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Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-2010 6 May – 20 May 2010 Kalpana M. Kanal, Ph.D. 1 Mammography Mammography - - Chapter 8 Chapter 8 Kalpana Kanal, Ph.D., DABR Kalpana Kanal, Ph.D., DABR Assistant Professor, Diagnostic Physics Assistant Professor, Diagnostic Physics Dept. of Radiology Dept. of Radiology UW Medicine UW Medicine a copy of this lecture may be found at: a copy of this lecture may be found at: http://courses.washington.edu/radxphys/PhysicsCourse.html http://courses.washington.edu/radxphys/PhysicsCourse.html 2 2 Kanal Kanal 1. Introduction 1. Introduction Mammography is a radiographic modality used for detecting breas Mammography is a radiographic modality used for detecting breas t t pathology and cancer pathology and cancer Approximately 1 in 8 women will develop breast cancer over a Approximately 1 in 8 women will develop breast cancer over a lifetime in USA lifetime in USA Breast cancer accounts for 32% of cancer incidence and 18% of Breast cancer accounts for 32% of cancer incidence and 18% of cancer deaths in women in the United States cancer deaths in women in the United States Breast cancer screening Breast cancer screening - - depend on x depend on x - - ray mammography because ray mammography because it is a low it is a low - - cost, low cost, low - - radiation radiation - - dose procedure that has the sensitivity dose procedure that has the sensitivity for early detection and improved treatment for early detection and improved treatment In 1992, the federal Mammography Quality Standards Act (MQSA) In 1992, the federal Mammography Quality Standards Act (MQSA) came into existence to ensure that all women have access to qual came into existence to ensure that all women have access to qual ity ity mammography with optimal patient care and follow mammography with optimal patient care and follow - - up up 3 3 Kanal Kanal RSN RSNA/AAPM Web Module Curriculum Fundamental Knowledge: Fundamental Knowledge: 1. Describe unique features of mammography tubes and how they af 1. Describe unique features of mammography tubes and how they af fect the x fect the x - - ray spectrum produced. ray spectrum produced. 2. Describe automatic exposure control (AEC) performance. Explai 2. Describe automatic exposure control (AEC) performance. Explai n n compression benefits. compression benefits. 3. Review magnification techniques. 3. Review magnification techniques. 4. Describe the characteristics of the different detectors used 4. Describe the characteristics of the different detectors used in mammography, in mammography, e.g. screen e.g. screen - - film and full film and full - - field digital mammography systems. field digital mammography systems. 5. Discuss breast radiation dosimetry. 5. Discuss breast radiation dosimetry. 6. Discuss MQSA (Mammography Quality Standards Act) and its effe 6. Discuss MQSA (Mammography Quality Standards Act) and its effe ct on ct on mammography image quality and dose. mammography image quality and dose. 4 4 Kanal Kanal RSN RSNA/AAPM Web Module Curriculum Clinical Application: Clinical Application: 1. Describe appropriate uses of the different targets and filter 1. Describe appropriate uses of the different targets and filter s available in s available in mammography systems. mammography systems. 2. Explain when magnification is indicated. 2. Explain when magnification is indicated. 3. Associate image quality changes with radiation dose changes. 3. Associate image quality changes with radiation dose changes. 4. What are the MQSA training and CME requirements for radiologi 4. What are the MQSA training and CME requirements for radiologi sts, technologists and sts, technologists and physicists? physicists? 5. What are the QA requirements of MQSA for digital mammography? 5. What are the QA requirements of MQSA for digital mammography? Clinical Problem Clinical Problem - - Solving: Solving: 1. Identify factors influencing image contrast and detail as the 1. Identify factors influencing image contrast and detail as the y relate to the visualization y relate to the visualization of lesions in mammography. of lesions in mammography. 2. Discuss possible image artifacts in mammography and correctiv 2. Discuss possible image artifacts in mammography and correctiv e methods that could e methods that could be used to reduce them. be used to reduce them.

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  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

    Kalpana M. Kanal, Ph.D. 1

    Mammography Mammography -- Chapter 8Chapter 8

    Kalpana Kanal, Ph.D., DABRKalpana Kanal, Ph.D., DABRAssistant Professor, Diagnostic PhysicsAssistant Professor, Diagnostic Physics

    Dept. of RadiologyDept. of RadiologyUW MedicineUW Medicine

    a copy of this lecture may be found at:a copy of this lecture may be found at:http://courses.washington.edu/radxphys/PhysicsCourse.htmlhttp://courses.washington.edu/radxphys/PhysicsCourse.html

    22KanalKanal

    1. Introduction1. Introduction

    Mammography is a radiographic modality used for detecting breasMammography is a radiographic modality used for detecting breast t pathology and cancerpathology and cancerApproximately 1 in 8 women will develop breast cancer over a Approximately 1 in 8 women will develop breast cancer over a lifetime in USAlifetime in USABreast cancer accounts for 32% of cancer incidence and 18% of Breast cancer accounts for 32% of cancer incidence and 18% of cancer deaths in women in the United Statescancer deaths in women in the United StatesBreast cancer screening Breast cancer screening -- depend on xdepend on x--ray mammography because ray mammography because it is a lowit is a low--cost, lowcost, low--radiationradiation--dose procedure that has the sensitivity dose procedure that has the sensitivity for early detection and improved treatmentfor early detection and improved treatmentIn 1992, the federal Mammography Quality Standards Act (MQSA) In 1992, the federal Mammography Quality Standards Act (MQSA) came into existence to ensure that all women have access to qualcame into existence to ensure that all women have access to quality ity mammography with optimal patient care and followmammography with optimal patient care and follow--upup

    33KanalKanal

    RSNRSNA/AAPM Web ModuleCurriculum

    Fundamental Knowledge: Fundamental Knowledge:

    1. Describe unique features of mammography tubes and how they af1. Describe unique features of mammography tubes and how they affect the xfect the x--ray spectrum produced. ray spectrum produced.

    2. Describe automatic exposure control (AEC) performance. Explai2. Describe automatic exposure control (AEC) performance. Explain n compression benefits. compression benefits.

    3. Review magnification techniques. 3. Review magnification techniques.

    4. Describe the characteristics of the different detectors used 4. Describe the characteristics of the different detectors used in mammography, in mammography, e.g. screene.g. screen--film and fullfilm and full--field digital mammography systems. field digital mammography systems.

    5. Discuss breast radiation dosimetry. 5. Discuss breast radiation dosimetry.

    6. Discuss MQSA (Mammography Quality Standards Act) and its effe6. Discuss MQSA (Mammography Quality Standards Act) and its effect on ct on mammography image quality and dose. mammography image quality and dose.

    44KanalKanal

    RSNRSNA/AAPM Web ModuleCurriculum

    Clinical Application: Clinical Application:

    1. Describe appropriate uses of the different targets and filter1. Describe appropriate uses of the different targets and filters available in s available in mammography systems. mammography systems.

    2. Explain when magnification is indicated. 2. Explain when magnification is indicated.

    3. Associate image quality changes with radiation dose changes. 3. Associate image quality changes with radiation dose changes.

    4. What are the MQSA training and CME requirements for radiologi4. What are the MQSA training and CME requirements for radiologists, technologists and sts, technologists and physicists? physicists?

    5. What are the QA requirements of MQSA for digital mammography?5. What are the QA requirements of MQSA for digital mammography?

    Clinical ProblemClinical Problem--Solving: Solving:

    1. Identify factors influencing image contrast and detail as the1. Identify factors influencing image contrast and detail as they relate to the visualization y relate to the visualization of lesions in mammography. of lesions in mammography.

    2. Discuss possible image artifacts in mammography and correctiv2. Discuss possible image artifacts in mammography and corrective methods that could e methods that could be used to reduce them. be used to reduce them.

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

    Kalpana M. Kanal, Ph.D. 2

    55KanalKanal

    1. Introduction1. IntroductionContinuing refinements in technology have vastly improved mammogContinuing refinements in technology have vastly improved mammography raphy over the last 15 yearsover the last 15 years

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 192.ed., p. 192.

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography

    Digital al MammographyMammography

    Tomosynthesis

    66KanalKanal

    1. Introduction1. Introduction

    Mass withMass withSpiculatedSpiculated

    marginsmargins

    Clustered Clustered heterogeneous heterogeneous

    microcalcificationsmicrocalcificationsArchitectural Architectural

    distortiondistortion

    c.f. Pictorial Essay : Mammographic Features of Breast Cancer, Mc.f. Pictorial Essay : Mammographic Features of Breast Cancer, MB Popli, Ind J B Popli, Ind J Radiol Imag 2001 11:4:175Radiol Imag 2001 11:4:175--179179

    Mammographic features characteristic of breast cancer are:Mammographic features characteristic of breast cancer are:

    77KanalKanal

    1. Introduction1. Introduction

    Screening Mammography Screening Mammography –– Identify Identify CancerCancerthe AMA, ACS and ACR recommend the AMA, ACS and ACR recommend a baseline mammogram by age 40, a baseline mammogram by age 40, biannual examinations between ages biannual examinations between ages 40 and 50, and yearly examinations 40 and 50, and yearly examinations after age 50after age 50NCI recommends women in their 40s, NCI recommends women in their 40s, 50s and older should be screened 50s and older should be screened every one to two years with every one to two years with mammographymammographyRequire craniocaudal (CC) and Require craniocaudal (CC) and mediolateral oblique (MLO) views of mediolateral oblique (MLO) views of each breasteach breast

    CCCC MLOMLO

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    1. Introduction1. Introduction

    Diagnostic Mammography Diagnostic Mammography ––Evaluate AbnormalitiesEvaluate Abnormalities

    may require additional may require additional views, magnification views, views, magnification views, spot compression views, spot compression views, stereotactic biopsy or other stereotactic biopsy or other studies using other studies using other modalitiesmodalities

    c.f. Radiographics 19 (2): 280c.f. Radiographics 19 (2): 280

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    1. Mammography Imaging Modalities1. Mammography Imaging Modalities

    Ultrasound Breast ImagingUltrasound Breast Imagingused for differentiating cysts (typically benign) from solid used for differentiating cysts (typically benign) from solid masses (often cancerous), which have similar appearances masses (often cancerous), which have similar appearances on the mammogramon the mammogramprovides biopsy needle guidance for extracting breast tissue provides biopsy needle guidance for extracting breast tissue specimensspecimens

    MRIMRIhas wonderful tissue contrast sensitivityhas wonderful tissue contrast sensitivityuseful for evaluating silicone implantsuseful for evaluating silicone implantsaccurately assess the stage of breast cancer involvementaccurately assess the stage of breast cancer involvement

    UW UW -- Dr. Constance Dr. Constance LehmanLehman

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    1. Modern Mammography1. Modern Mammography

    Breast is composed of fatty tissue, glandular tissue and a 50/50Breast is composed of fatty tissue, glandular tissue and a 50/50combination of both combination of both Normal and cancerous tissues in the breast have small xNormal and cancerous tissues in the breast have small x--ray ray attenuation differences between them and this difference decreasattenuation differences between them and this difference decreases es with increasing energywith increasing energyNeed xNeed x--ray equipment specifically designed to optimize breast ray equipment specifically designed to optimize breast cancer detectioncancer detection

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 193.ed., p. 193.

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography

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    1. Modern Mammography1. Modern Mammography

    Detection of minute calcifications important Detection of minute calcifications important high correlation of calcification patterns with diseasehigh correlation of calcification patterns with disease

    Best differential between the tissues is obtained at low xBest differential between the tissues is obtained at low x--ray ray energiesenergies

    However, the high absorption results in a high tissue dose and However, the high absorption results in a high tissue dose and long exposure timelong exposure time

    Mammography equipmentMammography equipmentLow contrast sensitivityLow contrast sensitivityhigh resolution high resolution low doselow dose

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography 1212KanalKanal

    1. Modern Mammography1. Modern Mammography

    Dedicated Mammography EquipmentDedicated Mammography EquipmentSpecialized XSpecialized X--ray Tubesray TubesBreast Compression DevicesBreast Compression DevicesOptimized Screen/Film detector Optimized Screen/Film detector systemssystems

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 194.ed., p. 194.c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and

    Dose in MammographyDose in Mammography

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    1. X1. X--Ray Tube DesignRay Tube Design

    0.3 mm (contact) and 0.1 mm (magnification) focal spot sizes0.3 mm (contact) and 0.1 mm (magnification) focal spot sizesSmall focal spot minimizes geometric blurring and maintains Small focal spot minimizes geometric blurring and maintains spatial resolution spatial resolution Peak Kilovolt below 35 kVp Peak Kilovolt below 35 kVp 100 mA for large (0.3 mm) focal spot100 mA for large (0.3 mm) focal spot25 mA for small focal spot 25 mA for small focal spot

    Anodes: Molybdenum (Mo), and dual track Mo/Rhodium Anodes: Molybdenum (Mo), and dual track Mo/Rhodium (Mo/Rh) targets are used(Mo/Rh) targets are usedTargets used in combination with specific tube filters to achievTargets used in combination with specific tube filters to achieve e optimal energy spectraoptimal energy spectra

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    1. X1. X--Ray Tube DesignRay Tube Design

    Heel effect Heel effect –– significant drop in xsignificant drop in x--ray intensity on the anode side ray intensity on the anode side of the field (selfof the field (self--filtration through anode)filtration through anode)Thus cathodeThus cathode--anode axis is placed from the chest wall (greater anode axis is placed from the chest wall (greater penetration of xpenetration of x--rays) to the nipple in breast imagingrays) to the nipple in breast imagingMore uniform exposure is achievedMore uniform exposure is achievedAlso minimizes equipment bulk near the patientAlso minimizes equipment bulk near the patient’’s head for easy s head for easy positioningpositioning

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 196.ed., p. 196.

    Self-filtration

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    Monoenergetic xMonoenergetic x--rays of 15 to 25 keV are optimal choice to achieve rays of 15 to 25 keV are optimal choice to achieve high subject contrast at lowest possible radiation dosehigh subject contrast at lowest possible radiation dose

    Polychromatic spectra compromises:Polychromatic spectra compromises:HighHigh--energy xenergy x--rays in the bremsstrahlung spectrum diminish rays in the bremsstrahlung spectrum diminish subject contrastsubject contrastLowLow--energy xenergy x--rays in the bremsstralung spectrum have inadequate rays in the bremsstralung spectrum have inadequate penetration and contribute to patient dose without providing a penetration and contribute to patient dose without providing a useful imageuseful image

    Optimal xOptimal x--ray energy is achieved by use of specific target materials ray energy is achieved by use of specific target materials and filters to remove the lowand filters to remove the low-- and highand high--energy xenergy x--raysrays

    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

    1616KanalKanal

    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

    Molybdenum (Mo)Molybdenum (Mo) and and Rhodium (Rh)Rhodium (Rh) are used for mammography are used for mammography targets and produce characteristic xtargets and produce characteristic x--ray peaks at 17.5 and 19.6 keV ray peaks at 17.5 and 19.6 keV (Mo) and 20.2 and 22.7 keV (Rh)(Mo) and 20.2 and 22.7 keV (Rh)

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    11--mm thick Beryllium used as the tube portmm thick Beryllium used as the tube portBeryllium provides both low attenuation and good structural Beryllium provides both low attenuation and good structural integrityintegrity

    Added tube filters of the Added tube filters of the samesame element as the target reduce the element as the target reduce the lowlow-- and highand high--energy xenergy x--rays in the xrays in the x--ray spectrum and allow ray spectrum and allow transmission of characteristic xtransmission of characteristic x--ray energiesray energies

    Common target/filters in mammography include Common target/filters in mammography include Mo/MoMo/MoRh/RhRh/RhMo/RhMo/Rh

    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

    1818KanalKanal

    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

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    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

    A Mo target with Rh filter is A Mo target with Rh filter is used for imaging thicker used for imaging thicker and denser breasts since and denser breasts since this produces slightly this produces slightly higher effective energy than higher effective energy than Mo/MoMo/Mo

    20 20 -- 23 keV effective 23 keV effective energy leading to increased energy leading to increased penetration of thick and/or penetration of thick and/or dense breastsdense breasts

    2020KanalKanal c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 201.ed., p. 201.

    1. Tube Port, Tube Filtration & Beam Quality1. Tube Port, Tube Filtration & Beam Quality

    Rh target with Rh filter provides the highest effective energy Rh target with Rh filter provides the highest effective energy beam beam and is useful for the thickest and densest breastsand is useful for the thickest and densest breastsTungsten (W) targets with Mo and Rh filters not usually used butTungsten (W) targets with Mo and Rh filters not usually used butsometimes are available with the mammography unitsometimes are available with the mammography unit

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    1. Half Value Layer (HVL)1. Half Value Layer (HVL)

    The HVL ranges from 0.3 to 0.45 mm Al in mammographyThe HVL ranges from 0.3 to 0.45 mm Al in mammographydepends on kVp, compression paddle thickness, added tube depends on kVp, compression paddle thickness, added tube filtration, target material and age of tubefiltration, target material and age of tubeIn general, HVL increases with higher kVp and higher atomic In general, HVL increases with higher kVp and higher atomic number targets and filtersnumber targets and filters

    The approximate HVL in breast tissue is The approximate HVL in breast tissue is ~~ 1 to 2 cm (strongly 1 to 2 cm (strongly dependent on tissue composition: glandular, adipose and dependent on tissue composition: glandular, adipose and fibrous).fibrous).

    Thus a 4cm breast will attenuate 1Thus a 4cm breast will attenuate 1--1/21/244 ≈≈ 0.93, or 93% of the 0.93, or 93% of the incident primary radiation incident primary radiation

    [reduction in beam intensity or fraction [reduction in beam intensity or fraction transmitted is 1/2transmitted is 1/2nnand and attenuation is (1attenuation is (1--1/21/2nn)])]

    2222KanalKanal

    1. Collimation1. Collimation

    FixedFixed--size metal apertures or variable field size shutters size metal apertures or variable field size shutters collimate the xcollimate the x--ray beamray beamThe field size matches the film cassette sizes The field size matches the film cassette sizes

    18 x 24 cm or 24 x 30 cm18 x 24 cm or 24 x 30 cm

    Collimator light and mirror assembly define the xCollimator light and mirror assembly define the x--ray fieldray fieldXX--ray field ray field –– light field congruence must be within 2% of SID light field congruence must be within 2% of SID for any edgefor any edgeThe useful xThe useful x--ray field must extend to the chest wall edge ray field must extend to the chest wall edge without field cutoffwithout field cutoff

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    2. X2. X--Ray Generator Ray Generator

    A dedicated mammography xA dedicated mammography x--ray generator is similar to a ray generator is similar to a standard xstandard x--ray generator in design and function with some minor ray generator in design and function with some minor differences. differences.

    Generator power rating is 3Generator power rating is 3--10 kW10 kWThe voltage supplied to the xThe voltage supplied to the x--ray tube (22ray tube (22--40 kVp),40 kVp),Automatic Exposure Control (AEC) circuitry differentAutomatic Exposure Control (AEC) circuitry different

    HighHigh--frequency generators are the standard for mammography frequency generators are the standard for mammography

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    2. Automatic Exposure Control (AEC)2. Automatic Exposure Control (AEC)The AEC, also called a phototimer, uses a radiation sensor (or The AEC, also called a phototimer, uses a radiation sensor (or sensors), an amplifier, a voltage comparator, to control the expsensors), an amplifier, a voltage comparator, to control the exposureosure

    AEC detector is located AEC detector is located underneathunderneath the cassette in mammography the cassette in mammography unlike conventional radiographyunlike conventional radiography

    c.f. Bushberg, c.f. Bushberg, et al. The et al. The Essential Essential Physics of Physics of Medical Medical Imaging, 2Imaging, 2ndnded., p. 205.ed., p. 205.

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    If the transmission of photons is insufficient to turn the exposIf the transmission of photons is insufficient to turn the exposure ure off after an extended exposure time, a off after an extended exposure time, a backup backup timer terminates timer terminates the exposurethe exposure

    For a retake, the operator must select a higher kVp for For a retake, the operator must select a higher kVp for greater beam penetrability and shorter exposure timegreater beam penetrability and shorter exposure time

    Inaccurate phototimer response can be caused byInaccurate phototimer response can be caused byBreast tissue composition heterogeneity, defective cassette, Breast tissue composition heterogeneity, defective cassette, faulty detector, inappropriate kVp setting etc.faulty detector, inappropriate kVp setting etc.

    Film response to very long exposure times (MAG mode) results Film response to very long exposure times (MAG mode) results in in reciprocity law failurereciprocity law failure and inadequate film densityand inadequate film density

    2. Automatic Exposure Control (AEC)2. Automatic Exposure Control (AEC)

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    2. Technique Chart2. Technique Chart

    Technique charts are useful guides to determine the appropriate Technique charts are useful guides to determine the appropriate kVp for specific imaging tasks, based on breast thickness and brkVp for specific imaging tasks, based on breast thickness and breast east compositioncomposition

    posted near the consoleposted near the console

    Proper kVp is essential for a reasonable exposure time, defined Proper kVp is essential for a reasonable exposure time, defined as a as a range from approx. 0.5 to 2.0 seconds, to achieve an optical denrange from approx. 0.5 to 2.0 seconds, to achieve an optical density sity of 1.5 to 2.0of 1.5 to 2.0

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    3. Compression3. CompressionBreast compression is necessary Breast compression is necessary

    it reduces overlapping anatomy and decreases tissue thickness it reduces overlapping anatomy and decreases tissue thickness of the breastof the breastless scatter, more contrast, less geometric blurring of the less scatter, more contrast, less geometric blurring of the anatomic structures, less motion and lower radiation dose to theanatomic structures, less motion and lower radiation dose to thetissuestissues

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 208.ed., p. 208.c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and

    Dose in MammographyDose in Mammography 2828KanalKanal

    3. Compression3. Compression

    Use a low attenuating lexan paddle attached to a compression Use a low attenuating lexan paddle attached to a compression devicedevice10 to 20 newtons (22 to 44 pounds) of force is typically used10 to 20 newtons (22 to 44 pounds) of force is typically usedA flat, 90A flat, 90°°paddle (not curved) provides a uniform density imagepaddle (not curved) provides a uniform density imageParallel to the breast support tableParallel to the breast support tablePrincipal drawback of compression is patient discomfortPrincipal drawback of compression is patient discomfort

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 208.ed., p. 208.

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    3. Compression3. Compression

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 208.ed., p. 208.

    Spot compression uses small paddlesSpot compression uses small paddles

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    3. Scatter Radiation 3. Scatter Radiation

    Scatter radiation degrades Scatter radiation degrades subject contrastsubject contrastThe amount of scatter The amount of scatter increases with breast increases with breast thickness and breast area, thickness and breast area, and is relatively constant and is relatively constant with kVp (25with kVp (25--35 kVp)35 kVp)Without scatter rejection, Without scatter rejection, only 50 to 70% of the only 50 to 70% of the inherent subject contrast will inherent subject contrast will be detectedbe detected

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 209.ed., p. 209.

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    3. Scatter Radiation 3. Scatter Radiation Linear grids with a grid ratio of 4:1 to 5:1 are typicalLinear grids with a grid ratio of 4:1 to 5:1 are typicalAluminum and carbon fiber are typical interspace materialsAluminum and carbon fiber are typical interspace materials

    Carbon fiber is preferred Carbon fiber is preferred –– lower attenuationlower attenuationGrid frequencies (lead strip densities) range from 30 to 50 lineGrid frequencies (lead strip densities) range from 30 to 50 lines/cm s/cm for moving grids and up to 80 lines/cm for stationary gridsfor moving grids and up to 80 lines/cm for stationary gridsBucky factor (with grid/without grid) is about 2 to 3, so breastBucky factor (with grid/without grid) is about 2 to 3, so breast dose is dose is doubled or tripled, but image contrast improves by 40%doubled or tripled, but image contrast improves by 40%Grids not used in magnification, air gap usedGrids not used in magnification, air gap used

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 209.ed., p. 209.

    c.f. RSNA/AAPM web module: c.f. RSNA/AAPM web module: Image Quality and Dose in Image Quality and Dose in MammographyMammography

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    3. Magnification3. MagnificationAdvantagesAdvantages

    Magnification of 1.5x to 2.0x is Magnification of 1.5x to 2.0x is usedusedIncreased effective resolution of Increased effective resolution of the image receptor by the the image receptor by the magnification factormagnification factorSmall focal spot size usedSmall focal spot size usedReduction of scatterReduction of scatter

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 211.ed., p. 211.

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography

  • Mammography – Chapter 8 Diagnostic Radiology Imaging Physics Course 2009-20106 May – 20 May 2010

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    3. Magnification3. Magnification

    DisadvantagesDisadvantagesGeometric blurring caused Geometric blurring caused by the finite focal spot size by the finite focal spot size (more on cathode side)(more on cathode side)Breast dose in general Breast dose in general similar to contact similar to contact mammographymammographyLong exposure times (small Long exposure times (small focal spot, low mA)focal spot, low mA)

    patient motion and blurpatient motion and blur

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 211.ed., p. 211. 3434KanalKanal

    3. MTF in magnification mammography3. MTF in magnification mammography

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 211.ed., p. 211.

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    Take Home PointsTake Home Points

    Breast Cancer Breast Cancer –– masses, microcalcifications and architectural masses, microcalcifications and architectural distortions in breastdistortions in breastLow energies used to optimize contrast (photoelectric effect)Low energies used to optimize contrast (photoelectric effect)Specialized equipment neededSpecialized equipment needed

    Improve contrast and resolution, decrease doseImprove contrast and resolution, decrease dosekVp range 22kVp range 22-- 40 kVp40 kVpMolybdenum and Rhodium targets used in mammographyMolybdenum and Rhodium targets used in mammography

    Characteristic radiation for Mo at 17.5 and 19.6 keVCharacteristic radiation for Mo at 17.5 and 19.6 keVFor rhodium, 20.2 and 22.7 keVFor rhodium, 20.2 and 22.7 keV

    Heel effect due to attenuation in targetHeel effect due to attenuation in targetChest wall on cathode side and nipple on anode side to get Chest wall on cathode side and nipple on anode side to get uniform exposureuniform exposure

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    Take Home PointsTake Home Points

    Common target/filters in mammography include Common target/filters in mammography include Mo/Mo (thin breasts), Rh/Rh (thickest, dense breasts), Mo/Rh Mo/Mo (thin breasts), Rh/Rh (thickest, dense breasts), Mo/Rh (thicker, denser breasts)(thicker, denser breasts)Tungsten target available on some units but not usedTungsten target available on some units but not used

    Generator similar to conventional radiography except forGenerator similar to conventional radiography except forlower power rating, different AEC circuitry, low kVp usedlower power rating, different AEC circuitry, low kVp used

    18 x 24 and 24 x 30 cm cassettes used18 x 24 and 24 x 30 cm cassettes usedAEC detector is located AEC detector is located underneathunderneath the cassette in mammography the cassette in mammography unlike conventional radiographyunlike conventional radiography

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    Take Home PointsTake Home Points

    Breast compression is necessary Breast compression is necessary reduces overlapping anatomy, decreases tissue thickness of the reduces overlapping anatomy, decreases tissue thickness of the breast, less scatter, more contrast, less motion and lower breast, less scatter, more contrast, less motion and lower radiation dose to the tissuesradiation dose to the tissues

    Scatter reduced by gridsScatter reduced by grids5:1 grid ratio5:1 grid ratioBucky factor of 2 to 3Bucky factor of 2 to 3

    Magnification of 1.5 to 2 times in mammographyMagnification of 1.5 to 2 times in mammographyIncreased resolution, decreased scatter, increased dose, long Increased resolution, decreased scatter, increased dose, long exposure times, motion, increase in geometric blur with exposure times, motion, increase in geometric blur with increased magnificationincreased magnification

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    4. Screen/Film Cassettes 4. Screen/Film Cassettes

    Cassettes have a single phosphor Cassettes have a single phosphor screen and single emulsion filmscreen and single emulsion film

    Mammography screenMammography screen--film speeds film speeds (sensitivity):(sensitivity):

    regular (100 or par speed) (12regular (100 or par speed) (12--15 mR required)15 mR required)medium (150 medium (150 –– 190 speed)190 speed)

    For comparison, a conventional For comparison, a conventional ““100100--speedspeed”” screen film cassette screen film cassette requires about 2 mRrequires about 2 mR

    3939KanalKanalc.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical

    Imaging, 2Imaging, 2ndnd ed., p. 214.ed., p. 214.

    Limiting spatial Limiting spatial resolution is =resolution is =1515--20 lp/mm 20 lp/mm (0.025 (0.025 -- 0.030 0.030 mm object size)mm object size)

    4. Screen/Film Cassettes 4. Screen/Film Cassettes

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    4. Film Processing4. Film Processing

    Film processing is a critical step in the mammographic imaging Film processing is a critical step in the mammographic imaging chainchain

    Consistency in film speed, contrast, optical density levels are Consistency in film speed, contrast, optical density levels are readily readily achieved by following the manufacturerachieved by following the manufacturer’’s recommendationss recommendations

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    4. Film Sensitometry4. Film Sensitometry

    A film processor quality control program is required by A film processor quality control program is required by Mammography Quality Standards Act of 1992 (MQSA) regulations, Mammography Quality Standards Act of 1992 (MQSA) regulations, and daily sensitometric strips and daily sensitometric strips prior to the first clinical imagesprior to the first clinical images must must verify acceptable performanceverify acceptable performance

    Film sensitometry confirms proper film contrast, speed and base Film sensitometry confirms proper film contrast, speed and base + + fog values of mammographic filmfog values of mammographic film

    Typical fog values are 0.17 Typical fog values are 0.17 –– 0.2 OD, Dmax = 3.8 0.2 OD, Dmax = 3.8 –– 4.0 OD and 4.0 OD and the target film OD ranges from 1.2 the target film OD ranges from 1.2 –– 1.81.8

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    4. Film Sensitometry4. Film Sensitometry

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 216.ed., p. 216.

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    4. Film Sensitometry4. Film Sensitometry

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 216.ed., p. 216.

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    4. Extended Cycle Processing4. Extended Cycle Processing

    Extended cycle processing (or push processing) increases the Extended cycle processing (or push processing) increases the speed of some single emulsion mammography films by speed of some single emulsion mammography films by extending the developer immersion time by a factor of two extending the developer immersion time by a factor of two (usually from (usually from ~~ 20 to 20 to ~~ 40 seconds)40 seconds)The rationale is to completely develop all latent image centers,The rationale is to completely develop all latent image centers,which does not occur with standard processingwhich does not occur with standard processing

    Up to 35% to 40% decrease in required xUp to 35% to 40% decrease in required x--ray exposure is ray exposure is obtained compared to standard processing for same ODobtained compared to standard processing for same ODOn conventional 90 second processor, the processing time is On conventional 90 second processor, the processing time is extended to 180 secondsextended to 180 seconds

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    4. Extended Cycle Processing4. Extended Cycle Processing

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 218.ed., p. 218.

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    4. Film Viewing Conditions4. Film Viewing Conditions

    Optimal film viewing conditions are important in detecting subtlOptimal film viewing conditions are important in detecting subtle e lesionslesionsMammography films are exposed to high optical densities to Mammography films are exposed to high optical densities to achieve high contrast, view boxes providing a high luminance areachieve high contrast, view boxes providing a high luminance arenecessarynecessary

    The luminance of a mammography viewbox should be at least The luminance of a mammography viewbox should be at least 3000 cd/m3000 cd/m22In comparison, a typical viewbox in diagnostic radiology is abouIn comparison, a typical viewbox in diagnostic radiology is about t 1500 cd/m1500 cd/m22

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    4. Film Viewing Conditions4. Film Viewing Conditions

    Film masking is essential for blocking clear portions of the filFilm masking is essential for blocking clear portions of the film m and the viewboxand the viewbox

    The ambient light intensity in a mammography reading room The ambient light intensity in a mammography reading room should be low to eliminate reflections from the filmshould be low to eliminate reflections from the film

    A high intensity bright light to penetrate high optical density A high intensity bright light to penetrate high optical density regions of the film, such as skin line and the nipple arearegions of the film, such as skin line and the nipple area

    Magnifying glass should be available to view fine detail such asMagnifying glass should be available to view fine detail such asmicrocalcificationsmicrocalcifications

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    1. 1. Which of the following is Which of the following is notnot a modern mammography target/filter a modern mammography target/filter combination for screencombination for screen--film?film?

    A. Mo/MoA. Mo/MoB. Mo/B. Mo/RhRhC. C. Rh/RhRh/RhD. W/AlD. W/AlE. W/E. W/RhRh

    Question Question

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    Rhodium/rhodium target/filter combinations should be used only wRhodium/rhodium target/filter combinations should be used only when:hen:Thick, dense breasts are imaged.Thick, dense breasts are imaged.Thin, adipose breasts are imaged.Thin, adipose breasts are imaged.Maximum subject contrast is critical.Maximum subject contrast is critical.The molybdenum anode is too hot.The molybdenum anode is too hot.High resolution images are necessary.High resolution images are necessary.

    Question Question

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    The use of a 5:1 mammography grid _____ the breast dose by The use of a 5:1 mammography grid _____ the breast dose by _____ _____ time(stime(s) that without a grid.) that without a grid.

    Decreases, 1.0Decreases, 1.0Increases, 1.0Increases, 1.0Decreases, 2.5Decreases, 2.5Increases, 2.5Increases, 2.5Increases, 5Increases, 5

    Question Question

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    Compensation for the heel effect occurs when:Compensation for the heel effect occurs when:Orientation of the cathode/anode axis perpendicular to the chestOrientation of the cathode/anode axis perpendicular to the chestwall/nipple.wall/nipple.Extended processor development time.Extended processor development time.Orientation of the cathode over the chest wall and anode over Orientation of the cathode over the chest wall and anode over the nipple.the nipple.Larger field of view (24 * 30 cm) cassettes.Larger field of view (24 * 30 cm) cassettes.Orientation of the cathode over the nipple and the anode over Orientation of the cathode over the nipple and the anode over the chest wall.the chest wall.

    Question Question

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    QuestionQuestion

    1.1. The KThe K--characteristic xcharacteristic x--rays of molybdenum target tubes comprise rays of molybdenum target tubes comprise a significant portion of the total xa significant portion of the total x--ray flux. These xray flux. These x--rays have rays have energies predominantly between _________ energies predominantly between _________ keVkeV and _________ and _________ keVkeV

    A. A. 10, 10, 1212B. B. 15, 15, 1616C. C. 17, 17, 2020D. D. 24, 24, 2626E. E. 59, 59, 6969

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    QuestionQuestion

    1.1. The filtration in mammography units primarily transmits the The filtration in mammography units primarily transmits the characteristic xcharacteristic x--rays. The very lowrays. The very low--energy energy bremsstrahlungbremsstrahlung xx--rays rays are filtered because they contribute to ___________, and the higare filtered because they contribute to ___________, and the higher her energy energy bremsstrahlungbremsstrahlung xx--rays are filtered because they contribute to rays are filtered because they contribute to _______________._______________.

    A. tube heating, offA. tube heating, off--focus radiationfocus radiationB. heel effect, focal spot bloomingB. heel effect, focal spot bloomingC. radiation dose, loss of contrastC. radiation dose, loss of contrastD. grid cutD. grid cut--off, off, septalseptal penetrationpenetrationE. coherent scatter, KE. coherent scatter, K--edge photonsedge photons

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    QuestionQuestion

    11. The low voltage used in screen/film mammography reduces:. The low voltage used in screen/film mammography reduces:

    (A) Subject contrast(A) Subject contrast(B) Dose(B) Dose(C) (C) MicrocalcificationMicrocalcification visibilityvisibility(D) Scatter(D) Scatter(E) Film processing time(E) Film processing time

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    5. Radiation Dosimetry5. Radiation Dosimetry

    Risk of carcinogenesis from the radiation dose to the breast is Risk of carcinogenesis from the radiation dose to the breast is of of concern thus monitoring of dose is important and is required yeaconcern thus monitoring of dose is important and is required yearly rly by MQSA (Mammography Quality Standards Act of 1992)by MQSA (Mammography Quality Standards Act of 1992)

    Indices used in MammographyIndices used in MammographyEntrance Skin Exposure (ESE)Entrance Skin Exposure (ESE)

    the freethe free--inin--air ionization chamber measurement of the air ionization chamber measurement of the entrance skin exposure of the breastentrance skin exposure of the breasttypical ESE values for a 4.5 cm breast are 500 to 1000 mRtypical ESE values for a 4.5 cm breast are 500 to 1000 mR

    Half Value Layer (HVL)Half Value Layer (HVL)Typical HVL from 0.3 to 0.4 mm Al for 25 Typical HVL from 0.3 to 0.4 mm Al for 25 –– 30 kVp30 kVp

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    Glandular tissue is sensitive to cancer induction by radiationGlandular tissue is sensitive to cancer induction by radiation

    Average Glandular DoseAverage Glandular DoseDependent on the composition of breast, breast thickness, Dependent on the composition of breast, breast thickness, HVL and kVp of beamHVL and kVp of beamThe Roentgen to Rad conversion factor, DThe Roentgen to Rad conversion factor, DggN is used to N is used to convert the measured ESE to glandular doseconvert the measured ESE to glandular dose

    DDgg = D= DggN x XN x XESEESE

    5. Radiation Dosimetry5. Radiation Dosimetry

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography

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    5. Radiation Dosimetry5. Radiation Dosimetry

    Factors affecting breast doseFactors affecting breast doseHigher kVp increases beam penetrability (lower ESE and lower Higher kVp increases beam penetrability (lower ESE and lower average glandular dose), but decreases inherent subject average glandular dose), but decreases inherent subject contrastcontrast↑↑ kVp and kVp and ↓↓ mAs will result in low dose because of greater mAs will result in low dose because of greater penetrability (use higher kVp)penetrability (use higher kVp)

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 223.ed., p. 223.

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    5. Radiation Dosimetry5. Radiation Dosimetry

    Factors affecting breast doseFactors affecting breast doseIncreased breast thickness requires increased doseIncreased breast thickness requires increased doseVigorous compression lowers breast dose by reducing thicknessVigorous compression lowers breast dose by reducing thickness

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 224.ed., p. 224.

    c.f. RSNA/AAPM web module: Image Quality and c.f. RSNA/AAPM web module: Image Quality and Dose in MammographyDose in Mammography

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    5. Radiation Dosimetry5. Radiation Dosimetry

    Variables impacting breast doseVariables impacting breast doseRh/Rh combination will result in lowest average dose, Rh/Rh combination will result in lowest average dose, followed by Mo/Rh and Mo/Mo (use Rh for thicker, denser followed by Mo/Rh and Mo/Mo (use Rh for thicker, denser breasts)breasts)Screen/film speed and film processing conditions (use faster Screen/film speed and film processing conditions (use faster screen film or digital detectors)screen film or digital detectors)

    Higher OD target on film will Higher OD target on film will ↑↑ dosedoseUse of a grid will Use of a grid will ↑↑ dosedose

    Tissue composition of the breast Tissue composition of the breast Glandular tissue will have higher breast dose due to Glandular tissue will have higher breast dose due to increased attenuation and a greater mass of tissue at riskincreased attenuation and a greater mass of tissue at risk

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    The MQSA limits the average glandular breast dose to 3 mGy or The MQSA limits the average glandular breast dose to 3 mGy or 300 mrad per film for a compressed breast thickness of 4.2 cm an300 mrad per film for a compressed breast thickness of 4.2 cm and d a breast composition of 50% glandular and 50% adipose tissue a breast composition of 50% glandular and 50% adipose tissue (using the MQSA approved mammography phantom)(using the MQSA approved mammography phantom)

    If the average glandular dose for this phantom exceeds 3 mGy, If the average glandular dose for this phantom exceeds 3 mGy, mammography cannot be performedmammography cannot be performed

    The average glandular dose for this phantom is typically 1.5 to The average glandular dose for this phantom is typically 1.5 to 2.2 2.2 mGy per viewmGy per view or 3 to 4.4 mGy for two views for a film optical density or 3 to 4.4 mGy for two views for a film optical density of 1.5 to 2.0of 1.5 to 2.0

    5. Radiation Dosimetry5. Radiation Dosimetry

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    5. Risks and Benefits5. Risks and Benefits

    Based on AGD of 3 mGy, the increased breast cancer risk from Based on AGD of 3 mGy, the increased breast cancer risk from radiation is 6 per million examined womenradiation is 6 per million examined womenThis is equivalent to dying in an accident when traveling 5000 mThis is equivalent to dying in an accident when traveling 5000 miles iles by airplane or 450 miles by carby airplane or 450 miles by carScreening in 1 million women is expected to identify 3000 cases Screening in 1 million women is expected to identify 3000 cases of of breast cancerbreast cancerThe breast cancer mortality rate is about 50%The breast cancer mortality rate is about 50%Screening would reduce the mortality rate by about 40%Screening would reduce the mortality rate by about 40%That would potentially mean 600 lives being saved due to screeniThat would potentially mean 600 lives being saved due to screeningngThe benefits of getting a mammogram far outweigh the risks The benefits of getting a mammogram far outweigh the risks associated with the radiation due to the mammogramassociated with the radiation due to the mammogram

    c. Huda. Review of Radiologic Physics, 2c. Huda. Review of Radiologic Physics, 2ndnd ed., p. 112ed., p. 112--113.113.6262KanalKanal

    Take Home PointsTake Home Points

    SingleSingle--screen and single emulsion film usedscreen and single emulsion film used1515--20 lp/mm resolution20 lp/mm resolution

    Film processing is very importantFilm processing is very importantA film processor quality control program is required by A film processor quality control program is required by Mammography Quality Standards Act of 1992 (MQSA) regulationsMammography Quality Standards Act of 1992 (MQSA) regulationsThe luminance of a mammography viewbox should be at least 3000 The luminance of a mammography viewbox should be at least 3000 cd/mcd/m22

    Glandular tissue is sensitive to cancer induction by radiationGlandular tissue is sensitive to cancer induction by radiation

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    Take Home PointsTake Home Points

    Average glandular breast dose limited to 3 mGy or 300 mrad per fAverage glandular breast dose limited to 3 mGy or 300 mrad per film ilm for a compressed breast thickness of 4.2 cm, 50/50 for a compressed breast thickness of 4.2 cm, 50/50 glandular/adipose breast compositionglandular/adipose breast composition

    Increasing kVp reduces doseIncreasing kVp reduces doseIncreased breast size increases doseIncreased breast size increases doseVigorous compression lowers breast dose by reducing thicknessVigorous compression lowers breast dose by reducing thickness

    Risk of mammogram induced breast cancer is far less than the risRisk of mammogram induced breast cancer is far less than the risk k of developing breast cancerof developing breast cancer

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    6. Stereotactic Breast Biopsy6. Stereotactic Breast Biopsy

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 220, 305.ed., p. 220, 305.

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    6. Stereotactic Breast Biopsy6. Stereotactic Breast Biopsy

    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 220.ed., p. 220. 6666KanalKanal

    7. Full7. Full--Field Digital Mammography (FFDM)Field Digital Mammography (FFDM)

    c.f. www.gehealthcare.com/rad/xr/education/dig_xray_intro.htmlc.f. www.gehealthcare.com/rad/xr/education/dig_xray_intro.html

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    7. Full7. Full--Field Digital Mammography (FFDM)Field Digital Mammography (FFDM)

    AdvantageAdvantageWide dynamic range Wide dynamic range (1000:1) compared with (1000:1) compared with SFM (40:1)SFM (40:1)Dynamic image Dynamic image manipulationmanipulationAbility to postAbility to post--processprocessSoftSoft--copy read copy read accompanied by computeraccompanied by computer--aidedaided--diagnosis (CAD)diagnosis (CAD)3D imaging3D imaging

    Radiographics 2004:24,1749 6868KanalKanal

    7. Full7. Full--Field Digital Mammography (FFDM)Field Digital Mammography (FFDM)

    AdvantageAdvantageEach component of the mammographic process can be Each component of the mammographic process can be optimized with digital mammographyoptimized with digital mammography

    Radiographics 2004:24,1750

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    7. SFM vs. FFDM7. SFM vs. FFDM

    SFM: Half mAs, Automatic exposure control, Double mAs

    FFDM: Same technique factors as SFM, W/L adjusted

    Radiographics 2004:24,1750 7070KanalKanal

    7. SFM vs. FFDM7. SFM vs. FFDM

    Radiographics 2004:24,1751

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    7.Technologies for FFDM7.Technologies for FFDM

    Indirect CaptureIndirect Capturea scintillator such as cesium a scintillator such as cesium iodide (CsI) absorbs xiodide (CsI) absorbs x--rays rays and generates a light and generates a light scintillationscintillationdetected by an array of detected by an array of photodiodes or chargephotodiodes or charge--coupled devices (CCDs)coupled devices (CCDs)Resolution degradation Resolution degradation

    http://www.hologic.com/wh/pdf/R-LM-016_Radiology_Management.pdf 7272KanalKanal

    7. Technologies for FFDM7. Technologies for FFDM

    Direct CaptureDirect CaptureXX--ray photons are directly ray photons are directly captured by a captured by a photoconductor such as photoconductor such as amorphous selenium (aamorphous selenium (a--Se), which converts the Se), which converts the absorbed xabsorbed x--rays directly to a rays directly to a digital signaldigital signalSpatial resolution limited to Spatial resolution limited to pixel sizepixel size

    http://www.hologic.com/wh/pdf/R-LM-016_Radiology_Management.pdf

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    7. Technologies for FFDM 7. Technologies for FFDM –– Indirect CaptureIndirect Capture

    A narrow slotA narrow slot--detector and a detector and a narrow fan beam of xnarrow fan beam of x--rays are rays are scanned synchronously across scanned synchronously across the full field of view to cover the full field of view to cover the entire breastthe entire breastSystem consists of phosphor System consists of phosphor (thallium(thallium--activated CsI) with a activated CsI) with a fiberoptic coupling to a CCDfiberoptic coupling to a CCDDetector is 1 cm wide and 22 Detector is 1 cm wide and 22 cm long, consists of 4 CCDs cm long, consists of 4 CCDs abutted togetherabutted together

    Slot Scanning with a Scintillator and a CCD Array Slot Scanning with a Scintillator and a CCD Array (SenoScan; Fischer Imaging (now (SenoScan; Fischer Imaging (now HologicHologic))))

    Radiographics 2004:24,1752Seibert, AAPM Meeting Handout 7474KanalKanal

    7. Technologies for FFDM 7. Technologies for FFDM –– Indirect CaptureIndirect Capture

    In this system, the digital In this system, the digital detector array is constructed detector array is constructed from an afrom an a--Si thinSi thin--film transistor film transistor (TFT) matrix deposited on a (TFT) matrix deposited on a glass substrateglass substrateThe CsI scintillator is The CsI scintillator is deposited on the adeposited on the a--Si detectorSi detectorEach lightEach light--sensitive diode sensitive diode element is connected by TFTs element is connected by TFTs to control and data lines so to control and data lines so that charge produced in the that charge produced in the diode is read out in response diode is read out in response to light emission from the to light emission from the scintillatorscintillator

    FlatFlat--Panel Scintillator with an aPanel Scintillator with an a--Si Diode ArraySi Diode Array(Senographe 2000D, DS, GE Healthcare)(Senographe 2000D, DS, GE Healthcare)

    Radiographics 2004:24,1753

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    7. Technologies for FFDM 7. Technologies for FFDM –– Indirect CaptureIndirect Capture

    The GE Senographe 2000D The GE Senographe 2000D system was the first FFDM system was the first FFDM system to be approved by the system to be approved by the FDA in USAFDA in USA1,920 x 2,304 detector 1,920 x 2,304 detector elements on a 19.2 x 23elements on a 19.2 x 23--cm cm areaareaEach pixel is 100 Each pixel is 100 μμm, largest m, largest pixel size of the available pixel size of the available FFDM systemsFFDM systems

    FlatFlat--Panel Scintillator with an aPanel Scintillator with an a--Si Diode ArraySi Diode Array(Senographe 2000D, DS, GE Healthcare)(Senographe 2000D, DS, GE Healthcare)

    Radiographics 2004:24,1753 7676KanalKanal

    7. GE Senographe DS FFDM system7. GE Senographe DS FFDM system

    c.f. private document, GE Medical Systemsc.f. private document, GE Medical Systems

    Can use in association with CAD systems Can use in association with CAD systems

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    7. Technologies for FFDM 7. Technologies for FFDM –– Indirect CaptureIndirect CapturePhotostimulable Phosphor Plates (Computed Radiography) Photostimulable Phosphor Plates (Computed Radiography)

    (Fuji (Fuji –– not approved for Mammography yet)not approved for Mammography yet)

    Seibert, AAPM Meeting Handout

    When x-rays are absorbed, electronic charges are stored proportionally in “traps” in the phosphor

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    7. Technologies for FFDM 7. Technologies for FFDM –– Direct CaptureDirect Capture

    aa--Se, a good photoconductor is Se, a good photoconductor is deposited directly onto the adeposited directly onto the a--Si Si TFT substrate enabling direct TFT substrate enabling direct capturecaptureThe aThe a--Se detector directly Se detector directly converts xconverts x--rays to electronrays to electron--hole hole pairs pairs The aThe a--Si TFT converts the Si TFT converts the electronelectron--hole pairs to electronic hole pairs to electronic signalsignal25 x 2925 x 29--cm field of view, the cm field of view, the largest among all systemslargest among all systemsAccommodates all breast sizesAccommodates all breast sizesPixel size is 70 mmPixel size is 70 mm

    FlatFlat--Panel aPanel a--Se Array (Lorad Selenia, Hologic)Se Array (Lorad Selenia, Hologic)

    http://www.hologic.com/wh/digisel.htm

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    7. Technologies for FFDM 7. Technologies for FFDM –– Direct CaptureDirect Capture

    Approved recentlyApproved recently24 x 2924 x 29--cm field of viewcm field of viewAccommodates all breast sizesAccommodates all breast sizes

    FlatFlat--Panel aPanel a--Se Array (Se Array (MammomatMammomat NovationNovation, Siemens), Siemens)

    http://www.medical.siemens.com 8080KanalKanal

    7. Technologies for FFDM7. Technologies for FFDM

    http://www.hologic.com/oem/pdf/DROverviewR-007_Nov2000.pdf

    Fuji/Kodak Fischer (Hologic)

    GE Lorad/Hologic

    Siemens

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    7. Technologies for FFDM7. Technologies for FFDM

    Radiology 2005:234,353 8282KanalKanal

    7. FFDM 7. FFDM –– Radiation DoseRadiation Dose

    DS systemDS systemContrast mode Contrast mode -- 219 219 mradmrad or 2.19 mGyor 2.19 mGyStandard mode Standard mode -- 109 109 mradmrad or 1.09 mGy (28 kV, 48 mAs)or 1.09 mGy (28 kV, 48 mAs)Dose mode Dose mode –– 89.2 89.2 mradmrad or 0.892 mGyor 0.892 mGy

    FilmFilm--screenscreenStandard mode Standard mode –– 151 151 mradmrad or 1.51 mGy (28 kV, 65 mAs)or 1.51 mGy (28 kV, 65 mAs)

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    7. Storage of Digital Images7. Storage of Digital ImagesSignals are digitized into one of 2Signals are digitized into one of 2nn intensity levels within each pixel, where intensity levels within each pixel, where nnis the number of bitsis the number of bitsIf 12 bits, 4,096 signal values, if 14 bits, 16,384 signal valueIf 12 bits, 4,096 signal values, if 14 bits, 16,384 signal valuessA digital detector of N pixels requires 2N bytes of storage (2 bA digital detector of N pixels requires 2N bytes of storage (2 bytes per pixel)ytes per pixel)

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    7. Display of Digital Images7. Display of Digital Images

    Radiographics 2004:24,1757

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    7. Economics of FFDM7. Economics of FFDM

    SFM systems cost well under $100,000SFM systems cost well under $100,000FFDM systems cost in the range of $300,000 FFDM systems cost in the range of $300,000 -- $450,000$450,000One attractive reason for centers to One attractive reason for centers to ““go digitalgo digital”” is the higher is the higher reimbursement rates approved by Medicare in 2003reimbursement rates approved by Medicare in 2003SFM SFM -- $83.03 (2008) $83.03 (2008) FFDM FFDM -- $133.69 (2008)$133.69 (2008)

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    7. Expected Benefits of FFDM7. Expected Benefits of FFDM

    The costs of FFDM systems should be compared along with the The costs of FFDM systems should be compared along with the inherent benefits of the digital technology prior to the purchasinherent benefits of the digital technology prior to the purchase:e:

    Reduced recall ratesReduced recall ratesIncreased patient throughputIncreased patient throughputIncreased early detection of breast cancerIncreased early detection of breast cancerDecreased falseDecreased false--negative biopsy resultsnegative biopsy resultsDecreasing film and processing costsDecreasing film and processing costsIncreasing the caseload of each mammography roomIncreasing the caseload of each mammography room

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    7. Clinical Trials and Phantom Studies7. Clinical Trials and Phantom Studies

    Larger screening study screened 49,500 womenLarger screening study screened 49,500 womenDigital Mammographic Imaging Screening TrialDigital Mammographic Imaging Screening Trial (DMIST), funded by (DMIST), funded by NCI and conducted by ACRIN NCI and conducted by ACRIN (http://www.acrin.org/6652_protocol.html)(http://www.acrin.org/6652_protocol.html)

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    7. Advantages and Disadvantages7. Advantages and Disadvantages

    AdvantagesAdvantagesOptimize postOptimize post--processing of imagesprocessing of imagesPermit computerPermit computer--aided detection to improve the detection of aided detection to improve the detection of lesionslesionsStorage of images easierStorage of images easier

    DisadvantagesDisadvantagesImage display and system costImage display and system costLimiting spatial resolution is inferior to film, 10 lp/mm vs. 20Limiting spatial resolution is inferior to film, 10 lp/mm vs. 20lp/mmlp/mm

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    Take Home PointsTake Home Points

    Quality Assurance important and regulated by MQSA in Quality Assurance important and regulated by MQSA in mammographymammography

    Radiologist oversees programRadiologist oversees programPhysicist and technologist responsibilitiesPhysicist and technologist responsibilitiesPhantom Phantom –– 4 fibers, 3 masses, 3 specks should be seen4 fibers, 3 masses, 3 specks should be seen

    Stereotactic units used for breast biopsy, use geometry to calcuStereotactic units used for breast biopsy, use geometry to calculate late lesion locationlesion locationDigital mammography becoming commonDigital mammography becoming common

    GE, Fischer, GE, Fischer, Lorad/HologicLorad/Hologic, Siemens approved by FDA , Siemens approved by FDA Indirect and Direct systems usedIndirect and Direct systems usedCAD used in association with digital systemsCAD used in association with digital systemsAdvantages and disadvantagesAdvantages and disadvantages

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    8. Quality Assurance & Quality Control8. Quality Assurance & Quality Control

    Regulations mandated by the MQSA of 1992 specify the Regulations mandated by the MQSA of 1992 specify the operational and technical requirements necessary to perform operational and technical requirements necessary to perform mammography in the USAmammography in the USA

    For a facility to perform mammography legally under MQSA, it For a facility to perform mammography legally under MQSA, it must be certified and accredited (ACR or some states)must be certified and accredited (ACR or some states)

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    8. Quality Assurance & Quality Control8. Quality Assurance & Quality Control

    The accreditation body verifies that the mammography facility The accreditation body verifies that the mammography facility meets standards set forth by the MQSA such as initial meets standards set forth by the MQSA such as initial qualifications, continuing experience, education of physicians, qualifications, continuing experience, education of physicians, technologists and physicists, equipment quality control etc.technologists and physicists, equipment quality control etc.

    Certification is the approval of a facility by the U.S. FDA to Certification is the approval of a facility by the U.S. FDA to provide mammography services, and is granted when provide mammography services, and is granted when accreditation is achievedaccreditation is achieved

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    8. Radiologist Responsibilities8. Radiologist Responsibilities

    Responsibilities includeResponsibilities include

    Ensuring that technologists are appropriately trained in Ensuring that technologists are appropriately trained in mammography and perform required quality assurance mammography and perform required quality assurance measurementsmeasurements

    Providing feedback to the technologists regarding aspects of Providing feedback to the technologists regarding aspects of clinical performance and QC issuesclinical performance and QC issues

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    8. Radiologist Responsibilities8. Radiologist Responsibilities

    Responsibilities includeResponsibilities include

    Having a qualified medical physicist perform the necessary testsHaving a qualified medical physicist perform the necessary testsand administer the QC programand administer the QC program

    Ultimate responsibility for mammography quality assurance rests Ultimate responsibility for mammography quality assurance rests with the radiologist in charge of the mammography practicewith the radiologist in charge of the mammography practice

    The medical physicist and technologist are responsible for the The medical physicist and technologist are responsible for the QC testsQC tests

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    8. Mammography phantom8. Mammography phantom

    Is a test object that simulates the radiographic characteristicsIs a test object that simulates the radiographic characteristics of of compressed breast tissues, and contains components that model compressed breast tissues, and contains components that model breast disease and cancer in the phantom imagebreast disease and cancer in the phantom image

    It is intended to mimic the attenuation characteristics of a It is intended to mimic the attenuation characteristics of a ““standard standard breastbreast”” of 4.2of 4.2--cm compressed breast thickness of 50% adipose and cm compressed breast thickness of 50% adipose and 50% glandular tissue composition50% glandular tissue composition

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    8. Mammography phantom8. Mammography phantom

    6 nylon fibers, 5 simulated calcification groups, 5 low contrast6 nylon fibers, 5 simulated calcification groups, 5 low contrast disks disks that simulate massesthat simulate masses

    To To pass the MQSA quality standards, at least 4 fibers, 3 calcificatpass the MQSA quality standards, at least 4 fibers, 3 calcification ion groups and 3 masses must be clearly visiblegroups and 3 masses must be clearly visible (with no obvious (with no obvious artifacts) at an average glandular dose of less than 3 mGyartifacts) at an average glandular dose of less than 3 mGy

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    c.f. Bushberg, c.f. Bushberg, et al. The et al. The Essential Essential Physics of Physics of Medical Medical Imaging, 2Imaging, 2ndnded., p. 228.ed., p. 228.

    8. Mammography Phantom8. Mammography Phantom

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    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 226.ed., p. 226.

    8. Technologist Quality Control8. Technologist Quality Control

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    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 226.ed., p. 226.

    8. Technologist Quality Control8. Technologist Quality Control

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    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 226.ed., p. 226.

    8. Technologist Quality Control8. Technologist Quality Control

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    c.f. Bushberg, et al. The Essential Physics of Medical c.f. Bushberg, et al. The Essential Physics of Medical Imaging, 2Imaging, 2ndnd ed., p. 226.ed., p. 226.

    8. Technologist Quality Control8. Technologist Quality Control

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    c.f. Bushberg, et c.f. Bushberg, et al. The Essential al. The Essential Physics of Medical Physics of Medical Imaging, 2Imaging, 2ndnd ed., ed., p. 227.p. 227.

    8. 8. Physicist Physicist Quality Quality ControlControl

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    1.1. The average glandular dose for a 4.2 cm compressed breast is The average glandular dose for a 4.2 cm compressed breast is about:about:

    A. 1.3 mGy (130mrad)A. 1.3 mGy (130mrad)B. 1.7 mGy (170mrad)B. 1.7 mGy (170mrad)C. 3.0 mGy (300 mad)C. 3.0 mGy (300 mad)D. 120mRD. 120mRE. 170mRE. 170mR

    QuestionQuestion

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    1.1. Breast doses in mammography are most likely to be reduced by Breast doses in mammography are most likely to be reduced by increasingincreasing the:the:

    (A) X(A) X--ray tube voltageray tube voltage(B) X(B) X--ray tube currentray tube current(C) Focal spot size(C) Focal spot size(D) Grid ratio(D) Grid ratio(E) Number of views taken(E) Number of views taken

    QuestionQuestion

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    1.1. Mammograms cannot be processed if the weekly phantom does Mammograms cannot be processed if the weekly phantom does not pass. A passing score would be:not pass. A passing score would be:

    Fibers Fibers Speck Speck Masses Masses Disk Disk Groups Groups ContrastContrast

    A. A. 4.0 4.0 3.0 3.0 3.0 3.0 0.400.40B. B. 5.0 5.0 2.5 2.5 3.0 3.0 0.500.50C. C. 3.5 3.5 4:0 4:0 3.0 3.0 0.500.50D. D. 4.04.0 4.0 4.0 2.5 2.5 0.500.50E. E. 6.0 6.0 5.0 5.0 2.5 2.5 0.50.5

    QuestionQuestion

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    QuestionQuestion

    11. In mammography, a fiber interspaced grid is preferred over . In mammography, a fiber interspaced grid is preferred over aluminum because it:aluminum because it:

    (A) Reduces the dose(A) Reduces the dose(B) Improves resolution(B) Improves resolution(C) Removes more scatter(C) Removes more scatter(D) Reduces image mottle(D) Reduces image mottle(E) Improves contrast(E) Improves contrast

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    QuestionQuestion

    1.1. Ideally, the AEC (Ideally, the AEC (phototimerphototimer) sensor in mammography should be ) sensor in mammography should be placed:placed:

    A. As close to the chest wall as possible.A. As close to the chest wall as possible.B. Under the densest portion of the breast. B. Under the densest portion of the breast. C. Under the least dense portion of the breast.C. Under the least dense portion of the breast.D. Under the most anterior portion of the breast.D. Under the most anterior portion of the breast.E. In the center of the breast.E. In the center of the breast.

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    QuestionQuestion

    1. 1. Which grid would be the best choice for use as a stationary gridWhich grid would be the best choice for use as a stationary grid in in mammography?mammography?

    A. 44 lines/cm, 5:1 ratioA. 44 lines/cm, 5:1 ratioB. 44 lines/cm, 12:1 ratioB. 44 lines/cm, 12:1 ratioC. 80 lines/cm, 5:1 ratioC. 80 lines/cm, 5:1 ratioD. 80 lines/cm, 12:1 ratioD. 80 lines/cm, 12:1 ratioE. Any of the above, as long as they are made of carbon fiberE. Any of the above, as long as they are made of carbon fiber

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    QuestionQuestion

    1.1. Which of the following is Which of the following is not not true? Vigorous compression in true? Vigorous compression in mammography reduces:mammography reduces:

    A. Patient dose.A. Patient dose.B. Scatter.B. Scatter.C. Motion C. Motion unsharpnessunsharpness..D. Subject contrast.D. Subject contrast.

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    QuestionQuestion

    1.1. Magnification radiography using current imaging equipment:Magnification radiography using current imaging equipment:

    (A) Reduces the entrance skin exposure(A) Reduces the entrance skin exposure(B) Improves the definition of fine detail(B) Improves the definition of fine detail(C) Requires large focal spots larger than 0.3 mm(C) Requires large focal spots larger than 0.3 mm(D) Reduces film density(D) Reduces film density(E) Requires moving the film further from the tube(E) Requires moving the film further from the tube