BREAST MRI

Principles, Procedure, and Technique

Dr Ghadeer AlBaloul

Assistant Professor

Faculty of Allied Health

Kuwait University

Basic Anatomy of the Breast

BREAST IMAGING

1- Digital Mammography

Digital Mammography

Advantages

• High spatial resolution

• Good as an early detection modality

• Readily available in most medical centers

• Affordable for patients

Disadvantages

• Radiation dose

• Less sensitive in younger patients

• Less sensitive in breast implant evaluation

2- Ultrasound

Breast Ultrasound

Advantages

• Inexpensive

• Readily available

• Uses no ionizing radiation

• Can differentiate between solid and cystic lesions

• Can be used to evaluate breast implants

• Used in combination with mammography for increased sensitivity and accuracy.

Disadvantages

• Operator dependent

• Can increase the number of false-positives

3- Breast MRI

Breast MRI

Advantages

• No ionizing radiation exposure

• Highly sensitive in the detection of lesions especially in dense breasts

• Highly specific when used in combination with digital mammography

• Can be used for preoperative staging

Disadvantages

• Expensive

• Not readily available

• Long waiting lists

• Not suitable for all patients

• Long scan times

Indications of Breast MRI/MR-guided Biopsy

• Screening • High risk patients

• Contralateral breast in patients with new breast malignancy

• Patients with breast augmentation

• Extent of Disease • Determining the presence of multi focality

• Invasion deep to fascia

• After conservative surgery to evaluate the presence of residual disease

• Evaluation of treatment response before, during and after chemotherapy

Indications of Breast MRI/MR-Guided Biopsy

• Additional evaluation of clinical or imaging findings

• Recurrence of breast cancer

• Metastatic cancer where primary is unknown and suspected to be of breast origin

• Lesion characterization where other imaging or clinical findings are inconclusive

• Postoperative tissue reconstruction evaluation

• MRI-guided biopsy in lesions that are demonstrable only by MRI

Other Considerations in Breast MRI

• Screening breast MRI is not recommended for the general population/average risk patients

• False positives- findings not evident clinically or on mammography or ultrasound

• Treatment choices – should be correlated carefully with biopsy findings

• Inappropriate uses of breast MRI- should not replace mammographic or ultrasound scans because it can miss some cancers that mammography can detect

Specifications of the examination

• All patients should undergo standard mammography in addition to breast MRI unless it is contraindicated.

• Previous mammography reports should be available for correlation

• Breast MRI request forms should contain sufficient information to demonstrate the medical necessity of the examination (e.g. signs, symptoms, history)and allow for proper performance and interpretation

Patient Selection and Preparation

• Patient should be interviewed and screened for possible contraindications for MRI

• Patients suffering from anxiety or claustrophobia may require sedation or additional assistance

• A recovery area is necessary and appropriate personnel must be available to observe patients after sedation

• Scans must be performed between day 10-15 of the menstrual cycle to avoid false negatives and false positives due to increased parenchymalenhancement

Equipment specifications

• A minimum of 1.5T magnet to achieve optimal resolution• Use of dedicated bilateral breast coils • Slice thickness should be 3mm or less• Fat suppression is helpful to reduce fat signal while

preserving SNR• Subtraction used with fat suppression to assess contrast

enhancement is recommended, motion correction may also be helpful in reducing artifacts

• Simultaneous imaging of both breasts should be performed• Scan time- A pre-contrast scan should be performed, scan

time in relation to contrast injection is extremely important (specific intervals separated by 4 mins or less)

Additional Equipment

• Breast Coils

• MR compatible biopsy needle

• MR compatible automatic injector

• Ear plugs

Patient Positioning

• Patient is usually in prone position• Straps may be used to further limit patient motion• Clear communication with the patient to ensure they

are in a comfortable position is very important to avoid motion during the investigation

• Breasts are positioned within the breast coil and may be further supported by foam pads to avoid motion

• Longitudinal positioning light should be aligned with midline

• Horizontal alignment should pass through the center of the coil

Common Protocols• Axial T1-weighted pre-contrast provides morphological information such as

fat and glandular structures including both axillae, supraclavicular fossae, chest wall and anterior mediastinum (for enlarged lymph nodes)

• Axial T2-weighted without fat saturation for demonstrating cysts and microcysts in addition to water-containing or edematous lesions

• Axial T2-weighted with fat saturation to create MR ductography (in cases of discharge)

• Dynamic contrast enhanced T1-wieghted (e.g. 3D spoiled GRE short TR, short TE, shallow flip angle, applied before administration of contrast medial and repeated several times after contrast

• For tumor detection fat suppression sequences are used to differentiate between fat and enhancing lesions

• T2 with water suppression, and STIR are used in visualizing implants

Additional Protocols

• MR spectroscopy: is based on an abnormal Choline peak in malignant tumors, this can improve the predictive value of MRI and may avoid the need for biopsy in some cases

• Diffusion: based on the quantification of water molecule motion in tissues (reduced water molecule motion in malignant lesions compared with benign). It is used mainly in breast imaging to optimize characterization of lesions and to improve detection of small lesions.

MR-Guided Biopsy and Lesion Localization

• Used in lesions that are neither palpable or visible on conventional imaging

• Must use a dedicated bilateral breast coil

• Spatial and temporal resolution must be adequate

• A T1-weighted sequence should be obtained for at least three time points (pre and post contrast)

• Reporting should be done by a radiologist with good MR breast experience

Image Optimization

• SNR is usually high in breast coils

• Fine matrix can be obtained for better spatial resolution

• Smallest FOV, thin slice and small gap should be maintained for highest resolution

• Prone position reducing respiratory artifact

• Flow artifact can be overcome by swapping phase encoding axis

Artifacts and Solutions

Artefact Sign Solution

Motion •Fuzzy lines•Propagation in the phase encoding direction•Enhancement on subtracted sequences no found on native images

•Comfortable position for the patient•Foam wedges in the coil in case of small breast

Aliasing Ghost images •Increase FOV•Modify the phase encoding direction

Magnetic Susceptibility

Tissue distortion, hypersignal spots, fall in signal

Reduce TE

Non-uniformity of Fat-Saturation

Occurs with non-uniform field because of non-selection of fatty pixels

Reshim the magnet

Contrast Media

• Gadolinium contrast media is given to evaluate lesions but not generally required in evaluating implant integrity or rupture

• Contrast media should only be given 10-15 days into the menstrual cycle to minimize enhancement of normal breast tissue

• Gadolinium should be administered as a bolus with a standard dose 0.1mmol/kg followed by a saline flush of at least 10ml

• All breast parenchyma enhances after a short delay therefore if each breast is being examined individually (not recommended) at least 24 hours should be allowed for the contrast to be eliminated from the previous examination

Patient Care and Education

• Most patients will be extremely anxious • Careful explanation and reassurance is very

important • It is highly important that patients do not move

during the exam, therefore careful positioning is crucial from the start

• Examinations should be done 10-15 days into the menstrual cycle due to hormonal changes

• Ear plugs or ear phones should be provided to protect the patient’s ears

QC, Safety, Infection Control

• Institutional policies of QC , safety and infection control should be developed and maintained

• Equipment monitoring should be conducted in accordance with ACR technical standard for diagnostic medical physics performance monitoring of MRI equipment, including testing of breast coils.

• Reviews should also include the accuracy of interpretation as well as the appropriateness of the examination.

• Complications or adverse events should be reported, analyzed and reviewed to improve patient care.

References

• ACR practice parameter for the performance of contrast enhanced magnetic resonance imaging (MRI) of the breast. Revised 2013

• Kinkel K, et al. Breast MRI: guidelines from the European Society of Breast Imaging. Eur Radiol (2008) 18:1307-1318.

• Mahoney M, and Argus A. Clinical indications for Breast MRI. Appl Radiol. 2010, 39(10):10-19.

• Thomassin-Naggara I, et al. Tips and techniques in breast MRI. Diagnostic and interventional imaging (2012) 93, 828-839.

• Westbrook Catherine. Handbook of MRI Technique, second edition. Blackwell Publishing 2003.