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Radiation Protection inRadiation Protection inRadiotherapyRadiotherapy

Part 10Part 10

Good Practice including Radiation Good Practice including Radiation Protection in EBTProtection in EBT

Lecture 3 (cont.): Radiotherapy Treatment PlanningLecture 3 (cont.): Radiotherapy Treatment Planning

IAEA Training Material on Radiation Protection in Radiotherapy

Part 10, lecture 3 (cont.): Radiotherapy treatment planning

2Radiation Protection in Radiotherapy

C. CommissioningC. Commissioning

Complex procedure depending very much on Complex procedure depending very much on equipmentequipment

Protocols exist and should be followedProtocols exist and should be followed Useful literature:Useful literature:

J van Dyk et al. 1993 Commissioning and QA of treatment J van Dyk et al. 1993 Commissioning and QA of treatment planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: 261-273planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: 261-273

J van Dyk et al, 1999 Computerised radiation treatment planning J van Dyk et al, 1999 Computerised radiation treatment planning systems.systems. In: Modern Technology of Radiation Oncology (Ed.: J In: Modern Technology of Radiation Oncology (Ed.: J Van Dyk) Chapter Van Dyk) Chapter 88. Medical Physics Publishing, Wisconsin, . Medical Physics Publishing, Wisconsin, ISBN 0-944838-38-3, pp. ISBN 0-944838-38-3, pp. 231-286231-286..



Acceptance testing and Acceptance testing and commissioningcommissioning

Acceptance testing:Acceptance testing: Check that the system conforms with Check that the system conforms with specifications.specifications.

Documentation of specifications either in the tender, in Documentation of specifications either in the tender, in guidelines or manufacturers’ notes – may test against guidelines or manufacturers’ notes – may test against standard data (standard data (e.g.e.g. Miller Miller et al.et al. 1995, AAPM report 55) 1995, AAPM report 55)

Subset of commissioning procedureSubset of commissioning procedure Takes typically two weeksTakes typically two weeks

Commissioning:Commissioning: Getting the system ready for clinical use Getting the system ready for clinical use Takes typically several months for modern 3D systemTakes typically several months for modern 3D system



Some equipment requiredSome equipment required

Scanning beam data acquisition systemScanning beam data acquisition system Calibrated ionization chamberCalibrated ionization chamber Slab phantom including Slab phantom including

inhomogeneitiesinhomogeneities Radiographic filmRadiographic film Anthropomorphic phantomAnthropomorphic phantom Ruler, spirit levelRuler, spirit level



CommissioningCommissioning

A. Non-dose related componentsA. Non-dose related components

B. Photon dose calculationsB. Photon dose calculations

C. Electron dose calculationsC. Electron dose calculations

(D. Brachytherapy - covered in part 11)(D. Brachytherapy - covered in part 11)

E. Data transferE. Data transfer

F. Special proceduresF. Special procedures



A. Non-dose componentsA. Non-dose components

Image inputImage input Geometry and scaling of Geometry and scaling of

Digitizer,Digitizer, ScansScans OutputOutput

Text informationText information Anatomical structure informationAnatomical structure information

CT numbersCT numbers Structures (outlining tools, non-axial Structures (outlining tools, non-axial

reconstruction, “capping”,…)reconstruction, “capping”,…)



Electron and photon beamsElectron and photon beams

Description (machine, modality, energy)Description (machine, modality, energy) Geometry (Gantry, collimator, table, Geometry (Gantry, collimator, table,

arcs)arcs) Field definition (Collimator, trays, MLC, Field definition (Collimator, trays, MLC,

applicators, …)applicators, …) Beam modifiers (Wedges, dynamic Beam modifiers (Wedges, dynamic

wedges, compensators, bolus,…)wedges, compensators, bolus,…) NormalizationNormalization



B. Photon calculation testsB. Photon calculation tests

Point dosesPoint doses TAR, TPR, PDD, PSFTAR, TPR, PDD, PSF Square, rectangular and irregular fieldsSquare, rectangular and irregular fields Inverse square lawInverse square law Attenuation factors (trays, wedges,…)Attenuation factors (trays, wedges,…) Output factorsOutput factors

Machine settingsMachine settings



Photon calculation tests (cont.)Photon calculation tests (cont.)

Dose distributionDose distribution HomogenousHomogenous

Profiles (open and wedged)Profiles (open and wedged) SSD/SADSSD/SAD Contour correctionContour correction Blocks, MLC, asymmetric jawsBlocks, MLC, asymmetric jaws Multiple beamsMultiple beams ArcsArcs Off axis (open and wedged)Off axis (open and wedged) Collimator/couch rotationCollimator/couch rotation

PTW waterphantom



Photon calculation tests (cont.)Photon calculation tests (cont.)

Dose distributionDose distribution InhomogeneousInhomogeneous

Slab geometrySlab geometry Other geometriesOther geometries Anthropomorphic phantomAnthropomorphic phantom

In vivo In vivo dosimetry at least for the dosimetry at least for the first patientsfirst patients

Following the incident in Panama, the IAEA Following the incident in Panama, the IAEA recommends a largely extended recommends a largely extended in vivoin vivo dosimetry dosimetry program to be implementedprogram to be implemented



C. Electron calculationC. Electron calculation

Similar to photons, however, additional:Similar to photons, however, additional: Bremsstrahlung tailBremsstrahlung tail Small field sizes require special considerationSmall field sizes require special consideration Inhomogeneity has more impactInhomogeneity has more impact

It is possible to use reference data for It is possible to use reference data for comparison (Shui comparison (Shui et al.et al. 1992 “Verification 1992 “Verification data for electron beam dose algorithms” Med. data for electron beam dose algorithms” Med. Phys. 19: 623-636)Phys. 19: 623-636)



E. Data transferE. Data transfer

Pixel values, CT numbersPixel values, CT numbers Missing linesMissing lines Patient/scan informationPatient/scan information OrientationOrientation Distortion, magnificationDistortion, magnification

All needs verification!!!



F. Special proceduresF. Special procedures

Junctions Junctions Electron abuttingElectron abutting Stereotactic proceduresStereotactic procedures Small field procedures (Small field procedures (e.g.e.g. for eye for eye

treatment)treatment) IMRTIMRT TBI, TBSITBI, TBSI Intraoperative radiotherapyIntraoperative radiotherapy



Sources of uncertaintySources of uncertainty Patient localization Patient localization Imaging (resolution, distortions,…)Imaging (resolution, distortions,…) Definition of anatomy (outlines,…)Definition of anatomy (outlines,…) Beam geometryBeam geometry Dose calculationDose calculation Dose display and plan evaluationDose display and plan evaluation Plan implementationPlan implementation



Typical accuracy required Typical accuracy required (examples)(examples)

Square field CAX: Square field CAX: 1%1%

MLC penumbra: 3%MLC penumbra: 3% Wedge outer beam: Wedge outer beam:

5%5% Buildup-region: 30%Buildup-region: 30% 3D inhomogeneity 3D inhomogeneity

CAX: 5%CAX: 5%From AAPM TG53



Typical accuracy required Typical accuracy required (examples)(examples)

Square field CAX: Square field CAX: 1%1%

MLC penumbra: 3%MLC penumbra: 3% Wedge outer beam: Wedge outer beam:

5%5% Buildup-region: 30%Buildup-region: 30% 3D inhomogeneity 3D inhomogeneity

CAX: 5%CAX: 5%

Note:Uncertainties have two components:Dose (given in %)Location (given in mm)



Time and staff requirements for Time and staff requirements for commissioning (J Van Dyk 1999)commissioning (J Van Dyk 1999) Photon beam: 4-7 daysPhoton beam: 4-7 days Electron beam: 3-5 daysElectron beam: 3-5 days Brachytherapy: 1 day per source typeBrachytherapy: 1 day per source type Monitor unit calculation: 0.3 days per Monitor unit calculation: 0.3 days per

beambeam



Some ‘tricky’ issuesSome ‘tricky’ issues

Dose Volume Histograms - watch sampling, Dose Volume Histograms - watch sampling, grid, volume determination, normalization grid, volume determination, normalization (1% volume represents still > 10E7 cells!)(1% volume represents still > 10E7 cells!)

Biological parameters - Tumour Control Biological parameters - Tumour Control Probability (TCP) and Normal Tissue Probability (TCP) and Normal Tissue Complication Probability (NTCP) depend on Complication Probability (NTCP) depend on the model used and the parameters which the model used and the parameters which are available.are available.



Commissioning summaryCommissioning summary

Probably the most complex task for RT Probably the most complex task for RT physicists - takes considerable time and trainingphysicists - takes considerable time and training

Partial commissioning needed for system Partial commissioning needed for system upgrades and modificationupgrades and modification

Documentation and hardcopy data must be Documentation and hardcopy data must be includedincluded

Training is essential and courses are availableTraining is essential and courses are available Independent check highly recommendedIndependent check highly recommended

Quick Question:Quick Question:

What ‘commissioning’ needs to be done for a hand What ‘commissioning’ needs to be done for a hand calculation method of treatment times for a superficial calculation method of treatment times for a superficial

X Ray treatment unit?X Ray treatment unit?



Superficial beamSuperficial beam HVLHVL Percentage depth dose (may be look up table)Percentage depth dose (may be look up table) Normalization point (typically the surface)Normalization point (typically the surface) Scatter (typically back scatter) factorScatter (typically back scatter) factor Applicator and/or cone factorApplicator and/or cone factor Timer accuracyTimer accuracy On/off effectOn/off effect Other effects which may affect dose (Other effects which may affect dose (e.g.e.g. electron electron

contamination)contamination)



Quality Assurance of a treatment Quality Assurance of a treatment planning systemplanning system QA is typically a subset of commissioning QA is typically a subset of commissioning

teststests Protocols:Protocols:

As for commissioning and:As for commissioning and: M Millar M Millar et al.et al. 1997 ACPSEM position paper. 1997 ACPSEM position paper.

Australas. Phys. Eng. Sci. Med. 20 SupplementAustralas. Phys. Eng. Sci. Med. 20 Supplement B Fraas B Fraas et al.et al. 1998 AAPM Task Group 53: QA for 1998 AAPM Task Group 53: QA for

clinical RT planning. Med. Phys. 25: 1773-1829clinical RT planning. Med. Phys. 25: 1773-1829



Aspects of QA (compare also Aspects of QA (compare also part 12 of the course)part 12 of the course) Training - qualified staffTraining - qualified staff Checks against a benchmark - Checks against a benchmark -

reproducibilityreproducibility Treatment verificationTreatment verification QA administrationQA administration

CommunicationCommunication DocumentationDocumentation

Awareness of procedures requiredAwareness of procedures required



Quality AssuranceQuality Assurance



Quality AssuranceQuality Assurance

Check prescriptionHand calculation of

treatment time



Frequency of tests for planning (and Frequency of tests for planning (and suggested acceptance criteria)suggested acceptance criteria)

Commissioning and significant upgradesCommissioning and significant upgrades See aboveSee above

Annual: Annual: MU calculation (2%)MU calculation (2%) Reference plan set (2% or 2mm)Reference plan set (2% or 2mm) Scaling/geometry input/output devices (1mm)Scaling/geometry input/output devices (1mm)

MonthlyMonthly Check sumCheck sum Some reference test sets Some reference test sets



Frequency of tests (cont.)Frequency of tests (cont.)

WeeklyWeekly Input/output devicesInput/output devices

Each time system is turned onEach time system is turned on Check sum (no change)Check sum (no change)

Each planEach plan CT transfer - orientation?CT transfer - orientation? Monitor units - independent checkMonitor units - independent check Verify input parameters (field size, energy, Verify input parameters (field size, energy, etc.etc.))



Treatment planning QA summaryTreatment planning QA summary

Training most essentialTraining most essential Staying alert is part of QAStaying alert is part of QA Documentation and reporting necessaryDocumentation and reporting necessary Treatment verification Treatment verification in vivo in vivo can play can play

an important rolean important role


How much time should be spent on treatment How much time should be spent on treatment planning QC?planning QC?



Staff and time requirementsStaff and time requirements (source J. Van Dyk (source J. Van Dyk et al.et al. 1999) 1999)

Reproducibility tests/QC: 1 week per Reproducibility tests/QC: 1 week per yearyear

In vivo In vivo dosimetry: about 1 hour per dosimetry: about 1 hour per patient - aim for about 10% of patientspatient - aim for about 10% of patients

Manual check of plans and monitor Manual check of plans and monitor units: 20 minutes per planunits: 20 minutes per plan



QA in treatment planningQA in treatment planning

The planning system

QA of the system

Plan of a patient

QA of the plan



QC of treatment plansQC of treatment plans

Treatment plan: Treatment plan: Documentation ofDocumentation of treatment set-up,treatment set-up, machine parameters,machine parameters, calculation details,calculation details, dose distribution,dose distribution, patient information,patient information, record and verify record and verify

datadata

Consists typically of:Consists typically of: Treatment sheetTreatment sheet Isodose planIsodose plan Record and Verify Record and Verify

entryentry Reference films Reference films

(simulator, DRR)(simulator, DRR)



QC of treatment plansQC of treatment plans

Check plan for each patient prior to Check plan for each patient prior to commencement of treatmentcommencement of treatment

Plan must bePlan must be Complete from prescription to set-up Complete from prescription to set-up

information and dose delivery adviseinformation and dose delivery advise Understandable by colleaguesUnderstandable by colleagues Document treatment for future useDocument treatment for future use



Who should do it?Who should do it?

Treatment sheet checking should involve Treatment sheet checking should involve senior staffsenior staff

It is an advantage if different professions It is an advantage if different professions can be involved in the processcan be involved in the process

Reports must go to clinicians and the Reports must go to clinicians and the relevant QA committeerelevant QA committee



Example for physics treatment sheet Example for physics treatment sheet checking procedurechecking procedure

1. Check prescription (energy/dose/fractionation is everything signed ?) 2. Check prescription and calculation page for consistency: Isocentric (SAD) or fixed distance (SSD) set-up ? Are all

necessary factors used? Check both,dose/fraction and number of fractions.3. Check normalisation value (Plan or data sheets).4. Check outline, separation and prescription depth.5. Turn to treatment plan: Does it look ok ? Outline ? Bolus ? Isocentre placement and normalisation point ? Any concerns

regarding the use of algorithms near surfaces or inhomogeneities? Would you expect problems in planes not shown ? Prescription ?

6. Check and compare with treatment sheet calculation page: treatment unit and type, field names, weighting, wedges, blocks, field size (FS), focus surface distance (FSD), Tissue Air Ratio (TAR) (if isocentric treatment) - is this consistent with entries in treatment log page?

7. Electrons only: …8. Photons only: …9. Check shadow tray factor, wedge factor. Are any other attenuation factors required (e.g. couch, headrest, table tray...) ? 10. Check inverse square law factor (in electron treatments: is the virtual FSD appropriate?) 11. Calculate monitor units. Is time entry ok ? 12. Check if critical organ (e.g. spinal cord, lens, scrotum) dose or hot spot dose is required. If so, is it calculated correctly ? 13. Suggest in vivo dosimetry measurements if appropriate. Sign calculation sheet (if everything is ok). 14. Compare results on calculation page with entries in treatment log. 15. Check diagram and/or set up description: is there anything else worth to consider ? 16. Sign top of treatment sheet (specify what parts where checked if not all fields were checked). 17. Contact planning staff if required. Sign off physics log book.



Example for physics treatment sheet Example for physics treatment sheet checking procedurechecking procedure

1. Check prescription (energy/dose/fractionation is everything signed ?)

2. Check prescription and calculation page for consistency: Isocentric (SAD) or fixed distance (SSD) set-up ? Are all necessary factors used? Check both,dose/fraction and number of fractions.

3. Check normalisation value (Plan or data sheets).4. Check outline, separation and prescription depth.5. Turn to treatment plan: Does it look ok ? Outline ?

Bolus ? Isocentre placement and normalisation point ? Any concerns regarding the use of algorithms near surfaces or inhomogeneities? Would you expect problems in planes not shown ? Prescription ?



Example for physics treatment sheet Example for physics treatment sheet checking procedure (cont.)checking procedure (cont.)

6. Check and compare with treatment sheet calculation page: treatment unit and type, field names, weighting, wedges, blocks, field size (FS), focus surface distance (FSD), Tissue Air Ratio (TAR) (if isocentric treatment) - is this consistent with entries in treatment log page?

7. Electrons only: …8. Photons only: …9. Check shadow tray factor, wedge factor. Are any other

attenuation factors required (e.g. couch, headrest, table tray...) ?

10. Check inverse square law factor (in electron treatments: is the virtual FSD appropriate?)

11. Calculate monitor units. Is time entry ok ? 12. Check if critical organ (e.g. spinal cord, lens, scrotum) dose

or hot spot dose is required. If so, is it calculated correctly ?



Example for physics treatment sheet Example for physics treatment sheet checking procedure (cont.)checking procedure (cont.)

13. Suggest in vivo dosimetry measurements if appropriate. Sign calculation sheet (if everything is ok).

14. Compare results on calculation page with entries in treatment log.

15. Check diagram and/or set up description: is there anything else worth to consider ?

16. Sign top of treatment sheet (specify what parts where checked if not all fields were checked).

17. Contact planning staff if required. Sign off physics log book.



Treatment plan QA summaryTreatment plan QA summary

Essential part of departmental QAEssential part of departmental QA Part of patient recordsPart of patient records Multidisciplinary approachMultidisciplinary approach


What advantages has a multidisciplinary What advantages has a multidisciplinary approach to QC of treatment plans?approach to QC of treatment plans?



Did we achieve the objectives?Did we achieve the objectives? Understand the general principles of Understand the general principles of

radiotherapy treatment planningradiotherapy treatment planning Appreciate different dose calculation Appreciate different dose calculation

algorithmsalgorithms Be able to apply the concepts of optimization Be able to apply the concepts of optimization

of medical exposure throughout the treatment of medical exposure throughout the treatment planning processplanning process

Appreciate the need for quality assurance in Appreciate the need for quality assurance in radiotherapy treatment planningradiotherapy treatment planning



Overall SummaryOverall Summary

Treatment planning is the most important Treatment planning is the most important step towards radiotherapy for individual step towards radiotherapy for individual patients - as such it is essential for patient patients - as such it is essential for patient protection as outlined in BSSprotection as outlined in BSS

Treatment planning is growing more complex Treatment planning is growing more complex and time consumingand time consuming

Understanding of the process is essentialUnderstanding of the process is essential QA of all aspects is essentialQA of all aspects is essential

Any questions?Any questions?

Question:Question:

Please label and discuss the following processes in Please label and discuss the following processes in external beam radiotherapy treatment. external beam radiotherapy treatment.



Question:Question:Patient

Treatment unit

Diagnostic tools

Treatmentplanning

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