Radiation Protection in Radiotherapy

Radiation Protection in Radiotherapy
Part No...., Module No....Lesson No Module title IAEA Training Material on Radiation Protection in Radiotherapy Radiation Protection in Radiotherapy Part 10: Optimization in External Beam Radiotherapy Lesson 4: Treatment Planning Learning objectives: Upon completion of this lesson, the students will be able to: Understand the general principles of radiotherapy treatment planning Appreciate different dose calculation algorithms Understand the need for testing the treatment plan against a set of measurements Be able to apply the concepts of optimization of medical exposure throughout the treatment planning process Appreciate the need for quality assurance in radiotherapy treatment planning Activity: Lecture - 2 practical sessions: 1 Hand planning using isodose plots, 2 Monitor unit calculations Duration: 2 hours References: J van Dyk et al Commissioning and QA of treatment planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: J van Dyk et al, 1999 Computerised radiation treatment planning systems. In: Modern Technology of Radiation Oncology (Ed.: J Van Dyk) Chapter 8. Medical Physics Publishing, Wisconsin, ISBN , pp M Millar et al 1997 ACPSEM position paper. Australas. Phys. Eng. Sci. Med. 20 Supplement B Fraass et al 1998 AAPM Task Group 53: QA for clinical RT planning. Med. Phys. 25: Part 10 Good Practice including Radiation Protection in EBT Lecture 3 (cont.): Radiotherapy Treatment Planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Part No...., Module No....Lesson No
Module title C. Commissioning Complex procedure depending very much on equipment Protocols exist and should be followed Useful literature: J van Dyk et al Commissioning and QA of treatment planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: J van Dyk et al, 1999 Computerised radiation treatment planning systems. In: Modern Technology of Radiation Oncology (Ed.: J Van Dyk) Chapter 8. Medical Physics Publishing, Wisconsin, ISBN , pp The last section of lecture 3 in part 10 is mainly concerned with computerized treatment planning, however, many points are also relevant for manual treatment planning. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Acceptance testing and commissioning
Part No...., Module No....Lesson No Module title Acceptance testing and commissioning Acceptance testing: Check that the system conforms with specifications. Documentation of specifications either in the tender, in guidelines or manufacturers’ notes – may test against standard data (e.g. Miller et al. 1995, AAPM report 55) Subset of commissioning procedure Takes typically two weeks Commissioning: Getting the system ready for clinical use Takes typically several months for modern 3D system This is a difference which often overlooked by administrators - it can result in vastly different time estimates. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Some equipment required
Part No...., Module No....Lesson No Module title Some equipment required Scanning beam data acquisition system Calibrated ionization chamber Slab phantom including inhomogeneities Radiographic film Anthropomorphic phantom Ruler, spirit level The picture shows the set-up of a scanning water phantom Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Commissioning A. Non-dose related components B. Photon dose calculations C. Electron dose calculations (D. Brachytherapy - covered in part 11) E. Data transfer F. Special procedures These are different aspects of the commissioning of computerised treatment planning - the lecture follows this outline... Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title A. Non-dose components Image input Geometry and scaling of Digitizer, Scans Output Text information Anatomical structure information CT numbers Structures (outlining tools, non-axial reconstruction, “capping”,…) The ruler illustrates the need for quantitative geometric information Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Electron and photon beams
Part No...., Module No....Lesson No Module title Electron and photon beams Description (machine, modality, energy) Geometry (Gantry, collimator, table, arcs) Field definition (Collimator, trays, MLC, applicators, …) Beam modifiers (Wedges, dynamic wedges, compensators, bolus,…) Normalization This should all be familiar to the participants from the previous section of the lecture. The next slide is a reminder which is currently hidden. The lecturer should point out that the planning system (and any system which allows manual calculation of dose) must ‘know’ all this information Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Hidden slide Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

B. Photon calculation tests
Part No...., Module No....Lesson No Module title B. Photon calculation tests Point doses TAR, TPR, PDD, PSF Square, rectangular and irregular fields Inverse square law Attenuation factors (trays, wedges,…) Output factors Machine settings The first test is equally applicable to computerized treatment planning systems and hand planning. Machine settings include what gantry angles and field sizes are allowed, what wedges fit where and what set-up requirements there may be. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Photon calculation tests (cont.)
Part No...., Module No....Lesson No Module title Photon calculation tests (cont.) Dose distribution Homogenous Profiles (open and wedged) SSD/SAD Contour correction Blocks, MLC, asymmetric jaws Multiple beams Arcs Off axis (open and wedged) Collimator/couch rotation PTW waterphantom All these tests can be performed in the water phantom shown... Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Photon calculation tests (cont.)
Part No...., Module No....Lesson No Module title Photon calculation tests (cont.) Dose distribution Inhomogeneous Slab geometry Other geometries Anthropomorphic phantom In vivo dosimetry at least for the first patients Following the incident in Panama, the IAEA recommends a largely extended in vivo dosimetry program to be implemented Illustrated is a CIRS phantom In vivo dosimetry is discussed in more detail in the next lecture in part 10. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

C. Electron calculation
Part No...., Module No....Lesson No Module title C. Electron calculation Similar to photons, however, additional: Bremsstrahlung tail Small field sizes require special consideration Inhomogeneity has more impact It is possible to use reference data for comparison (Shui et al “Verification data for electron beam dose algorithms” Med. Phys. 19: ) Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title E. Data transfer Pixel values, CT numbers Missing lines Patient/scan information Orientation Distortion, magnification In a computerized world every step must be verified. For example, there are many conventions for patient orientation available - it must be ensured that a lesion on the left side of the brain is also represented on the left side in the data used for planning… (in general it is not easy to tell which side is which in a brain scan - are we looking at the patient from the head or the toes?) All needs verification!!! Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title F. Special procedures Junctions Electron abutting Stereotactic procedures Small field procedures (e.g. for eye treatment) IMRT TBI, TBSI Intraoperative radiotherapy This is just a summary - it would be beyond the scope of the course to provide more details on any of these. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Sources of uncertainty
Part No...., Module No....Lesson No Module title Sources of uncertainty Patient localization Imaging (resolution, distortions,…) Definition of anatomy (outlines,…) Beam geometry Dose calculation Dose display and plan evaluation Plan implementation This is an important slide - it summarizes the uncertainties which will affect the realization of a treatment plan in practice. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Typical accuracy required (examples)
Part No...., Module No....Lesson No Module title Typical accuracy required (examples) Square field CAX: 1% MLC penumbra: 3% Wedge outer beam: 5% Buildup-region: 30% 3D inhomogeneity CAX: 5% From AAPM TG53 Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Typical accuracy required (examples)
Part No...., Module No....Lesson No Module title Typical accuracy required (examples) Square field CAX: 1% MLC penumbra: 3% Wedge outer beam: 5% Buildup-region: 30% 3D inhomogeneity CAX: 5% Note: Uncertainties have two components: Dose (given in %) Location (given in mm) This is an important point: In regions where the dose is relatively homogenous (not much change of dose in the area of interest) on has to look primarily to the uncertainty in dose calculation. In regions of strong dose gradients this is not possible as the dose changes very rapidly and a small misplacement results in a large change in dose. Here it is more appropriate to characterize the dose calculation algorithm in terms of distance to agreement. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Time and staff requirements for commissioning (J Van Dyk 1999)
Part No...., Module No....Lesson No Module title Time and staff requirements for commissioning (J Van Dyk 1999) Photon beam: 4-7 days Electron beam: 3-5 days Brachytherapy: 1 day per source type Monitor unit calculation: 0.3 days per beam Important information for administrators - a new treatment planning system will not be available for clinical use a couple of days after installation. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Some ‘tricky’ issues Dose Volume Histograms - watch sampling, grid, volume determination, normalization (1% volume represents still > 10E7 cells!) Biological parameters - Tumour Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) depend on the model used and the parameters which are available. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Commissioning summary
Part No...., Module No....Lesson No Module title Commissioning summary Probably the most complex task for RT physicists - takes considerable time and training Partial commissioning needed for system upgrades and modification Documentation and hardcopy data must be included Training is essential and courses are available Independent check highly recommended Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Quick Question: What ‘commissioning’ needs to be done for a hand calculation method of treatment times for a superficial X Ray treatment unit? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Superficial beam HVL Percentage depth dose (may be look up table) Normalization point (typically the surface) Scatter (typically back scatter) factor Applicator and/or cone factor Timer accuracy On/off effect Other effects which may affect dose (e.g. electron contamination) Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Quality Assurance of a treatment planning system
Part No...., Module No....Lesson No Module title Quality Assurance of a treatment planning system QA is typically a subset of commissioning tests Protocols: As for commissioning and: M Millar et al ACPSEM position paper. Australas. Phys. Eng. Sci. Med. 20 Supplement B Fraas et al AAPM Task Group 53: QA for clinical RT planning. Med. Phys. 25: Other aspects of QA are covered in part 12 of the course. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Aspects of QA (compare also part 12 of the course)
Part No...., Module No....Lesson No Module title Aspects of QA (compare also part 12 of the course) Training - qualified staff Checks against a benchmark - reproducibility Treatment verification QA administration Communication Documentation Awareness of procedures required Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Quality Assurance This slide is included in three lectures of the course - some repetition is useful and it helps participants to feel familiar within the course. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Quality Assurance Hand calculation of treatment time Check prescription Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Frequency of tests for planning (and suggested acceptance criteria)
Part No...., Module No....Lesson No Module title Frequency of tests for planning (and suggested acceptance criteria) Commissioning and significant upgrades See above Annual: MU calculation (2%) Reference plan set (2% or 2mm) Scaling/geometry input/output devices (1mm) Monthly Check sum Some reference test sets This slide preempts some of the discussions of part 12 of the course. However, it was felt that it would be beneficial for participants to discuss QA of treatment planning close to the introduction of the planning systems themselves. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Frequency of tests (cont.)
Part No...., Module No....Lesson No Module title Frequency of tests (cont.) Weekly Input/output devices Each time system is turned on Check sum (no change) Each plan CT transfer - orientation? Monitor units - independent check Verify input parameters (field size, energy, etc.) Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Treatment planning QA summary
Part No...., Module No....Lesson No Module title Treatment planning QA summary Training most essential Staying alert is part of QA Documentation and reporting necessary Treatment verification in vivo can play an important role The last point should be seen in the context of the material presented in the 4th lecture of part 10 Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Quick Question: How much time should be spent on treatment planning QC? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Staff and time requirements (source J. Van Dyk et al. 1999)
Part No...., Module No....Lesson No Module title Staff and time requirements (source J. Van Dyk et al. 1999) Reproducibility tests/QC: 1 week per year In vivo dosimetry: about 1 hour per patient - aim for about 10% of patients Manual check of plans and monitor units: 20 minutes per plan Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

QA in treatment planning
The planning system Plan of a patient QA of the system QA of the plan Part 10, lecture 3 (cont.): Radiotherapy treatment planning

Module title QC of treatment plans Treatment plan: Documentation of treatment set-up, machine parameters, calculation details, dose distribution, patient information, record and verify data Consists typically of: Treatment sheet Isodose plan Record and Verify entry Reference films (simulator, DRR) This is a different aspect than the QA of planning systems - the QA here is directed towards the treatment plan of an individual patient. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Part 10, lecture 3 (cont.): Radiotherapy treatment planning
QC of treatment plans Check plan for each patient prior to commencement of treatment Plan must be Complete from prescription to set-up information and dose delivery advise Understandable by colleagues Document treatment for future use Part 10, lecture 3 (cont.): Radiotherapy treatment planning

Part 10, lecture 3 (cont.): Radiotherapy treatment planning
Who should do it? Treatment sheet checking should involve senior staff It is an advantage if different professions can be involved in the process Reports must go to clinicians and the relevant QA committee Part 10, lecture 3 (cont.): Radiotherapy treatment planning

Example for physics treatment sheet checking procedure
Part No...., Module No....Lesson No Module title Example for physics treatment sheet checking procedure Check prescription (energy/dose/fractionation is everything signed ?) 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. Check normalisation value (Plan or data sheets). Check outline, separation and prescription depth. 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 ? 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? Electrons only: … Photons only: … Check shadow tray factor, wedge factor. Are any other attenuation factors required (e.g. couch, headrest, table tray...) ? Check inverse square law factor (in electron treatments: is the virtual FSD appropriate?) Calculate monitor units. Is time entry ok ? Check if critical organ (e.g. spinal cord, lens, scrotum) dose or hot spot dose is required. If so, is it calculated correctly ? Suggest in vivo dosimetry measurements if appropriate. Sign calculation sheet (if everything is ok). Compare results on calculation page with entries in treatment log. Check diagram and/or set up description: is there anything else worth to consider ? Sign top of treatment sheet (specify what parts where checked if not all fields were checked). Contact planning staff if required. Sign off physics log book. This slide is too small to be read (see slides for bigger text). The text could be handed out to participants. However, it may be better to just use this to emphasize that: this is a complex procedure it must be developed locally documentation is essential The next slide highlights just three points which should not be overlooked. Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Example for physics treatment sheet checking procedure
Part No...., Module No....Lesson No Module title Example for physics treatment sheet checking procedure Check prescription (energy/dose/fractionation is everything signed ?) 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. Check normalisation value (Plan or data sheets). Check outline, separation and prescription depth. 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 ? The key issues are: Communication and Documentation Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Example for physics treatment sheet checking procedure (cont.)
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? Electrons only: … Photons only: … Check shadow tray factor, wedge factor. Are any other attenuation factors required (e.g. couch, headrest, table tray...) ? Check inverse square law factor (in electron treatments: is the virtual FSD appropriate?) Calculate monitor units. Is time entry ok ? Check if critical organ (e.g. spinal cord, lens, scrotum) dose or hot spot dose is required. If so, is it calculated correctly ? Part 10, lecture 3 (cont.): Radiotherapy treatment planning

Example for physics treatment sheet checking procedure (cont.)
Part No...., Module No....Lesson No Module title Example for physics treatment sheet checking procedure (cont.) Suggest in vivo dosimetry measurements if appropriate. Sign calculation sheet (if everything is ok). Compare results on calculation page with entries in treatment log. Check diagram and/or set up description: is there anything else worth to consider ? Sign top of treatment sheet (specify what parts where checked if not all fields were checked). Contact planning staff if required. Sign off physics log book. The key issues are: Communication and Documentation Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Treatment plan QA summary
Part No...., Module No....Lesson No Module title Treatment plan QA summary Essential part of departmental QA Part of patient records Multidisciplinary approach Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Quick Question: Again, the question can be omitted if deemed inappropriate, or if time is pressing. It is meant as a tool to get participants involved. The next slide provides some answers. What advantages has a multidisciplinary approach to QC of treatment plans? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Did we achieve the objectives?
Part No...., Module No....Lesson No Module title Did we achieve the objectives? Understand the general principles of radiotherapy treatment planning Appreciate different dose calculation algorithms Be able to apply the concepts of optimization of medical exposure throughout the treatment planning process Appreciate the need for quality assurance in radiotherapy treatment planning Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Overall Summary Treatment planning is the most important step towards radiotherapy for individual patients - as such it is essential for patient protection as outlined in BSS Treatment planning is growing more complex and time consuming Understanding of the process is essential QA of all aspects is essential Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Any questions?

Module title Question: The next slide can be printed out for the students with its notes. The first process is already described. The participants shall discuss and label the additional processes. Important keywords are: 2: Electronic data transfer, digitisation of patient outlines, ensuring geometry, placement of beams 3: Patient outlines, immobilisation devices, external markers 4: Patient positioning, immobilisation 5: Data transfer (including beam modifiers, blocks, MLC), verification images (DRRs) 6: Simulator images Please label and discuss the following processes in external beam radiotherapy treatment. IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Question: Diagnostic tools 1 Patient 2 4 6 3 1: It is essential to align the patient during any diagnostic procedure in a way which allows to reference the target anatomy to external landmarks. The latter may be bony landmarks or artificial marks like tattoos. In any case the procedure should allow the placement of external beams without repeating the diagnostic procedure. An important part of this is to perform the diagnostic procedure in the same patient position as the treatment. 2: 3: 4: 5: 5 Treatment planning Treatment unit Part 10, lecture 3 (cont.): Radiotherapy treatment planning IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Radiation Protection in Radiotherapy

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