Radiation Protection in Radiotherapy

Radiation Protection inRadiotherapyPart 10Good Practice including Radiation Protection in EBTLecture 3 (cont.): Radiotherapy Treatment PlanningIAEA Training Material on Radiation Protection in Radiotherapy

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

Radiation Protection in Radiotherapy

C. CommissioningComplex procedure depending very much on equipmentProtocols exist and should be followedUseful literature:J van Dyk et al. 1993 Commissioning and QA of treatment planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: 261-273J 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 0-944838-38-3, pp. 231-286.

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

Radiation Protection in Radiotherapy

Acceptance testing and commissioningAcceptance 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 procedureTakes typically two weeks

Commissioning: Getting the system ready for clinical useTakes typically several months for modern 3D system

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

Radiation Protection in Radiotherapy

Some equipment requiredScanning beam data acquisition systemCalibrated ionization chamberSlab phantom including inhomogeneitiesRadiographic filmAnthropomorphic phantomRuler, spirit level

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

Radiation Protection in Radiotherapy

CommissioningA. Non-dose related componentsB. Photon dose calculationsC. Electron dose calculations(D. Brachytherapy - covered in part 11)E. Data transferF. Special procedures

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

Radiation Protection in Radiotherapy

A. Non-dose componentsImage inputGeometry and scaling of Digitizer,ScansOutputText informationAnatomical structure informationCT numbersStructures (outlining tools, non-axial reconstruction, capping,)

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

Radiation Protection in Radiotherapy

Electron and photon beamsDescription (machine, modality, energy)Geometry (Gantry, collimator, table, arcs)Field definition (Collimator, trays, MLC, applicators, )Beam modifiers (Wedges, dynamic wedges, compensators, bolus,)Normalization

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

Radiation Protection in Radiotherapy

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

Radiation Protection in Radiotherapy

B. Photon calculation testsPoint dosesTAR, TPR, PDD, PSFSquare, rectangular and irregular fieldsInverse square lawAttenuation factors (trays, wedges,)Output factorsMachine settings

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

Radiation Protection in Radiotherapy

Photon calculation tests (cont.)Dose distributionHomogenousProfiles (open and wedged)SSD/SADContour correctionBlocks, MLC, asymmetric jawsMultiple beamsArcsOff axis (open and wedged)Collimator/couch rotationPTW waterphantom

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

Radiation Protection in Radiotherapy

Photon calculation tests (cont.)Dose distributionInhomogeneousSlab geometryOther geometriesAnthropomorphic phantomIn vivo dosimetry at least for the first patientsFollowing the incident in Panama, the IAEA recommends a largely extended in vivo dosimetry program to be implemented

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

Radiation Protection in Radiotherapy

C. Electron calculationSimilar to photons, however, additional:Bremsstrahlung tailSmall field sizes require special considerationInhomogeneity has more impactIt is possible to use reference data for comparison (Shui et al. 1992 Verification data for electron beam dose algorithms Med. Phys. 19: 623-636)

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

Radiation Protection in Radiotherapy

E. Data transferPixel values, CT numbersMissing linesPatient/scan informationOrientationDistortion, magnificationAll needs verification!!!

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

Radiation Protection in Radiotherapy

F. Special proceduresJunctions Electron abuttingStereotactic proceduresSmall field procedures (e.g. for eye treatment)IMRTTBI, TBSIIntraoperative radiotherapy

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

Radiation Protection in Radiotherapy

Sources of uncertaintyPatient localization Imaging (resolution, distortions,)Definition of anatomy (outlines,)Beam geometryDose calculationDose display and plan evaluationPlan implementation

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

Radiation Protection in Radiotherapy

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

Radiation Protection in Radiotherapy

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)

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

Radiation Protection in Radiotherapy

Time and staff requirements for commissioning (J Van Dyk 1999)Photon beam: 4-7 daysElectron beam: 3-5 daysBrachytherapy: 1 day per source typeMonitor unit calculation: 0.3 days per beam

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

Radiation Protection in Radiotherapy

Some tricky issuesDose 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

Radiation Protection in Radiotherapy

Commissioning summaryProbably the most complex task for RT physicists - takes considerable time and trainingPartial commissioning needed for system upgrades and modificationDocumentation and hardcopy data must be includedTraining is essential and courses are availableIndependent check highly recommended

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

Quick Question:What commissioning needs to be done for a hand calculation method of treatment times for a superficial X Ray treatment unit?

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

Radiation Protection in Radiotherapy

Superficial beamHVLPercentage depth dose (may be look up table)Normalization point (typically the surface)Scatter (typically back scatter) factorApplicator and/or cone factorTimer accuracyOn/off effectOther effects which may affect dose (e.g. electron contamination)

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

Radiation Protection in Radiotherapy

Quality Assurance of a treatment planning systemQA is typically a subset of commissioning testsProtocols:As for commissioning and:M Millar et al. 1997 ACPSEM position paper. Australas. Phys. Eng. Sci. Med. 20 SupplementB Fraas et al. 1998 AAPM Task Group 53: QA for clinical RT planning. Med. Phys. 25: 1773-1829

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

Radiation Protection in Radiotherapy

Aspects of QA (compare also part 12 of the course)Training - qualified staffChecks against a benchmark - reproducibilityTreatment verificationQA administrationCommunicationDocumentationAwareness of procedures required

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

Radiation Protection in Radiotherapy

Quality Assurance

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

Radiation Protection in Radiotherapy

Quality AssuranceCheck prescriptionHand calculation of treatment time

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

Radiation Protection in Radiotherapy

Frequency of tests for planning (and suggested acceptance criteria)Commissioning and significant upgradesSee aboveAnnual: MU calculation (2%)Reference plan set (2% or 2mm)Scaling/geometry input/output devices (1mm)MonthlyCheck sumSome reference test sets

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

Radiation Protection in Radiotherapy

Frequency of tests (cont.)WeeklyInput/output devicesEach time system is turned onCheck sum (no change)Each planCT transfer - orientation?Monitor units - independent checkVerify input parameters (field size, energy, etc.)

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

Radiation Protection in Radiotherapy

Treatment planning QA summaryTraining most essentialStaying alert is part of QADocumentation and reporting necessaryTreatment verification in vivo can play an important role

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

Quick Question:How much time should be spent on treatment planning QC?

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

Radiation Protection in Radiotherapy

Staff and time requirements (source J. Van Dyk et al. 1999)Reproducibility tests/QC: 1 week per yearIn vivo dosimetry: about 1 hour per patient - aim for about 10% of patientsManual check of plans and monitor units: 20 minutes per plan

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

Radiation Protection in Radiotherapy

QA in treatment planningThe planning systemQA of the systemPlan of a patientQA of the plan

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

Radiation Protection in Radiotherapy

QC of treatment plansTreatment plan: Documentation oftreatment set-up,machine parameters,calculation details,dose distribution,patient information,record and verify dataConsists typically of:Treatment sheetIsodose planRecord and Verify entryReference films (simulator, DRR)

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

Radiation Protection in Radiotherapy

QC of treatment plansCheck plan for each patient prior to commencement of treatmentPlan must beComplete from prescription to set-up information and dose delivery adviseUnderstandable by colleaguesDocument treatment for future use

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

Radiation Protection in Radiotherapy

Who should do it?Treatment sheet checking should involve senior staffIt is an advantage if different professions can be involved in the processReports must go to clinicians and the relevant QA committee

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

Radiation Protection in Radiotherapy

Example for physics treatment sheet checking procedureCheck 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.

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

Radiation Protection in Radiotherapy

Example for physics treatment sheet checking procedureCheck 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 ?

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

Radiation Protection in Radiotherapy

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

Radiation Protection in Radiotherapy

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.

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

Radiation Protection in Radiotherapy

Treatment plan QA summaryEssential part of departmental QAPart of patient recordsMultidisciplinary approach

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

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

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

Radiation Protection in Radiotherapy

Did we achieve the objectives?Understand the general principles of radiotherapy treatment planningAppreciate different dose calculation algorithmsBe able to apply the concepts of optimization of medical exposure throughout the treatment planning processAppreciate the need for quality assurance in radiotherapy treatment planning

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

Radiation Protection in Radiotherapy

Overall SummaryTreatment planning is the most important step towards radiotherapy for individual patients - as such it is essential for patient protection as outlined in BSSTreatment planning is growing more complex and time consumingUnderstanding of the process is essentialQA of all aspects is essential

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

Any questions?

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

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

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

Radiation Protection in Radiotherapy

Question:PatientTreatment unitDiagnostic toolsTreatmentplanning135426

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

Part No...., Module No....Lesson NoPart 10: Optimization in External Beam RadiotherapyLesson 4: Treatment PlanningLearning objectives: Upon completion of this lesson, the students will be able to:Understand the general principles of radiotherapy treatment planningAppreciate different dose calculation algorithmsUnderstand 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 processAppreciate the need for quality assurance in radiotherapy treatment planningActivity: Lecture - 2 practical sessions: 1 Hand planning using isodose plots, 2 Monitor unit calculations Duration: 2 hoursReferences:J van Dyk et al. 1993 Commissioning and QA of treatment planning computers. Int. J. Radiat. Oncol. Biol. Phys. 26: 261-273J 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 0-944838-38-3, pp. 231-286.M Millar et al 1997 ACPSEM position paper. Australas. Phys. Eng. Sci. Med. 20 SupplementB Fraass et al 1998 AAPM Task Group 53: QA for clinical RT planning. Med. Phys. 25: 1773-1829IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe 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. IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis is a difference which often overlooked by administrators - it can result in vastly different time estimates.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe picture shows the set-up of a scanning water phantomIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThese are different aspects of the commissioning of computerised treatment planning - the lecture follows this outline...IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe ruler illustrates the need for quantitative geometric informationIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis 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 informationIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoHidden slideIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe 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.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoAll these tests can be performed in the water phantom shown...IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIllustrated is a CIRS phantomIn vivo dosimetry is discussed in more detail in the next lecture in part 10.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIn 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?)IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis is just a summary - it would be beyond the scope of the course to provide more details on any of these.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis is an important slide - it summarizes the uncertainties which will affect the realization of a treatment plan in practice. IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis 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.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoImportant information for administrators - a new treatment planning system will not be available for clinical use a couple of days after installation.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoOther aspects of QA are covered in part 12 of the course.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis slide is included in three lectures of the course - some repetition is useful and it helps participants to feel familiar within the course.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis 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.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe last point should be seen in the context of the material presented in the 4th lecture of part 10IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis is a different aspect than the QA of planning systems - the QA here is directed towards the treatment plan of an individual patient.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThis slide is too small to be read (see slides 37-39 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 procedureit must be developed locallydocumentation is essential

The next slide highlights just three points which should not be overlooked.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe key issues are:Communication and DocumentationIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe key issues are:Communication and Documentation

IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoAgain, 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.IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson NoThe 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 beams3: Patient outlines, immobilisation devices, external markers4: Patient positioning, immobilisation5: Data transfer (including beam modifiers, blocks, MLC), verification images (DRRs)6: Simulator imagesIAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation SourcesPart No...., Module No....Lesson No1: 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:

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