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 5 Properties and safety of radiotherapy sources and equipment used for external beam radiotherapy Part 5: External beam radiotherapy - equipment Lesson 1:Techniques Learning objectives: Upon completion of this lesson, the students will be able to: To become familiar with different radiation types used for external beam radiotherapy To understand the function of different equipment used for EBT delivery To appreciate the implications of different treatment units and their design To be familiar with auxilliary equipment required and used for EBT To understand the measures used in this equipment to ensure radiation safety Activity: lecture and site visit Duration: Part 5: 6 hours, lecture 1: 2 hours Materials and equipment needed: References: Johns H E; Cunningham J R. The physics of radiology. Springfield: CC Thomas; 1983. Karzmark, C, Nunan C and Tanabe E. Medical electron accelerators. McGraw Hill, New York, 1993. Khan F. The physics of radiation therapy. 2nd edition. Baltimore: Williams & Wilkins; 1994. Metcalfe P.; Kron T.; Hoban P. The physics of radiotherapy X-rays from linear accelerators. Madison: Medical Physics Publishing; 1997. VanDyk, J. Modern Technology of Radiation Oncology (Ed.: J Van Dyk) Medical Physics Publishing, Wisconsin 1999, ISBN Williams J; Thwaites D. Radiotherapy Physics. Oxford: Oxford University Press; 1993. IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

IAEA Safety Series 120, Safety Fundamentals (1996)
Part No...., Module No....Lesson No Module title IAEA Safety Series 120, Safety Fundamentals (1996) Definition to avoid confusion Source: “Anything that may cause radiation exposure… an X-ray unit may be a source …” IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

External Beam Radiotherapy
Part No...., Module No....Lesson No Module title External Beam Radiotherapy Beam 2 Beam 3 Beam 1 This slide illustrates the basic principle - the radiation delivery is from outside of the patient. The most important features of this procedure are given in the next slide. tumour patient Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

External Beam Therapy (EBT)
Part No...., Module No....Lesson No Module title External Beam Therapy (EBT) Non-invasive Target localization important and beam placement may be tricky Usually multiple beams to place target in the focus of all beams Multiple non- coplanar beams The picture can be used by the lecturer to introduce participants to the increasing complexity of EBT when adding more beams. In practice most departments would use multiple co-planar beams because of the near-cylindrical symmetry of the human body. Single beam Three coplanar beam patient Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

External Beam Radiotherapy
Part No...., Module No....Lesson No Module title External Beam Radiotherapy More than 90% of all radiotherapy patients are treated using EBT Most of these are treated using X Rays ranging from 20keV to 20MeV in peak-energy Other EBT treatment options include telecurie units (60-Co and 137-Cs), electrons from linear accelerators and accelerators for heavy charged particles such as protons The term telecurie units should be introduced by the lecturer here. It is used to describe all external beam treatment units employing radioactive sources. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Part 5, lecture 1: Radiation types and techniques
Objectives To become familiar with different radiation types used for external beam radiotherapy To understand the function of different equipment used for EBT delivery To appreciate the implications of different treatment units and their design To be familiar with auxiliary equipment required and used for EBT To understand the measures used in this equipment to ensure radiation safety Part 5, lecture 1: Radiation types and techniques

Part No...., Module No....Lesson No
Module title Contents Lecture 1: Radiation types and techniques Lecture 2: Equipment and safe design Even the split in tow lectures leaves both lectures relatively long and the second will be split in several subsections. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

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 5 External Beam RT Lecture 1: Radiation types and techniques Part 5: Introduction Lesson 1: Radiation types and techniques Learning objectives: Upon completion of this lesson, the students will be able to: To be familiar with different radiation types used in EBT To appreciate the technical needs to make these radiation types applicable to radiotherapy To understand common external beam radiotherapy techniques Activity: lecture- if available a video clip can be shown. Many radiotherapy departments have excellent introductory videos for patients. Watching a video of this nature would be highly beneficial (and helpful for the work on the question at the end of the lecture) Duration: 1 hour Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session) IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Objectives To be familiar with different radiation types used in EBT To appreciate the technical needs to make these radiation types applicable to radiotherapy To understand common external beam radiotherapy techniques Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Contents 1. External Beam Radiotherapy process 2. Radiation qualities in use 3. Delivery techniques 4. Prescription and reporting 5. Special procedures Points 2 and 3 belong together - the discussion will combine radiation quality, how it relates to radiotherapy problems and common techniques. This will be dealt with in order of different radiation qualities (see slide Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title 1. EBT process This should be familiar to participants from part 1 of the course. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

EBT process: Use of radiation
Part No...., Module No....Lesson No Module title EBT process: Use of radiation These steps are of immediate importance for radiation protection, however, also the others will determine the outcome. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Note on the role of diagnosis
The responsibility of clinicians Without appropriate diagnosis the justification of the treatment is doubtful Diagnosis is important for target design and the dose required for cure or palliation Part 5, lecture 1: Radiation types and techniques

Note on the role of simulation
Simulator is often used twice in the radiotherapy process Patient data acquisition - target localization, contours, outlines Verification - can the plan be put into practice? Acquisition of reference images for verification Simulator may be replaced by other diagnostic equipment or virtual simulation Part 5, lecture 1: Radiation types and techniques

Module title Simulator However, some functions can be replaced by other diagnostic X Ray units provided the location of the X Ray field can be marked on the patient unambiguously Other functions (isocentricity) can then be mimicked on the treatment unit Important to mimic isocentric treatment environment This slide reflects the reality in many radiotherapy centres. It is important for the participants to realize that the course cannot prescribe what equipment is required. It will try to introduce functions, and suggest potential solutions. A good simulation session can be done using a diagnostic X-ray unit for target localization and a treatment unit for verification. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Virtual simulation All aspects of simulator work are performed on a 3D data set of the patient This requires high quality 3D CT data of the patient in treatment position Verification can be performed using digitally reconstructed radiographs (DRRs) This and the following slides introduces a technique which is currently finding its way into many radiotherapy practices in the developed world. As such the lecturer can choose to omit this and the next 4 slides. However, in practice, virtual simulation can be cheaper than buying a simulator if a CT scan of the patient is available. As such it may be of interest also for others in the future. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title CT Simulation (Thanks to ADAC) Marking the Patient already during CT This complex slide illustrates the ‘high form’ of virtual simulation. The patient undergoes a CT scan and the clinician identifies the target while the patient is still on the couch. The target localisation is then fed back to a movable laser system which will indicate on the patient where the centre of the target is. These points can be marked on the patient in situ and the beams positioned accordingly. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Virtual Simulation 3D Model of the patient and the Treatment Devices Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Digitally Reconstructed Radiographs as reference image for verification View and print DRRs for all planned fields: Improved confidence for planning and reference for verification DRR are an important part of the virtual simulation procedure - they constitute computer generated images which show what the planning system thinks a portal image should look like. As such DRRs can replace the simulator image as reference image. Again this technology requires a CT dataset for the patient and a complex treatment planning system. However, it allows potential cost-savings due to the lack of need for a simulator. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Note on the role of treatment planning
Part No...., Module No....Lesson No Module title Note on the role of treatment planning Links prescription to reality The ‘center piece’ of radiotherapy Becomes more and more sophisticated and complex Extensive discussion in part 10 Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. External beam radiotherapy (EBT) treatment approaches
Part No...., Module No....Lesson No Module title 2. External beam radiotherapy (EBT) treatment approaches Superficial X Rays Orthovoltage X Rays Telecurie units Megavoltage X Rays Electrons Heavy charged particles Others This slide also serves as roadmap for the main part of the lecture - it is structured following the different radiation types. The lecturer could already point out that megavoltage X-rays, 60-Co gammas and electrons produced by linear accelerators are by far the most important treatment modality. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

External beam radiotherapy (EBT) treatment approaches
Part No...., Module No....Lesson No Module title External beam radiotherapy (EBT) treatment approaches Superficial X Rays Orthovoltage X Rays Telecurie units Megavoltage X Rays Electrons Heavy charged particles Others 40 to 120kVp 150 to 400kVp 137-Cs and 60-Co Linear accelerators Protons from cyclotron, C, Ar, ... Neutrons, pions Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Photon percentage depth dose comparison for photon beams
Part No...., Module No....Lesson No Module title Photon percentage depth dose comparison for photon beams Superficial beam Orthovoltage beam Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Superficial radiotherapy
50 to 120kVp - similar to diagnostic X Ray qualities Low penetration Limited to skin lesions treated with single beam Typically small field sizes Applicators required to collimate beam on patient’s skin Short distance between X Ray focus and skin Part 5, lecture 1: Radiation types and techniques

Superficial radiotherapy
Part No...., Module No....Lesson No Module title Superficial radiotherapy The lecturer should point out the very short distance of 10cm from the target to the skin. Philips RT 100 Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Superficial radiotherapy issues
Part No...., Module No....Lesson No Module title Superficial radiotherapy issues Due to short FSD high output and large influence of inverse square law Calibration difficult (strong dose gradient, electron contamination) Dose determined by a timer - on/off effects must be considered Photon beams may be contaminated with electrons from the applicator The lecturer should particularly emphasize the first point. The strong dose gradients are due to FSDs of 10 to 25cm in practice. Calibration of beams is typically done at surface, therefore electron contamination from lead glass cones can be of concern. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Orthovoltage radiotherapy
Part No...., Module No....Lesson No Module title Orthovoltage radiotherapy kVp Penetration sufficient for palliative treatment of bone lesions relatively close to the surface (ribs, spinal cord) Largely replaced by other treatment modalities Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Orthovoltage Equipment (150 - 400 kVp)
Depth dose dramatically affected by the FSD FSD 6cm, HVL 6.8mm Cu FSD 30cm, HVL 4.4mm Cu Part 5, lecture 1: Radiation types and techniques

Orthovoltage patient set-up
Like for superficial irradiation units the beam is set-up with cones directly on the patient’s skin Part 5, lecture 1: Radiation types and techniques

Megavoltage radiotherapy
Part No...., Module No....Lesson No Module title Megavoltage radiotherapy 60-Cobalt (energy 1.25MeV) Linear accelerators (4 to 25MVp) Skin sparing in photon beams Typical focus to skin distance 80 to 100cm Isocentrically mounted The picture shows a VARIAN linac Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Photon percentage depth dose comparison
Part No...., Module No....Lesson No Module title Photon percentage depth dose comparison PHOTONS ELECTRONS The slide summarizes both linac and 60-Co megavoltage units. Only linacs can also produce electron beams. If time permits, the lecturer can use the depth dose characteristics and compare the location of a typical tumor or normal tissue in regards to depth. The next slide gives some impression. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Typical locations of tumor and normal tissues
Part No...., Module No....Lesson No Module title Typical locations of tumor and normal tissues PHOTONS ELECTRONS This is just an indication and others may be found easily Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Build-up effect Result of the forward direction of secondary electrons - they deposit energy down stream from the original interaction point Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Build-up effect Clinically important as all radiation beams in external radiotherapy go through the skin Is reduced in large field sizes and oblique incidence and when trays are placed in the beam Can be avoided by the use of bolus on the patient if skin or scar shall be treated The reduction of build-up effect in large fields and fields using trays is a result of additional electron contamination. The lecturer can point out the magnitude of the effect: 60-Co about 50%, full build-up at 1cm depth 6MV about 20%, full build-up at 1.5cm 18MV about 10% full build-up at 3.5cm. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Isocentric set-up Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Isocentric set-up Result of the large FSDs possible with modern equipment Places the tumour in the centre - multiple radiation beams are easily set-up to deliver radiation from many directions to the target Image from VARIAN webpage Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Common photon treatment techniques
Part No...., Module No....Lesson No Module title Common photon treatment techniques Two parallel opposed fields lung breast head and neck The following may be expanded on by participants and the lecturer following their own experience. The lecture is NOT meant to be a compendium of treatment techniques - it is merely an illustration. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Common photon treatment techniques
Part No...., Module No....Lesson No Module title Common photon treatment techniques Four field ‘box’ cervix prostate Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Isocentric or not? All the beam arrangements discussed so far can be set-up with a fixed distance (e.g. 80cm) to the patient’s skin or isocentrically with a fixed distance to the centre of the target. Advantages and disadvantages are subject of a practical exercise/discussion. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Photon beam modification
Part No...., Module No....Lesson No Module title Photon beam modification Blocks Wedges Compensators Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Shielding blocks Customized shielding block Beam shaping Conform the high dose region to the target Fixed blocks Customized blocks made from low melting alloy (LMA) Partially replaced now by Multi Leaf Collimator (MLC) Siemens MLC Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Physical wedge The picture shows a wedge and isodose lines. The higher dose is located where the thinner edge of the wedge is. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Wedges One dimensional dose modification Different realizations Now often a dynamic wedge The different realizations refer to different locations for the wedge: More on this in the next section and part 10 of the course. The dynamic wedge uses a moving collimator to create a one-dimensionally varied fluence map by closing more and more parts of the field. The area next to the stationary jaw (the left jaw in the illustration) will receive the highest dose and would be equivalent to the thin end of the wedge. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Use of wedges Wedged pair Three field techniques Isodose lines patient patient Typical isodose lines Part 5, lecture 1: Radiation types and techniques

Module title Compensators Physical compensators lead sheets brass blocks customized milling Intensity modulation multiple static fields arcs dynamic MLC The aim of all compensators is to modulate the photon fluence in different parts of the beam. This is a two dimensional map rather than a one dimensional one as in the case of the wedge. Similarly to the wedge there is also a physical version of compensators shown here and one created by moving jaws (or better the MLC) on a megavoltage photon unit. This is called Intensity Modulated Radiation Therapy (IMRT) and illustrated in the next slides. It is currently the topic of a lot of research and holds great promise for improved dose distributions in the target. Depending on the participants, the lecturer can decide to omit the following two slides. Similar information is also provided in the next lecture and in part 10 of the course. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Intensity modulation Can be shown to allow optimization of the dose distribution Make dose in the target homogenous Minimize dose outside the target Different techniques physical compensators intensity modulation using multileaf collimators Part 5, lecture 1: Radiation types and techniques

Module title Intensity Modulation MLC pattern 1 MLC pattern 2 Achieved using a Multi Leaf Collimator (MLC) The field shape can be altered either step-by-step or dynamically while dose is delivered MLC pattern 3 The lecturer can take participants through the right part of the slide step by step, adding up the fluence distribution in all three fields shown. In practice, there will be often more than 50 subfields or segments. Intensity map Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Dynamic treatment techniques
Part No...., Module No....Lesson No Module title Dynamic treatment techniques Arcs Dynamic wedge Dynamic MLC increasing complexity with increasing flexibility in dose delivery. Verification becomes essential patient Dynamic wedge has been described, Dynamic MLC is part of IMRT and the arc is illustrated here. All have in common the increased flexibility in dose delivery. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Electron radiotherapy
Part No...., Module No....Lesson No Module title Electron radiotherapy The slide illustrates the two most important features of electron beams Finite range Rapid dose fall off Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Characteristics of an electron beam
Part No...., Module No....Lesson No Module title Characteristics of an electron beam Rp dmax 50 10 20 30 40 60 70 80 90 100 1 2 3 4 5 6 7 8 9 11 12 Depth (cm) %DD R100 R50 Surface dose Therapeutic range x-ray component The slide introduces important parameters for electron beam dosimetry - it can be omitted in lectures for non-technical staff. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Electron beam isodoses (20MeV)
Part No...., Module No....Lesson No Module title Electron beam isodoses (20MeV) Watch dose increase (115%!) due to oblique incidence Watch ‘bulging’ of isodoses at depth This slide illustrates tow important issues when using electron beams clinically - both physicists and clinicians must be aware of these features when using electron radiation clinically. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Other issues with electron beams
Part No...., Module No....Lesson No Module title Other issues with electron beams Dose distribution significantly affected by surface contour changes - this must be considered when using bolus to shape dose distribution at depth. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Inhomogeneities affect the dose distribution
Part No...., Module No....Lesson No Module title Inhomogeneities affect the dose distribution Air cavity The lecturer can point out that these pictures were created using Monte Carlo Calculations, the most accurate way to predict dose distributions. A conventional commercial treatment planning system will typically show different isodoses which are often incorrect. Caution is necessary and a clinical radiotherapy physicist should be consulted if in doubt. Monte Carlo Calculations Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Use of electrons Skin lesions Scar boosting Avoidance of deep lying sensitive structures (e.g. spinal cord) All of the above are obvious from the properties of electron beams Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

More issues with the use of electrons for radiotherapy
Computer prediction of dose distribution more difficult Small fields difficult to predict Dosimetry somewhat more difficult than in photons due to strong dose gradients and variation of electron energy with depth Part 5, lecture 1: Radiation types and techniques

Module title Other radiation types Neutrons Complex radiobiology Complex interactions Potential advantages for hypoxic and radioresistant tumors Not widely used Protons - probably the most promising other radiation type Neutron radiotherapy would be beyond the scope of the present course - however, protons shall be discussed a bit more in depth in the following because proton RT has similarities with electron irradiation proton radiotherapy can be expected to grow in the next years Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Comparison to other radiation types
Part No...., Module No....Lesson No Module title Comparison to other radiation types The lecturer can use this slide to summarise photon and electron radiotherapy depth dose curves and introduce protons. The slide includes also 60-Co radiation. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Potential Advantage of Proton radiotherapy: dose sparing before and behind the target due to Bragg peak The spread out Bragg Peak is a summation of many beams with different energies which results in different depths for the Bragg Peak. Added with the correct weighting the resultant beam has a nearly flat plateau at depth. The small ripples are due to the individual Bragg peaks used. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title From these pictures it is clear that protons will result in less dose to normal tissues for the same tumour dose. The difference (yellow areas) will get smaller though for increasing number of beams and for deeper lying larger targets. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title X Rays versus protons The lecturer can point out the missing exit dose in the proton beam Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

4. Prescription and reporting
Part No...., Module No....Lesson No Module title 4. Prescription and reporting Prescription is the responsibility of individual clinicians, depending on the patient’s condition, equipment available, experience and training. The prescription should follow protocols which are established by professional organizations and modified and adopted by radiotherapy departments. The prescription must be informed - as far as possible - by clinical evidence Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Prescription and reporting
Part No...., Module No....Lesson No Module title Prescription and reporting Prescription may vary within reason depending on equipment available Reporting must be uniform - any adequately educated person must be able to understand what happened to the patient in case of: need for a different clinician to continue treatment re-treatment of the patient clinical trials potential litigation Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Recommendations by the ICRU
Part No...., Module No....Lesson No Module title Recommendations by the ICRU International Commission on Radiation Units and Measurements ICRU reports provide guidance on prescribing, recording and reporting These are tow important documents which all participants of the course must be aware of. Ideally, the lecturer should bring a copy of the reports with him/her. Participants should have access to them. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Target delineation ICRU report 50 This is a central slide for the prescription system of the ICRU - the definitions of the different volumes are provided in the following Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Definitions form ICRU 50 Gross Tumour Volume (GTV) = clinically demonstrated tumour Clinical Target Volume (CTV) = GTV + area at risk (e.g. potentially involved lymph nodes) The lecturer should point out that these definitions have indeed been widely adopted and form basis of most clinical trials and scientific publications. In order to understand these one must be familiar with the present definitions. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Definitions form ICRU 50 Planning Target Volume (PTV) = volume planned to be treated = CTV + margin for set-up uncertainties and potential of organ movement This is a crucial step in the prescription process - margins depend on the quality of the equipment used, the set-up uncertainties and the internal motion of organs. The lecturer can point out that the margins are not necessarily uniform. If an organ moved in a particular direction mostly (eg liver in sup inf with breathing) the margins may reflect this. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Strategies for margins
Margins are most important for clinical radiotherapy - they depend on: organ motion - internal margin patient set-up and beam alignment - external margin Margins can be non-uniform but should be three dimensional A reasonable way of thinking would be: “Choose margins so that the target is in the treated field at least 95% of the time” Part 5, lecture 1: Radiation types and techniques

Definitions form ICRU 50 Treated Volume = volume that receives dose considered adequate for clinical objective Irradiated volume = dose considered not negligible for normal tissues Part 5, lecture 1: Radiation types and techniques

Module title The concept of margins was expanded on by ICRU report 62 Internal margin = due to organ motion Set-up margin The two are often combined as independent uncertainties This is another complex but very important slide. The lecturer should take time to guide students through it. The addition of independent sources of uncertainty is done in quadrature as: Combined = sqrt(internal^2 + external^2) Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title 5. Special procedures Total body irradiation Total electron skin irradiation Stereotactic radiosurgery Many others could be thought of (eg mantle techniques for lymphoma treatment), however, the ones chosen here are most common and illustrate the most important points - depending on need and time requirements, the lecturer can add or delete procedures. Provided one knows what to do, magic they are not. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Total body irradiation (TBI)
Part No...., Module No....Lesson No Module title Total body irradiation (TBI) Target: Bone marrow Different techniques available 2 lateral fields at extended FSD AP and PA moving of patient through the beam Typically impossible to do a computerized treatment plan Need many measurements Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

TBI: one possible patient position
Part No...., Module No....Lesson No Module title TBI: one possible patient position Radiation field at >3m FSD; collimator rotated Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Issues with TBI In vivo dosimetry essential May need low dose rate treatment Shielding of critical organs (e.g. lung) and thin body parts may be required this can be only for parts of the treatment to achieve the best possible dose uniformity The last point can lead the lecturer to talk about intensity modulation again - often thin parts of the body (feet, head) are blocked for part of the treatment or a suitable attenuator is placed in the beam: This is similar to IMRT with MLC or compensator. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Total electron skin irradiation
Part No...., Module No....Lesson No Module title Total electron skin irradiation Treat all skin to very shallow depth Different techniques available 4 or 6 fields rotating patient Impossible to plan using a computer Requires many measurements for beam characterization Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Total Body Skin Irradiation
Part No...., Module No....Lesson No Module title Total Body Skin Irradiation Multiple electron fields at extended FSD Whole body skin as target Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Issues with TBSI Use low energy electrons (4 or 6MeV) Spoiler in front of patient improves dose distribution in vivo dosimetry required shielding of nails and eyes boost of some areas (e.g. under arms) may be required The spoiler is a thin sheet of perspex - its reduction of the effective energy of the electron beam must be taken into account. In vivo dosimetry is most usually done using TLDs Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Stereotactic procedures
Part No...., Module No....Lesson No Module title Stereotactic procedures Target usually brain lesions External head frame used to ensure accurate patient positioning Invasive or Re-locatable The key to these procedures is an external reference frame which can be attached to the patient. The reference frame can be visualized in CT scans and other diagnostic procedures (eg MRI, angiography) and guides the approach to the target. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Image registration Variety of systems Many frame attachments to allow for different diagnostic modalities (MRI, CT, angiography) Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Image registration CT scan MRI Leksell fiducial markers on both The Leksell system features a total of 9 marker rods, some of which are angled. This allows the determination of the sup/inf (cranio caudal) location from the location of the markers on the axial images. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Stereotactic procedures
Part No...., Module No....Lesson No Module title Stereotactic procedures Both systems MedTec Spatial accuracy around 1mm High dose single fraction (e.g. for arterio-venous malformations) = stereotactic radiosurgery using an invasively mounted head frame Multiple fractions for tumour treatment = stereotactic radiotherapy using a re-locatable head immobilisation The relocatable head frame is a combination of a personalized mask (‘shell”) and a bite block - in practice the spatial accuracy of the relocatable systems is somewhat less than the invasively mounted head frames which are screwed to the skull. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

EBT verification tools
Part No...., Module No....Lesson No Module title EBT verification tools Correct location portal films electronic portal imaging Correct dose phantom measurements in vivo dosimetry After talking a lot about high spatial accuracy, one also needs to mention verification: how do we know that we achieve what we think we do. This is discussed in more detail in section X - however, it should be mentioned already here. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

EBT verification tools
Part No...., Module No....Lesson No Module title EBT verification tools Correct location portal films electronic portal imaging Correct dose phantom measurements in vivo dosimetry Part 10 with some comments in second lecture part 5 (now) Parts 2 and 10 Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Summary A wide variety of radiation qualities are available for the optimization of radiotherapy for individual patients The choice depends on patient and availability of equipment Given adequate understanding of radiation properties and patient requirements many highly specialized procedures have been developed to address problems in radiotherapy Let’s summarize the main subjects we did cover in this session. Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Have we achieved the objectives?
Part No...., Module No....Lesson No Module title Have we achieved the objectives? To be familiar with different radiation types used in EBT To appreciate the technical needs to make these radiation types applicable to radiotherapy To understand common external beam radiotherapy techniques After a long lecture such as the present, it is worthwhile to check if the objectives were achieved - time for the participants to ask questions... Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Where to Get More Information
Part No...., Module No....Lesson No Module title Where to Get More Information Part 10 relates directly to this part References: Karzmark, C, Nunan C and Tanabe E. Medical electron accelerators. McGraw Hill, New York, Site visit of ... Lecturer to complete the site of the site visit... Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Any questions? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Question: The lecturer should first just ask the question and after five minutes change to the next slide which gives some suggestions for headings. The participants can then work for at least another 20 minutes to complete the table (may depend on the background of the participants). Please put together a table comparing electron and X Rays produced by linear accelerators IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

X Rays and electrons in EBT
Part No...., Module No....Lesson No Module title X Rays and electrons in EBT Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Acknowledgments John Drew, Westmead Hospital, Sydney Patricia Ostwald, Newcastle Mater Hospital Part 5, lecture 1: Radiation types and techniques IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Radiation Protection in Radiotherapy

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Radiation Protection in Radiotherapy

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Presentation on theme: "Radiation Protection in Radiotherapy"— Presentation transcript:

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