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 6: Brachytherapy Learning objectives: Upon completion of this lesson, the students will be able to: To be familiar with typical radioactive sources used in cancer treatment To be aware of different implant types and techniques To appreciate the implications of life implants vs manual and remote afterloading To understand the differences between low and high dose rate brachytherapy equipment To be familiar with some special current implant techniques (prostate seed implants, endovascular brachytherapy) Activity: 2 lectures Duration: 4 hours Materials and equipment needed: Slides, some demonstration material (needles, catheters, dummy sources, applicators, if possible) Part 6 Properties and safety of radiotherapy sources and equipment used for brachytherapy IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Part No...., Module No....Lesson No
Module title Brachytherapy The use of radioactive sources in close proximity to the target area for radiotherapy X Ray of a gynaecological implant using an applicator loaded with 137-Cs sources Breast implant using radioactive 192-Ir wire Just two illustrations of brachytherapy - left an interstitial implant and right an intracavitary implant. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Brachytherapy overview
Part No...., Module No....Lesson No Module title Brachytherapy overview Brachytherapy uses encapsulated radioactive sources to deliver a high dose to tissues near the source brachys (Greek) = short (distance) Inverse square law determines most of the dose distribution The picture shows a radiograph of radium needles implanted in tissue. If this is explained the lecturer should point out that radium is chiefly of historical interest - it is not recommended to be used. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Brachytherapy Characterized by strong dose gradients Many different techniques and sources available Implants are highly customized for individual patients The figure illustrates the strong dose gradients around 6 dwell positions for a HDR 192-Ir source(from ICRU report 58) Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Brachytherapy Use of radioactive materials in direct contact with patients - more radiation safety issues than in external beam radiotherapy Less than 10% of radiotherapy patients are treated with brachytherapy Per patient treated the number of accidents in brachytherapy is considerably higher than in EBT In regards to the last bullet point, the lecturer can point out that due to the high customization of every brachytherapy case, accidents in brachytherapy typically affect only one patient, while in external beam radiotherapy many can be affected. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Objectives of part 6 To be familiar with typical radioactive sources used in cancer treatment To be aware of different implant types and techniques To appreciate the implications of life implants vs. manual and remote afterloading To understand the differences between low and high dose rate brachytherapy equipment To be familiar with some special current implant techniques (prostate seed implants, endovascular brachytherapy) Brachytherapy is a topic which lends itself to practical demonstrations and ‘show and tell’. The lecturer should bring as many items from the clinic as possible. Examples are: Dummy sources Catheters, needles Applicators Phantoms Inactive gold seeds Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Contents Lecture 1: Brachytherapy Sources and equipment Lecture 2: Brachytherapy techniques (including special techniques such as prostate seed implants and endovascular brachytherapy) The lecturer can point out that the order of the lectures is different from the previous part 5 on external beam radiotherapy. However, in brachytherapy, it is more appropriate to start with the radioactive sources in use and then discuss techniques. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Flow of brachytherapy information in the course
Part No...., Module No....Lesson No Module title Flow of brachytherapy information in the course Part 2: Physics Part 6: Brachytherapy (Description of techniques and equipment) Part 11: Good practice in brachytherapy (Information placed in context of BSS with emphasis on radiation protection) The lecturer can point out that this information flow is similar for external beam radiotherapy, however, parts 14 to 16 play a less important role. Parts 14 (Transport), 15 (Security of sources) and 16 (Discharge of patients): Additional and supporting information - most of it directly relevant for brachytherapy practice Part 6, lecture 1: Brachytherapy sources 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 6 Brachytherapy Lecture 1: Brachytherapy Sources and Equipment Part 6: Brachytherapy Lesson 1: Sources for brachytherapy Learning objectives: Upon completion of this lesson, the students will be able to: To understand the concept of ‘sealed’ source To know the most common isotopes used for brachytherapy To be familiar with general rules for source handling and testing To be aware of differences between permanent implants, low (LDR) and high dose rate (HDR) applications To understand the basic fundamentals of brachytherapy equipment design. Activity: lecture Duration: 2 hours IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Objectives To understand the concept of ‘sealed’ source To know the most common isotopes used for brachytherapy To be familiar with general rules for source handling and testing To be aware of differences between permanent implants, low (LDR) and high dose rate (HDR) applications To understand the basic fundamentals of brachytherapy equipment design Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Contents 1 Sealed sources 2 The ideal source for radiotherapy 3 Brachytherapy sources in use Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Henri Becquerel ( ) A slide which can be omitted or used to start the lecture on a historical note… Becquerel and his father had studied phosphorescence in uranium salts, among others. After learning about the discovery of X-rays by CW Roentgen in 1995, he looked for penetrating radiation, fortuitously beginning with uranium salts. He exposed his uranium salts to sunlight and placed them on wrapped, light-tight photographic plates. On February 24, 1896, he reported success. Then on March 1, he reported that exposure to sunlight was not necessary, a discovery that occurred because of a series of sunless days. During March and April, he found that even non-phosphorescent uranium salts emitted penetrating radiation, while other phosphorescent bodies did not. On May 18, Becquerel announced that uranium metal, the element itself, was the source of the rays Becquerel's discovery was the result of careful and persistent experimentation, just the right background, some good luck, and an ability to accept and follow up unexpected results. The real significance of Becquerel's discovery was not recognized for a few more years. The Curies coined the term radioactivity. Becquerel himself identified electrons in the radiation of radium and published the first evidence of a radioactive transformation. His early work opened the way to the new field of nuclear physics and led to applications in nuclear medicine, reactors and nuclear weapons. Henry Becquerel shared the Nobel Prize with the Curies in (adapted from American Physics Society) Discovered radioactivity in 1896 Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title 1. Sealed sources IAEA BSS glossary: “Radioactive material that is a) permanently sealed in a capsule or b) closely bound and in a solid form.” In other words: the activity is fixed to its carrier and contamination of the environment is not possible as long as the source is intact Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Sealed sources Have an activity which can be derived from a calibration certificate and the half life of the isotope (nothing is lost) MUST be checked for integrity regularly - a good means of doing this is by wipe tests Here the wipe test is only mentioned to support the notion that a sealed source must be tested for integrity. Sealed sources are only sealed as long as the integrity can be assured. More details on wipe tests in part 11. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Sealed and unsealed sources in radiotherapy
Part No...., Module No....Lesson No Module title Sealed and unsealed sources in radiotherapy Both are used to treat cancer Sealed sources are used for brachytherapy - they are discussed here Unsealed sources may be used for systemic treatments - they are discussed in more detail in the course on Nuclear Medicine Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Some examples for unsealed source radiotherapy
Part No...., Module No....Lesson No Module title Some examples for unsealed source radiotherapy 131-I for thyroid treatment 89-Sr and 153-Sm for treatment of bone metastasis 32-P for hematological cancers Just some examples to give participants a ‘flavor of unsealed source therapy. A good summary is given in Williams and Thwaites 1994. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Note All brachytherapy sources are of an activity which makes them of ‘regulatory concern’ Therefore, persons ordering, receiving, handling, storing and disposing them must have appropriate training and hold the appropriate license More on this in parts 14 and 15 of the course Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

2. The ideal source in brachytherapy
Part No...., Module No....Lesson No Module title 2. The ideal source in brachytherapy A question is used as starting point for this section - the lecturer can choose to answer it him/herself by showing the next slides or to spend some time with the participants to elicit ideas about: half life specific activity/size energy What do you think one would expect from and ideal brachytherapy source? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Clinical usefulness determined by
Part No...., Module No....Lesson No Module title Clinical usefulness determined by Half life = the time after which half of the original activity is still present in the source Specific activity = activity per gram of material. The higher the specific activity, the smaller a source of a particular activity can be made Radiation energy determines the range of radiation in tissue (AND the requirements for shielding) Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

The Ideal Brachytherapy source
Part No...., Module No....Lesson No Module title The Ideal Brachytherapy source Pure gamma emitter - betas or alphas are too short in range and result in very high doses to small volumes around the source Medium gamma energy high enough to treat the target with homogenous dose low enough to avoid normal tissues and reduce shielding requirements High specific activity suitable also for high dose rate applications small The lecturer can point out that there are some exceptions - eg for some endovascular brachytherapy application (discussed in the next lecture) one prefers beta emitter because of the lack of exposure to staff. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

The Ideal Brachytherapy source
Part No...., Module No....Lesson No Module title The Ideal Brachytherapy source Stable daughter product For temporary implants: long half life allows economical re-use of sources For permanent implants: medium half life The ideal source does not exist, however we can get close Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

3. Real brachytherapy Sources
A variety of source types and isotopes are currently in use They differ for different applications because of half life, size (specific activity) and radiation energy When deciding on a source one must also keep the shielding requirements in mind Part 6, lecture 1: Brachytherapy sources

Brachytherapy Sources
Part No...., Module No....Lesson No Module title Brachytherapy Sources Included in the handout slides... Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Brachytherapy source types (ICRU report 58)
Part No...., Module No....Lesson No Module title Brachytherapy source types (ICRU report 58) It is not necessary here to understand the design of all these sources - the emphasis is on variety and choice of the best source for a particular application. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Brachytherapy sources
Part No...., Module No....Lesson No Module title Brachytherapy sources The first isotope used clinically was radium around 1903 Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Brachytherapy sources
Part No...., Module No....Lesson No Module title Brachytherapy sources However, radium and radon have only historical importance - they should not be used in a modern radiotherapy department Because: wide energy spectrum leading to high dose close to the source and still high dose around the patient - shielding difficult Radon, the daughter product of radium, is a noble gas which is very difficult to contain - contamination risk The long half life means disposal is very difficult Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Popular sources: 137-Cs “Cesium 137” Main substitute for radium Mostly used in gynecological applications Long half life of 30 years ---> decay correction necessary every 6 months Sources are expensive and must be replaced every 10 to 15 years The lecturer can point out that more details on applicators and LDR/HDR will follow Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Popular sources: 192-Ir “Iridium 192” Many different forms available Most important source for HDR applications Medium half life (75 days) - decay correction necessary for each treatment Needs to be replaced every 3 to 4 months to maintain effective activity and therefore an acceptable treatment time The last point applies equally to LDR and HDR applications Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Popular sources: 192-Ir “Iridium 192” High specific activity - therefore even high activity sources can be miniaturized essential for HDR applications A bit easier to shield than 137-Cs - because the gamma energies of 192-Ir range from 136 to 1062keV (effective energy around 350keV) Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title HDR 192-Ir source 10 Ci (370GBq) diameter of the order of 1mm length of the order of 10mm dual encapsulation attached to steel cable Typical dimensions only - there are different designs available for different HDR units. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

HDR source: anisotropy of dose
Part No...., Module No....Lesson No Module title HDR source: anisotropy of dose Typical results - the maximum dose rate is emitted about 45deg from central axis of the cylindrical source. The lecturer can point out the errors which are made if the source is assumed to be a point source with isotropic emission. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Popular sources: 125-I Very low energy - therefore shielding is easy and radiation from an implant is easily absorbed in the patient: permanent implants are possible Mostly used in the form of seeds More info on seeds and their use in the next lecture on special techniques. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Part 6, lecture 1: Brachytherapy sources
125-I seeds Many different designs Part 6, lecture 1: Brachytherapy sources

125-I seeds Design aims and features: sealed source non-toxic tissue compatible encapsulation isotropic dose distribution radio-opaque for localization Mentor Part 6, lecture 1: Brachytherapy sources

X Ray visibility of 125-I seeds
Part No...., Module No....Lesson No Module title X Ray visibility of 125-I seeds A typical AP X-ray view of a prostate seed implant Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

125-I seeds A different design: radio-opaque for X Ray visualization MRI compatibility desirable No contamination A source example Part 6, lecture 1: Brachytherapy sources

Symmetry of dose distribution
Part 6, lecture 1: Brachytherapy sources

Other isotopes used for seeds
Part No...., Module No....Lesson No Module title Other isotopes used for seeds Palladium 103 Half Life = 17 days - dose rate about 2.5 times larger than for 125-I Energy = 22 keV TVL lead = 0.05mm Gold 198 Half Life = 2.7 days - short enough to let activity decay in the patient Energy = 412 keV TVL lead = around 8mm The lecturer should point out that the TVL is only an approximation as it will vary with effective source size and the amount of attenuation required (eg for gold TVL1 (shield the first factor of 10) < TVL2) Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Brachytherapy Sources
Part No...., Module No....Lesson No Module title Brachytherapy Sources A variety of source shapes and forms: pellets = balls of approximately 3 mm diameter seeds = small cylinders about 1 mm diameter and 4 mm length needles = between 15 and 45 mm active length tubes = about 14 mm length, used for gynaecological implants hairpins = shaped as ‘hairpins’, approximately 60 mm active length wire = any length, usually customised in the hospital - inactive ends may be added HDR sources = high activity miniature cylinder sources approximately 1mm diameter, 10mm length Part of handout slides Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Source form examples Seeds (discussed before): small containers for activity usually 125-I, 103-Pd or 198-Au for permanent implant such as prostate cancer Needles and hairpins: for ‘life’ implants in the operating theatre - activity is directly introduced in the target region of the patient usually 192-Ir for temporary implants e.g. of the tongue Scale in mm Part 6, lecture 1: Brachytherapy sources

Module title Source form: 192-Ir wire Used for LDR interstitial implants Cut to appropriate length prior to implant to suit individual patient Cutting using manual technique or cutter... Shown are applicators for interstitial implants from Gammamed (strictly, they are for HDR units as shown here but the ones used for LDR wire implants look identical) The cutter station is shown on the next slide. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Source form 192-Ir wires 192-Ir wire: activity between 0.5 and 10mCi per cm used for interstitial implants low to medium dose rate can be cut from 50 cm long coils to the desired length for a particular patient Ir wires are commonly used for interstitial LDR implants. They are cut to the correct length using manual cutting or an automated wire cutter. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Source form example 192-Ir wire: activity between 0.5 and 10mCi per cm used for interstitial implants low to medium dose rate can be cut from 50 cm long coils to the desired length for a particular patient Cut wire is strictly speaking not a sealed source The ends of the wire are not strictly a sealed source - however, in practice they are classified as such. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

The requirements of BSS:
Part No...., Module No....Lesson No Module title The requirements of BSS: Appendix IV.8. “Registrants and licensees, in specific co-operation with suppliers, shall ensure that the following responsibilities be discharged, if applicable: (a) to provide a well designed and constructed source that: (i) provides for protection and safety in compliance with the Standards; (ii) meets engineering, performance and functional specifications; and (iii) meets quality norms commensurate with the protection and safety significance of components and systems; (b) to ensure that sources be tested to demonstrate compliance with the appropriate specifications; and (c) to make available information in a major world language acceptable to the user concerning the proper installation and use of the source and its associated risks.” This slide sums up the discussion of sources used in brachytherapy - more details on handling and storage in part 11 of the course. Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title Summary A wide variety of radioactive sources have been used for brachytherapy in many different physical forms The most common sources are 137-Cs, 192-Ir and 125-I Regular check of source integrity is essential to ensure the source can be classified as ‘sealed’ Let’s summarize the main subjects we did cover in this session. (List the main subjects covered and stress again the important features of the session) Part 6, lecture 1: Brachytherapy sources IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Module title References Johns H E and Cunningham J R 1983 The Physics of Radiology, 4th edition (Springfield: C Thomas) Khan F M 1994 The Physics of Radiation Therapy, 2nd edition (Williams & Wilkins, Baltimore) Williams J R and Thwaites D I 1993 Radiotherapy Physics in Practice (Oxford: Oxford University Press) Part 6, lecture 1: Brachytherapy sources 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 Key features are: small sources (seed) short half life (2.7 days) inert material Therefore, ideal for permanent implant photon energy 412keV Therefore not too difficult to shield Why would people use 198-Au for brachytherapy? IAEA Post Graduate Educational Course in Radiation Protection and Safe Use of Radiation Sources

Some clues for an answer
Key features of 198-Au are: small sources (seed) short half life (2.7 days) inert material photon energy 412keV Therefore, ideal for permanent implant Part 6, lecture 1: Brachytherapy sources

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