Radiation Protection in Radiotherapy

Radiation Protection in Radiotherapy
IAEA Training Material on Radiation Protection in Radiotherapy Radiation Protection in Radiotherapy Part 6 Brachytherapy Lecture 2: Brachytherapy Techniques Part 6: Brachytherapy Lesson 2: Techniques Learning objectives: Upon completion of this lesson, the students will be able to: To be familiar with different implant techniques To understand different systems of dose prescription To be aware of differences between permanent implants, low (LDR) and high dose rate (HDR) applications To appreciate the potential for optimization in high dose rate brachytherapy Activity: lecture Duration: 2 hours Materials and equipment needed: (List materials and equipment needed to conduct the session, if appropriate) References: (List the references for the session)

Part 6, lecture 2: Brachytherapy techniques
Very flexible radiotherapy delivery Source position determines treatment success Depends on operator skill and experience In principle the ultimate ‘conformal’ radiotherapy Highly individualized for each patient Typically an inpatient procedure as opposed to external beam radiotherapy which is usually administered in an outpatient setting The lecturer can cross reference brachytherapy to the modern external beam attempts of conformal RT and even intensity modulated radiotherapy (IMRT). Both of these techniques (conforming the high dose region to the target volume and optimizing the dose distribution in target and normal tissues) have been implemented in brachytherapy well before they were technologically possible in EBT. This has been possible as the brachytherapy oncologist is literally in touch with the tumor region and more recently has acquired the potential for optimization due to stepping source high dose rate brachytherapy. The last point can be qualified by the lecturer: One of the main reasons why HDR brachytherapy is so popular is that it can be delivered as an outpatient procedure with the cost-savings afforded by this Seed implants are also often an outpatient procedure. Part 6, lecture 2: Brachytherapy techniques

Objectives To be familiar with different implant techniques To be aware of differences between permanent implants, low (LDR) and high dose rate (HDR) applications To appreciate the potential for optimization in high dose rate brachytherapy To be familiar with some special techniques used in modern brachytherapy (seed implants, endovascular brachytherapy) Part 6, lecture 2: Brachytherapy techniques

Contents 1. Clinical brachytherapy applications 2. Implant techniques and applicators 3. Delivery modes and equipment 4. Special techniques A. Prostate seed implants B. Endovascular brachytherapy C. Ophthalmic applicators Part 6, lecture 2: Brachytherapy techniques

Clinical brachytherapy
Illustrated is a tongue implant treated with HDR brachytherapy - the participants will get more information on these treatment as the lecture progresses. Part 6, lecture 2: Brachytherapy techniques

History Brachytherapy has been one of the earliest forms of radiotherapy After discovery of radium by M Curie, radium was used for brachytherapy already late 19th century There is a wide range of applications - this versatility has been one of the most important features of brachytherapy A history of brachytherapy is available from Nucletron corporation (Mould (ed)). Part 6, lecture 2: Brachytherapy techniques

Today Many different techniques and a large variety of equipment Less than 10% of radiotherapy patients receive brachytherapy Use depends very much on training and skill of clinicians and access to operating theatre The picture illustrates two orthogonal X-rays from a gynecological brachytherapy insertion, the most common form of brachytherapy Part 6, lecture 2: Brachytherapy techniques

A brachytherapy patient
Typically localized cancer Often relatively small tumour Often good performance status (must tolerate the operation) Sometimes pre-irradiated with external beam radiotherapy (EBT) Often treated with combination brachytherapy and EBT Part 6, lecture 2: Brachytherapy techniques

Patient flow in brachytherapy
Treatment decision Ideal plan - determines source number and location Implant of sources or applicators in theatre Localization of sources or applicators (typically using X Rays) This is an important slide - the lecturer should take some time to guide participants through this process. It will also be discussed in more detail in part 11 in the context of clinical dosimetry/treatment planning. Once a decision for brachytherapy is made, one typically prepares a pre-implant plan using idealized geometry. This provides the guidance for the actual implant of active sources (life implant) or catheters/needles/applicators. Following this the geometry of the implant is assessed and a plan made which takes into account the actual location of the sources. In HDR brachytherapy, it is now still possible to optimize the implant by adjusting the dwell positions. The lecturer can point out that variations to the flow can occur depending on the application - this is topic of the next section in the lecture. Treatment plan Commence treatment Part 6, lecture 2: Brachytherapy techniques

1. Clinical brachytherapy applications
A. Surface moulds B. Intracavitary (gynaecological, bronchus,..) C. Interstitial (Breast, Tongue, Sarcomas, …) not covered here: unsealed source radiotherapy (Thyroid, Bone metastasis, …) - this is dealt with in the IAEA training material on radiation protection in Nuclear Medicine Part 6, lecture 2: Brachytherapy techniques

A. Surface moulds Treatment of superficial lesions with radioactive sources in close contact with the skin Hand A mould for the back of a hand including shielding designed to protect the patient during treatment The lecturer can point out that the sources are transferred at the side away from the patient to avoid unnecessary exposure Catheters for source transfer Part 6, lecture 2: Brachytherapy techniques

Historical example Surface applicator with irregular distribution of radium on the applicator surface (Murdoch, Brussels 1933) Part 6, lecture 2: Brachytherapy techniques

Other example Treatment of squamous cell carcinoma of the forehead The lecturer should point out that the sources are not placed directly on the skin of the patient. The distance from the skin determines the depth of treatment. Catheters for source placement Part 6, lecture 2: Brachytherapy techniques

Source distance from the skin
Determines incident dose Determines dose fall off in skin - the further the sources are from the skin the less influence has dose fall off due to inverse square law Dose homogeneity - the further away the sources are the more homogenous the dose distribution is at the skin Part 6, lecture 2: Brachytherapy techniques

Simulator films of forehead mould
Two X-rays of the forehead mould shown before illustrate the location of the catheters. The lecturer can point out that dummy wires with opaque markers in fixed distances have been inserted in the catheters to show their location and allow determination of required source length.. Dummy wires as markers for location

Set up of the mould on a HDR unit - in practice all catheters are connected.

Surface mould advantages
Fast dose fall off in tissues Can conform the activity to any surface Flaps available The picture shows a flap commercially available from Nucletron. The catheters are pre-placed in the flap which can be taped to the patient’s skin. Part 6, lecture 2: Brachytherapy techniques

B. Intracavitary implants
Introduction of radioactivity using an applicator placed in a body cavity Gynaecological implants Bronchus Oesophagus Rectum The illustration shows a gynaecological applicator Part 6, lecture 2: Brachytherapy techniques

Gynaecological implants
Most common brachytherapy application - cervix cancer Many different applicators Either as monotherapy or in addition to external beam therapy as a boost X-ray of an applicator with two ovoids, an intrauterine line and an independent rectal marker (dotted line). Part 6, lecture 2: Brachytherapy techniques

Gynecological applicators
Different design - all Nucletron Part 6, lecture 2: Brachytherapy techniques

Vaginal applicators Single source line Different diameters and length Gammamed - on the right with shielding Nucletron Part 6, lecture 2: Brachytherapy techniques

Bronchus implants Often palliative to open air ways Usually HDR brachytherapy Most often single catheter, however also dual catheter possible The picture shows a Nucletron HDR brachytherapy unit. Part 6, lecture 2: Brachytherapy techniques

Dual catheter bronchus implant
Catheter placement via bronchoscope Bifurcation may create complex dosimetry Part 6, lecture 2: Brachytherapy techniques

C. Interstitial implants
Implant of needles or flexible catheters directly in the target area Breast Head and Neck Sarcomas Requires surgery - often major In practice these are the most demanding implants as they include significant surgery - this means one needs to book theatres and get surgeons and anesthetists together with a radiation oncologist. It also means that recovery is required and the patient maybe in pain and under distress. Part 6, lecture 2: Brachytherapy techniques

Interstitial implants - tongue implant
Catheter loop tongue Button Brachytherapy in the head and neck region is typically better at preserving normal function of organs (eg speech) than surgery or external beam radiotherapy. Tongue implants are demanding, in particular if at the back of the oral cavity. The catheters go through the neck and the tongue into the oral cavity and either curve around or end in a button. tongue Part 6, lecture 2: Brachytherapy techniques

Breast implants Typically a boost Often utilizes templates to improve source positioning Catheters or needles Part 6, lecture 2: Brachytherapy techniques

2. Implant techniques and applicators
Permanent implants patient discharged with implant in place Temporary implants implant removed before patient is discharged from hospital A useful distinction - also in terms of cost. A day in a hospital can be rather costly. Part 6, lecture 2: Brachytherapy techniques

Permanent implants Implantation of sealed sources (typically seeds) into the target organ of the patient Sources are NOT removed and patient is discharged with activity in situ (compare part 16 of the course) The participants should be familiar with these implant from the previous lecture. It will be covered in more depth also later in the present lecture in the context of prostate seed implants. Part 6, lecture 2: Brachytherapy techniques

Radiation protection issues
Patients are discharged with radioactive sources in place: lost sources exposure of others issues with accidents to the patient, other medical procedures, death, autopsies and cremation Discussed in more detail in parts 9 (Medical Exposure), 16 (Discharge of patients) and 17 (Public exposure) Part 6, lecture 2: Brachytherapy techniques

Source requirement for permanent implants
Low energy gammas or betas to minimize radiation levels outside of the patient (125-I is a good isotope) May be short-lived to reduce dose with time (198-Au is a good isotope) More details on most common 125-I prostate implants in section 4A of the lecture Participants should have by now have some understanding of these implants and isotopes. Part 6, lecture 2: Brachytherapy techniques

Temporary implants Implant of activity in theatre Manual afterloading Remote afterloading Headings of the following sections of the course - the meaning of all these will be discussed in the following. Part 6, lecture 2: Brachytherapy techniques

Implant of activity in theatre
(Common for permanent implants) For temporary implants common practice 40 years ago when radium was commonly used for example gynecological implants of radium or 137-Cs needles Today only very rarely used for temporary implants - one of few examples are 192Ir hairpins for tongue implants The lecturer should ensure that participants understand that the first two points are not linked - the first is about permanent implants, the second on temporary implants: no one would use radium or 137-Cs for permanent implants. Part 6, lecture 2: Brachytherapy techniques

Problems with handling activity in the operating theatre
Potential of lost sources The time to place the sources in the best possible locations is typically limited Radiation protection of staff may require awkward operation Part 6, lecture 2: Brachytherapy techniques

Afterloading Implant only empty applicator or needles/catheters in theatre Once patient has recovered, dummy sources are introduced to verify the location of the applicators (typically using diagnostic X Rays) The treatment is planned The sources are introduced into the applicator or needle/catheter Afterloading is an important concept and advance in brachytherapy. The lecturer should take some time to discuss its role within the flow of brachytherapy - he/she could show also the next slide which is currently hidden. Part 6, lecture 2: Brachytherapy techniques

Patient flow in brachytherapy
Treatment decision Ideal plan - determines source number and location Implant of sources or applicators in theatre Localization of sources or applicators (typically using X Rays) This is an important slide - the lecturer should take some time to guide participants through this process. It will also be discussed in more detail in part 11 in the context of clinical dosimetry/treatment planning. Once a decision for brachytherapy is made, one typically prepares a pre-implant plan using idealized geometry. This provides the guidance for the actual implant of active sources (life implant) or catheters/needles/applicators. Following this the geometry of the implant is assessed and a plan made which takes into account the actual location of the sources. In HDR brachytherapy, it is now still possible to optimize the implant by adjusting the dwell positions. The lecturer can point out that variations to the flow can occur depending on the application - this is topic of the next section in the lecture. Treatment plan Commence treatment Part 6, lecture 2: Brachytherapy techniques

Afterloading Manual The sources are placed manually usually by a physicist The sources are removed only at the end of treatment Remote The sources are driven from an intermediate safe into the implant using a machine (“afterloader”) The sources are withdrawn every time someone enters the room The picture shows the Buchler HDR remote afterloader Part 6, lecture 2: Brachytherapy techniques

Afterloading advantages
No rush to place the sources in theatre - more time to optimize the implant Treatment is verified and planned prior to delivery Significant advantage in terms of radiation safety (in particular if a remote afterloader is used) Part 6, lecture 2: Brachytherapy techniques

Quick question: Why is afterloading the method of choice from a radiation safety perspective? This question gives the lecturer an opportunity to elaborate on the last point listed in the previous slide. Participants should be involved in the discussion of the next slide.

Some radiation safety aspects of afterloading
No exposure in theatre Optimization of medical exposure possible No transport of a radioactive patient necessary ‘Live’ implants should be avoided for temporary implants Part 6, lecture 2: Brachytherapy techniques

Applicators for brachytherapy
This is a slide showing the range of Nucletron applicators - there is no need for a detailed description. The important factors are: 1. There are many applicators available allowing for choice 2. The most important ones are described in the following. Part 6, lecture 2: Brachytherapy techniques

Brachytherapy Applicators - lots to choose from, lots to learn
Depending on the experience the lecturer can use this slide to introduce particular applicator types as appropriate Part 6, lecture 2: Brachytherapy techniques

Some examples for applicators
Gynaecological applicators Fletcher Suit A similar slide had been shown before - all are Nucletron applicators. There are some differences in dose distribution and placement - in practice the use of a particular applicator is typically preference (due to previous experience) by the clinician. Henschke type Ring type Part 6, lecture 2: Brachytherapy techniques

Rotterdam Applicator A choice of sizes allows customized treatment of each patient The applicator is typically bought as a set allowing for all the variation shown here - the aim is to choose the best possible fit for a particular patient. Part 6, lecture 2: Brachytherapy techniques

Close-up view Part 6, lecture 2: Brachytherapy techniques

Other intracavitary applicators
Vaginal Bronchus Part 6, lecture 2: Brachytherapy techniques

Interstitial applicators
Needles hollow and rigid may use templates for placement usually have pusher during implantation in tissue Two similar slides - here needles, the next catheters. In both cases the typical method of placing the catheters/needles is shown in the right lower corner. Part 6, lecture 2: Brachytherapy techniques

Interstitial applicators
Catheters flexible open and closed end available often introduced into tissue via an open end needle skin Part 6, lecture 2: Brachytherapy techniques

3. Delivery modes and equipment
Low Dose Rate (LDR) Medium Dose Rate (MDR) High Dose Rate (HDR) Pulsed Dose Rate (PDR) The headings of sections to come... Part 6, lecture 2: Brachytherapy techniques

Delivery modes - different classifications are in use
Low Dose Rate Medium Dose Rate High Dose Rate Pulsed Dose Rate < 1Gy/hour around 0.5Gy/hour > 1Gy/hour not often used >10Gy/hour pulses of around 1Gy/hour The lecturer may want to point out that the dose rate is meant to refer to the prescription point or isodose - this is discussed in more detail in part 11 of the course. Part 6, lecture 2: Brachytherapy techniques

Low dose rate brachytherapy
The only type of brachytherapy possible with manual afterloading Most clinical experience available for LDR brachytherapy Performed with remote afterloaders using 137-Cs or 192-Ir LDR = low dose rate Part 6, lecture 2: Brachytherapy techniques

Low dose rate brachytherapy
Selectron for gynecological brachytherapy 137-Cs pellets pushed into the applicators using compressed air 6 channels for up to two parallel treatments The Nucletron selectron - shown is the control unit which usually sits on top of the safe and operational unit outside the treatment room. Nucletron Part 6, lecture 2: Brachytherapy techniques

Simple design No computer required Two independent timers Optical indication of source locations Permanent record through printout Key to avoid unauthorized use Part 6, lecture 2: Brachytherapy techniques

Treatment process Implant of applicator (typically in the operating theatre) Verification of applicator positioning using diagnostic X Rays (e.g. radiotherapy simulator) Shown is a lateral and an anterior X-ray of a gynaecological implant. Part 6, lecture 2: Brachytherapy techniques

Two orthogonal views allow to localize the applicator in three dimensions The lecturer can point out that from a theoretical point of view the two orthogonal views do not need to be AP and lateral - it may be often better to use two oblique projections. Part 6, lecture 2: Brachytherapy techniques

Treatment planning Most commercial treatment planning systems have a module suitable for brachytherapy planning: Choosing best source configuration Calculate dose distribution Determine time required to give desired dose at prescription points Record dose to critical structures Part 6, lecture 2: Brachytherapy techniques

Treatment planning of different brachytherapy implants
The picture shows just some illustrations from treatment plans: a) a radium gynecological implant b) an interstitial breast implant Part 6, lecture 2: Brachytherapy techniques

High Dose Rate Brachytherapy
Most modern brachytherapy is delivered using HDR Reasons? Outpatient procedure Optimization possible The picture shows a Nucletron HDR unit for 192-Ir Part 6, lecture 2: Brachytherapy techniques

HDR brachytherapy In the past possible using 60-Co pellets
Today, virtually all HDR brachytherapy is delivered using a 192-Ir stepping source Source moves step by step through the applicator - the dwell times in different locations determine the dose distribution Part 6, lecture 2: Brachytherapy techniques

HDR 192-Ir source Source length 5mm, diameter 0.6mm
Activity: around 10Ci From presentation by Pia et al. Part 6, lecture 2: Brachytherapy techniques

Optimization of dose distribution adjusting the dwell times of the source in an applicator Shown are dose distributions achieved with HDR stepping source brachytherapy Nucletron Part 6, lecture 2: Brachytherapy techniques

HDR brachytherapy procedure
Implant of applicators, catheters or needles in theatre For prostate implants as shown here use transrectal ultrasound guidance Part 6, lecture 2: Brachytherapy techniques

HDR brachytherapy procedure
Localization using diagnostic X Rays Part 6, lecture 2: Brachytherapy techniques

Treatment planning Definition of the desired dose distribution (usually using many points) Computer optimization of the dwell positions and times for the treatment Part 6, lecture 2: Brachytherapy techniques

Treatment Transfer of date to treatment unit Connecting patient Treat... Gammamed The picture purposely shows two different HDR units. The transfer of all the dwell positions and time (eg 20 per catheter for 15 catheters) is critical for the operation of the HDR unit. In practice one requires the planning system and the treatment unit from the same manufacturer. Nucletron Part 6, lecture 2: Brachytherapy techniques

HDR unit interface Gammamed - the lecturer can read out the different captions if they are too difficult to see by the participants. Part 6, lecture 2: Brachytherapy techniques

HDR brachytherapy Usually fractionated (e.g. 6 fractions of 6Gy) Either patient has new implant each time or stays in hospital for bi-daily treatments Time between treatments should be >6hours to allow normal tissue to repair all damage Part 6, lecture 2: Brachytherapy techniques

HDR units: different designs available
Gammamed and Buchler Part 6, lecture 2: Brachytherapy techniques

Catheters are indexed to avoid mixing them up
Varian Varisource system Transfer catheters are locked into place during treatment - green light indicates the catheters in use Part 6, lecture 2: Brachytherapy techniques

HDR systems Can be moved between different facilities or into theatre for intra-operative work Nucletron system - the large wheels are an excellent idea, eg trying to move the unit into a lift. Part 6, lecture 2: Brachytherapy techniques

Pulsed dose rate Unit has a similar design as HDR, however the activity is smaller (around 1Ci instead of 10Ci) Stepping source operation - same optimization possible as in HDR Treatment over same time as LDR treatment to mimic favorable radiobiology In-patient treatment: hospitalization required Source steps out for about 10 minutes per hour and then retracts. Repeats this every hour to deliver minifractions (‘pulses’) of about 1Gy Part 6, lecture 2: Brachytherapy techniques

Pulsed dose rate brachytherapy
Different dose/time pattern possible Usually treatment about once per hour Illustration form ICRU report 58 International Commission on Radiation Units and Measurements ICRU 58, Bethesda. Prescribing, recording, and reporting interstitial brachytherapy Part 6, lecture 2: Brachytherapy techniques

Features of PDR: Advantages Emulates LDR Optimized dose distribution Visitors and nursing staff can use the time between pulses while the activity is in the safe Disadvantages Potential radiation safety hazard of a source stuck in the patient: In LDR - low activity, no severe problem In HDR - physicist is present during treatment In PDR - will someone with sufficient training be there within 10 minutes? Even at midnight??? Part 6, lecture 2: Brachytherapy techniques

Question: Please list advantages and disadvantages of High Dose Rate Brachytherapy as compared to Low Dose Rate brachytherapy. Assume both approaches are performed using remote afterloading equipment. A quick question to get participants involved...

The answer should include:
Advantages Out patient procedure Optimization of dose distribution using stepping source Possibly better geometry as patient anesthetized No exposure of nursing staff during procedure No source preparation Disadvantages Potential radiobiological disadvantage Fractionation required More shielding required There is no time to intervene if machine failure occurs More sophisticated (and expensive) Part 6, lecture 2: Brachytherapy techniques

Radiation Protection in Radiotherapy

Similar presentations

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

Similar presentations

About project

Feedback

Log in

Auth with social network:

Radiation Protection in Radiotherapy

Similar presentations

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

Similar presentations

About project

Feedback