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IAEA Training Material on Radiation Protection in Radiotherapy. Radiation Protection in Radiotherapy. Part 6 Brachytherapy Lecture 2: Brachytherapy Techniques. Brachytherapy. Very flexible radiotherapy delivery Source position determines treatment success

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radiation protection in radiotherapy

IAEA Training Material on Radiation Protection in Radiotherapy

Radiation Protection inRadiotherapy

Part 6

Brachytherapy

Lecture 2: Brachytherapy Techniques

brachytherapy
Brachytherapy
  • 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

Part 6, lecture 2: Brachytherapy techniques

objectives
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
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
Clinical brachytherapy

Part 6, lecture 2: Brachytherapy techniques

history
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

Part 6, lecture 2: Brachytherapy techniques

today
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

Part 6, lecture 2: Brachytherapy techniques

a brachytherapy patient
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
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)

Treatment plan

Commence treatment

Part 6, lecture 2: Brachytherapy techniques

1 clinical brachytherapy applications
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
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

Catheters for

source transfer

Part 6, lecture 2: Brachytherapy techniques

historical example
Historical example

Surface applicator with irregular distribution of radium on the applicator surface

(Murdoch, Brussels 1933)

Part 6, lecture 2: Brachytherapy techniques

other example
Other example

Treatment of squamous cell carcinoma of the forehead

Catheters for source placement

Part 6, lecture 2: Brachytherapy techniques

source distance from the skin
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
Simulator films of forehead mould

Dummy wires as markers for location

surface mould advantages
Surface mould advantages
  • Fast dose fall off in tissues
  • Can conform the activity to any surface
  • Flaps available

Part 6, lecture 2: Brachytherapy techniques

b intracavitary implants
B. Intracavitary implants
  • Introduction of radioactivity using an applicator placed in a body cavity
    • Gynaecological implants
    • Bronchus
    • Oesophagus
    • Rectum

Part 6, lecture 2: Brachytherapy techniques

gynaecological implants
Gynaecological implants
  • Most common brachytherapy application - cervix cancer
  • Many different applicators
  • Either as monotherapy or in addition to external beam therapy as a boost

Part 6, lecture 2: Brachytherapy techniques

gynecological applicators
Gynecological applicators

Different design - all Nucletron

Part 6, lecture 2: Brachytherapy techniques

vaginal applicators
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

Bronchus implants

Part 6, lecture 2: Brachytherapy techniques

dual catheter bronchus implant
Dual catheter bronchus implant
  • Catheter placement via bronchoscope
  • Bifurcation may create complex dosimetry

Part 6, lecture 2: Brachytherapy techniques

c interstitial implants
C. Interstitial implants
  • Implant of needles or flexible catheters directly in the target area
    • Breast
    • Head and Neck
    • Sarcomas
  • Requires surgery - often major

Part 6, lecture 2: Brachytherapy techniques

interstitial implants tongue implant
Interstitial implants - tongue implant

Catheter loop

tongue

Button

tongue

Part 6, lecture 2: Brachytherapy techniques

breast implants
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
2. Implant techniques and applicators
  • Permanent implants
    • patient discharged with implant in place
  • Temporary implants
    • implant removed before patient is discharged from hospital

Part 6, lecture 2: Brachytherapy techniques

permanent implants
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)

Part 6, lecture 2: Brachytherapy techniques

radiation protection issues
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
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

Part 6, lecture 2: Brachytherapy techniques

temporary implants
Temporary implants
  • Implant of activity in theatre
  • Manual afterloading
  • Remote afterloading

Part 6, lecture 2: Brachytherapy techniques

implant of activity in theatre
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

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

Problems with handling activity in the operating theatre

Part 6, lecture 2: Brachytherapy techniques

afterloading
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

Part 6, lecture 2: Brachytherapy techniques

afterloading35
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

Afterloading

Part 6, lecture 2: Brachytherapy techniques

afterloading advantages
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

Quick question:

Why is afterloading the method of choice from a radiation safety perspective?

some radiation safety aspects of afterloading
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
Applicators for brachytherapy

Part 6, lecture 2: Brachytherapy techniques

brachytherapy applicators lots to choose from lots to learn
Brachytherapy Applicators - lots to choose from, lots to learn

Part 6, lecture 2: Brachytherapy techniques

some examples for applicators
Some examples for applicators
  • Gynaecological applicators

Fletcher Suit

Henschke type

Ring type

Part 6, lecture 2: Brachytherapy techniques

rotterdam applicator
Rotterdam Applicator
  • A choice of sizes allows customized treatment of each patient

Part 6, lecture 2: Brachytherapy techniques

close up view
Close-up view

Part 6, lecture 2: Brachytherapy techniques

other intracavitary applicators
Vaginal

Bronchus

Other intracavitary applicators

Part 6, lecture 2: Brachytherapy techniques

interstitial applicators
Interstitial applicators
  • Needles
    • hollow and rigid
    • may use templates for placement
    • usually have pusher during implantation in tissue

Part 6, lecture 2: Brachytherapy techniques

interstitial applicators46
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
3. Delivery modes and equipment
  • Low Dose Rate (LDR)
  • Medium Dose Rate (MDR)
  • High Dose Rate (HDR)
  • Pulsed Dose Rate (PDR)

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

Delivery modes - different classifications are in use

Part 6, lecture 2: Brachytherapy techniques

low dose rate brachytherapy
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

Part 6, lecture 2: Brachytherapy techniques

low dose rate brachytherapy50
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

Nucletron

Part 6, lecture 2: Brachytherapy techniques

simple design
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
Treatment process
  • Implant of applicator (typically in the operating theatre)
  • Verification of applicator positioning using diagnostic X Rays (e.g. radiotherapy simulator)

Part 6, lecture 2: Brachytherapy techniques

two orthogonal views allow to localize the applicator in three dimensions
Two orthogonal views allow to localize the applicator in three dimensions

Part 6, lecture 2: Brachytherapy techniques

treatment planning
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
Treatment planning of different brachytherapy implants

Part 6, lecture 2: Brachytherapy techniques

high dose rate brachytherapy
High Dose Rate Brachytherapy
  • Most modern brachytherapy is delivered using HDR
  • Reasons?
    • Outpatient procedure
    • Optimization possible

Part 6, lecture 2: Brachytherapy techniques

hdr brachytherapy
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
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
Optimization of dose distribution adjusting the dwell times of the source in an applicator

Nucletron

Part 6, lecture 2: Brachytherapy techniques

hdr brachytherapy procedure
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 procedure61
HDR brachytherapy procedure
  • Localization using diagnostic X Rays

Part 6, lecture 2: Brachytherapy techniques

treatment planning62
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
Treatment
  • Transfer of date to treatment unit
  • Connecting patient
  • Treat...

Gammamed

Nucletron

Part 6, lecture 2: Brachytherapy techniques

hdr unit interface
HDR unit interface

Part 6, lecture 2: Brachytherapy techniques

hdr brachytherapy65
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
HDR units: different designs available

Part 6, lecture 2: Brachytherapy techniques

catheters are indexed to avoid mixing them up
Catheters are indexed to avoid mixing them up

Transfer catheters are locked into

place during treatment - green light

indicates the catheters in use

Part 6, lecture 2: Brachytherapy techniques

hdr systems
HDR systems
  • Can be moved between different facilities or into theatre for intra-operative work

Part 6, lecture 2: Brachytherapy techniques

pulsed dose rate
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
Pulsed dose rate brachytherapy
  • Different dose/time pattern possible
  • Usually treatment about once per hour
  • Illustration form ICRU report 58

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???

Features of PDR:

Part 6, lecture 2: Brachytherapy techniques

question

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.

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)

The answer should include:

Part 6, lecture 2: Brachytherapy techniques