BRACHYTHERAP Y
P RI NCI P L E AND METHODS
DR. MANOJ KUMAR B
MODERATOR:PROF. S.C. SHARMA
DEPTT. OF RADIOTHERAPY AND ONCOLOGY
PGIMER,CHANDIGARH
BRACHYTHERAP Y
 Type of radiation treatment in which
radioactive sources are arranged in
such a fashion that radiation is
delivered to the tumor at a short
distance by interstitial, intracavitary
or surface application.
CLI NI CAL ADVANTAGES









High biological efficacy
Rapid dose fall-off
High tolerance
Tolerable acute intense reaction
Decreased risk of tumor population
High control rate
Better cosmesis
Minimal radiation morbidity
Day care procedure
LI MI TATI ONS &
DI S ADVANTAGES
Difficult for inaccessible regions
Limited for small tumors (T1_T2)
Invasive procedures, require GA
Higher dose inhomogeneity
Greater conformation –small errors in
placement of sources lead to extreme changes
from the intended dose distribution
 Radioactive hazards (not now)
 Costly





S ELECTI ON CRI TERI A
 Easily accessible lesions
 Early stage diseases (Ideal implant ≤ 5 cm)
 Well localized tumor to organ of origin
 No nodal or distant metastases
 No local infections or inflammation
 Favorable histology- mod. diff. i.e. SCC
 Non DM / HTN
 Proliferative/ ulcerative lesions preferred
I NDI CATI ONS
 RADICAL RADIATION
 Skin malignanciesBCC, SCC
 Head & neck cancers
 Ca cx
 Ca prostate
 BOOST AFTER
EXT.RT±CCT
 Head & neck cancers
 Ca Breast
 Esophagus
 Anal canal
I NDI CATI ONS . . .
 PERIOPERTIVE
 STS
 Ca Breast
 POSTOP
 Ca Endometrium
 Ca cx
 Ca Breast
 PALLIATIVE
 Bronchogenic Ca
 Biliary duct malignancy
 Ca Esophagus
 Recurrent tumors
 BENIGN
 Keloids / Pterygium
 OTHERS
 Endovascular/Rad.
stent
CLAS S I F I CATI ON
Positioning of Radionuclide
Dose rate of irradiation
Classification
Schemes
Duration of irradiation
Loading pattern
CLAS S I F I CATI ON
 SURGICAL APPROACH
/ POSITIONING
 SOURCE IN TUMOR




INTERSTITIAL
INTRACAVITARY
INTRALUMINAL
ENDOVASCULAR
 SOURCE IN CONTACT
BUT SUPERFICIAL
 SURFACE
BRACHYTHERAPY/
MOULAGE
 DURATION OF
IRRADIATION
 TEMPORARY-Cs137,Ir192
 PERMANENT-I125,Au198
DOS E RATE( I CRU 3 8 )
 LOW DOSE RATE (LDR)



0.4-2 Gy/hr
Bed confinement
LDR A/L : Cs137
 MEDIUM DOSE RATE (MDR)

2-12 Gy/hr
 HIGH DOSE RATE (HDR)

> 12 Gy/hr
 ULTRA LOW DOSE RATE

0.01-0.3 Gy/hr
 ROUGHLY



LDR – 10 Gy/day
MDR -10 Gy/hr
HDR – 10 Gy/min
ADVANTAGES
LDR
HDR
 Predictable clinical effects
 SHORT T/T TIME
 Superior radiobiological
 Geometry well maintained
 Less morbidity, control is
comfort
 Day care procedure
role
best
 Well practised since long
 Minimum intersession
variability in dose
distribution
 Better patient compliance /
 OPTIMIZATION
 NO RADIATION HAZARDS
 SMALL APPLICATOR
 Less tissue trauma
 Better packing
MDR BRACHYTHERAPY
 ADVANTAGES
 Comparative shorter T/T time
 One time treatment can be used
 Patient convenience
 Radio biologically acceptable nearer to LDR
Brachytherapy
 DISADVANTAGES
 Late complications increases if correction not done
S OURCE LOADI NG TECHNI QUE
 PRELOADING SYSTEM
 Live sources
 ADVANTAGES
 Clinical results are best
 Affordable
 Long term results with lesser morbidities
 DISADVANTAGES
 Radiation hazards
 Special instruments
 Difficult application / hasty
 Geometry not maintained
 ? Optimization
AF TER LOADI NG TECHNI QUE
 MANUAL
 Avoids radiation




protection issue of
preloading
Better applicator
placement
Verification prior to
source placement
Min. radiation hazard
Advantages of
preloading
 REMOTE
CONTROLLED
No radiation hazard
Accurate placement
Geometry maintained
Better dose distribution
Highly precise
Short T/T time
Day care procedure
 Mainly used for HDR







I NTERS TI TI AL
BRACHYTHERAPY
 Sealed Radioactive sources directly implanted
into the tumor in a geometric fashion
 First suggested by Alexander Graham Bell
 ADVANTAGES
Higher local dose in shorter time
Rapid dose fall
Better tumor control
Lesser radiation morbidities
Superior cosmetics
 Functional preservation of organs





I NTERS TI TI AL
BRACHYTHERAPY…
 DISADVANTAGES
 Radiation hazards in older days
 Costly
 Not applicable to inaccessible areas
 INTENTION OF TREATMENT
 Always RADICAL
 As radical brachytherapy alone (smaller lesions)
 Local boost in combination with EBRT (larger lesion)
 NEVER USED FOR PALLIATION
S ELECTI ON CRI TERI A
 Easily accessible lesions, at least from one side
 Early stage disease
 T 1-T2 and sometimes early T3
 Ideally total size of implant ≤ 5 cm
 Non DM /HTN
 No local infection
 Proliferative and ulcerative lesions preferred
CLI NI CAL APPLI CATI ONS
 Head & neck tumors
 Early stage oropharyngeal cancers
 Ca breast- Boost /PBI
 Ca prostate
 Soft tissue sarcoma
 Gynecologic malignancies
 Ca anal canal and rectum
 Ca lung and pancreas
TYPES OF I NTERS TI TI AL
I MPLANTS
ACCORDI NG TO S I ZE/LOCATI ON/PROXI MI TY OF TUMOR TO NORMAL S TRUCTURES
 TEMPORARY
 PERMANENT
 Radioactive sources
 Preloaded – rigid needle
removed after desirable
dose has been delivered
 Rigid stainless steel
needles/flexible Teflon /
nylon guides/plastic
tubes
 Preloaded/After loaded
eg. Ra226 ,Cs137
 After loaded – Manual/
Remote
 Advantages
 Flexibility of implant
design
 Reduction of radiation
exposure levels resulting in
more accurate placement
of needles and guides
S YS TEMS OF I MPLANT
DOS I METRY
 OBJECTIVES OF TREATMENT PLANNING
 To determine the distribution & type of radiation
sources to provide optimum dose distribution
 To provide complete dose distribution in irradiated
volume
 SYSTEM USED
 Paterson-Parker (Manchester) system
 Quimby system (Memorial) system
 Paris system – Pierquin, Chassagne , Dutreix and
Marinello
 Computer System
S YS TEMS OF I MPLANT
DOS I METRY
 These system designed during times when
computers were not available for routine
planning
 Extensive table & elaborate rules of source
distribution were devised to facilitate the
process of manual treatment planning
 These systems differ in rule of implantation,
definition of dose uniformity & method used in
reference dose specification
RULES OF I NT. I MPLANT
PARAMETERS
MANCHESTER
QUIMBY
PARIS
S YS TEM
COMPUTER
Linear strength
Variable
Constant
Constant
Constant
Source
distribution
Planar implant:(periphery)
Area <25 cm- 2/3 Ra;
25-100 cm- ½ Ra; >100 cm1/3
Volume
implant::Cylinder:belt-4
parts,core-2,end-1
Sphere:shell-6,core-2
Cube :each side-1,core-2
Constant approx. 1 cm apart
from each other or from
crossing ends
Uniform
Uniform
Uniform
Uniform
Line sources Line sources
parallel
Parallel or
planes
cylinderic
volumes
Same as
Manchester
Constant,
Selective
Separation
8-15 mm
Constant
Selective
Required to enhance dose at
implant ends
Same
Crossing
needles not
used;active
length 3040% longer
Crossing
needles not
used;active
length 3040% longer
Spacing line
source
Crossing
needles
COMPONENTS - CLAS S I CAL
SYS
TEM
DISTRIBUTION RULES: given a target volume,
distribution rules determine how to distribute RA
sources & applicators in & around target volume
 DOSE SPECIFICATION & IMPLANT OPTIMIZATION
CRITERIA: Each system has a definition of
prescribed dose
 Above 2 criteria determine dose homogeneity,
normal tissue sparing, no. of catheters implanted
& margins around target
 DOSE CALCULATION AIDS: Older systems used
tables that give dose delivered per mg Ra-Eq-hr
as a function of treatment volume or area
 Recent Paris system uses computerized treatment
planning to relate absorbed dose to source strength &
PRI NCI PLE- MANCHES TER
SFEATURES
YS TEM
DOSE &
DOSE RATE
6000-8000 R in 6-8 days (1000 R/day; 40 R/hr)
UNIT / USE OF
RADIUM
mg Ra hr – defined as amount of radium to give specified dose
in 1 hr
DOSE
SPECIFICATION
CRITERA
Effective minimum dose 10% above absolute minimum dose
LINEAR
ACTIVITY
Variable: 0.66 and 0.33 mg RaEq/cm
QUI MBY S YS TEM
 Developed by Edith Quimby et al
 Dose 5000-6000 R in 3-4 days
 Equal linear intensity (mg RaEq/cm) needles distributed
uniformly (fixed spacing) in each implant, although
spacing selected in 1-2 cm range acc. to implant size
 Quimby tables (Nomogram ) give mg RaEq-hr to deliver
stated exposure of 1000 R as function of T.V. or area
(5000-6000 R over 3-4 days; 60-70 R/hour)
 No clear description of rules for distributing Ra needles
 Crossing recommended; peripheral needles placed on or
beyond T.V. boundaries
 Dose specification criteria inconsistent
NOT RECOMMENDED FOR CLINICAL USE
PARI S S YS TEM- PRI NCI PLES
RADIOACTVE SOURCES
 Rectilinear/parallel -arrangement so that centers
are located in the same plane which is
perpendicular to the direction of sourcesCENTRAL PLANE
 Equidistant
 Linear activity-uniform and identical
 Source geometries
 Linear- single-plane implants
 Squares/Equilateral triangles- two plane implants
PARI S S YS TEM
FEATURES
DOSE AND
DOSE RATE
6000 -7000 cGy in 3-11 days
DOSE PRESCRIPTION Average of the minimum doses in the region defined by the
POINT
source
REFERENCE DOSE &
DOSE GRADIENT
85 % of the BASAL DOSE
15 % between the Reference dose and the Basal dose
RA SOURCE
PLACEMENT
Reference isodose volume covers the treated volume
PERMANENT I MPLANTS
ADVANTAGES
DISADVANTAGES
 Less accessible sites
 Environmental issue
 Cont. ultra low dose
 Dosimetric uncertainties >
rate>Max biological
effectiveness
 Better tissue heal
 Better effect in slow and
radio resistant tumors
 Improved mobility
Later part of T/T becomes
less effective
 Source displacement
 Large tumor > Difficult
procedure and geometry
 Radio biologically less
effective for rapidly
proliferating tumors
COMPUTER S YS TEM
 Implant system evolved through use of





computers
Implantation rules: Sources of uniform strength
Spaced uniformly (1-1.5 cm), larger spacing for
larger implants to cover entire T.V.
Active length 30-40% longer than Target length
as ends uncrossed
T.V.: sufficient safety margins; peripheral
sources implanted on outer surface
Dose specified by isodose surface that surrounds
target
 Whole planning with help of computers
COMPUTER DOS I METRY
 Possible to preplan implants & complete isodose
distribution corresponding to final source
distribution
 Rapid & fast; helps modify implant
 Isodose patterns can be magnified &
superimposed on implant radiograph
 Localization of sources:
 Orthogonal Imaging method
 Stereo-shift method
 CT
 Dose Calculation:




No. of milligrams or millicurie in implant
Location of each source with respect to dose calculation point
Type of isotope being used
Filtration of the encapsulation
COMPUTER DOS I MTERY
 Dose Computation:
 Dose calculation Formalisms’ (AAPM TG 43
algorithm)
 Use Sievert Integral directly
 Precalculated dose tables
 For Radium & other long lived sources:
Dose rates in form of isodose curves
 For Iridium & relatively short lived
implants: Computer calculates cumulative
dose with decay correction
CLI NI CAL AP P L I CATI ONS
Oral Cavity:
 LIP:
 Indications: T1-2N0 Lesions
 T.V.: All visible & palpable tumour with 5-10 mm margin
 Dose: 50-70Gy in 5-7 days LDR
 Technique:
 Rigid afterloading needles maintained in place by
Template
 Classical plastic tubes
 Spacers to decrease dose to gingiva, teeth & other lip
CLI NI CAL APPLI CATI ONS …
Buccal Mucosa:
 Indications:
 Brachytherapy alone indicated for small (<4cm), welldefined lesions in anterior 2/3rd
 As boost after EBRT for larger lesions
 T.V.: GTV + margins
 Dose: Alone 65-70 Gy
 Boost 25-30 Gy
 Technique: Guide Gutter Technique: Lesion < 2cm
 Plastic tube technique: For other lesions
CLI NI CAL APPLI CATI ONS …
Oral Tongue:
 Indications: T1 N0, T2 N0 < 3cm lesion
 T.V.: GTV + 5 mm margin
 Dose: Alone:60-65 Gy LDR
 Boost 20-25 Gy after EBRT dose of 45-50 Gy
 Techniques: Guide-gutter technique
AP X-ray
CLI NI CAL APPLI CATI ONS …
Floor of Mouth:
 Indications: T1-2N0 lesions, ≥ 5 mm away from
mandible
 Dose: Techniques same as for Tongue implants
 Complication: Osteoradionecrosis:5-15%
Oropharynx:
 Indications: Ca BOT, soft palate, tonsillar fossa &
vallecula usually as boost after EBRT
 Lesions < 5 cm (after EBRT)
 T.V.: GTV + 10 mm margin
 Dose: Tonsillar fossa-25-30 Gy; BOT 30-35 Gy
 Technique: Classical Plastic Loop technique
CLI NI CAL APPLI CATI ONS …
Breast
Indications: Boost after BCS & EBRT
 Postoperative interstitial irradiation alone of
the primary tumor site after BCS in selected
low risk T1 and small T2N0 (PBI)
As sole modality
As Boost to EBRT
Patient choice: cannot come for
5-6 wks treatment :
Close, positive or unknown
margins
 Distance
 Lack of time
Elderly, frail, poor health patient
EIC
Large breasts: unacceptable
toxicity
Younger patients
Deep tumour in large breast
Irregularly thick target vol.
Moderator: Prof. S. C. Sharma
 Chest wall recurrences
CLI NI CAL APPLI CATI ONS …
 T.V.: Primary Tumor site + 2-3 cm margin
 Dose: As Boost: 10-20 Gy LDR
 AS PBI: 45-50 Gy in 4-5 days LDR (30-70 cGy/hour)
 34 Gy/10#, 2# per day HDR
 Technique:
 Localization of PTV: Surgical clips (at least 6)
 USG, CT or MRI localization, Intraop USG
 During primary surgery
 Guide needle technique or
 Plastic tube technique using Template
 Double plane implant
 Skin to source distance: Minimum 5 mm
CLI NI CAL APPLI CATI ONS …
CLI NI CAL APPLI CATI ONS …
Prostate:
 Indications
 Brachytherapy as monotherapy:
 Stage T1-2a & Gleason score 2-6 & PSA ≤ 10 ng/ml
 As boost after EBRT
 Stage T2b, T2c or Gleason score 7-10 or PSA > 10 ng/ml
 For brachytherapy, Prostate size < 50 cc
 Exclusion criteria:
 Life expectancy < 5 yrs
 Large or poorly healed TURP defect
 Distant Mets or operative risk
 T.V.: Whole prostate within capsule + 2-3 mm
margin
 Methods: Permanent Implant (I125 or Pd103) or
Temporary Implant (Ir192)
CLI NI CAL APPLI CATI ONS …
Technique for Permanent implant
 Retropubic approach with I125 seedsDisappointing results
 Modern technique: Transperineal Approach
 TRUS guided
 Two step approach
 Volume study of prostate
 Computer planning
 Seed positioning
 Coverage check -USG & Flouroscopy
 Check Cystoscopy
 Post-implant image based dosimetry
CLI NI CAL APPLI CATI ONS
 Dose:
 I125: 145 Gy as sole RT
 100-110 Gy as boost to 40-50 Gy EBRT
 Pd103: 125 Gy as sole RT
 90-100 Gy as boost to 40-50 Gy EBRT
 Temporary Implants with Ir192 (LDR or
HDR):
 Procedure same as above; lesser no. of plastic
catheters required (8-15)
 Dose:
 LDR 30-35 Gy seeds left for 3 days(Boost to 45 Gy EBRT)
 HDR 20-25 Gy, 4-6 Gy/#(Boost to 45 Gy EBRT)
CLI NI CAL APPLI CATI ONS
Soft tissue Sarcomas (using Ir192 or I125)
 Indications:
 As sole postop RT:
 completely resected intermediate or high grade tumours
of extremity or superficial trunk with -ve margins
 As boost to postop EBRT:
 Intermediate or high grade sarcoma with +/- margins
 Postop pts with small lesions & +ve/uncertain margins
 Deep lesions
 Low grade sarcomas
 T.V.: GTV + 2-5 cm margin
 GTV based on preop MRI & clinical findings
 Dose: LDR (Ir seeds or wires) as sole treatment
45-50 Gy in 4-6 days
 As boost to 45-50 Gy EBRT: 15-25 Gy in 2-3 days
CLI NI CAL APPLI CATI ONS …
 Technique:
 Usually performed at time of surgery
 Basic or sealed end temporary implant technique
CLI NI CAL APPLI CATI ONS …
Brain: Permanent or temporary (using I125 or Ir192
seeds/wires )
 Indications:
 As boost to EBRT or recurrence
 Anaplastic astrocytoma or GBM, unifocal, well
cicumscribed, peripheral lesions & < 5 cm in diameter
 T.V.: Contrast enhancing area on MRI +/- 5mm
margin
 Dose: LDR 50-60 Gy, 0.4-0.5 Gy/hr
 Technique: Planning CT/MRI done
CLI NI CAL APPLI CATI ONS …
Ca Anorectum
 Indications: As boost to EBRT/ChemoRT
 If T.V. doesnot exceeds 1/2 circumference, 5 mm thick, 5
cm long i.e. T1-2 & small T3 lesions
 T1N0 adenocarcinoma of rectum 3-10 cm above anus
 T.V.: Visible palpable tumor+5 mm
 Dose: LDR 15-20 Gy at 0.3-0.6 Gy/hr
 Technique: Guide needle technique with
template
CLI NI CAL APPLI CATI ONS …
Gynecological Tumors (Ir192 LDR or HDR)
 Indications:
 Ca Cervix
 Ca Endometrium
 Postop local recurrence
 Ca Vagina & Vulva
 Radical BT in select early lesions (T1-2N0)
 Boost after EBRT in large lesions (T2-3N1)
 Technique:
 Guide-gutter technique
 Blind plastic tube implant
(transperineal technique)
 Plastic or guide needles
CLI NI CAL APPLI CATI ON – CA
CX
ABS Recommendations
 Bulky primary disease
 Prior hysterectomy-inability to place tandem
 Post hysterectomy
 vault recc./cut-through hysterectomy/cervical
stump presentation
 Extesive parametrial involvement
 Distorted anatomy
 Narrow vagina & fornices
 Extensive / Distal vaginal wall involvement
 Re-irradiation after recurrences
 Prior course of RT to area of interest
CLI NI CAL APPLI CATI ONS …
 PERINEAL IMPLANTS
Martinez Universal Perineal
Interstitial Template (MUPIT)
Syed-Neblett template
CLI NI CAL APPLI CATI ONS …
 Dose:
 Radical BT:
 LDR: 55-60 Gy @ 50-90 cGy/hr
 HDR: 3.5 Gy/#@ 2#/day/12-16#
 Boost
 LDR: 15-25 Gy , 50-90 cGy/hr
 HDR: as above, no. of # depend upon EBRT doses
CLI NI CAL APPLI CATI ONS …
Other sites:
 Lung: Permanent perioperative BT, I125 seeds,
Au198 Grains
 Persistent or recurrent ds after EBRT or residual ds after
surgery
 Pancreas: Permanent perioperative BT, I125 seeds
 Locally advanced unresectable ds
 Penis & Urethra:
I NTRACAVI TARY APPLI CATI ON
 Radioactive sources are placed in a existing
cavity usually inside a predefined applicator
with special geometry
 Uses:
 Cervix
 Endometrium
 Vagina
 Maxilla
 Nasopharynx
PARI S S YS TEM
 Single application of radium
 Two cork colpostats (cylinder)
and an intrauterine tube
 Delivers a dose of 7000- 8000
mg-hrs of radium over a period
of five days(45R/hr)
(5500mg/hr
 Equal amount of radium used
in the uterus and the vagina
 Intrauterine sources

3 radioactive sources, with
source strengths in the ratio of
1:1:0.5
 colpostats
 sources with the same strength
as the topmost uterine source
S TOCKHOLM S YS TEM
 Fractionated course of radiation delivered




over a period of one month.
Usually 2-3 applications, each for a period
of 20- 30 hours (repeated 3weekly)
Intravaginal boxes -lead or gold
intrauterine tube -flexible rubber
Unequal loading
 30 - 90 mg of radium in uterus
 60 - 80 mg in vagina
Total prescribed dose -6500-7100 mg Ra
 4500 mg Ra contributed by the vaginal
box (dose rate-110R/hr or 2500mg/hr/#)
DRAWBACKS OF PARI S AND
S TOCKHOLM S YS TEMS
 Long treatment time
 Discomfort to the patient
 No dose prescription
MANCHES TER S YS TEM
 To define the treatment in terms of dose to a
point. Criteria of the point:
 Anatomically comparable
 Position
 where the dosage is not highly sensitive to small
alteration in applicator position
 Allows correlation of the dose levels with the
clinical effects
 To design a set of applicators and their loading
which would give the same dose rate irrespective
of the combination of applicators used
 To formulate a set of rules regarding the activity,
relationship and positioning of the radium
sources in the uterine tumors and the vaginal
POINT A
 PARACERVICAL TRIANGLE where initial lesion
of radiation necrosis occurs
 Area in the medial edge of broad ligament where
the uterine vessel cross over the ureter
 The point A -fixed point 2cm lateral to the
center of uterine canal and 2 cm from the
mucosa of the lateral fornix
POINT B





Rate of dose fall-off laterally
Imp. Calculating total dose-Combined with EBRT
Proximity to important OBTURATOR LNs
Same level as point A but 5 cm from midline
Dose ~20-25 % of the dose at point A
LOADI NG OF APPLI CATORS
 In order that point A receives same dosage
rate no matter which ovoid combination is
used ,it is necessary to have different radium
loading for each applicator size
 Dose rate 57.5 R/hr to point A
 Not more than 1/3 dose to point A must be
delivered from vaginal radium
 APPLICATORS
LOADI NG PATTERN
TUBE
TYPE
LENGTH
TUBES
RADIUM
(mg)
UNITS
(FUNDUS
to CX)
LOADING TUBES
(mg)
LARGE
6
3
35
6-4-4
15-10-10
MEDIUM
4
2
25
6-4
15-10
SMALL
2
1
20
8
20
VAGINAL
OVOIDS
TUBES
RADIUM
(mg)
UNITS
LOADING
TUBES(mg)
LARGE
3
22.5
9
10-10-5 or 20/25
MEDIUM
2
20
8
20
SMALL
1
17.5
7
10-5-5
or
20/15
GUI DELI NES
 Largest possible ovoid
 Lesser dose to mucosa
 Longest possible tandem (not > 6 cm)
 Better lateral throwoff
 Smaller dose to mucosa
 Dose to point A- 8000R
 Dose to uterus wall -30,000R
 Dose to vaginal mucosa-20,000R
 Dose to recto-vaginal septum- 6750 R
 Dose limitation
 BLADDER <80 Gy
 RECTUM <75 Gy
I NTRACAVI TARY APPLI CATORS
MANCHESTER
PGI
I DEAL APPLI CATI ON
 Tandem
 1/3 of the way between S1 –S2
and the symphysis pubis
 Midway between the bladder and
S1 -S2
 Bisect the ovoids
 Marker seeds should be placed
in the cervix
 Ovoids
against the cervix (marker seeds)
 Largest
 Separated by 0.5-1.0 mm
 Axis of the tandem-central

 Bladder and rectum -should be
packed away from the implant
I CRU REPORT NO. 3 8
DOSIMETRIC INFORMATION FOR REPORTING
 Complete description
 Technique
 Time-dose pattern
 Treatment prescription
 Total Reference Air Kerma
 Dose description
 Prescription points/surface
 Reference dose in central plane
 Mean central /peripheral dose
 Volumes: Treated/ point A/ reference volume
 Dose to Organs at Risk : bladder, rectum
 REFERENCE VOLUME
 Dimensions of the volume included in the corresponding
isodose
 The recommended dose 60 Gy
 TREATED VOLUME
 Pear and Banana shape
 Received the dose appropriate to achieve the purpose of
the treatment, e.g., tumor eradication or palliation, within
the limits of acceptable complications
 IRRADIATED VOLUME
 Volumes surrounding the Treated Volume
 Encompassed by a lower isodose to be specified, e.g., 90 –
50% of the dose defining the Treated Volume
 Reporting irradiated volumes may be useful for
interpretation of side effects outside
CERVI CAL BRACHYTHERAPY
ABS . DOS E AT REF ERENCE
NTS POINT
POI
BLADDER
 RECTAL POINT
 LYMPHATIC TRAPEZOID OF FLETCHER
 LOW PA, LOW COMM.ILIAC LN & MID EXT ILIAC LNs
 PELVIC WALL POINTS
 DISTAL PART OF PARAMETRIUM & OBTURATOR LNs
DOSE SCHEDULE
 LDR (<200cgy/hr)
 35-40 Gy at point A
 MDR (200-1200cgy/hr)
 35 Gy LDR EQUIVALENT at point A
 HDR(>1200cgy/hr)
 9 Gy in 2 #
 6.8Gy in 3# at point A
EXTERNAL RT WI TH
BRACHYTHERAP Y
 Brachytherapy can follow external irradiation
 SIMULTANEOUS
 Stage I - II with very minimal parametriun
involvement
 HDR -5 sessions (9gy /#/ 5, 1week apart)
 40 Gy by XRT simultaneously
 SANDWICH
 Stage I-II
 MDR 40 Gy LDR eq.—› XRT 40 Gy —› MDR 35 Gy
LDR eq.
 In both above cases a MIDLINE SHIELD is used
POS T OP/ VAULT
BRACHYTHERAPY
 Vault RT
 No residual disease
 8500 cGy at 5mm from the surface of the
vault
 2 sessions 1 week apart
 Residual disease
 CTV of 2 cm given to gross tumor and the
prescription of 8500cgy encompassing the
whole CTV is made
 2 sessions 1 week apart
 Mostly after XRT
POS T OP BRACHYTHERAPY
 CONTRAINDICATIONS
 Vaginal wall involvement ( middle- lower 1\3)
 Heavy parametrium infiltration
 VVF or VRF
 Inadequate space
 Medical contraindications
 Metastatic disease
 Supplementary radiation 2000 cGy \10# \ 2
weeks
S URF ACE MOULDS
Radiation is delivered by arranging RA
sources over the surface of tumor
 Types
 Planar
 Circular
 Square
 Rectangular
 Line source
 Cylinder
I NDI CATI ONS
 Superficial /Accessible tumors
 Skin ca
 Post mastectomy recurrence
 Oral tumor
 hard palate ,alveolus
 Penile carcinoma
CI RCULAR MOULDS
 Amount of radium used is obtained
from the table for a particular treating
distance
 Circular arrangement is the best
 Space between the needles (end)
should not be more than H
S QUARE MOULDS
 An arrangement is considered to be
linear if the distance between the
active end of the sources does not
exceed the height
 Length of the side of the square is less
than twice the height
 No further radium is placed in the center
RECTANGULAR MOULDS
The dividing lines or bars are placed parallel
to the longer side
 Elongation correction factor: Increase the
reading in milligrams hour by a given factor


This factor is proportional to the ratio of the sides
of the rectangle




1.5:1 = 2.5%
2:1 = 5%
3:1 = 9%
4:1 = 12%
CI RCULAR MOULDS
CURVED SURFACES
 Irregular area
 Curved surfaces:
convex, concave
 The smaller area is used
for calculation of radium
dose and implant rules
 Cylinder mould:
Amount of radium is
30D2
COAXIAL RINGS
 DISTRIBUION
RULES
 In case of coaxial
rings radium is
placed at a distance
equal to 2H
I NTRALUMI NAL
BRACHYTHERAPY
Radioactive source is passed through a tube
and passed into a hollow lumen
 Sites
 Esophagus
 Bronchus : Bronchogenic carcinoma
 Definitive : T1-T2tumors
 Palliative
 Dyspnea
 Cough
 Atelectasis
 Biliary tract
RADI OBI OLOGY
 Biological effects depend on





Dose prescribed
Treated volume
Dose rate
Fractionation
Treatment duration
 Heterogeneous dose distribution
 Higher average dose
 Short treatment
RADI OBI OLOGY – 4 Rs




Repair
Reassortment / redistribution
Repopulation
Reoxygenation
RADI OBI OLOGY- LDR
 Repair of Sublethal damage
 Most significant- 1 Gy/min and 0.3 Gy /h
 DNA repair
 Dynamic process
 Special kinetics
 Simple exponential kinetics
 Reassortment - slow and imp. <1 Gy/min
 Repopulation-slowest and significant
 Reoxygenation - relative slow process may be
a disadvantage
LDR AND HDR
LDR vs HDR
EFFECTS OF HDR
RADI OACTI VE S OURCES






Naturally occurring
Artificial
Induced by neutron bombardment
Induced by bombardment of protons
Fission product
CHARACTERISTICS







HALF LIFE
GAMMA ENERGY
BETA ENERGY
HALF VALUE LAYER
EXPOSURE RATE CONSTANT
BETA FILTRATION
DECAY SCHEME
I DEAL RADI ONUCLI DE
 Photon energy :low to medium- 0.03 to 0.5 MeV
 Monoenergetic beam preferred













Moderate Gamma ray constant
Long half life
High specific activity
Isotropic
No gaseous disintegration/daughter product
Nuclei should not disperse if source damaged
Low beta energy
Low or no self attenuation
Insoluble and nontoxic
Flexible
Easily available and cost effective
Withstand sterilization process
Disposable without radiation hazards to environment
RADI UM 2 2 6
 Sixth member of the radio active series which





starts with uranium and ends with lead
Half life 1620 years
Gamma energy 0.83 MeV
Half value 12mm Pb
Exposure rate constant 8.25 Rcm2/mCi-h
Filtration 0.5 – 1 mm Pt
RADI UM S UBS TI TUTES
NAME ORIGIN
T1/2
γ
β
β
ENERG ENERGY FILTRATI
Y-MeV
ON
Rn 222 NATURAL
3.83
days
0.83
Cs 137
FISSION
30.17 0.662
yrs
Co 60
NEUTRON 5.26
yrs
ACTIVAT.
- do 73.8
Ir 192
yrs
Stainless
steel
HVL ERC SPECI
(Pb
.
-mm
ACTI.
)12
10.27
DECAY
PRODU
CT
Ba 137
87
Pb 206
0.512
1.17
- do -
6.5
3.26
1.17,
1.33
0.38
- do-
11
13.07 1020
Ni 60
0.1361.06
0.0790.068
Platinum
4
4.69
Pt 192
-
Platinum
12
6.87
-
7760
Tn 182 - do -
115
yrs
0.67
Au 198 - do -
2.7
days
1.0880.412
0.96
St. steel
3.3
2.376
-
Hg 198
I 125
59.4
days
0.274,
0.314
No
Titanium
0.01
10th
1.403
-
Te 125
No
Platinum
0.03
6.87
-
Ru 103
- do -
Pd 103 - do -
16.97 0.21
-