for cervical cancer

1. SYSTEMS OF
BRACHYTHERAPY
Dr.Irfan Bashir

2. SYSTEMS OF BRACHY:-OUTLINE
Systems of implant
dosimetry
Systems of intracavitary
therapy
 Paterson Parker system
 Quimby System
 Paris system
 Computer System
 Stockholm system
 Paris system
 Manchester system
 International commission on
radiation units and
measurements system

3. INTRODUCTION
 Brachytherapy is a method of treatment in which
sealed radioactive sources are used to deliver radiation
at a short distance by interstitial, intracavitary or
surface application.
 High radiation dose to the tumour.
 Rapid dose fall off in the surrounding normal tissue.

4. PATERSON-PARKER SYSTEM
 Developed by Ralston Paterson (radiation oncologist)
and Herbert Parker (physicist) in the 1930s
 Aim: To deliver a uniform dose(within 10%) to a plane
or volume.
 Non - uniform distribution of sources

5. PLANAR IMPLANT
Technique used: When tumour spread is under the skin / lesion can be
sandwiched between parallel planes of implant.
 Effectively irradiate tissues of 1 cm thickness (0.5 cm on either side).
 Reference dose plane is 0.5 cm from source plane.
 The dose at 0.5 cm is the minimum dose throughout the 1 cm thick
slab.
 The high spots immediately surrounding each source are assumed to
be tolerated by tissues and its presence is ignored.

6. PLANAR IMPLANT

7. PLANAR IMPLANT
 Distribution laws:
-------------------------------------------------------------------------
Area Fraction of Activity on
(cm2) Periphery Center
-------------------------------------------------------------------------
< 25 2/3 1/3
25-100 1/2 1/2
> 100 1/3 2/3

8. PLANAR IMPLANT
 Needles spacing: not more than 1 cm. from each
other or from the crossing ends.
 For uncrossed ends: effective area has to be
reduced by 10% for each uncrossed ends. Fig.B
effective area is 0.9 x b x c and for Fig. C, it is 0.8 x
b x d

9. PLANAR IMPLANT
Multiplanar implant:
 Planes should be parallel to each other.
 Two plane implant: 1.5/2.0/2.5 cm.
 Separation is more than 1.0 cm between the planes then
 Plane Separation Multiplication Factor
1.5 1.25
2.0 1.40
2.5 1.50

10. VOLUME IMPLANT
When the lesion > 2.5 cm thick.
Two plane implant leads to low dose region midway
between the planes.
Tumours are implanted using 3D shapes:
Sphere
Cuboid
Cylinder.

11. VOLUME IMPLANT
Volume is divided into two parts: rind and core.
Sphere: rind → shell/surface,
Cuboid: rind → six faces,
Cyl: rind → belt &2 ends
Total amount of radium activity is divided into eight equal
parts:
Sphere: Shell – 6 parts, core - 2 parts
Cylinder: Belt - 4 parts, core - 2 parts, each end - 1 part
Cuboid : Each side 1 part, core 2 parts

12. VOLUME IMPLANT
 Needles should be placed as uniformly as possible, not
more than 1 cm apart.
 At least 8 needles in the belt and 4 in the core.
 Target volume effectively treated is reduced by 7.5% for
each uncrossed end.

14. Manchester system
 Dose and dose rate:- 6,000 R to 8,000 R in 6-8 days
(1,000 R/day; 40 R/h)
 Linear activity Variable:- 0.66 and 0.33 mg Ra Eq/cm

15. QUIMBY SYSTEM
 Quimby System (1932)
Developed by Edith Quimby at New York Memorial Hospital.
Uniform distribution of sources of equal linear activity
 Results:
 Non uniform distribution
 Hot spots in central region
 Planar Implant:
 Quimby table gives the mg.hrs required to deliver 1000R at the central
plane.
 Stated dose is the max. dose in the plane of implant
 Volume Implant:
 Stated dose is the min. dose within the implanted volume.

16. MEMORIAL SYSTEM
Extension of the Quimby System
 Based on computer generated dose
distributions
 Uniform source strength spaced 1 cm. apart
 Tables are generated to provide information
of mg- hrs required to deliver 1000 rads at 0.5
cm from the source plane for planar implant.

17. PARIS SYSTEM
 Developed in early 1960s by Pierquin, Dutreix
and Marinello.
 Sources of uniform activity
 Placed parallel and equidistant
 Square or triangular pattern for volume implant
 Source spacing varies between 8-15 mm for
short implant and 15-22 mm for long implants
 For target thickness < 12 mm, single plane
implant and for > 12 mm, double plane implant.

18. Basal Dose Rate (BD), is defined as the arithmetic mean of the
local minimum doses midway through an array of equally spaced
implants . For double plane implants, the basal dose rate is the
dose rate in the central cross-sectional plane at the intersection
of perpendicular bisectors projected from the side of the
triangle for triangular arrangement and at the geometric
centre for square arrangements.
Reference Dose Rate (RD) is equal to 85% BD and is the dose
rate used for dose prescription.
Ref. Dose Rate (RD) = 0.85 x BD

20. Paris system
 Dose and dose rate:- 6,000 cGy to 7,000 cGy in 3-11
days (25 cGy/h to 90 cGy/h)
 Linear activity Constant:- 4-14 µGy · m2 · h-1/cm

21. Paris system

22. COMPUTER SYSTEM
 Source of uniform strength are implanted.
 Spaced uniformly (e.g. 1.0 to 1.5cm) with larger spacing
for larger implant size.
 Cover the entire target volume.
Result of uniform activity source :- ‘’HOTTER’’ in
middle than periphery (as in Quimby & Paris system)

23. COMPUTER SYSTEM
 Dose specified at isodose surface that is just
surrounding the target .
 Better to implant a larger volume, then to select a
lower value of isodose curve to increase the coverage.
 Active length of line source should be suitably longer (
≈ 40% longer) then the length of target volume due to
uncrossed ends.

24. COMPUTER SYSTEM:- Advantages
 Older dosimetry system are based on idealized implants
conforming to certain distribution rule which are
seldom realised.
 In Computer system possible to preplan complete
isodose distribution corresponding to final source
distribution.
 Rapid turnaround time.
 Isodose curve may be generated in any arbitrary plane.
 Isodose pattern can be magnified & superimposed on an
implant radiograph for viewing distribution in relation to
patients anatomy.

25. INTRACAVITARY BRACHYTHERAPY
Three methods were developed between 1910 &
1938 for treatment of carcinoma cervix by
intracavitary brachytherapy.
1. Stockholm Method : 1914
2. Paris Method : 1919
3. Manchester System: 1938

26. 26
STOCKHOLM METHOD
 Fractionated course of radiation
delivered over a period of one month.
 Three insertions each of 22 hours
separated by 1-3 weeks.
 Intra-vaginal boxes Silver 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

27. 27
PARIS METHOD
 Devised by Claudine Regaud & Antone Lacassagne.
 Single application of radium for 120 hours.
 Two cork colpostats (cylinder) with 13.3 mg radium in each and
an intrauterine tube of silk rubber containing 33.3 mg of radium.
 Delivers a dose of 5500 mg-hrs of radium over a period of five
days at dose rate of 45R/h.

28. 28
 The historical Paris
system. Typical radium
application for a
treatment of cervix
carcinoma consisting
of : 3 individualized
vaginal sources (one in
each lateral fornix and
one central in front of
the cervical os), 1
intrauterine source
made of 3 radium
tubes (in so called
tandem position).

29. 29
DRAWBACKS OF PARIS AND STOCKHOLM
SYSTEMS
 Long treatment time
 Discomfort to the patient
 No dose prescription

30. 30
MANCHESTER SYSTEM
Developed by Todd & Meredith in 1938
NEED:
1. Recognized that unique dosage system was
necessary.
2. Defined the treatment in terms of dose to a point.
3. Stressed the importance of constant dose rate.
4. Introduced reproducible technique which could
aim at better tumour control and less radiation
morbidity.
5. Defined point A and point B.

31. 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 above from the mucosa of the
lateral vaginal fornix
 Revised point A: 2 cm superior from lower end of
central radium tube(external cervical os) and 2 cm
lateral from uterine canal(1953).

33. 33
POINT B
 Same level as point A but 5 cm from
midline
 Proximity to obturator LNs
 Dose ~15-20 % of the dose at point A
POINT H
A line connecting middle of sources in
vaginal ovoids on A-P radiograph and
move 2 cm plus the radius of ovoid
superiorly along the tandem from
intersection of this line with intrauterine
source line and then 2 cm lateral on either
side of the tandem (IJROBP.48(1),201-
11,2000).

34. 34
POINT P:
 Used by Mallinckrodt Institute of Radiology
System to specify minimum dose to pelvic lymph
nodes.
 It is 6 cm to Rt and Lt of patient midline in same
plane as of classical point A.

35.  Localisation of bladder and rectum performed using
radiographs with contrast media in the bladder and
rectum.
 Maximum dose to bladder and rectum should be, as
far as possible, less than the dose to point A(80% or
less of the dose to point A).

36. INTERNATIONAL COMMISSION
ON RADIATION UNITS AND
MEASUREMENTS SYSTEM

37.  The ICRU introduced the concept of reference volume
enclosed by the reference isodose surface for
reporting, communicating and comparing
intracavitary treatments performed in different
centers regardless of the applicator system, insertion
technique, and method of treatment prescription
used.

38.  Specifically, ICRU Report No. 38 recommended that
the reference volume be taken as the 60-Gy isodose
surface, resulting from the addition of dose
contributions from any external-beam whole-pelvis
irradiation and all intracavitary insertions.

39.  The ICRU proposed that a pear-shaped reference
volume be described in terms of its three orthogonal
maximal dimensions: height (dh), width (dw), and
thickness (dt), measured in the oblique coronal and
sagittal planes containing the intrauterine sources.

41. DATA NEEDED FOR REPORTING
ICRU
 Description of the technique used.
 Total reference Air Kerma
 Description of the Reference Volume – 60 Gys.
Dimensions of the reference volume.
 Absorbed dose at reference points
Bladder point
Rectal point
Lymphatic trapezoid of fletcher
Pelvic wall points
 Time dose pattern

42. 42
BLADDER POINT
 Frontal radiograph:- Center of the balloon
 Lateral radiograph:- At the posterior surface on a
line drawn anteroposteriorly through the center of
the balloon.

43. 43
RECTAL POINT
 Frontal radiograph:- Mid point of ovoid sources or lower end
of intrauterine source
 Lateral radiograph:-Line drawn from the middle of ovoid
sources, 0.5cm behind the posterior vaginal wall.

44. 44
Lymphatic Trapezoid Of Fletcher

45. Pelvic wall points
 AP X-ray:- At the intersection of a horizontal tangent
to superior aspect of acetabulum and a vertical line
touching the medial aspect of acetabulum
 Lateral view:- Highest middistance points of the right
and left acetabulum.

46.  Time dose pattern
 Duration and time sequence of the implant should be
recorded.

47. THANK YOU