The dose selected to define the reference volume shall imply a consensus at an international level (or at least between the involved centres). In EBRT, as dose distribution is homogeneous hence, “reference point for reporting” is selected in the centre of the PTV. But this is not the case in I/C brachytherapy because of the steep dose gradient especially in the vicinity of the radioactive sources
With imaging, one may visualize the tumor volume and conform dose to the volume
(but more often closer than the ICRU bladder dose).
Conventional Brachytherapy in carcinoma cervix
Conventional Brachytherapy In
• Brachytherapy is a type of radiation treatment in which
small, encapsulated radioactive sources are arranged in a
geometric fashion in & around tumor.
– It delivers very high dose of radiation to tumor
– Sparing normal tissue
– Dose delivered in short duration as compared to External beam
BRACHYTHERAPY in Cervix
• Brachytherapy plays vital role in treatment of ca cx. &
is mainly applied as an intracavitary procedure in
selected cases complemented by interstitial implants.
• It consists of positioning specially designed applicators
bearing sealed radioactive sources into a body cavity in
close proximity to the target tissue.
• I/C applications are temporary that are left in the
patient for a specified time to deliver prescribed dose.
WHY I/C BRACHYTHERAPY
• Uterine cx. is ideally suited for I/C brachytherapy
– High tolerance of cervix ,uterus & vagina
– It is accessible organ hence Brachytherapy can be practised
– The endocervical canal & vaginal vault form a suitable
vehicle to carry rigid applicators with radioactive sources.
– These applicators can be used with minor modifications in
ADV. OF I/C
• High dose of radiation is delivered in shortest time.
• Cervix receives 20,000 – 25000 cGys.
• Uterus receives 20,000- 30000 cGys
• Vagina receives 10,000 cGys.
such high doses can’t be delivered by any technique of EBRT.
• Best long term control is achieved
• Sharp Fall off of dose and hence less dose to the normal
• Less late radiation morbidity .
• Preservation of normal anatomy.
• Better sexual functional life.
1898 : Discovery of Radium by Marie Curie in Paris.
1903 : Margaret Cleaves, a New York physician
described inserting Radium into the Uterine cavity
of a patient with Ca Cervix.
1908 : I/C brachytherapy started in Vienna
1910 : I/C brachytherapy started in Stockholm
1912 : I/C brachytherapy started at Paris.
1930 : Todd & Meredith developed Manchester system
1960s - After loading technique ( Helneski)
1970- Paris System of dosimetry for Interstitial Brachytherapy evolved
1975- Remote Control LDR ( Cs-137)
1985- HDR Introduces( Ir-192 & Co-60) & ICRU-38 Published
- Concept of Volume in place of point introduced
- Joshlin Published data about the discrepancies in point A & B
1990s - Miniaturized stepping source with optimization
• The historical dosimetric systems were developed when
computer treatment planning and dose computations were not
• Term ‘system’ specifies a set of rules for
– Geometrical arrangement of a specific set of radio isotopes in a
– To obtain suitable dose distributions over the volume to be treated.
– It specifies treatment in terms of the dose, time and administration
– A specified set of tables to allow, reproducible and easy calculation
in most of the encountered clinical scenarios.
– A system ensures safety and is based on clinical experience.
• Fractionated (2-3 #s) course over a period of one month.
• For a period of 22 hours each.
• Separated by 1-3wks
• This system used
– Intravaginal boxes made up of silver or gold
– The intrauterine tube made up of flexible rubber.
– These were not fixed together
• Unequal loading of Radium
– 30 to 90 mg of Radium was placed inside the uterus
– While 60 - 80 mg were placed inside the vagina
• A total dose of 6500 -7100 mg -hrs was prescribed out of
which 4500 mg Ra was contributed by the vaginal box.
• Single application of Radium for 120hrs (5-
• In this system, almost an equal amount of Radium
was used in the uterus and the vagina.
• The system incorporated
– Two cork colpostats (cylinder) with 13.3mg
Radium in each
– An intrauterine tube of silk rubber with 33.3mg
• The intrauterine sources contained three
radioactive sources, with source strengths in the
ratio of 1:1:0.5.
• The colpostats contained sources with the same
strength as the topmost uterine source
• Designed to deliver a dose of 7000 - 8000 mg hrs
over a period of 5days (45R/hr) (5500mg/hr)
• Done in mg-hr i.e. simple mathematical product of mg of
Radium times the duration (in hours) of the implant.
• It was easy to use.
• The dose prescription was entirely empirical due to the lack
– knowledge about the biological effects of radiation on the
normal tissues and the tumor
– understanding about the dose, dose distribution and the duration
• Only applicable when both tandem & ovoids are used &
sources are loaded in a rigidly prescribed manner.
• Long treatment time, discomfort to the patient
• Dose prescription method was empirical. Both systems specified
dose in mg-hour.
• Does not give any information about dose distribution.
• When used in conjunction with EBRT, overall radiation treatment
can’t be adequately defined
• Dose specification method lacks the information on
– Source arrangement
– Position of tandem relative to the ovoids
– Packing of the applicators
– Tumour size, and
– Patient anatomy.
• With the use of this dose prescription method dose to important
anatomical targets could not be quantified adequately.
• Ignored the importance of tolerance of different critical organs to
• The Manchester system is one of the oldest &
extensively used systems in the world.
• Developed by Todd & Meredith in 1930 & was in
clinical use by 1932.
• This system was initially developed for radium tubes,
but was easily adapted to different afterloading systems.
• Manchester system was based on following principles:
• To define the treatment in terms of dose to a point. To be
acceptable this point should have following criteria :
– It should be anatomically comparable from patient to patient.
– Should be in a region where the dosage is not highly sensitive to small
alteration in applicator position.
– Should be in position that allows correlation of dose with clinical effects
• To design a set of applicators and their loading (with a given
amount of radium), which would give the same dose rate
irrespective of the combination of applicators used.
• To formulate a set of rules regarding the activity, relationship &
positioning of the radium sources in the tandem & vaginal ovoids
to achieve desired dose rate.
• Todd & Meredith defined a point in
paracervical triangle where the uterine
vessels cross the ureter as point A.
• Point A is defined as a point 2cm. lateral
to the center of the uterine canal and 2
cm. superior to the mucosa of the lateral
fornix, in the plane of the uterus.
• Now point A is defined as a point 2cm
above the distal end of lowest source in
cervical canal & 2cm lat. to centre of
• Although point A is defined in relation to important
anatomic structures, these can’t be visualized on a
• The keel is placed at the external os. It serves as
important reference point as it can be visualized on
• Dose at point A showed a correlation with local control
and the incidence of late normal tissue toxicity in the
• Point B is defined 2cm above external os & 5 cm laterally to
• Represents dose to the pelvic wall, obturator L.N.
• The dose at point B is approx. 25 -30% of the dose at point A.
• Dose to point B, depends little on the geometric distribution of
radium, but on the total amount of radium used.
DOSE LIMITING STRUCTURES
• Vaginal mucosa
• Rectovaginal septum
– No more than 40% of total dose at point A could be delivered safely
through the vaginal mucosa.
– The rectal dose should be 80% or less of the dose at point A; this
rectal dose can usually be achieved by careful packing.
• In this system, the dose distributions were not calculated for
• Applications outside the standard variations were corrected
for, but the majority of patients had applicators in place for a
• The Manchester system was a time system based on the use of
APPICATOR IN MANCHESTER
• Similar to that used in Paris system
• It had a pair of ovoids & an intrauterine tube
• The intrauterine tube was made up of the thin rubber ( to prevent
excessive dilatation of the cervical canal)
• These tubes were available in three separate lengths
• In order to accommodate 1, 2 or three Radium tubes (2 cm long) in line
I.U.tubes were closed at one end, and had a flange at the other end so
that when packed into position, the uterine tube did not slip out during the
• Used in pairs, one in each lateral fornix
• The shape of ovoids mimics the shape of isodose curves
around a Radium tube having "active length" of 1.5 cm.
• The ovoids were designed to be adaptable to the different
vaginal capacity, with diameter of
– 2 cm
– 2.5 cm
– 3 cm
• The largest ovoid are placed in the roomiest vagina in order
to achieve the best lateral dose throw off
• Apart from ovoids & I.U.tubes spacers or washers were used
– To maintain the distance between the ovoids
– To help in their fixation
• Spacer was used to give the largest possible separation b/w the
ovoids so that the dose could be carried out as far laterally as
• It maintained a distance of 1cm b/w the ovoids.
• Manchester applicators do not incorporate rectal
• Hence gauze is packed firmly and carefully
– behind the ovoids,
– anteriorly b/w the ovoids and the base of the bladder,
– and around the applicator tubes down to the level of the introitus
• Packing helps to
– keep the applicators in position
– to reduce dose to bladder and anterior rectal wall.
• The point A should receive the same dose rate, irrespective of the
combination of applicators used.
• Not more than one third of the total dose to point A should be
delivered by the vaginal ovoids. So that tolerance of vagina mucosa is
• Standard or ideal loading is 60-40 i.e. 60% of the dose to point A is
contributed by intrauterine sources while 40% is contributed by
• Total Dose to point A : 8000 R
– Total number of applications : 2
– Total time for each application : 72 hrs
– Total time : 144 hrs
– Dose rate desired : 55.5 R /hour to point A
• Amount of radium to be used was defined in terms of units.
• 1 unit = 2.5 mg of radium filtered by 1 mm platinum.
• The loadings were specified in terms of integral multiples of this unit.
• Total dose at point A using different combinations of
I.U tube & ovoids :
– Large tube with large ovoid and washer : 57.5 R
– Large tube with large ovoid and spacer: 56.9 R
– Large tube with small ovoid and washer: 57.6 R
– Medium tube with small ovoids and spacer: 57.3 R
• The variations were thus within 1.5% range.
• For reliable and relevant comparison of different
methods and their clinical results ICRU 38 recommends
a common terminology for prescribing recording and
reporting I/C Brachytherapy applications.
• The ICRU recommends a system of dose specification
that relates the dose distribution to the target volume,
instead of the dose to a specific point
• The dose is prescribed as the value of an isodose
surface that just surrounds the target volume.
• Description of technique
• Time dose pattern (application duration)
• Description of reference volume
• Dose at reference points
Description of the Technique
• Minimum information should include the
– orthogonal radiographs of the application.
– Source used (radionuclide, shape and size of source, and filtration)
– applicator type
– Loading pattern
– Simulation of linear source for point or moving sources
– Applicator geometry (rigidity, tandem curvature, vaginal uterine
connection, source geometry, shielding material)
DOSE AT REFERENCE POINTS
• The dose to bladder and rectum depends on the
distribution of sources in a given application.
• The maximum dose to bladder and rectum should
be less than 80% of the dose to point A
• The localization of bladder and rectum can be
performed using radiographs taken with contrast
media in the bladder and rectum.
• ICRU recommends :
o Foley balloon filled with 7 cm3
radiopaque fluid and pulled down against
• On a lat. radiograph reporting dose at a
point at posterior surface of Foley balloon
on AP line through centre of balloon.
• On AP radiograph, reference point is
taken at the centre of the balloon
• The dose is calculated at a
point 5 mm posterior to
(opacified) vaginal cavity
along an AP line midway
between vaginal sources.
• On the frontal radiograph, this
reference point is taken at the
intersection of (the lower end
of) the intrauterine source
through the plane of the
• Lymphatic trapezoid represents
dose at lower Para-aortic ,
common and external iliac L.N.
• A line is drawn from S1-S2
junction to top of symphysis,
then a line is drawn from middle
of this line to middle of ant.
aspect of L4
• A trapezoid is constructed in a
plane passing through transverse
line in pelvic brim plane and
midpoint of ant. aspect of body
PELVIC WALL REFERENCE POINTS
• The pelvic wall reference point,
represents absorbed dose at the distal part
of the parametrium and at the obturator
• Reporting dose at reference points related
to well defined bony structures & L.N.
areas is particularly useful when I/C BT
is combined with EBRT
• On a AP radiograph, pelvic-wall reference
point is located at intersection of following
– a horizontal line tangential to the highest
point of the acetabulum,
– a vertical line tangential to the inner
aspect of the acetabulum.
• On a lat. radiograph, the highest points of
the right & left acetabulum, in cranio -
caudal direction, are joined & lateral
projection of the pelvic-wall reference point
is located mid-way b/w these points.
• Volume encompassed by the
reference isodose, selected and
specified to compare treatments
performed in different centres using
• ICRU (43) recommends 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 I/C insertions.
– Height h,
– Width w, and
– Thickness t.
– and their product should be reported
• The Treated Volume is the pear and banana
shape volume that received (at least) the dose
selected and specified by the radiation
oncologist to achieve the purpose of the
treatment e.g. tumour eradication or palliation,
within the limits of acceptable complications
• The irradiated volume is the volume,
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 is useful for
interpretation of side effects outside the treated
volume and for purpose of comparison.
• Applicators are small-caliber tubes that are inserted into
body cavities to hold the brachytherapy sources in
clinically defined configurations.
• The applicators include
– A tandem to be inserted into the uterus
• with different lengths that allow for adaptation according to the
individual anatomy (with a fixed uterine flange)
• Angled at varying degrees to the line of the vaginal component
• The deliberate angle in the tube draws the uterus, in most patients,
into a central position in the pelvis away from the pouch of
Douglas, the sigmoid colon, and the anterior rectal wall.
– Two ovoids, to be positioned in the vaginal vault abutting the
• Applicators used to insert intracavitary sources
in the uterus and vagina included
– Rubber catheters and ovoids developed by French
– Metallic tandems and plaques designed in Sweden
– Thin rubber tandems and ovoids of the
– Fletcher (1953) designed a preloadable colpostat,
which Suit et al. (1963) modified and made after
• IDEAL CHARACTERISTICS of applicators
– It should have a fixed geometry.
– It should be made of rigid material as fixed & rigid applicators attain and
hold better geometry of the insertions
– Lightweight (ideally 50- 60gm but should not be more than 100gm) for the
– capable of easy sterilization.
– Applicators should be of inert material that is not adversely affected by
– There should be minimal attenuation of radiation by the walls of the
applicators i.e. it should not produce its own characteristic radiations
– Vaginal ovoids should be perpendicular to the long axis of vagina to avoid
more dose to rectum and bladder.
– I.U. tube should be angulated
• Based on Manchester System
• Stainless steel
• Cylindrical ovoid
• Rectal shield
• Preloaded but modified by Suit
for after loading
– Presence of shielding lead
to uncertainty in dosimetry.
– Cylindrical caps lead to
non-uniform doses to
vaginal mucosa. Fletcher - Suit- Delclos
applicator for afterloading with Ir-192
• Ovoids are hemispherical in
• Three ovoid diameters &
various tandem lengths are
• The radioactive sources are
placed parallel to the long axis
of the bladder & rectum
• Thus delivering a higher dose
to these organs
• Fixed geometry applicator
• Desired dose can be delivered
around area of interest
• Easy & accurate dosimetry
• Less rectal dose because of
• Perineal plate which helps to
maintain fixed geometry of
– Bladder complications are more as it
receives higher dose due to more
• Modern after loading applicator
that mimics classical Manchester
• I.U. tube with different lengths
graduated in centimeters (4&
• The vaginal ovoids are of ellipsoid
shape (large, medium, small, half)
• These tubes are held together and
their relative positions fixed by a
clamp ensuring an ideal physical
• Based on Stockholm technique
• Intrauterine tubes are of different
lengths & angulations
• Ring is available in different
diameters (26, 30, 34mm)
• Acrylic caps cover the ring tube to
reduce dose to vaginal mucosa.
• The ring and the intrauterine tube
are fixed to each other with a screw.
• A rectal retractor helps in pushing
rectum so that it receives less dose.
• Adv. of ring applicator:
– Fixed geometry
– Interrelationship b/w ovoids is
– Customized planning can be done
• Use longest tandem that the
patient's anatomy can
• Increasing the tandem length
increases the point B (lateral
parametrium and pelvic lymph
nodes) contribution relative to the
uterine cavity surface dose
• The radioactivity near the ends of
the long tandem contributes little to
the surface dose (because of
inverse-square law), whereas each
tandem segment makes roughly
equal contributions to points remote
from the applicator.
• Colpostats /ovoids with largest clinically indicated
diameter should be used to deliver highest tumor dose
at depth, for a given mucosal dose.
• As colpostat diameter increases from 2 to 3 cm, the
vaginal surface dose decreases by 35% relative to the
dose 2 cm from the applicator surface; This is simply a
consequence of increasing the source-to-surface
• The geometry of the insertion must prevent under
dosing around the cervix
• Sufficient dose must be delivered to the Para cervical
• Tolerance of vaginal mucosa, bladder and rectum must
• Tandem -1/3 of the way b/w S1
–S2 and the symphysis pubis
• The tandem -midway b/w the
bladder and S1 -S2
• Marker seeds may be placed in
• Ovoids should be against the
cervix (marker seeds)
• Tandem should bisect the
• The bladder and rectum should
be packed away from the
• The tandem should be in the midline or
as nearly as possible equidistant from the
lateral pelvic wall
• The vaginal colpostats should be
symmetrically positioned against the
cervix in relation to the tandem
• The ovoids should fill the vaginal
fornices, add caps to increase the size of
the ovoids if necessary
• The ovoids should be separated by 0.5 –
1.0 cm, admitting the flange on the
• The axis of the tandem should be central
between the ovoids.
• Computerized dose optimization cannot
make up for a poor applicator position.
• Pt is anaesthesitized.
• Patient is in lithotomy
• Perineal area is
• Potential options include general, spinal or iv conscious
• With IV conscious sedation – levator muscle tightens
making application difficult.
• Conscious sedation with Iv fentanyl and midazolam is
preferred in most patients.
• General or spinal anesthesia result in complete
immobilization during insertion and treatment which may
be 2-4 hr
• Applicator set is check
for integrity and
• Dilatation of the cervix
with standard tooling.
• Hegar uterine dilators are used to dilate the os
to 6 mm.
• Tandem length is usually 6–8 cm but its
variable from patient to patient.
• For tandems >8 cm, avoid loading/active
source at end to protect small bowel.
• Tandem should be located centrally between
the ovoids on the AP view and bisect the
ovoids on the lateral view.
• Correct length of IU-tube &
ovoids are selected
• Inserted one by one and
attached to fixing
• To determine the rectal wall
on CT or radiograph a radio
opaque marker is inserted
• After insertion of applicator
gauze packing is done
behind the ovoids to push
rectum and bladder away
reducing the dose to these
• After procedure orthogonal radiographs are taken to
check applicator geometry.
• Stage IA (microinvasive) tumors
– Treated with Brachytherapy alone
– LDR dose is approximately 60 Gy in one insertion or
75 to 80 Gy in two insertions to point A
– with HDR an equivalent dose, with one or two
fractions per week.
• A reasonable target is to give to Point A
– 65-75 Gy for Stage IA disease
– 75-85 Gy for IB - IIB
– 85-90 Gy for III – IVA
For determination of target
• point based dosimetry
• point A may overestimate or underestimate the tumor dose based on
• no optimization:
• tumor coverage relies on tumor volume at time of BT, larger tumors
requiring greater optimization to be adequately covered by the prescribed
• Kim et al** found that dose to point A was significantly lower than
the D90 for HR-CTV calculated using 3D image-based optimization
• dose escalation not possible
• *Kim RY, Pareek P. Radiography-based treatment planning compared with computed tomography (CT)-based treatment planning for
intracavitary brachytherapy in cancer of the cervix: analysis of dose-volume histograms. Brachytherapy 2003;2:200–206.
• **Kim H, Beriwal S, Houser C, et al. Dosimetric analysis of 3D image-guided HDR brachytherapy planning for the treatment of
cervical cancer: is point A-based dose prescription still valid in image-guided brachytherapy? Med Dosim 2011;36:166–170.
to analyze dosimetric outcome of 3D IGBT &compare dose coverage of HRCTV to
traditional Point A dose.
• N=32patients (stage IA2-IIIB cervical cancer) treated with IGBT
• dose: 5.0-6.0 Gy/# ×5 fractions.
• delineation of CTV as per GYN GEC/ESTRO guidelines.
• D90 for HRCTV was 80-85 Gy,
• D2cc of bladder, rectum, and sigmoid was limited to 85 Gy, 75 Gy &75 Gy.
• The mean D90 for HRCTV was 83.2 ± 4.3 Gy SD significantly higher (p
<0.0001) than mean value of Point A dose (78.6 ± 4.4 Gy).
• The dose levels of the OARs were within acceptable limits
• Dose to Point A was found to be significantly lower than the D90 for HRCTV
• Image-based 3D brachytherapy provides adequate dose coverage to HRCTV,
with acceptable dose to OARs in most patients.
• ICRU bladder point:
• Foley Bulb in the trigone of bladder with7 cc of dilute contrast is used
• only report point estimates.
• wide range of anatomic variations in bladder points along he length of implant
• doses may be different at bladder base & neck, multiple points have to be taken
• ICRU point may underestimate maximum doses to the OAR, in particular
for the bladder
• ICRU bladder volume point does not represent the hottest part of the bladder that
usually falls about 2 cm superior. highest dose often is about 2-4 times the dose
at the bulb
For determination of OAR
ICRU rectal point:
• rectal markers is used which tend to lie on posterior wall of rectum while the
anterior wall is at greater risk.
• Stiff markers can move rectum, flimsy ones are difficult to push deep.
• ICRU rectal point doesn’t usually represent the maximum rectal does, which,
again often is 2-4 cm cephalad.
• maximum does is up to 3 times the ICRU point
None of this localizes the superior bowel - an organ very much at risk.