Two dimensional varsus three dimensional radiation treatment planning in pelvic malignancies

1. Two Dimensional Versus Three
Dimensional Radiation Treatment
Planning In Pelvic Malignancies:

2. CANCER:
 Any definition must embody two Characteristics:
1. The property of uncontrollable growth of cells
originating from normal tissue.
2. The property of damaging the host by means
of local tissue invasion and/or distant spread
(metastasis).
 Cancer is a group of diseases characterized by
uncontrolled cellular growth with local tissue
invasion and/or systemic metastasis.

3. CONTD:
 Metastasis- spread of cells, from a primary
tumor via the lymphatic and circulatory systems
to a distant body part, where cells give rise to
another cancer.
 Micro metastasis -metastasis too small to be
detected by conventional diagnostic methods.
 Tumor- abnormal growth that can be benign or
malignant.

4. History of Radiation
Physics in Medicine
Pierre Curie (1859-1906)
Marie Curie (1867-1934)
Wilhelm Conrad Roentgen
(1845-1923)
Ernest Rutherford
(1871-1937)

5. RADIATION ONCOLOGY:
The discipline of human medicine
concerned with the generation,
conservation and dissemination of
knowledge concerning the causes,
prevention and treatment of cancer and
other diseases involving special expertise
in the therapeutic applications of ionizing
radiation.

6. RADIATION THERAPY:
 It is a clinical modality dealing with use of
ionizing radiations in the treatment of
patients with malignant neoplasia (and
occasionally with benign disease).

7. RADIATION:
 ELECTROMAGNETIC
RADIATION
. X-Rays
. Gamma Rays
•PARTICLES
•Neutrons
•Protons
•He IONS/α Particles
•Negative pions
•Heavy ions
•Carbon
•Neon
•Argon

8. HOW RADIATION WORKS?
 Biologic effects of ionizing radiations are
largely the result of DNA damage.
 General forms of DNA damage are base
damage, DNA-protein cross links, single-
strand breaks, double strand breaks and
complex combinations of all of these
resulting in cell death.

9. Critical Target is DNA
Cell
Nucleus contains DNA
DNA is packaged on chromosomes
DNA double stranded helix

11. AIM OF RADIOTHERAPY:
 To deliver a precisely measured dose
of radiation to a defined tumor volume
with as minimal damage as possible to
surrounding healthy tissue, resulting
in eradication of the tumor, a high
quality of life, and prolongation of
survival at a competitive cost.

12. PLANNING & CONCEPT OF
RADIATION THERAPY:
 What is the indication?
 What is the goal of radiation therapy?
 What is the planned treatment volume?
 What is the planned treatment technique?
 What is the planned treatment dose?

13. RADIOTHERAPY:
 Radical or Palliative intent.
 Localized form of treatment.
 Uses radiation to damage DNA within the
cancer cells.

14. INDICATIONS:
 Localized tumors-skin, cervix,
endometrium, breast, larynx, Hodgkin’s
disease etc.
 High-risk surgical candidates.
 Palliative-pain relief from bony
metastases, as haemostatic agent, in
relieving malignant obstruction etc.
 Radiosensitizer with chemotherapy.

15. TECHNIQUES IN
DELIVERING PELVIC
IRRADIATION:
 External beam- Teletherapy.
 Internal beam- Brachytherapy.

19. IDEAL RADIATION TREATMENT
PLANNING IN PELVIC
MALIGNANCIES:
 The dose to the treatment volume should not exceed
that to any other area by at least 20%.
 The dose to normal surrounding organs should be
kept below their tolerance dose.
 The integral dose viz total dose to patient should be
kept to a minimum.
 The dose throughout the target volume should be
uniform to within 5%.
 The treatment volume should be as near as possible
be the same as the target volume in position, size and
shape.

20.  Earlier Rad was used.
 Gray (Gy) is the SI unit.
 Represents the absorption of 1 joule of
energy per kg of absorbing material.
 1 Gy = 100 Rads.
UNIT OF RADIATION
ABSORBED DOSE:

21.  Whole of radiation is delivered
in weeks in number of small
fractions of dose.
 Each fraction delivered daily 5
days a week.
 Fraction size 180cGy
to200cGy.
 Usually each fraction dose is
delivered in multiple planes.
 60GY/30f/6weeks.
STANDARD TIME DOSE
FRACTIONATION SCHEDULE:

22. With the help of radiotherapy units
especially designed to hold radioactive
source and emit radiation in form of beam.
HOW RADIOTHERAPY IS
DELIVERED:

26. TWO DIMENSIONAL
TREATMENT PLANNING:
 It is simple, easy to do, takes less than an hour
and done generally on only one slice of CT scan.
 The central plane through the target volume is
generally taken as representative for the entire
volume.
 Consists of single beam from one to four
directions, in pelvic malignancies most
commonly four fields i.e. “Box technique” is
used.

29. WHAT IS THE NEED FOR
THREE DIMENSIONAL
PLANNING?
 In pelvic malignancies we can not escalate
doses beyond 70 Gy in 2-D planning while
doses approaching 80 to 100 Gy are
needed to sterilize the size of epithelial or
mesenchymal tumors frequently seen with
primary tumors.

30. CONTD:
 Sharp increase in late rectal and urinary
bladder injury above 70 Gy .
 Thus to get higher doses as well as in
diminishing acute and late complications,
the need for 3- D planning arises.

31. THE TOLERANCE DOSE OF
PELVIC ORGANS:
 Radiation tolerance dose of normal pelvic
structures is as :
 The cervix and body of uterus tolerate very high
dose of radiation 200-300 Gy.
 Mucosa of vagina tolerates upto 160-200 Gy.
 Rectosigmoid and large bowel upto 50-60 Gy.
 Small bowel upto 45-50 Gy.
 Urinary bladder upto 55-60 Gy.

32. 3-D TREATMENT
PLANNING:
 It is very complex process, difficult to do, very time
consuming ( takes many days for the final plan) and done
on multiple CT slices of area of interest (up to 50 slices).
 Refers to a process in which image based planning is
performed with goal of conforming the prescription dose
to target volumes while lowering or minimizing dose to
surrounding normal tissue. Three dimensional
localization implies localization in three planes i.e.
Coronal, saggital and axial planes.
 Doses up to 90 Gy can be given by 3-D planning.

35. STEPS IN 3-D PLANNING:
 Preplanning and localization of tumor.
 Computed tomographic (CT) imaging.
 Central structures, tumor and target volume
delineation on CT slices.
 Designing beams and field shaping with the help
of Beam's eye view and Room's eye view
display.
 Dose calculation.
 Plan optimization and plan evaluation.
 Treatment documentation.
 Plan and treatment verification.

36. Photo Album
by Dr.Rakesh

38. DELINEATION OF TARGET VOLUMES
AND NORMAL TISSUES/ORGANS AT RISK:
 Done according to standard target volumes as per
defined by ICRU Report no.50 and later modified in
Report no.62.
1. GROSS TUMOR VOLUME (GTV):
2. CLINICAL TARGET VOLUME (CTV):
3. INTERNAL TARGET VOLUME (ITV):
4. PLANNING TARGET VOLUME (PTV):

39. ITV
CTV
Tumor
(GTV)
Areas/volume of tissue to be
treated by radiation:
PTV
Treated volume
Irradiated volume

40. CONTD:
 GROSS TUMOR VOLUME (GTV):
– Includes all known gross disease including
abnormally enlarged regional lymph nodes.
– Is the gross extent of growth as determined by
palpation or imaging studies.
 CLINICAL TARGET VOLUME (CTV):
– GTV with surrounding tissue which is
suspected to be tumor i.e. sub clinical
disease.

41.  INTERNAL TARGET VOLUME (ITV):
CTV+ a margin for physiological movements and
variation in size, shape and position in
corresponding coordinate system (IM).
 PLANNING TARGET VOLUME (PTV):
CTV + IM + set-up margin for patient
movement and set-up uncertainties.
In 3-D planning PTV is the volume around
which planning is done.

42.  TREATED VOLUME: An additional margin is
added around target volume to allow for limitation of
the treatment technique. Minimum tumor dose should
be represented by an Isodose surface which
adequately cover PTV.
 IRRADIATED VOLUME: Volume which receives
a dose considered significant in relation to normal
tissue tolerance (e.g. 50% of specified target dose).
These volumes are generally for plan
optimization and plan evaluation.
CONTD:

43. Planning organ at risk volume
(OAR):
 A safety margin is added in organ at risk
volume to compensate its internal movement and
set-up to define planning organ at risk volume.
 Organs at risk need adequate protection. In our
study organs at risk were urinary bladder and
rectum (except in cases of ca bladder and
rectum).

49. MATERIALS AND
METHODS:
 30 histopathologically proven cases of
pelvic malignancies were included .
 Radical radiotherapy was the intention.
 15 pts. were of ca cervix.
 7 pts. were of ca prostate.
 6 pts. were of ca urinary bladder.
 2 pts. were of ca rectum.

50. CARCINOMA CERVIX:
 Commonest malignancy of an individual
organ in India.
 Abnormal vaginal bleeding is commonest
symptom.
 Radiotherapy is considered as an
excellent treatment modality in all stages
of invasive Ca Cx . Though early stage
low volume disease are treated equivocally
by either surgery or RT.

51. CONTD:
 External beam radiotherapy is usually given
prior to Brachytherapy.
 It improves geometry of pelvic structures for
ICBT, here we are performing HDR ICBT by
state of art machine Microselectron HDR
Machine by Nucletron.
 Sufficient dose is given to central disease part
such as vagina, cervix and uterus. 50 Gy by Ext.
RT followed by 2 or more sessions of HDR
ICBT.

53. CONTD:
 Two parallel opposed Anterior/Posterior or 4
field “box technique” is used.
 Upper border-Lower border of L4 vertebra.
 Inferior border-2cm below obturator foramen.
 Lateral borders-2cm lateral to true pelvis.
 Anteriorly-1cm above the pubic symphysis.
 Posteriorly line drawn at S-2-3 junction sparing
½ of rectum.
 Common field’s dimensions are 15-15 or17-17
cms. by AP/PA.

54. CARCINOMA PROSTATE:
 Commonest malignancy in men over 65 yrs. of
age.
 Most of these present in advanced disease.
 Treatment options include: Observation, Radical
prostatectomy, Radical radiotherapy & hormonal
therapy.
 Radiotherapy can be by Ext. RT or
Brachytherapy or a combination of two.

57. CARCINOMA U. BLADDER:
 Higher incidence in industrialized nations.
 Exposure to dyes, rubber, leather, paint,
organic chemicals is associated.
 Cigarette smoking is most important
causative factor.
 Radical cystectomy/ concomitant
chemoradiation done in advanced cases.

58. CARCINOMA RECTUM:
 Colorectal cancer is the fourth most
frequent site for a primary malignant
tumor.
 Radical surgery is preferred modality.
 Radical radiation is given in adjuvant
settings.
 Palliative RT given in very advanced
cases.

59. FIELD PLACEMENTS FOR CA
U.BLADDER & RECTUM:
 Whole pelvic irradiation is given.
 Anterior field placements are almost
similar to as in Ca Cx , lateral fields
are modified depending upon the
malignancy.
 Four field technique is preferred.

60. TREATMENT PLANNING
AND EVALUATION:
 CT scans (plain/contrast)of abdomen and pelvis
were performed for all these 30 patients.
 CT data of each pt. was transferred to the
Theraplan 500-3D planning computer in Dept. of
Radiotherapy.
 Delineation of different target volumes/normal
tissues/organs at risk was done.
 Two dimensional as well as three dimensional
planning was done for all these patients.
 All plans were normalized to grid maximum
value.

61. PLAN EVALUATION:
 Isodose distribution of plans for each slice were
obtained & compared for PTV.
 Cumulative as well as differential Dose Volume
Histograms (DVH) were also made using
standard parameters viz. V95, D95, D05 & D5.
 DVH represent the total volume which has
received a given dose and displays dose
distribution too.

62. PARAMETERS USED IN
DVHs:
 V95: defined as the percentage of target
volume receiving 95% of the dose.
 D95: dose to 95% of the target volume.
 D05: minimum dose that 5% of the
volume receives.
 D5: maximum dose to a volume of no less
than 5% of total target volume.

67. CONTD:
 Beam’s eye view as well as Room's eye
view software was used.
 Conformal fields were placed.
 Isodose distribution for both types of
planning techniques were compared.
 Dose volume histograms were calculated
and compared.

70. DVH COMPARISION BETWEEN
2D &3D PLANNING FOR PTV:

71. DVH COMPARISION BETWEEN 2D
&3D PLANNING FOR BLADDER &
RECTUM (OAR):

72. CONCLUSION:
 Three dimensional planning is superior to two
dimensional planning in not only delivering
homogenous dose to target volume but also sparing
critical organs in the vicinity of target i.e. Tumor.
 3-D conformal radiotherapy provides more accurate
three-dimensional definition of the tumor and
distribution of radiation dose that corresponds to the
shape of tumor volume.
 3-D conformal radiotherapy provides accuracy in the
dose application and dose escalation to the targeted
volume.

73. CONTD:
 Precision in the outline of the contours is the
most important task of the radiation oncologist.
It takes a lot of time, great clinical experience,
and high-resolution imaging equipment.
 3-D planning provides maximal approach to the
basic aim of the radiotherapy.
 3-D conformal radiotherapy significantly
reduces to dosing of normal tissues; yet, a great
caution is still necessary because any erroneous
demarcation of pelvic, inguinal or para-aortal
lymph nodes always results in the appearance of
loco regional diseases.