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PRINCIPLES OF
CONFORMAL
RADIATION AND
UTILITY OF 3DCRT
Dr.G.Lakshmi Deepthi
Radiotherapy :
 Principles :
maximum dose to the tumor
least normal tissue toxicity
Conventional planning :
Disadvantages of conventional
planning :
 Lack of 3D visualization of the tumor
 Irradiation of large volumes of normal ...
Conformal radiation therapy
It is described as radiotherapy treatment that
creates a high dose volume that is shaped to
cl...
History :
 CT - Goitein and co workers used CT based
imaging –high quality BEV displays and display
radiographic images from CT –D...
Features of conformal
radiotherapy :
 Target volumes are defined in three dimensions
 Multiple beam directions are used ...
Types Of Conformal
Radiotherapy :
3DCRT :Techniques
aiming to employ
geometric field shaping
alone
IMRT :Techniques to
modu...
What is 3DCRT :
 To plan & deliver treatment based on 3D anatomic
information. such that resultant dose distribution
conf...
Conformation : Automated
Manual
Workflow of Conformal
Radiotherapy :
Step 1 : Positioning :
 comfortable and reproducible.
 Suitable for beam entry with minimum accessories
in beam path.
 ...
Step 1 :Immobilization :
An immobilization device is any device that helps to
establish and maintain the patient in a fixe...
Step 2 : Image Acquisition
 It provides foundation for treatment planning
 Usually more than one imaging modalities are
...
Step 2: Imaging modalities
 Anatomic images of high quality are needed to
accurately delineate target volumes and normal
...
CT Imaging :
 Advantages :
 reconstruction of images in
plane other than that of
original transverse image.
 Bony struc...
MRI Imaging :
 depend on proton density
distribution
 They can be used alone or in
conjunction with CT
Advantages :
 directly generates scan in axial , sagittal, coronal
planes.
 No radiation dose to patient
 Superior to C...
PET CT Imaging :
 enables the collection of both anatomical & biological
information simultaneously
 Advantages :
Earli...
Simulation :
 Virtual simulation is a process in which the
physician uses the digital CT data to define normal
tissue and...
CT Simulator :
• A large bore (75-85cm) to accommodate various
treatment positions along with treatment
accessories.
• A f...
Requisites Of A Planning CT :
 Ct couch should be flat
 Same position
 Immobilization
 Fiducial pointers
 Planning CT...
Image Acquisition :
Patient made to lie in treatment position.
Immobilization devices are used
Radio opaque fiducial are p...
Step 3 :Image Registration :
 Process of correlating different image data sets to
identify corresponding structures or re...
MRI IMAGE
CT IMAGE
Contouring On fused
Image
POINT TO POINT MATCHING
IMAGE FUSION
Applications Of Image
Registration :
 Visualizing CNS structures more clearly seen on MRI
and mapping them to CT image fo...
Step 4 :Image segmentation :
 It is the slice by slice delineation of anatomic
regions of interest.
 CT is the principal...
Volume specification :
 Volume definition is prerequisite
for 3-D treatment planning.
 To aid in the treatment planning
...
Volume specification :
 ICRU 29—1978
Target volume
Treated volume
Irradiated volume
Organ at risk
Hot spot
Target volume :
 Definition : volume containing those tissues that are
to be irradiated to a specified absorbed dose
acco...
 Treatment volume : volume enclosed by the
isodose surface representing minimal target dose.
 Irradiated volume : volume...
VOLUMES :
 Gross target volume
 Clinical target volume
 Planning target volume
 Organs at risk
 Treated volume
 Irra...
ICRU 50-1993
 Well suited for conformal therapy
TARGET VOLUME :
PTV
CTV
GTV
GTV-Gross Target Volume
 Gross demonstrable extent and location of the
malignant growth.
 It consists of :
 Primary tum...
GTV Identification :
GTV Identification--CT
CTV – Clinical Target Volume
2 types of
Subclinical
extension:-
Around the GTV-
CTV I
At a distance
(Regional lymph
node...
 The PTV is a static geometrical concept defined
to select appropriate beam sizes and beam
arrangements.
 It considers t...
Treated volume : (previously treatment volume )
volume enclosed by any isodose surface, selected and
specified by the radi...
ICRU 50
Irradiated
Volume
Treated Volume
PTV
CTV
GTV
ICRU 62- 1999
 Supplement ICRU report 50 –conformal therapy
 different margins to account for Anatomical &
Geometrical u...
SM
IM
CT
V
Internal Target Volume
Planning Target Volume
SM-setup margin
CTV-Clinical target volum
IM-internal margin
PTV :
 Based on published clinical experience
 Van Herk and colleagues –systemic and random errors
on the required margi...
 Coplanar treatment techniques –margins across
plane of treatment and margins orthogonal will be
different .
 PTV overla...
Organs At Risk Classification :
Normal tissue whose radiation sensitivity may
significantly influence treatment planning
&...
Classification Of Organs At Risk
Serial – whole organ is a continuous unit and damage at one point
will cause complete da...
Step 5 :Dose prescription :
 Based on published data and clinical experience
 Prescription is specified as a dose at or ...
Step 6 : Conformal Planning
 Forward Planning :In this places beams into a
radiotherapy treatment planning system which c...
Step 6 :Forward Planning
 Beam arrangement – ability to orient beams in 3D
allows one to develop plans using non coplanar...
 Beam directions that create greater difference
between targets and critical structures are
preferred
 A 2cm margin betw...
Beam Designing: Beam
arrangement
Field multiplicity : less need for high energy beams
Disadvantage :
designing excess numb...
 to get a practical idea about geometry of beam
placement .
 Simulates any arbitrary viewing location in
treatment room....
Beam Designing : Field Shaping
 MLCs are used to shape the field around the PTV.
Placed using Beams eye view (BEV)
 BEV ...
Beam Modeling :
DRR- Digitally Reconstructed
Radiograph
 After beam arrangement, DRR is generated.
 Used for treatment portal design.
 ...
Step 7 :Dose distribution
calculation :
Rectilinear coordinate system affixed to the patient
3D CT image set is typically ...
 CT numbers are not directly used in photon dose
calculations , electron density of the corresponding
tissue are used. Wh...
 Once the parameters are defined, the Treatment
Planning Software generates the dose distribution
 Past – dose calculati...
Plan Optimization And
Evaluation :
 Iterative, interactive approach
 Beam arrangement is done based on review of
DVH and...
Plan Evaluation
The following tools are used in the evaluation of the
planned dose distribution:
• Methods of dose display...
Colour Wash -
Spectrum of colours superimposed
on the anatomic information
represented by modulation of
intensity
Gives q...
Coverage By Slice
 Always verify the anatomical dose distribution slice
by slice, in order to identify where under dosage...
Problems With 3D Dose
Distribution:
 Huge amount of information to assess
 Difficult to quantify visually
 Difficult to...
DVH– Dose Volume Histogram
 gives an idea of the percentage volume receiving
the percentage dose both for the tumor and t...
Differential DVH :
 Is a plot of the volume of a given structure
receiving a dose within a specified dose interval(or
dos...
 It is plot of volume of a given structure receiving a
certain dose.
 Any point on the cumulative DVH curve shows the
vo...
See Dose Statistics :
It provide quantitative information on the volume of the
target or critical structure and on the dos...
Plan Approval :
 uniform dose is delivered to the target volume
(+7% to -5% of prescribed dose)
 Dose to critical struct...
Plan Implementation And
Treatment Verification :
 Once the plan is designed, evaluated, and
approved, documentation for p...
 Transfer plan parameters into treatment machine
record-and-verify system
 Set up (register) the real patient according ...
Clinical Utility 3DCRT :
The possible benefits with 3D CRT in clinical practice
are as follows
 Improved local control
 ...
Patient Selection
Patients most likely to be benefited with this
technique are those who have :
 Tumors in sites with com...
Clinical Areas
Following tumor sites have been extensively
treated with this technique :
 Lung Cancer
 Brain Tumors
 Pr...
Brain Tumors :
PTV
RT TEMPORAL
LT TEMPORAL
BRAINSTEM
LENS
OPTIC NERVE
SPINAL CORD
Ca Lung
Ca Cervix
Role In Prostate Cancer :
 Less bladder and rectum toxicity
 Dose escalation – better disease control
 3DCRT can drastically reduce rectal and bladder
dose (Perez et al)
Conv RT 3DCRT
Bladder > 65Gy ~60% ~34%
Rectum > 65Gy ...
Pelvis Treatments :
 Reduction in small bowel toxicity.
 Prevention of late term ano-rectal toxicity
 Escalation of dos...
Pediatric Tumors :
Results other sites :
 Breast : improves dose coverage and reduces
inhomogeneity, elimination of additional surgical
proc...
Advantages :
 allows for the simulation of the patient's treatment
without their physical presence after the CT scan is
o...
Conclusion :
 Tightening of field margins around image based GTV
with little attention to occult disease, patient motion
...
Thank you…
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3D Conformal radiotherapy

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  1. 1. PRINCIPLES OF CONFORMAL RADIATION AND UTILITY OF 3DCRT Dr.G.Lakshmi Deepthi
  2. 2. Radiotherapy :  Principles : maximum dose to the tumor least normal tissue toxicity
  3. 3. Conventional planning :
  4. 4. Disadvantages of conventional planning :  Lack of 3D visualization of the tumor  Irradiation of large volumes of normal tissue along with the tumor  Higher toxicity and side effects.  2D planning of 3D tumor.
  5. 5. Conformal radiation therapy It is described as radiotherapy treatment that creates a high dose volume that is shaped to closely “Conform” to the desired target volumes while minimizing the dose to critical normal tissues..
  6. 6. History :
  7. 7.  CT - Goitein and co workers used CT based imaging –high quality BEV displays and display radiographic images from CT –DRR’s  End of 1980’s –3D planning systems were developed.  1990’s – 3DTPS became commercially available
  8. 8. Features of conformal radiotherapy :  Target volumes are defined in three dimensions  Multiple beam directions are used to crossfire on the targets.  Individual beams are shaped or intensity modulated to create a dose distribution that conforms to the target volume and desired dose levels.  Use of image guidance , accurate patient setup ,immobilization and management of motion to ensure accurate delivery of the planned dose distributions
  9. 9. Types Of Conformal Radiotherapy : 3DCRT :Techniques aiming to employ geometric field shaping alone IMRT :Techniques to modulate the intensity of fluence across the geometrically-shaped field.
  10. 10. What is 3DCRT :  To plan & deliver treatment based on 3D anatomic information. such that resultant dose distribution conforms to the target volume closely in terms of ◦ Adequate dose to tumor & ◦ Minimum dose to normal tissues.
  11. 11. Conformation : Automated Manual
  12. 12. Workflow of Conformal Radiotherapy :
  13. 13. Step 1 : Positioning :  comfortable and reproducible.  Suitable for beam entry with minimum accessories in beam path.  Positioning devices are ancillary devices used to maintain the patient in a non standard treatment position.
  14. 14. Step 1 :Immobilization : An immobilization device is any device that helps to establish and maintain the patient in a fixed, well- defined position from treatment to treatment over a course of radiotherapy-reproduce the treatment everyday.
  15. 15. Step 2 : Image Acquisition  It provides foundation for treatment planning  Usually more than one imaging modalities are required for better delineation of target volume  Images are acquired for : ◦ Treatment planning ◦ Image guidance and/or treatment verification ◦ Follow-up studies (during & after treatment)
  16. 16. Step 2: Imaging modalities  Anatomic images of high quality are needed to accurately delineate target volumes and normal structures  Modalities : CT MRI US SPECT PET
  17. 17. CT Imaging :  Advantages :  reconstruction of images in plane other than that of original transverse image.  Bony structures  Easily available , inexpensive  4D imaging can be done  Gives quantitative data in form of CT no. (electron density) to account for tissue heterogeneities while computing dose distribution
  18. 18. MRI Imaging :  depend on proton density distribution  They can be used alone or in conjunction with CT
  19. 19. Advantages :  directly generates scan in axial , sagittal, coronal planes.  No radiation dose to patient  Superior to CT in soft tissue delineation such as CNS, head and neck ,sarcoma , prostrate, lymph nodes. Disadvantages :  Insensitive to calcification and bony structures.  longer time  artifacts
  20. 20. PET CT Imaging :  enables the collection of both anatomical & biological information simultaneously  Advantages : Earlier diagnosis of tumour Accurate staging Precise treatment Monitoring of response to treatment  Disadvantages :  Poor resolution  Costly
  21. 21. Simulation :  Virtual simulation is a process in which the physician uses the digital CT data to define normal tissue and target volume contours to reconstruct the patient in three dimensions on a video display terminal.  Images are obtained on a CT simulator as it provides the best geometric accuracy
  22. 22. CT Simulator : • A large bore (75-85cm) to accommodate various treatment positions along with treatment accessories. • A flat couch insert to simulate treatment machine couch. • A laser system consisting of Inner laser External moving laser to position patients for imaging & for marking. A graphic work station
  23. 23. Requisites Of A Planning CT :  Ct couch should be flat  Same position  Immobilization  Fiducial pointers  Planning CT protocols are tumor site dependent and typically 2-5mm thickness and 50-200 slices
  24. 24. Image Acquisition : Patient made to lie in treatment position. Immobilization devices are used Radio opaque fiducial are placed Topogram is generated and VOI is selected Using site dependent protocols images are generated Transfer of images to a 3DTPS or workstation
  25. 25. Step 3 :Image Registration :  Process of correlating different image data sets to identify corresponding structures or regions.  It provides accurate geometric model of the patient ,as well as the electron density information needed for the calculation of the 3D dose distribution that takes into account tissue heterogeneities
  26. 26. MRI IMAGE CT IMAGE Contouring On fused Image POINT TO POINT MATCHING IMAGE FUSION
  27. 27. Applications Of Image Registration :  Visualizing CNS structures more clearly seen on MRI and mapping them to CT image for planning-fusion  Combining functional or biochemical signals from emission tomography onto CT scans for planning purposes.  For organ motion studies  Image guidance  For follow-up studies  Image registration allows computation of cumulative doses from multiple plans done on different image sets for same patient
  28. 28. Step 4 :Image segmentation :  It is the slice by slice delineation of anatomic regions of interest.  CT is the principal source of imaging data used for defining the structures.  Problems with CT : 1.in case of GTV –appropriate CT window and level settings– maximum dimension of gross disease. 2.organ motion
  29. 29. Volume specification :  Volume definition is prerequisite for 3-D treatment planning.  To aid in the treatment planning process & provide a basis for comparison of treatment outcomes.  ICRU reports50 & 62 define & describe target & critical structure volumes.
  30. 30. Volume specification :  ICRU 29—1978 Target volume Treated volume Irradiated volume Organ at risk Hot spot
  31. 31. Target volume :  Definition : volume containing those tissues that are to be irradiated to a specified absorbed dose according to a specified time dose pattern.  Did not address the issue of coordinate system and no definite margin added for different type of uncertainties
  32. 32.  Treatment volume : volume enclosed by the isodose surface representing minimal target dose.  Irradiated volume : volume that receives a dose considered significant in relation to normal tissue tolerance (eg:50% isodose surface).  OAR : radiosensitive organs in or near the target volume whose presence influences treatment planning or prescribed dose.  Hot spot :tissues outside the target area receiving dose higher than 100% of the specified target dose(at least 2cm2 in section)
  33. 33. VOLUMES :  Gross target volume  Clinical target volume  Planning target volume  Organs at risk  Treated volume  Irradiated volume Defined prior to T/t planning During T/t planning Depends on the T/t technique ICRU 50
  34. 34. ICRU 50-1993  Well suited for conformal therapy TARGET VOLUME : PTV CTV GTV
  35. 35. GTV-Gross Target Volume  Gross demonstrable extent and location of the malignant growth.  It consists of :  Primary tumor(GTV primary)  Metastatic lymphadenopathy(GTV nodal)  Other metastasis(GTV M)  If the tumor has been removed prior to radiotherapy then no GTV can be defined.
  36. 36. GTV Identification :
  37. 37. GTV Identification--CT
  38. 38. CTV – Clinical Target Volume 2 types of Subclinical extension:- Around the GTV- CTV I At a distance (Regional lymph nodes)-CTV II To account for uncertainties in microscopic tumor spread
  39. 39.  The PTV is a static geometrical concept defined to select appropriate beam sizes and beam arrangements.  It considers the net effect of the geometrical variations to ensure that the prescribed dose is actually absorbed in the CTV. PTV-Planning Target Volume :
  40. 40. Treated volume : (previously treatment volume ) volume enclosed by any isodose surface, selected and specified by the radiation oncologist as being appropriate to achieve the purpose of treatment. Irradiated volume : tissue volume that receives a dose that is considered significant in relation to normal tissue tolerance. Hot spot : 2cm2  1.5cm2
  41. 41. ICRU 50 Irradiated Volume Treated Volume PTV CTV GTV
  42. 42. ICRU 62- 1999  Supplement ICRU report 50 –conformal therapy  different margins to account for Anatomical & Geometrical uncertainties – internal and setup margin.  Introduces concept of reference points & coordinate systems.  Introduces the concept of conformity index.  Classifies Organs at Risk.  Introduces planning organ at risk volume.  Gives additional recommendations on reporting doses, not only in a single patient but also in a series of patients.
  43. 43. SM IM CT V Internal Target Volume Planning Target Volume SM-setup margin CTV-Clinical target volum IM-internal margin
  44. 44. PTV :  Based on published clinical experience  Van Herk and colleagues –systemic and random errors on the required margins to account for setup error and organ motion – PTV margin = 2.5 Σ + 0.7σ  Asymmetric nature of positional uncertainties eg: prostate  Beam portals– additional margin beyond PTV required to obtain dose coverage because of beam penumbra and treatment techniques.
  45. 45.  Coplanar treatment techniques –margins across plane of treatment and margins orthogonal will be different .  PTV overlapping with a contoured normal structure –  PTV contour extending outside the skin –delineate PTV 5cm below the skin surface.  PTV margin can be reduced if more frequent imaging or other technical innovation is used to reduce geometric uncertainties.
  46. 46. Organs At Risk Classification : Normal tissue whose radiation sensitivity may significantly influence treatment planning &prescribed dose.  Class I Organs: radiation lesions are fatal or result in severe morbidity.  Class II Organs: mild to moderate radiation morbidity  Class III Organs: mild, transient, reversible, not significant radiation morbidity ICRU-50
  47. 47. Classification Of Organs At Risk Serial – whole organ is a continuous unit and damage at one point will cause complete damage of the organ (spinal cord, digestive system). So even point dose is significant Parallel – organ consists of several functional units and if one part is damaged, the rest of the organ makes up for the loss (lung, bladder). Dose delivered to a given volume or average/mean dose is considered. Serial-parallel – kidney (glomerulus- parallel, tubules- serial), heart (myocardium- parallel, coronary arteries - serial). ICRU-62
  48. 48. Step 5 :Dose prescription :  Based on published data and clinical experience  Prescription is specified as a dose at or near the center of PTV as a dose covering certain percentage of PTV.
  49. 49. Step 6 : Conformal Planning  Forward Planning :In this places beams into a radiotherapy treatment planning system which can deliver sufficient radiation to a tumour while both sparing critical organs and minimising the dose to healthy tissue and later modification is done  Inverse Planning :this approach starts with desired result (a uniform target dose) & works backward toward incident beam intensities.
  50. 50. Step 6 :Forward Planning  Beam arrangement – ability to orient beams in 3D allows one to develop plans using non coplanar beams.  Field shaping – BEV and DRR display allow to view target volume and OAR ,hence shielding blocks and MLC can be placed accordingly .
  51. 51.  Beam directions that create greater difference between targets and critical structures are preferred  A 2cm margin between the PTV and field edge ensures better than 95% isodose coverage of the PTV.  coplanar or non coplanar
  52. 52. Beam Designing: Beam arrangement Field multiplicity : less need for high energy beams Disadvantage : designing excess number of beams shaping blocks longer setup time carrying of blocks – danger
  53. 53.  to get a practical idea about geometry of beam placement .  Simulates any arbitrary viewing location in treatment room.  Provides near time capability for evaluating the location of hot and cold spots in a given dose distribution. Rooms Eye View :
  54. 54. Beam Designing : Field Shaping  MLCs are used to shape the field around the PTV. Placed using Beams eye view (BEV)  BEV : The observer's viewing point is at the source of radiation looking out along the axis of the radiation beam in planes perpendicular to central axis of the beam .  Easily view the critical structure volumes and the target volume so that shielding blocks or MLC defined apertures can be defined.
  55. 55. Beam Modeling :
  56. 56. DRR- Digitally Reconstructed Radiograph  After beam arrangement, DRR is generated.  Used for treatment portal design.  Verification of treatment delivery by comparison with portal film.  allow better visualization of organs of interest.
  57. 57. Step 7 :Dose distribution calculation : Rectilinear coordinate system affixed to the patient 3D CT image set is typically used for calculating the dose distribution . Horizontal axis Vertical axis of CT couch motion
  58. 58.  CT numbers are not directly used in photon dose calculations , electron density of the corresponding tissue are used. Why ??  Compton scattering is dominant for photon beam used in radiotherapy and absorption and scattering of photons in tissue depends on electron density  Errors in CT numbers – errors in dose calculation . <10% errors not significant.
  59. 59.  Once the parameters are defined, the Treatment Planning Software generates the dose distribution  Past – dose calculation algorithms were traditionally based on dose distribution measured in water phantoms and applying correction factors for non uniform surface/beam obliquity tissue heterogeneities beam modifiers  Advanced models– superposition/convolution method
  60. 60. Plan Optimization And Evaluation :  Iterative, interactive approach  Beam arrangement is done based on review of DVH and multilevel 2D display levels showing isodose lines superimposed on CT images.  REV view is used to display dose clouds along with rendered PTV and OAR’S. hot and cold spots can be seen
  61. 61. Plan Evaluation The following tools are used in the evaluation of the planned dose distribution: • Methods of dose display Isodose lines Color wash DVHs (Dose volume histograms ) • Dose distribution statistics
  62. 62. Colour Wash - Spectrum of colours superimposed on the anatomic information represented by modulation of intensity Gives quick over view of dose distribution Easy to assess over dosage in normal tissue that are not contoured. To asses dose heterogeneity inside PTV Slice by slice evaluation of dose distribution can be done.
  63. 63. Coverage By Slice  Always verify the anatomical dose distribution slice by slice, in order to identify where under dosage or over dosage is occurring. overdosage underdosage
  64. 64. Problems With 3D Dose Distribution:  Huge amount of information to assess  Difficult to quantify visually  Difficult to understand relationship between dose and 3d anatomy DVH
  65. 65. DVH– Dose Volume Histogram  gives an idea of the percentage volume receiving the percentage dose both for the tumor and the normal organs.  2 types – Cumulative Differential  provides a complete summary of the entire 3D dose matrix,  it does not provide any spatial information. Thus, the DVH can only complement, and not replace, spatial dose-distribution displays.
  66. 66. Differential DVH :  Is a plot of the volume of a given structure receiving a dose within a specified dose interval(or dose bin) as a function of dose.  Shows the extent of dose variation within a given structure.  Useful to display dose to target volumes—to see max ,min , mean dose.
  67. 67.  It is plot of volume of a given structure receiving a certain dose.  Any point on the cumulative DVH curve shows the volume of a given structure that receives the indicated dose or higher.  It start at 100% of the volume for zero dose, since all of the volume receives at least more than zero Gy . Cumulative DVH :
  68. 68. See Dose Statistics : It provide quantitative information on the volume of the target or critical structure and on the dose received by that volume. These include :The minimum dose to the volume The maximum dose to the volume The mean dose to the volume Useful in dose reporting.
  69. 69. Plan Approval :  uniform dose is delivered to the target volume (+7% to -5% of prescribed dose)  Dose to critical structures below tolerance level  Well within constraints for maximum ,median dose or according to volume constraint.  Acceptable dose distribution is one that differs from desired dose distribution within pre-set limits of dose and only in regions where desired dose distribution can’t be physically achieved.
  70. 70. Plan Implementation And Treatment Verification :  Once the plan is designed, evaluated, and approved, documentation for plan implementation is generated.  This includes beam parameter settings and MLC parameters communicated to the computer system that controls the MLC of treatment machine, and DRR generation and printing or transfer to the Image database .
  71. 71.  Transfer plan parameters into treatment machine record-and-verify system  Set up (register) the real patient according to plan (verification simulation optional)  Perform patient treatment quality assurance checks including independent check of monitor units.
  72. 72. Clinical Utility 3DCRT : The possible benefits with 3D CRT in clinical practice are as follows  Improved local control  Reduced acute and late morbidity  Possibility of dose escalation
  73. 73. Patient Selection Patients most likely to be benefited with this technique are those who have :  Tumors in sites with complex anatomy  Irregularly shaped tumors  Tumors adjacent to radiation sensitive normal structures  Small volume or high dose treatments
  74. 74. Clinical Areas Following tumor sites have been extensively treated with this technique :  Lung Cancer  Brain Tumors  Prostate Cancer  Partial Breast Irradiation  Head and Neck Cancer  Pancreatic Tumors  Liver Tumors
  75. 75. Brain Tumors :
  76. 76. PTV RT TEMPORAL LT TEMPORAL BRAINSTEM LENS OPTIC NERVE SPINAL CORD
  77. 77. Ca Lung
  78. 78. Ca Cervix
  79. 79. Role In Prostate Cancer :  Less bladder and rectum toxicity  Dose escalation – better disease control
  80. 80.  3DCRT can drastically reduce rectal and bladder dose (Perez et al) Conv RT 3DCRT Bladder > 65Gy ~60% ~34% Rectum > 65Gy ~50% ~22% Rectal and bladder complication rates are reduced Conv RT 3DCRT IMRT Gr II ~50-60% ~20-30% 5% (R) 15% (B) Gr III ~3-4% (20-30% with dose escalation)
  81. 81. Pelvis Treatments :  Reduction in small bowel toxicity.  Prevention of late term ano-rectal toxicity  Escalation of dose to pelvic lymph nodes  Better target coverage
  82. 82. Pediatric Tumors :
  83. 83. Results other sites :  Breast : improves dose coverage and reduces inhomogeneity, elimination of additional surgical procedures, improves cosmesis, reduces fat necrosis  Anal canal : Conformal techniques provides an opportunity to spare small bowel and the femoral heads.  GIT : 3D CRT can be validated because it improves dose distribution , reduces dose to kidneys, liver and cord.  Head & neck :permits good coverage of the PTV .There is low rate of acute toxicity which can be explained by improving the dosimetric parameters of organs of risk
  84. 84. Advantages :  allows for the simulation of the patient's treatment without their physical presence after the CT scan is obtained.  Treatment modifications.  system allows for better dosimetric optimization above that which is achievable with geometric optimization alone. Limitations : • Knowledge of tumor extent • CTV is often not fully discernible • Patient motion • Biologic response of tumor
  85. 85. Conclusion :  Tightening of field margins around image based GTV with little attention to occult disease, patient motion is a misuse of 3DCRT ---should be avoided.  3DCRT is not synonymous with better results  Its superiority lies entirely on how accurate the PTV is and how much better the dose distribution is… hence i conclude by stating that it is a superior tool for treatment planning with a potential of achieving better results.
  86. 86. Thank you…

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