Somvilai Mayurasakorn, MD.
Division of Therapeutic Radiology and Oncology,
Faculty of Medicine, Chiang Mai University
Rationale of radiotherapy
• MAXIMAL CONTROL OF TUMOR
– Accuracy of target volume delineation
– Precise technique
• MININAL NORMAL TISSUE TOXICITY
– Sophisticate technique
External beam radiotherapy
• 2D radiotherapy
ICRU 29
External beam radiotherapy
• 3D radiotherapy
ICRU 29
External beam radiotherapy
• Advanced radiotherapy
ICRU 62
External beam radiotherapy
• Advanced radiotherapy
External beam radiotherapy
2D
3D
IMRT
Simple to Complex
Advanced radiotherapy treatment
Three-dimensional treatment planning systems
• Increasingly more conformal treatments
• Deliver high dose radiotherapy to an
accurately defined target volume
• Minimum dose to surrounding tissues
• Dose escalation ; leads to improved clinical
outcomes
– Evidence: lung, head & neck and prostate cance
Cancer Imaging (2006) 6, 30–32
Target volumes in EBRT
Gross Tumor Volume (GTV)
•The gross palpable or visible/demonstrable
extent and location of the malignant growth
•Supplemental target localization information
CT scan
MRI : improved soft tissue resolution for the definition of soft tissue
boundaries, e.g., tumor and surrounding normal tissues
PET : high level of sensitivity and specificity for tumor involvement
ICRU IMRT report
Target volumes in EBRT
GTV & CTV
CT and MRI supplemented by
PET information. GTV, light
blue; PTV1, yellow; PTV2, red;
right parotid gland, dark blue;
left parotid gland, orange
Molecular and Functional Imaging
Tumor biology plays an important role in
• Diagnosis
• Treatment decision-making
• Assessment of therapeutic response
The development of cellular and molecular imaging
 Significant opportunities for the radiation discipline
to take the patient’s biological information into the
radiation therapy treatment decision-making process
and to truly individualize cancer radiotherapy
Molecular and Functional Imaging
Possible to map out the biology distribution
Molecular|functional imaging-guided treatment generally favors
non-uniform dose distributions and requires a plan optimization
formalism in voxel domain to deal with the biological heterogeneity
Gross Tumor Volume (GTV)
Fiberoptic examination
Right piriform sinus
SCC grade 2
TNM 6th ed: T4N0M0
CT
MRI T2 FS
FDG-PET
Gross Tumor Volume (GTV)
PET/CT : target volume of treatment
A prospective trial of PET in RT planning for
esophageal carcinoma
significant impact on GTV and PTV
prevented geographic miss
: identifying unsuspected LN involvement
Leong T et al.Radiother Oncol 2006;78:254–61
Advanced EBRT
• More precious RT
Improves the
therapeutic ratio
Reduces normal
tissue morbidity
• More sophisticate
More resources
Adiquate ???
External beam radiotherapy
Image-Guided Radiotherapy
SOURCES OF GEOMETRIC UNCERTAINTIES
The Netherlands Cancer institute suggested
1. Systematic errors
• Uncertainties occurring during treatment
preparation
– Setup error & organ motion on the planning CT
simulator study
– Delineation errors
– Equipment calibration errors
SOURCES OF GEOMETRIC UNCERTAINTIES
The Netherlands Cancer institute suggested
2. Random variations
• Uncertainties occurring during treatment
execution
– Interfraction variations
– Intrafraction variations
IGRT
• Advanced technique :using imaging devices
that allows radiation to be delivered to tumors
with more precision than is traditionally
possible
• Many IGRT technologies are currently
available using multiple imaging modalities
– USN, video, planar, volumetric
IGRT
If we can :
Improve, patient setup (reproducibility)
Reduce uncertainties on patient movements
(intra,interfractions)
Reduce uncertainties on target movements
(intra,interfractions)
IGRT
So we could :
Reduce margins around targets used to take
into account movement
Obtain the opportunity to increase dose
Obtain a possible strategy to adapt to target
modifications, or to the patient
Imaging techniques for IGRT
Imaging techniques for IGRT
Video IGRT
A. Outline of the patient’s features
initially seen
B. As alignment improves, the image
becomes less distinct
C. Finally, a featureless gray image seen