the external beam radiotherapy and image-guided radiotherapy (1)
DESCRIPTION
The external beam radiotherapy and Image-guided radiotherapy (1). 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 - PowerPoint PPT PresentationTRANSCRIPT
Somvilai Mayurasakorn, MD.Division of Therapeutic Radiology and Oncology,
Faculty of Medicine, Chiang Mai University
• MAXIMAL CONTROL OF TUMOR– Accuracy of target volume delineation– Precise technique
• MININAL NORMAL TISSUE TOXICITY– Sophisticate technique
Rationale of 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
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
•The gross palpable or visible/demonstrable extent and location of the malignant growth
•Supplemental target localization informationCT scanMRI : improved soft tissue resolution for the definition of soft tissue
boundaries, e.g., tumor and surrounding normal tissuesPET : high level of sensitivity and specificity for tumor involvement
Gross Tumor Volume (GTV)
ICRU IMRT report
Target volumes in EBRT
Target volumes in EBRT
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
Molecular and Functional Imaging
Possible to map out the biology distributionMolecular|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
CT MRI T2 FS FDG-PET
Fiberoptic examinationRight piriform sinusSCC grade 2TNM 6th ed: T4N0M0
Gross Tumor Volume (GTV)
PET/CT : target volume of treatmentA prospective trial of PET in RT planning for esophageal carcinoma
significant impact on GTV and PTVprevented geographic miss: identifying unsuspected LN involvement
Leong T et al.Radiother Oncol 2006;78:254–61
Gross Tumor Volume (GTV)
Advanced EBRT
External beam radiotherapy
Image-Guided Radiotherapy
SOURCES OF GEOMETRIC UNCERTAINTIES
The Netherlands Cancer institute suggested1. Systematic errors • Uncertainties occurring during treatment
preparation – Setup error & organ motion on the planning CT
simulator study– Delineation errors– Equipment calibration errors
The Netherlands Cancer institute suggested2. Random variations • Uncertainties occurring during treatment
execution – Interfraction variations– Intrafraction variations
SOURCES OF GEOMETRIC UNCERTAINTIES
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
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
Video IGRT