the external beam radiotherapy and image-guided radiotherapy (1)

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