Do we need Proton Therapy? GEOFFREY IBBOTT RADIOLOGICAL PHYSICS - PowerPoint PPT Presentation

Do we need Proton Therapy? GEOFFREY IBBOTT RADIOLOGICAL PHYSICS CENTER HOUSTON, TEXAS

Target Margin Display Distal Target Margins Proxim al

Dose Profile Showing Modulated Depth

Dosimetry and Calibration Standards � Disagreement on width of SOBP � Disagreement on procedure to convert CT# to stopping power � General, but not universal, agreement to use TRS-398

Promising research/ development areas 1. Delivery systems with selectable energy, scanning 2. Standards for measurement, prescription and reporting of dose 3. IMPT 4. Adaptive treatment for moving targets 5. Therapeutic effectiveness to be demonstrated 6. Adopt high-LET radiation Jakel et. al., (2008) The future of heavy ion radiotherapy. Med. Phys. 35 , 5653

Proton Pelvis Phantom

Phantom Treatment � Treatment plan created with a prescription of 6 Gy to the prostate � Plan delivered 3 times with film and TLD inserted in phantom � Plan accounting for difference in patient and material SP to be delivered in near future

TLD results PTV Right PTV Left Femur Right Femur Left Institution Predicted 600.2 600.2 247.3 243.8 Dose (cGy) TLD Measured Dose 589.8 595.1 242.1 240.4 (cGy) Measured / Predicted 0.983 0.992 0.979 0.986 Dose � PTV within 1.7% of predicted value � Femur within 2.1% of predicted value

To borrow from Dr. Vikram… � Should we study proton therapy? � Yes! � Should we use proton therapy outside prospective clinical trials? � No! � Do we need standardized protocols for dose measurement and specification? � Yes!