Program Information
Maximum Energy of Helium and Carbon Ions Clinically Needed for Spine, Lung, Prostate and Pancreas Cancer
A Pompos*, H Choy , X Jia , S Jiang , R Timmerman , The University of Texas Southwestern Medical Ctr, Dallas, TX
Presentations
SU-E-T-539 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: Maximum available kinetic energy of accelerated heavy ions is a critical parameter to consider during the establishment of a heavy ion therapy center. It dictates the maximum range in tissue and determines the size and cost of ion gantry. We have started planning our heavy ion therapy center and we report on the needed ion range.
Methods: We analyzed 50 of random SBRT-spine, SBRT- lung, prostate and pancreatic cancer patients from our photon clinic. In the isocentric axial CT cut we recorded the maximum water equivalent depth (WED4Field) of PTV’s most distal edge in four cardinal directions and also in a beam direction that required the largest penetration, WEDGantry. These depths were then used to calculate the percentage of our patients we would be able to treat as a function of available maximum carbon and helium beam energy. Based on the Anterior-Posterior WED for lung patients and the maximum available ion energy we estimated the largest possible non-coplanar beam entry angle φ (deviation from vertical) in the isocentric vertical sagittal plane.
Results: We found that if 430MeV/u C-12, equivalently 220MeV/u He-4, beams are available, more than 96% (98%) of all patients can be treated without any gantry restrictions (in cardinals angles only) respectively. If the energy is reduced to 400MeV/u C-12, equivalently 205MeV/u He-4, the above fractions reduce to 80% (87%) for prostate and 88% (97%) for other sites. This 7% energy decrease translates to almost 5% gantry size and cost decrease for both ions. These energy limits in combination with the WED in the AP direction for lung patients resulted in average non-coplanar angles of φ430MeV/u = 68°±8° and φ400MeV/u = 65°±10° if nozzle clearance permits them.
Conclusion: We found that the two worldwide most common maximum carbon beam energies will treat above 80% of all our patients.
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