Product Development of Intensity Modulation for Bolus Electron Conformal Therapy

Project Summary Abstract Electron beam therapy EBT using MeV beams provides effective radiation treatment for superficial cancers depthandlt cm As many as of radiotherapy patients in USA annually are eligible for electron therapy for some portion of their treatment making it the second most used external beam modality As many as of these electron patients annually could benefit from bolus electron conformal therapy ECT a technique conforming the dose distribution distal isodose surface to the targeted cancer volume while protecting surrounding healthy tissue from acute and long term adverse effects of radiation aligning with the agency mission to improve cancer treatment quality Currently radiation oncologists are limited in the use of bolus ECT because of dose heterogeneity as great as in the targeted cancer volume due to multiple Coulomb scattering from the irregular proximal bolus surface This Phase I application proposes to research and develop electron intensity modulation technology planning software and delivery device which when integrated with existing bolus ECT technology can eliminate the dose heterogeneity problem i e deliver a more uniform dose distribution dose spread to the targeted cancer volume Availability of the proposed product intensity modulated bolus ECT should not only greatly improve current treatments of superficial cancers using electron radiotherapy bolus ECT or otherwise but in some cases provide an improved alternative to other radiation modalities e g volumetric arc therapy or intensity modulated radio therapy by having decreased chance of secondary cancers equally high chance of cancer control and equally low chance of acute normal tissue complications The proposed delivery technology is an intensity modulator plate which consists of a matrix of small diameter cylindrical island blocks imbedded in a low density slab attached to the beam defining collimating insert The magnitude of the intensity modulation is related to the fraction of beam area covered by the island blocks in a small overlying region By properly varying the diameter and or separation of these island blocks electron scatter in air should result in a smoothly varying intensity pattern on the patient and or bolus that restores the dose uniformity in the cancer target volume when using bolus ECT Phase I goals will be to demonstrate proof of principle by incorporating intensity modulation into the existing BolusECT software product including a method for segmenting the intensity pattern into an appropriate matrix of island blocks validating that the planning software modeling the island blocks produces expected results for select patient sites and validating delivery of the planned intensity modulated BolusECT beams by demonstrating agreement between delivered measured and planned calculated dose distributions in water Project Narrative Electron beam radiotherapy an effective modality for radiotherapy of superficial depth cm cancers potential US patients year has the ability to protect distal healthy tissue from acute and long term adverse effects of radiation however radiation oncologists are often limited in use of its most powerful delivery technique bolus electron conformal therapy ECT because of excessive dose heterogeneity as great as in the targeted cancer volume due to scatter from the irregular proximal surface of the bolus This STTR application proposes to research and develop an intensity modulation technology planning software and delivery device that can be integrated with existing bolus ECT technology previously shown to provide a more uniform and equally conformal dose distribution to the targeted cancer volume Heretofore no such product has been available therefore if developed this should not only greatly improve current electron radiotherapy but potentially provide an improved alternative to other radiation modalities by providing decreased chance of secondary cancers equally high chance of cancer control and equally low chance of acute normal tissue complications