SU-FF-T-203: Evaluation and Performance Characteristics of An Implantable Dosimeter with the TomoTherapy Hi-Art System

Abstract

Purpose: To evaluate the performance of an implantable dosimeter for IMRT treatment delivery and daily dose verification with the TomoTherapy Hi‐Art System. Method and Materials: The DVS® dosimeter from Sicel Technologies was used to measure the dose delivered with TomoTherapy and was compared against the treatment planning calculation and ion chamber measurements. Two DVS® devices were used. One of the devices tracked the dose for a static tomotherapy beam. The other device tracked the dose for an IMRT prostate treatment plan. Comparable measurements were obtained with a NIST‐traceable calibrated ion chamber. All three detectors were placed at isocenter within a uniform cylindrical phantom. Before delivery, MVCT scans were made for treatment position verification followed by measurements. Results: Day‐to‐day position verification using MVCT scans for both types of dosimeters was reproducible. When comparing the results for the static beam delivery, the cumulative dose error was 0.4% between the ion chamber and the DVS® dosimeter. The results for the first 10 fractions resulted in an average percent difference of 0.70% from the planned dose with a standard deviation of 0.92%. When comparing the results for the prostate plan, the cumulative dose error was 3.2% between the ion chamber and the DVS® dosimeter. The results for the first 10 fractions resulted in an average percent difference of 0.68% from the planned dose with a standard deviation of 1.0%. Conclusions: The measurements made by the DVS® dosimeter falls within the device's specified accuracy of the dosimeter. The DVS® device is easily identifiable with the Hi‐Art TomoTherapy System and is an effective fiducial marker. MVCT verification scans did not contribute any significant dose nor did they affect the accuracy of the DVS® device. Conflict of Intertest: Sicel Technologies, Inc provided the equipment and materials used in the study.