Comparative Study of Fluence Distribution and Point Dose Using Arc-check and Delta4 Phantoms

Abstract

The study aims to assess the fluence distribution and point dosage between two phantoms for patient-specific quality assurance on the Tomotherapy system. This was a retrospective study conducted on 15 patients who had radiation using the Helical Tomotherapy Machine (Radixact, Accuray Inc.). We used two phantoms to quantify the fluence produced by the treatment planning system (TPS) and recorded from the machine. The ArcCHECK (Sun-Nuclear) has 1386 diodes placed in a cylindrical configuration. The minimal resolution for this was 7 mm. The second was Delta4, supplied by ScandiDos. It has 1069 diode detectors arrayed in a crossed orthogonal configuration with a minimum resolution of 5 mm. All patient plans were transferred to these phantoms to validate the accuracy of treatment plan delivery. We used SunCHECK and ScandiDos Delta4 software to compare the fluence produced by the TPS with the fluence measured by the equipment. In ArcCHECK, we used an external ionization chamber, cc13 (IBA dosimetry), whereas in Delta4,we employed a central diode detector to quantify point dosage. The mean and standard deviation of the gamma pass percentage with ArcCHECK were 98.3 ± 0.8%, with an average point dose deviation of ± 0.94%. The mean and standard deviation of the gamma pass percentage using Delta4 was 99.1 ± 1.6%, while the average point dose deviation was ± 0.60%, both of which were well within the 3% tolerance employing the two phantoms.

Keywords

• arc-check
• delta4
• fluence maps
• patient specific quality assurance
• point dosimetry