Room: Exhibit Hall | Forum 8
Purpose: To present on efforts in correcting discrepancy between system-reported air kerma rates (AKR) and measured AKR for Ziehm Vision RFD 3D C-Arm system.
Methods: Acceptance testing was performed for a Ziehm Vision RFD 3D system. System-reported AKR (in mGy/min) at the interventional reference point were compared with the measurements made using a Radcal solid-state detector (AGMS-D); these measurements were performed in â€˜low-doseâ€™, â€˜standard-doseâ€™ and â€˜high-doseâ€™ modes. Errors between the system-reported and measured AKR values were analyzed with reference to the Â±35% suggested tolerance limit. If errors were unacceptable, service intervention was initiated, and testing was repeated.
Results: Initially, maximum error between the system-reported and measured AKR were 6% and 7% for â€˜low-doseâ€™ and â€˜standard-doseâ€™ modes (system-reported AKR: 13.2-57.0mGy/min). However, the maximum error between the system-reported and measured AKR was 29% for â€˜high-doseâ€™ mode (system-reported AKR: 79mGy/min). Service intervention included a two-point calibration utilizing measured doses at 50kV and 100kV for pre-configured settings. However, this two-point calibration was performed only in the â€˜standard-doseâ€™ mode, as per manufacturer-specified protocol. After service intervention, maximum errors in â€˜low-doseâ€™, â€˜standard-doseâ€™ and â€˜high-doseâ€™ modes were 21% (AKR: 15.5mGy/min), 22% (AKR: 68.8mGy/min) and 12% (AKR: 91.2mGy/min). For this C-Arm system pulse-widths in the â€˜low-doseâ€™ and â€˜standard-doseâ€™ modes were same, but in the â€˜high-doseâ€™ mode the pulse-width was relatively less. This difference in pulse-widths may not be factored in two-point calibration performed in 'standard-dose' mode. Thus, the errors in â€˜low-doseâ€™ and â€˜standard-doseâ€™ modes increased when the calibration factor was chosen to minimize AKR errors in â€˜high-doseâ€™ mode.
Conclusion: This study highlights the importance of verifying system-reported AKR in all fluoroscopy modes. The study also reveals that vendor-specific calibration protocols may require modification such that calibration of system-reported AKR should be performed for each dose mode, especially when pre-configured settings (e.g., pulse-widths) between the dose-modes is different.