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On Efforts to Correct Discrepancy Between System-Reported Air Kerma Rates and Measured Air Kerma Rates for Ziehm Vision RFD 3D C-Arm System

J Dave1*, (1) Thomas Jefferson University, Philadelphia, PA


(Tuesday, 7/16/2019) 9:30 AM - 10:00 AM

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 ‘low-dose’, ‘standard-dose’ and ‘high-dose’ modes. Errors between the system-reported and measured AKR values were analyzed with reference to the ±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 ‘low-dose’ and ‘standard-dose’ modes (system-reported AKR: 13.2-57.0mGy/min). However, the maximum error between the system-reported and measured AKR was 29% for ‘high-dose’ 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 ‘standard-dose’ mode, as per manufacturer-specified protocol. After service intervention, maximum errors in ‘low-dose’, ‘standard-dose’ and ‘high-dose’ 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 ‘low-dose’ and ‘standard-dose’ modes were same, but in the ‘high-dose’ 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 ‘low-dose’ and ‘standard-dose’ modes increased when the calibration factor was chosen to minimize AKR errors in ‘high-dose’ 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.


Fluoroscopy, Validation


IM- Other (General): Electromagnetic radiation (general)

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