Room: Exhibit Hall | Forum 8
Purpose: When the X-ray beam is heavily filtered (for fluoroscopy guided interventional systems (FGI)), the error of the measured kVp can exceed a 5% limit when using a Radcal solid-state multi-sensor AGMS-DM+. This study determines the capability kVp measurement limits of the Radcal solid-state multi-sensor under heavily filtered X-ray beams.
Methods: Different thicknesses of copper or aluminum filtrations were added in front of the X-ray tube of a GE Mobile C-arm (OEC-9800), while kVp is measured using the Radcal. 80, 100, and 120kVp excitations were investigated utilizing a fixed mA. The added copper filtration ranges from 0.2mm to 3mm, with 0.2mm increments, and the added aluminum ranges from 1mm to 6mm, with 1mm increments. The measured kVp, 1-shot-HVL, and detector calculated filtration in mm of aluminum were recorded.
Results: The calculated filtration increases with the added copper filtration linearly, until the measured filtration saturates at 42 mm Al. The saturation point occurs when the added copper filtration is 0.8mm for 80 & 120kVp, and 1mm for 100kVp. Beyond the 42mm saturation, adding more copper increases the kVp error above 5% when added copper exceeds 1mm for 100 & 120kVp, and exceeds 2mm for 80 kVp. Before saturating at 42mm Al, the measured kVp error is within or close to 5%. Adding aluminum filtration, up to 6mm, doesn't appear to detrimentally affect the kVp measurement. The error of the calculated aluminum filtration is within 6%. The calculated HVL saturates at 13.6 mm aluminum when copper filtration is 1.4mm for 120kVp, and 3mm for 100kVp.
Conclusion: In order for Radcal to provide kVp readings within 5% of the expected value, the effective filtration of the beam should be less than 42mm of Aluminum, and the measured HVL should to be less than 11.7mmAL, 11.1mmAL and 9mmAL for 120kVp, 100kVP and 80kVp, respectively.