Purpose: The reference point air kerma (K₍a,r₎) is a readily-available dose quantity provided by most modern fluoroscopes that can provide guidance for patient dose management actions following fluoroscopically-guided procedures. This study investigates the patient peak skin dose (PSD) distribution for procedures exceeding the 5 Gy K₍a,r₎ which is the recommended substantial radiation dose level (SRDL) by NCRP 168 for potential patient follow-up.
Methods: Using DICOM radiation dose structured report data, PSD was calculated for 125 fluoroscopically-guided interventions (FGIs) exceeding a single procedure K₍a,r₎ of 5 Gy using an internally-validated PSD calculation method. Additionally, for each procedure, the ratio of PSD to K₍a,r₎ was calculated and the results pooled into one of three clinical categories: cardiac (N=67), body-interventional (N=24), and neuro-interventional (N=34). The K₍a,r₎ distribution and PSD distribution were analyzed for all procedures in aggregate while the PSD to K₍a,r₎ ratios were analyzed by the clinical procedure type.
Results: The K₍a,r₎ distribution resulted in a mean value of 6.7 Gy with a range of 5.1–18.6 Gy. The PSD distribution resulted in a mean value of 5.1 Gy with a range of 1.6–11.0 Gy. For the PSD to K₍a,r₎ ratio differentiated by clinical categories, cardiac FGIs resulted in a mean ratio of 0.84 with a range of 0.31–1.72, body-interventional FGIs resulted in a mean ratio of 0.74 with a range of 0.43–1.41, and neuro-interventional FGIs resulted in a mean ratio of 0.53 with a range of 0.37–0.88.
Conclusion: PSD to K₍a,r₎ ratios yielded substantially different results with respect to the clinical categories which illustrates the possible need of a K₍a,r₎ SRDL specific to the clinical service. Additionally, using a static K₍a,r₎ SRDL for any clinical service could over or under predict the need for patient follow-up indicating it may be better to establish SRDLs based on PSD.