Technical note: Relationship between peak skin dose and fluoroscopic K_a,r : Clinical variations and application in...

The reference point cumulative air kerma (K_a,r ) is a commonly used dose quantity for establishing substantial radiation dose levels (SRDLs) that can provide guidance for patient dose management actions following fluoroscopically guided procedures. However, the K_a,r may not correlate well with the patient peak skin dose (D_skin,max ) because the relationship between K_a,r and D_skin,max may vary widely due to clinical variations. Therefore, it may be prudent for institutions to establish different K_a,r -based SRDL values based on the clinical procedure type.

The present study investigates the relationship between K_a,r and D_skin,max for different clinical services and how that variation may overestimate or underestimate the need for patient follow-up. Additionally, the study suggests a possible framework for establishing K_a,r SRDLs based on the clinical data analysis.

A retrospective analysis was performed for fluoroscopically guided interventions exceeding 5 Gy K_a,r . For each procedure, the patient D_skin,max was estimated and the ratio of D_skin,max to K_a,r (DKR) was calculated. Results were pooled into one of three clinical service categories: body interventions (n = 33), cardiac interventions (n = 81), or neurological (neuro) interventions (n = 44). The distributions in K_a,r , D_skin,max , and DKR were analyzed in aggregate and by the clinical service category.

The median K_a,r values for procedures exceeding 5 Gy were 6.0 Gy (95% CI [5.6, 6.4]) for body interventions, 5.8 Gy (95% CI [5.5, 6.0]) for cardiac interventions, and 6.3 Gy (95% CI [5.9, 6.6]) for neuro interventions. D_skin,max for the same procedure data sets were 5.0 Gy (95% CI [4.4, 5.6]) for body interventions, 5.5 Gy (95% CI [5.2, 5.8]) for cardiac interventions, and 3.7 Gy (95% CI [3.4, 4.0]) for neuro interventions. This resulted in median DKR values of 0.81 for body interventions, 0.91 for cardiac interventions, and 0.59 for neuro interventions.

This study illustrates the need to understand the relationship between the reported K_a,r and the patient D_skin,max for different types of interventional procedures. This is especially important when an institution uses K_a,r as the parameter for establishing an SRDL threshold to identify patients who may require clinical follow-up. The implications of this research and a guide for how to implement these findings are elaborated on in the Discussion.