Purpose: The dose area product (DAP) may be a more reliable and convenient metric than mA-min for radiation shielding design. DAP is more readily available and better correlated with x-ray scatter than mA-min. We investigated the use of DAP as an alternative metric of radiation workload for modern cardiac angiography suites.
Methods: Irradiation event data was collected from radiation dose structured reports (RDSRs) for 11 cardiac angiography suites across 4 hospitals for 3 weeks in 2019. Workload distributions as a function of kVp were calculated for DAP and mA-min. DAP was consistently provided in the RDSR but mA-min required calculation of the product of tube current (mA) and exposure time using DICOM fields in the RDSR that were populated inconsistently among vendors. To enable comparison of DAP workloads with mA-min workloads (from NCRP Report 147), a DAP-to-mA-min conversion factor was estimated.
Results: The average DAP/patient workload was 490 dGy-cm²/patient. The DAP-to-mA-min conversion factor was 0.31. Of the 10 suites with data from ≥20 patients, this conversion factor predicted the total mA-min with a mean absolute error of 21% (error range: -45% to 58%). The average workload was slightly lower than that of NCRP-147 (150 mA-min/patient vs. 160 mA-min/patient, respectively) and had a higher average tube potential (93 kVp vs. 88 kVp, respectively). Notably, the workload at high kVp (115 – 120 kVp) was approximately five times greater than in NCRP-147.
Conclusion: The radiation workload for modern cardiac angiography suites was readily calculated using DAP. DAP and mA-min workload distributions were compared to estimate a DAP-to-mA-min conversion factor. This conversion factor may help facilitate future comparisons between DAP workloads and mA-min workloads (from NCRP-147). Future work will investigate secondary air kerma rates for this DAP distribution which may be useful for shielding calculations.