Purpose: To estimate the system, patient size, and projection specific Dose Conversion Coefficients (DCC) for coronary angiography (CAG) procedures at our site.
Methods: X-ray spectrums were modeled based on measured Entrance-Skin-Exposure-Rate (ESER) for CAG procedures using PCXMC (STUK, Finland) Monte Carlo dosimetry software. Monte Carlo simulations were then carried out to simulate organ doses from monochromatic beams with a typical field size (25x25 cm). User provided Kerma-Area-Product (KAP) was given as input to compute associated Effective Dose (ED) for the procedure. DCC was obtained by dividing the calculated ED by the KAP. This was done for three cardiovascular systems, Philips Allura XPER FD, Siemens Axiom Q Zen, and GE Innova by modeling their spectrums using patient size specific ESERs, with three most commonly used projections (PA, LAO45Â° and Lateral). ED for average patient was calculated for all three systems using the modeled DCCs and the median of CAG specific KAP at our site.
Results: The fitted filtration thickness for each cardiovascular system provides an understanding of manufacturer specific optimizations to obtain the desired image quality for patients of varied sizes. The modeled DCCs for average adult ranged from 0.13 to 0.33 mSvGy-1cm-2, which is consistent with the 0.2 mSvGy-1cm-2 in NCRP 160 and 0.35 mSvGy-1cm-2 as derived based on a recent publication. The calculated projection-specific ED for average adult varies from 6.3 to 10.9 mSv among the three systems, while the ED based on projection-independent DCC (0.2 mSvGy-1cm-2) is 8.7 mSv.
Conclusion: We have developed a simple method to estimate the DCC for CAG procedures. The overall range of modeled DCCs agrees well with published results. Future work is aimed at extending this approach to DCC and ED calculation for additional projections and other fluoroscopic procedures.