Effect of the radiation field of view and angle in unconventional angiography on patient doses: a Monte Carlo simulation study using a voxelized phantom

Introduction: We aimed to investigate the effect of variation of beam angle and field of view (FOV) on organs’ and effective doses for patients undergoing interventional cardiology examinations by using Monte Carlo simulations and ICRP110 phantom.   Materials and Methods: Simulations were done for energies obtained from experimental measurements on the left ventricle phantom of the Axiom Artis model of an angiography system by Monte Carlo N- Particle System code (MCNP). The ICRP110 voxelized whole body model representing an average patient was employed at posterior anterior (PA) position. To guide the x-ray source, the approximate spherical coordinates were set at: 27, 27.135. The collimated x-rays beam was directed toward the patient's body over 16´16 and 25´25 cm2 field sizes for twenty alternative proposed techniques and their resulting effective doses were estimated and compared with those obtained for six relevant routine techniques of coronary angiography including LAO40-CAUD40, LAO45, LAO60-CRA20, PA-CRA45, RAO20-CAUD20 and RAO30, used at a hospital. Results: Variation of the angle and FOV for the 25´25 cm2 field size resulted in dose reduction for some of the proposed techniques including the LAO20-CAUD20, LAO20-CAUD45, LAO60- CAUD20, LAO60-CAUD45, LAO30, LAO60-CRA30, RAO10-CAUD30, RAO30-CAUD30, RAO20 and RAO40 with an amount of 12, 15, 27, 74, 40, 54, 50, 56, 13 and 38 percent respectively. But, for the 16´16 cm2 field size, the dose reduction was observed just for the LAO60-CRA30, RAO10-CAUD30 and RAO30-CAUD30 proposed techniques with an amount of 41, 16 and 38 percent respectively. Conclusion: By appropriate variation of the beam angle and FOV, the number/volume of the critical organs exposed directly to primary x-rays can be reduced and lead to the reduction of effective dose while keeping the target organ within the radiation field.