Purpose: This work assessed the performance of a high ratio (r29) 80 line cm⁻¹ grid under adult patient cardiovascular angiography imaging condition. Non-grid and the OEM r15 80 line cm⁻¹ grid were used as reference conditions.
Methods: Plastic Water™ phantom thickness in the range 20-44 cm was used to attenuate the primary beam and create scatter. X-ray source to detector (SID) distance 107 and 120 cm was used to match the 105 and 118 cm focus distances of the grids. Fields of view (FOV) 20 and 25 cm were tested. The X-ray technique was fixed to ensure equal phantom-specific dose for all conditions. Primary and scatter transmission (Tp and Ts) of the grids and non-grid scatter to primary ratio (SPR) was measured using a lead beam stop method. Object quantum SNR improvement factor (Ksnr) theory was expanded to consider variable geometric magnification of a hypothetical test object located at the X-ray system isocenter and used to assess the relative SNR across experimental conditions.
Results: For equivalent imaging conditions, Tp of the r15 and r29 grids was 0.75 and 0.69 and Ts was 0.34 and 0.18, respectively. SPR was in the range 0.27-4.1; increased by 30-39% for FOV 25 versus 20 cm; and increased exponentially with phantom thickness. Ksnr increased approximately linearly with increasing phantom thickness. Ksnr of the 29 grid at SID 120 cm versus the r15 grid at SID 107 cm was in the range 1.0-1.17 for phantom thicknesses 20-44 cm. Predicted radiation dose reduction with preserved image quality ranged from 0-26%.
Conclusion: Compared to the r15 grid, the very low scatter transmission properties of the r29 grid is expected to improve the relationship between image quality and radiation dose for adult patients. The predicted benefit of the r29 grid increased with increasing phantom thickness.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by a grant from Siemens Healthineers.
Not Applicable / None Entered.