Impact of a Prototype 29:1 Ratio Grid on Image Quality and Radiation Dose in Abdominal Angiography Evaluation in a Pig Model

Objectives The aim of this study was to evaluate the impact of a prototype grid with a 29:1 ratio (r29) and a 15:1 (r15) grid on the image quality (IQ) and radiation dose in abdominal angiography. Materials and Methods Six typical abdominal angiographic image scenarios were created in 4 pigs. Polymethylmethacrylate and aluminum plates were used to add 10 cm of patient equivalent thickness to simulate different body types. Fluoroscopic images were acquired with a source-to-image receptor distance of 120 cm. Tantalum- and iron-specific acquisition protocols at different IQ levels were acquired. IQ of radiation dose equivalent image pairs, created with the r29 and r15 grids, respectively, was quantitatively evaluated using contrast-to-noise ratio (CNR) measurements. Differences in radiation dose were estimated using the dose-weighted CNR. Two blinded readers compared IQ of these images using a Likert scale. In a second step, the readers selected pairs of the r29 and r15 images with subjectively equivalent IQ. Radiation doses were then compared. Results Compared with the r15 grid, the r29 grid images achieved similar CNR at an average of 26% (+/- 12%) lower radiation dose at a mean patient equivalent thickness of 26 cm and 36 cm. Both readers noted a significant increase in IQ (P < 0.001) for dose equivalent images, whereas the interobserver agreement was 0.59. For the selected IQ equivalent images, a radiation dose reduction of 38% (+/- 17%; P < 0.001, interobserver agreement 0.92) was noted when using the r29 grid. Conclusions The use of an r29 grid at a large source-to-image receptor distance can significantly improve the IQ compared with the r15 grid at the same radiation dose in abdominal angiography or can reduce radiation dose while preserving IQ.