The impact of pitch values on image quality and radiation dose in an abdominal adult phantom using CT

Abstract

Purpose: To identify the impact of different pitch values on image quality and effective radiation dose for axial and coronal plane in abdominal adult CT. Methods and materials: Three scans were conducted on an abdominal phantom using a Toshiba Aquilion 16-slice CT scanner with three different pitch values: standard (0.938), detail (0.688) and fast (1.438). Slices were taken from the upper, middle and lower abdomen in the axial plane and anterior, middle and posterior in the coronal plane. The six different anatomical structures were liver, intrahepatic vessels, spleen, pancreas, kidneys and renal vessels, retroperitoneum, aorta and vena cava. A two-alternative forced-choice (2AFC) method was used to evaluate images for each pitch with 8 observers using a 3-point Likert scale. SNR was calculated in every plane, slice and pitch factor using the ImageJ software. To estimate effective radiation dose the CT Expo software was used. Results: Detail pitch factor provides superior image quality compared to standard in axial plane when evaluating the liver (p<0.034) and pancreas (p=0.008). However, the results for spleen, kidney, renal vessels, retroperitoneum, aorta and vena cava are not significant when comparing detail vs standard. Standard provides a 26.3% reduction in effective radiation dose (mSv) compared to detail. Fast had the worst image quality in both the axial and coronal plane but the lowest dose. In the coronal plane, standard was superior to both detail (p=0.026) and fast (p=0.023) in terms of image quality. The differences in SNR results were not significant except in standard vs detail in the coronal plane (p=0.03). Conclusion: Detail pitch factor provides superior image quality to standard and fast in the axial plane. Standard had superior image quality to both detail and fast in the coronal plane. The augmentation of effective doses has been inversely proportional to the pitch factors. The most irradiant pitch mode was detail and the less was fast.