4:02 PM Abstract No. 227 - Optimization of iterative reconstruction technique for CT pulmonary arteriography: systemic assessment in a porcine model

Abstract

Purpose To evaluate the quantitative and qualitative image quality of pulmonary CT arteriography images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR) scanned at differential radiation doses. Materials and Methods A healthy 56.1 kg Yorkshire pig underwent fluoroscopic placement of a femoral central venous catheter. The catheter was subsequently injected with macerated, previously clotted autologous blood. After pulmonary emboli were visualized in the left lower lobe segmental pulmonary arteries, successive pulmonary arterial CT angiography on a Discovery 750HD MDCT scanner (GE Healthcare) was performed at 700, 400, 200, 100, and 50 mA at 120, 100, and 80 kVp, for a total of 15 scans. Each scan was reconstructed FBP, ASIR (50% blend) and MBIR. Noise (SD) and contrast-to-noise ratios were calculated from ROIs over the left lower lobe segmental pulmonary artery and paraspinous muscle. Selected axial images were scored subjectively for PE visibility and overall image quality. Results Averaged across all doses, MBIR reduced noise and improved contrast to noise ratio (CNR) compared to FBP by 73% and 232%, and reduced noise and improved CNR compared to ASIR by 69% and 110%, respectively. The effect was more pronounced in higher noise settings. Averaged across all doses, MBIR improved subjective image quality and diagnostic sensitivity for pulmonary embolism (PE) compared to FBP by 50% and compared to ASIR by 25%. Subjective improvements in image quality were most pronounced in higher noise settings. At 120 kVp/400 mA, readers scored FBP, ASIR, and MBIR images equally. At 100 mA/120 kVp, readers scored FBP and ASIR images as nondiagnostic for detection of PE, while MBIR images were considered of moderate quality but remained diagnostic for detection of PE. Conclusion MBIR reduced image noise and improved CNR for the pulmonary arteries compared to ASIR and FBP across all dose levels. Furthermore, MBIR resulted in higher subjective image quality and improved diagnostic sensitivity for pulmonary embolism, particularly in higher noise settings.