Impact of respiratory motion artifact on coronary image quality of one beat coronary CT angiography

BACKGROUND: Accuracy of CT-derived fractional flow reserve depends on good image quality. Thus, improving image quality during coronary CT angiography (CCTA) is important. OBJECTIVE: To investigate impact of respiratory motion artifact on coronary image quality focusing on vessel diameter and territory during one beat CCTA by a 256-row detector. METHODS: We retrospectively reviewed patients who underwent CCTA under free-breathing (n = 100) and breath-holding (n = 100), respectively. Coronary image quality is defined as 4-1 from excellent to poor (non-diagnostic) and respiratory motion artifact severity is also scored on a 4-point scale from no artifact to severe artifact. Coronary image quality and respiratory motion artifact severity of all images were evaluated by two radiologists independently. RESULTS: Compared with free-breathing group, the image qualities are significantly higher in per-segment, per-vessel and per-patient levels (P < 0.001) and proportion of segments with excellent image quality also improves significantly (73.6% vs 60.1%, P < 0.001) in breath-holding group. The image quality improvement occurs in medium-sized coronary arterial segments. Coronary image quality improves with respiratory motion artifacts decreasing in both groups, respectively. CONCLUSION: During one heartbeat CCTA, breath-holding is still recommended to improve coronary image quality due to improvement of the image quality in the medium-sized coronary arteries.

CT Protocols for Attenuation Correction and Segmentation in 99mTc-MAA SPECT/CT for 90Y Radioembolization Treatment Planning – a Simulation Study

Background Conventional 99mTc-macroaggregated albumin (99mTc-MAA) planar scintigraphy overestimates lung shunt fraction (LSF) as compared to SPECT/CT in 90Y radioembolization treatment planning. However, the respiratory motion artifact due to the temporal mismatch between static SPECT and helical CT (HCT) may compromise the SPECT quantitation accuracy by incorrect attenuation correction (AC) and volume-of-interest segmentation. The goal of this study is to systematically assess different AC and segmentation protocols for LSF, tumor-to-normal liver (TNR), organ absorbed dose and injected activity (IA) estimation in 99mTc-MAA SPECT/CT.Methods The 4D XCAT phantom was used to simulate 10 patient anatomies with 99mTc-MAA distribution based on the clinical data, each with LSF of 5%, 10%, 15% and 20%, axial respiratory motion of 2 cm, different TNR and tumor size. An analytical projector for low energy high resolution parallel-hole collimator was used to simulate realistic noisy planar acquisitions, and 128 projections over 360o for SPECT, both modeling attenuation, scatter and geometric collimator-detector-response. Five attenuation maps, i.e., (i) HCT at end-inspiration (HCT-IN), (ii) HCT at mid-respiration (HCT-MID), (iii) HCT at end-expiration (HCT-EX), (iv) cine averaged CT (CACT) and (v) interpolated average CT (IACT) were applied for SPECT AC and segmentation in LSF, dosimetric and IA evaluation. Mid-respiratory phases were also extracted from CACT/IACT for VOI segmentation while CACT/IACT were used for AC, i.e., hybrid CT protocols.Results For LSF estimation, SPECT/CACT has the least absolute errors. Planar significantly overestimates LSF and lung absorbed dose compared to SPECT especially for LSF of 5%. SPECT-based is better than CT-based segmentation in TNR estimation. There is no statistically significant difference for different CT protocols for TNR, normal liver and tumor absorbed dose estimation. Hybrid CTs and HCT-MID performed the best for IA especially for higher LSF.Conclusions 99mTc-MAA SPECT/CT with an appropriate choice of CT protocol for AC and segmentation is superior to planar in LSF and lung absorbed dose estimation. The 4D CT protocols are recommended for AC and segmentation to alleviate respiratory artifacts and improve quantitation accuracy in 90Y radioembolization treatment planning. HCT-EX would also be a recommended choice if 4D CT is not available.

Characterization of Severe Arterial Phase Respiratory Motion Artifact on Gadoxetate Disodium-Enhanced MRI – Assessment of Interrater Agreement and Reliability

Purpose To assess the interrater agreement and reliability of experienced abdominal radiologists in the characterization and grading of arterial phase gadoxetate disodium-related respiratory motion artifact on liver MRI. Materials and Methods This prospective multicenter study was initiated by the working group for abdominal imaging within the German Roentgen Society (DRG), and approved by the local IRB of each participating center. 11 board-certified radiologists independently reviewed 40 gadoxetate disodium-enhanced liver MRI datasets. Motion artifacts in the arterial phase were assessed on a 5-point scale. Interrater agreement and reliability were calculated using the intraclass correlation coefficient (ICC) and Kendall coefficient of concordance (W), with p < 0.05 deemed significant. Results The ICC for interrater agreement and reliability were 0.983 (CI 0.973 – 0.990) and 0.985 (CI 0.978 – 0.991), respectively (both p < 0.0001), indicating excellent agreement and reliability. Kendall’s W for interrater agreement was 0.865. A severe motion artifact, defined as a mean motion score ≥ 4 in the arterial phase was observed in 12 patients. In these specific cases, a motion score ≥ 4 was assigned by all readers in 75 % (n = 9/12 cases). Conclusion Differentiation and grading of arterial phase respiratory motion artifact is possible with a high level of inter-/intrarater agreement and interrater reliability, which is crucial for assessing the incidence of this phenomenon in larger multicenter studies. Key Points Citation Format