CT can classify plaque based on its x-ray attenuation. However, identifying vulnerable plaque is limited by overlap between the attenuation of necrotic core and fibrous plaque. Changes in attenuation of plaque components to x-rays of differing energies may allow better discrimination. We tested whether Dual Energy CT (DECT) (simultaneous image acquisition at two energies) improved identification of necrotic core, both in-vivo and ex-vivo.
Methods
20 patients underwent DECT and 3-vessel Virtual Histology-IVUS (VH-IVUS). Attenuation was sampled in 1088 plaque areas co-registered with VH-IVUS and used to define dual energy indices (changes in attenuation of plaque components at 100 kV and 140kV). 42 plaques were analysed by DECT to determine whether DECT increased sensitivity to detect VH-IVUS defined necrotic core. 10 post-mortem coronary arteries were also examined with DECT prior to histological analysis to determine whether DECT increased sensitivity to detect histologically proven necrotic core.
Results
Dual energy indices of necrotic core and fibrous plaque were significantly different (mean: 0.0071 vs. 0.0283, p<0.05). Utilising these increased diagnostic accuracy for DECT to detect necrotic core in 87 segments of post-mortem arteries (sensitivity-64%, specificity-96%) compared with single energy CT (sensitivity-54%, specificity-92%). Sensitivity to detect necrotic core was lower in plaques analysed in-vivo due to the impact of temporal resolution on moving coronaries. However, DECT still provided marginal improvements in sensitivity (45%) compared with single energy CT (39%).
Conclusions
Dual Energy CT has the potential to improve the differentiation of necrotic core and fibrous plaque allowing more accurate non-invasive identification of vulnerable plaque.
Dual-Energy CT Pulmonary Angiography: A New Horizon in the Imaging of Acute Pulmonary ThromboembolismEdward T. D. Hoey, Deepa Gopalan and Nicholas J. ScreatonAudio Available | Share
Pulmonary vein sign (PVS) indicates abnormal pulmonary venous flow on computed tomography pulmonary angiography (CTPA) is a frequent finding in proximal chronic thromboembolic pulmonary hypertension (CTEPH). PVS's occurrence in distal CTEPH and correlation to disease severity is unknown. Using right heart catheterization data, we evaluated the relationship between PVS and CTEPH disease distribution and severity.A total of 93 consecutive CTEPH cases with both CTPA and right heart catheterization were identified in this retrospective multi-institutional study. After excluding 17 cases with suboptimal CTPA, there were 52 proximal and 24 distal CTEPH cases. Blood flow in the major pulmonary veins was graded qualitatively. Subgroup analysis of PVS was performed in 38 proximal CTEPH cases before and after pulmonary endarterectomy.PVS was more frequent in proximal (79%) than distal CTEPH (29%) ( P <0.001). No significant difference was noted in invasive mean pulmonary artery pressure (46±11 and 41±12 mm Hg) or pulmonary vascular resistance (9.4±4.5 and 8.4±4.8 WU) between the 2 groups. In the subgroup analysis, PVS was present in 29/38 patients (76%) before surgery. Postoperatively, 33/38 cases (87%, P <0.001) had normal venous flow (mean pulmonary artery pressure 46±11 and 25; pulmonary vascular resistance 9.2±4.3 and 2.6 WU preop and postop, respectively).PVS is a common feature in proximal but infrequent findings in distal CTEPH. PVS does not correlate with hemodynamic severity. PVS resolution was seen in the majority of patients following successful endarterectomy.
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