[A comparison of ventilation/perfusion single photon emission CT and CT pulmonary angiography for diagnosis of pulmonary embolism].

OBJECTIVE: To assess the diagnostic accuracy of ventilation/perfusion (V/Q) single photon emission CT (SPECT) as compared to computed tomographic pulmonary angiography (CTPA) for pulmonary embolism (PE). METHODS: In this prospective multicenter study, 111 patients in whom acute or sub-acute PE was clinically confirmed or suspected were enrolled. The patients underwent one-day method V/Q lung scan (including SPECT and planar imaging) within 3 days before and after completion of CTPA. The European Association of Nuclear Medicine (EANM) guidelines for ventilation/perfusion scintigraphy (2009) reference was used as the evaluation criteria of V/Q SPECT imaging. The refined modified prospective investigation of pulmonary embolism diagnosis (RM-PIOPED) criteria was used for evaluation of planar imaging. According to the direct and indirect signs of PE, the imaging of CTPA was evaluated. All patients were followed for at least 6 months. A diagnosis was finally made by consensus of respiratory physicians, radiologists and nuclear medicine physicians based on the clinical data, laboratory tests, imaging features and follow-up results. The difference among diagnostic methods was evaluated for significance using chi-square test. The receiver operator characteristic (ROC) curve was drawn according to the results of the 3 diagnostic tests. The area under ROC curve (AUC) was calculated and compared. P < 0.05 was considered statistically significant. RESULTS: Among the 111 patients, PE was confirmed in 80, and excluded in 31. The diagnostic sensitivity/specificity/accuracy of V/Q SPECT, planar imaging, and CTPA were 85.9%/93.5%/88.1%, 75.7%/92.9%/81.4%, and 85.5%/90.0%/86.8%, respectively. By ROC curve analysis, the AUC values of V/Q SPECT, planar imaging and CTPA were 0.898, 0.838, and 0.877, respectively; with 95% confidence intervals [CI] 0.831 to 0.966, 0.759 to 0.917, and 0.801 to 0.954, respectively. The area of the fitted smooth ROC curve was statistically significant (P < 0.05) as compared with the area under the reference line. CONCLUSION: The results indicate that SPECT V/Q imaging is superior to V/Q planar scan and CTPA in the diagnosis of PE.

[In vivo noninvasive detection of vulnerable atherosclerotic plaque by (99)Tc(m)-Annexin V imaging in an atherosclerotic rabbit model.].

OBJECTIVE: Apoptosis contributes to the instability of the atherosclerotic (AS) lesions. The vulnerable plaque was identified in vivo by detecting the apoptosis with radiolabeled annexin V in an atherosclerotic rabbit model. METHODS: Eight male New Zealand white rabbits on 2% cholesterol diet for 2 weeks had abdominal aortic balloon injury and fed a 2% cholesterol diet for another 15 weeks (AS group), 3 rabbits fed a normal rabbit chow for 17 weeks without balloon injury served as controls. Annexin V labeled with (99)Tc(m) was then intravenously administered and planar whole-body images were captured using a gamma camera in the left lateral position. The entire length of the abdominal aorta was explanted for ex vivo imaging with gamma camera. The aorta then was divided into several segments according to the severity of AS. The segments were separated weighted and counted in an gamma counter for the absorptive dose of annexin per gram of tissue. Histology examinations were made on specimens. RESULTS: At 2 hours post annexin V injection, clear delineation of radiolabel within the abdominal aorta could be evidenced in vivo gamma imaging. After explanation of the aorta, ex vivo imaging showed a robust uptake of radiotracer in the infradiaphragmatic aorta corresponding to the in vivo images and conforming to the macroscopic distribution of atherosclerotic lesions. The uptake of radiolabel was absent in areas without grossly visible atherosclerotic lesions. The in vivo and ex vivo images identified plaque areas were identical and corresponded histological results on the explanted specimen. The aortic specimen was divided into 18 segments on lesions. The magority of the lesions (14/18) manifested as type IV or type V lesions of AHA classification (vulnerable lesions), except segments 1 - 4, which manifested as type I or type II lesions. The thickness of fibrous cap (TFC) and the ratio of cap and lipid nuclear (RCN) were significantly reversely correlated to the unit radioactivity counts, and the correlation between RCN and the unit radioactivity counts was more significant than that between TFC and the unit radioactivity counts (r = -0.904, P < 0.01, and r = -0.8, P < 0.01). Apoptosis detection (TUNEL): annexin V intake in plaques was positively correlated to apoptotic index(r = 0.651, P = 0.012). CONCLUSION: Noninvasive Annexin V imaging could be used to detect vulnerable atherosclerotic plaques in vivo.