Relation between lung perfusion defects and intravascular clots in acute pulmonary thromboembolism: Assessment with breath-hold SPECT–CT pulmonary angiography fusion images

Pulmonary enhancement imaging with dual energy CT for the detection of pulmonary embolism in a rabbit model: comparison to perfusion planar scintigraphy, SPECT and SPECT-CT modalities

RATIONALE AND OBJECTIVES

Pulmonary enhancement imaging (PEI) derived from dual-energy computed tomographic (CT) imaging has been used to detect perfusion defects from pulmonary embolism (PE). The purpose of this study was to compare the ability of PEI, planar, single photon-emission CT (SPECT) perfusion scintigraphy, and SPECT-CT fusion images to detect perfusion defect in a PE rabbit model.

MATERIALS AND METHODS

A PE model was made by injecting Gelfoam into the femoral veins of rabbits (n = 16). After 2 hours, 16 experimental rabbits and three control rabbits underwent contrast-enhanced dual-energy CT scans, from which PEI and CT pulmonary angiography were created, and planar, SPECT, and SPECT-CT fusion images were then obtained and evaluated. Pathologic determination of locations and numbers of lung lobes with PE were recorded. The sensitivity and specificity of the above-mentioned modalities were calculated using the histopathologic results as reference standards.

RESULTS

Emboli were present in 31 pulmonary lobes and absent in 64 lung lobes in histopathologic analysis. With the histopathologic findings as the gold standard, sensitivities and specificities of PEI, planar, SPECT, and SPECT-CT fusion images to detect PE were 100% and 96.9%, 71.0% and 84.4%, 77.4% and 90.6%, and 74.2% and 93.8%, respectively. McNemar's tests showed that PEI had higher diagnostic accuracy for the detection of PE than three scintigraphic images (all P values < .05), while three scintigraphic images had similar diagnostic accuracy (all P values = NS).

CONCLUSIONS

This study demonstrates that PEI from dual-energy CT imaging can provide higher diagnostic accuracy for detecting PE than planar, SPECT, and SPECT-CT fusion images in a rabbit model.

Application of breath-holding SPECT with high-speed-rotation technique in hepatic-function scintigraphy

Recently, a new method for acquiring SPECT data in deep inspiratory breath hold with a high-speed rotation (HSR-SPECT) technique was developed for pulmonary perfusion scintigraphy. Our purpose in this study was to apply this method to hepatic-function scintigraphy. A phantom study was performed for determining data acquisition times. The coefficient of variation (CV) value was used for evaluating nonuniformity of radioactivity in the liver area. Data acquisition times were determined based on the CV value. According to the results of the phantom study, this method needs at least ten projection data sets for acquiring sufficient counts for a proper diagnosis. Under clinical conditions, breath-holding HSR-SPECT can suppress the respiratory motion effects, better than the conventional method can. In addition, the fusion images made from breath-holding HSR-SPECT images match excellently with CT images.