The Added Value of Low-Dose CT to SPECT V/Q Scan in Diagnosis of Pulmonary Embolism

Abstract

Abstract Background The purpose of this study was to compare the known V/Q images that carried out as traditional planar scintigraphy using Prospective Investigation of Pulmonary Embolism Diagnosis (modified PIOPED II) interpretation criteria to the potential benefit and diagnostic ability of combining Low Dose-CT to perfusion SPECT, without contrast agent administration, for the detection of pulmonary embolism (PE). Material and methods Eighty-one patients presented with symptoms suggestive of pulmonary embolism. In all 81 cases, planar perfusion lung scans with SPECT/CT were conducted, whereas complementing planar ventilation was performed in 27 cases. SPECT/CT findings in all cases made the diagnosis based on the segmental and sub-segmental perfusion defects regarding the 2009 EANM guideline for PE diagnosis. V/Q scans were compared to SPECT/CT findings for 27 patients according to Modified PIOPED II. Results Among the normal perfusion cases with no defect by planar scan, 48 patients (59.3%) still entirely normal on SPECT. SPECT add small segmental defects in 16 patients (19.8%), 2 patients of them converted from low to high probability for PE. Nevertheless, the increase in the number of defects discovered throughout the whole research group when compared to planar scan indicates that SPECT has added value in defect detection. In the diagnosis of PE, lung perfusion scintigraphy paired with CT conducted by hybrid SPECT/CT gamma cameras offers a good diagnostic effectiveness. SPECT/CT was shown to be more accurate than planar scintigraphy, with a sensitivity of 100.0%, specificity of 85.7%, and accuracy of 92.6%. Conclusions Including low-dose CT in lung perfusion SPECT demonstrated increased diagnostic utility of perfusion scan with enhanced negative predictive value to rule out PE. The use of low-dose CT improves the test's diagnostic yield by providing information on other diseases that explain the presenting symptoms. Specificity is increased, allowing a single imaging technique to detect PE with high accuracy while also ruling out other possible causes of chest discomfort and SOB.