Contribution of V/Q SPECT to planar scintigraphy in the diagnosis of pulmonary embolism

Aim: To evaluate the feasibility of V/QSPECT and analyze its contribution to planar V/Q lung scintigraphy in the diagnosis of pulmonary embolism (PE). Material and methods: A total of 109 patients with suspected PE showing Wells score >2 and elevated D-dimer were studied. The V/Q could not be completed in 7 patients, so they were excluded. Ventilation and perfusion scans were done using Technegas and Tc-99m-MAA. Planar study included 8 projections on a 256 x 256 matrix and 128 projections on a 128 x 128 matrix were acquired for the SPECT study, applying an iterative method. Planar images were interpreted according to modified PIOPED criteria, and SPECT by the guidelines of the EANMMI. The results with both techniques were compared. Results: V/Q planar scintigraphy and SPECT could be performed in 102 patients. V/Qplanar scintigraphy was considered diagnostic in 39 of the 102 patients, and non-diagnostic in 63. Of the 39 diagnostic studies, 31 were reported as high probability of PE and 8 as normal. Of the 63 non-diagnostic, 26 corresponded to intermediate, 29 to low, and 8 to very low probability. The SPECT study was diagnostic in 97 and indeterminate in only 5. All patients with a high probability planar scintigraphy had a positive SPECT. In the 8 patients with a normal planar scintigraphy SPECT was negative in 5 and positive in 3. In the 63 patients with a non-diagnostic planar scintigraphy SPECT was diagnostic in 58 of them, positive in 17 and negative in 41. Conclusion: V/Q SPECT is a feasible technique as it was performed in 102 of the 109 patients who were enrolled in the study (94%). The addition of V/Q SPECT to planar V/Q decreases the number of non-diagnostic reports from 62% in planar scintigraphy to 4.9% in SPECT. Therefore, V/QSPECT should be included in the diagnosis approach of PE due to its high diagnostic yield. (C) 2013 Elsevier Espana, S.L. and SEMNIM. All rights reserved.