Abstract: Aim: To evaluate the feasibility of V/Q SPECT 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 99mTc-MAA. Planar study included 8 projections on a
256
×
256 matrix and 128 projections on a 128
×
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/Q planar 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/Q SPECT should be included in the diagnosis approach
of PE due to its high diagnostic yield.
