Radionuclide lung scans for suspected acute pulmonary embolism: Single photon emission computed tomography (SPECT) or hybrid SPECT/CT?

Introduction Hybrid single photon emission computed tomography (SPECT) with CT (SPECT/CT) may improve diagnostic accuracy in suspected acute pulmonary embolism, but further research is needed. We evaluated whether the use of attenuation correction and/or the depiction of lung pathology with hybrid SPECT/CT could significantly reduce potentially false-positive ventilation-perfusion (VQ) SPECT studies or obviate the need for a ventilation study. Methods Two specialists (S1 and S2) reviewed prospectively acquired VQ SPECT/CT in 165 patients. Studies were reported using standard criteria and compared to VQ SPECT and Q SPECT/CT. Results S1 and S2 recorded positive VQ SPECT in 54 (32.7%) and 42 (25.6%) cases, respectively. Hybrid SPECT/CT showed non-embolic pathology in 41 (S1) and 46 (S2) patients, but compared to VQ SPECT, neither hybrid SPECT/CT nor attenuation correction SPECT/CT had significantly fewer positive studies. Intra-observer agreement with VQ SPECT/CT was almost perfect (k = 0.91 for S1 and k = 0.95 for S2; P < 0.001), but not with Q SPECT/CT (k = 0.4 for S1 and k = 0.62 for S2; P < 0.001). Inter-observer agreement was moderate for VQ SPECT (k = 0.65) and VQ SPECT/CT (k = 0.63). Conclusion In our study, hybrid VQ SPECT/CT did not reduce the number of potentially false-positive VQ SPECT, nor did the CT obviate the need for a ventilation study. Thus, the routine use of hybrid SPECT/CT for suspected pulmonary embolism is not justified.