PurposeTo compare interpretation of traditional planar ventilation–perfusion lung scan images with planar images reformatted from single photon emission computed tomography (SPECT) data using two different techniques. MethodsPlanar and SPECT ventilation–perfusion (V/Q) data were acquired from 50 patients referred with suspected pulmonary embolism. In addition to traditional six-view planar images, six-view planar images were also generated from SPECT data using two methodologies: an angular summing technique (angular summed planar images) and a forward projection technique (reprojected planar images). Three experienced nuclear medicine clinicians reviewed the images in a blinded, randomized fashion. Results were analysed by comparing the two reprojected techniques with the traditional true planar scans, examining for differences in the defects seen (number, type and confidence), and the impact on final clinical interpretation. ResultsCompared with true planar scintigraphy, angular summed images demonstrated fewer mismatched defects (P<0.0001), while the reprojected planar images had more matched defects (P=0.013). In addition, there was a significant change in the clinical interpretation of the angular summed planar images resulting in clinicians perceiving a decreased likelihood of pulmonary embolism (P<0.016). No such difference in interpretation was observed for the reprojected planar images. ConclusionsAngular summed planar images result in a perceived decreased likelihood of pulmonary embolism compared with true planar images. In contrast, while reprojected planar images result in an increased number of matched defects compared to true planar scans, there was no change in the clinical interpretation. Caution should be exercised when interpreting SPECT derived angular summed planar images in isolation.

A whole body bone scan with SPECT/CT of the thoracolumbar spine was performed on a patient with metastatic renal cell carcinoma. Bone scan demonstrated widespread skeletal metastases. In addition, CT identified a lytic lesion on the right side of T12 that was at risk for causing nerve root compression but was “cold” on bone scan. This was confirmed on MRI. Bone lesions associated with renal cell carcinoma are typically osteolytic and generally very aggressive, with a relatively high incidence of cold lesions. This case demonstrates that SPECT/CT not only allows more accurate lesion localization, but provided additional information complementary to SPECT alone.