SPECT ventilation perfusion scanning with the addition of low-dose CT for the investigation of suspected pulmonary embolism.

Single-photon emission computed tomography (SPECT) ventilation perfusion (V/Q) scanning with low-dose computed tomography (LDCT) is an emerging imaging technique for investigation of suspected pulmonary embolism (PE). We aimed to estimate diagnostic utility of the combined technique using results from all patients referred in 2009 compared with final diagnosis and 6-month follow-up status. PE was diagnosed in 28 of 106 patients (26%), including in 2 of 80 (2%) with negative SPECT V/Q and LDCT. The estimated negative predictive value of SPECT V/Q for PE was 97%. LDCT was abnormal in 43 (41%) patients, including 41 patients who had negative SPECT V/Q. In 29 (27%) patients, LDCT provided information on alternative pathologies that accounted for presenting symptoms, and the combined technique had a diagnostic yield of 52%.