Comparison between pulmonary ventilation and thoracic low-dose multidetector CT in the follow-up of pulmonary embolism

Objectives Planar ventilation/perfusion (V/Q) scintigraphy is currently the standard method in the follow-up of patients with pulmonary embolism. With the advent of hybrid SPECT/CT systems it is possible to study the airway lung space both anatomically and physiologically. We hypothesized that anatomical findings using the low-dose CT component may potentially replace the physiological findings of the ventilation scan. Therefore, the aim of the study was to assess the agreement between the planar ventilation scan and the low-dose CT scan.

Methods Fifty-three consecutive patients underwent planar V/Q and lung perfusion SPECT/CT imaging as follow-up of acute pulmonary embolism. A hybrid double headed SPECT/CT system equipped with a six slice multidetector scanner was used (Philips Precedence). Planar ventilation images and low-dose CT images were separately interpreted by a nuclear medicine physician. Kappa statistics were calculated to determine agreement between both methods.

Results Only 15 (28.3%) of the patients showed one or more ventilation defects and/or morphological changes in the CT, with a total of 20 abnormalities registered (2 ventilation defects with no corresponding CT changes; 6 CT changes with no corresponding ventilation defects; and 12 matched ventilation and CT changes). Thirty-eight patients showed no defects on the planar ventilation scan or CT scan. The overall agreement between the planar ventilation scan and the low-dose CT scan was good (kappa =0,657, p<0.0001).

Conclusions Low-dose CT scan used for lung perfusion SPECT/CT imaging in the follow-up of patients with acute pulmonary embolism shows good agreement with planar ventilation scan, thus potentially allowing to skip the ventilation scan, reducing total exploration time and cost, and increasing patient comfort.