Diagnostic evaluation of planar and tomographic ventilation/perfusion lung images in patients with suspected pulmonary emboli

Planar lung ventilation/perfusion scintigraphy (V/P-PLANAR) is a standard method for diagnosis of pulmonary embolism (PE). The goals of this study were to test whether the diagnostic information of ventilation/perfusion tomography (V/P-SPET) applied in clinical routine might enhance information compared with V/P-PLANAR and to streamline data processing for the demands of clinical routine. This prospective study includes 53 patients suspected for PE referred for lung scintigraphy. After inhalation of Tc-99m-DTPA planar ventilation imaging was followed by tomography, using a dual-head gamma camera. Tc-99m-MAA was injected i.v. for perfusion tomography followed by planar imaging. Patients were examined in supine position, unchanged during V/P tomography. Two reviewers evaluated V/P-PLANAR and V/P-SPET images separately and randomly. Mismatch points were calculated on the basis of extension of perfusion defects with preserved ventilation. Patients were followed up clinically for at least 6 months. With V/P-SPET the number of patients with PE was higher and 53% more mismatch points were found. In V/P-SPET interobserver variation was less compared with V/P-PLANAR. Ancillary findings were observed by both techniques in half of the patients but more precisely interpreted with V/P-SPET. V/P-SPET shows more and better delineated mismatch defects, improved quantification and less interobserver variation compared with V/P-PLANAR. V/P-SPET is amenable to implementation for clinical routine and suitable even when there is demand for a high patient throughput.