title: Pulmonary thromboembolism: a retrospective study on the examination of 991 patients by ventilation/perfusion SPECT using Technegas.
abstract: OBJECTIVE
  Conventional planar ventilation/perfusion (V/P)-imaging in those patients suspected of suffering from pulmonary thromboembolism (PTE) is of limited diagnostic value. It is the purpose of this retrospective study to determine whether the use of V/P-SPECT using Technegas might reduce the rate of those diagnostic uncertainties and might lead to better results.
  
  
  METHODS
  991 patients (660 female, 331 male, age 18-90, mean 60), referred to our laboratory with suspected PTE, were examined as follows: patients inhaled 37 MBq of Technegas in the supine position and a SPECT-acquisition was started. Following SPECT-completion, 185 MBq 99mTc-MAA was injected intravenously. SPECT was then repeated. Coronal and transverse ventilation and perfusion SPECT-slices were reconstructed and compared section by section. 85 patients underwent control scans by the same technique at a mean interval of 22 months after the original scans.
  
  
  RESULTS
  As the SPECT images in almost all cases made a clear match/mismatch decision possible, we categorized all patients as embolic (PTE+) if there was at least one mismatching defect, and as non embolic (PTE-) if there were none. Our results were: PTE+: 178 patients (18%), PTE-: 808 patients (81%), uncertain: 5 patients (0.5%), if 34 triple-match defects are included: 39 patients (3.9%). 46 patients, categorized as PTE+ underwent a control V/P scan after anticoagulant therapy. In 44 of these patients, PTE was confirmed by the controls. In a control group of 39 PTE- patients, control scans were unchanged in 38 cases. From these observations we can calculate a sensitivity of 96% and a specificity of 97%.
  
  
  CONCLUSIONS
  We conclude that V/P imaging can be improved significantly by V/P SPECT using Technegas.
authors.affiliation: Röntgeninstitut, Bremerhaven/Germany. lemb-donnem@t-online.de
authors.forename: M
authors.initials: M
authors.lastname: Lemb
authors.forename: H
authors.initials: H
authors.lastname: Pohlabeln
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011655:Pulmonary Embolism / Q000145:classification / Q000000981:diagnostic imaging* / Q000503:physiopathology; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D013670:Sodium Pertechnetate Tc 99m; D015899:Tomography, Emission-Computed, Single-Photon; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*
chemical_list: D019275:Radiopharmaceuticals; C056708:Technegas; D013670:Sodium Pertechnetate Tc 99m