title: Lung scintigraphy in the diagnosis of pulmonary embolism: current methods and interpretation criteria in clinical practice.
abstract: BACKGROUND
  In current clinical practice lung scintigraphy is mainly used to exclude pulmonary embolism (PE). Modified diagnostic criteria for planar lung scintigraphy are considered, as newer scitigraphic methods, especially single photon emission computed tomography (SPECT) are becoming more popular.
  
  
  METHODS
  Data of 98 outpatients who underwent planar ventilation/perfusion (V/Q) scintigraphy and 49 outpatients who underwent V/Q SPECT from the emergency department (ED) were retrospectively collected. Planar V/Q images were interpreted according to 0.5 segment mismatch criteria and revised PIOPED II criteria and perfusion scans according to PISA-PED criteria. V/Q SPECT images were interpreted according to the criteria suggested in EANM guidelines. Final diagnosis of PE was based on the clinical decision of an attending physician and evaluation of a 12 months follow-up period.
  
  
  RESULTS
  Using 0.5 segment mismatch criteria and revised PIOPED II, planar V/Q scans were diagnostic in 93% and 84% of cases, respectively. Among the diagnostic planar scans readings specificity for 0.5 segment mismatch criteria was 98%, and 99% for revised PIOPED II criteria. V/Q SPECT showed a sensitivity of 100% and a specificity of 98%, without any non-diagnostic cases. In patients with low pretest probability for PE, planar V/Q scans assessed by 0.5 segment mismatch criteria were diagnostic in 92%, and in 85% using revised PIOPED II criteria, while perfusion scintigraphy without ventilation scans was diagnostic in 80%.
  
  
  CONCLUSIONS
  Lung scintigraphy yielded diagnostically definitive results and is reliable in ruling out PE in patients from ED. V/Q SPECT has excellent specificity and sensitivity without any non-diagnostic results. Percentage of non-diagnostic results in planar lung scintigraphy is considerably smaller when 0.5 segment mismatch criteria instead of revised PIOPED II criteria are used. Diagnostic value of perfusion scintigraphy according to PISA-PED criteria is inferior to combined V/Q scintigraphy; the difference is evident especially in patients with low pretest probability for PE.
authors.affiliation: Department for Vascular Diseases, Ljubljana University Medical Centre, Ljubljana, Slovenia.
authors.forename: Ajda
authors.initials: A
authors.lastname: Skarlovnik
authors.affiliation: Department for Nuclear Medicine, Celje General Hospital, Celje, Slovenia.
authors.forename: Damjana
authors.initials: D
authors.lastname: Hrastnik
authors.affiliation: Department for Nuclear Medicine, Ljubljana University Medical Centre, Ljubljana, Slovenia.
authors.forename: Jure
authors.initials: J
authors.lastname: Fettich
authors.affiliation: Department for Nuclear Medicine, Ljubljana University Medical Centre, Ljubljana, Slovenia.
authors.forename: Marko
authors.initials: M
authors.lastname: Grmek
keywords: 0.5 segment mismatch criteria; interpretation criteria; lung scintigraphy; pulmonary embolism