title: Diagnosis of pulmonary embolism: conventional ventilation/perfusion SPECT is superior to the combination of perfusion SPECT and nonenhanced CT.
abstract: BACKGROUND
  Ventilation/perfusion single-emission photon CT (V/P-SPECT) is widely used to detect pulmonary embolism (PE). Any pathological deficit on P-SPECT with a corresponding unremarkable V-SPECT is considered an embolism. This means that a deficit on P-SPECT with a corresponding deficit on the ventilation scan correlates with other lung pathologies such as pneumonia, bullous emphysema or tumor. In principle, it is possible to identify any of these lung pathologies on nonenhanced chest CT and so this technique has the potential to replace V-SPECT in the diagnosis of PE. Today, SPECT/CT hybrid imaging systems are increasingly applied in clinical routines.
  
  
  OBJECTIVE
  We investigated whether embolism can be diagnosed using a combined P-SPECT/CT hybrid imaging approach without V-SPECT.
  
  
  METHODS
  Ninety-three patients with clinically suspected embolism were investigated with standard V/P-SPECT and a nonenhanced CT scan on a combined SPECT/CT system. A diagnosis of embolism was based on V/P-SPECT (gold standard). P-SPECT/CT datasets were blinded and analyzed without any knowledge of the V-SPECT data. The accuracy of P-SPECT/CT was compared to the gold standard.
  
  
  RESULTS
  Embolism was diagnosed in 24/93 patients using V/P-SPECT. In total, 57 lung lobes were affected. P-SPECT/CT significantly (p < 0.01) overdiagnosed embolism in nonaffected patients. In total, 36 cases with 88 affected lung lobes were shown. The sensitivity was 95.8%, the specificity 82.6%, the false-negative rate 4.2% and the false-positive rate 17.3%.
  
  
  CONCLUSIONS
  Our results demonstrate that a nonenhanced CT scan in a novel hybrid imaging system cannot replace V-SPECT in the scintigraphy-based diagnosis of PE. V-SPECT increases specificity and reduces the number of false-positive results when compared to 'perfusion-only' SPECT/CT.
authors.affiliation: Department of Pneumology and Respiratory Critical Care Medicine, Thoraxklinik Heidelberg, University of Heidelberg, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Palmowski
authors.forename: Ute
authors.initials: U
authors.lastname: Oltmanns
authors.forename: Michael
authors.initials: M
authors.lastname: Kreuter
authors.forename: Felix M
authors.initials: FM
authors.lastname: Mottaghy
authors.forename: Moritz
authors.initials: M
authors.lastname: Palmowski
authors.forename: Florian F
authors.initials: FF
authors.lastname: Behrendt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D057186:Comparative Effectiveness Research; D003951:Diagnostic Errors / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D014692:Ventilation-Perfusion Ratio