title: Noncontrast perfusion single-photon emission CT/CT scanning: a new test for the expedited, high-accuracy diagnosis of acute pulmonary embolism.
abstract: BACKGROUND
  Standard ventilation and perfusion (V˙/Q˙) scintigraphy uses planar images for the diagnosis of pulmonary embolism (PE). To evaluate whether tomographic imaging improves the diagnostic accuracy of the procedure, we compared noncontrast perfusion single-photon emission CT (Q˙-SPECT)/CT scans with planar V˙/Q˙scans in patients at high risk for PE.
  
  
  METHODS
  Between 2006 and 2010, most patients referred for diagnosis of PE underwent both Q˙-SPECT/CT scan and planar V˙/Q˙scintigraphy. All scans were reviewed retrospectively by four observers; planar scans were read with modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II and Prospective Investigative Study of Pulmonary Embolism Diagnosis (PISA-PED) criteria. On Q˙-SPECT/CT scan, any wedge-shaped peripheral perfusion defect occupying &gt; 50% of a segment without corresponding pulmonary parenchymal or pleural disease was considered to show PE. The final diagnosis was established with a composite reference standard that included ECG, ultrasound of lower-extremity veins, D-dimer levels, CT pulmonary angiography (when available), and clinical follow-up for at least 3 months.
  
  
  RESULTS
  One hundred six patients with cancer and mean Wells score of 4.4 had sufficient follow-up; 22 patients were given a final diagnosis of PE, and 84 patients were given a final diagnosis of no PE. According to PIOPED II, 13 studies were graded as intermediate probability. Sensitivity and specificity for PE were 50% and 98%, respectively, based on PIOPED II criteria; 86% and 93%, respectively, based on PISA-PED criteria; and 91% and 94%, respectively, based on Q˙-SPECT/CT scan. Seventy-six patients had additional relevant findings on the CT image of the Q˙-SPECT/CT scan.
  
  
  CONCLUSIONS
  Noncontrast Q˙-SPECT/CT imaging has a higher accuracy than planar V˙/Q˙imaging based on PIOPED II criteria in patients with cancer and a high risk for PE.
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Alice
authors.initials: A
authors.lastname: Lorenzoni
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Josef J
authors.initials: JJ
authors.lastname: Fox
authors.affiliation: Body Imaging Section, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Rademaker
authors.affiliation: Department of Radiology and Pulmonary Disease Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Vander Els
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Grewal
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: H William
authors.initials: HW
authors.lastname: Strauss
authors.affiliation: Molecular Imaging and Therapy Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY. Electronic address: schoderh@mskcc.org.
authors.forename: Heiko
authors.initials: H
authors.lastname: Schöder
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D057210:Delayed Diagnosis; D003937:Diagnosis, Differential; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis*; D015203:Reproducibility of Results; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014692:Ventilation-Perfusion Ratio