title: Additional value of combining low-dose computed tomography to V/Q SPECT on a hybrid SPECT-CT camera for pulmonary embolism diagnosis.
abstract: OBJECTIVE
  The aim of the study was to assess the potential interest of combining a low-dose computed tomography (ldCT) to ventilation/perfusion (V/Q) single-photon emission computed tomography (SPECT) for the diagnosis of pulmonary embolism (PE). We addressed three main questions: Could ldCT be used in substitution to ventilation SPECT? Could ldCT improve the diagnostic performance of V/Q SPECT? Could ldCT provide alternative diagnoses to PE?
  
  
  METHODS
  A total of 393 patients previously analysed in a management outcome study that aimed at assessing the safety of V/Q SPECT for PE diagnosis were assessed. All patients underwent an ldCT under the same SPECT-computed tomography camera, which was not used at the time of initial interpretation. Three retrospective analyses were performed: Q SPECT combined with ldCT, V/Q SPECT combined with ldCT and ldCT only.
  
  
  RESULTS
  On the basis of initial V/Q SPECT interpretation, 110 (28%) patients were positive and 283 (72%) were negative for PE.With Q SPECT-ldCT, 139 (35%) patients were positive and 254 (65%) were negative, with 55 (19%) discrepancies when compared with V/Q SPECT. Of the 283 patients with negative V/Q SPECT, 42 were positive with V/Q SPECT-ldCT, and among the 110 patients with positive V/Q SPECT 13 were negative with V/Q SPECT-ldCT. On using V/Q SPECT-ldCT, 97 (25%) patients were positive and 296 (75%) were negative, with 13 (3%) discrepancies when compared with V/Q SPECT (all had had a positive V/Q SPECT but a negative V/Q SPECT-ldCT). Finally, 67 (24%) ldCT scans showed a potential alternative diagnosis to PE.
  
  
  CONCLUSIONS
  For PE diagnosis with lung SPECT, the use of ldCT in substitution to ventilation SPECT is associated with a high risk of overdiagnosis. The diagnostic value of ldCT in addition to V/Q SPECT remains unclear. Further studies are needed to determine its potential role in PE diagnosis.
authors.affiliation: aBrest University bEA3878 (GETBO) IFR 148 Departments of cNuclear Medicine dInternal Medicine and Chest Diseases eRadiology, Brest University Hospital fDepartment of Radiology, HIA Clermont Tonnerre gINSERM CIC 05-02 IFR 148, Brest, France hOttawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Le Roux
authors.forename: Philippe
authors.initials: P
authors.lastname: Robin
authors.forename: Aurélien
authors.initials: A
authors.lastname: Delluc
authors.forename: Ronan
authors.initials: R
authors.lastname: Abgral
authors.forename: Xavier
authors.initials: X
authors.lastname: Palard
authors.forename: Valentin
authors.initials: V
authors.lastname: Tissot
authors.forename: Agnes
authors.initials: A
authors.lastname: Morel
authors.forename: Jean
authors.initials: J
authors.lastname: Rousset
authors.forename: Francis
authors.initials: F
authors.lastname: Couturaud
authors.forename: Grégoire
authors.initials: G
authors.lastname: le Gal
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Salaun
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011829:Radiation Dosage; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014692:Ventilation-Perfusion Ratio; D055815:Young Adult