• Pierre-Yves Le Roux, Philippe Robin, Aurélien Delluc, Ronan Abgral, Xavier Palard, Valentin Tissot, Agnes Morel, Jean Rousset, Francis Couturaud, Grégoire le Gal, and Pierre-Yves Salaun.
• 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.
• Nucl Med Commun. 2015 Sep 1; 36 (9): 922-30.

ObjectivesThe 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?MethodsA 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.ResultsOn 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.ConclusionFor 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.

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