title: Software-Based Hybrid Perfusion SPECT/CT Provides Diagnostic Accuracy When Other Pulmonary Embolism Imaging Is Indeterminate.
abstract: OBJECTIVE
  To investigate the diagnostic performance of perfusion single-photon emission computed tomography/computed tomography (Q-SPECT/CT) in patients suspected to have pulmonary embolism (PE) but with indeterminate computed tomographic pulmonary angiography (CTPA) or planar ventilation/perfusion (V/Q) scans.
  
  
  METHODS
  This retrospective study included two groups of patients. Group I consisted of 49 patients with nondiagnostic CTPA. These 49 patients underwent subsequent V/Q scans. Further Q-SPECTs were obtained in patients with indeterminate planar images and fused with existing CTPA. Group II consisted of 182 non-CTPA patients with indeterminate V/Q scans. These 182 patients underwent further Q-SPECT and separate noncontrast low-dose CT chest. Fusion Q-SPECT/CT scans were obtained through FDA-approved software and interpreted according to published criteria as positive, negative, or indeterminate for PE. Upon retrospective analyses, the final diagnosis was made using composite reference standards including all available clinical and imaging information for at least 6-month follow-up.
  
  
  RESULTS
  In group I patients, 1 was positive, 24 were negative, and another 24 (49 %, 24/49) were indeterminate. In the subsequent 24 Q-SPECT/CTPAs, 4 were positive, 19 were negative, and 1 was indeterminate (4.2 %, 1/24). In group II patients, 9 (4.9 %, 9/182) were indeterminate, 33 were positive, and 140 were negative. The combined nondiagnostic rate for Q-SPECT/CT was only 4.9 % (10/206). There was six false-negative and one false-positive Q-SPECT/CT examinations. The sensitivity, specificity, and positive and negative predictive value of Q-SPECT/CT were 85.7 % (36/42), 99.4 % (153/154), 97.3 % (36/37) and 96.2 % (153/159), respectively.
  
  
  CONCLUSIONS
  Q-SPECT/CT improves the diagnostic rate with promising accuracy in diagnosing PE that yields a satisfactory clinical verdict, especially when the CTPA and planar V/Q scan are indeterminate.
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Nishant
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Xie
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Winnie
authors.initials: W
authors.lastname: Mar
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Anderson
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Carney
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Mehta
authors.affiliation: Section of Pulmonary section, Department of Medicine, University of Illinois Hospital & Health Sciences System, Chicago, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Machado
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Blend
authors.affiliation: Department of Radiology, University of Illinois Hospital & Health Sciences System, 1740 W Taylor St. MC 931, Chicago, IL 60612 USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
keywords: CTPA; Pulmonary Embolism; Q-SPECT/CT; V/Q