Objective analysis of tomographic ventilation-perfusion scintigraphy in pulmonary embolism

Am J Respir Crit Care Med. 2007 Jun 1;175(11):1173-80. doi: 10.1164/rccm.200608-1110OC. Epub 2007 Mar 15.


Rationale: Ventilation-perfusion scintigraphy is highly sensitive for pulmonary embolism (PE), but its clinical usefulness is limited by its nondiagnostic rate. Objective analysis of single photon emission computed tomography (SPECT) three-dimensional scintigraphy may improve its diagnostic performance compared with subjective interpretation.

Objectives: To determine the diagnostic accuracy of objective SPECT analysis in PE.

Methods: We determined the ventilation/perfusion (V(.)/Q(.)) relationship using SPECT scintigraphy in a retrospective cohort of 73 patients. Measures of V(.)/Q(.) heterogeneity (logSD(Q(.)), logSD(V(.)), logSD(VQR)), including a novel parameter, the weighted median V(.)/Q(.) value, were calculated. Using receiver operating characteristic (ROC) analysis, each parameter's diagnostic accuracy was determined. The weighted median V(.)/Q(.) value was then assessed prospectively in a second cohort of 50 patients.

Measurements and main results: In cohort 1, all parameters of V(.)/Q(.) heterogeneity were higher in patients with PE (p < 0.002). The weighted median V(.)/Q(.) had the highest area under the ROC curve (0.93; 95% confidence interval, 0.87-0.98). When applied to the prospective cohort, the area under the ROC curve was 0.87 (95% confidence interval, 0.75-0.99), with diagnostic cutoff values having negative and positive predictive values of 96 and 83%, respectively. In the retrospective and prospective cohorts, 82 and 73% of initially reported intermediate or low probability scans had diagnostic weighted median V(.)/Q(.) values, with 90 and 100% accuracy, respectively.

Conclusions: Objective analysis of SPECT scintigraphy has a high diagnostic accuracy in patients with suspected PE. Objective analysis has the potential to reduce the number of nondiagnostic scan results, and may be useful for quantifying V(.)/Q(.) mismatch in other pulmonary disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Confidence Intervals
  • Female
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Pulmonary Embolism / diagnostic imaging*
  • Pulmonary Embolism / physiopathology*
  • ROC Curve
  • Reproducibility of Results
  • Retrospective Studies
  • Severity of Illness Index
  • Tomography, Emission-Computed, Single-Photon / methods*
  • Ventilation-Perfusion Ratio / physiology