ENHANCED ACCURACY AND REPRODUCIBILITY IN REPORTING OF LUNG SCINTIGRAMS BY A SEGMENTAL REFERENCE CHART

The diagnostic probability of pulmonary embolic disease is based on th e recognition of unmatched segmental perfusion defects. Although inter observer and intraobserver reproducibility have been studied, accuracy has been an elusive goal due to the lack of a gold standard. We inves tigated the accuracy and reproducibility of reporting in a virtual sci ntigraphic model of the lungs, with and without the use of a lung segm ental reference chart. Methods: A Monte Carlo package was used to mode l lung scintigraphy from a digital phantom of the human lungs. An idea l lung segmental reference chart was created from the phantom. Five ex perienced nuclear medicine physicians reported a set of all possible d efects involving 100% of a segment, without and with the chart. A furt her set of defects involving 45%-55% of a segment in the lower lobes w as investigated using the chart. Results: There was a significant impr ovement in accuracy (from 48% to 72%) and intraobserver agreement (fro m 61% to 77%) with the chart. The accuracy of reporting defects in the upper and middle lobes was consistently better than that in the lower lobes. There was no significant difference between the accuracy of re porting large defects and that of reporting moderate defects in the lo wer lobes. Conclusion: The lung segmental reference chart significantl y improves both the accuracy and reproducibility of reporting lung sci ntigrams; however, although reporting in the lung bases is improved, a bsolute accuracy is substantially less than that in the upper and midd le lobes. This emphasizes the need for caution because the lung bases are the most common site of embolic disease.