"V/Q scans are always intermediate/indeterminate probability" – Fact or fiction

Abstract

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Learning Objectives: 1. Dispel the myth that most V/Q scans are indeterminate probability by showing the data calculated from a retrospective review of 461 patient files. 2. Increase diagnostic confidence by showing data and select VQ scintigraphy images with correlative angiographic studies.

Abstract Body: Methods: Having heard the assertion "V/Q scans are always indeterminate probability", we conducted a retrospective review of 461 patients imaged with 99mTc-MAA and 99mTc-aerosolized DTPA V/Q scintigraphy. This included 247 patients with planar images and 214 patients with SPECT scintigraphy during 2006. By retrospectively correlating difficult to interpret V/Q images with other imaging modalities and the clinical outcome, the significance of confounding V/Q scan findings are better appreciated. This presentation will show the results of our review. Characteristics of V/Q scans interpreted as intermediate probability and having other correlative imaging studies will be displayed to better stratify the V/Q findings into an appropriate probability category. Results: Only 30% of planar and 17% of SPECT studies had an intermediate probability for PE. Of the patients who had intermediate probability for PE on V/Q scan, 35 had correlative angiographic imaging, only 4 patients had positive angiography findings, while 31 were negative. Conclusions: The majority of V/Q scans are not intermediate. SPECT studies appeared to have less intermediate probability diagnosis than planar studies. Most intermediate probability V/Q scans have negative angiography. Reviewing the factors leading to a diagnosis of intermediate probability in the patients of this retrospective study, and correlating with angiographic and clinical outcome may improve diagnostic accuracy of future V/Q scans.