In S. Seo MD, Presenter: Nothing to Disclose

Won Jun Park MD, Abstract Co-Author: Nothing to Disclose

Kevin Tsai MD, Abstract Co-Author: Nothing to Disclose

CT angiography (CTA) is the most frequently performed diagnostic tool for PE because of reduced invasiveness and greater availability. It has high specificity (SP) for PE while its sensitivity (SN) is limited and high radiation exposure limits its routine use, particularly on young women. V/Q has high SN for PE, but has low SP, particularly when CXR is abnormal. V/Q is performed when CTA is contraindicated, technically unsatisfactory or inconclusive. SPECT increases SN, but further decreases SP, whereas SPECT/CT improves SP significantly. CXR is important in determining which study should be performed - V/Q when CXR is normal and CTA when CXR is abnormal. The authors have tried to determine whether SPECT/CT has high diagnostic accuracy for PE, even among patients with abnormal CXRs.

Between July 1, 2012 and December 31, 2013, 897 (348 men and 549 women, aged 20 - 101; median age 64.5 years old) patients had V/Q. 835 patients had V/Q as the initial study (Gp 1) while 62 patients had V/Q performed after a suboptimal or inconclusive CTA (Gp 2). SPECT/CT was performed in patients with high probability (HP) V/Q and abnormal CXR and in patients with intermediate probability (IP) or low probability (LP) V/Q with normal or abnormal CXR. SPECT/CT could not be performed in 145 patients because they were too wide, contracted, claustrophobic, or refusing the procedures.

In104 of 107 (97.2%) patients with abnormal CXRs, SPECT/CT confirmed HP PE while 3 were downgraded to LP or VLP. In 8 of 12 patients with IP PE, SPECT/CT downgraded the findings to LP or very low probability (VLP). In 48 of 66 patients with LP PE, SPECT/CT downgraded the findings to VLP.

CXR findings are crucial, mainly for the HP V/Q. When CXR is normal, SPECT/CT is not needed. In our series, 46 of 62 (74.2%) patients in Gp 2 had normal CXRs, a situation in which V/Q could be the initial study of choice rather than CTA. When CXR is abnormal, SPECT/CT should be added, as supported by our study results.

V/Q has no limitation for renal dysfunction and allergy to iodine and delivers less radiation to patients. When CXR is normal, V/Q should be used as the initial study for PE. When CXR is abnormal, the use of SPECT/CT increases both SN and SP for PE, improving the diagnostic accuracy. In any institute with SPECT/CT capability, V/Q could be used as the initial study for PE, even when CXR is abnormal.

Seo, I, Park, W, Tsai, K, Abnormal CXR and Lung Ventilation and Perfusion Scan (V/Q)? The Role of SPECT/CT in the Evaluation of Pulmonary Embolism (PE) in Patients with Abnormal CXR.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14008296.html