David T. Fetzer MD, Presenter: Nothing to Disclose

Alessandro Furlan MD, Abstract Co-Author: Nothing to Disclose

Amol Patil, Abstract Co-Author: Nothing to Disclose

Naomi Sarah Schwarz MD, Abstract Co-Author: Nothing to Disclose

Yun Robert Sheu MD, MS, Abstract Co-Author: Nothing to Disclose

Kyongtae Tyler Bae MD, PhD, Abstract Co-Author: Patent agreement, Covidien AG, Saint Louis, MO Patent agreement, Bayer AG, Pittsburgh, PA Expert Advisory Committee, Bracco Group, Princeton, NJ

To compare clot burden measures (quantitative PE volume with Qanadli Pulmonary Artery Obstruction Index (PAOI) and Mastora scores) as they relate to clot burden and location, and to investigate reasons for discordance.

This retrospective study was IRB approved. Study cohort consisted of 641 patients diagnosed with acute PE by CTPA (334F, 307M, mean age, 60 years; range, 17-102 years) during year 2007. Images were reviewed in consensus by two radiologists who measured PE burden by assessing clot location and grade of obstruction to calculate semi-quantitative scores Qanadli and Mastora General (Mas_G), Central (Mas_C), and Peripheral (Mas_P). Quantification of PE volume was also performed using our in-house semi-automated segmentation program. Association between semi-quantitative scores and volumetric data was analyzed using Pearson coefficient and linear regression. Analysis was repeated for patients with exclusively peripheral (segmental and subsegmental) clot. In addition, patients with single clots were assessed independently for association between clot volume and location.

Volumetric measurement correlated stongly with Qanadli (r=0.70), Mas_G (r=0.78), Mas_C (r=0.82) and Mas_P (r=0.67). However, when considering patients with peripheral clot only (N=320, segmental or subsegmental), correlation decreased with Qanadli (r=0.53) and Mas_G (r=0.77), though increased with Mas_P (r=0.78). When considering subsegmental clots only (N=106), all scoring methods correlated poorly (r=0). When only central PE burden was considered (N=33, proximal or lobar), mean clot volume was 1507±561cc. For peripheral PE burden only, mean volume was 474±43cc.  Mean clot volume was 260±330cc for single peripheral PE and 162±173cc for exclusively subsegmental PE. Number of segmental clots required to equal a single, central clot in volume was 5.2, while the number of subsegmental clots was 12.9.

When regarding clot volume as a measure of embolism burden, quantitative volumetric measurement is a more reliable method. With increased peripheral distribution of clot burden, semi-quantitative scores correlate less with volume measurement, thereby underestimating subsegmental PE burden.

As a measure of clot burden, volumetric quantification is more accurate; prior methods may considerably underestimate contribution of peripheral PEs, thus potentially compromising clinical relevance.

Fetzer, D, Furlan, A, Patil, A, Schwarz, N, Sheu, Y, Bae, K, Assessment of Clot Burden in Acute Pulmonary Embolism (PE) on CT Pulmonary Angiogram (CTPA): Semi-quantitative Scoring Methods vs Fully Quantitative Volume Measurement.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9012847.html