Albert Yoo MD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: To describe a new artifact in CT pulmonary angiography (CTPA) which can both mimic and hide pulmonary emboli, and to demonstrate that it is related to physiologic variation in blood return to the right heart. Methods and Materials: In a retrospective study of 234 patients from January 2001 to December 2002 who had both CTPA and a close follow-up diagnostic pulmonary angiogram, or in one case CTPA, 7 cases were identified which contained a flow artifact consisting of a segment of the pulmonary arterial tree which demonstrates relatively decreased contrast attenuation and which is between areas of increased attenuation both proximally and distally. In each case, density measurements in Hounsfield units (HU) were made in the area of decreased attenuation, the areas of higher attenuation both proximally and distally, the superior vena cava (SVC), inferior vena cava (IVC), right atrium (RA), and right ventricle (RV). To test the hypothesis that the artifact arises from increased flow of unopacified blood from the IVC, the relative IVC contribution to the right heart was determined in the cases and in age- and sex-matched controls who had a diagnostic CTPA with no evidence of the artifact or a pulmonary embolus. The relative IVC contribution was calculated by equating density in the RA and RV to a weighted average of the densities of the SVC and IVC. This assumes that the SVC and IVC are the sole contributors of flow to the right heart. Results: In all cases, the artifact is seen bilaterally. The mean densities (+/- standard deviation) of the low attenuation region, the proximal region of higher attenuation, and the distal region of higher attenuation are 146 HU (+/- 60 HU), 292 HU (+/- 97 HU), and 452 HU (+/- 141 HU), respectively. In the patients with the artifact, the average relative IVC contributions to the RA and RV are 80.1% and 79.5%, respectively. In the control patients, the values for the RA and RV are 52.8% and 55.5%, respectively. Using a two-tailed paired t-test, the difference between the cases and controls is significant for both the RA (p=0.02) and RV (p=0.02). Conclusion: The artifact, which we term the "stripe sign," represents inhomogeneous mixing of contrast from the SVC. We have shown that it is not a random occurrence but rather a flow-related phenomenon that is associated with increased IVC contribution to the right side of the heart, which likely causes poor dispersion of contrast from the SVC. The insights gained from this work suggest various means of improving CTPA technique to prevent this potential pitfall in the CTPA diagnosis of pulmonary embolus.       Questions about this event email: ajyoo@partners.org

Yoo MD, A, CTPA Pulmonary Artery Flow Artifact: Pitfall in the Diagnosis of Pulmonary Embolism.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3103890.html