Spencer Albert Chang MD, Presenter: Nothing to Disclose

Charles C. Matthews MD, Abstract Co-Author: Nothing to Disclose

Dennis Kay MD, Abstract Co-Author: Nothing to Disclose

To compare fixed delay and bolus tracking techniques of contrast administration in CT pulmonary embolism (PE) studies.

Approval and waiver of consent were obtained from our IRB for this retrospective study. Scans were done on either a 4- or 16-detector spiral CT, using either low or iso-osmolar contrast (Omnipaque 350 or Visipaque 320) given at 4cc per second. Fixed delay of 20 seconds was used in Group 1, and bolus tracking with region of interest (ROI) at the main pulmonary artery (MPA) and scan threshold set to 150 Hounsfield units (HU) used in Group 2, with 50 contiguous patients per group. Axial images were reviewed, with ROIs placed over the MPA, right and left pulmonary (RPA and LPA), lower lobar (RLL and LLL), basal segmental (R seg and L seg), and subsegmental (R subseg and L subseg arteries, for a total of nine ROIs per patient. Lower lobes were chosen because they are the most frequent site of PE. Vascular enhancement between the two groups at each of the vascular levels was compared using the unpaired t test. Studies were interpreted by one of our department’s CT staff radiologists as positive, negative, or non-diagnostic (cases where pulmonary arteries were inadequately shown to the segmental level), and χ² test was used to compare these interpretations.

Mean attenuation values (HU) with standard deviation for Groups 1 and 2 are as follows: 342.5 +/- 91 and 304.4 +/- 98.8 (P0.05) at RPA, 337.2 +/- 91.6 and 295.3 +/- 92.3 (P0.05) at R seg, 330.6 +/- 100.4 and 284.7 +/- 93.3 (P0.05) at L subseg. There was no statistically significant difference (p>0.05) in the occurrence of non-diagnostic interpretations between the groups (4 out of 50 in Group 1, and 9 out of 50 in Group 2).

There is no significant difference in diagnostic quality with standard delay versus bolus tracking for CT pulmonary embolism studies.

Chang, S, Matthews, C, Kay, D, CT Pulmonary Angiography for Evaluation of Pulmonary Embolus: Fixed Delay versus Bolus Tracking Techniques of Contrast Administration.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4411413.html