Mark Allan Ahlman MD, Presenter: Nothing to Disclose

Veit Sandfort MD, Abstract Co-Author: Nothing to Disclose

Davis M. Vigneault BS, Abstract Co-Author: Nothing to Disclose

Nehal Mehta, Abstract Co-Author: Nothing to Disclose

David A. Bluemke MD, PhD, Abstract Co-Author: Research support, Siemens AG

Changes in FDG arterial activity within the most diseased segment target to background ratio (MDS TBR) has been used to measure response to treatment. MDS TBR is calculated by averaging the maximum arterial activity of 3 contiguous axial slices centered at the slice that has the highest standardized uptake value (SUV), divided by the mean venous activity. For a normal adult patient population, we evaluate the MDS value and location using differing image reconstruction algorithms and methods for calculation.

FDG PET-CT images were obtained at 2 hrs uptake time with a Siemens Biograph 128 mCT. Transaxial reconstruction of the descending aorta at 1.5mm slice thickness resulted in 200-300 images covering the descending aorta (DAo) from the arch to the bifurcation. PET-CT images were obtained in 17 hyperlipidemic subjects (age 56.8 ± 12.8, 59% female). Image reconstruction (256x256 matrix) was performed using both high definition (HD) and time-of-flight (TOF) algorithms. For either reconstruction, aortic MDS TBR was identified and the corresponding MDS TBR at the same slice location was measured in the second reconstruction. Any difference in MDS slice location was recorded. The MDS TBR was measured on both reconstructions using both 3- and 5- contiguous slices for comparison.

MDS was located on the same slice between HD and TOF volumes in only 2/17 (11%) of subjects, and was 7.4 ± 6.6 cm apart on average. There was no difference in MDS TBR between HD and TOF when the same slice measurement method was used (e.g. 3-slice HD vs 3-slice TOF). However, there was higher value of 3-slice MDS TOF compared to 5-slice methods for either reconstruction (p<0.01). Specific to location, where TOF MDS TBR was found for 3- and 5-slice methods, the reference HD MDS TBR was lower (p<0.001 and p<0.001, respectively). Similarly, where found on HD images, the reference MDS TBR on the TOF reconstruction was lower (p<0.001 and p<0.01, respectively).

MDS location and value is highly dependent on reconstruction algorithm. Independent of MDS TBR length, values will regress to a lower value on the same slice on alternate PET reconstructions evaluated.

Designed to quantify changes in FDG PET arterial inflammation in research as well as for clinical application for cardiovascular risk stratification, we evaluate the MDS TBR with different reconstruction algorithms and measurement methods.

Ahlman, M, Sandfort, V, Vigneault, D, Mehta, N, Bluemke, D, Limitations of the Most Diseased Segment for Use in 18FDG Vascular Imaging of the Aorta.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014145.html