David A Tovar BS, Abstract Co-Author: Nothing to Disclose

Wang Zhan, Abstract Co-Author: Nothing to Disclose

David Soltysik PHD, Abstract Co-Author: Nothing to Disclose

Sunder S. Rajan PhD, Presenter: Nothing to Disclose

We have described the construction and use of a head-sized fMRI phantom that can generate consistent T2-weighted signal changes. Applications for this fMRI phantom include quantitatively evaluating scanner reproducibility and comparing the contrast of different BOLD imaging pulse sequences.

There have been various attempts at producing useful quality control fMRI phantoms, but none are yet standardized. A useful phantom will need to demonstrate the BOLD imaging pulse sequence’s ability to detect small changes in T2*, over a nominal imaging volume. In addition, the phantom should contain material that recreates the physiological T1 and T2 values of grey matter, be usable across different scanners, have minimal susceptibility artifacts, and yield reproducible signal changes. In this study, an eight-compartment cylindrical fMRI phantom was tested.

We have described the construction and use of a head-sized fMRI phantom that can generate consistent T2-weighted signal changes. Applications for this fMRI phantom include quantitatively evaluating scanner reproducibility and comparing the contrast of different BOLD imaging pulse sequences.

The cylinderical phantom (length/diameter=23/19 cm) was made using acrylic material. The cylinder was divided into eight wedge-shaped compartments using partitions, with a long handled for manual rotation. The compartments were filled with nickel-doped agar gel with alternating concentrations (1.4%, 1.6%), to produce a difference in T2 values. The agar gel was made by previously published methods. T1, T2 mapping, and EPI imaging were performed using a Siemens TRIO 3T system. The EPI parameters used were the same as that for BOLD imaging (TR/TE/slice/FA=3s/50ms/5mm/90). During the EPI run, a signal change was induced in a block-design paradigm by rotating the phantom 45° between each pair of blocks. EPI scan of the phantom showed minimal artifacts within a usable volume covered by 20 slices. Some distortion was seen in the outer slices. Alternate compartments had mean T1/T2 values of 1551 ± 54/100 ± 12 ms and 1521 ± 49/89 ± 14 ms, respectively. The mean EPI signal difference between the compartments was 5.0 ± 4.2%. The EPI contrast to noise ratio was studied as a function of TE (21 to 60 ms) and was found to increase from 5.9 to 10.2.

Tovar, D, Zhan, W, Soltysik, D, Rajan, S, A Description of a Novel Phantom for fMRI Quality Control.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12028886.html