2398. Foot and Ankle DWI – Comparison of Bone Visualization and Pathology on Conventional DWI versus zoomIT DWI: A Prospective Study
Authors * Denotes Presenting Author
  1. Prajwal Gowda *; UT Southwestern Medical School
  2. Flavio Silva; UT Southwestern Medical School
  3. Yin Xi; UT Southwestern Medical School
  4. Avneesh Chhabra; UT Southwestern Medical School
Diffusion weight imaging (DWI) is a useful magnetic resonance imaging (MRI) technique for foot and ankle infections and abscess detection. However, DWI scan distortions are common around small bones of foot and ankle. The aim of this prospective study was to determine if there is an improved imaging with zoomIT DWI sequence versus conventional DWI in visualizing small bones of the foot and ankle, soft tissue abscess, and osteomyelitis.

Materials and Methods:
Institutional review board approval was in place and informed consent was obtained from a consecutive series of patients referred for foot and ankle infections and imaged with both conventional DWI and zoomIT DWI sequence. The parameters used were- repetition time= 5500 ms, time to echo = 98.0 ms, spectral adiabatic inversion recovery (SPAIR) fat saturation, voxel size= 0.8 × 0.8 × 4.0 mm, field of view read= 160 mm, acceleration factor= 2, and b values of 50, 400, 800 s/mm2, zoomIT rotation mode, echo planar factor= 100, and bandwidth= 1612 Hz. One musculoskeletal fellowship trained reader evaluated each sequence in separate settings blinded to the final diagnosis, and assessed quality of fat saturation, motion artifacts, visualization of foot and ankle bones, presence of abscess and osteomyelitis in conjunction with conventional sequences, and calculated contrast to noise (CNR) of the 1st metatarsal base. Paired t-test was used and p value <0.05 was considered significant.

Consecutive series of 43 adult patients, 34 men and 9 women, with a mean age of 53.6 years were included. The zoomIT sequence exhibited superior fat saturation (p = 0.00) with no significant difference in motion artifacts (p = 0.27). Both conventional DWI and zoomIT detected osteomyelitis (23 cases vs. 22 cases) and soft tissue abscess (13 cases vs. 11 cases), respectively. In addition, zoomIT DWI detected 45 more small bones of the foot and ankle (372/472, 78.8%) than conventional DWI (327/472, 69.2%) across all cases. CNR was on average larger for conventional DWI than zoomIT imaging (p < 0.05), however it did not impede anatomic assessment.

The zoomIT DWI aids in visualization of much greater number of bones of foot and ankle due to less distortion compared to conventional DWI with a higher quality fat saturation at the expense of decreased CNR. Thus, it can be considered for evaluation of distal lower extremity DWI.