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Diffusion Tensor Imaging and High Definition Fiber Tracking for Monitoring Cortical Neurointegration after Human Hand Transplantation
Vijay Gorantla, MD, PhD; Vince Lee, BA; Anto Bagic; Fernando Boada, PhD; Alexander Spiess; Joseph Losee; University of Pittsburgh
University of Pittsburgh Medical Center, Pittsburgh, PA, USA

PURPOSE

Hand transplantation is a clinical reality with over 80 transplants performed to date. The dual goals of hand transplantation are to reduce toxic effects of immunosuppression and maximize functional recovery. Much work has focused on peripheral nerve regeneration after hand transplantation. However, cortical neurointegration could be key to outcomes in amputees receiving these innovative transplants. Here, we present for the first time a study using an MRI based diffusion tensor imaging (DTI) protocol for high definition fiber tracking (HDFT) of cortical neurointegration after unilateral hand transplantation.

METHOD AND MATERIALS

Scanning was performed under IRB protocol using a whole body TrioTim 3 Tesla scanner. The patient was scanned at 4 time points: pre-transplant (75 days prior), and post transplant (58, 121, and 187 days). Diffusion Tensor Images (DTIs) were acquired in 256 isotropically directions using a spin-echo echo-planar sequence with the following parameters: TE/TR=91/8900 ms, Voxel = 2 x 2 x 2 mm, Resolution = 128 x 128 x 67. b-value ranged from 0 (b0) to 1000s/mm2. DTI for each time point was reconstructed and Fractional Anisotropy (FA) for each voxel calculated using the formula in Figure. DTI-Studio and MRI-Studio image processing software were used for HDFT. Region of interest (ROI) was the pyramidal motor neuron tract. Fiber densities in ROI were analyzed and normalized for simple comparison between different time points.

RESULTS

Rendered left hemisphere ROI fibers with normalized fiber density data are shown in Figure. A steady increase in fiber number, density, length/reach, and normalized fiber fraction was seen with time, especially comparing the 58-day to 187 day testing. These trends in cortical fiber morphology correlated well with functional and electrophysiologic outcomes at these time points in terms of motor function (total motion, grip and pinch strength) and sensory return (touch, temperature and vibratory perception).

CONCLUSION

Our study demonstrates that central neurointegration of fiber tracts after hand transplantation occurs concurrently with peripheral neuroregeneration and may be critical for functional recovery after these transplants.

CLINICAL RELEVANCE/APPLICATION

This is the first implementation of HDFT with DTI in evaluating fiber parameters and recovery after hand transplantation and holds value in both screening and monitoring of patient functional outcomes


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