Diffusion tensor imaging as a tool to assess the structure of lower limb muscles invisible on T1- and T2-weighted images in the course of the chronic phase of peripheral artery disease

A patient with peripheral artery disease (PAD) was selected randomly from a group of 55 patients from the N-O CLI clinical trial, registered under EudraCT No. 2016-004684-40, conducted in accordance with GCP requirements. A 76-year-old woman was referred to the Outpatient Clinic of the Vascular Surgery Department of the John Paul II Hospital in Krakow, due to critical ischemia of the right lower limb. She was offered an experimental method of treatment using mesenchymal stem cells (MSCs). The patient was submitted to magnetic resonance imaging (MRI) examination before (E1) and after (E2) the intraarterial and intramuscular injections of CardioCell based on mesenchymal stem cells (MSCs) or placebo which was produced according to the rules of good manufacturing practices at Jagiellonian University Collegium Medicum, Pracownia-Bank Tkanek i Komórek (PBTiK) Zakładu Transplantologii UJ CM (license no. 145/0323/15), in a double-blind RCT. Therapy encompassed three injections every seven weeks and after 398 days after E1 the condition of the lower extremities was once again checked by MRI. The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of John Paul II hospital in Krakow. Positive opinion no. 1072.61201.17.2017 dated on 21/12/2017 was issued by the Bioethics Committee of the Jagiellonian University. Muscles’ condition was evaluated based on T1- (T1WI) and T2-weigthed images (T2WI; Figure 1), obtained transversely on a 3T MR system (Siemens Skyra 3 T, Erlangen, Germany) using an eight-channel TORSO body coil with the application of turbo spin echo (TSE) and turbo inversion recovery magnitude (TIRM) with fat suppression pulse sequences, respectively. Complementarily, diffusion tensor imaging (DTI) was performed using the Echo Planar Imaging (EPI) sequence with six diffusion gradient directions. In the DTI protocol, b-value = 350 s/mm2, number of scans, NoS = 1, while slice thickness was equal to 8 mm. The BSD-DTI calibration method [1, 2] was applied before the quantitative analysis, for which it was shown recently to have substantial applicability [3]. The following DTI parameters were analyzed: the second and third eigenvalues (2 and 3, respectively), mean (MD), longitudinal (DL) and transversal (DT; mean of 2 and 3) diffusivity, and fractional anisotropy (FA), by using the in-house BSD-DTI software (BSD-DTI ver. 2.0, AGH UST, Krakow, Poland). For comparison, mean...


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