Overview
ISO/TR 16379:2014 - "Tissue-engineered medical products - Evaluation of anisotropic structure of articular cartilage using DT (Diffusion Tensor)-MR Imaging" - is a Technical Report that compiles methods and reference data for non‑invasive structural evaluation of knee articular cartilage using Diffusion Tensor Magnetic Resonance Imaging (DT‑MRI / DT‑MR Imaging). It is intended to support longitudinal assessment of regenerative therapies (tissue‑engineered medical products) for articular cartilage disease by characterizing collagen fiber orientation (anisotropy) in vivo.
Key Topics and Technical Requirements
- Scope and purpose: Provides measurement procedures and reference results to evaluate therapeutic courses following cartilage transplantation, focusing on the anisotropic three‑layer collagen architecture of hyaline cartilage.
- DT‑MRI principle: Uses diffusion tensors to infer water molecule motion; in fibrous tissues this motion aligns with collagen fibers, enabling assessment of fiber orientation and anisotropy.
- Primary measurement indices:
- Fractional Anisotropy (FA) - index of structural anisotropy (0–1). The report describes pixel‑based FA mapping and a luminance‑to‑FA conversion used in its examples.
- Mean Diffusivity (MD) - average diffusion coefficient across principal tensor axes.
- Imaging protocol guidance: Includes practical notes on setting parameters such as sequence (SE‑EPI), field strengths (1.5 T and 3 T examples), coils, field of view (FOV), matrix, TR/TE, slice thickness, number of averages (NA), b‑value, number of motion probing gradient (MPG) directions (minimum six), voxel size and SNR trade‑offs, and use of parallel imaging to shorten scan time.
- Measurement methods: Defines recommended slice selection (sagittal plane at inferior lateral femoral condyle), pixel sampling (example: three pixels along cartilage surface × five pixels in depth), and depth normalization formula (depth % = D / T × 100).
- Data quality considerations: Discusses effects of voxel size, SNR, TR, NA, b‑value and MPG direction count on reliability of anisotropy measures.
Practical Applications and Users
- Clinicians & Radiologists: longitudinal, non‑invasive monitoring of cartilage regeneration after cell/tissue transplants.
- MRI technologists: protocol optimization for DT‑MRI of knee cartilage (parameter trade‑offs and coil/sequence choices).
- Researchers in regenerative medicine and biomechanics: quantitative assessment of collagen fiber reorganization and structural maturation of engineered cartilage.
- Medical device and tissue‑engineered product developers, and regulatory bodies: standardized imaging endpoints to support clinical evaluation and comparability.
Related Standards (if applicable)
- Complementary ISO and medical imaging standards on MRI safety, image acquisition, and implants for surgery may be relevant when implementing DT‑MRI protocols and integrating imaging endpoints into clinical studies.
Keywords: ISO/TR 16379:2014, DT‑MRI, Diffusion Tensor MR Imaging, articular cartilage, anisotropy, fractional anisotropy, mean diffusivity, regenerative medicine, tissue‑engineered medical products, knee cartilage, MRI parameters.