Medical Physics Unit, McGill University, Montreal, Quebec, Canada.
Department of Physics, McGill University, Montreal, Quebec, Canada.
Magn Reson Med. 2021 Aug;86(2):1029-1044. doi: 10.1002/mrm.28694. Epub 2021 Feb 28.
To propose a method for voxel-wise estimation of cell radii and volume fractions of two cell populations when they coexist in the same MR voxel using the combination of diffusion-weighted MRI and microstructural modeling.
Microstructure models were investigated using diffusion data simulated with the matrix method for a range of microstructures mimicking tumor tissue with two cell populations, using acquisition parameters available on preclinical scanners. The effect of noise was investigated for a subset of these microstructures. The accuracy and precision of the estimated radii and volume fractions for large and small cells were evaluated by comparing the estimates to their true values. The stability of model fitting was characterized by the percentage of accepted fits.
The estimation accuracy and precision, and thus the ability to robustly distinguish the two cell populations, depended on the microstructural properties and SNR. For a SNR of 50, a minimum difference of 3 μm between the radius of the large and small cell populations was required for differentiation. Proposed modifications to the two cell population microstructure model, including constrained fits, improved the stability of fits.
This proof-of-concept study proposed a diffusion MRI-based method for voxel-wise estimation of cell radii and volume fractions of two cell populations when they coexist in the same MR voxel. The ability to reliably characterize tissue with two cell populations opens exciting avenues of potential applications in both tumor diagnosis and treatment monitoring.
提出一种方法，用于在同一体素中存在两种细胞群体时，通过结合扩散加权 MRI 和微结构建模，对细胞半径和两种细胞群体的体积分数进行体素估计。
使用矩阵方法模拟扩散数据，对一系列微结构进行研究，这些微结构模拟了具有两种细胞群体的肿瘤组织，使用了临床前扫描仪上可获得的采集参数。对这些微结构中的一部分进行了噪声效应的研究。通过将估计值与真实值进行比较，评估了大细胞和小细胞的估计半径和体积分数的准确性和精度。通过接受拟合的百分比来表征模型拟合的稳定性。
估计的准确性和精度，从而能够稳健地区分两种细胞群体，取决于微结构特性和 SNR。对于 SNR 为 50，需要大细胞和小细胞群体的半径之间有最小 3μm 的差异才能进行区分。对两种细胞群体微结构模型的修改建议，包括约束拟合，提高了拟合的稳定性。
这项概念验证研究提出了一种基于扩散 MRI 的方法，用于在同一体素中存在两种细胞群体时对细胞半径和两种细胞群体的体积分数进行体素估计。能够可靠地描述具有两种细胞群体的组织为肿瘤诊断和治疗监测的潜在应用开辟了令人兴奋的途径。
