Säll Cornelia, Lind Emelie, Einarsson Emma, Turkiewicz Aleksandra, Englund Martin, Peterson Pernilla
Imaging and Physiology, Skåne University Hospital, Lund, Sweden.
Department of Medical Radiation Physics, Lund University, Lund, Sweden.
MAGMA. 2025 Jul 24. doi: 10.1007/s10334-025-01280-0.
To evaluate the effects of excluding fatty tissue in QSM of human knee cartilage.
Gradient echo images from 18 knee-healthy volunteers were acquired, from which chemical shift corrected field perturbation maps were calculated. Based on these, QSM maps were reconstructed using morphology enabled dipole inversion and one of three masking alternatives: (1) excluding no tissue, (2) excluding bone marrow, and (3) excluding all fatty tissues. The slope of a linear regression [ppm/%] between susceptibility values and the relative distance from the bone surfaces was used as a measurement of contrast between cartilage layers. The average differences in slopes between methods are reported with 95% confidence intervals.
The expected susceptibility differences between cartilage layers from literature were observed for all tested reconstruction techniques. However, smaller slopes (average difference (confidence interval)) were detected when either all fatty tissue (- 0.090 (- 0.121, - 0.059) ppm/%) or bone marrow (- 0.088 (- 0.121, - 0.055) ppm/%) was excluded from reconstruction.
All tested methods result in adequate image quality in QSM of knee cartilage. However, exclusion of fatty tissue decreased the susceptibility contrast between cartilage layers. Assuming that phase contributions from chemical shift are addressed, inclusion of fatty tissue may be preferable.
评估在人体膝关节软骨定量磁化率成像（QSM）中排除脂肪组织的效果。
采集了18名膝关节健康志愿者的梯度回波图像，并据此计算出化学位移校正后的场扰动图。在此基础上，使用形态学增强偶极子反演和三种掩蔽方法之一重建QSM图：（1）不排除任何组织；（2）排除骨髓；（3）排除所有脂肪组织。将磁化率值与距骨表面相对距离之间的线性回归斜率[ppm/%]用作软骨层之间对比度的测量指标。报告了各方法之间斜率的平均差异及其95%置信区间。
所有测试的重建技术均观察到了文献中报道的软骨层之间预期的磁化率差异。然而，在重建过程中排除所有脂肪组织（-0.090（-0.121，-0.059）ppm/%）或骨髓（-0.088（-0.121，-0.055）ppm/%）时，检测到的斜率较小。
所有测试方法在膝关节软骨QSM中均能产生足够的图像质量。然而，排除脂肪组织会降低软骨层之间的磁化率对比度。假设化学位移的相位贡献得到解决，纳入脂肪组织可能更可取。
