Azma Yassine N, Boci Nada, Abramowicz Katarzyna, Russo Luca, Orton Matthew R, Tunariu Nina, Koh Dow-Mu, Charles-Edwards Geoffrey, Collins David J, Winfield Jessica M
MRI Unit, The Royal Marsden NHS Foundation Trust, London, UK.
Division of Radiotherapy and Imaging, The Institute of Cancer Research, London, UK.
Eur Radiol. 2025 Apr 11. doi: 10.1007/s00330-025-11564-7.
This study aimed to assess the accuracy of fat fraction estimation with clinically available Dixon sequences in normal-appearing marrow and bone metastases in the pelvis of metastatic prostate cancer patients.
A prospective single-centre study was conducted with metastatic prostate cancer patients and healthy volunteers. Linearity and bias of fat fraction estimates from clinically available Dixon sequences were assessed against a 6-point PDw gradient echo (q-Dixon) sequence measuring the reference standard proton density fat fraction. Lesion fat fraction estimates were cross-compared using the Friedman test. Repeatability in volunteers was evaluated with Bland-Altman plots. Sensitivity of fat fraction estimates using TSE-Dixon sequences to specific absorption rate (SAR) related modifications were evaluated with correlation plots.
Thirty-three patients were recruited for this study. Significant (p < 0.05) absolute bias (12.4%) was demonstrated in the T1-weighted (T1w) Dixon measurements against the q-Dixon. Significant differences (p < 0.05) between fat fraction estimates provided by the T1w Dixon and PDw Dixon sequences were observed in 13 active and 6 treated lesions. Repeatability coefficients for fat fraction estimates ranged from 5.9 to 9.0% in the pelvic tissues of healthy volunteers. Reduction of slice number with repetition time for SAR had the greatest effect, reaching a maximum difference in fat fraction of 14.7% from the q-Dixon for the T2w-TSE Dixon in bone marrow.
T1w Dixon methods can detect post-treatment changes but remain confounded by relaxation time biases. While all Dixon methods showed good repeatability, careful choice of SAR-related modifications is critical to maintaining accuracy for PD- and T2-weighted TSE sequences.
Question The clinical validity of signal-weighted fat fraction estimates versus proton density fat fraction for characterising metastatic bone lesions has not been fully assessed. Findings T1-weighted Dixon sequences in line with whole-body MRI international guidelines demonstrate significant fat fraction bias, particularly in lesions and muscle. Clinical relevance Fat fraction estimation using T1-weighted Dixon sequences recommended in international guidelines are highly sensitive to relaxation time biases, making underlying physiological changes potentially ambiguous.
本研究旨在评估在转移性前列腺癌患者骨盆中，使用临床可用的狄克逊序列对外观正常的骨髓和骨转移灶进行脂肪分数估计的准确性。
对转移性前列腺癌患者和健康志愿者进行了一项前瞻性单中心研究。将临床可用狄克逊序列的脂肪分数估计值的线性和偏差与测量参考标准质子密度脂肪分数的6点PDw梯度回波（q-狄克逊）序列进行对比评估。使用弗里德曼检验对病变脂肪分数估计值进行交叉比较。通过布兰德-奥特曼图评估志愿者中的重复性。使用相关图评估TSE-狄克逊序列的脂肪分数估计值对特定吸收率（SAR）相关修改的敏感性。
本研究招募了33名患者。T1加权（T1w）狄克逊测量相对于q-狄克逊显示出显著（p < 0.05）的绝对偏差（12.4%）。在13个活跃病变和6个已治疗病变中，观察到T1w狄克逊序列和PDw狄克逊序列提供的脂肪分数估计值之间存在显著差异（p < 0.05）。健康志愿者骨盆组织中脂肪分数估计值的重复性系数范围为5.9%至9.0%。对于SAR，切片数量随重复时间的减少影响最大，骨髓中T2w-TSE狄克逊与q-狄克逊相比，脂肪分数的最大差异达到14.7%。
T1w狄克逊方法可以检测治疗后的变化，但仍受弛豫时间偏差的困扰。虽然所有狄克逊方法都显示出良好的重复性，但仔细选择与SAR相关的修改对于维持PD加权和T2加权TSE序列的准确性至关重要。
问题 尚未充分评估信号加权脂肪分数估计值与质子密度脂肪分数在表征转移性骨病变方面的临床有效性。发现 符合全身MRI国际指南的T1加权狄克逊序列显示出显著的脂肪分数偏差，特别是在病变和肌肉中。临床意义 国际指南中推荐的使用T1加权狄克逊序列进行脂肪分数估计对弛豫时间偏差高度敏感，使得潜在的生理变化可能变得模糊不清。
