Kousi Evanthia, Smith Joely, Ledger Araminta E, Scurr Erica, Allen Steven, Wilson Robin M, O'Flynn Elizabeth, Pope Romney J E, Leach Martin O, Schmidt Maria A
CR-UK and EPSRC Cancer Imaging Centre, Royal Marsden NHS Foundation Trust, Institute of Cancer Research, Sutton, Surrey, SM2 5PT, UK.
Brighton and Sussex University Hospitals NHS Trust, Brighton, BN2 5BE, UK.
Med Phys. 2018 Jan;45(1):287-296. doi: 10.1002/mp.12652. Epub 2017 Nov 30.
To propose a method to quantify T and contrast agent uptake in breast dynamic contrast-enhanced (DCE) examinations undertaken with standard clinical fat-suppressed MRI sequences and to demonstrate the proposed approach by comparing the enhancement characteristics of lobular and ductal carcinomas.
A standard fat-suppressed DCE of the breast was performed at 1.5 T (Siemens Aera), followed by the acquisition of a proton density (PD)-weighted sequence, also fat suppressed. Both sequences were characterized with test objects (T ranging from 30 ms to 2,400 ms) and calibration curves were obtained to enable T calculation. The reproducibility and accuracy of the calibration curves were also investigated. Healthy volunteers and patients were scanned with Ethics Committee approval. The effect of B field inhomogeneity was assessed in test objects and healthy volunteers. The T of breast tumors was calculated at different time points (pre-, peak-, and post-contrast agent administration) for 20 patients, pre-treatment (10 lobular and 10 ductal carcinomas) and the two cancer types were compared (Wilcoxon rank-sum test).
The calibration curves proved to be highly reproducible (coefficient of variation under 10%). T measurements were affected by B field inhomogeneity, but frequency shifts below 50 Hz introduced only 3% change to fat-suppressed T measurements of breast parenchyma in volunteers. The values of T measured pre-, peak-, and post-contrast agent administration demonstrated that the dynamic range of the DCE sequence was correct, that is, image intensity is approximately directly proportional to 1/T for that range. Significant differences were identified in the width of the distributions of the post-contrast T values between lobular and ductal carcinomas (P < 0.05); lobular carcinomas demonstrated a wider range of post-contrast T values, potentially related to their infiltrative growth pattern.
This work has demonstrated the feasibility of fat-suppressed T measurements as a tool for clinical studies. The proposed quantitative approach is practical, enabled the detection of differences between lobular and invasive ductal carcinomas, and further enables the optimization of DCE protocols by tailoring the dynamic range of the sequence to the values of T measured.
提出一种方法，用于量化在采用标准临床脂肪抑制MRI序列进行的乳腺动态对比增强（DCE）检查中的T值和对比剂摄取，并通过比较小叶癌和导管癌的增强特征来证明所提出的方法。
在1.5T（西门子Aera）下进行标准的乳腺脂肪抑制DCE检查，随后采集质子密度（PD）加权序列，同样进行脂肪抑制。用测试物体（T值范围为30毫秒至2400毫秒）对两个序列进行表征，并获得校准曲线以进行T值计算。还研究了校准曲线的重现性和准确性。在伦理委员会批准下对健康志愿者和患者进行扫描。在测试物体和健康志愿者中评估了B场不均匀性的影响。对20例患者（10例小叶癌和10例导管癌）在不同时间点（对比剂给药前、峰值和给药后）计算乳腺肿瘤的T值，并比较两种癌症类型（Wilcoxon秩和检验）。
校准曲线被证明具有高度重现性（变异系数低于10%）。T值测量受B场不均匀性影响，但低于50Hz的频率偏移对志愿者乳腺实质脂肪抑制T值测量仅引入3%的变化。对比剂给药前、峰值和给药后测量的T值表明DCE序列的动态范围是正确的，即在该范围内图像强度大约与1/T成正比。小叶癌和导管癌对比剂给药后T值分布宽度存在显著差异（P<0.05）；小叶癌对比剂给药后T值范围更广，这可能与其浸润性生长模式有关。
这项工作证明了脂肪抑制T值测量作为临床研究工具的可行性。所提出的定量方法是实用的，能够检测小叶癌和浸润性导管癌之间的差异，并进一步通过根据测量的T值调整序列的动态范围来优化DCE方案。
