MRS AND MRI OF BREAST CANCER AT VERY HIGH MAGNETIC FIELD

目前还没有一种诊断成像方法能够提供足够的特异性来可靠地区分患者的乳腺良恶性病变。目前，病理评估是获得明确诊断的唯一途径。这项研究将使用磁共振波谱(MRS)和非常高的磁场(4特斯拉)中的新方法来区分乳房病变的良恶性。所需的特异性将从用质子(1H)MRS非侵入性测量的生化特性中获得。这项工作将进一步调查早期的发现，即1H谱中3.2ppm的含胆碱化合物(CHO)可能是乳腺病变恶性的标志。假阳性诊断可能是由3.2ppm的共振引起的，这种共振不是由CHO引起的，而是源于流动性降低和横向弛豫时间(T2)较短的脂质或其他大分子。脑的~1H谱在3.2ppm处发生大分子共振。在本项目中，测量到的固有T2的差异应该可以将3.2ppm的大分子和脂类共振与游离CHO区分开来，从而消除假阳性。所提出的MRS方法和4特斯拉磁场提供的改善的信噪比将显著降低假阴性诊断的发生率。作为确定乳腺病变特征的另一种手段，还将研究MRS测量乳腺病变中葡萄糖代谢的能力，方法是在静脉注射富含稳定13C同位素的葡萄糖后检测13C标记的乳酸。乳腺病变将通过动态增强的二维MRI和高分辨率三维MRI进行可视化。在活检或手术切除之前，将对临床确定的可疑乳腺病变进行MRI和MRS扫描。与病理结果的相关性将揭示建议的MRS测量是否提供了准确识别和描述乳腺患者恶性病变所需的额外特异性。

Currently no diagnostic imaging method offers sufficient specificity to reliably differentiate between benign and malignant breast lesions in patients. Pathologic evaluation is presently the only way to obtain a definitive diagnosis. This research will use new methods in magnetic resonance spectroscopy (MRS) and a very high magnetic field (4 Tesla) to distinguish malignant from benign breast lesions. The required specificity will be gained from biochemical properties measured non- invasively with proton (1H) MRS. This work will further investigate the earlier finding that the presence of choline- containing compounds (Cho) at 3.2 ppm in 1H spectra may be a marker for malignancy in breast lesions. It is hypothesized that false-positive diagnoses can result from a resonance at 3.2 ppm that does not arise from Cho, but instead originates from lipids or other macromolecules with reduced mobility and short transverse relaxation time (T2). A macromolecular resonance at 3.2 ppm has been shown to occur in 1H spectra of brain. In the present project, the measured difference in intrinsic T2 should permit macromolecular and lipid resonances at 3.2 ppm to be distinguished from free Cho, thus eliminating false-positives. The improved SNR offered by the proposed MRS methods and the 4 Tesla magnetic field will significantly reduce the incidence of false-negative diagnoses. As an alternative means to characterize breast lesions, the ability of MRS to measure glucose metabolism in breast lesions will also be investigated, by detecting 13C-labeled lactate following an intravenous injection of glucose enriched with the stable 13C isotope. Breast lesions will be visualized by dynamic contrast-enhanced two-dimensional MRI and high resolution three-dimensional MRI. MRI and MRS scans will be performed on clinically identified suspicious breast lesions prior to biopsy or surgical removal. Correlation with pathologic findings will reveal whether the proposed MRS measurements provide the additional specificity needed to accurately identify and characterize malignant lesions in breast patients.