Abstract P2-06-16: Total Choline Measurement in Human Breast Using High-Speed MR Spectroscopic Imaging at 3T

Abstract

Abstract PURPOSE: We developed a novel, quantitative and high-speed MR spectroscopic imaging (MRSI) method to map total Choline (tCho), a sensitive biomarker of breast tumor status, as an adjunct to enhance the limited specificity of routine dynamic-contrast enhanced (DCE) MRI. Quantitative tCho maps measured in 7 minutes were compared with tCho obtained with conventional Single Voxel Spectroscopy (SVS). METHOD AND MATERIALS: Measurements on a total of 18 healthy female subjects (mean age: 25.6±5) were performed using 3T MR scanners (Siemens Trio, Erlangen, Germany) located at the two partner sites equipped with 4-channel breast coil (Siemens, Erlangen, Germany) or 8-channel breast coil (Sentinelle Medical, Toronto, Canada). 2D MRSI data of an entire oblique slice were collected using Proton-Echo-Planar-Spectroscopic-Imaging (PEPSI) [1] with MEGA lipid suppression. Acquisition parameters were: TR/TE=1500ms/125ms, matrix size=32x32, voxel size=2x2x2mm3 (8cc), number of signal averages= 16 with weighted k-space sampling and total acquisition time=7 minutes. PRESS SVS data were acquired with 8 cc voxel size using identical TR/TE and acquisition time. The absolute metabolite concentration was calculated in reference to tissue water (millimoles of tCho per kilogram of solute) using LCModel (s-provencher.com) fitting to estimate the Choline peak baseline and subsequent spectral integration using a Cramer-Rao lower bound threshold of 25%. RESULTS: tCho was detected in 7 of the 15 subjects (47%) in both SVS and PEPSI data. In the PEPSI data sets, tCho was detected in multiple voxels (Fig. 1). Subjects in which tCho was detected exhibited narrower water line width and smaller lipid content than subjects in which tCho was not detectable (2-tailed t-test, P<0.01). The absolute tCho concentrations corrected for relaxation effects in these 7 subjects using SVS and PEPSI was 0.43±0.34 mmol/kg and 0.51±0.19 mmol/kg, respectively. In comparison with SVS data (21.8±8.6Hz), PEPSI spectra demonstrated larger water line width (33.9±12.6Hz) and displayed greater lipid contamination from adipose tissue areas and larger baseline distortion due to the spatial point spread function. CONCLUSION: Despite less favorable shimming and lipid suppression conditions compared to SVS, it is feasible to quantitatively map tCho in healthy breast tissue using high-speed MRSI, with concentration values that are consistent with those from SVS. Studies in breast cancer patients are in progress to assess the feasibility of breast cancer diagnosis and treatment monitoring with MRSI. Results will be reported at the Symposium. The long-term goals are to utilize high-speed MRSI as an early predictor of treatment failure in women undergoing systemic therapy (i.e. chemotherapy, endocrine therapy) for breast cancer and to develop an improved screening protocol for high risk patients. Fig. 1: PEPSI slice localization (left) and spectral array (right) with superimposed LCModel fit and integrated tCho peak Ref: (1) Posse et al. Magn. Reson. Med. 2007;58(2):236-244. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-06-16.