Purpose:To prospectively compare an investigational version of a complex-based chemical shift-based fat fraction magnetic resonance (MR) imaging method with MR spectroscopy for the quantifi cation of hepatic steatosis. Materials and Methods:This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained before all studies. Fifty-fi ve patients (31 women, 24 men; age range, 24-71 years) were prospectively imaged at 1.5 T with quantitative MR imaging and single-voxel MR spectroscopy, each within a single breath hold. The effects of T2* correction, spectral modeling of fat, and magnitude fi tting for eddy current correction on fat quantifi cation with MR imaging were investigated by reconstructing fat fraction images from the same source data with different combinations of error correction. Single-voxel T2-corrected MR spectroscopy was used to measure fat fraction and served as the reference standard. All MR spectroscopy data were postprocessed at a separate institution by an MR physicist who was blinded to MR imaging results. Fat fractions measured with MR imaging and MR spectroscopy were compared statistically to determine the correlation ( r 2 ), and the slope and intercept as measures of agreement between MR imaging and MR spectroscopy fat fraction measurements, to determine whether MR imaging can help quantify fat, and examine the importance of T2* correction, spectral modeling of fat, and eddy current correction. Two-sided t tests (signifi cance level, P = .05) were used to determine whether estimated slopes and intercepts were signifi cantly different from 1.0 and 0.0 , respectively. Sensitivity and specifi city for the classifi cation of clinically signifi cant steatosis were evaluated. Results:Overall, there was excellent correlation between MR imaging and MR spectroscopy for all reconstruction combinations. However, agreement was only achieved when T2* correction, spectral modeling of fat, and magnitude fi tting for eddy current correction were used ( r 2 = 0.99; slope 6 standard deviation = 1.00 6 0.01, P = .77; intercept 6 standard deviation = 0.2% 6 0.1, P = .19 ). Conclusion:T1-independent chemical shift-based water-fat separation MR imaging methods can accurately quantify fat over the entire liver, by using MR spectroscopy as the reference standard, when T2* correction, spectral modeling of fat, and eddy current correction methods are used.q RSNA, 2011

This work describes a methodology for quantifying levels of total choline-containing compounds (tCho) in the breast using in vivo 1 H MR spectroscopy (MRS) at high field (4 Tesla). Water is used as an internal reference compound to account for the partial volume of adipose tissue. Peak amplitudes are estimated by fitting one peak at a time over a narrow frequency band to allow measurement of small metabolite resonances in spectra with large lipid peaks. This quantitative method significantly improves previously reported analysis methods by accounting for the variable sensitivity of breast 1 H MRS measurements. Using this technique, we detected and quantified a tCho peak in 214 of 500 in vivo spectra. tCho levels were found to be significantly higher in malignancies than in benign abnormalities and normal breast tissues, which suggests that this technique could be used to diagnose suspicious lesions and monitor response to cancer treatments. Breast cancer is a very common disease, affecting 11% of American women and causing more than 40000 deaths each year (1). While breast cancer mortality is decreasing, the incidence continues to rise (2). Thus, there is a great need for noninvasive diagnostic tools for both screening and treatment monitoring. The conventional diagnostics-X-ray mammography, sonography, and physical examination-are limited in their sensitivity for detecting disease and their specificity for distinguishing between benign and malignant lesions. Magnetic resonance imaging (MRI) of the breast is being used increasingly because of its high sensitivity, but its reported specificity is widely variable (3).Researchers have recently begun to augment breast MRI studies with MR spectroscopy (MRS) to increase specificity. In vivo MRS can detect a resonance at 3.25 ppm that has contributions from several different compounds, including choline, phosphocholine, glycerophosphocholine, and taurine. High-resolution in vitro and ex vivo studies indicate that the levels of choline compounds increase with malignancy (4 -6). At the lower field strengths used for in vivo work (1.5-4 T), these multiple resonances cannot be spectrally resolved and thus appear as a single peak, termed total choline-containing compounds (tCho).Several studies conducted at 1.5 T have shown that in vivo MRS can be used to distinguish between benign and malignant tissues (7-11). These studies used the hypothesis that tCho is only detectable in malignancies. A pooled analysis of these five studies showed that this tCho detectability criterion can identify malignancies with an 83% sensitivity and 85% specificity (12). This qualitative approach is promising, but it is only applicable if the MRS measurement sensitivity is invariant. In similar studies performed at 4 T, the increased sensitivity allows detection of tCho in benign lesions and normal subjects. A more general approach is to quantify the tCho peak with the expectation that tCho levels are higher in malignancies than in benign lesions or normal tissues. Two groups have reported quanti...

These results suggest that the change in tCho concentration between baseline and 24 hours after the first dose of PST can serve as an indicator for predicting clinical response to doxorubicin-based chemotherapy in locally advanced breast cancer.