The main purpose of breast ¹H-MRS is to help distinguish benign from malignant tumors. Numerous reports have described the association of cancer with elevation of a broad spectral peak centered at approximately δ = 3.2 ppm. This peak is primarily derived from free choline, phosphocholine, and glycerophosphocholine and is commonly referred to as total choline (tCho). Several other compounds including taurine, glucose, phophoethanolamine, and myoinositol also make minor contributions to this resonance.
Although 2D and 3D CSI methods are possible, the overwhelming majority of published studies in breast cancer have utilized SVS techniques. Accurate sizing and placement of the voxel is critical, with special care needed to exclude both adipose tissues and cystic/necrotic regions. Although gadolinium contrast may reduce the size of the choline peak, it is still commonly used to identify small lesions and to define tumor margins before spectroscopy.
Prior to generating spectra, automated plus manual shimming to achieve water line widths of no greater than 20 (for 1.5T) and 30 Hz (for 3.0T) must be performed. A typical SVS protocol might be: SVS-PRESS, TR = 2000 ms, TE = 135 ms, and NEX = 128 using 1024 data points. Fat and water suppression is required using conventional CHESS (or more sophisticated MEGA) pulses. Intermediate to long TE values (i.e.,130-288 ms) are recommended to allow the signal from fat to decay and render the tCho peak more conspicuous.
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Commercial vendors offer optimized/streamlined protocols for breast MRS. GE calls theirs BREASE (BREAst Spectroscopy Examination), a single voxel technique using PRESS and TE averaging. Siemens refers to theirs as GRACE (GeneRalized breAst speCtroscopy Exam). GRACE allows for quantitative choline measurements using signal from tissue water as an internal calibration reference or from an external sample fixed to the inner surface of the breast coil itself.
Baltzer PAT, Dietzel M. Breast lesions: diagnosis by using proton MR spectroscopy at 1.5 and 3.0 T — Systematic review and meta-analysis. Radiology 2013; 267:735-746. (significant publication bias due to low numbers of patients in most series inflates sensitivity of breast MRS, though specificity remains high; no difference in field strength noted).
Begley JKP, Redpath TW, Bolan PJ, Gilbert FJ. In vivo proton magnetic resonance spectroscopy of breast cancer: a review of the literature. Breast Cancer Res 2012; 14:207.
Stanwell P, Mountford C. In vivo proton MR spectroscopy of the breast. Radiographics 2007; 27(Suppl 1):S253-266.
Tozaki M, Maruyama K. Current status and future prospects of proton MR spectroscopy of the breast with a 1.5T MR unit. J Oncol 2010; Article ID 781621:1-10.
Does gadolinium contrast affect MR spectral lines?