PURPOSE To report on an initial experience on breast MR spectroscopy (MRS) at 3T. The study was aimed at characterizing the feasibility of single-voxel choline detection at 3T in suspected malignant breast lesions. METHOD AND MATERIALS 22 patients (24 lesions, range 0.065-8.18cm3, mean 1.93cm3) were enrolled in the study (32-77yrs, mean 57yrs). All patients had suspicious findings on mammography or sonography of the breast, confirmed by cytology and/or micro-biopsy. Single-voxel MRS was performed by means of a Philips Achieva STx 3.0T scanner. Iterative shimming was restricted to the region of interest (ROI) used for spectroscopy (0.512-8.0 cm3, mean 1.097 cm3). The ROI was centred on the lesion, except in cases where a central necrotic area was observed. The spectroscopic sequence used TE=100ms, TR=2000ms, 128 samples, water (window 100Hz) and fat (SPAIR, window 80Hz) suppression. When possible, spectroscopy was performed before contrast agent injection and repeated thereafter. Pre-saturation was used to suppress signal from nearby regions. The local field homogeneity was evaluated by means of the FWHM of the unsuppressed water peak. A threshold was placed at 50Hz, above which spectroscopy was not performed due to insufficient field homogeneity. Total choline was estimated by means of the signal-to-noise ratio of the peak at 3.2ppm. RESULTS MRS was feasible in 54.2% of the lesions (13/24, water peak FWHM 15-44Hz, mean 29Hz). For the other 11 lesions the FWHM of the unsuppressed water peak exceeded 50Hz (57-103Hz, mean 70.3Hz). Of the 13 feasible, 10 lesions showed choline (SNR 3.2-16.6, mean 7.5) while 3 lesions showed no detectable choline. In 2 cases no choline was detected in the central, necrotic region while a clear signal was present at the periphery of the lesion (SNR 5.1-5.4). In 2 cases the cho signal was disrupted after contrast injection. CONCLUSION High-field MR spectroscopy is expected to improve the signal-to-noise ratio of the investigated metabolites (choline in this study), however field homogeneity is more difficult to achieve compared to 1.5T applications. The measured SNR confirmed the expected improvement, but further research is warranted to increase the fraction of cases for which high-field MRS is feasible. CLINICAL RELEVANCE/APPLICATION MRS at 3T could improve the specificity of breast MR, however the possible correlation between total choline concentration and malignancy needs further investigation.
MR Spectroscopy of the Breast at 3T: An Initial Clinical Experience
MONTEMEZZI, STEFANIA;BAGLIO, Ilaria;CENZI, Daniela;BARBAZENI, GIOVANNA;MELIADO', GABRIELE;CAVEDON, CARLO
2012-01-01
Abstract
PURPOSE To report on an initial experience on breast MR spectroscopy (MRS) at 3T. The study was aimed at characterizing the feasibility of single-voxel choline detection at 3T in suspected malignant breast lesions. METHOD AND MATERIALS 22 patients (24 lesions, range 0.065-8.18cm3, mean 1.93cm3) were enrolled in the study (32-77yrs, mean 57yrs). All patients had suspicious findings on mammography or sonography of the breast, confirmed by cytology and/or micro-biopsy. Single-voxel MRS was performed by means of a Philips Achieva STx 3.0T scanner. Iterative shimming was restricted to the region of interest (ROI) used for spectroscopy (0.512-8.0 cm3, mean 1.097 cm3). The ROI was centred on the lesion, except in cases where a central necrotic area was observed. The spectroscopic sequence used TE=100ms, TR=2000ms, 128 samples, water (window 100Hz) and fat (SPAIR, window 80Hz) suppression. When possible, spectroscopy was performed before contrast agent injection and repeated thereafter. Pre-saturation was used to suppress signal from nearby regions. The local field homogeneity was evaluated by means of the FWHM of the unsuppressed water peak. A threshold was placed at 50Hz, above which spectroscopy was not performed due to insufficient field homogeneity. Total choline was estimated by means of the signal-to-noise ratio of the peak at 3.2ppm. RESULTS MRS was feasible in 54.2% of the lesions (13/24, water peak FWHM 15-44Hz, mean 29Hz). For the other 11 lesions the FWHM of the unsuppressed water peak exceeded 50Hz (57-103Hz, mean 70.3Hz). Of the 13 feasible, 10 lesions showed choline (SNR 3.2-16.6, mean 7.5) while 3 lesions showed no detectable choline. In 2 cases no choline was detected in the central, necrotic region while a clear signal was present at the periphery of the lesion (SNR 5.1-5.4). In 2 cases the cho signal was disrupted after contrast injection. CONCLUSION High-field MR spectroscopy is expected to improve the signal-to-noise ratio of the investigated metabolites (choline in this study), however field homogeneity is more difficult to achieve compared to 1.5T applications. The measured SNR confirmed the expected improvement, but further research is warranted to increase the fraction of cases for which high-field MRS is feasible. CLINICAL RELEVANCE/APPLICATION MRS at 3T could improve the specificity of breast MR, however the possible correlation between total choline concentration and malignancy needs further investigation.
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