Breast cancer screening and interventions have been increasingly successful in early detection and reduction of mortality rates. Prevention, however, is the most desirable goal. Some of the least expensive prevention options, dietary modification and omega-3 supplementation, may have a practical role in reducing the rates of breast malignancies. The interaction between fat consumption, fat composition, and the risk of cancer has been examined extensively. However, many of the studies reach conflicting conclusions. For example, epidemiological studies demonstrate high correlation between total fat consumption and breast cancer mortality (1
). In addition to the amount of fat consumed, fat composition may also be a prognostic marker for tumorigenesis. Animal studies show that selected polyunsaturated fatty acids (PUFA) are associated with tumorigenesis (3
). Conversely, protective effects have been attributed to α-linolenic and docosahexaenoic (DHA) acids (5
), and ω-3 PUFA (6
). Considerations of the lipodome as a complex composite marker consisting of 23 fatty acids have shown that a lipid profile low in linoleic acid and high in cis
-monounsaturated fatty acids (MUFA) decreases the risks of breast cancer (7
). Numerous negative results however have also been reported, where no significant association of fatty acid composition and breast cancer was found (8
The discrepancies in some of the dietary intervention studies in humans may be due to limitations in the methodology used to evaluate dietary intake. Dietary records, dietary interviews, and food frequency questionnaires all suffer from subjectivity and unintentional under- or over-reporting. Since the chemical composition of adipose tissue reflects dietary fat over the preceding two years (11
), noninvasive analysis of breast fat composition should provide an accurate index of the long-term effects of diet.
While magnetic resonance spectroscopy (MRS) has been previously used for evaluation of the water-(total) fat (W-F) ratio, there is ambiguity in the utility of this marker since some studies report elevated W-F ratios in malignant breast tissues (12
), while others report no significant differences for benign and malignant breast lesions (14
). The interpretation of this marker is complicated by partial volume contamination due to voxel placement, as well as by changes in T2
of water rather than changes in the W-F ratios themselves (15
). Indeed, fat is mostly perceived to be a nuisance in proton MRS, with most of the spectroscopic studies focusing on the detection of total choline-containing metabolites (tCho), since elevated tCho is an indicator of increased cell proliferation (16
). Ex vivo
breast fat composition has been quantified by MRS using 13
) and while this method affords additional compositional information, as compared to proton MRS, it may be difficult to apply in vivo
due to the high power requirement for proton decoupling. In the only in vivo
MRS report on breast lipid composition, Dzendrowskyj et al. were able to measure changes in the allylic intensity throughout the menstrual cycle, but did not report on the PUFA/MUFA/saturated portions of the lipid (19
), presumably due to the lack of spectral resolution in separating signals from these lipid fractions. In the present study, spectral resolution was improved by going to high fields thus allowing for baseline-resolution of most of the lipid peaks at 7T.
High field breast MRS can be technically challenging, particularly due to the large lipid peak at 1.3 ppm that can generate frequency modulation sidebands due to mechanical gradient vibrations. Two main methods have been developed to reduce these sidebands, namely the gradient polarity inversion scheme (20
) and the TE-averaging scheme (21
). These methods were combined in this study to allow for virtual elimination of this artifact from the spectra. Further challenge in high field human spectroscopy, the frequency and phase shifts due to respiration, was addressed using respiratory triggering in acquisition and coherent averaging in postprocessing (22
Here, we report the use of high field proton MRS for non-invasive determination of lipid composition in female subjects. Normative values of PUFA, MUFA, and saturated fatty acids in the breast adipose tissue of ten healthy (without known breast disease) women are reported.