P-31 METABOLISM OF HUMAN BREAST - AN IN-VIVO MAGNETIC-RESONANCE SPECTROSCOPIC STUDY AT 1.5 TESLA

We have studied the metabolism of compounds containing P-31 in normal breast using magnetic resonance spectroscopy (MRS). Spectra were acqui red from non-lactating pre-menopausal breast (n = 14 women), lactating breast (n = 8) and post-menopausal breast (n = 8). The standard acqui sition protocol used a 5.5 cm surface coil with the volunteer prone to minimize chest wall signal contamination. In pre-menopausal nonlactat ing women the phosphocreatine (PCr) peak area, expressed relative to t he sum of all P-31 peak areas, was negatively correlated with breast s ize (r = -0.56, p = 0.02) suggesting that much of the PCr signal origi nated from the chest wall. The phosphodiester (PDE) relative peak area was positively correlated with breast size (r = 0.71; p = 0.002). Spe ctra could be acquired at all phases of the menstrual cycle. In sequen tial examinations of five women not taking the oral contraceptive pill (OCP), phosphomonoester (PME) relative peak area was significantly lo wer on Week 2 than other weeks of the cycle (p = 0.03). Among pre-meno pausal women no clear difference was apparent between the spectra from women taking the OCP and those not taking the OCP. Lactating breast h ad significantly higher PME relative peak area than non-lactating prem enopausal breast (p = 0.02), probably reflecting the higher proportion of epithelial tissue in lactation; the lower PCr relative peak area i n lactating breast (p = 0.05) is probably due to the greater size of t he breast during lactation. Spectra were acquired from post-menopausal women but with a relatively low signal-to-noise ratio. The only signi ficant difference between P-31 relative peak areas of breast spectra a cquired from pre- and post-menopausal women was that less PCr was dete cted in the post-menopausal volunteers (p = 0.03), probably as a resul t of differences in breast size.