EFPcount appears to provide functional information regarding changes in tumor angiogenesis due to neoadjuvant chemotherapy. Functional MR imaging of the breast may be useful in monitoring tumor response to neoadjuvant chemotherapy.

This study was undertaken to determine the best time during the menstrual cycle to perform dynamic breast magnetic resonance imaging (MRI). The contralateral "normal" breast of 50 premenopausal women (mean age 40.4 +/- 6.4 years, range 30--52 years) were enrolled in a protocol designed to correlate an ipsilateral suspicious breast lesion with pathology. The contralateral breast in each patient was examined with palpation and mammography prior to MRI on a 1.5 T scanner using gradient echo and dynamic contrast-enhanced echo-planar without and following gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) injection. Pre-contrast T1 relaxation times were measured before calculating extraction flow product (EFP) maps using a multicompartmental model. T1, EFP, and enhancement were measured in the control breast on four slices centered around the nipple and recorded as a function of the phases of the menstrual cycle. Lesions or areas with focal enhancement were excluded. Analysis of variance and Fisher's tests were performed. The cyclic changes in T1 relaxation time were not significant (p>0.2). EFP and enhancement varied significantly during the cycle (p<0.003 and p<0.004, respectively), with low values during the first half of the cycle and high values during the second half. The lowest values of EFP and enhancement (5.5+/-2.9 ml/100 g/min and 26+/-17%) were observed during the proliferative phase (days 3--7), and the highest values (17+/-10.2 ml/100 g/min and 104+/-28%) were observed during the secretory phase (days 21-27) (p<0.0006 and p<0.0008, respectively). Dynamic breast MRI should be performed during first half of the menstrual cycle (days 3--14) in order to minimize interpretative difficulties related to the uptake of gadolinium in normal breast tissue due to hormonal fluctuations during the menstrual cycle.

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