Magnetic resonance T(1) imaging of the breast using fat suppressed single scan technique.

Abstract

Previous in vitro studies suggest that T$\sb1$ is significantly elevated in malignant breast tissues compared to normal. As a result, quantitative T$\sb1$ imaging of the breast in vivo is considered potentially specific for breast cancer diagnosis. For various reasons, however, breast T$\sb1$ imaging studies to date have produced T$\sb1$ values with great dispersion including considerable overlap between normal and malignant groups. The T$\sb1$ measurements from these in vivo studies are, therefore, not specific for diagnostic purposes. In conjunction with other measures, T$\sb1$ may yet be a valuable indicator. But prior to further studies, the accuracy of in vivo techniques should be improved. In this dissertation, we focus on two major factors hypothesized to contribute to T$\sb1$ scatter determined from in vivo imaging. The first is the strong contamination from undesirable fat signals in conventional proton T$\sb1$ images of the breast. The second is the often non-optimal experimental design of the T$\sb1$ imaging technique employed in previous studies. We first simulate the effects of these two factors on T$\sb1$ measurements of target breast tissues. We then develop and evaluate a reliable T$\sb1$ imaging technique combining the features of fat suppression with single scan, multiple acquisition point T$\sb1$ imaging. We further explore the clinical utility of this technique with a number of in vivo experiments. A special purpose breast coil is constructed for T$\sb1$ imaging experiments. The B1 homogeneity of the volume enclosed by the coil is assessed. In vitro tests employing chemical samples with T$\sb1$ values determined using a conventional inversion recovery technique are conducted to evaluate the proposed fat suppressed T$\sb1$ imaging technique. Twenty normal volunteers are studied using the fat suppressed T$\sb1$ imaging technique to assess relaxation time dispersion in different breast regions. The T$\sb2$ values of these breast regions are also measured using conventional multiple echo, spin echo images. The work described here establishes a foundation for further research to estimate the distribution of relaxation times of various malignant breast tissues and thereafter to ultimately determine the diagnostic value of relaxation times in breast cancer detection.