Estimation of the content of fat and parenchyma in breast tissue using MRI T1 histograms and phantoms.

Mammographic breast density has been correlated with breast cancer risk. Estimation of the volumetric composition of breast tissue using three-dimensional MRI has been proposed, but accuracy depends upon the estimation methods employed. The use of segmentation based on T1 relaxation rates allows quantitative estimates of fat and parenchyma volume, but is limited by partial volume effects. An investigation employing phantom breast tissue composed of various combinations of chicken breast (to represent parenchyma) and cooking fats was carried out to elucidate the factors that influence MRI T1 histograms. Using the phantoms, T1 histograms and their known fat and parenchyma composition, a logistic distribution function was derived to describe the apportioning of the T1 histogram to fat and parenchyma. This function and T1 histograms were then used to predict the fat and parenchyma content of breasts from 14 women. Using this method, the composition of the breast tissue in the study population was as follows: fat 69.9+/-22.9% and parenchyma 30.1+/-22.9%.

Optimal post-contrast timing of breast MR image acquisition for architectural feature analysis.

PURPOSE: To define a post-contrast imaging time span during which diagnostic accuracy of breast magnetic resonance (MR) architectural feature analysis is maintained. MATERIALS AND METHODS: Seventy-five patients with mammographically-visible or palpable findings underwent MR examination. Three sequential post-contrast, fat-saturated, three-dimensional gradient-echo imaging runs were acquired spanning 0-90, 90-180, and 180-270 seconds after contrast injection. Five readers independently predicted the malignant potential of the MR abnormalities. RESULTS: Receiver-operator characteristics (ROC) curves were our primary measure of diagnostic accuracy. The accuracy of four readers was unchanged over the three post-contrast runs. One reader was slightly more accurate using the second and third runs than using the first. CONCLUSION: For most readers, a single post-contrast run performed at any point during the first four minutes and 30 seconds following injection should yield an equivalent diagnostic accuracy. If any time period is less optimal, it is that of our first run, performed between 0-90 seconds after contrast injection.