| Summary: | Dynamic contrast-enhanced MRI (DCE-MRI) has proven to be a valuable tool in the detection, diagnosis and management of breast cancer. Signal intensity time-course data of lesions from the DCE-MRI sequence aid radiologists in diagnosing breast cancer. Semi-quantitative and quantitative analyses are the detailed modeling and measurements of lesion kinetic parameters from signal enhancement and concentration of contrast media time-course data, respectively.
Estimates of concentration with the standard clinical DCE-MRI protocol are very sensitive to measurements of the native T1 of lesions, and accurate knowledge of the actual flip angle at a given location (B 1). A method for the acquisition of B1 and T1 maps in the breast, based on a reference tissue method, was developed. This method relies on the homogeneous T1 of fat in the breast, and was shown to increase the accuracy of acquired T1 maps with respect to 'gold standards'.
Identification of lesion kinetic parameters that are insensitive to scanner properties is important for the wider applicability of quantitative methods. Patients were scanned at both 1.5T and 3T keeping other acquisition parameters similar between scans. Semi-quantitative measurements of overall curve shape were the most reproducible. Conversion from signal enhancement to concentration did not reduce variability between field strengths. With the acquisition parameters used, application of quantitative methods is troublesome as even small errors in T1 and B1 can lead to significant biases in estimated concentration.
A protocol was developed to sample early kinetics at a faster rate. Malignant and benign lesions showed significant differences in early kinetics. Fast DCE allowed the study of lesion kinetics with respect to time of arterial enhancement in the breast, and not time of injection, reducing dependence on global variables such as cardiac output. Lesion conspicuity was greatest at early time-points, and greater than with the standard protocol. Accelerated acquisitions during the first minute after contrast injection have diagnostic potential in clinical image interpretation and quantitative analysis.
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