Investigation of Diagnostic Improvement Gained Through Optimization of MR Methods for Breast Cancer Detection

MR examinations will be performed on a 3.0 Tesla GE whole-body scanner using an elliptically driven body coil for transmit and a multi-channel bilateral breast coil for receive. The multi-channel coil will consist of 8, 16 or 31 channels. DCE-MRI: DCE-MRI will be carried out using a three-dimensional (3D) turbo fast lowangle gradient echo sequence (TFE) combined with parallel acquisition Sensitivity Encoding (SENSE) technique. The imaging plane will be set in axial plane so that both breasts are included in the images. One image will be acquired before and four images will be acquired after intravenous administration of a standard dose of 0.1 mmol per kg of body weight of Gadavist (Schering AG, Germany) at a rate of 3ml/sec. with subjects in the prone position, breathing normally during the scan. The total scan time for the DCEMRI will be about 8 minutes.

Pharmacokinetic parameters, including the volume transfer constant Ktrans, the fractional volume of extravascular extracellular space of the target tissue ve, and the rate constant kep, will be estimated by fitting a pharmacokinetic model to the time-intensity curves obtained from the DCE-MRI. In this study, the concentration of tracer Ct(t) after bolus injection is assumed to obey the model proposed by Tofts and Kermode (20). DWI-MRI examinations: The DWI acquisition will occur before and/or after contrast enhancement used in DCE imaging. Immediately after the completion of imaging with the 16 (or 31) channel breast coil, the patient will be repositioned replacing the breast coil with an 8 channel breast coil and additional DWI acquisitions will be made. Data for apparent diffusion coefficient assessment on diffusion-weighted imaging will be acquired using a single-shot Echo Planar Imaging sequence in the transverse plane. The DWI protocol will acquire images with up to 16 different b values. Slice dependent shimming will be performed to provide the maximum B0 homogeneity for each slice. The total scan time for the DWI-MRI will be about 5 minutes.

All of the DWI image data from the MRI examinations will be stored on a dedicated HIPPA compliant computer workstation (located in room NE6.114) for analysis. The relevant parameters will be mean ADC and the histogram of ADC in the lesions.

Conductivity imaging: A B1 map and a spin echo image will be acquired for measuring tissue conductivity (21).

The images used for conductivity measurement will be anonymized and sent to the manufacturer for further development of post-processing techniques.