Percentage Signal Intensity Change Research Articles

Dynamic MR mammography: a technique for potentially reducing the biopsy rate for benign breast disease.

Thirty-five women with a total of 39 breast lesions detected at mammography and/or physical examination and who were scheduled for surgical biopsy were studied with dynamic magnetic resonance (MR) mammography. Fat-suppressed, spoiled GRASS (gradient-recalled acquisition in the steady state) sequences were performed before and after administration of gadopentetate dimeglumine. T1-weighted spin-echo and fat-suppressed T2-weighted fast spin-echo images were also obtained. By measuring percentage signal intensity change in lesions on the spoiled GRASS images after contrast agent injection, the authors achieved a sensitivity of 100% and a specificity of 83.3% in differentiating benign from malignant lesions (24 benign, 15 malignant), with biopsy results as the standard. This dynamic MR mammography technique deserves further evaluation.

Imaging of cerebral activation at 1.5 T: optimizing a technique for conventional hardware.

To empirically optimize a two-dimensional magnetic resonance (MR) imaging technique for detecting changes in signal intensity during cerebral activation with a standard clinical imager. Visual activation experiments were performed while imaging parameters were manipulated in a serial fashion, to test their effect on the percentage change in signal intensity (PCSI). The parameters tested were section thickness, echo time (TE), field of view (FOV), flip angle, radio-frequency (RF) spoiling, number of readout points, and number of signals averaged. The PCSI for visual activation experiments was typically in the 1%-5% range. The best results were achieved with a small section thickness, long TE, and large FOV. Variations in other acquisition parameters had a negligible influence on the PCSI. Good results can be obtained at functional MR imaging with standard 1.5-T hardware. Markedly improved results can be obtained by optimizing several key variables, namely, section thickness, TE, and FOV.