An example of the effusion regions of a knee. Effusion regions shown on T2-weighted images (A), peripheral enhancement of the contrast-enhanced MR images (B), and a schematic drawing of the effusion areas (C). The effusion region contained two separate areas which included fluid in the inner portions (dark arrow) and synovium at the periphery (white arrow).
A schematic drawing of the double inversion recovery sequence. The two inversion times are denoted as TI 1 and TI 2. τ is a constant value that is equal to half of the echo spacing. Imaging acquisition was performed with a turbo spin-echo acquisition mode (TSE Acq).
Results of the computer simulations to suppress signals from both water and fat based on T 1 relaxation times. The normalized values of the available magnetization Mz versus the T 1 values for the TI 1 and TI 2 values that are appropriate for nulling fluid, and fat signal with a given TR, TE, and τ are plotted in this figure.
DIR images with different double-inversion times obtained from a 28-year-old male patient without using a fat suppression pulse that demonstrate the improved effusion contrast. IMW is the intermediate density-weighted turbo spin-echo image without using a fat suppression pulse. DIR is the double inversion recovery images obtained with 254-2830 ms. The scan time was 2 min and 20 s for the DIR sequence.
Improved effusion contrast with the DIR sequence in images obtained from a 48-year-old female patient. The images were acquired with using a fat suppression pulse for two imaging sequences. IMW is the intermediate density-weighted turbo spin-echo image without using a fat suppression pulse. DIR is the double inversion recovery images obtained with 254-2830 ms. The scan time was 2 min and 20 s for the DIR sequence.
Comparisons of the DIR images with fat-saturated contrast-enhanced T1-weighted (CE T1W) images obtained from a 69-year-old female patient that demonstrate the usefulness of the DIR sequences for imaging the effusion areas. IMW is the intermediate density-weighted turbo spin-echo image. DIR images were obtained with TI 1 = 2830 ms and TI 2 = 254 ms. The enhanced areas from the CE T1W are overlaid onto the IMW and DIR images.
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