成像体模
脉冲序列
磁共振成像
扫描仪
序列(生物学)
比吸收率
核磁共振
关节软骨
材料科学
翻转角度
生物医学工程
核医学
物理
计算机科学
医学
骨关节炎
光学
放射科
化学
替代医学
病理
电信
生物化学
天线(收音机)
作者
Arijitt Borthakur,Andrew J. Wheaton,Sridhar R. Charagundla,Erik M. Shapiro,Ravinder R. Regatte,Sarma V.S. Akella,J. Bruce Kneeland,Ravinder Reddy
摘要
To design and implement a magnetic resonance imaging (MRI) pulse sequence capable of performing three-dimensional T(1rho)-weighted MRI on a 1.5-T clinical scanner, and determine the optimal sequence parameters, both theoretically and experimentally, so that the energy deposition by the radiofrequency pulses in the sequence, measured as the specific absorption rate (SAR), does not exceed safety guidelines for imaging human subjects.A three-pulse cluster was pre-encoded to a three-dimensional gradient-echo imaging sequence to create a three-dimensional, T(1rho)-weighted MRI pulse sequence. Imaging experiments were performed on a GE clinical scanner with a custom-built knee-coil. We validated the performance of this sequence by imaging articular cartilage of a bovine patella and comparing T(1rho) values measured by this sequence to those obtained with a previously tested two-dimensional imaging sequence. Using a previously developed model for SAR calculation, the imaging parameters were adjusted such that the energy deposition by the radiofrequency pulses in the sequence did not exceed safety guidelines for imaging human subjects. The actual temperature increase due to the sequence was measured in a phantom by a MRI-based temperature mapping technique. Following these experiments, the performance of this sequence was demonstrated in vivo by obtaining T(1rho)-weighted images of the knee joint of a healthy individual.Calculated T(1rho) of articular cartilage in the specimen was similar for both and three-dimensional and two-dimensional methods (84 +/- 2 msec and 80 +/- 3 msec, respectively). The temperature increase in the phantom resulting from the sequence was 0.015 degrees C, which is well below the established safety guidelines. Images of the human knee joint in vivo demonstrate a clear delineation of cartilage from surrounding tissues.We developed and implemented a three-dimensional T(1rho)-weighted pulse sequence on a 1.5-T clinical scanner.
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