Feasibility of diffusion weighting with a local inside-out nonlinear gradient coil for prostate MRI.
Feasibility of diffusion weighting with a local inside-out nonlinear gradient coil for prostate MRI.
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前列腺癌仍然是男性第二大癌症杀手，但它也是一种过度治疗率很高的疾病。弥散加权成像(DWI)是一种可靠的、对级别敏感的成像方法，但其成像质量较低。目前，DWI图像质量与低梯度幅度直接相关，因为必须用长回波时间来补偿弱梯度。我们提出了一种新型的MRI附件，一种由内而外的非线性梯度，其唯一目的是将扩散编码传递到感兴趣的区域。在OPERA中进行了性能模拟，所得到的场被用来模拟具有两个隔室和峰度模型的DWI。利用非线性磁头梯度的实验证明了用非线性梯度进行扩散编码的DWI和ADC映射的准确性。模拟验证了热和机械安全，同时显示梯度强度比前列腺增加了5到10倍。有了这些优势，ADC图上的病变CNR在一系列解剖位置上几乎翻了一番。原理验证实验表明，空间变化的b值可以进行校正，以获得准确的DWI和ADC。专用的非线性扩散编码硬件可以改善前列腺的弥散加权成像。
Prostate cancer remains the 2nd leading cancer killer of men, yet it is also a disease with a high rate of overtreatment. Diffusion weighted imaging (DWI) has shown promise as a reliable, grade-sensitive imaging method, but it is limited by low image quality. Currently, DWI image quality is directly related to low gradient amplitudes, since weak gradients must be compensated with long echo times. We propose a new type of MRI accessory, an “inside-out” and nonlinear gradient, whose sole purpose is to deliver diffusion encoding to a region of interest. Performance was simulated in OPERA and the resulting fields were used to simulate DWI with two compartment and kurtosis models. Experiments with a nonlinear head gradient prove the accuracy of DWI and ADC maps diffusion encoded with nonlinear gradients. Simulations validated thermal and mechanical safety while showing a 5 to 10-fold increase in gradient strength over prostate. With these strengths, lesion CNR in ADC maps approximately doubled for a range of anatomical positions. Proof-of-principle experiments show that spatially varying b-values can be corrected for accurate DWI and ADC. Dedicated nonlinear diffusion encoding hardware could improve prostate DWI.