Inside-Out Nonlinear Gradients to Improve Diffusion MRI

项目总结/摘要 前列腺癌的终生风险是1/9，它仍然是男性的第二大癌症杀手。然而许多 低度疾病患者接受过早或过度治疗，这可能导致数十年的 失禁和勃起功能障碍。前列腺的过度诊断和诊断不足的原因之一 癌症的一个重要原因是目前的成像方法不可靠，这反过来又使活检不可靠。一种无创 前列腺癌最需要的是一种灵敏度高、特异性强的影像学检查方法 扩散加权MRI（DWI）是最有前途的候选者。然而，前列腺MRI 由于充分扩散编码所需的回波时间长，图像质量极低。 为了提高前列腺DWI的质量，我们在MRI硬件中引入了一个新的概念： 是向目标器官提供扩散编码。与体积包围的成像梯度不同， 和严格的线性，这种"由内而外"的扩散梯度是一个棒放在大腿之间， 在前列腺处产生强非线性场。几何形状允许标准空间编码、标准空间编码和标准空间编码。 接收器放置和扫描器之间的便携性。 对于前列腺成像，该方法实现了在感兴趣区域上> 10倍强的梯度， 增加了总体SNR和对上皮/细胞体积的敏感性，这是恶性肿瘤的标志。的 预计场强增加会使前列腺DWI中的对比度加倍，从而改善主动监视， 活检命中率和治疗监测。综上所述，关于（1）可实现硬件的初步数据 规格，（2）前列腺成像模拟，和（3）幻影实验结果为 该项目的可行性及其对前列腺DWI的重大影响。 方法： 目标1将安装并表征自定义扩散梯度，以在前列腺病变体模中演示DWI 该方法与常规方法一致，但具有更高的重现性和CNR。 目的2将新方法应用于健康对照者的前列腺以建立定位、PNS阈值， 准确性和改善的体内图像质量（精度、对比度、再现性和定性评级）。 Aim 3将对活检初治疑似病变患者进行成像，将通过多项指标进行概述和评分。 放射科医师在现实人群中量化对比度、诊断置信度和阅片师间变异性。 目的4将在根治性前列腺切除术患者中获得共配准的术前体内MRI、离体MRI和MRI。 切除的前列腺和整体病理学以显示ADC和真实Gleason评分之间的相关性。 总之，这些目标将提供强有力的证据，提高精度，对比度，诊断信心， 和临床有效性。

Project Summary/Abstract The lifetime risk of prostate cancer is 1 in 9 and it remains the 2nd leading cancer killer of men. Yet many patients with low grade disease receive premature or excessive treatment, which can lead to decades of incontinence and erectile dysfunction. One reason for the simultaneous over- and under- diagnosis of prostate cancer is that current imaging methods are unreliable, which in turn make biopsies unreliable. A noninvasive imaging method with good sensitivity and specificity is one of the greatest needs in prostate cancer management, and diffusion weighted MRI (DWI) is the most promising candidate. However, prostate MRI has extremely low image quality due to the long echo times needed for adequate diffusion encoding. To improve DWI of prostate, we introduce a new concept in MRI hardware: an accessory whose sole purpose is to provide diffusion encoding to a target organ. Unlike imaging gradients which are volume-encompassing and stringently linear, this “inside-out” diffusion gradient is a wand placed between the upper legs which creates strong nonlinear fields at the prostate. The geometry allows for standard spatial encoding, standard receiver placement, and portability between scanners. For prostate imaging, this approach achieves a gradient that is >10-fold stronger over the region of interest, increasing both overall SNR and sensitivity to epithelial/cellular volume, a hallmark of malignancy. The increase in field strength is predicted to double contrast in DWI of prostate, improving active surveillance, biopsy hit rates, and treatment monitoring. Taken together, the preliminary data on (1) achievable hardware specs, (2) prostate imaging simulations, and (3) phantom experimental results make a strong case for the feasibility of this project and the significant impact it will have on prostate DWI. Approach: Aim 1 will install and characterize a custom diffusion gradient to demonstrate DWI in a prostate lesion phantom which is consistent with conventional methods, but with higher reproducibility and CNR. Aim 2 applies the new method to prostate of healthy controls to establish positioning, PNS thresholds, accuracy, and improved image quality (precision, contrast, reproducibility and qualitative ratings) in vivo. Aim 3 will image patients with biopsy-naïve suspected lesions, which will be outlined and scored by multiple radiologists to quantify contrast, diagnostic confidence and inter-reader variability in a realistic population. Aim 4 will acquire, in radical prostatectomy patients, coregistered presurgical in vivo MRI, ex vivo MRI of the excised prostate, and whole-mount pathology to show correlation between ADC and true Gleason score. Together, these aims will provide strong evidence for the increased precision, contrast, diagnostic confidence, and clinical validity of DWI acquired with this hardware.