Inside-Out Nonlinear Gradients to Improve Diffusion MRI

项目摘要/摘要 前列腺癌的终生风险是九分之一，它仍然是男性第二大癌症杀手。然而，许多人 低级别疾病的患者接受过早或过度的治疗，这可能导致数十年的 大小便失禁和勃起功能障碍。前列腺癌同时过度诊断和漏诊的一个原因 癌症是指目前的成像方法是不可靠的，这反过来又使活检变得不可靠。一种非侵入性 前列腺癌的最大需求之一是具有良好的敏感性和特异性的影像检查方法。 弥散加权磁共振成像(DWI)是最有前景的候选序列。然而，前列腺核磁共振检查显示 由于适当的扩散编码需要较长的回声时间，因此图像质量极低。 为了改善前列腺的弥散加权成像，我们在MRI硬件中引入了一个新的概念：一种附件，它的唯一目的是 就是向靶器官提供扩散编码。与包含体积的成像渐变不同 这种由内向外的扩散梯度是放置在大腿之间的一根魔杖，它是严格线性的 在前列腺产生强烈的非线性场。几何图形允许标准空间编码、标准 接收器放置，以及扫描仪之间的便携性。 对于前列腺成像，这种方法在感兴趣的区域实现了10倍强的梯度， 增加总体信噪比和对上皮/细胞体积的敏感性，这是恶性肿瘤的一个标志。这个 据预测，磁场强度的增加将使前列腺的弥散加权成像加倍，改善主动监测， 活检命中率和治疗监测。综合来看，关于(1)可实现硬件的初步数据 SPECS，(2)前列腺成像模拟，和(3)体模实验结果为 该项目的可行性以及它将对前列腺弥散加权成像产生的重大影响。 方法： AIM 1将安装并描述定制扩散梯度以显示前列腺病变模体的弥散加权成像 该方法与常规方法一致，但具有较高的重复性和可信噪比。 目的2将新方法应用于健康人前列腺，建立定位、PNS阈值、 提高了体内的图像质量(精确度、对比度、重复性和定性评级)。 AIM 3将对具有活检幼稚疑似病变的患者进行成像，这些病变将由多个 放射科医生对现实人群中的对比度、诊断置信度和读者群间的可变性进行量化。 目的：在根治性前列腺切除术患者中，将联合注册的术前活体MRI、体外MRI 切除前列腺和整体病理以显示ADC和真实Gleason评分之间的相关性。 总而言之，这些目标将为提高精确度、对比度、诊断信心、 以及用该硬件获得的弥散加权成像的临床有效性。

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.