Imaging Prostate Cancer with SQUID-Detected Microtesla MRI

描述(申请人提供)：1.5Tesla及以上的常规磁共振成像(MRI)越来越多地用于癌症的检测、诊断和分期。然而，在前列腺癌的情况下，传统的MRI不能提供足够的特异性来检测前列腺癌。为了利用在低磁场下可获得的增强的T1(纵向弛豫时间)对比度，LBNL开发了一种新的MRI系统，该系统可以在微特斯拉磁场下获取与地球磁场相当的MR图像。在这项技术中，质子自旋在更高磁场中的预极化与使用超导量子干涉装置(SQUID)检测核磁共振信号相结合，以提高信噪比。体外前列腺标本的初步数据表明，前列腺癌和健康的前列腺组织之间的对比度显著增强。该项目的目标是评估这种新的磁共振成像方法在前列腺癌诊断和分期中的潜力。在一项关于体外前列腺标本的盲法研究中，我们将测量包含不同类型的良性前列腺组织和不同Gleason分级的肿瘤标本的图像的T1对比度，并将结果与在加州大学旧金山分校综合癌症中心进行的组织病理学结果进行比较。此外，我们将提高SQUID探测器的灵敏度，并增加目前成像系统中的偏振场大小，以评估未来活体成像系统可以实现的空间分辨率以及信噪比和对比度噪声比。为了实现这些目标，我们提出了以下具体目标：目标1.提高探测器的灵敏度。目的2.测定含肿瘤的体外前列腺组织和其他类型的前列腺组织图像的T1对比度，以确定检测前列腺癌的敏感性和特异性。目的3.设计制作一种适用于活体成像的偏振线圈。目的4.对三维(3D)前列腺模型进行成像，并将其分辨率与计算结果进行比较；在与体内成像对应的距离处对2D体外前列腺标本进行成像。只要这些实验证实了初步的测量，随后就可以构建用于前列腺癌体内研究的原型系统。该系统可能比传统的MRI系统更便宜、更开放，并可能对前列腺癌的诊断和分期产生重大影响。可能的应用包括：(I)在活检前对前列腺进行成像，以确定癌症的位置和范围。(Ii)更准确地标示肿瘤的位置，以指导活检。(3)连续成像，以确定治疗或积极监测期间肿瘤的进展情况。(4)就地监测局部治疗，例如在近距离放射治疗期间放置种子。 与公众健康相关：将开发一种磁共振成像(MRI)系统，以证明在极低磁场下成像前列腺癌的可行性。与传统的高场磁共振相比，这项技术在健康组织和癌症组织之间提供了更高的对比度，而且该系统限制更少，成本更低。临床应用有望包括在治疗过程中对肿瘤进行连续监测或主动监测，图像引导活检，以及监测局部治疗，如近距离放射治疗。

DESCRIPTION (provided by applicant): Conventional magnetic resonance imaging (MRI) at 1.5 tesla and above is used increasingly for the detection, diagnosis and staging of cancer. In the case of prostate cancer, however, conventional MRI does not provide sufficient specificity for detection of prostate tumors. To take advantage of the enhanced T1 (longitudinal relaxation time) contrast available at low magnetic fields, a novel MRI system has been developed at LBNL which acquires MR images at microtesla fields, comparable to the Earth's field. In this technique, prepolarization of the proton spins in a much higher magnetic field is combined with detection of the nuclear magnetic resonance signal using a Superconducting QUantum Interference Device (SQUID) to enhance the signal-to-noise ratio. Preliminary data on ex vivo prostate specimens indicate that there is significantly enhanced contrast between prostate tumors and healthy prostate tissue. The goal of the proposed project is to assess the potential of this novel MR imaging method for the diagnosis and staging of prostate cancer. In a blinded study on ex vivo prostate specimens we will determine the T1 contrast in images of specimens containing different types of benign prostate tissue and tumors with various Gleason grades and compare the results with those from histopathology performed at the UCSF Comprehensive Cancer Center. In addition, we will improve the sensitivity of the SQUID detector and increase the magnitude of the polarizing field in our current imaging system to assess the spatial resolution and the signal to noise and contrast to noise ratios achievable with a future in vivo imaging system. To attain these goals we propose the following specific aims: Aim 1. Upgrade the detector sensitivity. Aim 2. Determine T1 contrast in images of ex vivo prostate tissue containing tumors and other prostate tissue types to determine the sensitivity and specificity for detecting prostate cancer. Aim 3. Design and build a polarizing coil suitable for in vivo imaging. Aim 4. Image three-dimensional (3D) prostate phantoms and compare the resolution with results predicted by calculations; image 2D ex vivo prostate specimens at a distance corresponding to that for in vivo imaging. Provided these experiments confirm the preliminary measurements, a prototype system could subsequently be constructed for in vivo studies of prostate cancer. This system would potentially be less expensive and more open than conventional MRI systems, and could significantly impact the diagnosis and staging of prostate cancer. Possible applications include: (i) Imaging the prostate before a biopsy to determine the location and extent of the cancer. (ii) More accurate mapping of the location of tumors to guide biopsy. (iii) Serial imaging to determine the progression of tumors during treatment or active surveillance. (iv) In situ monitoring of focal therapies, such as placement of the seeds during brachytherapy. PUBLIC HEALTH RELEVANCE: A magnetic resonance imaging (MRI) system will be developed to demonstrate the feasibility of imaging prostate tumors in very low magnetic fields. This technique offers much higher contrast between healthy and cancerous tissue compared to conventional high-field MRI, and the system is both less confining and less expensive. Clinical applications are expected to include serial monitoring of tumors during treatment or active surveillance, image guided biopsy, and monitoring of focal therapies like brachytherapy.