MR IMAGING TECHNIQUES FOR INTERVENTIONAL APPLICATIONS

MR引导治疗对动态MRI方法有特定要求。 首先，可以连续地选择图像视场（FOV）。 由医生使用例如定点设备来改变方式。 第二，独立于成像平面的选择， 图像FOV本身可以物理地改变（例如，诸如活检 针进入）或化学地（例如，在激光或RF烧蚀期间，或者作为 注射造影剂团），因此改变了最终的MR 形象所有这些情况都需要动态MR成像方法。 动态MRI与标准MRI的不同之处在于， 通过连续更新或重新获取图像数据来获得图像。 我们实验室最近的研究集中在新的动态 用于对MR引导治疗中涉及的过程进行成像的自适应方法 这些问题发展得如此之快， 在空间和时间上使用当前的动态方法。动态 自适应方法被区分为其中图像数据 根据信息动态修改获取策略 在处理最近获取的图像之后获得。 我们的方法是建立在假设的基础上， 可以在不损失图像质量的情况下获得时间分辨率， 动态MRI，如果使用自适应方法来最小化图像中的冗余 编码和数据采集。正在研究的MRI方法， 我们的实验室，是有效的编码和采集方法。他们可以 可以在快速成像技术的背景下实现（例如，回声- 平面或快速梯度回波），其不利用数据中的冗余 采集 我们将重点实施和改进三个主要的动态MRI 方法： a.子波变换编码技术 B.奇异值分解编码技术 C.专门的傅立叶变换编码技术。 我们还将根据标准性能评估每种方法 标准（信噪比，空间和时间分辨率）。 最后，我们将研究选择性射频激发方法的物理学， MRI（每种成像方法的基础）和诊断实用性 使用标准ROC方法修改的新方法，以评估检测 以及表征图像序列中的时变信息。 该方法开发项目将对该计划产生影响， 提供更高的空间和时间分辨率，更快（动态） 扫描和量化空间相关信息， 其他四个项目的具体目标。

MR guided therapy has a specific requirement for dynamic MRI methods. First, the image field-of-view (FOV) may be selected in a continuously varying fashion by physician using, for example, a pointing device. Second, independent of the selection of the imaging plane, the objects in the image FOV may themselves be changing physically (e.g., as a biopsy needle enters) or chemically (e.g., during laser or rf ablation, or as a bolus of contrast agent is injected) therefore altering the resultant MR image. All of these circumstances require a dynamic MR imaging method. Dynamic MRI differs from standard MRI in that a sequence of time-ordered images is obtained by continually updating or reacquiring image data. Recent investigations of our laboratory have focused on new dynamically adaptive methods for imaging the processes involved in MR guided therapy that evolve so rapidly that they cannot be adequately resolved both spatially and temporally using current dynamic approaches. Dynamically adaptive methods are distinguished as those in which the image data acquisition strategy is modified dynamically depending on information obtained after processing the most recently acquired image(s). Our approach is founded on the hypothesis that significant improvement in temporal resolution, without loss of image quality, can be obtained in dynamic MRI if an adaptive method is used to minimize redundancy in image encoding and data acquisition. The MRI methods that are under study in our laboratory, are efficient encoding and acquisition methods. They can be implemented in the context of fast imaging techniques (e.g., echo- planar or fast gradient-echo), which do not exploit redundancy in data acquisition. We will focus on implementing and improving three main dynamic MRI approaches: a. Wavelet transform encoding techniques; b. SVD (Singular Value Decomposition) encoding techniques; c. Specialized Fourier transform encoding techniques. We will also evaluate each method in terms of standard performance criteria (signal-to-noise ratios, spatial and temporal resolution). Finally, we will study the physics of selective rf excitation methods for MRI (the basis of each of the imaging methods) and the diagnostic utility of new methods using standard ROC methods modified to assess the detection and characterization of time-varying information in series of images. This method development project will have an impact on the program by providing improved spatial and temporal resolution, faster (dynamic) scanning, and quantitation of spatially dependent information tailored to the specific goals of each of the other four projects.