PET/MR for the multimodal diagnostics of myocardial perfusion: validation and synergies

缺血性心脏病是西方国家最常见的死亡原因。非侵入性诊断可以使用核医学技术进行，如单光子发射断层扫描（SPECT）或正电子发射断层扫描（PET）。动态对比增强心脏磁共振成像也允许诊断，并已证明了临床常规使用的高潜力。最近，定量灌注测量也引起了人们的极大兴趣。在核医学检查方面，MRI一方面得益于无电离辐射和明显更高的空间分辨率。另一方面，MRI仍然有一些主要的缺点，比如在每个rr区间内只有3到4个切片的解剖覆盖范围相当小，或者验证不理想。因此，在这个项目中，将开发新技术，允许对全心脏覆盖的第一次灌注进行高分辨率测量。该技术将使用集成PET/ mr系统进行验证。除了开发和验证工作，将探索同时获得的PET和MRI数据用于心肌组织表征的协同使用的潜力。新的成像技术旨在提供高分辨率的图像，覆盖整个心肌，并允许定量测定心肌灌注。为了实现全心脏覆盖，将采用同步多层成像（MS-CAIPIRINHA）。结合径向k空间轨迹，另外将开发一种成像方法，可以通过一次扫描估计血池和心肌内造影剂浓度的时间曲线。因此，灌注定量将不再需要从预注射技术中已知的第二次大剂量注射。在集成的PET/MR系统上实施，新开发的成像技术将得到验证，并利用同时获得的PET数据评估MS-CAIPIRINHA在准确心肌灌注定量方面的预期优势。在MR灌注成像中实现的完全解剖覆盖可以提高与定量PET检查结果的可比性。此外，还将研究径向k空间轨迹的使用在多大程度上系统地改善了造影剂量化。考虑到MRI造影剂和PET示踪剂分布动力学的差异，同时获得的PET/MR数据集有望提供一组关于组织功能的定量信息，这些信息超过了单个MRI或PET检查可获得的信息。因此，该项目的目标将是评估全心脏同时PET/MR检查在多参数心肌组织表征方面的协同潜力。

Ischemic heart disease is the most common cause of death in western countries. Non-invasively diagnosis can be performed using nuclear medicine techniques like Single Photon Emission Tomography (SPECT) or Positron Emission Tomography (PET). Dynamic contrast enhanced cardiac magnetic resonance imaging also allows for the diagnosis and has demonstrated a high potential for clinical routine use. Recently, also quantitative perfusion measurements gained a lot of interest. With respect to nuclear medicine examinations, MRI on the one hand benefits from the absence of ionizing radiation and the significantly higher spatial resolution. On the other hand MRI still suffers from some major disadvantages like the rather small anatomic coverage of only 3 to 4 slices within each RR-interval or the suboptimal validation.Consequently, in this project new techniques will be developed allowing for highly resolved measurements of the first pass perfusion with whole heart coverage. The techniques will be validated using an integrated PET/MR-system. Besides the development and validation works the potential of a synergetic usage of simultaneously acquired PET and MRI data for myocardial tissue characterization will be explored.The new imaging techniques are intended to provide highly resolved images, cover the whole myocardium and allow for the quantitative determination of the myocardial perfusion. In order to achieve whole heart coverage simultaneous multi-slice imaging (MS-CAIPIRINHA) will be utilized. Incorporating a radial k-space trajectory, additionally an imaging method will be developed that allows estimating the time curves of the contrast agent concentration within the blood pools and the myocardium from one single scan. A second bolus injection as known from the prebolus technique will thus be no longer required for perfusion quantification.Implemented on an integrated PET/MR system, the newly developed imaging techniques will be validated and the expected advantages of MS-CAIPIRINHA in terms of accurate myocardial perfusion quantification will be evaluated utilizing the simultaneously acquired PET data. The achieved full anatomical coverage in MR perfusion imaging allows an improved comparability with the results of the quantitative PET examination. Moreover, it will be investigated, to what extent the use of a radial k-space trajectory systematically improves the contrast agent quantification.Considering the difference in the distribution kinetics for the MRI contrast agent and the PET tracer, a simultaneously acquired PET/MR dataset is expected to deliver a combined set of quantitative information on tissue functionality that exceeds the information retrievable by individual MRI or PET examinations. A goal of this project thus will be to evaluate the synergetic potential of a simultaneous whole heart PET/MR examination regarding a multiparametric myocardial tissue characterization.