Liu Xiaoyang, Karmarkar Parag, Voit Dirk, Frahm Jens, Weiss Clifford R, Kraitchman Dara L, Bottomley Paul A
Department of Electrical and Computer Engineering, Johns Hopkins University, USA.
The Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland, USA.
BME Front. 2021 Feb 17;2021:6185616. doi: 10.34133/2021/6185616. eCollection 2021.
. Atherosclerosis is a leading cause of mortality and morbidity. Optical endoscopy, ultrasound, and X-ray offer minimally invasive imaging assessments but have limited sensitivity for characterizing disease and therapeutic response. Magnetic resonance imaging (MRI) endoscopy is a newer idea employing tiny catheter-mounted detectors connected to the MRI scanner. It can see through vessel walls and provide soft-tissue sensitivity, but its slow imaging speed limits practical applications. Our goal is high-resolution MRI endoscopy with real-time imaging speeds comparable to existing modalities. . Intravascular (3 mm) transmit-receive MRI endoscopes were fabricated for highly undersampled radial-projection MRI in a clinical 3-tesla MRI scanner. Iterative nonlinear reconstruction was accelerated using graphics processor units connected via a single ethernet cable to achieve true real-time endoscopy visualization at the scanner. MRI endoscopy was performed at 6-10 frames/sec and 200-300 m resolution in human arterial specimens and porcine vessels and and compared with fully sampled 0.3 frames/sec and three-dimensional reference scans using mutual information (MI) and structural similarity (3-SSIM) indices. . High-speed MRI endoscopy at 6-10 frames/sec was consistent with fully sampled MRI endoscopy and histology, with feasibility demonstrated in a large animal model. A 20-30-fold speed-up vs. 0.3 frames/sec reference scans came at a cost of ~7% in MI and ~45% in 3-SSIM, with reduced motion sensitivity. . High-resolution MRI endoscopy can now be performed at frame rates comparable to those of X-ray and optical endoscopy and could provide an alternative to existing modalities, with MRI's advantages of soft-tissue sensitivity and lack of ionizing radiation.
动脉粥样硬化是导致死亡和发病的主要原因。光学内镜检查、超声检查和X射线检查提供了微创成像评估，但在疾病特征和治疗反应的表征方面敏感性有限。磁共振成像（MRI）内镜检查是一种较新的概念，它采用连接到MRI扫描仪的微小导管安装探测器。它可以穿透血管壁并提供软组织敏感性，但其成像速度慢限制了实际应用。我们的目标是实现高分辨率MRI内镜检查，其实时成像速度可与现有模式相媲美。
为在临床3特斯拉MRI扫描仪中进行高度欠采样的径向投影MRI，制造了血管内（3毫米）发射-接收MRI内镜。使用通过单根以太网电缆连接的图形处理器单元加速迭代非线性重建，以在扫描仪处实现真正的实时内镜可视化。在人体动脉标本和猪血管中以6-10帧/秒和200-300微米分辨率进行MRI内镜检查，并使用互信息（MI）和结构相似性（3-SSIM）指数与完全采样的0.3帧/秒和三维参考扫描进行比较。
6-10帧/秒的高速MRI内镜检查与完全采样的MRI内镜检查和组织学结果一致，在大型动物模型中证明了其可行性。与0.3帧/秒的参考扫描相比，速度提高了20-30倍，但MI损失约7%，3-SSIM损失约45%，运动敏感性降低。
现在可以以与X射线和光学内镜检查相当的帧率进行高分辨率MRI内镜检查，并且可以提供现有模式的替代方案，具有MRI软组织敏感性和无电离辐射的优点。
