Posluns Centre for Image Guided Innovation and Therapeutic Intervention, Hospital for Sick Children, Toronto, Ontario, Canada.
The Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
Med Phys. 2022 Apr;49(4):2120-2135. doi: 10.1002/mp.15540. Epub 2022 Mar 1.
Intraventricular hemorrhage (IVH) is one of the most serious neurovascular complications resulting from premature birth. It can result in clotting of blood within the ventricles, which causes a buildup of cerebrospinal fluid that can lead to posthemorrhagic ventricular dilation and posthemorrhagic hydrocephalus. Currently, there are no direct treatments for these blood clots as the standard of care is invasive surgery to insert a shunt. Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) has been investigated as a noninvasive treatment to lyse blood clots. However, current MRgHIFU systems are not suitable in the context of treating IVH in neonates.
We have developed a robotic MRgHIFU neurosurgical platform designed to treat the neonatal brain. This platform facilitates ergonomic patient positioning and directs treatment through their open anterior fontanelle while providing a larger treatment volume. The platform is based on an MR-compatible robot developed by our group. Further development of the platform has warranted investigation of its targeting ability to assess its feasibility in the neonatal brain. This study aimed to quantify the platform's targeting accuracy, precision, and repeatability using a brain phantom and clinical MRI system.
A thermosensitive brain-mimicking phantom was developed to test the platform's targeting accuracy. Rectangular grid patterns were created with HIFU thermal energy "lesions" in the phantoms by targeting specific coordinate points. The intended target locations were demarcated by inserting carbon fiber rods through a targeting assessment template. Coordinates for the intended and actual targets were derived from T2-weighted MRI scans, and the centroid distance between them was measured. Subsequently, the platform's targeting accuracy was quantified according to equations derived from ISO Standard 9283:1998.
HIFU ablation resulted in distinct thermal lesions within the thermosensitive phantoms, which appeared as discrete hypointense regions in T2-weighted MR scans. A total of 127 target points were included in the data analysis, which yielded a targeting accuracy of 0.6 mm and targeting precision of 1.2 mm.
The robotic MRgHIFU platform was shown to have a high degree of accuracy, precision, and repeatability. The results demonstrate the platform's functionality when targeting through simulated brain matter. These results serve as an initial verification of the platform targeting ability and showed promise toward the final application in a neonatal brain.
脑室内出血（IVH）是早产儿最严重的神经血管并发症之一。它会导致血液在脑室中凝结，从而导致脑脊液积聚，进而导致出血后脑室扩张和出血后脑积水。目前，由于标准的治疗方法是通过插入分流器进行有创手术，因此对于这些血块没有直接的治疗方法。磁共振引导高强度聚焦超声（MRgHIFU）已被研究为一种非侵入性治疗方法来溶解血块。然而，目前的 MRgHIFU 系统在治疗新生儿 IVH 方面并不适用。
我们开发了一种机器人磁共振引导高强度聚焦超声神经外科平台，旨在治疗新生儿的大脑。该平台便于患者进行符合人体工程学的定位，并通过他们的开放前囟门引导治疗，同时提供更大的治疗体积。该平台基于我们小组开发的一种与磁共振兼容的机器人。为了进一步开发该平台，我们需要研究其靶向能力，以评估其在新生儿大脑中的可行性。本研究旨在使用脑模型和临床磁共振成像系统来量化该平台的靶向准确性、精度和可重复性。
我们开发了一种热敏脑模拟模型来测试该平台的靶向准确性。通过在模型中的特定坐标点上使用 HIFU 热能“损伤”来创建矩形网格图案。通过插入碳纤维棒穿过靶向评估模板来标记目标位置。从 T2 加权磁共振扫描中得出目标和实际目标的坐标，然后测量它们之间的质心距离。随后，根据 ISO 标准 9283:1998 中的公式来量化平台的靶向准确性。
HIFU 消融导致热敏模型中的热损伤明显，在 T2 加权磁共振扫描中表现为离散的低信号区域。共有 127 个目标点纳入数据分析，靶向准确性为 0.6 毫米，靶向精度为 1.2 毫米。
机器人磁共振引导高强度聚焦超声平台具有很高的准确性、精度和可重复性。结果表明，该平台在模拟脑内靶向时具有良好的功能。这些结果是对该平台靶向能力的初步验证，并为最终在新生儿脑内应用提供了希望。
