Department of Spinal Surgery, University Hospital of North Tees, Hardwick, Stockton.
Spine (Phila Pa 1976). 2010 Jan 15;35(2):252-6. doi: 10.1097/BRS.0b013e3181c838cc.
Technical report.
To minimize the gross artefact associated with a conventional metallic lumbar total disc arthroplasty (TDA) device on a conventional high field-strength (1.5 Tesla [T]) magnetic resonance imaging (MRI) scanner.
Gross artefact is often apparent with ferromagnetic metallic TDA devices on conventional high field-strength MRI scanners. Such artefact completely obliterates MRI assessment at the operated level, and usually obscures visualization of adjacent segments. Because adjacent segment preservation is a raison d'être of spinal TDA, clarity of imaging at this latter level is imperative. A failure to image adjacent segments may presage investigations, which are either invasive (e.g., myelography) or associated with significant radiation hazard (e.g., computed tomography), both with significantly less diagnostic sensitivity. This could negatively direct TDA choice with certain TDAs.
Progressive modifications to specific imaging parameter settings were sought on a conventional high field-strength (1.5T) closed-bore scanner to match the minimal artefact previously observed on a lower field-strength (0.3T) open scanner. Direct comparisons were made between each modified protocol image obtained initially using a phantom; however, routine postoperative MRIs were subsequently obtained in n = 40 patients following lumbar TDA insertion.
Key parameter modifications were required in the receive bandwidth, the strength of the frequency encoding gradient, as well as in the echo train length. The use of higher specification "focused gradients" was also avoided. The overall effect was to reduce the slew rate of the gradients, which limited artefact due to a decrease in phase dispersion. Such appearances effectively matched with those previously obtained on the low field-strength (0.3T) open scanner in n = 40 patients.
Relatively simple modifications to MRI parameter settings can be made on conventional high field-strength (1.5T) closed-bore scanners, which minimize metal artefact and enhance imaging of adjacent segments with ferromagnetic TDA devices. Such modifications effectively match appearances to those obtained with outmoded low field-strength (0.3T) open-bore scanners.
技术报告。
最大限度地减少传统高场强（1.5 特斯拉[T]）磁共振成像（MRI）扫描仪上常规金属腰椎全椎间盘置换（TDA）装置的总伪影。
在传统高场强 MRI 扫描仪上，铁磁性金属 TDA 装置通常会出现明显的总伪影。这种伪影完全掩盖了手术部位的 MRI 评估，通常还会遮挡相邻节段的可视化。由于相邻节段的保留是脊柱 TDA 的存在理由，因此后者水平的成像清晰度至关重要。如果无法对相邻节段进行成像，可能预示着需要进行侵入性检查（例如脊髓造影）或与显著辐射危害相关的检查（例如计算机断层扫描），这两种检查的诊断敏感性都明显较低。这可能会对某些 TDA 的选择产生负面影响。
在传统高场强（1.5T）闭孔扫描仪上寻求特定成像参数设置的逐步修改，以匹配之前在低场强（0.3T）开孔扫描仪上观察到的最小伪影。最初在体模上进行了每个修改协议图像的直接比较；然而，随后在 n = 40 例腰椎 TDA 插入术后患者中获得了常规术后 MRI。
需要对接收带宽、频率编码梯度的强度以及回波链长度进行关键参数修改。还避免使用更高规格的“聚焦梯度”。总体效果是降低梯度的上升速率，从而通过减少相位弥散来减少伪影。这种外观与 n = 40 例患者在低场强（0.3T）开孔扫描仪上之前获得的外观有效匹配。
在传统高场强（1.5T）闭孔扫描仪上，可以对 MRI 参数设置进行相对简单的修改，最大限度地减少铁磁性 TDA 装置的金属伪影并增强相邻节段的成像。这些修改有效地使外观与使用过时的低场强（0.3T）开孔扫描仪获得的外观相匹配。
