Jungmann Pia M, Ganter Carl, Schaeffeler Christoph J, Bauer Jan S, Baum Thomas, Meier Reinhard, Nittka Mathias, Pohlig Florian, Rechl Hans, von Eisenhart-Rothe Ruediger, Rummeny Ernst J, Woertler Klaus
Department of Radiology, Klinikum rechts der Isar, Technische Universitaet Muenchen, Ismaninger Strasse 22, 81675, Munich, Germany.
Department of Radiology, Klinikum rechts der Isar, Technische Universitaet Muenchen, Ismaninger Strasse 22, 81675, Munich, Germany; Musculoskeletal Imaging, Kantonsspital Graubuenden, Loestrasse 170, CH-7000, Chur, Switzerland.
PLoS One. 2015 Apr 24;10(4):e0124922. doi: 10.1371/journal.pone.0124922. eCollection 2015.
MRI plays a major role in follow-up of patients with malignant bone tumors. However, after limb salvage surgery, orthopaedic tumor endoprostheses might cause significant metal-induced susceptibility artifacts.
To evaluate the benefit of view-angle tilting (VAT) and slice-encoding metal artifact correction (SEMAC) for MRI of large-sized orthopaedic tumor endoprostheses in an experimental model and to demonstrate clinical benefits for assessment of periprosthetic soft tissue abnormalities.
In an experimental setting, tumor endoprostheses (n=4) were scanned at 1.5T with three versions of optimized high-bandwidth turbo-spin-echo pulse sequences: (i) standard, (ii) VAT and (iii) combined VAT and SEMAC (VAT&SEMAC). Pulse sequences included coronal short-tau-inversion-recovery (STIR), coronal T1-weighted (w), transverse T1-w and T2-w TSE sequences. For clinical evaluation, VAT&SEMAC was compared to conventional metal artifact-reducing MR sequences (conventional MR) in n=25 patients with metal implants and clinical suspicion of tumor recurrence or infection. Diameters of artifacts were measured quantitatively. Qualitative parameters were assessed on a five-point scale (1=best, 5=worst): "image distortion", "artificial signal changes at the edges" and "diagnostic confidence". Imaging findings were correlated with pathology. T-tests and Wilcoxon-signed rank tests were used for statistical analyses.
The true size of the prostheses was overestimated on MRI (P<0.05). A significant reduction of artifacts was achieved by VAT (P<0.001) and VAT&SEMAC (P=0.003) compared to the standard group. Quantitative scores improved in the VAT and VAT&SEMAC group (P<0.05). On clinical MR images, artifact diameters were significantly reduced in the VAT&SEMAC-group as compared with the conventional-group (P<0.001). Distortion and artificial signal changes were reduced and diagnostic confidence improved (P<0.05). In two cases, tumor-recurrence, in ten cases infection and in thirteen cases other pathologies were diagnosed.
Significant reduction of metallic artifacts was achieved by VAT and SEMAC. Clinical results suggest, that these new techniques will be beneficial for detecting periprosthetic pathologies during postoperative follow-up.
磁共振成像（MRI）在恶性骨肿瘤患者的随访中发挥着重要作用。然而，保肢手术后，骨科肿瘤假体可能会引起明显的金属诱导敏感性伪影。
在实验模型中评估视角倾斜（VAT）和切片编码金属伪影校正（SEMAC）对大型骨科肿瘤假体MRI的益处，并证明其对评估假体周围软组织异常的临床益处。
在实验环境中，使用三种优化的高带宽涡轮自旋回波脉冲序列在1.5T下扫描肿瘤假体（n = 4）：（i）标准序列，（ii）VAT序列，（iii）VAT与SEMAC联合序列（VAT&SEMAC）。脉冲序列包括冠状面短反转时间反转恢复（STIR）序列、冠状面T1加权（w）序列、横断面T1加权和T2加权快速自旋回波（TSE）序列。为了进行临床评估，将VAT&SEMAC与n = 25例有金属植入物且临床怀疑肿瘤复发或感染的患者的传统金属伪影减少MR序列（传统MR）进行比较。定量测量伪影直径。定性参数采用五点量表进行评估（1 = 最佳，5 = 最差）：“图像失真”、“边缘人工信号变化”和“诊断置信度”。影像学表现与病理结果相关。采用t检验和Wilcoxon符号秩检验进行统计分析。
MRI高估了假体的实际尺寸（P < 0.05）。与标准组相比，VAT（P < 0.001）和VAT&SEMAC（P = 0.003）显著减少了伪影。VAT组和VAT&SEMAC组的定量评分有所改善（P < 0.05）。在临床MR图像上，VAT&SEMAC组的伪影直径与传统组相比显著减小（P < 0.001）。失真和人工信号变化减少，诊断置信度提高（P < 0.05）。诊断出2例肿瘤复发、10例感染和13例其他病变。
VAT和SEMAC显著减少了金属伪影。临床结果表明，这些新技术将有助于在术后随访中检测假体周围病变。
