Clementi Valeria, Zanovello Umberto, Arduino Alessandro, Ancarani Cristina, Baruffaldi Fabio, Bordini Barbara, Chiampi Mario, Zilberti Luca, Bottauscio Oriano
IRCCS Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica, Via di Barbiano 1/10, 40136 Bologna, Italy.
Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy.
Diagnostics (Basel). 2022 Aug 2;12(8):1873. doi: 10.3390/diagnostics12081873.
Due to the large variety of possible clinical scenarios, a reliable heating-risk assessment is not straightforward when patients with arthroplasty undergo MRI scans. This paper proposes a simple procedure to estimate the thermal effects induced in patients with hip, knee, or shoulder arthroplasty during MRI exams. The most representative clinical scenarios were identified by a preliminary frequency analysis, based on clinical service databases, collecting MRI exams of 11,658 implant carrier patients. The thermal effects produced by radiofrequency and switching gradient fields were investigated through 588 numerical simulations performed on an ASTM-like phantom, considering four prostheses, two static field values, seven MR sequences, and seven regions of imaging. The risk assessment was inspired by standards for radiofrequency fields and by scientific studies for gradient fields. Three risk tiers were defined for the radiofrequency, in terms of whole-body and local SAR averages, and for GC fields, in terms of temperature elevation. Only 50 out of 588 scenarios require some caution to be managed. Results showed that the whole-body SAR is not a self-reliant safety parameter for patients with metallic implants. The proposed numerical procedure can be easily extended to any other scenario, including the use of detailed anatomical models.
由于可能出现的临床情况多种多样，对于接受关节置换术的患者进行MRI扫描时，可靠的加热风险评估并非易事。本文提出了一种简单的程序，用于估计髋关节、膝关节或肩关节置换术患者在MRI检查期间产生的热效应。通过基于临床服务数据库的初步频率分析，收集了11658名植入物携带者患者的MRI检查数据，从而确定了最具代表性的临床情况。通过在类似ASTM的体模上进行588次数值模拟，研究了射频和切换梯度场产生的热效应，考虑了四种假体、两个静磁场值、七个MR序列和七个成像区域。风险评估受到射频场标准和梯度场科学研究的启发。针对射频，根据全身和局部比吸收率平均值定义了三个风险等级；针对梯度场，根据温度升高定义了三个风险等级。在588种情况中，只有50种情况需要谨慎处理。结果表明，全身比吸收率对于金属植入物患者而言并非一个可靠的安全参数。所提出的数值程序可以很容易地扩展到任何其他情况，包括使用详细的解剖模型。
