The magnetic susceptibility effect of gadolinium-based contrast agents on PRFS-based MR thermometry during thermal interventions.
The magnetic susceptibility effect of gadolinium-based contrast agents on PRFS-based MR thermometry during thermal interventions.
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DOI：
10.1186/2050-5736-1-8
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Grüll H
中科院分区：
文献类型：
--
作者：
Hijnen NM;Elevelt A;Pikkemaat J;Bos C;Bartels LW;Grüll H
质子共振频移（PRFS）磁共振（MR）测温利用水质子的电子屏蔽常数的温度依赖性引起的局部磁场变化。因此，任何其他局部磁场变化都将转化为不正确的温度读数，需要相应地加以考虑。在这里，我们调查的磁化率变化引起的流入和存在的顺磁性MR造影剂和它们的影响PRFS测温。进行体模测量，以证明突然钆喷酸葡胺（Gd-DTPA）流入对使用临床3 T磁共振引导高强度聚焦超声（MR-HIFU）系统上的PRFS测温序列测量的相移的影响。通过质子核磁共振谱，测量了Gd-DTPA磁化率的温度依赖性，以及脂质体包封和释放对Gd-DTPA体磁化率的影响。进行了体内研究，以测量静脉注射Gd-DTPA后在大鼠后腿肌肉中引起的温度误差。体模研究显示，注射Gd-DTPA（1.0 mM，临床相关量）后，体模内出现0.6 ± 0.2弧度（平均值±标准差）的显著相移。在37°C下，在平行于主磁场的圆柱体中测量了ΔχGd-DTPA = 0.109 ppm/mM的Gd-DTPA诱导的磁化率偏移。磁化率漂移的温度依赖性显示dΔ x Gd-DTPA/dT = -0.00038 ± 0.00008 ppm/mM/°C。Gd从顺磁性脂质体中释放后，未测量到额外的敏感性效应。在体内，静脉注射Gd-DTPA导致后腿肌肉中心的感知温度变化为2.0°C ± 0.1°C。在MR-HIFU治疗前使用顺磁性MR造影剂可能会影响PRFS MR测温的准确性。根据治疗工作流程，可以预期Gd引起的温度误差范围在-4 ° C和+3 ° C之间。造影剂注射和治疗之间的较长等待时间以及通过增加超声功率缩短消融持续时间将最大限度地减少Gd影响。由于磁场变化在磁化率变化的周围非局部地产生，因此难以补偿由Gd的存在变化引起的相位变化。
Proton resonance frequency shift (PRFS) magnetic resonance (MR) thermometry exploits the local magnetic field changes induced by the temperature dependence of the electron screening constant of water protons. Any other local magnetic field changes will therefore translate into incorrect temperature readings and need to be considered accordingly. Here, we investigated the susceptibility changes induced by the inflow and presence of a paramagnetic MR contrast agent and their implications on PRFS thermometry. Phantom measurements were performed to demonstrate the effect of sudden gadopentetate dimeglumine (Gd-DTPA) inflow on the phase shift measured using a PRFS thermometry sequence on a clinical 3 T magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) system. By proton nuclear magnetic resonance spectroscopy, the temperature dependence of the Gd-DTPA susceptibility was measured, as well as the effect of liposomal encapsulation and release on the bulk magnetic susceptibility of Gd-DTPA. In vivo studies were carried out to measure the temperature error induced in a rat hind leg muscle upon intravenous Gd-DTPA injection. The phantom study showed a significant phase shift inside the phantom of 0.6 ± 0.2 radians (mean ± standard deviation) upon Gd-DTPA injection (1.0 mM, clinically relevant amount). A Gd-DTPA-induced magnetic susceptibility shift of ΔχGd-DTPA = 0.109 ppm/mM was measured in a cylinder parallel to the main magnetic field at 37°C. The temperature dependence of the susceptibility shift showed dΔχGd-DTPA/dT = -0.00038 ± 0.00008 ppm/mM/°C. No additional susceptibility effect was measured upon Gd release from paramagnetic liposomes. In vivo, intravenous Gd-DTPA injection resulted in a perceived temperature change of 2.0°C ± 0.1°C at the center of the hind leg muscle. The use of a paramagnetic MR contrast agent prior to MR-HIFU treatment may influence the accuracy of the PRFS MR thermometry. Depending on the treatment workflow, Gd-induced temperature errors ranging between -4°C and +3°C can be expected. Longer waiting time between contrast agent injection and treatment, as well as shortening the ablation duration by increasing the sonication power, will minimize the Gd influence. Compensation for the phase changes induced by the changing Gd presence is difficult as the magnetic field changes are arising nonlocally in the surroundings of the susceptibility change.