Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands.
Invest Radiol. 2013 Jul;48(7):517-24. doi: 10.1097/RLI.0b013e31829aae98.
The purpose of this study was to investigate the use of Gd-DTPA shortly before magnetic resonance guided high-intensity focused ultrasound MR-HIFU thermal ablation therapy with respect to dissociation, trapping, and long-term deposition of gadolinium (Gd) in the body.
Magnetic resonance-HIFU ablation treatment was conducted in vivo on both rat muscle and subcutaneous tumor (9L glioma) using a clinical 3T MR-HIFU system equipped with a small-animal coil setup. A human equivalent dose of gadopentetate dimeglumine (Gd-DTPA) (0.6 mmol/kg of body weight) was injected via a tail vein catheter just before ablation (≤5 minutes). Potential trapping of the contrast agent in the ablated area was visualized through the acquisition of R1 maps of the target location before and after therapy. The animals were sacrificed 2 hours or 14 days after the injection (n = 4 per group, a total of 40 animals). Subsequently, the Gd content in the tissue and carcass was determined using inductively coupled plasma techniques to investigate the biodistribution.
Temporal trapping of Gd-DTPA in the coagulated tissue was observed on the R1 maps acquired within 2 hours after the ablation, an effect confirmed by the inductively coupled plasma analysis (3 times more Gd was found in the treated muscle volume than in the control muscle tissue). Two weeks after the therapy, the absolute amount of Gd present in the coagulated tissue was low compared with the amount present in the kidneys 14 days after the injection (ablated muscle, 0.009% ± 0.002% ID/g; kidney, 0.144% ± 0.165% ID/g). There was no significant increase in Gd content in the principal target organs for translocated Gdions (liver, spleen, and bone) or in the entire carcasses between the HIFU- and sham-treated animals. Finally, an in vivo relaxivity of 4.6 mmols was found in the HIFU-ablated volume, indicating intact Gd-DTPA.
Magnetic resonance-HIFU treatment does not induce the dissociation of Gd-DTPA. In small-tissue volumes, no significant effect on the long-term in vivo Gd retention was found. However, care must be taken with the use of proton resonance frequency shift-based MR thermometry for HIFU guidance in combination with Gd because the susceptibility artifact induced by Gd can severely influence treatment outcome.
本研究旨在探讨钆喷替酸葡甲胺（Gd-DTPA）在磁共振引导高强度聚焦超声（MR-HIFU）热消融治疗前的应用，以研究钆在体内的解离、捕获和长期沉积情况。
采用配备小动物线圈的临床 3T MR-HIFU 系统，在大鼠肌肉和皮下肿瘤（9L 神经胶质瘤）中进行磁共振-HIFU 消融治疗。通过尾静脉导管在消融前（≤5 分钟）给予人等效剂量的钆喷替酸葡甲胺（Gd-DTPA）（0.6mmol/kg 体重）。通过在治疗前后对目标位置采集 R1 图谱，观察造影剂在消融区域的潜在捕获情况。在注射后 2 小时或 14 天（每组 4 只，共 40 只动物）处死动物。然后，采用电感耦合等离子体技术测定组织和尸体中的 Gd 含量，以研究其体内分布情况。
在消融后 2 小时内获得的 R1 图谱上观察到 Gd-DTPA 在凝固组织中的暂时捕获，该结果通过电感耦合等离子体分析得到证实（处理肌肉体积中的 Gd 含量是对照肌肉组织中的 3 倍）。治疗 2 周后，与注射后 14 天肾脏中的 Gd 含量相比，凝固组织中的 Gd 含量较低（处理肌肉，0.009%±0.002%ID/g；肾脏，0.144%±0.165%ID/g）。在 HIFU 治疗和假治疗动物之间，主要的 Gd 离子转移靶器官（肝、脾和骨）或整个尸体中的 Gd 含量均无明显增加。最后，在 HIFU 消融体积中发现体内弛豫率为 4.6mmol/s，表明 Gd-DTPA 完整。
磁共振-HIFU 治疗不会导致 Gd-DTPA 解离。在小组织体积中，未发现对长期体内 Gd 保留有显著影响。然而，在结合 Gd 进行基于质子共振频率位移的磁共振测温指导 HIFU 治疗时，必须小心谨慎，因为 Gd 引起的磁化率伪影会严重影响治疗效果。
