Magnetic resonance guidance for radiofrequency ablation of liver tumors

Image-guided thermal ablation of liver tumors is a minimally invasive treatment option. Techniques used for thermal ablation are radiofrequency (RF) ablation, laser interstitial thermotherapy (LITT), microwave (MW) ablation, high-intensity focused ultrasound (HIFU), and cryoablation. Among these techniques RF ablation attained widespread consideration. Image guidance should ensure a precise ablation therapy leading to a complete coagulation of tumor tissue without injury to critical structures. Therefore, the modality of image guidance has an important impact on the safety and efficacy of percutaneous RF ablation. The current literature regarding percutaneous RF ablation mainly describes the use of computed tomography (CT) and ultrasonography (US) guidance. In addition, interventional MR systems offer the possibility to utilize the advantages of MR imaging such as excellent soft-tissue contrast, multiplanar and interactive capabilities, and sensitivity to thermal effects during the entire RF ablation procedure. Monitoring of thermally induced coagulation by MR imaging is supportive to control the ablation procedure. MR imaging can be advantageously used to guide overlapping ablation if necessary as well as to define the endpoint of RF ablation after complete coverage of the target tissue is verified. Furthermore, monitoring of thermal effects is essential in order to prevent unintended thermal damage from critical structures surrounding the target region. Therefore, MR-guided RF ablation offers the possibility for a safe and effective therapy option in the treatment of primary and secondary hepatic malignancies. The article summarizes the role of MR guidance for RF ablation of liver tumors.     

Real-time MR temperature mapping of rabbit liver in vivo during thermal ablation.

It has been shown that quantitative MRI thermometry using the proton resonance frequency (PRF) method can be used to noninvasively monitor the evolution of tissue temperature, and to guide minimally-invasive tumor ablation based on local hyperthermia. Although hepatic tumors are among the main targets for thermal ablation, PRF-based temperature MRI of the liver is difficult to perform because of motion artifacts, fat content, and low T(*) (2). In this study the stability of real-time thermometry was tested on a clinical 1.5 T scanner for rabbit liver in vivo. The fast segmented EPI principle was used together with respiratory gating to limit respiratory motion artifacts. Lipid signal suppression was achieved with a binomial excitation pulse. Saturation slabs were applied to suppress artifacts due to flowing blood. The respiratory-gated MR thermometry in the rabbit liver in vivo showed a standard deviation (SD) of 1-3 degrees C with a temporal resolution of 3 s per slice and 1.4 mm x 1.9 mm spatial resolution in plane (slice thickness = 5 mm). The method was used to guide thermal ablation experiments with a clinical infrared laser. The estimated size of the necrotic area, based on the thermal dose calculated from MR temperature maps, corresponded well with the actual lesion size determined by histology and conventional MR images obtained 5 days posttreatment. These results show that quantitative MR temperature mapping can be obtained in the liver in vivo, and can be used for real-time control of thermal ablation and for lesion size prediction.     

Four-dimensional transcatheter intraarterial perfusion MRI monitoring of radiofrequency ablation of rabbit VX2 liver tumors

Purpose:

To investigate the hypothesis that four‐dimensional (4D) transcatheter intraarterial perfusion (TRIP) magnetic resonance imaging (MRI) can quantify immediate perfusion changes after radiofrequency (RF) ablation in rabbit VX2 liver tumors.

Materials and Methods:

Nine New Zealand White rabbits were used to surgically implant VX2 liver tumors. During ultrasound‐guided RF ablation, tumors received either a true or sham ablation. After selective catheterization of the left hepatic artery under x‐ray fluoroscopy, we acquired pre‐ and post‐RF ablation 4D TRIP MR images using 3 mL of 2.5% intraarterial gadopentetate dimeglumine. Two regions‐of‐interest were drawn upon each tumor to generate signal‐intensity time curves. Area under the curve (AUC) was calculated to provide semiquantitative perfusion measurements that were compared using a paired t‐test (α = 0.05). Ablated tissue was visually confirmed on pathology using Evans blue dye.

Results:

Mean AUC perfusion of VX2 tumors for the true ablation group decreased by 92.0% (95% confidence interval [CI]: 83.3%–100%), from 1913 (95% CI: 1557, 2269) before RF ablation to 76.6 (95% CI: 18.4, 134.8) after RF ablation (a.u., P < 0.001). Sham‐ablated tumors demonstrated no significant perfusion changes.

Conclusion:

4D TRIP MRI can quantify liver tumor perfusion reductions in VX2 rabbits after RF ablation. This MRI technique can potentially be used to improve tumor response assessment at the time of RF ablation. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

In vivo porcine liver radiofrequency ablation with simultaneous MR temperature imaging

PURPOSE: To demonstrate in vivo MR-guided temperature mapping during radiofrequency (RF) ablation of the liver with a commercially available RF generator modified to allow simultaneous RF treatment and MRI. MATERIALS AND METHODS: A commercial RF generator was modified using passive filtering to allow the continuous application of the treatment current during MRI studies. A total of six ablations were performed with the device in vivo in three porcine livers, and imaging was concurrently performed using one of two different temperature mapping strategies. RESULTS: MR images acquired during RF ablation demonstrated no noticeable interference from the RF ablation device, which was operated at clinically relevant power levels. Temperature maps showed areas of heating that were consistent with the dimensions of the RF ablation probe, with some asymmetry (likely depending on the orientation of the probe and heat propagation effects), and some differences in heating-spot area stability depending on the specific temperature mapping strategy used. Lesions were visualized on post-ablation imaging and sectioning. CONCLUSION: The feasibility of performing RF ablation with a modified commercial RF generator simultaneously with MRI was demonstrated. Interference-free MR temperature maps were produced with both variable respiratory motion and mechanical ventilation, and showed the extent of heating as the ablation progressed.     

肝癌射频消融后的影像学评价

射频消融术(RFA)是肝癌综合治疗中的一项重要手段,尤其是对小肝癌的治疗,临床疗效较好。由于RFA治疗范围的局限,术后常有肿瘤病灶的残存或出现复发。因此,准确地评价RFA术后疗效非常重要。本文综述了不同影像手段对RFA治疗肝癌的疗效评价,同时讨论不同评价方法的优劣,以冀为采取合理的影像手段,做出正确的临床处理提供参考。     

射频消融技术在胆囊癌肝浸润外科手术中的应用价值

目的探讨射频消融技术在胆囊癌肝浸润外科手术过程中的应用价值。方法选择2007年9月-2009年8月入院的胆囊癌肝浸润患者34例,分为外科手术组和射频消融组。20例外科手术组患者行胆囊切除术加肝楔形切除术,其中男12例,女8例,年龄53~76岁,平均69.0岁。14例射频消融组患者行外科开腹射频消融术,其中男9例,女5例,年龄64~78岁,平均71.5岁。术后随访,观察并比较两组的生存率及并发症情况。结果外科手术组1年生存率为14/20,射频消融组1年生存为8/14,两组比较差异无统计学意义(P>0.05),2年生存率有无差异还在进一步随访观察中。外科手术组术后发热19例,恶心呕吐13例,腹腔出血3例,胆道损伤3例,胆漏2例;射频消融组术后发热11例,轻度恶心呕吐8例,胆囊床周边少量积血2例,无腹腔出血、胆道损伤、胆漏发生。两组在术后发热、恶性呕吐方面差异无统计学意义(P>0.05),但在腹腔出血、胆道损伤、胆汁漏方面有统计学差异(P<0.05)。结论开腹射频消融技术可用于外科治疗胆囊癌伴肝浸润,且在降低术后并发症发生率方面优于单纯外科手术。     

射频消融亚致死性温度对肝癌干细胞的影响

目的 研究亚致死温度射频消融(RFA)对肝癌干细胞(LCSC)产生及其相关转录因子表达的影响.方法 利用小鼠Hep1-6肝癌细胞株和肝细胞癌(HCC)患者临床样品,检测LCSC相关标志物和转录因子的表达.结果 不同温度分别刺激Hep1-6细胞后发现,45℃是不能诱导细胞死亡的亚致死性温度.流式细胞仪(FCM)检测显示45℃处理可引起CD13+、CD44+、CD90+、CD133+ Hep1-6细胞水平明显上调,提示45℃温度导致Hep1-6细胞中以上各型LCSC产生增加;实时定量聚合酶链反应(RT-qPCR)检测显示45℃温度导致CD13、CD90、CD133 mRNA水平明显上调.CD13 mRNA水平在5例HCC患者复发肝癌组织中均明显上调,CD133 mRNA在4例复发肝癌中上调,CD90 mRNA仅在1例复发肝癌中上调;FCM检测显示CD13+ LCSC水平在4例复发肝癌中明显上调,CD133+ LCSC水平仅在1例复发肝癌中上调,提示CD13+ LCSC水平上调与45℃温度关系更密切.RT-qPCR检测显示4例CD13+ LCSC上调的复发肝癌患者13个LCSC相关转录因子中Sox2、Stat1明显上调,FCM检测显示45℃处理Hep1-6细胞后Sox2、Stat1 mRNA明显上调.用Sox2、Stat1 siRNA分别沉默了Sox2、Stat1基因,表明Sox2 、Stat1均参与了45℃温度诱导的CD13+ LCSC产生.结论 RFA治疗中45℃亚致死性温度所致CD13+ LCSC水平增高与Sox2、Stat1表达有关.该结果对肝癌复发研究有一定借鉴意义.     

右美托咪定复合瑞芬太尼在肝癌射频消融术中的应用

 

目的 评价在肝癌射频消融术(radiofrequency ablation,RFA)中使用右美托咪定复合瑞芬太尼后的镇静和镇痛效果。方法 选择美国麻醉师协会分级标准为Ⅱ~Ⅲ级择期行RFA的肝癌患者60例,随机分为右美托咪定+瑞芬太尼组(Dex组)和丙泊酚+瑞芬太尼组(对照组),每组30例。分别记录两组局麻浸润前15 min(T₀)、局麻浸润时(T₁)、手术开始时(T₂)、射频温度达峰值时(T₃)、术毕烧针道时(T₄)及停药后5 min(T₅)时的心率(HR)、血压(收缩压SBP、舒张压DBP)、呼吸频率(R)、血氧饱和度(SPO₂)、清醒镇静评分(OAA/S)、脑电双频指数(BIS),同时记录围术期不良反应及患者满意度。结果 Dex组在围术期的收缩压、舒张压、呼吸频率、血氧饱和度的变化趋势与对照组相比有统计学差异(F=2.496,P=0.033;F=2.658,P=0.025;F=11.900,P=0.000;F=6.378,P=0.000),心率变化趋势没有统计学差异(F=0.704,P=0.622);Dex组OAA/S评分低于对照组(F=6.978,P=0.000),Dex组BIS高于对照组(F=519.780,P=0.000);Dex组在围术期呼吸抑制、术中体动、恶心呕吐及苏醒延迟少于对照组(χ²=15.635,P=0.000、χ²=9.834,P=0.000、χ²=6.613,P=0.013);Dex组患者满意度高于对照组(χ²=7.938,P=0.000)。结论 肝癌患者在RFA中使用右美托咪定复合瑞芬太尼可获得满意的镇痛镇静效果,患者可被唤醒,麻醉管理更加安全高效。

     

射频消融联合肝动脉化疗栓塞治疗肝癌的应用

以超声、CT等为主要引导方式的经皮射频消融(RFA)等局部热消融技术在肝癌治疗中发挥了重要的作用.然而,对血供丰富的较大肝癌疗效受限.经肝动脉化疗栓塞(TACE)可有效减少肝癌的血供,并具有创伤小,适应证广,并发症少等特点,成为肝癌患者姑息治疗及术前、术后新辅助治疗的有效手段之一.因此,富血供肝肿瘤RFA治疗前应用TACE,通过栓塞肿瘤供血动脉造成肿瘤缺血,进而减少血流带走热量,可扩大消融范围提高RFA疗效,是肝癌RFA联合治疗常用的方法.本文针对RFA联合TACE治疗肝癌的应用现状及疗效进行综述.     

MR-guided radiofrequency ablation in a 0.2-T open MR system: technical success and technique effectiveness in 100 liver tumors

PURPOSE: To evaluate the feasibility and technique effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation of hepatic malignancies. MATERIALS AND METHODS: In 64 patients, 100 primary (N = 19) or secondary (N = 81) liver tumors (mean diameter = 24.7 mm; range = 4-60 mm) were treated with 87 sessions of MR-guided RF ablation. The entire ablation procedure was carried out at an 0.2-T open MR system by using MR-compatible internally cooled electrodes. T2-weighted turbo spin echo sequences (TR/TE = 3500 msec/110 msec) were used to monitor thermally induced coagulation. Technique effectiveness was assessed four months after the last RF ablation by dynamic MR imaging at 1.5-T. RESULTS: MR-guided RF ablation procedures were technical successful in 85 of 87 (97.7%) assessed at the end of each session. Complete coagulation was intended in 99 of 100 tumors. Technique effectiveness was observed in 92 of 99 (92.9%) of these tumors. To achieve complete coagulation 82 of 92 (89.1%) tumors required a single session. T2-weighted sequences were accurate to monitor the extent of coagulation and were supportive to guide overlapping ablation. There were two of 87 (2.3%) major and seven of 87 (8.0%) minor complications. CONCLUSION: MR-guided RF ablation is a safe and effective therapy in the treatment of hepatic malignancies. MR imaging offers an accurate monitoring of thermally-induced coagulation, thus enabling complete tumor coagulation in a single session.     

磁共振导向技术在乳腺癌射频消融治疗中的应用

目的 探讨MRI引导下经皮射频消融(RFA)对乳腺癌治疗的应用价值.方法 12例经穿刺病理确诊的乳腺癌患者,临床分期Ⅳ期7例(肺转移6例,骨转移1例);Ⅲ期5例(患者因严重高血压、糖尿病或肝肾功能不全,为手术禁忌或年龄大拒绝手术).全部患者经4~6周期化疗或内分泌治疗及靶向治疗等综合治疗后乳腺残留病灶难以进一步缩小,影像学检查乳腺病灶残存,再次穿刺病理活检证实有活性肿瘤组织细胞残存,遂对乳腺残存病灶行RFA治疗.术后1、3、6、12个月临床随访,3、6、12个月影像学复查.结果 本组12例患者行18次RFA,治疗后MRI检查示肿瘤病灶均发生坏死,瘤内血供消失,无强化区;术后3、6、12个月MRI复查病灶消失,原瘤区无血供,无强化区;6个月及1年X线检查显示原乳腺病灶模糊或者消失.乳腺病灶影像学检查全部达到完全缓解(CR),有效率为100%.术后随访1年所有患者均生存.结论 磁共振介入技术对乳腺癌RFA治疗安全有效.     

肝动脉化疗栓塞术联合CT引导下射频消融治疗大肝癌的疗效和安全性

 目的 评价肝动脉化疗栓塞术(transcatheter arterial chemoembolization, TACE)联合CT引导下经皮穿刺射频消融治疗大肝癌的疗效及安全性。方法 回顾性分析52例经穿刺病理或影像学诊断的大肝癌患者临床资料,患者均先行1次TACE术,术后2周复查增强CT,对碘油沉积欠缺的区域在CT导向下进行射频消融治疗,术后复查甲胎蛋白(AFP)、增强MRI或CT评价肿瘤体积缩小及坏死情况,随访时间为12个月。结果 52例 (56个病灶)手术均获得成功。TACE术前病灶最大径为(12.7±2.7)cm,射频术后1个月病灶最大径为(6.1±1.9)cm,肿瘤大小较术前均有不同程度缩小(t=14.416,P<0.05)。TACE术前AFP值为(4156±689)ng/ml,射频术后1个月为(256±178)ng/ml,AFP值明显下降(t=39.485,P<0.05)。其中完全消融(CR)26例,大部分消融(PR)21例,稳定(SD)4例,进展(PD)1例,总体有效率为90.4%,12个月生存率为92.3%。结论 TACE联合CT导向下射频消融治疗大肝癌是一种安全、有效、微创的治疗方法。     

Prediction of cell necrosis with sequential temperature mapping after radiofrequency ablation

Purpose

To assess the feasibility of magnetic resonance (MR) thermometry after thermoablative therapy and to quantitatively evaluate the ability of two sequence types to predict cell necrosis.

Methods

Twenty patients with hepatic tumors were treated by MR‐guided radiofrequency ablation. For each 10 patients, postinterventionally performed gradient echo and segmented echo planar imaging sequences were used to calculate temperature maps based on the proton resonance frequency shift method. Contrast‐enhanced images acquired 1 month after therapy were registered on the temperature maps and the necrotic, nonenhanced area was segmented and compared to the area with a displayed temperature above 60°C. Sensitivity and positive predictive value of the temperature map was calculated, using the follow‐up imaging as the gold standard.

Results

Temperature mapping reached acceptable image quality in 45/47 cases. Sensitivity, ie, the rate of correctly detected coagulated tissue was 0.82 ± 0.08 for the gradient echo imaging (GRE) sequence and 0.81 ± 0.14 for the echo planar imaging (EPI) sequence. Positive predictive value, ie, the rate of voxel in the temperature map over 60°C that actually developed necrosis, was 0.90 ± 0.07 for the GRE sequence and 0.84 ± 0.11 for the EPI sequence.

Conclusion

Sequential MR temperature mapping allows for the prediction of the coagulation zone with an acceptable sensitivity and positive predictive value using EPI and GRE sequences. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

射频消融对原发性肝癌治疗评价及预后危险因素分析

目的：分析射频消融对原发性肝癌治疗及复发的临床治疗评价并探讨影响预后的相关危险因素。方法纳入本院肿瘤科经射频消融治疗的164例患者进行分析,研究内容包括治疗前后的肝功能、甲胎蛋白(AFP)的变化,复发率及生存期,并纳入与预后相关的危险因素,先通过单因素条件的 Logistic 回归分析预后的相关危险因素,再采用 COX 风险模型对影响预后的相关危险因素进行分析。结果治疗后患者的 AFP 及肝功能均明显改善,与治疗前比较差异有统计学意义(P <0.05);肿瘤完全消融率达87.50%;经过治疗后的肿瘤1、2、3、4年的复发率为17.9%、29.9%、45.9%、55.0%。结论射频消融术是一种有效的治疗原发性肝癌的治疗方法,原发性肝癌预后危险因素为肿瘤的分化程度、肿瘤复发、TNM 分期、AFP、术中输血、手术方式、肿瘤和手术部位、术前转氨酶水平。     

射频技术在临床中的应用

近20年来,射频(radiofrequency,RF)技术以其微创、靶向、疗效好,不良反应少等特点应用于临床各种疾病的治疗有了巨大的发展。从治疗实体肿瘤,逐渐发展到治疗实质器官的良性病变如脾亢、前列腺增生,以及在心血管系统、骨骼系统、消化系统、妇科疾病、治疗疼痛以及医学美容等多个领域得到广泛应用并取得了较好的疗效。本文就其治疗原理、不同机型及特点以及在临床方面的应用作一综述。     

Study of laser ablation in the in vivo rabbit brain with MR thermometry

PURPOSE: To investigate the peak temperature and thermal dose (T(43)) as tissue damage indicators for thermal therapy. MATERIALS AND METHODS: The proton resonant frequency (PRF) shift thermal coefficient was calibrated on six in vivo rabbit brains during interstitial laser ablation. The peak temperature and T(43) were correlated with the lesion boundary observed on T2-weighted spin-echo (SE) MRI at 4 hours post-heating in seven thermal lesions using direct MR measurement and analysis based on a binary discriminate model. RESULTS: The peak temperature and T(43) were 48.3 +/- 1.7 degrees C and 191 +/- 219 minutes, respectively, from the direct MR measurement. The values derived by the binary discriminate analysis were 47.8 +/- 2.2 degrees C and 28 +/- 41 minutes, respectively. CONCLUSION: Our results suggest that tissue damage in rabbit brain 4 hours after thermal ablation can be predicted reliably from a threshold temperature of approximately 48 degrees C.     

MR-guided radiofrequency ablation of hepatic malignancies at 1.5 T: initial results

Purpose

To assess the feasibility of magnetic resonance (MR)‐guided radiofrequency ablation (RFA) of hepatic malignancies using a high‐field MR scanner.

Materials and Methods

A total of 10 patients with 14 primary (N = 1) or secondary (N = 13) hepatic malignancies underwent MR‐guided RFA using a closed‐bore 1.5 T MR scanner. Lesion diameters ranged from 2.0 cm to 4.7 cm. RFA was performed using a 200‐W generator in combination with a 3.5‐cm LeVeen electrode applying a standardized energy protocol.

Results

RFA was technically feasible in all patients. Necrosis diameter ranged from 2.5 cm to 6.8 cm. The mean follow‐up period is 12.2 ( 1 - 18 ) months. In nine out of 10 patients, local tumor control was achieved. For this purpose, a second CT‐guided RFA was required in two patients. In four patients, multifocal hepatic tumor progression occurred, with the treated lesion remaining tumor‐free in three of these patients. Two patients showed extrahepatic tumor progression. Four patients remained tumor‐free. No major complications occurred.

Conclusion

MR‐guided RFA of hepatic malignancies in a closed‐bore high‐field MR scanner is technically feasible and safe. It can be advantageous in locations considered unfavorable for CT‐guided puncture or in patients in which iodinated contrast material is contraindicated. J. Magn. Reson. Imaging 2004;19:342–348. © 2004 Wiley‐Liss, Inc.

     

MR monitoring of MR-guided radiofrequency thermal ablation of normal liver in an animal model

The purpose of this study was to determine the suitability of MRI to accurately detect radiofrequency (RF) thermoablative lesions created under MR guidance. In vivo RF lesions were created in the livers of six New Zealand White rabbits using a 2-mm-diameter titanium alloy RF electrode with a 20-mm exposed tip and a 50-W RF generator. This was performed using a 0.2T clinical C-arm MR imager for guidance and monitoring. Each animal was sacrificed and gross evaluation was performed. Histologic correlation was performed on the first two animals. The MR-compatible RF electrode was easily identified on rapid gradient-echo images used to guide electrode placement. A single lesion was created in each rabbit liver. Lesions ranged from approximately 10 to 17 mm in diameter (mean, 13.5 mm). T2-weighted and short T1 inversion recovery (STIR) images demonstrated lesions ranging in diameter from 12 to 18 mm (mean, 14.6 mm). Lesion dimensions determined from images closely correlated with those determined at gross examination with the discrepancy never exceeding 2 mm, for an r² value of .87. MRI performed at the time of MR-guided RF ablation accurately demonstrated created lesions. This modality may provide a new option for the treatment of local and regional neoplastic disease.     

鼻内镜下低温等离子消融术治疗腺样体肥大43例临床分析

目的：探讨鼻内镜下低温等离子消融术对腺样体肥大的治疗效果,为临床治疗提供参考。方法应用随机数字表法将86例腺样体肥大患者随机分为2组,每组43例,以接受鼻内镜下电动吸切术治疗者为对照组,以接受鼻内镜下低温等离子消融术治疗者为观察组。对比2组治疗相关情况及手术并发症发生情况。结果2组手术时间比较,差异无统计学意义（P＞0.05）,而观察组术中出血量少于对照组,术后正常通气时间及住院时间短于对照组,差异有统计学意义（P＜0.05）。2组间术后6个月时治疗总有效率比较,差异无统计学意义（P＞0.05）。观察组术后6个月内的手术并发症发生率明显低于对照组,差异有统计学意义（P＜0.05）。结论鼻内镜下低温等离子消融术可在不降低治疗总有效率的同时,有效地改善手术治疗情况及降低术后并发症发生率。