Microwave ablation of liver tumors: degree of tissue contraction as compared to RF ablation

Purpose

To compare the amount of tissue contraction after microwave (MW) versus radiofrequency (RF) ablation of liver tumors.

Materials and methods

Seventy-five hepatic tumors in 65 patients who underwent percutaneous MW or RF ablations were included in this retrospective study. All patients underwent MRI within 6 months before the ablation and 24 h after the procedure. Two blinded radiologists, by consensus, performed measurements on the corresponding series of pre and post-ablation MRI. Absolute and relative contraction of liver, tumor, and control were calculated and compared.

Results

Thirty-one patients underwent MW ablations, and 44 patients underwent RF ablations. The absolute and relative contraction of the ablation zone were significantly greater with MW than RF ablation (p = 0.003 to <0.001). Thirty-two lesions were visible on both pre- and post-ablation MRI. MW ablation had significantly more tumor contraction as compared to RF ablation (p = 0.003 to 0.009). The control measurements demonstrated no significant difference in normal tissue variation between MW and RF groups.

Conclusions

MW ablation of hepatic tumors produced significantly more contraction of tumor and ablated hepatic tissue compared to RF ablation. Tissue contraction should be taken into account during pre-procedural planning and assessing treatment response by comparing pre- and post-ablation images.

     

Radiofrequency thermal ablation of liver tumors.

Chemotherapy and radiation therapy are ineffective against primary and secondary malignant hepatic tumors. Surgical resection has been considered the only potentially curative option, but few patients with hepatic tumors are candidates for surgery. Recent results suggest that radiofrequency thermal ablation may be an effective, minimally invasive technique for treating malignant hepatic tumors. Sonography is the primary technique for guiding percutaneous ablative procedures. We review the current research and clinical experience with radiofrequency thermal ablation for treating malignant hepatic tumors.     

Percutaneous image-guided radiofrequency ablation of liver tumors

The development of image-guided percutaneous techniques for local tumor ablation has been one of the major advances in the treatment of liver malignancies. Over the past two decades, several methods for chemical or thermal tumor destruction have been clinically tested. Among these methods, radiofrequency (RF) ablation is currently established as the primary ablative modality at most institutions. RF ablation is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma (HCC) when liver transplantation or surgical resection are not suitable options. In addition, RF ablation is emerging as a viable alternate to surgery for inoperable patients with limited hepatic metastatic disease, especially from colorectal cancer. Several series have shown that RF ablation can result in complete tumor eradication in properly selected candidates, and have provided indirect evidence that the treatment improves survival. In this article, we review technique, indications, and clinical results of percutaneous RF ablation in the treatment of HCC and colorectal hepatic metastases.     

A surgical device for radiofrequency ablation of large liver tumors

Radiofrequency ablation has become an accepted treatment option of patients with primary and metastatic liver tumors. We propose an ablation electrode array consisting of 4-8 blade shaped electrodes arranged in a circular geometry for the treatment of large liver tumors. We developed a 3D code based on the finite difference method for evaluating the effect of different numbers of electrodes (4, 6 and 8) and electrode distance on lesion size. The configuration with six electrodes can ablate a volume of 70 x 70 x 40 mm(3) in approximately 5 min, with tissue temperature above 50 degrees C throughout the treatment volume. We then performed an experimental study in polyacrylamide gel in order to validate the theoretical results. The average temperature error between the simulation and the experiment was 3.8% at the center of the electrode array. This study shows that the proposed device potentially allows more rapid treatment of large tumors than current radiofrequency ablation devices.     

The role of contrast-enhanced sonography for radiofrequency ablation of liver tumors.

OBJECTIVE: To assess the feasibility and usefulness of contrast-enhanced sonography for tumor detection and guidance of liver VX2 tumor ablation and to evaluate post radiofrequency ablation effectiveness. METHODS: VX2 tumors were implanted into the livers of 6 rabbits. Both conventional and harmonic gray scale and power Doppler imaging were performed with a commercially available scanner to evaluate the liver tumors before and after intravenous injection of a sonographic contrast agent before and after radiofrequency ablation. Contrast-enhanced imaging was used to detect the tumors before ablation, to guide needle insertion, and to measure the ablation sites after radiofrequency ablation. Pathologic examination was performed for comparison. RESULTS: Three tumors were seen without contrast enhancement, whereas 10 tumors (<1 cm) were detected with contrast enhancement. Intentionally, 2 tumors were completely ablated and 5 tumors were partially ablated. In 3 cases, incompletely ablated tumors could only be identified on contrast-enhanced Doppler imaging by enhancing the detection of residual tumor vascularity. There was excellent concordance between sonographic imaging and gross pathologic findings. CONCLUSIONS: Contrast-enhanced sonographic imaging appears useful for detection of liver tumors and for guiding and monitoring tumor ablation therapies.     

射频消融治疗伴腹水的肝脏肿瘤的安全性探讨

目的：研究腹水存在的情况下，应用射频消融（RFA）治疗肝脏肿瘤的安全性。方法：对14例伴发腹水的肝脏肿瘤患者进行了17次RFA治疗，比较RFA治疗前后肝周腹水的平均CT值、最大深度值及患者血清血红蛋白量，并记录治疗后各种并发症尤其是出血性并发症的发生情况。结果：RFA治疗后均未出现严重并发症，仅1例为自限性出血，治疗前后肝周腹水的最大深度值（P=0.115）、血清血红蛋白量（P=0.091）及除1例出血外的腹水平均CT值（P=0.073）均无统计学差异。其他并发症包括8例发热、6例腹痛，5例存在肝功能损伤加重，但经对症治疗后均于两周内逐渐恢复，属于轻微并发症。结论：腹水不是进行RFA操作的绝对禁忌症，当适量腹水存在时，应用RFA对肝脏肿瘤进行治疗是安全可靠的。     

射频消融对较大肝肿瘤治疗范围与布针方案计算的研究

目的 探讨超声引导射频消融（radio-frequency ablation,RFA）治疗肝肿瘤中治疗范围与射频针伞径、布径次数之间的关系，设计较准确的布针定点定位方法。方法 将肿瘤模式化为类球体，根据球体覆盖原理建立数学模型，应用正棱柱法及正多面体进行推导计算，获得治疗范围与射频针伞径、布针次数的关系式。根据RFA治疗原则消融范围须超越肿瘤周边0.5cm以上，按照覆盖类球体肿瘤的计算结果，采用伞径5.0cm的射频针，治疗4.1～4.3cm的肿瘤须用正四面体法至少布针4个点，治疗4.4～5.6cm的肿瘤用正棱柱法至少布针5～8个点，5.7～6.0cm的肿瘤用三层重叠法至少布针12个点，方能达到较彻底覆盖灭活肿瘤的效果。结果 应用上述治疗方案对32个3.5～6.6cm的病灶设计布针进行RFA治疗，肿瘤灭活率达84.4%。结论 肿瘤类球体治疗计算方案对RFA治疗中不能一次覆盖的较大肿瘤，可提供分区布针方案，有助于提高RFA对肝癌的灭活率，减少肿瘤残留复发。     

Microwave ablation of atrial flutter

Radiofrequency (RF) ablation of the isthmus between the inferior vena cava and the tricuspid ring has proven to be a safe and successful method of treating atrial flutter (AF). However, RF ablation lesions are small in size requiring a considerable number of energy applications to ablate the AF circuit. The aim of this study was to evaluate the feasibility and efficacy of microwave energy for AF ablation. We report a case of sustained typical AF treated successfully and safely by 1 pulse of microwave (MW) energy. This showed it is possible to treat AF with a small number of pulse applications.     

超声造影在肝脏恶性肿瘤微波治疗后的后期随访中的应用价值

目的:评价超声造影(CEUS)在肝脏恶性肿瘤微波消融术后的随访中的应用价值.方法:在35例肝脏恶性肿瘤共49个病灶微波消融治疗的后期随访过程中,出现甲胎蛋白不降或升高、常规超声检查微波灶可疑残存时,应用第二代超声造影剂进行CEUS检查,判断微波灶是否有肿瘤组织残存.CEUS检查后,经过3月以上的随访,以最终临床结果为标准,从而来判断CEUS在肝脏恶性肿瘤微波后的后期随访过程中的价值.结果:在对49个病灶CEUS检查中,43个病灶在三个造影时相中均未见造影剂填充,判断为肿瘤灭活;5个病灶动脉期周边可见增强,判断为肿瘤残存;1个病灶倾向残存;以最终随访结果为诊断标准,CEUS的准确性为91.8％.结论:CEUS是肝脏恶性肿瘤微波治疗后复诊过程中正确地判断肿瘤残存的有效方法,可成为肝癌微波治疗长期随访的重要手段,并且具有较高临床应用价值.     

射频消融治疗大鼠移植性肝肿瘤对脾脏树空状细胞的影响

目的探讨射频消融（RFA）治疗大鼠肝肿瘤对其脾脏组织内树突状细胞（DC）表型的影响及其意义。 方法选取40只正常Sprague Dawley大鼠,10只作为正常对照组,其余30只制作Walker-256肝肿瘤模型后,随机分为RFA后7 d组、RFA后14 d组和荷瘤对照组,每组10只。RFA后7 d组、RFA后14 d组分别于RFA处理后7 d及14 d处死,荷瘤对照组与正常对照组不做RFA处理即处死。取其脾脏组织,采用Ficoll密度梯度离心法分离出单个核细胞,应用流式细胞术检测单个核细胞OX62、OX6及CD86表达水平。 结果正常大鼠与荷瘤大鼠的脾脏单个核细胞中分别有（10.36±3.21）％、（11.69±4.39）％表达OX62,二者比较差异无统计学意义（P＞0.05）。正常大鼠与荷瘤大鼠的脾脏单个核细胞中分别有（76.33±7.86）％、（60.58±6.26）％表达OX6;而分别有（63.06±8.77）％、（40.87±8.66）％表达CD86,2者比较差异均有统计学意义（P<0.05）。RFA后7 d OX62阳性表达率为（10.24±2.49）％,RFA后14 d为（15.10±2.37）％,RFA后14 d组与荷瘤对照组比较差异有统计学意义（P<0.05）。RFA后7 d OX6阳性表达率为（77.45±4.53）％,RFA后14 d为（75.47±5.22）％,2组与荷瘤对照组比较差异均有统计学意义（P<0.05）。RFA后7 d CD86阳性表达率为（46.86±9.42）％,RFA后14 d为（45.53±9.13）％,2组与荷瘤对照组比较差异均无统计学意义（P＞0.05）。 结论荷瘤鼠脾脏组织中未成熟DC比例高,抗原提呈能力弱,RFA促使荷瘤大鼠外周血中DC前体细胞迁移到脾脏组织中的数量增多,并进一步分化成熟,对提高机体在免疫应答中的抗原提呈能力起到促进作用。     

B超引导下微波消融术治疗特殊部位中晚期原发性肝癌的临床价值

目的探讨B超引导下应用微波消融术治疗特殊部位[指邻近胆囊、膈肌、心脏、肝门部、大血管等（即肿瘤距上述器官最短距离≤0．5cm）]中晚期肝癌的有效性和安全性。方法选择2006年10月至2008年12月外科住院的特殊部位中晚期原发性肝癌患者21例作为治疗组,并通过分层随机选取同期普通部位原发性肝癌患者20例作为对照组,两组患者均接受微波消融术治疗。术前术后均行B超,增强CT或MRI检查,同时检测甲胎蛋白（AFP）,并观察不良反应及并发症。结果经微波消融术治疗后1个月,治疗组和对照组肿瘤坏死率分别为90．5％（19／21）、90．0％（18／20）;1个月后治疗组和对照组复查AFP,转阴率均为78．6％（11／14）;治疗组与对照组6个月、1年、2年、3年生存率分别为：100．0％（21／21）、95．0％（20／21）、81．0％（17／21）、71．4％（15／21）和100．0％（20／20）、95．0％（19／20）、90．0％（18／20）、80．0％（16／20）。结论采用微波消融对特殊部位中晚期肝癌进行治疗确切有效,其疗效与普通部位原发性肝癌疗效接近。     

Radiofrequency ablation of liver tumors: the role of microbubble ultrasound contrast agents

Radiofrequency ablation (RFA) is currently indicated for the treatment of primary and metastatic hepatic malignancies. Real-time ultrasound (US) is generally used during the procedure to guide electrode placement, but for evaluating the results of treatment, contrast-enhanced computed tomography and magnetic resonance imaging have traditionally been considered more effective. This view has changed, however, with the recent development of contrast-enhanced ultrasound (CEUS) (eg, using sulfur hexafluoride microbubbles), which can provide valuable information on the effects of RFA more rapidly and economically than computed tomography or magnetic resonance imaging without exposing the patient to ionizing radiation. In our center, CEUS is performed in patients with liver tumors before and immediately after RFA, in selected cases during the procedure as well, and in the follow-up. Between January 2003 and June 2005, we performed CEUS on 350 patients scheduled for RFA of primary or metastatic liver tumors. In 14 (13.4%) of the 96 patients whose disease was metastatic, CEUS revealed lesions that had been missed on the conventional US examination. In most of these cases, the result was a more complete treatment performed under CEUS guidance. In the remaining 2 (14%) of 14, the results of the examination allowed us to avoid subjecting the patient to useless treatment. In our experience, the use of CEUS also improved the management and follow-up of patients undergoing interstitial therapy.     

Retracted: Microwave ablation with cooled‐tip electrode for liver cancer: An analysis of 160 cases

Summary

Alongside conservative therapy regimes, an increasing number of surgical procedures is now available for spinal treatment. With the growing number of endoscopic techniques, the spinal surgeon has more procedures from which to choose, Endoscopic techniques are less invasive on the patient and results show a reduced rate of postoperative risks, e.g. post-diskectomy (failed back) syndrome and comorbidity. Endoscopic techniques are used for treatment of a variety of disorders of the cervical, thoracic and lumbar spine, especially spinal disk protrusions. These techniques are also integrated in a number of spinal surgery procedures, such as thoracoscopic, laparoscopic and retroperitoneal procedures, spinal fusion operations, fracture treatment and tumour extraction. Although there is room for technical improvement and the addition of navigation systems has just begun, the preliminary results are very promising and justify the increased technical requirements and extensive training.     

超声引导下扩大微波消融活体犬脑组织安全性和可行性的实验研究

目的 探讨扩大超声引导下实验家犬脑组织微波消融灶的可行性和安全性,为超声引导微波消融脑肿瘤的临床应用提供实验依据.方法 以不同微波功率(20 W、30 W、40 W)及不同消融时间(60 s、90 s、120 s、150 s、180 s)随机作用于20只家犬脑组织,术中监测颅内压并应用电生理监测仪监测脑电图变化,术后1 h超声探测消融灶声像图变化,术后4~5 h取实验犬脑组织观察消融灶大体及镜下病理变化并测量水肿带宽度.应用多元线性回归分析消融灶长径、宽径与微波输出功率及时间的关系,并建立回归方程.结果 (1)20只实验家犬中10只完成颅内压监测,其中8只从消融开始至消融结束30 min内颅内压未见明显变化;2只颅内压显著升高.(2)脑电图监测结果显示消融灶波形平直,平均波幅(5.7±1.61)μV,消融灶旁开0.3 cm处以弥散性δ和θ波为主,消融灶旁开0.6 cm处以δ波为主.(3)病理大体标本显示微波消融灶呈椭圆形,随着消融时间及功率增加,消融灶长径(L)及宽径(W)均呈线性增加,消融灶长径、宽径与微波输出功率及时间建立的多元线性回归方程分别为L＝0.038P+0.009T,W＝0.012P+0.007T.结论 实验研究结果初步表明,在20 W×60 s~40 W×150 s时间功率组合范围内,消融灶随微波输出功率及消融时间增加而消融范围增大,在此时间功率组合范围内增加脑组织微波消融范围安全、可行.     

SLIR: Synthesis,localization, inpainting,and registration for image-guided thermal ablation of liver tumors

Thermal ablation is a minimally invasive procedure for treating small or unresectable tumors. Although CT is widely used for guiding ablation procedures, yet the contrast of tumors against normal soft tissues is often poor in CT scans, aggravating the accurate thermal ablation. In this paper, we propose a fast MR-CT image registration method to overlay pre-procedural MR (pMR) and pre-procedural CT (pCT) images onto an intra-procedural CT (iCT) image to guide the thermal ablation of liver tumors. At the pre-procedural stage, the Cycle-GAN model with mutual information constraint is employed to generate the synthesized CT (sCT) image from the input pMR. Then, pMR-pCT image registration is carried out via traditional mono-modal sCT-pCT image registration. At the intra-procedural stage, the region of the probe and its artifacts are automatically localized and inpainted in the iCT image. Then, an unsupervised registration network (UR-Net) is used to efficiently align the pCT with the inpainted iCT (inpCT) image. The final transform from pMR to iCT is obtained by concatenating the two estimated transforms, i.e., (i) from pMR image space to pCT image space (via sCT) and (ii) from pCT image space to iCT image space (via inpCT). The proposed method has been evaluated over a real clinical dataset and compared with state-of-the-art methods. Experimental results confirm that the proposed method achieves high registration accuracy with fast computation speed.     

超声造影评估肝脏肿瘤微波消融边界的研究进展

微波消融（microwave ablation,MWA）以其微创、疗效好等特点已广泛应用于肝脏肿瘤的治疗,而消融未达到安全边界会造成治疗不彻底的后果,容易引起肿瘤复发,因此消融术后评估消融边界（ablation margin,AM）是治疗中不可或缺的环节。而超声造影（contrast-enhanced ultrasound,CEUS）具有经济、实时、无放射性、无肾毒性等优点,可作为评估AM的重要方法。本文就超声造影评估肝脏肿瘤微波消融边界的研究进展做一综述。     

超声造影时间-强度曲线在肝脏恶性肿瘤射频消融中的应用价值

目的探讨超声造影时间-强度曲线(TIC)在肝脏恶性肿瘤射频消融(RFA)中的应用价值。 方法选取2014年1月至2016年1月在湖北省肿瘤医院超声科治疗的肝脏恶性肿瘤患者61例,均经影像学手段、肝穿刺行组织学病理活检或手术病理证实为肝脏恶性肿瘤,共81个病灶。根据随机数字表法将患者分为对照组及观察组,其中观察组患者30例,共46个病灶,利用超声造影检查后行RFA,做出TIC;对照组患者31例,共35个病灶,常规超声检查后行RFA。比较观察组肝脏恶性肿瘤患者RFA前后正常肝实质与肿瘤组织超声造影定量分析结果的差异,同时比较肝脏恶性肿瘤患者RFA治疗后1个月肝脏肿瘤残留病灶与正常肝实质的超声造影定量分析结果,并比较观察组与对照组患者射频消融疗效的差异,采用Kappa一致性检验分析超声造影与增强CT/磁共振(MRI)检查结果的一致性。 结果RFA治疗前,运用超声造影对观察组46个肝脏病灶和肝脏肿瘤周边区的正常肝实质进行量化分析,术前肿瘤病灶造影剂灌注初始时间(IT)、最大峰值到达时间(PT)、灌注加速时间(AT)[(13.21±3.47)s,(17.56±7.12)s,(19.02±3.35)s]低于术前正常肝实质IT、PT、AT值[(18.75±3.68)s,(31.20±6.13)s,(34.50±3.12)s],灌注加速斜率(AS)(2.89±0.94)高于术前正常肝实质AS值(1.28±0.58),组间比较均差异有统计学意义(t＝7.43,9.85,22.93,9.89;均P<0.01)。RFA治疗1个月后,81个病灶中,有67个病灶未出现造影剂增强情况,8个病灶周边出现高增强,另外4个病灶出现内部不均匀高增强,2个病灶均匀性高增强;TIC分析显示肿瘤完全消融部分动脉相、门脉相及延迟相均无造影剂充填,肿瘤残留部位的IT、PT、AT值[(15.11±2.57)s,(20.97±3.33)s,(18.32±0.27)s]小于正常肝实质[(19.90±3.96)s,(35.68±2.92)s,(31.28±0.16)s],组间比较均差异有统计学意义(t＝9.13,29.89,37.17;均P<0.01)。随访3～6个月,以增强CT/MRI为判断肿瘤消融程度的对照指标,两组患者在经过治疗后,观察组患者的肿瘤完全消除率为91.30%(42/46),对照组患者的肿瘤完全消除率为71.43%(25/35),观察组患者的治疗效果明显优于对照组患者的治疗效果,组间比较差异有统计学意义(χ²＝5.49,P<0.05)。RFA术前超声造影与增强CT/MRI检出率具有较高一致性(Kappa＝0.87,P<0.05),RFA术后超声造影与增强CT/MRI检出率具有较高一致性(Kappa＝0.93,P<0.05)。 结论超声造影时间-强度曲线能有效识别肝脏恶性肿瘤组织,与增强CT/MRI检查具有较高一致性,在指导肝脏恶性肿瘤患者RFA治疗中具有较高的应用价值,值得在临床推广应用。