Dynamics of ablation plume particles generated during excimer laser corneal ablation

Background and Objective: Although the empirical characteristics of ArF excimer laser corneal ablation have been well documented, the exact ablation mechanisms are not well understood. The present paper reports a quantitative analysis of corneal ablation plumes using in situ time resolved laser light scattering and Raman spectroscopy. Study Design/Materials and Methods: Bovine corneas were used as the ArF excimer laser ablation targets. Light scattering data were recorded from the ablation plume as a function of height above the tissue surface and as function of delay time with respect to the ablative ArF laser pulse. Results: Raman spectra of the ablation plume allow identification of the particles as water. Mean plume particle diameters are found to decrease with height, while the particle volume fractions are relatively constant. The total volume of plume particles correlates well with the total volume of water in the ablated corneal tissue. Conclusion: The finding of a non-evolving plume composed of water spherules, combined with the excellent agreement between total volume of water in the plume and the content of water in the ablated corneal tissue, support the concept of photodecomposition or “cold ablation” for corneal tissue during ArF excimer laser ablation. © 1995 Wiley-Liss, Inc.     

Er:YAG laser ablation of tissue: measurement of ablation rates

The ablation of both soft and hard tissue using the normal-spiking-mode Er:YAG laser has been quantified by measuring the number of pulses needed to perforate a measured thickness of tissue. Bone is readily ablated by 2.94 microns radiation; however, at per pulse fluences greater than 20 J/cm2, plasma formation decreases ablation efficiency. At low fluence, desiccation can prevent efficient ablation of bone. The ablation efficiency for aorta and skin is higher than for bone. The ablation efficiency, 540 micrograms/J, and the ablation depth per pulse, greater than 400 microns, for skin are too high to be readily explained by simple models of ablation and thus provide evidence for a more complex explosive removal process.     

射频消融治疗快速心律失常疗效初步分析

目的对我科近年来14例快速心律失常的射频消融疗效进行总结.方法14例患者中,术前体表12导心电图及食道调搏诊断为室上性心动过速,心内电生理检查确诊9例为左侧旁道,3例为房室结双径路,经射频消融旁道及慢径;另有2例为室性心动过速,采用起搏标测,标测位置满意后射频消融.结果12例室上性心动过速病人手术成功率100%,无一例严重并发症,长期随访无一例复发.2例室性心动过速病人,一例手术成功,术后一年复发,一例手术失败.结论射频消融是目前治疗折返引起的室上性心动过速的唯一创伤小、危险少、效果最满意的方法.目前除一些左室特发性室速及束支折返性室性心动过速外,室性心动过速的发病机理还不完全明确,消融结果欠满意,且复发率高.因手术费用较高,室性心动过速病人手术应慎重,可作为顽固性室速药物治疗无效情况下的一种补充办法.     

超声引导下射频消融联合乙醇消融与单纯射频消融治疗甲状腺良性囊实性结节的疗效对比

目的探讨射频消融联合乙醇消融与单纯射频消融对良性囊实性甲状腺结节治疗效果的差异。方法选取2015年1月-2018年7月就诊于郑州大学第一附属医院甲状腺外科,颈部彩超确认为甲状腺囊实性结节,且结节最大直径≥20 mm,穿刺病理结果为良性,拟行甲状腺射频消融手术的80例患者的病理资料,根据病情及患者意愿,分别行单纯射频消融手术治疗(A组,n=40)和射频消融联合乙醇消融治疗(B组n=40),观察术中射频消融能量差异、术后并发症情况、术后12个月患者满意度和术后3、6、12个月结节体积及最大直径的变化。分析两组各自的临床效果及两组之间的疗效差异,符合正态分布的计量资料组间比较采用两因素重复测量方差分析或独立样本r检验的统计学方法。不符合正态分布的计量资料组内比较采用Friedman的秩和检验,两两比较采用Bonferroni校正。计数资料组间比较采用x²检验。结果B组术后12个月结节体积较术前缩小值大于A组,差异有统计学意义[(7.0±5.1)mL比(5.5±4.9)mL,P<0.05];B组术后12个月结节最大直径较术前缩小值大于A组,差异有统计学意义[(1.5±0.6)cm比(1.4±0.8)cm,P<0.05];术后6-12个月期间.B组结节缩小趋势较A组更明显(P<0.05)。B组射频能量小于A组,差异有统计学意义[(2.37+1.18)kJ比(3.89±1.17)kJ,P<0.05]。术后2例出现声音降低,2周内恢复;术中1例出现局部出血,消融后止血。A组患者满意度,与B组患者满意度相比,差异无统计学意义(87.5%比90.0%,P>0.05)。结论甲状腺良性囊实性结节行射频消融联合乙醇消融治疗,较单纯射频消融治疗可以取得更好的结节缩小效果,且能够降低消融使用能量。     

Bipolar radiofrequency ablation of the kidney: comparison with monopolar radiofrequency ablation

PURPOSE: We report initial ex vivo and in vivo studies using bipolar radiofrequency (RF) ablation of porcine kidneys. An internal ground electrode is positioned in the kidney opposite the RF electrode, resulting in ablation of all the intervening renal tissue. MATERIALS AND METHODS: Ex vivo preparations of 10 porcine kidneys were perfused continuously with Ringer's solution and treated with either standard external grounded RF (N = 3) or bipolar RF ablation with 1 (N = 2), 2 (N = 3), or 3 (N = 2) cm of separation between the ground probe and the RF probe using a Model 30 RITA generator (RITA, Mountain View, CA). Target temperatures were 90 degrees C for 8 minutes. Gross and histologic assessments were made acutely. Four domestic pigs were treated with monopolar RF ablation of the lower pole of one kidney and bipolar RF with a 12-mm separation between the probes of the contralateral lower pole. Animals were harvested 48 hours later to maximize tissue damage for gross measurements and histologic evaluation. RESULTS: Ex vivo studies revealed grossly monopolar lesions 1.5 cm in maximum diameter and 1.75 cm(3) in volume. In comparison, bipolar lesions were 2.8 cm in maximum diameter and 10.3 cm(3) in volume using 3 cm of electrode separation. There was histologic evidence of cell death in all specimens. In vivo studies showed two distinct gross lesions with RF: one blanched and one hemorrhagic. Using bipolar RF, larger blanched lesions were achievable than with monopolar RF (2.80 cm(3) v 1.63 cm(3)). Overall, the combinations of blanched and hemorrhagic lesions were similar with monopolar and bipolar RF (5.01 v 5.31 cm(3)). Histologic evaluation verified cell death in the blanched lesions and rare areas of normal tissue in the hemorrhagic lesions. CONCLUSIONS: As shown by ex vivo data, bipolar RF can create larger lesions than does monopolar RF. In vivo, at 48 hours, both blanched and hemorrhagic gross lesions were seen using RF. In this model, blanched lesions predominated when performing bipolar RF.     

Temperature profiles of 980- and 1,470-nm endovenous laser ablation,endovenous radiofrequency ablation and endovenous steam ablation

Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures.     

Pulsed CO2 laser tissue ablation: Measurement of the ablation rate

Ablation of guinea pig skin using a CO₂ laser emitting 2-μsec-long pulses has been quantified by measuring the mass of tissue removed as a function of incident fluence per pulse. The mass-loss curves show three distinct regimes in which water evaporation, explosive tissue removal, and laser-induced plasma formation dominate. The data are fit to two models that predict that the mass removed depends either linearly or logarithmically on fluence. Although the data are best fit by a linear dependence upon fluence, plasma formation at high fluences prohibited obtaining data over a wide enough fluence range to differentiate unambiguously between the two models. Ablation efficiency, ablation thresholds, and the optical penetration depth at 10.6 μm were obtained from the measurements.     

Hepatic radiofrequency ablation

HYPOTHESIS: Hepatic radiofrequency ablation (RFA) is effective in treating patients with unresectable hepatic malignancies. DESIGN: Case series of 123 patients with unresectable hepatic tumors or tumors with histological findings not traditionally treated by means of hepatic resection were considered for hepatic RFA. Median follow-up was 20 months. SETTING: Tertiary referral center. PATIENTS: The 123 patents underwent 168 RFA sessions from January 1, 1998, through September 30, 2001. Sixty-nine patients were male and 54, female; average age was 65 years (range, 1-89 years). Fifty-two patients had metastatic colorectal cancer; 30, hepatocellular carcinoma; and 41, cancers with other histological findings. INTERVENTIONS: A 200-W, cooled-tip RF probe system was used for all cases. Probe placement and ablation were monitored by means of real-time ultrasonography or fluoroscopic computed tomography. Final tissue temperature of greater than 50 degrees C was achieved in all cases. RESULTS: Initial treatment sessions were percutaneous in 87 patients, open operations in 33, and laparoscopic in 3. Repeated sessions were percutaneous in all but 2 patients. The mean number of lesions treated per session was 2.7 (range, 1-24). Mean tumor size was 5.2 cm (range, 0.5-15.0 cm). One death occurred within 30 days of a procedure. No hepatic bleeds, bile leaks, or adult respiratory distress syndrome occurred. Overall morbidity was 7.1%. Complications included hepatic abscesses in 4 patients, transient liver insufficiency in 3, segmental hepatic infarcts in 2, diaphragm paralysis in 1, hepatic artery-to-portal vein fistula in 1, and systemic hemolysis in 1. CONCLUSIONS: Hepatic RFA is an effective treatment option for patients with unresectable hepatic malignancies. Careful patient selection based on tumor size, location, and number and on patient clinical status should determine the choice of treatment. Further controlled trials are needed to determine the effect of hepatic RFA on long-term survival.     

Renal tumor ablation

PURPOSE OF REVIEW: The management of small renal tumors is changing from radical nephrectomy to nephron-conserving surgery. The aim of this review is to discuss the currently prevailing methods used for nonextirpative renal tumor ablation. The studies published in English during 2004 to May 2005 have been reviewed in this article. RECENT FINDINGS: Of the various ablation techniques, cryotherapy and radiofrequency ablation are being increasingly applied clinically. They can be performed either laparoscopically or percutaneously using a combination of fine probes and high-resolution imaging techniques for focusing and monitoring the therapy. Noninvasive tumor ablation by high-intensity focused ultrasound, and other techniques, is still at an experimental stage. SUMMARY: Although the initial outcomes of cryoablation and radiofrequency ablation are encouraging, long-term studies are necessary to confirm their lasting efficacy. The optimal modality for tumor targeting, monitoring therapy, and follow-up remains to be determined. These ablative techniques should be reserved for carefully selected patients, the data should be prospectively accrued, and the results should be compared to that of the reference standard, open or laparoscopic partial nephrectomy.     

纳米刀消融治疗不可切除肝门部胆管癌的初步探索

目的:分析纳米刀消融治疗不可切除肝门部胆管癌的疗效与难点。方法:回顾性分析2016年1月—2018年6月郑州大学第五附属医院采用纳米刀消融技术治疗的26例不可切除肝门部胆管癌的临床资料。结果:全部患者顺利实施开腹纳米刀消融治疗。4例患者术中放置T管引流,11例术中放置胆道支架,4例术中放置胆道支架+放射性粒子链。8例手术前、后CA19-9均无明显升高;其余18例患者术前CA19-9明显升高,术后第1、3天进一步升高,后逐步下降。术后胆道出血1例,心房颤动2例,上消化道出血死亡1例,胆道感染3例,肝脓肿、腹腔脓肿、淋巴漏各1例,PTCD管脱落4例。22例(84.6%)患者术后胆管再通。26例患者总生存时间平均为(9.8±5.6)个月。结论:纳米刀消融治疗不可切除肝门部胆管癌安全、有效,联合胆道支架治疗可使患者获得更好疗效。     

Laparoscopic in situ ablation of liver cancer with cryotherapy and radiofrequency ablation

BACKGROUND: In situ ablation has potential for the treatment of patients with liver cancer either as a single-modality treatment or in combination with liver resection. METHODS: Laparoscopy and intraoperative ultrasonography was used to target cryotherapy and radiofrequency ablation. Thirty-eight patients with 146 liver lesions were treated between January 1995 and December 2000 using cryotherapy alone (nine patients), combined cryotherapy and radiofrequency (eight), radiofrequency alone (15) and in situ ablation with liver resection (six). Cancers treated were metastases from colorectal tumours (n = 25), hepatocellular carcinoma (n = 5), and neuro endocrine (n = 5), melanoma (n = 2) and renal cell (n = 1) metastases. Complications and survival after in situ ablation were compared with age- and disease-matched controls treated with systemic chemotherapy. RESULTS: The mean age was 61.6 years. At mean follow-up of 26.6 (range 3-62, median 26) months, 22 patients were alive. Survival was increased following in situ ablation compared with that in controls (P < 0.001). Local recurrence at the ablation site was noted in 12 of 44 lesions following cryotherapy and in 20 of 102 lesions after radiofrequency ablation, and new disease in the liver was found in six of 17 and six of 29 patients respectively. The complication rate was higher with cryotherapy than with radiofrequency ablation (four of 17 versus one of 29). Intraoperative ultrasonography identified 14 new hepatic lesions (10 per cent) not seen on preoperative imaging. CONCLUSION: Laparoscopic in situ ablation should include ultrasonography to stage the disease. In situ ablation appears to have a survival benefit and should be considered for the treatment of liver cancer in appropriate patients.     

脾脏毁损体积对射频消融治疗脾脏功能亢进症疗效的影响

目的探讨脾脏毁损体积对射频消融(Radiofrequency Ablation,RFA)治疗肝硬化门脉高压性脾功能亢进症近期疗效的影响。方法对28例肝炎后肝硬化门静脉高压脾功能亢进症患者进行RFA治疗。分别在RFA术后1、7、14、30、60、180、360d,检测外周血WBC、RBC、PLT变化。增强CT测定脾脏毁损体积,根据脾脏毁损体积百分比将患者分成4组:Ⅰ组(<30%)、Ⅱ组(30%~50%)、Ⅲ组(50%~60%),Ⅳ组(>60%),各组间进行对比分析。结果RFA术后WBC、PLT呈明显上升趋势,术后360d与术前比较差异有统计学意义(P<0.01)。脾脏平均毁损体积为(38.20±17.36)%。毁损体积50%~60%组术后360d WBC、PLT较<30%组、30%~50%组及>60%组上升明显(P<0.01)。结论临床上应用射频消融治疗门脉高压性脾功能亢进症的近期疗效肯定。毁损脾脏50%~60%体积近期疗效较好。