Changes in Local Hepatic Blood Perfusion During Interstitial Laser-Induced Thermotherapy of Normal Rat Liver Measured by Interstitial Laser Doppler Flowmetry

Interstitial laser Doppler flowmetry was used to measure the effect of interstitial laser-induced thermotherapy on local blood perfusion in normal rat liver in the peripheral treatment region elevated to hyperthermic temperatures. The Nd:YAG laser emitting at 1064 nm was utilised as heat generation source. The plane-cut tip of an optical fibre was placed in the middle of the exteriorised left liver lobe. Blood perfusion and temperature were measured in the liver parenchyma 4 mm from the laser fibre. The temperature at the location of the liver temperature sensor was maintained at 41 or 44°C during 30 min by regulating the power of the heating laser. The laser Doppler signal was recorded during and after heat treatment, for a total time of 60 min. At 41°C, a significant increase in perfusion up to 1.3 times the initial value was observed 2–16 min after start of treatment. At 44°C, perfusion decreased continuously during and after treatment, and was significantly different from control 40 min after start of treatment. The results may be valuable in assessing the thermal response of tissues surrounding the target in interstitial laser-induced thermotherapy of liver tumours during conditions of normal blood flow. Paper received 28 September 1998; accepted after revision 24 November 1998.     

Synergistic Effect of Interstitial Laser Coagulation and Doxorubicin in a Murine Tumor Recurrence Model of Solitary Colorectal Liver Metastasis

Background Interstitial laser coagulation (ILC) is gaining acceptance for treatment of unresectable colorectal liver metastases. However, local recurrence rates are still high. To overcome this problem, we investigated the potential of additional systemic therapy after ILC in a murine model. Methods Single C26 colon carcinoma nodules (∼1 mm³) expressing firefly luciferase were implanted in the left liver lobe of 32 BALB/c mice. Seven days after implantation, tumors were treated with either ILC alone (neodymium–yttrium aluminum garnet; 6 W/cm; 800 J/cm) or ILC followed by 1 mg/kg of doxorubicin intravenously. Controls received either doxorubicin alone or sham treatment. Tumor load was measured by in vivo bioluminescent imaging. Results Solitary colorectal liver metastases developed over 7 days after tumor implantation in the liver. Extrahepatic disease was not observed. The ILC dose was set to ablate the liver metastases with recurrent tumor growth in 9 of 16 mice after 7 days. After ILC plus doxorubicin, complete tumor destruction occurred without recurrence (0 of 14). Sham treatment or treatment with doxorubicin alone showed an exponential increase in tumor load. Conclusions A murine tumor recurrence model after local ablative treatment of solitary liver metastasis was developed. The combination of ILC and doxorubicin had a strong synergistic effect that led to complete tumor remission in all animals treated.     

Preserving the Integrity of Oesophageal Stents with Laser Therapy and Argon Plasma Coagulation: An In Vitro Study

. Thermal lasers and argon plasma coagulation are widely used in the treatment of stent overgrowth in patients with advanced oesophageal malignancy. The aim of treatment is to achieve patency while avoiding damage to the prosthesis. This experimental study was designed to determine the power and duration of application that can be safely tolerated by four different types of oesophageal prostheses. Five stents were studied: wall stent; open metal mesh stent (uncovered Ultraflex); covered metal mesh stent (covered Ultraflex); Gianturco (Z-stent); Esophagocoil. Nd-YAG Laser, GaAlAs diode laser and argon plasma coagulation were applied in non-contact mode at gradually increasing power levels and duration and the effects were observed. The use of argon plasma coagulation on Esophagocoil stent seems safe in power settings of 100 W up to 10 s. The diode laser is intermediate in that Gianturco and Esophagocoil stents can withstand pulses of up to 50 W for about 2 s. The Nd-YAG laser is detrimental to most stents at power levels of 20 W. Only the Esophagocoil withstands Nd-YAG pulses of 60 W but only up to 1 s. Wallstent, open and membrane-covered mesh stents perform poorly in that they can only tolerate up to 1.5 s of power at 25 W with the Diode and 1.0 s of power at 20 W with Nd-YAG laser. The use of different thermal modalities on the five stents has indicated safe power limits and duration. Membrane-covered stents are always damaged by thermal laser application unless the membrane is truly transparent. Paper received 23 February 2000; accepted after revision 24 March 2000.     

Experimental Study of Different Laser Systems for PMMA Extraction Within the Scope of Revision Hip Arthroplasty

. Cement removal at revision hip arthroplasty forms a critical step for a successful operation. The removal of polymethymethacrylate (PMMA) with curet and chisel can cause major damage to the femoral shaft. The use of ultrasound or lithotripsy can cause perforation and microfractures to bone tissue. The goal of our study was to evaluate the application and practicability of different laser systems for cement removal. We examined and compared the effects of a diode laser (wavelength λ=800 nm), a Nd:YAG laser (λ=1064 nm), and an Er:YSSG laser (λ=2780 nm) on PMMA and the PMMA–bone interface. Whereas the Nd:YAG laser with a high ablation rate led to severe bone damage with extensive carbonisation, the Er:YSSG laser with a low ablation rate produced a defined cut at the PMMA–bone interface (max. depth 3.70 mm at 6.0 W laser power). Using the diode laser a defined high quality ablation of PMMA at the PMMA–bone interface was possible without any visible damage of adjacent tissue (max. depth 2.75 mm at 2.9 W laser power). However, sufficient ablation in an adequate operating time could not be realised with this power. The use of a laser tool for cement removal is insufficient. It only facilitated the manual removal of the remaining cement with chisel and curet. Paper received 5 November 1999; accepted after revision 27 April 2000.     

微创经皮肾钬激光碎石取石术治疗复杂性肾结石（附218例报告）

目的：提高复杂性肾结石的治愈率,降低残石率,减少并发症和手术创伤。方法：回顾分析218例复杂性肾结石患者采用微创经皮肾钬激光碎石取石术（MPCNL术）治疗的临床资料。左侧复杂性肾结石96例,右侧90例,双侧32例,孤立肾或对侧肾功能丧失患者37例,合并肾功能不全氮质血症54例。结果：218例患者全部治愈。15例残余少许肾盏内小结石,未发生因并发症导致肾丢失,无死亡病例。结论：经皮肾钬激光碎石取石术具有微创、出血少、恢复快等优点。充分的术前评估及准备、娴熟的手术技巧、完善的术后处理是取得手术成功,减少术后并发症的关键。     

An Atlas of Optical Coherence Tomography (OCT): Elucidating In Vivo Differences of Scar Types Using OCT in Order to Guide Laser Treatment Parameters

ObjectiveWhen using laser therapy to effectively treat scars, the choice of treatment parameters depends on the knowledge accuracy of the underlying scar pathology, which is often difficult to judge by gross physical exam. As such, more quantitative measures are needed. In recent years, optical coherencetomography (OCT) has shown promise as a real-time imaging technolgoy of skin microstructure. A key step in developing a methodology for utilizing OCT to develop a comprehensive ‘atlas’ of OCT characteristics of a wide variety of scar types. This atlas may then be used as a tool for selecting the optimal treatment modality and parameters for each scar type.MethodsOne hundred and fifty scars of a wide range of anatomical locations were imaged using OCT, capturing both vascular and structural data. A variety of scar etiologies (e.g. burn, surgical, traumatic) and types (e.g. hypertrophic, keloidal, atrophic) were included. Comparator scans were also taken from normal, unscarred skin.ResultsOCT revealed morphological differences in the epidermis and dermis between scars and normal tissue, and between scar subtypes. Features affected by scar pathology included epidermal thickness, skin surface texture, dermal epidermal junction rugosity, blood vessel density, vessel shape and diameter, vessel direction and vascular network, dermis scattering intensity and non-uniformity. Each scar subtype showed consistent characteristics distinct from other scar subtypes.LimitationsThis was a single-site study of a patient population in South Florida.ConclusionOCT is a powerful new objective tool for the clinician to utilize in the pursuit of effective laser treatment parameters by enabling personalized treatment based on individual scar characteristics in order to maximize treatment capabilities.     

Mortality Risk Factors Among Patients With Cirrhosis and a Low Model for End‐Stage Liver Disease Sodium Score (≤15): An Analysis of Liver Transplant Allocation Policy Using Aggregated Electronic Health Record Data

Although the Model for End‐Stage Liver Disease sodium (MELD Na) score is now used for liver transplant allocation in the United States, mortality prediction may be underestimated by the score. Using aggregated electronic health record data from 7834 adult patients with cirrhosis, we determined whether the cause of cirrhosis or cirrhosis complications was associated with an increased risk of death among patients with a MELD Na score ≤15 and whether patients with the greatest risk of death could benefit from liver transplantation (LT). Over median follow‐up of 2.3 years, 3715 patients had a maximum MELD Na score ≤15. Overall, 3.4% were waitlisted for LT. Severe hypoalbuminemia, hepatorenal syndrome, and hepatic hydrothorax conferred the greatest risk of death independent of MELD Na score with 1‐year predicted mortality >14%. Approximately 10% possessed these risk factors. Of these high‐risk patients, only 4% were waitlisted for LT, despite no difference in nonliver comorbidities between waitlisted patients and those not listed. In addition, risk factors for death among waitlisted patients were the same as those for patients not waitlisted, although the effect of malnutrition was significantly greater for waitlisted patients (hazard ratio 8.65 [95% CI 2.57–29.11] vs. 1.47 [95% CI 1.08–1.98]). Using the MELD Na score for allocation may continue to limit access to LT.