Three-dimensional assessment of vascular cooling effects on hepatic microwave ablation in a standardized ex vivo model.

The aim of this study was a three-dimensional analysis of vascular cooling effects on microwave ablation (MWA) in an ex vivo porcine model. A glass tube, placed in parallel to the microwave antenna at distances of 2.5, 5.0 and 10.0 mm (A-V distance), simulated a natural liver vessel. Seven flow rates (0, 1, 2, 5, 10, 100, 500 ml/min) were evaluated. Ablations were segmented into 2 mm slices for a 3D-reconstruction. A qualitative and quantitative analysis was performed. 126 experiments were carried out. Cooling effects occurred in all test series with flow rates ≥ 2 ml/min in the ablation periphery. These cooling effects had no impact on the total ablation volume (p > 0.05) but led to changes in ablation shape at A-V distances of 5.0 mm and 10.0 mm. Contrary, at a A-V distance of 2.5 mm only flow rates of ≥ 10 ml/min led to relevant cooling effects in the ablation centre. These cooling effects influenced the ablation shape, whereas the total ablation volume was reduced only at a maximal flow rate of 500 ml/min (p = 0.002). Relevant cooling effects exist in MWA. They mainly depend on the distance of the vessel to the ablation centre.

Perivascular vital cells in the ablation center after multibipolar radiofrequency ablation in an in vivo porcine model.

Multibipolar radiofrequency ablation (RFA) is an advanced ablation technique for early stage hepatocellular carcinoma and liver metastases. Vessel cooling in multibipolar RFA has not been systematically investigated. The objective of this study was to evaluate the presence of perivascular vital cells within the ablation zone after multibipolar RFA. Multibipolar RFA were performed in domestic pigs in vivo. Three internally cooled bipolar RFA applicators were used simultaneously. Three experimental settings were planned: (1) inter-applicator-distance: 15 mm; (2) inter-applicator-distance: 20 mm; (3) inter-applicator-distance: 20 mm with hepatic inflow occlusion (Pringle maneuver). A vitality staining was used to analyze liver cell vitality around all vessels in the ablation center with a diameter > 0.5 mm histologically. 771 vessels were identified. No vital tissue was seen around 423 out of 429 vessels (98.6%) situated within the central white zone. Vital cells could be observed around major hepatic vessels situated adjacent to the ablation center. Vessel diameter (> 3.0 mm; p < 0.05) and low vessel-to-ablation-center distance (< 0.2 mm; p < 0.05) were identified as risk factors for incomplete ablation adjacent to hepatic vessels. The vast majority of vessels, which were localized in the clinically relevant white zone, showed no vital perivascular cells, regardless of vessel diameter and vessel type. However, there was a risk of incomplete ablation around major hepatic vessels situated directly within the ablation center. A Pringle maneuver could avoid incomplete ablations.

Sacral nerve stimulation in patients with ileal pouch-anal anastomosis.

PURPOSE: Functional results after proctocolectomy and ileal pouch-anal anastomosis (IPAA) are generally good. However, some patients suffer from high stool frequency or fecal incontinence. Sacral nerve stimulation (SNS) may represent a therapeutic alternative in these patients, but little is known about indication and results. The aim of this study was to evaluate incontinence after IPAA and demonstrate SNS feasibility in these patients. METHODS: This retrospective study includes patients who received a SNS between 1993 and 2020 for increased stool frequency or fecal incontinence after proctocolectomy with IPAA for ulcerative colitis. Proctocolectomy was performed in a two- or three-step approach with ileostomy closure as the last step. Demographic, follow-up data and functional results were obtained from the hospital database. RESULTS: SNS was performed in 23 patients. Median follow-up time after SNS was 6.5 years (min. 4.2-max. 8.8). Two patients were lost to follow-up. The median time from ileostomy closure to SNS implantation was 6 years (min. 0.5-max. 14.5). Continence after SNS improved in 16 patients (69%) with a median St. Marks score for anal incontinence of 19 (min. 4-max. 22) before SNS compared to 4 (0-10) after SNS placement (p = 0.012). In seven patients, SNS therapy was not successful. CONCLUSION: SNS implantation improves symptoms in over two-thirds of patients suffering from high stool frequency or fecal incontinence after proctocolectomy with IPAA. Awareness of the beneficial effects of SNS should be increased in physicians involved in the management of these patients.

Influence of interapplicator distance on multibipolar radiofrequency ablation during physiological and interrupted liver perfusion in an in vivo porcine model.

Radiofrequency ablation (RFA) is a curative treatment option for early stage hepatocellular carcinoma (HCC). Vascular inflow occlusion to the liver (Pringle manoeuvre) and multibipolar RFA (mbRFA) represent possibilities to generate large ablations. This study evaluated the impact of different interapplicator distances and a Pringle manoeuvre on ablation area and geometry of mbRFA. 24 mbRFA were planned in porcine livers in vivo. Test series with continuous blood flow had an interapplicator distance of 20 mm and 15 mm, respectively. For a Pringle manoeuvre, interapplicator distance was predefined at 20 mm. After liver dissection, ablation area and geometry were analysed macroscopically and histologically. Confluent and homogenous ablations could be achieved with a Pringle manoeuvre and an interapplicator distance of 15 mm with sustained hepatic blood flow. Ablation geometry was inhomogeneous with an applicator distance of 20 mm with physiological liver perfusion. A Pringle manoeuvre led to a fourfold increase in ablation area in comparison to sustained hepatic blood flow (p < 0.001). Interapplicator distance affects ablation geometry of mbRFA. Strict adherence to the planned applicator distance is advisable under continuous blood flow. The application of a Pringle manoeuvre should be considered when compliance with the interapplicator distance cannot be guaranteed.

Colectomy with ileostomy for severe ulcerative colitis-postoperative complications and risk factors.

PURPOSE: In the era of biological therapy of ulcerative colitis (UC), surgical treatment frequently consists of colectomy, end ileostomy, and rectal stump closure before patients go on towards restorative proctocolectomy. We aimed to evaluate possible risk factors for the occurrence of postoperative complications and investigate those after initial colectomy in these patients. METHODS: Retrospective analysis of 180 patients (76 female, 104 male) undergoing colectomy for UC with formation of a rectal stump and terminal ileostomy between March 2008 and March 2018 at Charité University Hospital Berlin, Campus Benjamin Franklin. A panel of possible postoperative complications was established, patient history was screened, and postoperative complications were analyzed using the Clavien Dindo Classification. RESULTS: Postoperative complication rate was 27.7%. Mortality was 0.5%. Postoperative ileus occurred in 15.3% and rectal stump leakage in 14.8%. Complications were categorized as Clavien Dindo 3 in 80%. Risk factors for surgical complications after multivariate analysis were ASA classification (p = 0.004), preoperative anemia (Hemoglobin < 8 mg/dl) (p = 0.025), use of immunosuppressants (p = 0.003), more than two cardiovascular diseases (p = 0.016), and peritonitis (p = 0.000). Reoperation rate of patients with surgical complications was 27.7%. CONCLUSION: Colectomy in high-risk UC patients is associated with significant morbidity. However, most of the surgical complications can be treated conservatively. Overall mortality is low. Patient-related risk factors are associated with postoperative complications. Optimizing these risk factors or earlier indication for surgery in the course of UC may help to reduce morbidity of this procedure.

[German Society for General and Visceral Surgery (DGAV) risk calculator of interventions for colorectal cancer : Presentation of a surgical algorithm on patient participation and quality assurance]. / DGAV-Risikorechner für Eingriffe beim Kolon- und Rektumkarzinom : Vorstellung eines chirurgischen Algorithmus zur Patientenpartizipation und Qualitätssicherung.

Algorithms are increasingly being developed on the basis of large data sets, also in the field of health, whether for predicting treatment outcomes or life-expectancy. In surgery it is also becoming increasingly more important to analyze complications at an early stage and to subsequently reduce them. The aim is to improve the quality of treatment and quality of life and thus to improve patient well-being. The German Society for General and Visceral Surgery (DGAV) has developed 12 StuDoQ registers in which pseudonymized data from a total of 150,000 patients are recorded. Risk models were developed and validated at the Institute for Medical Information Processing, Biometry and Epidemiology (IBE) of the Ludwig Maximilian University in Munich using the collected data from the StuDoQ|colon cancer and StuDoQ|rectal cancer registers. Based on the collected patient data, the risk calculator determines the statistical probability of the individual complication profile of the patient who is to undergo surgery. The aim is to support surgeons and patients in the decision making process for the individual procedure. The surgeon with his individual experience ultimately remains responsible for the patient.

[Natural orifice transluminal endoscopic surgery in Germany: Data from the German NOTES registry]. / "Natural orifice transluminal endoscopic surgery" in Deutschland : Daten aus dem deutschen NOTES-Register.

BACKGROUND: The German NOTES registry (GNR) was initiated by the German Society for General and Visceral Surgery (DGAV) as a treatment and outcome database for natural orifice transluminal endoscopic surgery (NOTES). AIM: The aim of this study was the descriptive analysis of all GNR data collected over a 5-year period since its start in 2008 with more than 3000 interventions. MATERIAL AND METHODS: The GNR is an online database with voluntary participation available to all German-speaking clinics. Demographic data, therapy details, complications and data on the postoperative course of patients are recorded. All cases in the GNR between March 2008 and November 2013 were included in the analysis. RESULTS: From a total of 3150 data sets 2992 (95 %) were valid and suited for the analysis. Hybrid transvaginal cholecystectomy was the most frequently used procedure (88.7 %), followed by hybrid transvaginal/transgastric appendectomy (6.1 %) and hybrid transvaginal/transrectal colon procedures (5.1 %). Intraoperative complications occurred in 1.6 %, postoperative complications in 3.7 % and conversions were reported in 1.5 %. Intraoperative bladder injuries and postoperative urinary tract infections were identified as method-specific complications of transvaginal procedures. Bowel injuries occurred as a rare (0.2 %) but potentially serious complication of transvaginal operations. CONCLUSION: The German surgical community ensures a safe and responsible introduction of the new NOTES operation techniques with its active participation in the GNR. Despite an overall low complication rate, the high number of procedures in the GNR permitted the identification of method-specific complications. This knowledge can be used to further increase the safety of NOTES in practice.

[Stump closure in laparoscopic appendectomy. Influence of endoloop or linear stapler on patient outcome]. / Stumpfverschluss bei der laparoskopischen Appendektomie. Einfluss der endoskopischen Schlinge oder des Linearstaplers auf das Patientenoutcome.

BACKGROUND: Even though laparoscopic appendectomy is one of the most frequent procedures in abdominal surgery, the technique of appendiceal stump closure is still not standardized. The aim of this retrospective study was to analyze the effect of the use of endoloops or linear staplers for appendiceal stump closure concerning surgical site infections (SSI) and intra-abdominal abscesses (IAA). PATIENTS AND METHODS: All laparoscopic appendectomies between January 1st 2007 and May 31st 2010 were split into an endoloop group (ELG) and a linear stapler group (LSG). The groups were compared with respect to the outcome parameters SSI and IAA. RESULTS: A total of 430 appendectomies were performed in the study period of which 105 operations were conducted laparoscopically. In this study 47.6 % (n = 50) were alloted to the LSG and 52.4 % (n = 55) to ELG. In LSG 3.1 % (n = 1) developed an SSI versus 10.0 % (n = 4, p = 0.254) in ELG. No IAAs occurred in LSG compared to 2 (5.1 %, p = 0.499) in ELG. CONCLUSION: The use of EL for appendiceal stump closure is safe and cost effective for low-grade appendicitis but high-grade appendicitis should be treated with LS.

[Safety of resection of symptomatic and asymptomatic Meckel's diverticulum and literature review]. / Das Meckel-Divertikel: Sicherheit der Resektion symptomatischer und asymptomatischer Befunde und Literaturübersicht.

BACKGROUND: Meckel's diverticulum (MD) is the most common diverticulum of the small bowel and an important finding in surgical practice. The aim of this study was to assess the safety of the resection of symptomatic and asymptomatic MD concerning postoperative complications. As MD are relatively rare, an overview of the literature is given. PATIENTS AND METHODS: All patients with MD at the department at general surgery of the Charité - Campus Benjamin Franklin between 1996 and 2010 were assessed. An analysis for symptomatic and incidental MD was performed for incidence, indication, intraoperative findings, histology and postoperative outcome. RESULTS: An MD was intraoperatively found in 71 of 29 682 patients (0.2 %). Of these, a symptomatic MD occurred in 26 patients (37 %). A symptomatic MD was causal in 6 of 7 patients with gastrointestinal bleeding (GIB, p = 0.005). All symptomatic MD and 30 (67 %) asymptomatic MD were resected. Ectopic gastric mucosa was found significantly more frequently in patients with symptomatic MD (p = 0.001). Patients with asymptomatic MD and resection had less complications as a trend (p = 0.057). CONCLUSION: Ectopic mucosa is more frequent in symptomatic MD, especially in bleeding MD. MD should always be considered in GIB of unknown origin. Resection of incidental MD can be recommended in patients without contraindications such as peritonitis, cancer, ascites or immunosuppression.

[What is the actual benefit of sigmoid resection for acute diverticulitis? : Functional outcome after surgical and conservative treatment]. / Welchen Erfolg bringt die Sigmaresektion bei der akuten Sigmadivertikulitis tatsächlich? : Funktionelle Ergebnisse nach operativer und konservativer Therapie.

INTRODUCTION: The correct therapeutic management of acute sigmoid diverticulitis (SD) is still controversially discussed. Essential to the success of therapy is primarily the long-term resolution of Patient symptoms after surgical or conservative therapy. The aim of this study was to compare the long-term outcome after conservative and surgical treatment of Patients with acute SD. PATIENTS AND METHODS: Consecutive admissions of all Patients with acute SD were prospectively recruited from January 2005 to June 2008 with the exception of a free perforation. The following data were recorded: age, sex, first or recurrent episode of SD, computed tomography (CT) stage, white blood cell count, C-reactive protein, persistent symptoms and recurrence after conservative and surgical therapy. Furthermore, information on the rates of postoperative sexual and bladder dysfunction was collected. The long-term outcome was evaluated by a standardized questionnaire. In June 2008 all Patients were contacted using a standardized questionnaire. RESULTS: A total of 153 Patients were included in the study of whom 70 (45.8  %) presented with the first episode, 83 (54.2  %) had a prior history of SD and 40 Patients were treated conservatively whereas 113 Patients were surgically treated by sigmoid resection. Uncomplicated SD was seen in 16 Patients (conservative 4, surgical 12, p = 0.961), phlegmonous SD was seen in 88 cases (conservative 29, surgical 59, p = 0.026) and covered perforated SD in 49 cases (conservative 7, surgical 42, p = 0.022). The median follow-up was 32 months (range 12-52 months). At follow-up 25  % of conservative and 8.8  % of Patients treated surgically complained about persistent symptoms (p = 0.009). The following symptoms occurred (conservative vs. surgery): painful defecation (22.5  % versus 8.8  %, p = 0.024.), constipation (25  % versus 8.8  %, p = 0.009), abdominal cramp (22.5 % versus 4.4  %, p = 0.001) and painful flatulence (25  % versus 8.8  %, p = 0.009). Sexual or bladder dysfunction occurred postoperatively in 7  % and 9  %, respectively. Of the conservatively treated Patients 32.5  % had a recurrence of SD during follow-up compared to 3.5 % of surgically treated Patients (p < 0.001). CONCLUSIONS: Surgical treatment of acute SD is more effective than conservative therapy for the prophylaxis of recurrent SD and avoidance of persistent symptoms.

Suitability of a virtual reality simulator for laparoscopic skills assessment in a surgical training course.

BACKGROUND: Virtual reality simulators (VRS) can acquire specific performance parameters for laparoscopic surgery. The aim of this study was to evaluate the suitability of a VRS for the assessment in a surgical skills course. MATERIALS AND METHODS: One hundred five attendees of a 7-day surgical skills course were tested with a VRS at the beginning (T1) and at the end (T2) of the course. Two standard VRS tasks (lifting and grasping (LG) and fine dissection (FD)) with two scores and 21 individual parameters were used. VRS performance was correlated to laparoscopic experience and experience in playing video games in order to assess the influence of preexisting skills. RESULTS: The participants improved significantly in both scores and in 19/21 VRS parameters between T1 and T2. Laparoscopic experts were significantly better than novices only for the parameter tissue damage on T1 in LG (41.4 %, P < 0.001). Gamers were significantly better than non-gamers in all manual parameters on T1 in LG. Both groups of laparoscopic experience as well as non-gamers improved between T1 and T2 in LG for most parameters, while gamers only improved for tissue damage. CONCLUSIONS: The VRS was able to assess the gain in surgical performance during the course in general. However, laparoscopic experience and video game experience strongly influenced the results. Laparoscopic experience was correlated to the parameter tissue damage, whereas video game experience was correlated to manual parameters. This knowledge can be used to build adequate scoring systems for VRS and to design tasks that target specific course skills.

[Simulation training in surgical education - application of virtual reality laparoscopic simulators in a surgical skills course]. / Simulationstraining in der Weiterbildung - Einsatz von virtuellen laparoskopischen Operationssimulatoren in einem chirurgischen Trainingskurs.

BACKGROUND: Training and simulation are gaining importance in surgical education. Today, virtual reality surgery simulators provide sophisticated laparoscopic training scenarios and offer detailed assessment methods. This also makes simulators interesting for the application in surgical skills courses. The aim of the current study was to assess the suitability of a virtual surgery simulator for training and assessment in an established surgical training course. MATERIALS AND METHODS: The study was conducted during the annual "Practical Course for Visceral Surgery" (Warnemuende, Germany). 36 of 108 course participants were assigned at random for the study. Training was conducted in 15 sessions over 5 days with 4 identical virtual surgery simulators (LapSim) and 2 standardised training tasks. The simulator measured 16 individual parameters and calculated 2 scores. Questionnaires were used to assess the test persons' laparoscopic experience, their training situation and the acceptance of the simulator training. Data were analysed with non-parametric tests. A subgroup analysis for laparoscopic experience was conducted in order to assess the simulator's construct validity and assessment capabilities. RESULTS: Median age was 32 (27 - 41) years; median professional experience was 3 (1 - 11) years. Typical laparoscopic learning curves with initial significant improvements and a subsequent plateau phase were measured over 5 days. The individual training sessions exhibited a rhythmic variability in the training results. A shorter night's sleep led to a marked drop in performance. The participants' different experience levels could clearly be discriminated ( ≤ 20 vs. > 20 laparoscopic operations; p ≤ 0.001). The questionnaire showed that the majority of the participants had limited training opportunities in their hospitals. The simulator training was very well accepted. However, the participants severely misjudged the real costs of the simulators that were used. CONCLUSIONS: The learning curve on the simulator was successfully mastered during the course. Construct validity could be demonstrated within the course setting. The simulator's assessment system can be of value for the assessment of laparoscopic training performance within surgical skills courses. Acceptance of the simulator training is high. However, simulators are currently too expensive to be used within a large training course.

[Acute sigmoid diverticulitis. Are operations more frequent since the introduction of laparoscopy and CT scanning?]. / Akute Sigmadivertikulitis. Wird seit Einführung der Laparoskopie und CT-Diagnostik häufiger operiert?

INTRODUCTION: Sigmoid resection is now considered as a standard procedure for acute and recurrent sigmoid diverticulitis (SD). In the last decade significant changes in preoperative diagnosis with computed tomography (CT) scanning and surgical access (laparoscopy) have been implemented. The aim of this study was to examine whether this has led to changes in the indications for surgical therapy. PATIENTS AND METHODS: Consecutive admissions of 1,154 patients from January 1995 to December 2009 with acute SD were prospectively included. In terms of pre-operative and intraoperative findings and postoperative course 3 treatment periods (TP) were distinguished: TP I 1995-1999, TP II 2000-2004 and TP III 2005-2009. RESULTS: CT scanning was used in more than 90% of cases since TP II compared to 51% during TP I (p<0.001). The ratio of emergency versus elective surgery significantly increased in favor of elective surgery (p<0.001). The rate of laparoscopy-assisted sigmoid resections showed a continuous increase from 53% in TP I to 71% in TP III (p<0.001) while the rate of Hartmann's procedures decreased over time (p<0.001). Overall, the rate of surgically treated patients decreased during the time periods studied despite an increase in the total number of patients with SD (TP III versus TP I +41%.) The rate of conservatively treated patients increased significantly (p<0.001). The morbidity rate decreased (p<0,001) whereas mortality rates remained at a constantly low level (p=0.175). CONCLUSION: The increasing use of CT diagnosis and the laparoscopic approach led to a shift from emergency surgery with a high complication rate to elective surgery with a high rate of primary restoration of continuity and low morbidity. However, the indications for surgery and therefore the overall rate of patients who underwent surgery did not increase due to these changes.

[Perforation risk and patient age. Risk analysis in acute sigmoid diverticulitis]. / Perforationsrisiko und Patientenalter. Eine Risikoanalyse bei der akuten Sigmadivertikulitis.

INTRODUCTION: It is often postulated that younger patients with acute sigmoid diverticulitis (SD) have an increased risk of perforation which constitutes an indication for early surgery. The aim of this study was to correlate the severity of sigmoid diverticulitis with patient age in order to check the surgical indication in younger patients. PATIENTS AND METHODS: Patients with acute SD from January 1998 to June 2009 were included. Two age groups were distinguished: group I (GI) ≤40 years in age and group II (GII) >40 years. The perforation risk associated with first episode SD was determined by multivariate analysis. SD was classified according to Hansen and Stock (H/S). RESULTS: In the total cohort of 959 patients, including 86 in GI (8.9%) and 873 in GII (91.1%) 468 had a first episode, with 64 in GI (13.7%) and 404 in GII (86.3%). The proportion of first episodes was 74.4% in GI and 46.3% in GII (p<0.001). The perforation risk did not differ (H/S IIb: 29.7% in GI vs. 29.2% in GII, p=0.938; H/S IIc: 25% in GI vs. 25% in GII, p=1). Treatment regimes were (GI vs. GII) emergency operations 25% vs. 25% (p=1), elective operations 17.2% vs. 10% (p=0.096) and conservative treatment 57.8% vs. 64.9% (p=0.276). CONCLUSION: First episodes of SD were more frequent in younger patients (≤40) and did not involve a higher risk of perforation. The indication for treatment of acute SD should not be based on age but on the severity of inflammation and the individual situation of patients.

Fast Estimation of the Vascular Cooling in RFA Based on Numerical Simulation.

We present a novel technique to predict the outcome of an RF ablation, including the vascular cooling effect. The main idea is to separate the problem into a patient independent part, which has to be performed only once for every applicator model and generator setting, and a patient dependent part, which can be performed very fast. The patient independent part fills a look-up table of the cooling effects of blood vessels, depending on the vessel radius and the distance of the RF applicator from the vessel, using a numerical simulation of the ablation process. The patient dependent part, on the other hand, only consists of a number of table look-up processes. The paper presents this main idea, along with the required steps for its implementation. First results of the computation and the related ex-vivo evaluation are presented and discussed. The paper concludes with future extensions and improvements of the approach.

["Practical course for visceral surgery in Warnemünde" 10 years on. Significance and benefits of a surgical training course]. / Zehn Jahre "Praktischer Kurs für Viszeralchirurgie Warnemünde". Bedeutung und Nutzen eines chirurgischen Trainingskurses.

BACKGROUND: Skill courses for surgery offer a good but cost and personnel-intensive possibility to obtain practical and theoretical knowledge by the employment of a close teacher-pupil contact of a large group of surgeons. The goal of the study presented here was to evaluate the satisfaction and benefits of the practical course for visceral surgery in Warnemünde after 10 years of course experience. MATERIAL AND METHODS: All participants in the annual course for visceral surgery were included since 1999. During this 1-week course conventional and laparoscopic exercises are performed under direct guidance of an experienced tutor. The participants are divided into 3 groups based on their surgical experience (e.g. <3 years, 3-5 years, >5 years). All participants received a standardised questionnaire before and after successful course completion for the collection of relevant data (e.g. demography, training, surgical experience and course evaluation). RESULTS: A total of 1,062 participants (435 female, 627 male, mean age 37 years) participated in the course. The average surgical experience of the participants was 5 years. Of the participants 489 came from a hospital of basic medical care, 499 from a hospital of maximum medical care and 74 from a university hospital. Of the participants 96% had no or only little experience with skill courses (1,020 out of 1,065) and 827 participants had no or only few possibilities for training outside of the operation room (78%). The conventional part of the course was evaluated by 77% of the participants as very good and by 50% as very good for the laparoscopic part. Only 8.3% of the participants were willing to finance the costs of the course by themselves. CONCLUSIONS: The practical course for visceral surgery leads to a subjective success in learning. Participation in the course leads to a high satisfaction and offers a cost-intensive possibility for a standardised surgical training. But there are too few experiences with skill courses and possibilities for surgical training outside the operation room so far.

Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation.

PURPOSE: To quantify the cooling effect of hepatic vessels on liver radiofrequency (RF) ablation ex situ. METHODS: Bipolar RF applicators (diameter = 1.8 mm, electrode length = 30 mm) were inserted parallel to perfused glass tubes (diameter = 5 and 10 mm; flow = 250-1,800 ml/min) at distances of 5 and 10 mm in porcine livers ex vivo. RF ablation was performed at 30 W/15 kJ. RF lesions were analyzed by measuring the maximum (r (max)) and minimum radius (r (min)) and the lesion area. RESULTS: Glass tubes without flow showed no influence on RF lesions, whereas perfused glass tubes had a significant cooling effect on lesions. r (min) was reduced to 50% at 5 mm applicator-to-vessel distance and the lesion area was reduced from 407 to 321 mm(2) (p < 0.001). There was no significant influence of glass tube diameter or flow volume on any of the analyzed parameters. CONCLUSIONS: Cooling effects of intrahepatic vessels could be simulated in an ex situ model. Cooling effects should be taken into account in RF ablation within 10 mm distance to major liver vessels regardless of blood flow volume or vessel diameter. Surgical RF ablation with temporary blood flow occlusion should be considered in such constellations.

Improving laser-induced thermotherapy of liver metastases--effects of arterial microembolization and complete blood flow occlusion.

INTRODUCTION: A prerequisite for an oncologically curative application of laser-induced thermotherapy (LITT) of liver metastases is complete tumor destruction. This increased effectiveness was achieved experimentally by combining LITT with interrupted hepatic perfusion. The aim of this study was to evaluate whether an interventional selective arterial microembolization might be as effective as complete blood flow occlusion using an open Pringle's maneuver. PATIENTS AND METHODS: We included patients with unresectable colorectal liver metastases. LITT was performed without interrupted hepatic perfusion (control group) compared to LITT in combination with interrupted perfusion either by embolization of intraarterial degradable starch microspheres (DSM) (percutaneous access) or by complete hepatic inflow occlusion (Pringle's maneuver; open access). Online monitoring was performed using intraoperative ultrasound or MRI. Volumetric techniques were used to assess metastases and postinterventional lesions. RESULTS: Fifty-six patients with 104 metastases (control group (25), DSM (37), and Pringle (42)) were treated. The preinterventional tumor volumes were significantly smaller than the postinterventional lesion volumes (control group: 9.8 vs. 25.3 cm3; DSM: 9.5 vs. 65.4 cm3; Pringle: 12.9 vs. 76.5 cm3). The morbidity rate was 21.4% without treatment-related mortalities. After 6 months follow-up, tumor recurrence was diagnosed in 6 patients (control group (4), LITT with DSM (1), and Pringle (1)). CONCLUSIONS: Combining LITT with blood flow occlusion leads to a significant increase in lesion size. The application of DSM offers a safe and effective alternative to the open access with Pringle's maneuver. Compared to LITT-monotherapy, this modality achieves significantly larger thermal lesions with the need of fewer applications.

Laser-induced thermotherapy: intra- and extralesionary recurrence after incomplete destruction of experimental liver metastasis.

PURPOSE: The aim of this study was to determine the energy (J/mm3 tumor volume) and temperature required for a complete laser-induced thermotherapy (LITT) of experimental liver tumors, and to find out causes and areas of local recurrence followed by incomplete treatment. METHODS: In VX-2 tumor-bearing rabbits LITT was performed using neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) with a diffuser-tip applicator and a temperature feedback system. The animals were randomized into four groups (n = 20) that differed in the target temperature at the tumor border as follows: 45 degrees C, 50 degrees C, 55 degrees C and 60 degrees C. The target temperature was held for 10 min constant. Histologic examination (hematoxylin and eosin [H and E], nicotinamide adenine dinucleotide phosphate [NADPH]-dehydrogenase) was performed at 0 h, 24 h, 96 h, and 14 days after LITT. RESULTS: The pretreatment tumor volume of 2191 +/- 61 mm3 was the same for all groups (p > 0.05). Energy up to target temperature and total energy required, lesion size, and the rate of incomplete tumor ablation (recurrences) are listed below (ap < 0.05, Kruskal-Wallis test). Histologically, two forms of local recurrences could be differentiated intralesionary and extralesionary. CONCLUSIONS: To achieve complete in situ ablation under the given conditions, it is necessary to apply laser energy of 3 J/mm3 tumor volume. A minimum temperature of 60 degrees C on the tumor border presumed an application of 10 min. Recurrence was found outside the coagulation zone (extralesionary) and in high vascularized areas within the coagulation zone (intralesionary).