Factors affecting tumor ablation during high intensity focused ultrasound treatment.

BACKGROUND/AIMS: High intensity focused ultrasound (HIFU) utilizes a targeted extracorporeal focused ultrasound beam to ablate neoplastic pancreatic tissue. We used an in vitro model to examine the effects of bone, metallic stents, plastic stents, metal plates, and cyst-like lesions on HIFU treatment. METHODS: HIFU was delivered to the phantom models implanted with foreign bodies, and the location, shape, and size of the ablated zones were evaluated. RESULTS: Bone and metallic plates reflected the ultrasound beam, shifting the ablation zone from the focal zone to the prefocal area. In the phantoms containing metal stent, plastic stent, and cyst, most of the ablative energy was reflected to the prefocal area by the surface, with the remainder penetrating through the phantom. The area of the ablated margins was significantly larger in size and volume than the intended focal ablation zone. CONCLUSIONS: During HIFU therapy, artificial or anatomical barriers could affect the direction of the ultrasound beams, shifting the ablation zone from the focal area to a prefocal site with a larger than expected ablation zone. These factors should be considered prior to HIFU treatment for pancreatic tumors because they could limit ablation success, in addition to causing complications.

Systemic effect of endoscopic ultrasonography-guided pancreatic cyst ablation with ethanol and paclitaxel.

BACKGROUND: Endoscopic ultrasonography (EUS)-guided pancreatic cyst ablation is a minimally invasive treatment modality. Local injection of ablative agents may rarely cause systemic effects in patients. AIMS: This study aimed to evaluate the systemic effect of ablative agents by analyzing the plasma drug concentration. METHODS: Ten patients with pancreatic cysts were enrolled. Cyst ablation was performed by 99 % ethanol lavage (2.5-70 mL) and paclitaxel (Genexol-polymeric micelle, 6.0-24.0) injection. Blood samples were collected at 0, 2, 4, 7 and 24 h. Plasma paclitaxel concentration was analyzed by a liquid chromatography-tandem mass spectrometry with the lowest limit of quantitation of 0.1 ng/mL. Procedure-related complications were closely monitored. RESULTS: Pancreatic cysts were located at the head in two, body in seven and tail in one patient. Eight cysts were septated. Median diameter and original volume were 39.5 mm (range 2.7-21.8) and 14.79 mL (3.42-343.30). Median cyst fluid CEA and amylase values were 17.10 ng/mL (0.5-14127.5) and 73.50 U/L (3.1-91,590). Peak plasma paclitaxel concentration values were observed between 2 and 7 h, ranging from 0.45 to 14.73 ng/mL. The highest concentration (17.10 ng/mL at 0 h) was observed in a patient who had intracystic bleeding. Mild abdominal pain occurred in five patients and vomiting in one patient during the first 48-h monitoring. CONCLUSION: Plasma paclitaxel concentration after EUS-guided pancreatic cyst ablation was nearly as low as the undetectable value and rarely caused systemic side-effect.

Forward-viewing endoscopic ultrasound-guided NOTES interventions: a study on peritoneoscopic potential.

AIM: To evaluate the feasibility of diagnostic and therapeutic transgastric (TG) peritoneoscopic interventions with a forward-viewing endoscopic ultrasound (FV-EUS). METHODS: This prospective endoscopic experimental study used an animal model. Combined TG peritoneoscopic interventions and EUS examination of the intra-abdominal organs were performed using an FV-EUS on 10 animal models (1 porcine and 9 canine). The procedures carried out include EUS evaluation and endoscopic biopsy of intraperitoneal organs, EUS-guided fine needle aspiration (EUS-FNA), EUS-guided radiofrequency ablation (EUS-RFA), and argon plasma coagulation (APC) for hemostatic control. The animals were kept alive for 7 d, and then necropsy was performed to evaluate results and complications. RESULTS: In all 10 animals, TG peritoneoscopy, followed by endoscopic biopsy for the liver, spleen, abdominal wall, and omentum, was performed successfully. APC helped control minor bleeding. Visualization of intra-abdominal solid organs with real-time EUS was accomplished with ease. Intraperitoneal EUS-FNA was successfully performed on the liver, spleen, and kidney. Similarly, a successful outcome was achieved with EUS-RFA of the hepatic parenchyma. No adverse events were recorded during the study. CONCLUSION: Peritoneoscopic natural orifice transluminal endoscopic surgery (NOTES) interventions through FV-EUS were feasible in providing evaluation and performing endoscopic procedures. It promises potential as a platform for future EUS-based NOTES.

Endoscopic gastrojejunostomy with a natural orifice transluminal endoscopic surgery technique.

AIM: To determine the technical feasibility and safety of an endoscopic gastrojejunostomy with a pure natural orifice transluminal endoscopic surgery (NOTES) technique using a T-anchoring device in a porcine survival model. METHODS: An endoscopic gastrojejunostomy with a pure NOTES technique using a T-anchoring device was performed on 10 healthy female minipigs weighing approximately 40 kg each under general anesthesia. All procedures were performed with a transgastric approach using a 2-channel therapeutic endoscope. RESULTS: The transgastric gastrojejunostomy was technically successful in all cases. A total of four to six stitched pairs of a T-anchoring device were used to secure the anastomosis. The median time required to enter the peritoneal cavity and pull the small bowel into the stomach was 34 min (range: 19-41 min); the median time required to suture the anastomosis was 67 min (range: 44-78 min). An obstruction of the efferent limb occurred in one case, and a rupture of the anastomosis site occurred in another case. As a result, the functional success rate was 80% (8/10). Small bowel adhesion to the stomach and liver occurred in one case, but the anastomosis was intact without leakage or obstruction. CONCLUSION: A transgastric gastrojejunostomy with a T-anchoring device may be safe and technically feasible. A T-anchoring device may provide a simple and effective endoscopic suturing method.

The Performance of Multiple Transgastric Procedures Using the Natural Orifice Transluminal Endoscopic Surgery Technique: Is Pure NOTES Satisfactory?

BACKGROUND/AIMS: Although several groups have demonstrated the usefulness of natural orifice transluminal endoscopic surgery (NOTES), there is still concern about frequent serious adverse events. We performed this study to determine the technical feasibility and safety of pure NOTES with a transgastric approach in a porcine model from the endoscopist's point of view. METHODS: Diagnostic peritoneoscopy, liver biopsy, salpingo-oophorectomy, and Fallopian tube ligation with a transgastric approach using a two-channel therapeutic endoscope were performed in 10 healthy female minipigs. These procedures were performed in two acute models and eight survival models in consecutive order. RESULTS: The technical success rate was 100% for peritoneoscopy (10/10), liver biopsy (5/5), salpingo-oophorectomy (10/10), and Fallopian tube ligation (10/10). Eight cases of adverse events occurred, including one case of splenic injury, one case of bleeding after liver biopsy, two cases of small bowel adhesion after salpingo-oophorectomy, two cases of hematoma at the salphingo-oophorectomy site, and two cases of partial dehiscence at the gastric closure site. The gastric puncture site was closed with seven to eight hemoclips in four cases and two hemoclips and an endoloop in four cases. CONCLUSIONS: The use of pure NOTES for peritoneoscopy, liver biopsy, salpingo-oophorectomy, and Fallopian tube ligation may be technically feasible, but considerable adverse events can occur during or after the procedure. Further studies utilizing specialized techniques overcome several limitations of pure NOTES are therefore necessary.

EUS-guided radiofrequency ablation of the porcine pancreas.

BACKGROUND: EUS-guided radiofrequency ablation (EUS-RFA) could be used as an adjunct and effective alternative mode of treatment for unresectable locally advanced and nonmetastatic pancreatic adenocarcinoma. However, its translation into clinical practice has been restricted because of limited data and high procedure-related risk. OBJECTIVE: To evaluate the feasibility, efficacy, and safety of EUS-RFA in the normal porcine pancreas. DESIGN: Prospective, endoscopic, experimental study in a porcine model. SETTING: Tertiary-care referral center animal laboratory. PATIENTS: Animal study. INTERVENTION: EUS-RFA of the pancreas was attempted on 10 adult mini pigs. An 18-gauge endoscopic RFA electrode was used to puncture the body and tail of the pancreas, with an output power of 50 W for 5 minutes. MAIN OUTCOME MEASUREMENTS: The feasibility, efficacy, and safety of EUS-RFA. RESULTS: A spherical necrotic lesion surrounded by fibrous tissue localized in the pancreatic parenchyma was observed on histopathologic examination. The mean diameter of the ablated tissue was 23.0 ± 6.9 mm. No major procedure-related complications were noted, and all pigs survived without any distress behavioral pattern for 7 days until autopsy. LIMITATIONS: Small sample size with short-term observation and the lack of evaluation of the head of the pancreas. CONCLUSION: EUS-RFA of the pancreatic body and tail was feasible, effective, and relatively safe in a porcine model. More animal studies to assess damage to adjacent organs are required before human trials can be conducted.