R. Rea

EUS-guided Nd:YAG laser ablation of normal pancreatic tissue: a pilot study in a pig model.

BACKGROUND Laser ablation with a neodymium:yttrium aluminum garnet (Nd:YAG) laser can achieve a high rate of complete tissue necrosis and has been applied as a minimally invasive, palliative option in hepatocellular carcinoma, liver metastasis in colorectal cancer, and malignant thyroid nodules. OBJECTIVE To assess the in vivo feasibility of EUS-guided laser ablation with an Nd:YAG laser of normal pancreatic tissue of a porcine model. DESIGN Prospective investigation. SETTING Hospital animal laboratory. SUBJECTS Eight pigs. INTERVENTIONS EUS-guided puncture of the pancreatic tail with a laser-beam fiber. An Nd:YAG laser (1.064 nm) was used, with an output power of 2 and 3 W and a total delivered energy of 500 and 1000 J in continuous mode. MAIN OUTCOME MEASUREMENTS The 24-hour follow-up of the pigs was focused on clinical and laboratory aspects. Results of histological studies of the pancreas were obtained 24 hours after the procedure on necroscopy tissue. RESULTS There were no technical limitations to the performance of the procedure. Tissue necrosis, localized in the pancreatic parenchyma, was observed in all animals on histological examination. The volume of ablation tissue ranged from a mean of 314 mm(3) to 483 mm(3). The ablation area ranged from a mean of 49 mm(2) to 80 mm(2). No major postprocedure complications were recorded, and all the pigs survived at 24 hours. LIMITATION Animal study. CONCLUSIONS EUS-guided laser ablation of the pancreas with an Nd:YAG laser is feasible in a porcine model.

EUS-guided Nd:YAG laser ablation of a hepatocellular carcinoma in the caudate lobe

Vascular liverinjuries and portobiliary fistulas related to biliary proceduresappear to be a more recognized complication of percutane-ous biliary drainage rather than ERCP. However, this casereport illustrates that if the apparent biliary anatomy looksunusual, particularly if radiographic contrast material washesout from the biliary tree, then entry into the portal vein haslikely occurred, a diagnosis of portobiliary fistula should beconsidered, and stent placement should take place only withcaution. As in this case, if a stent has been placed previously,then further stenting may be needed to occlude the fistula. Inthe occurrence of a portobiliary fistula, biliary stenting viaeither ERCP or percutaneous transhepatic cholangiographyoffers an opportunity to prevent significant hemorrhage andpotential portal sepsis.

Laser Interstitial Thermotherapy for pancreatic tumor ablation: Theoretical model and experimental validation

This study aims to develop and verify a theoretical model to reproduce the thermal response of pancreatic tissue undergone Laser Induced Interstitial Thermotherapy (LITT). The model provides the evaluation of: a) ablated volumes induced by thermal ablation; b) tissue response time to irradiation; and c) heat extinction time. Theoretical volume values were compared with ex vivo healthy tissue and in vivo healthy and neoplastic tissue volume values. The theoretical model takes into account the differences between healthy and neoplastic tissue due to blood perfusion. Mathematical model shows that ablated volume of ex vivo healthy tissue is greater than in vivo one after the same treatment. Moreover, ablated neoplastic in vivo tissue volume is greater than healthy in vivo one, because of tumour angiogenesis. Ablated volume values were compared with experimental data obtained by laser treatment of 30 ex vivo porcine pancreases. Experimental ablated volume values show a good agreement with theoretical values, with an estimated increase of 61% when power increases from 3 W to 6 W, versus 46% of experimental data, and an estimated increase of 14% from 6 W to 10 W, versus 21% of experimental values. LITT could be an alternative or a neo-adjuvant treatment to surgical resection for pancreas cancer removal, and the proposed model could be the basis to supervising the evolution of ablated volumes during tumor treatment.

US-guided application of Nd:YAG laser in porcine pancreatic tissue: an ex vivo study and numerical simulation

BACKGROUND Laser ablation (LA) with a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser is a minimally invasive approach able to achieve a high rate of complete tissue necrosis. In a previous study we described the feasibility of EUS-guided Nd:YAG pancreas LA performed in vivo in a porcine model. OBJECTIVE To establish the best laser setting of Nd:YAG lasers for pancreatic tissue ablation. A secondary aim was to investigate the prediction capability of a mathematical model on ablation volume. DESIGN Ex vivo animal study. SETTING Hospital animal laboratory. SUBJECTS Explanted pancreatic glands from 60 healthy farm pigs. INTERVENTION Laser output powers (OP) of 1.5, 3, 6, 10, 15, and 20 W were supplied. Ten trials for each OP were performed under US guidance on ex vivo healthy porcine pancreatic tissue. MAIN OUTCOME MEASUREMENTS Ablation volume (Va) and central carbonization volume (Vc) were measured on histologic specimens as the sum of the lesion areas multiplied by the thickness of each slide. The theoretical model of the laser-tissue interaction was based on the Pennes equation. RESULTS A circumscribed ablation zone was observed in all histologic specimens. Va values grow with the increase of the OP up to 10 W and reach a plateau between 10 and 20 W. The trend of Vc values rises constantly until 20 W. The theoretical model shows a good agreement with experimental Va and Vc for OP between 1.5 and 10 W. LIMITATIONS Ex vivo study. CONCLUSION Volumes recorded suggest that the best laser OP could be the lowest one to obtain similar Va with smaller Vc in order to avoid the risk of thermal injury to the surrounding tissue. The good agreement between the two models demonstrates the prediction capability of the theoretical model on laser-induced ablation volume in an ex vivo animal model and supports its potential use for estimating the ablation size at different laser OPs.

Endoscopic full-thickness resection of superficial colorectal neoplasms using a new over-the-scope clip system: A single-centre study

BACKGROUND AND AIM Endoscopic full-thickness resection (EFTR) provides complete en-bloc resection with a histopathological evaluation of submucosal, muscular, and serosal layers. The aim of this study was to investigate the efficacy and safety of a novel over-the-scope device for colorectal EFTR. MATERIAL AND METHODS In this retrospective, observational, open-label case study, a total of 20 patients with superficial colorectal neoplasms, underwent EFTR using a new endoscopic full-thickness resection device (FTRD; Ovesco Endoscopy, Tübingen, Germany). Endoscopic treatment outcomes (technical success, rate of EFTR, adverse events) and early follow-up at three months, were analyzed. RESULTS We reported a 100% of technical success, defined as full-thickness resection. Among the R1 resections, histology was negative for neoplasm. Non-lifting adenomas had histology positive for adenocarcinoma: seven T1/G1/sm1; one T1/G1/sm2; one, who underwent a surgical resection, T1/G1/sm3. Mean size of the resected lesions was 26mm, ranging from 10 to 42mm. One (5%) patient developed abdominal pain, fever and leukocytosis and was treated conservatively with medical therapy. In all specimens, histological complete resection was confirmed. CONCLUSIONS EFTR is a feasible and effective technique that could become a valid alternative to EMR and ESD in the management of recurrent adenomas, no-lifting lesions and scars of R1 resections. However, prospective studies are needed to further evaluate the device and technique.

Theoretical assessment of principal factors influencing laser interstitial thermotherapy outcomes on pancreas

The influence of some therapy-relevant parameters on Laser Induced Interstitial Thermotherapy (LITT) outcomes on pancreas is assessed. The aim is to execute a sensitivity analysis for an optimal treatment strategy on in vivo pancreas. A numerical model based on Bioheat Equation has been implemented to assess the influence of laser settings (power P and energy E), applicator radius (rf) and optical properties (effective attenuation coefficient, μeff) on temperature (T) distribution. Effects on pancreas undergoing LITT have been evaluated with a twofold approach: 1) T rise and maximum T (Tmax) in tissue; 2) injured volumes (vaporized and coagulated ones). We consider parameters range in typical LITT values (P from 1.5 W to 6 W, E from 500 J to 1500 J, rf from 150 μm to 600 μm) and optical values reported in literature. Our analysis shows that, among others, P and μeff are the principal influencing factors of thermal effects on pancreas undergoing LITT: P should be carefully chosen by operator to obtain the desired injured volumes, while the accurate measurement of tissue optical properties is crucial to carry out a safe and controlled thermal therapy on pancreas.

P.03.9 FEASIBILITY OF EUS-GUIDE ND: YAG LASER ABLATION OF THE HEPATOCELLULAR CARCINOMA

Background and aim: We previously described a case of EUS-guided Nd:YAG (neodymium:yttrium-aluminium-garnet) LA of a HCC lesion located into the caudate lobe, not suitable for percutaneous approach. Aim is to confirm the feasibility of EUS-guided Nd:YAG LA of HCC in unsafe conditions for the percutaneous approach. Material and methods: Treatment was performed in 2 patients with multifocal HCC unsuitable for surgical resection or liver transplant. First one was affected by criptogenetic liver cirrhosis Child-Pugh A6 and lesion was site in the caudate lobe with huge ombelical vein and portal hypertension. The location of the lesion and the difficult ultrasonography visualization precluded percutaneous treatment. Second patient was affected by HCV and HIV cirrhosis Child-Pugh B9 with ascites and portal hypertension. Both patients underwent previous failed transarterial embolization (TACE) and RFA of lesions located into segment 1 and 3 respectively. Trans-gastric EUS-puncture was performed using a 22-gauge needle following the application of Doppler. A Nd:YAG laser with a wavelength of 1.064 nm was used. As previously described the treatment was planned taking into account the baseline volume of the lesions at EUS and the volume of necrosis that could be achieved in relation to the energy delivered. Results: Lesions were easier targeting through the lesser gastric curve. Application of Nd:YAG LA did not have any negative effect on the quality of the EUS images during the treatment and the whole treated area was occupied by an irregular and poorly defined echogenic zone at the end. The patients didn’t report any pain or abdominal discomfort after treatment and were discharged on the third postoperative day without complications. CT performed 24 hours after procedure showed the whole treated area replaced by an homogeneous, hypoattenuating, nonenhancing area. At 2 months follow-up clinical examination and blood analysis tests were normal. CT-scan showed uniform hypoattenuation without enhancement in the ablated zone and confirm the success to ablate the entire lesion. Conclusions: EUS-guided Nd:YAG LA of a HCC is feasible and safe in lesions in which the percutaneous approach is unsure. This promising results need to be confirmed in additional patients with lesions difficult to reach by conventional ablative methods or in patients whit compromised clinical conditions.