Influence of fluorescent dopants on the vat photopolymerization of acrylate-based plastic scintillators for application in neutron/gamma pulse shape discrimination.

Plastic scintillators, a class of solid-state materials used for radiation detection, were additively manufactured with vat photopolymerization. The photopolymer resins consisted of a primary dopant and a secondary dopant dissolved in a bisphenol A ethoxylate diacrylate-based matrix. The absorptive dopants significantly influence important print parameters, for example, secondary dopants decrease the light penetration depth by a factor > 12 ×. The primary dopant 2,5-diphenyloxazole had minimal impact on the printing process even when loaded at 25 % by mass of the resin. Working curve measurements, which relate energy dose to cure depth, were performed as a function of feature size to further assess the influence of dopants. Photopatterns smaller than 150 µm width had apparent increases in critical energy dose compared to larger photopatterns, while all resins maintained printed features in line gratings with 50 µm of separation. Printed scintillator monoliths were compared to scintillators cast by traditional molding, demonstrating that the layer-by-layer printing process does not decrease scintillation response. A maximum light output of 31 % of a benchmark plastic scintillator (EJ-200) and successful pulse shape discrimination were achieved with 20 % by mass 2,5-diphenyloxazole as the primary dopant and 0.1 % by mass 9,9-dimethyl-2,7-distyrylfluorene as the secondary dopant in printed scintillator samples.

Laparoscopic revision of gastric pacing wires.

Currently, electrical stimulation is utilized to treat morbid obesity, gastroparesis, and diaphragmatic paralysis. Although this technology is in its infancy, numerous case reports and small series appear throughout the literature. Furthermore, electrical stimulation is not relegated to only academic centers and tertiary referral centers. As these technologies continue to evolve and alter the treatment of several different pathophysiologic processes, the general surgeon needs to understand the technical aspects of these devices and their potential complications. This paper presents the management of a gastroparetic patient with chronic abdominal pain following the successful placement of gastric pacing wires. A 45-year-old female with idiopathic gastroparesis underwent laparoscopic placement of gastric pacing wires without complications. Four months postoperatively, she presented with chronic left upper quadrant abdominal pain. Her nausea and vomiting had dissipated and she was tolerating a regular diet. Abdominal and pelvic computed tomography (CT) was normal except for the presence of a generator and pacing wires. Ultimately, she required a diagnostic laparoscopy and an upper endoscopy. The upper endoscopy was normal. The diagnostic laparoscopy showed a wide adhesive band from the seromuscular tunnel of the pacing wires to the abdominal wall in the left upper quadrant. The band was lysed and an omental patch was sutured over the insertion site of the wires. On postoperative day 1, the patient was pain-free and discharged home on a regular diet. This case presents an unusual complication of electrical pacing wires. This patient experienced somatic pain due to an adhesive band from her pacing wires to the abdominal wall. Based on the findings of this case, an omental patch was placed on top of the seromuscular electrode tunnel in order to prevent adhesions and potentially persistent abdominal wall pain.

Laparoscopic adrenalectomy: a cost analysis of three approaches.

Laparoscopic adrenalectomy (LA) is the current standard for treatment of benign adrenal disease and is performed more often now in the setting of malignant disease. Three surgical approaches, the lateral transperitoneal technique, the lateral retroperitoneal technique, and the posterior technique are utilized commonly. While advantages of each approach are advocated, a cost analysis is not available. This article analyzes the operating costs of the three approaches. The operative costs of 51 unilateral LA at the Cleveland Clinic Foundation from 1998 to 2002 were analyzed for comparison. Patients were grouped according to one of the three laparoscopic approaches--transperitoneal (group A), lateral retroperitoneal (group B), and posterior (group C). For each group, n=17. Perioperative characteristics and operative cost were analyzed. The groups were compared using single factor ANOVA analysis. Significance was assigned for P<0.05. The average costs of unilateral LA were $2,885, $3,219, and $2,850 for groups A, B, and C, respectively (P=0.20). Differences were not statistically significant. Six bilateral procedures were performed. There were no significant differences for these six cases. However, the cohort was too small for an appropriate power analysis. LA is commonly performed utilizing one of three surgical approaches. Our data demonstrates no significant difference in operative cost between the respective techniques. Operative costs should not be a factor in choosing a laparoscopic approach for unilateral adrenal disease.

Small bowel obstruction after laparoscopic Roux-en-Y gastric bypass.

BACKGROUND: Despite the proliferation of laparoscopic Roux-en-Y gastric bypass (LRYGBP), postoperative bowel obstructions still occur from mesocolonic constrictions, internal hernias, and anastomotic strictures. Obstructed patients do not present with a characteristic history and physical. Therefore, radiographic studies including upper gastrointestinal films and computed tomography are essential for diagnosing these unique obstructive etiologies after LRYGBP. METHODS: From February 2000 to December 2000, 115 patients underwent standard LRYGBP at the Cleveland Clinic Foundation. Retrocolic anastomoses were performed on all patients. Defects at the mesocolon and mesomesentery were closed with interrupted, nonabsorbable sutures. All patients underwent upper gastrointestinal study on the first postoperative day. RESULTS: Six patients developed small bowel obstructions postoperatively. Five of these patients required reexploration. The obstructive etiologies were two mesocolonic constrictions, three internal herniations, and one massive clot at the gastrojejunostomy. Repair of the mesocolonic constrictions involved incising the transverse mesocolon vertically to create a larger window for the Roux limb. Internal herniations were reduced, and defects were reclosed with nonabsorbable sutures. The patient with an obstructive clot was treated endoscopically. CONCLUSIONS: Based on these 6 patients, we have altered our technique to antecolic placement of the Roux limb. This technique requires division of the omentum and additional mobilization of the Roux limb mesentery in order to decrease tension at the gastrojejunostomy. Since initiating these changes and closing all iatrogenic defects, we have not experienced further early small bowel obstructions.

Isolated trans-hiatal colonic herniation.

Isolated herniation of the colon through congenital or traumatic diaphragmatic defects are well documented. However, trans-hiatal herniation of the colon in the absence of an intrathoracic stomach has been reported only once. A 67-year-old man presented with intragastric abdominal pain and a chest x-ray film documenting a posterior mediastinal air-fluid level. Computed tomography showed gastrointestinal contents within the thorax. The findings on an upper gastrointestinal film with small bowel follow-through were normal. Finally, a barium enema identified transverse colon within the thoracic cavity. At laparoscopy, the entire transverse colon was reduced with the hernia sac. The crural defect was repaired, and a Toupet fundoplication was performed. A gastropexy was also added. The patient was discharged on postoperative day 2 able to tolerate a regular diet, and he has been asymptomatic for 5 months. This defect most likely represents a congenital deformity of the diaphragm with intact posterior gastric attachments, including the posterior phrenoesophageal ligament. An intact gastric mesentery enabled isolated colonic herniation with retention of the stomach its normal anatomic position. An antireflux procedure was performed in addition to the crural repair because of the circumferential dissection of the esophagus. This article is the second report of an isolated trans-hiatal herniation of the colon and the first report of laparoscopic repair of this entity.

Gastric electrical-stimulation effects on canine gastric emptying, food intake, and body weight.

OBJECTIVE: It has been reported that electrical stimulation at the distal stomach can disrupt intrinsic gastric electrical activity and delay gastric emptying. Gastric dysrhythmia and impaired gastric emptying are associated with upper gastrointestinal symptoms and weight loss. The purpose of this study was to evaluate the effect of low-frequency/long-pulse gastric electrical stimulation (GES), at proximal and distal stomach, on canine gastric emptying, food intake, and body weight. RESEARCH METHODS AND PROCEDURES: Eight dogs were surgically implanted with four pairs of electrodes along the greater curvature and a gastric tube at the dependent part of the stomach. Liquid gastric emptying at baseline, during proximal and distal GES at 6 cycles per minute, was assessed first by a dye dilution technique. Proximal and distal GES were then randomly delivered during feeding for 10 consecutive days, and food intake and body weight were recorded daily. RESULTS: There was no significant difference in gastric emptying parameters among the various sessions. The mean daily food consumption was significantly reduced during both sessions of GES, resulting in significant immediate weight loss. Percentage weight loss was comparable between both sessions of GES. DISCUSSION: Short-term GES significantly reduced canine food intake and weight. This effect may not be related to changes in gastric emptying. GES may have a potential role in the treatment of obesity.

Laparoscopic small bowel resection of metastatic pulmonary carcinosarcoma.

Carcinosarcoma of the lung is a rare malignancy consisting of both epithelial and mesenchymal components. Although metastatic disease is common, metastatic disease to the small intestine is rare and has been reported only once in the literature. An unusual case of pulmonary carcinosarcoma with metastasis to the small bowel is presented. At the time of laparoscopic exploration, a 4 x 4 cm mass was seen in the jejunum involving the adjacent mesentery. The affected small bowel and mesentery were resected laparoscopically and bowel continuity was restored through an entirely intracorporeal technique. Laparoscopic small bowel resection can be performed safely in the setting of malignant disease and imparts many of the benefits of minimally invasive surgery.

Sphincter of Oddi injection with botulinum toxin is as effective as endobiliary stent in resolving cystic duct leaks in a canine model.

BACKGROUND: Current management of biliary fistulae includes percutaneous drainage and transpapillary endoscopic biliary stent placement. This study compared time to bile leak resolution for endoscopic stent insertion versus injection of botulinum toxin into the sphincter of Oddi. METHODS: Thirty dogs underwent laparotomy and cholecystectomy without cystic duct closure. After a duodenotomy, dogs were randomized to the control group (Group 1) or one of two treatment groups. Treated dogs either underwent transpapillary stent placement (Group 2) or botulinum toxin injection into the sphincter of Oddi (Group 3). Drains were placed adjacent to the cystic duct stump and output was recorded daily. Resolution of bile leaks was defined as an output of less than 10 mL/day. Necropsy was performed to identify undrained intraperitoneal bile. RESULTS: Data from 28 dogs were available for analysis. The numbers of days for resolution of bile leaks in Groups 1, 2, and 3 were, respectively, 9.3 (2.1) days, 2.3 (1.1) days, and 2.6 (1.1) days. There were significant differences in time to resolution of bile leak between Group 1 and both Groups 2 (p < 0.001) and 3 (p < 0.001). There was no significant difference between Groups 2 and 3 (p > 0.25). CONCLUSION: Sphincter of Oddi injection with botulinum toxin is as effective as endobiliary stent placement in resolving cystic duct leaks in this canine model.

Distinct temporal patterns of macrophage-inflammatory protein-2 and KC chemokine gene expression in surgical injury.

In the present study the regulation of CXC chemokine expression was evaluated in full-thickness abdominal wounds in mice. During the first 24 h after injury, IL-1alphabeta, KC, macrophage-inflammatory protein (MIP)-2, and monocyte chemoattractant protein-1 were the predominant cytokines and chemokines produced; TNF-alpha was not detected. Chemokine mRNA expression and protein secretion occurred in two temporal stages. The first, which reached a maximum at 6 h, was associated with high levels of IL-1alpha and KC and low levels of MIP-2. This stage could be reproduced by intradermal injection of IL-1alpha or IL-1beta and was partially blocked by injection of neutralizing Ab against IL-1alpha but not IL-1beta. In animals depleted of circulating neutrophils, chemokine expression was reduced by nearly 70% during this stage. In the second stage, which peaked at 24 h after injury, modest but significant levels of IL-1beta were detected in association with low levels of KC and high levels of MIP-2. This pattern of chemokine expression could not be mimicked by injection of IL-1alpha or IL-1beta (even with prolonged exposure), although MIP-2 expression could be partially inhibited by intradermal injection of neutralizing Ab against IL-1beta. Surprisingly, neutrophil depletion before injury resulted in sustained high levels of both KC and MIP-2 expression. These observations demonstrate that these two closely related chemokines are under distinct regulatory controls in vivo that are likely to reflect the temporally ordered participation of different cell types and/or extracellular stimuli and inhibitors.