Proton irradiation of plastic scintillator bars for POLAR-2.

POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42° and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy(corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of ß + decay with a typical for this process gamma-ray energy line of 511 keV.

Proton irradiation of SiPM arrays for POLAR-2.

POLAR-2 is a space-borne polarimeter, built to investigate the polarization of Gamma-Ray Bursts and help elucidate their mechanisms. The instrument is targeted for launch in 2024 or 2025 aboard the China Space Station and is being developed by a collaboration between institutes from Switzerland, Germany, Poland and China. The instrument will orbit at altitudes between 340km and 450km with an inclination of 42 ∘ and will be subjected to background radiation from cosmic rays and solar events. It is therefore pertinent to better understand the performance of sensitive devices under space-like conditions. In this paper we focus on the radiation damage of the silicon photomultiplier arrays S13361-6075NE-04 and S14161-6050HS-04 from Hamamatsu. The S13361 are irradiated with 58MeV protons at several doses up to 4.96Gy, whereas the newer series S14161 are irradiated at doses of 0.254Gy and 2.31Gy. Their respective performance degradation due to radiation damage are discussed. The equivalent exposure time in space for silicon photomultipliers inside POLAR-2 with a dose of 4.96Gy is 62.9years (or 1.78years when disregarding the shielding from the instrument). Primary characteristics of the I-V curves are an increase in the dark current and dark counts, mostly through cross-talk events. Annealing processes at 25 ∘ C were observed but not studied in further detail. Biasing channels while being irradiated have not resulted in any significant impact. Activation analyses showed a dominant contribution of ß + particles around 511 keV. These resulted primarily from copper and carbon, mostly with decay times shorter than the orbital period.

Right-sided vs. left-sided obstructing colonic cancer: results of a multicenter study of the French Surgical Association in 2325 patients and literature review.

PURPOSE: Few studies compared management and outcomes of obstructing colonic cancer (OCC), according to the tumor site. Our aim was to compare patient and tumor characteristics, postoperative and pathological results, and oncological outcomes after emergency management of right-sided vs. left-sided OCC. METHODS: A national cohort study including all consecutive patients managed for OCC from 2000 to 2015 in French surgical centers members of the French National Surgical Association (AFC). RESULTS: During the study period, 2325 patients with OCC were divided in right-sided (n = 819, 35%) and left-sided (n = 1506, 65%) locations. Patients with right-sided OCC were older, more frequently females, and associated with comorbidities, history of cancer, or previous laparotomy. Surgical management was more frequently performed for right-sided than left-sided OCC (99 vs. 96%, p < 0.0001). Tumor resection was more frequently performed in right-sided OCC (95 vs. 90%, p < 0.0001). Among the resected patients, primary anastomosis was more frequently performed in case of right-sided OCC (86 vs. 62%, p < 0.0001). Definitive stoma rate was lower in right-sided location (17 vs. 46%, p < 0.0001). There was no significant difference between locations in terms of cumulative morbidity, anastomotic leak, unplanned reoperation, and mortality. Five-year overall and disease-free survival rates were significantly lower in right-sided OCC (43 and 36%) than in left-sided OCC (53 and 46%, p < 0.0001 and p = 0.001, respectively). CONCLUSIONS: Although patients with right-sided OCC are frailer than left-sided OCC, tumor resection and anastomosis are more frequently performed, without difference in surgical results. However, right-sided OCC is associated with worse prognosis than distal location.

Risk factors for postoperative ileus following elective laparoscopic right colectomy: a retrospective multicentric study.

PURPOSE: Postoperative ileus (POI) is associated with an elevated risk of other complications and increases the economic impact on healthcare services. The aim of this study was to identify pre-, intra- and postoperative risk factors associated with the development of POI following elective laparoscopic right colectomy. METHODS: Between 2004 and 2016, 637 laparoscopic right colectomies were performed. Data were analysed retrospectively thanks to the CLIHMET database. Potential contributing factors were analysed by logistic regression. RESULTS: Patients with POI (n = 113, 17.7%) were compared to those without postoperative ileus (WPOI) (n = 524, 82.3%). In the POI group, there were more men (62 vs 49%; p = 0.012), more use of epidural anaesthesia (19 vs 9%; p = 0.004), more intraoperative blood transfusion requirements (7 vs 3%; p = 0.018) and greater perioperative intravenous fluid administration (2000 vs 1750 mL; p < 0.001). POIs were more frequent when extracorporeal vascular section (20 vs 12%; p = 0.049) and transversal incision for extraction site (34 vs 23%; p = 0.044) were performed. Overall surgical complications in the POI group were significantly greater than in the control group WPOI (31.9 vs 12.0%; p < 0.0001). Multivariate analysis found the following independent POI risk factors: male gender (HR = 2.316, 1.102-4.866), epidural anaesthesia (HR = 2.958, 1.250-6.988) and postoperative blood transfusion requirement (HR = 6.994, 1.550-31.560). CONCLUSIONS: This study is one of the first to explore the CLIHMET database and the first to use it for investigating risk factors for POI development. Modifiable risk factors such as epidural anaesthesia and intraoperative blood transfusion should be used with caution in order to decrease POI rates.

Patients' comorbidities reduce the clinical value of emergency colonoscopy: results of a retrospective cohort study.

BACKGROUND AND STUDY AIMS: Urgent endoscopy is often used to diagnose and sometimes treat acute upper gastrointestinal syndromes (hemorrhage, toxic ingestion, and occlusion). However, its suitability concerning the management of lower gastrointestinal conditions in emergency circumstances is controversial. PATIENTS AND METHODS: We studied the role of emergency colonoscopy in diagnosis and treatment of all consecutive patients presenting with acute lower gastrointestinal symptoms referred to our hospital on an emergency basis. All patients were first managed by physicians from the emergency room and/or the intensive care unit (ICU); the treatments included fluid resuscitation, blood transfusion, and antibiotic or cardiotonic as needed. Bowel cleansing was performed to purge the colon of clots, stool, and blood when clinically possible; alternatively, a bowel enema was used. Patients only underwent a computed tomography (CT) scan prior to the colonoscopy in clinically relevant situations. Colonoscopy was performed within 6 - 36 hours after hospitalization or the beginning of the clinical symptoms (hemorrhage, sepsis, colon distension) or occlusion, as assessed by abdominal CT scan. RESULTS: From 2010 to 2015, 603 patients underwent urgent colonoscopy; among them, 214 (36 %) presented with lower GI bleeding, while 264 (44 %) had symptoms suggestive of intestinal ischemia; almost half (49 %, n = 295) of the patients were hospitalized in the ICU. Patients received therapies, such as clips (15 %), epinephrine injections (5 %), bipolar coagulation (7 %), or devolvulation (3 %) using colonoscopy or antibiotic therapy when needed. No perforation was observed after colonoscopy and only three cases of hemorrhage recurrence were documented as complications after the procedure. Overall, 192 patients died within 1 month after colonoscopy due to four independent risk situations, as follows: septic shock, heart transplantation, multiorgan failure, and ischemic colitis. Only 67 (35 %) underwent urgent intestinal surgery when ischemic colitis was identified, and this did not have a significant effect on the mortality rate. CONCLUSIONS: Urgent bedside colonoscopy is feasible and safe for routine use. The highest advantage was observed in patients with red blood hemorrhage, diarrhea, and colon distension when symptoms were not associated with multiorgane failure, heart transplantation, or septic shock. As revealed by colonoscopy and pathological features, ischemic colitis is associated with a bad prognosis, and patients experience a higher rate of early mortality regardless of whether they undergo urgent colon surgery.