Secondary proton buildup in space radiation shielding.

The risk posed by prolonged exposure to space radiation represents a significant obstacle to long-duration human space exploration. Of the ion species present in the galactic cosmic ray spectrum, relativistic protons are the most abundant and as such are a relevant point of interest with regard to the radiation protection of space crews involved in future long-term missions to the Moon, Mars, and beyond. This work compared the shielding effectiveness of a number of standard and composite materials relevant to the design and development of future spacecraft or planetary surface habitats. Absorbed dose was measured using Al2O3:C optically stimulated luminescence dosimeters behind shielding targets of varying composition and depth using the 1 GeV nominal energy proton beam available at the NASA Space Radiation Laboratory at the Brookhaven National Laboratory in New York. Absorbed dose scored from computer simulations performed using the multi-purpose Monte Carlo radiation transport code FLUKA agrees well with measurements obtained via the shielding experiments. All shielding materials tested and modeled in this study were unable to reduce absorbed dose below that measured by the (unshielded) front detector, even after depths as large as 30 g/cm2. These results could be noteworthy given the broad range of proton energies present in the galactic cosmic ray spectrum, and the potential health and safety hazard such space radiation could represent to future human space exploration.

Profile of and risk factors for early unplanned readmissions in patients with acute necrotizing pancreatitis.

INTRODUCTION: Acute necrotizing pancreatitis (ANP) complicates up to 15% of acute pancreatitis cases. ANP has historically been associated with a significant risk for readmission, but there are currently no studies exploring factors that associate with risk for unplanned, early (<30-day) readmissions in this patient population. METHODS: We performed a retrospective review of all consecutive patients presenting to hospitals in the Indiana University (IU) Health system with pancreatic necrosis between December 2016 and June 2020. Patients younger than 18 years of age, without confirmed pancreatic necrosis and those that suffered in-hospital mortality were excluded. Logistic regression was performed to identify potential predictors of early readmission in this group of patients. RESULTS: One hundred and sixty-two patients met study criteria. 27.7% of the cohort was readmitted within 30-days of index discharge. The median time to readmission was 10 days (IQR 5-17 days). The most frequent reason for readmission was abdominal pain (75.6%), followed by nausea and vomiting in (35.6%). Discharge to home was associated with 93% lower odds of readmission. We found no additional clinical factors that predicted early readmission. CONCLUSION: Patients with ANP have a significant risk for early (<30 days) readmission. Direct discharge to home, rather than short or long-term rehabilitation facilities, is associated with lower odds of early readmission. Analysis was otherwise negative for independent, clinical predictors of early unplanned readmissions in ANP.

The addition of flexible endoscopic suturing to stenting for the management of transmural esophageal wall defects: a single tertiary center experience.

BACKGROUND AND AIMS: Endoscopic stenting is the standard of care for full thickness esophageal wall defects. The aim of this study is to evaluate outcomes of endoscopic closure of esophageal defects using stenting, with or without endoscopic suturing. METHODS: This is a single-center retrospective study of patients with esophageal wall defects who underwent endoscopic interventions. Outcomes of stenting with or without endoscopic suturing of the defect were assessed. Univariate and multivariate logistic regression models were used to examine factors associated with successful defect closure. RESULTS: One hundred and fourteen patients with esophageal wall defects underwent 254 endoscopies with an overall complete closure rate of 75.8%. Twenty-three (20.2%) patients underwent primary closure using endoscopic suturing and subsequent esophageal stenting, while 91 (79.8%) underwent esophageal stenting only. The dual modality group (versus the stent-only group) had similar defect closure rates (84.2 vs. 73.8%, p = 0.55) and time to stent migration (37 vs. 12.5 days, p = 0.07), but was associated with longer procedure times (60 vs. 36 min, p < 0.01) and fewer additional endoscopic procedures (13.6 vs. 43.2%, p = 0.01). Stent suturing significantly decreased migration (35.5 vs. 58.5%, p = 0.04), was associated with fewer additional endoscopies (15.4 vs. 50%, p < 0.01) and reduced need for additional stents (7.7 vs. 34.3%, p < 0.01). On multivariate analysis, chronic defects (> four weeks old) were 81% less likely to close compared to acute (≤ 4 weeks) defects (OR 0.19, CI 0.04-0.77, p = 0.02), and large diameter stents (23 mm) were associated with higher odds of defect closure (OR 3.36, CI 1.02-11.4, p = 0.04). CONCLUSION: Endoscopic treatment of esophageal wall defects is safe, effective, and more likely to be successful in acute defects using larger caliber stents. Stent suturing reduces migration, need for additional endoscopic procedures, and stent exchanges. Further comparative studies with larger cohorts are needed to validate our results.

Shielding effectiveness: A weighted figure of merit for space radiation shielding.

The risk to space crew health and safety posed by exposure to space radiation is regarded as a significant obstacle to future human exploration missions to the Moon, Mars, and beyond. Engineers developing future spacecraft or planetary surface habitats can benefit from detailed knowledge of a broad range of possible materials that could provide improved protection to space crews from the deleterious effects of prolonged exposure to the space radiation environment. As one step towards providing this knowledge base, we have developed an empirical weighted figure of merit, referred to as shielding effectiveness, that quantifies the ability of a candidate material to shield space crews from the space radiation environment. The shielding effectiveness, as formulated in this study, accounts for the competing physical aspects of target and projectile fragmentation to provide a comprehensive assessment of radiation protection with regard to passive shielding for space applications. The empirical data used in determining shielding effectiveness was obtained from proton and heavy ion accelerator-based experiments wherein Al2O3:C optically stimulated luminescence dosimeter and CR-39 plastic nuclear track detector were irradiated behind candidate space radiation shielding materials of varying composition and depth. As a test case, the experimental setup was exposed to nominal beams of 1 GeV protons, and 1 GeV/n 28Si and 56Fe heavy ions, the latter serving as a sample of the high linear energy transfer portion of the galactic cosmic ray spectrum. Established radiation dosimetry techniques were used to obtain linear energy transfer spectra, absorbed dose, and dose equivalent as a function of depth. Based on the measurement results, a shielding effectiveness value was computed, quantifying the efficacy of the candidate material as a function of depth, with cumulative weighting factors accounting for the measured percent composition of baryonic matter in the galactic cosmic ray spectrum, and the measured percent contribution to absorbed dose and dose equivalent. The methodology for shielding effectiveness was tested using the common materials of aluminum, copper, graphite, and water, with polyethylene serving as the standard reference. The preliminary shielding effectiveness values for these materials confirm the low Z principle for effective space radiation shielding, and, furthermore, these values tend to be lower when the effectiveness calculation is based on dose equivalent. Of the common materials studied here, at a bulkhead depth of 5 g/cm2, all materials provide a similar level of radiation protection to within standard error. In addition, this method can be used to supplement and/or verify similar findings obtained from transport models.

Self-expandable metal stents for obstructing colonic and extracolonic cancer: European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline

This Guideline is an official statement of the European Society of Gastrointestinal Endoscopy (ESGE). This Guideline was also reviewed and endorsed by the Governing Board of the American Society for Gastrointestinal Endoscopy (ASGE). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was adopted to define the strength of recommendations and the quality of evidence. Main recommendations The following recommendations should only be applied after a thorough diagnostic evaluation including a contrast-enhanced computed tomography (CT) scan. 1 Prophylactic colonic stent placement is not recommended. Colonic stenting should be reserved for patients with clinical symptoms and imaging evidence of malignant large-bowel obstruction, without signs of perforation (strong recommendation, low quality evidence). 2 Colonic self-expandable metal stent (SEMS) placement as a bridge to elective surgery is not recommended as a standard treatment of symptomatic left-sided malignant colonic obstruction (strong recommendation, high quality evidence). 3 For patients with potentially curable but obstructing left-sided colonic cancer, stent placement may be considered as an alternative to emergency surgery in those who have an increased risk of postoperative mortality, I. e. American Society of Anesthesiologists (ASA) Physical Status ≥ III and/or age > 70 years (weak recommendation, low quality evidence). 4 SEMS placement is recommended as the preferred treatment for palliation of malignant colonic obstruction (strong recommendation, high quality evidence), except in patients treated or considered for treatment with antiangiogenic drugs (e. g. bevacizumab) (strong recommendation, low quality evidence).(AU)

Does preoperative cross-sectional imaging accurately predict main duct involvement in intraductal papillary mucinous neoplasm?

Main pancreatic duct (MPD) involvement is a well-demonstrated risk factor for malignancy in intraductal papillary mucinous neoplasm (IPMN). Preoperative radiographic determination of IPMN type is heavily relied upon in oncologic risk stratification. We hypothesized that radiographic assessment of MPD involvement in IPMN is an accurate predictor of pathological MPD involvement. Data regarding all patients undergoing resection for IPMN at a single academic institution between 1992 and 2012 were gathered prospectively. Retrospective analysis of imaging and pathologic data was undertaken. Preoperative classification of IPMN type was based on cross-sectional imaging (MRI/magnetic resonance cholangiopancreatography (MRCP) and/or CT). Three hundred sixty-two patients underwent resection for IPMN. Of these, 334 had complete data for analysis. Of 164 suspected branch duct (BD) IPMN, 34 (20.7%) demonstrated MPD involvement on final pathology. Of 170 patients with suspicion of MPD involvement, 50 (29.4%) demonstrated no MPD involvement. Of 34 patients with suspected BD-IPMN who were found to have MPD involvement on pathology, 10 (29.4%) had invasive carcinoma. Alternatively, 2/50 (4%) of the patients with suspected MPD involvement who ultimately had isolated BD-IPMN demonstrated invasive carcinoma. Preoperative radiographic IPMN type did not correlate with final pathology in 25% of the patients. In addition, risk of invasive carcinoma correlates with pathologic presence of MPD involvement.

Endoscopic ultrasound-guided fine-needle aspiration of melanoma metastatic to the pancreas: report of two cases and review.

Malignant melanoma is a neoplasm which originates from melanocytes. Surgical exploration for abdominal metastases of cutaneous melanoma reveals pancreatic metastases in 16 % of patients which is usually accompanied by other intra-abdominal spread. Endoscopic ultrasound (EUS) and EUS-guided fine-needle aspiration (EUS-FNA) of primary and metastatic pancreatic masses have already been described. We report the first use of EUS-FNA for the diagnosis of malignant melanoma metastatic to the pancreas. As our cases illustrate, these lesions may present as either cystic or solid pancreatic masses. Preparation of a cell block from the FNA aspirate and use of immunostaining may help to obtain the diagnosis. Despite thorough examination of the skin and mucous membranes, however, a primary site might not be found in these patients.