The neutron dose equivalent rate measurements by R3DR/R2 spectrometers on the international space station.

The data from two Bulgarian-German instruments with the basic name "Radiation Risk Radiometer-Dosimeter" (R3D) are discussed. The R3DR instrument worked inside the ESA EXPOSE-R facility (2009-2010), while R3DR2 worked inside the ESA EXPOSE-R2 facility (2014-2016). Both were outside the Russian Zvezda module on the International Space Station (ISS). The data from both instruments were used for calculation of the neutron dose equivalent rate. Similar data, obtained by the Russian "BTNNEUTRON" instrument on the ISS are used to benchmark the R3DR/R2 neutron dose equivalent rate. The analisys reveals that the "BTNNEUTRON" and R3DR/R2 values are comparable both in the equatorial and in the South Atlantic Anomaly (SAA) regions. The R3DR/R2 values are smaller than the "BTNNEUTRON" values in the high latitude regions. The comparison with the Monte Carlo simulations of the secondary galactic cosmic rays (GCR) neutron ambient dose equivalent rates (El-Jaby and Richardson, 2015, 2016) also shows a good coincidence with the R3DR/R2 spectrometer data obtained in the equatorial and high latitude regions.

Moving forward with elective vascular work: a reflection on the impact of COVID-19 on a regional vascular hub.

INTRODUCTION: Following the initial COVID-19 surge in the UK, there was a national incentive for elective vascular surgery to be restricted to 'clean' sites to reduce perioperative cross-infection and subsequent mortality. We assessed the risk of dying from perioperatively acquired COVID-19 during the peak of the London outbreak. METHODS: Forty-three consecutive patients who had vascular (n=48) procedures in March and April 2020 at a regional hub serving five London hospitals were analysed. The patients were screened for COVID-19 in the 30-day postoperative period and the main outcome measure was mortality from COVID-19. A comparison was then made with patients who underwent minimally invasive procedures in our integrated interventional radiology department. Median follow-up was 41 days (interquartile range 8-58) overall. RESULTS: Three patients (7%) in the vascular group (median age 61 years, all diabetic, two male) died from COVID-19, all of whom tested positive postoperatively. Two others became positive but recovered. In comparison, two patients (2%) in the interventional radiology group died from COVID-19; however, one was positive prior to their procedure. CONCLUSION: Only urgent vascular cases should be performed during a COVID-19 surge. However, with growing waiting lists for elective surgery following the pandemic's second wave, further restrictions may not be a viable long-term solution. When prevalence of the disease is lower and if resources allow, resumption of care at 'hot' sites should be considered, if safety measures can be implemented. The advantages of minimally invasive surgery may also reduce risk.

Enteric neuronal development in canine small intestine - an immunohistochemical study.

The development of the enteric nervous system (ENS) is still a valid and intensely studied issue. However, literature in the field has no data on this topic in the dog. The present investigations were performed in three groups of fetuses from mongrel dogs - from the third, sixth- -seventh, and ninth week of pregnancy - and in 3-5-day-old puppies (3 specimens for each age group). The tissues (the medial parts of the duodenum, jejunum, and ileum with the cecum and a small portion of the adjacent ascending colon) were cut using a cryostat and the sections were processed for single- and double-labeling immunohistochemistry using antisera against acetylated tubulin (AcTub), vesicular acetylcholine transporter (VAChT), nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), galanin (GAL), neuropeptide Y (NPY), substance P (SP), and calcitonin gene-related peptide (CGRP). In the 3-week-old fetuses, some oval cells invading the gut wall were found. From the seventh week of pregnancy onwards, two different enteric ganglia were present: submucosal and myenteric. The estimated number of nerve elements in the 9-week-old fetuses was much higher than that observed in the 6-7-week-old individuals. There was no significant difference in the estimated number of nerve structures between the 9-week-old fetuses and the 3-5-day-old puppies. The colonization pattern and the development of the ENS in the canine small intestine are very similar to those observed in other mam- mals. However, a few exceptions have been confirmed, regarding the time of appearance of the VIP-, GAL-, and CGRP-immunoreactive neurons, and their distribution in different portions of the canine bowel during development.

Solar modulation of the GCR flux and dose rate, observed in space between 1991 and 2019.

The paper presents the solar modulation of the long-term galactic cosmic rays (GCR) flux and dose rates variations, observed during 14 space experiments by 10 Bulgarian build Liulin-type spectrometers (LTS) (Dachev et al., 2015a). They worked in near Earth space and in the interplanetary radiation environment between January 1991 and January 2019. Data were collected by LTS in the low Earth orbit (LEO) in the L range between 4 and 6.2 or outside the magnetosphere. The major advantage of the data sets are that they are obtained by the electronically identical LTS. The Liulin measurements of about monthly averaged flux and dose rate data are compared with the monthly values of the modulation parameter, reconstructed from the ground based cosmic ray data (Usoskin et al., 2017). A good correlation between the two data sets is observed. The most important achievement of the paper is that for the first time a proof of the solar modulation of the long-term variations of the monthly averaged dose rates is obtained. These long-term experimentally obtained dose rate data could be used for modeling of the GCR space radiation risks to humans in the near Earth radiation environment. Parallel to the long-term dose rate varitions, the monthly averaged flux variations are also presented.

Aortocaval fistula, a potentially favourable complication of abdominal aortic aneurysm rupture in endovascular repair.

Endovascular aneurysm repair is an established treatment for ruptured abdominal aortic aneurysm. Primary aortocaval fistula is an exceedingly rare finding in ruptured abdominal aortic aneurysm, with a reported incidence of less than 1%. The presence of an aortocaval fistula used to be an unexpected finding in open surgical repair which often resulted in massive haemorrhage and caval injury. We present a case of ruptured abdominal aortic aneurysm with an aortocaval fistula that was successfully treated with percutaneous endovascular aneurysm repair under local anaesthesia. Despite a persistent type 2 endoleak the aneurysm sack shrank from 8.4cm to 4.8cm in 12 months. The presence of an aortocaval fistula may have depressurised the aneurysm, resulting in less bleeding retroperitoneally and may have promoted rapid shrinkage of the sac despite the presence of a persistent type 2 endoleak.

[Prevalence, clinical and morphological features of tooth root caries in the adult human]. / Rasprostranennost' i kliniko-morfologicheskie osobennosti kariesa kornia zuba u vzroslogo cheloveka.

The incidence of tooth root caries, the morphology of hard dental tissues and the clinical course of the pathology were studied in 4701 (2526 men and 2175 women) residents of St. Petersburg and the Leningrad Region aged 18 to 88 years, which were divided into age groups according to age periodization of Institute of Age Physiology RAS. The highest prevalence of tooth root caries was revealed in the older age groups making 9.88% in elderly age and 7.4% in old age. In young, 1st and 2nd mature age the tooth root caries was diagnosed relatively rare (in 0.26, 1.35 and 5.02% of cases, respectively). Morphological changes in the tooth root cement that predispose to the development of a carious process were determined. In the first adulthood the caries of the tooth root occurred against the background of gum recession in chronic generalized periodontitis especially diabetes patients. In people of the 2nd mature age, elderly and old age the caries of the tooth root was associated with poor oral hygiene, gingival recession due to periodontal disease, as well as in teeth supporting fixed or removable dentures.

Effectiveness of fascial closure technique following percutaneous endovascular aneurysm repair.

INTRODUCTION: Percutaneous access and closure is commonly performed for patients undergoing endovascular aneurysm repair (EVAR). It has proven to be a safe and successful method of closure associated with fewer complications when compared with the traditional open technique. Fascial closure is an alternative technique that can be used for closure reducing the risks associated with the open technique. The aim of this study was to assess the safety and durability of fascial closure for failed percutaneous closure device following EVAR. MATERIALS AND METHODS: Over a 12-month period, 49 patients who had undergone EVAR were identified via our EVAR register. Retrospective analysis of the clinical records was undertaken. We identified all the patients who had fascial closure of the groins following a failed percutaneous closure device. Patients had a computed tomography angiogram one month postoperatively, with duplex imaging and clinic follow-up three months later. RESULTS: Fascial closure was performed in 14 groins. It failed in three groins and these patients had traditional open repair. Fascial closure was successful in 11 groins (7 patients). Of these seven patients, one was female (6%). The mean age was 80 years (range 68-92 years). Two patients died and one was lost to follow-up. One pseudoaneurysms were seen on computed tomography angiogram, which was managed conservatively and had resolved on follow-up imaging. CONCLUSIONS: Fascial closure is a very good alternative to open repair after failure of the closure device.

Chimney Grafts in Aortic Stent Grafting: Hazardous or Useful Technique? Systematic Review of Current Data.

BACKGROUND: The chimney graft (CG) technique was introduced to rescue accidentally covered aortic branches during aortic endovascular repair. It extends the sealing zone. There is concern about "gutter" type I endoleak (EL-I) and about the durability of CGs. The aim of the present report was to analyze the rapidly increasing existing data. METHODS: A search was performed (PRISMA criteria) for all studies of visceral and thoracic/arch chimney grafts. Technical and clinical details and outcome were assessed. RESULTS: The present review includes 831 patients who underwent EVAR/TEVAR (endovascular aneurysm repair/thoracic endovascular aneurysm repair) with one or more chimney, periscope, or sandwich grafts. For aortic visceral vessels 517 patients received 911 visceral CGs and 314 patients received 364 arch CGs. Most procedures (81% visceral and 69% arch CGs) were elective. Thirty day mortality was 4% for both groups. The rate of early EL-I was 13% (visceral CGs) and 11% (arch CGs). Most EL-I were handled conservatively (observation: 70% for visceral CG and 45% for arch CG). Early CG patency was high (97-99%) and remained high during follow up (median 17 months). Late (after 30 days) EL-I was reported in nine visceral (2%) and 12 arch (4%) CG cases. Few other late complications were reported, but those losing a kidney at the initial repair seemed to have a high risk of requiring permanent hemodialysis. CONCLUSION: Increasing amounts of data support the benefit of visceral and arch chimney graft techniques. In particular, the low early mortality and complication rates and high long-term patency seem advantageous; however, the majority of cases have been treated electively, and there is a high risk of bias in all studies. Mid- to long-term data suggest few late complications, except in cases where one renal artery was sacrificed. The CG technique is valuable for complex urgent patients and needs further documentation for other patient groups.

Reinterventions after open and endovascular AAA repair.

Reinterventions seem to occur more frequently after endovascular aneurysm repair than after open surgical repair and are encountered in about 20% versus 10% of the cases, respectively. However, reinterventions following endovascular repair are predominantly endoluminal and early reinterventions are more frequent after open repair. The indications for reintervention after EVAR have changed over time. The incidence and type of reintervention depends on the complexity of the primary procedure, irrespective of whether it was open or endovascular. The use of a device outside instructions for use is associated with a higher complication rate but it may nevertheless be fully justified. Advanced stent-grafts such as fenestrated and branched devices require secondary procedures more often than a standard stent-graft. Similarly, more complex open repair, e.g. a bifurcated bypass, reimplantation of visceral arteries or a redo procedure, is also associated with more reinterventions than a simple tube graft. This manuscript presents some of the most common complications of open and endovascular aortic aneurysm repair and the reinterventions they require. Many of the complications are similar with both open and endovascular techniques. Limb thrombosis, infections and endoleaks are the most frequent indications for reintervention.

In situ fenestration: a novel option for endovascular aortic arch repair.

Aortic arch repair, is a surgical challenge irrespective of which technique is applied. While open surgical repair is a major trauma and a technically difficult procedure that many elderly patients tolerate poorly, the branched and fenestrated stent-grafts remain complex to implant safely. Hybrid procedures combine some of the advantages of both open and endovascular techniques but also many disadvantages. The possibility of total arch replacement with a standard off-the-shelf thoracic stent-graft and preservation of precerebral vessels by in situ fenestration has recently been reported. Some technical issues remain but recent technical adjuncts seem to facilitate temporary cerebral shunting during implantation as well as piercing of the stent-graft fabric. The positioning of fenestrations is inherently accurate by this technique which may be associated with less material fatigue and improve durability. Preliminarily, this technology holds the promise of simpler implantation, less risk for stroke and improved durability of the devices.

Anatomic feasibility of endovascular reconstruction in aortic arch aneurysms.

The purpose was to estimate the proportion of current open aortic arch reconstructions that might be feasible for endovascular repair. From all elective repair made in Southern Sweden in one center between 2005 and 2012, 129 open and eight endovascular aortic arch repairs were identified. The anatomy of the ascending arch and descending aorta as well as the arch vessels was categorized from multiplanar and axial computed tomography scans. Of 129 open cases, only two (1.5%) were suitable for endovascular repair. Among 137 all arch open and endovascular arch reconstructions performed during the study period, only 10 (7%) were candidates for endovascular repair. The most common exclusion for endovascular repair was an excessively large ascending aortic diameter. In conclusion, only a small proportion of patients having an open arch repair are suitable for endovascular arch repair, a finding related to the large diameter of the ascending aorta.

Chimney grafts in aortic occlusive disease.

The aim of this article was to present juxtavisceral aortic occlusive disease with particular reference to a novel therapeutic approach, namely protected stenting by means of so called chimney grafts. The juxta renal aortic occlusion is the last aortoiliac occlusive lesion not to be stented routinely because of the risk for trash and/or need for overstenting of vital aortic side branches. The risk for trash also exists in open repair which makes it particularly challenging in this setting. The patients have advanced atherosclerosis and are poor risks for major surgery. A safe endovascular approach is therefore desirable. These lesions are either predominantly thrombotic or heavily calcified plaques. The thrombotic lesions can be stented under protection of the visceral branches by temporary occlusion balloons. The calcified lesions, on the other hand, require overstenting of the visceral vessels that then need to be preserved by chimney grafts. These endovascular procedures are complex and time consuming but they are associated with less surgical trauma and hence improved morbidity, mortality and recovery. The median term results of chimney grafts are encouraging, although more patients and longer follow-up are still needed.

Balloon control for ruptured AAAs: when and when not to use?

Emergency endovascular aneurysm repair (eEVAR) for ruptured abdominal aortic aneurysm (rAAA) must be carried out instantly. This requires firm logistics that include the ability to cross-clamp the aorta without delay. The present article focuses on the technique of balloon control of the aorta in eEVAR with aspects on indications as well as the organization of this type of vascular service. Transfemoral insertion of the occlusion balloon under local anesthesia is advocated and described. The use of dual balloons shortens the time of visceral ischemia without necessitating repeat declamping until the aneurysm has been completely excluded. Staged declamping upon completion is necessary just as in open repair. A "balloon test" is suggested to better identify those high risk patients with a rAAA who may benefit from endovascular rAAA repair.

Remodeling of fetoplacental arteries in rats due to chronic hypoxia.

The increased fetoplacental vascular resistance due to chronic hypoxia cannot be explained by simple hypoxic vasoconstriction, as it sustains to some degree after recovery in normobaric environment. To verify a hypothesis that fetoplacental arteries undergo remodeling of their walls similar to remodeling of pulmonary arteries in hypoxic pulmonary hypertension, we used a model of the chronically hypoxic rat placenta. Han Wistar pregnant rats were exposed to 14-day hypoxia (10% of oxygen) during the 6th to 19th day of pregnancy. Chronic hypoxia elicited in both intraplacental (prelabyrinthine) and chorionic plate (insertion) arteries significant narrowing of their lumina. Irregular thickening of their adventitia due to an increase in collagen fibers as well as ground substance was observed; reticular fibers were fragmented. Because of remodeling of fetoplacental arteries, a model of chronically hypoxic rat placenta could simulate human preplacental hypoxia and consequent effects.

Incidence and management of complications after branched and fenestrated endografting.

Endovascular treatment of complex aortic aneurysms with fenestrated and branched stentgrafts is in rapid development. Early and midterm results from centers of excellence are very promising but the technique is still in its infancy. With the introduction of EVAR for complex aneurysms a new set of failure modes have also been introduced. These relate both to the specific deployment techniques of the devices and to their intrinsic design characteristics. Procedural planning is of utmost importance for success. Failure to accomplish this may result in disastrous and uncorrectable perioperative failure. The endograft must be correctly tailored to the patient with regards to branch and fenestration positioning and design. Migration of stent-graft components, target vessel occlusions due to branch compression or dislocation and fenestration malpositioning must be recognized during follow up and treated accordingly. The clinical consequences of complex aneurysm repair include spinal cord ischemia and peripheral embolisation and strategies to handle this must be present.

Intra-aneurysm sac pressure in patients with unchanged AAA diameter after EVAR.

OBJECTIVE: To study intra-aneurysm sac pressure and subsequent abdominal aortic aneurysm (AAA) diameter changes in patients without endoleaks that remain unchanged in AAA diameter more than 1 year after endovascular aneurysm repair (EVAR). METHODS: A total of 23 patients underwent direct intra-aneurysm sac pressure (DISP) measurements 16 months (IQR: 14-35 months) after EVAR. Tip-pressure sensors were used through translumbar AAA puncture. Mean pressure index (MPI) was calculated as the percentage of mean intra-aneurysm pressure relative to the simultaneous mean intra-aortic pressure. Aneurysm expansion or shrinkage was assumed whenever the diameter change was > or =5mm. Values are presented as median and interquartile range. RESULTS: In 18 patients, no fluid was obtained upon AAA puncture (group A). In five patients, fluid was obtained (group B). In group A, follow-up continued for 29 months (IQR: 15-35 months) after DISP; five AAAs shrank, 10 remained unchanged and three expanded (MPIs of 26% (IQR: 18-42%), 28% (IQR: 20-48%) and 63% (IQR: 47-83%) and intra-sac pulse pressures of 3 mmHg (IQR: 0-5 mmHg), 4 mmHg (IQR: 2-8mm Hg) and 12 mmHg (IQR: 6-20 mmHg), respectively, for the three subgroups). MPI and intra-sac pulse pressures were higher in AAAs that subsequently expanded (P=0.073 and 0.017, respectively). MPI and pulse pressure correlated with total diameter change (r=0.49, P=0.039 and r =0.39, P=0.109, respectively). Pulse pressure had a greater influence than MPI on diameter change (R(2)=0.346, P=0.041, beta standardised coefficient of 0.121 for MPI and 0.502 for pulse pressure). Similar results with stronger, and significant correlation to pulse pressure were obtained when relative diameter changes were used (r=0.55, P=0.017). In group B, MPI and AAA pulse pressure were 32% (IQR: 18-37%) and 1 mmHg (IQR: 0-6 mmHg), respectively. After 36 months (IQR: 21-38 months), one AAA shrank, three continued unchanged while one expanded. CONCLUSIONS: AAAs without endoleak and unchanged diameter more than 1 year after EVAR will often continue unchanged. Expansion can eventually occur in the absence of intra-sac fluid accumulation and is associated with higher and more pulsatile intra-sac pressure. However, in patients with intra-sac fluid, expansion can occur with low intra-sac pressures.

Mid-term outcome of endovascular revascularization for chronic mesenteric ischaemia.

BACKGROUND: : This study aimed to assess mid-term outcome after endovascular revascularization of chronic occlusive mesenteric ischaemia (CMI) and to identify possible predictors of mortality. METHODS: : Consecutive patients undergoing primary elective stenting for CMI between 1995 and 2007 were registered prospectively in a database. Patients with acute ischaemia were excluded. Retrospective case-note review and data analysis were performed. RESULTS: : Forty-three patients (10 men) were treated for stable (n = 30) or exacerbated (n = 13) CMI. Their median (interquartile range (i.q.r.)) age was 70 (60-79) years. Revascularization was successful in 47 of 49 vessels. The superior mesenteric artery (SMA), either alone (n = 34) or in combination with the coeliac trunk (n = 6), was the predominant target vessel. No patient died within 30 days. Median follow-up was 43 (i.q.r. 25-63) months and the estimated (s.e.) 3-year overall survival rate was 76(7) per cent. Two patients died from distal SMA occlusive disease and intestinal infarction after 6 and 18 months respectively. Previous stroke (P = 0.016), male sex (P = 0.057) and age (P = 0.066) were associated with mid-term mortality on univariable, but not multivariable analysis. Reintervention was needed in 14 patients, achieving a 3-year cumulative rate of freedom from recurrent symptoms of 88(5) per cent. CONCLUSION: : Endovascular treatment provided high early and mid-term survival rates in this series of patients with CMI, with low complication rates.