Lars-Gunnar Eriksson

Plasma confinement in JET H?mode plasmas with H, D, DT and T isotopes

The scaling of the energy confinement in H mode plasmas with different hydrogenic isotopes (hydrogen, deuterium, DT and tritium) is investigated in JET. For ELM-free H modes the thermal energy confinement time τth is found to decrease weakly with the isotope mass (τth ~M-0.25±0.22), whilst in ELMy H modes the energy confinement time shows practically no mass dependence (τth ~M0.03±0.1). Detailed local transport analysis of the ELMy H mode plasmas reveals that the confinement in the edge region increases strongly with the isotope mass, whereas the confinement in the core region decreases with mass (τthcore ∝ M-0.16), in approximate agreement with theoretical models of the gyro-Bohm type (τgB ~M-0.2).

Isotope scaling of the H mode power threshold on JET

Results are presented from a series of dedicated experiments carried out on JET in tritium, DT, deuterium and hydrogen plasmas to determine the dependence of the H mode power threshold on the plasma isotopic mass. The Pthr ∝ Aeff-1 scaling is established over the whole isotopic range. This result makes it possible for a fusion reactor with a 50:50 DT mixture to access the H mode regime with about 20% less power than that needed in a DD mixture. Results on the first systematic measurements of the power necessary for the transition of the plasma to the type I ELM regime, which occurs after the transition to H mode, are also in agreement with the Aeff-1 scaling. For a subset of discharges, measurements of Te and Ti at the top of the profile pedestal have been obtained, indicating a weak influence of the isotopic mass on the critical edge temperature thought to be necessary for the H mode transition.

Arterial embolisation in management of massive bleeding from gastric and duodenal ulcers.

OBJECTIVE We have tried angiography and selective arterial embolisation as a complement or another option in patients with massive bleeding from peptic ulcers who were considered poor candidates for surgery. DESIGN Prospective, descriptive study. SETTING University hospital, Sweden. PATIENTS Since 1998, 18 patients (11 women) with a median age of 78 years (range 53-94) had selective arterial embolisation for uncontrollable bleeding from peptic ulcers. INTERVENTION Superselective angiographic catheterisation and embolisation of the arterial branch that was supplying the ulcer. MAIN OUTCOME MEASURES The success rate of haemostasis and the overall outcome. RESULTS 13 patients were treated after failed endoscopic treatment to stop bleeding or to control recurrent bleeding after initial arrest, while 5 patients were treated for recurrent bleeding after emergency operations for bleeding ulcers. Most of the ulcers were in the duodenum. The patients were haemodynamically unstable and had a median haemoglobin concentration of 72 g/L (50-98). Embolisation of the arterial branch that was supplying the ulcer was feasible in all patients. Permanent haemostasis was achieved in all but one patient, although two patients needed a second embolisation for recurrent bleeding. One patient had the bleeding controlled at an emergency operation, but eventually died of respiratory complications. There were no serious complications of embolisation. CONCLUSION Angiographic embolisation may be an effective way to stop massive bleeding from gastroduodenal ulcers. Emergency operations in poor surgical candidates can therefore be avoided.

Endoscopic Marking with a Metallic Clip Facilitates Transcatheter Arterial Embolization in Upper Peptic Ulcer Bleeding

PURPOSE To enable accurate transcatheter arterial embolization (TAE) of the target vessel, a new technique to localize the exact position of a bleeding ulcer was tested that involves endoscopic marking of the ulcer with a metallic clip. MATERIALS AND METHODS In 13 patients (mean age, 75 years) with acute bleeding ulcers (11 duodenal ulcers, two malignant ulcers), a metallic clip was placed at gastroscopy followed or preceded by routine endoscopic treatment. The metallic clip was placed in the fibrous edge of the ulcer adjacent to the bleeding point. In 10 patients, TAE was indicated as a result of continued or recurrent bleeding. The artery was embolized with microcoils as close as possible to the clip. In three patients, there was no indication for TAE, so plain abdominal radiography was performed to determine whether the marking clip was still in place. RESULTS In 11 patients, the clip was still in place on radiography; in two, it had disappeared. Hemostasis was achieved in eight of 10 patients after TAE. In six patients, the clip was essential to identify the bleeding vessel. CONCLUSION Marking of the bleeding ulcer with a clip before TAE enhances the possibility that the correct vessel is embolized. This will most likely minimize the risk of recurrent bleeding after embolization, especially in patients who do not show contrast medium extravasation.

Liver Embolization with Trisacryl Gelatin Microspheres (Embosphere) in Patients with Neuroendocrine Tumors

Purpose: To report our experience of liver embolization with trisacryl gelatin microspheres (Embosphere™) in patients with metastatic neuroendocrine tumors. Material and Methods: Fifteen patients underwent selective embolization of the right or left hepatic artery with Embosphere. One lobe was embolized in seven patients and both lobes, on separate occasions, in eight patients. Seven patients had midgut carcinoids, two had lung carcinoids, one suffered from a thymic carcinoid, and five had endocrine pancreatic tumors. Eight patients suffered from endocrine symptoms, seven of whom had carcinoid syndrome and one WDHA (watery diarrhea, hypokalemia, achlorhydria) syndrome. Results: Partial radiological response was seen after eight embolizations (in six different patients), stable disease was observed after 13 embolizations (after three of these, necroses occurred), while radiological progression was noted after only two embolizations. Only two patients experienced a biochemical response. Clinical improvement of carcinoid syndrome was observed after five embolizations. There were no major complications. Fever >38°C was seen after all but four embolizations, and urinary tract infections were diagnosed after eight embolizations. Conclusion: Selective hepatic artery embolization with Embosphere particles is a safe treatment for patients with metastatic neuroendocrine tumors and may lead to partial radiological response as well as symptomatic improvement of disabling endocrine symptoms.

Determination of the relative glomerular filtration rate of each kidney in man. Comparison between iohexol CT and 99mTc-DTPA scintigraphy.

Iohexol and 99mTc-DTPA were used in 43 patients to determine the relative glomerular filtration rate (GFR), i.e., the GFR of each kidney in percent of total GFR. The amount of any GFR marker accumulating in Bowmans space, tubuli and renal pelvis within a few minutes after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was determined by CT using 10 slices of 8-mm thickness 1 to 4 minutes after injection. The renal accumulation of 99mTc-DTPA was determined with a gamma camera within 2 minutes after injection. The correlation coefficient between the two methods was 0.98. Due to the higher radiation dose from CT than from 99mTc-DTPA injection, relative GFR determination with CT should be performed when there is also a diagnostic need to reveal morphology.

Fractures of self-expanding metallic stents in periampullary malignant biliary obstruction

Background: Self-expanding metallic stents are widely used for relieving biliary duct obstruction in patients with unresectable periampullary malignancies. However, only a few studies have assessed the occurrence of fractures in these stents. Purpose: To determine the prevalence and significance of stent fracture after placement of self-expanding metallic stents for periampullary malignant biliary obstruction. Material and Methods: Over a 5-year period, 48 patients underwent placement of self-expanding metallic stents for periampullary malignant biliary obstructions. Stents were introduced 2–6 weeks after a percutaneous transhepatic biliary decompression. The medical records and relevant images were reviewed for stent patency, stent fracture, type of stent, and stent-related complications. Results: Stent fracture was detected in four of the 48 patients (8%): in one patient at 1 month and in three patients between 10 and 21 months after stenting. All four fractures involved one type of nitinol stent used in 38 patients. In one of the patients, fracture was complicated by life-threatening gastrointestinal bleeding. The mean survival time for all patients was 251 days (standard deviation [SD]±275 days) and the mean overall patency time for all stents was 187 days (SD±205 days). Conclusion: Stent fracture occurs after placement of self-expanding nitinol stents for periampullary malignant biliary obstruction. The low reported incidence of this complication may be due to a lack of awareness of and difficulty in detecting stent fracture. Fracture should be considered as a possible contributing factor in recurrent biliary obstruction after self-expanding metallic stent insertion.

The edge operational space in JET

In this paper we investigate differences of the ELM behaviour between RF and NB heated H-mode discharges in JET. The main result of this investigation is that the edge pedestal pressure with NB heating is higher than with RF heating for equal power fluxes crossing the separatrix. This can be explained by a higher population of fast ions in the edge region in the case of NB heating. Using data from NB heated steady-state H-modes we derive a scaling law for the width of the transport barrier. We find that the barrier width is proportional to the poloidal Larmor radius, which in turn is controlled by the ion population with the highest energy in the plasma edge.

Endovascular treatment of acute and chronic portal vein thrombosis in patients with cirrhotic and non-cirrhotic liver.

Background Treatment of patients with portal vein thrombosis (PVT) differs due to different etiology and wide range of symptoms but certain patients seems to benefit from endovascular intervention. Purpose To assess the safety and efficiency of endovascular treatment of acute and chronic PVT in patients with cirrhotic and non-cirrhotic liver. Material and Methods Twenty-one patients with PVT treated with an endovascular procedure in 2002–2013 were studied retrospectively. Data on etiology, onset and extension of thrombus, presenting symptoms, methods of intervention, portal pressure gradients, complications, recurrence of symptoms, re-interventions, clinical status at latest follow-up, and survival were collected. Results Four non-cirrhotic patients with acute extensive PVT and bowel ischemia were treated with local thrombolysis, in three combined with placement of a transjugular intrahepatic portosystemic shunt (TIPS) placement. Three recovered and have survived more than 6 years. In six non-cirrhotic patients with chronic PVT and acute or threatening variceal bleeding recanalization and TIPS were successful in three and failed in three. Eleven cirrhotic patients with PVT and variceal bleeding or refractory ascites were successfully treated with recanalization and TIPS. Re-intervention was performed in five of these patients and five patients died, three within 12 months of intervention. Four cirrhotic patients had episodes of shunt-related encephalopathy and three had variceal re-bleeding. Conclusion TIPS was found to be effective in reducing portal hypertension in patients with PVT. In patients with extensive PVT and bowel ischemia treatment with TIPS combined with thrombolysis should be considered.

Determination of the Relative Glomerular Filtration Rate of Each Kidney in Man

Iohexol and 99mTc-DTPA were used in 43 patients to determine the relative glomerular filtration rate (GFR), i.e., the GFR of each kidney in percent of total GFR. The amount of any GFR marker accumulating in Bowmans space, tubuli and renal pelvis within a few minutes after i.v. injection, before any marker had left the kidney via the ureter, was defined as proportional to the GFR of that kidney. The renal accumulation of iohexol was determined by CT using 10 slices of 8-mm thickness 1 to 4 minutes after injection. The renal accumulation of 99mTc-DTPA was determined with a gamma camera within 2 minutes after injection. The correlation coefficient between the two methods was 0.98. Due to the higher radiation dose from CT than from 99mTc-DTPA injection, relative GFR determination with CT should be performed when there is also a diagnostic need to reveal morphology.