Photon thermalization and a condensation phase transition in an electrically pumped semiconductor microresonator.

We report on an experimental study of photon thermalization and condensation in a semiconductor microresonator in the weak-coupling regime. We measure the dispersion relation of light and the photon mass in a single-wavelength, broad-area resonator. The observed luminescence spectrum is compatible with a room-temperature, thermal-equilibrium distribution. A phase transition, identified by a saturation of the population at high energies and a superlinear increase of the occupation at low energy, takes place when the phase-space density is of order unity. We explain our observations by Bose-Einstein condensation of photons in equilibrium with a particle reservoir and discuss the relation with laser emission.

Transjugular intrahepatic portosystemic shunt treatment of variceal bleeding in an unselected patient population.

OBJECTIVE: To evaluate transjugular intrahepatic portosystemic shunt (TIPS) in variceal bleeding in a clinical setting. MATERIALS AND METHODS: Retrospective review of 131 patients (116 with liver cirrhosis) treated with TIPS with covered stent grafts in a single centre from 2002 to 2016. RESULTS: Survival at 1 and 2 years was 70% and 57% in patents with, and 100% at 2 years in patients without liver cirrhosis, respectively. A high Child-Pugh score and severe hepatic encephalopathy (HE) within 12 months post-TIPS were related to increased mortality. Re-bleeding occurred in 8% within 12 months and was related to TIPS dysfunction and a post-TIPS portosystemic gradient (PSG) of ≥5 mmHg. The main cause of TIPS dysfunction was that the stent did not fully reach the inferior vena cava. There was no correlation between the PSG and the occurrence of HE. CONCLUSIONS: TIPS was safe and prevented re-bleeding in patients with variceal bleeding, with or without liver cirrhosis, regardless of Child-Pugh class and of how soon after bleeding onset, the TIPS procedure was performed. A post-TIPS PSG of ≥5 mmHg was associated with an increased risk for re-bleeding and there was no correlation between the post-TIPS PSG and the occurrence of HE.

Transcutaneous port for levodopa/carbidopa intestinal gel administration in Parkinson's disease.

OBJECTIVE: To evaluate the safety and tolerability of the T-Port(®) for intestinal infusion of levodopa/carbidopa gel in patients with advanced Parkinson's disease (PD). METHODS: This prospective study was carried out in 24 patients with PD (15 males, mean age 61.8 years, mean duration PD 18.7 years). All adverse device effects were evaluated at 2 weeks, 3 months and 6 months and until explantation or death. RESULTS: Post-operative complications were similar to endoscopic gastrojejunostomy placement (four peritoneal irritation, one pocket pain). Eight patients with prior experience with the endoscopic gastrojejunostomy preferred the T-Port. The total device experience was 83.6 years, and the average survival time was 3.6 (range 1.1-5.2) years. Six T-Ports were still in use, and two patients had died due to non-device-related reasons. Sixteen T-Ports had been explanted due to 15 stoma reactions (14 inflammations and one infection) and one tilting of the T-Port. The T-Ports were replaced with endoscopic gastrojejunostomy system as replacements with T-Ports were not part of the study. Only two device malfunctions occurred (one catheter breakage at 3 year post-implant and one T-Port leakage of levodopa/carbidopa gel). No tube kinking, dislocation or blockage occurred. The number of adverse device effects proved to be significantly lower as compared to the endoscopic gastrojejunostomy literature data. CONCLUSIONS: The T-Port is safe and well tolerated, and the low number of tube problems is a potential advantage compared with the endoscopic gastrojejunostomy system. Proper cleaning and local treatment of the stoma site around the T-Port are essential to prolong its longevity.

Selective intra-arterial dual-energy CT angiography (s-CTA) in lower extremity arterial occlusive disease.

OBJECTIVE: In patients with peripheral arterial occlusive disease, renal impairment is a common contraindication to iodine and gadolinium contrast media, which limits the utility of conventional computed tomography angiography (CTA) and magnetic resonance angiography (MRA). It is proposed that selective intra-arterial dual-energy CT-angiography (s-CTA), that is CTA with intra-arterial injection of an ultra-low dose iodine contrast media, is a feasible, safe and accurate alternative imaging method to conventional non-invasive contrast enhanced vascular imaging in this patient group. The aim of this study was to report a preliminary experience of s-CTA in patients with critical limb ischemia and renal insufficiency with respect to safety, feasibility, and diagnostic accuracy. MATERIALS AND METHODS: Ten non-consecutive patients with ischemic foot ulcers underwent s-CTA of one leg. Procedure related complications were recorded and imaging results were compared with conventional digital subtraction angiography (DSA). RESULTS: A median 17 mL (range 10-19 mL) contrast media (400 mg I/mL) was used. The median baseline plasma creatinine was 163 µmol/L (range 105-569) pre s-CTA versus 153 µmol/L (range 105-562) post s-CTA (p = .24). There was no puncture site complication. Among the patients selected for intervention (n = 6 with 30 arterial segments) the s-CTA findings correlated well with the DSA findings; the diagnostic sensitivity was 100%, the specificity 89%, and the accuracy 93%. CONCLUSION: In this pilot study, a novel imaging method (s-CTA) is presented that provides high-quality arterial phase images with ultra-low dose iodine contrast media useful also for patients unsuitable for conventional contrast enhanced imaging methods because of renal insufficiency.

Percutaneous closure of large femoral artery access with Prostar XL in thoracic endovascular aortic repair.

OBJECTIVES: To investigate the technical success rate of Prostar XL for closure of large (≥20F) femoral vascular access sites in thoracic endovascular aortic repair (TEVAR) procedures. METHODS: This was a single-center consecutive case series. All TEVAR procedures at Uppsala University Hospital 2006-2010 were registered prospectively. Reoperations and cases with open closure technique were excluded. Primary (early) technical failure was defined as closure failure requiring immediate (on-table) open surgical repair; late access-related complication occurred thereafter. The medical records, pre- and postoperative computed tomography images were reviewed retrospectively. RESULTS: A total of 164 TEVAR procedures were identified, of which 118 (71%) had a median 22F (range 20-26F) access site sealed with tandem Prostar XL. The indications for TEVAR were dissection (47%), aneurysm (42%), trauma (8%), and miscellaneous (3%). Median follow-up time was 10 months (range 1-62). Primary technical failure occurred in 10 of 118 (8%). These cases were converted to cut-downs and surgical repair (n = 7), femoral fascia suturing (n = 2), and external compression with the Femo-Stop device (n = 1). Hypertension was associated with primary failure (p = .005), and a trend was observed for high age (p = .078) and increased groin subcutaneous fat layer (p = .077). Late access-related complications included pseudo-aneurysms (n = 12), small hematomas (n = 7), superficial groin infections (n = 2), and deep venous thrombosis (n = 1). None of the late complications required surgical treatment. CONCLUSIONS: The access closure technique with tandem Prostar XL for large access sites during TEVAR is safe, in experienced hands. Few technical failures and few late complications occur, and they are usually benign.

Early and long-term outcome after thoracic endovascular aortic repair (TEVAR) for acute complicated type B aortic dissection.

OBJECTIVES: The study aimed to investigate early and long-term outcome of thoracic endovascular aortic repair (TEVAR) for acute complicated type B dissection. DESIGN: This was a retrospective, single-centre, consecutive case series. MATERIALS AND METHODS: During the period 1999-2009, TEVAR was carried out in 50 patients with non-traumatic acute complicated type B dissection, and in another 10 patients with acute complications, including rupture, end-organ ischaemia and acute dilatation during the primary hospitalisation, but >14 days after onset of symptoms. Thus, in total, 60 patients were included; 22 with a DeBakey type IIIa dissection and 38 with a type IIIb; median age was 67 years. Early (30-day) and long-term (5-year) survival, re-intervention rate and complications were recorded until 1 July 2010. RESULTS: Within 30 days, two (3%) deaths, one (2%) paraplegia and three (5%) strokes were observed. Five-year survival was 87% and freedom from re-intervention at 5 years was 65%. CONCLUSIONS: In patients with acute complicated type B aortic dissection, TEVAR can be performed with excellent early and long-term survival, whereas morbidity and long-term durability must be further elucidated.

The value of intravascular phased-array imaging in endovascular treatment of thoracic aortic pathology.

BACKGROUND: Careful pre-, intra- and postoperative diagnostics in endovascular treatment of thoracic aortic pathology is crucial for a favourable outcome. Computer tomography (CT) and digitally subtracted angiography (DSA) do not always provide sufficient diagnostic information. PURPOSE: To report our primary experiences of using intraluminal phased-array imaging (IPAI) as an additive tool for diagnostics and endovascular treatment of thoracic aortic pathology. MATERIAL AND METHODS: Eleven patients, nine men and two women (mean age 60, range 45) were examined intraoperatively with IPAI in stentgraft procedures of thoracic aortic pathology. RESULTS: IPAI could detect and visualize the entries and re-entries in the intima. Aortic branch vessels could be visualized for patency both during and immediately after stentgraft deployment. It was also possible to detect ceased blood flow in the false lumen or aneurysmal sac after stentgraft deployment. CONCLUSION: IPAI is a helpful tool for diagnostics and for guiding stentgraft placing in the treatment of thoracic aortic pathology.

Intravascular ultrasound with a vector phased-array probe (AcuNav) is feasible in endovascular abdominal aortic aneurysm repair.

BACKGROUND: The ideal imaging method for endovascular aneurysm repair (EVAR) should provide all data regarding diagnosis, measurements, and guiding of stent-graft deployment. Contrast-enhanced computed tomography (CT) is used for preoperative EVAR planning, together with intraoperative angiography. However, the administered contrast volume might result in contrast-induced nephropathy (CIN). PURPOSE: To develop a technique for aortic measurements, vessel wall evaluation, and stent-graft positioning by using a vector phased-array intravascular ultrasound probe with color Doppler function (AcuNav) in elective EVAR. MATERIAL AND METHODS: Thirteen elective EVAR patients were included. AcuNav was compared to pre- and postoperative CT examinations, perioperative angiography, and postoperative duplex. RESULTS: Measurements for stent-graft sizing were easily obtained and facilitated by the color Doppler function and corresponded well with CT and angiography. The combined information from AcuNav and fluoroscopy provided exact positioning of the stent graft. An aortic placement of the probe provided superior imaging results compared to an inferior vena cava approach. Detection of endoleak was found to be difficult. No complications were registered. CONCLUSION: The use of AcuNav combined with fluoroscopy in EVAR was found to be safe, effective, and feasible in planning and guiding EVAR procedures. Best results were seen with the probe placed in the artery. AcuNav might be used to replace contrast-enhanced CT and angiography, hence reducing the risk of CIN, especially in high-risk patients.

Outcome after endovascular revascularization of atherosclerotic renal artery stenosis.

BACKGROUND: With an aging population, more patients might be treated for atherosclerotic renal artery stenosis (ARAS). The goal of this treatment is to achieve a dialysis-free life or a well-controlled blood pressure with reduced risks of cardiovascular complications. PURPOSE: To analyze the clinical outcome of percutaneous transluminal renal artery angioplasty without stenting (PTRA) or with stenting (PTRS) for ARAS at one center. MATERIAL AND METHODS: The study group comprised 152 patients who underwent 203 PTRA/PTRS. All had hypertension, and 45% had azotemia. A retrospective collection of baseline and postprocedural number of antihypertensive drugs, blood pressure, and serum creatinine were analyzed during a follow-up of 3-18 months. RESULTS: Technical success rate was 95%, and clinical benefit was seen in 63% of patients. Complications included a 30-day mortality rate of 1.5%, a total complication rate of 35%, and major adverse events in 13%. The major adverse events were highly related to azotemia. Major adverse events within 30 days, with permanent disability, were seen in 5% and almost exclusively in patients with moderate or severe renal impairment. A subgroup analysis of 28 patients with renal duplex resistive index (RI) pre-PTRA/S and 6 months' follow-up showed a benefit of PTRA/PTRS in 17 (68%) of the 25 patients with RI <80 and in all three (100%) of the patients with RI >or=80. CONCLUSION: Endovascular treatment of ARAS has an excellent technical success rate, with a clinical improvement rate of >60%. However, it is associated with a considerable complication rate. Serious complications are seen mainly in azotemic patients. Predictors of clinical response could not be identified. Renal duplex RI is questioned as a predictor of clinical outcome.

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 future of imaging in the management of abdominal aortic aneurysm.

The development of endovascular techniques depends on the concomitant development of imaging techniques. Imaging with ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MR) is evolving at rapid pace. Angiography has largely been replaced by these techniques as a diagnostic tool in the clinical setting. New methods, e.g., rotational angiography and intravascular ultrasound, will play an important role in endovascular treatment of vascular disease. It is necessary to have easy access to ultrasonography, CT and MR images in future hybrid angiographic/surgical suites and the operator must be able to do advanced immediate reconstructions in a sterile environment. The combined use of advanced imaging, open and endovascular techniques will further improve the treatment of vascular disease in the future.

Propositions for refinement of the hybrid surgical technique for treatment of thoraco-abdominal aortic aneurysm.

Traditional open repair of thoraco-abdominal aortic aneurysms Crawford type II-IV carries a high perioperative risk and mortality. The hybrid technique for combined surgical and endovascular treatment offers an interesting alternative with reduced risk of paraparesis and possibly a reduced mortality rate. Propositions for refinement of this approach are outlined based on a single centre experience.

Remodeling of the thoracic aorta after stent grafting of type B dissection: a Swedish multicenter study.

AIM: Endovascular repair of complicated type B dissections has evolved as a promising alternative to open repair. Previous studies have indicated that continued false lumen flow is a predictor of continued aortic dilatation and risk of rupture during follow-up. This multicenter study was conducted to analyze the postoperative changes of the false lumen after endografting of complicated type B dissections. METHODS: All patients treated with endovascular stent grafts for thoracic type B dissections at 5 major Vascular Centers in Sweden were identified through local databases. Review of charts and all available pre- and postoperative CT scans were performed to identify demographics, indications for repair as well as postoperative changes of the aorta and false lumen. RESULTS: A total of 129 patients treated for type B dissections between 1994 and December 2005 were identified. Median radiological follow-up was 14 months. Fourteen patients died perioperatively leaving 115 patients available for analysis. Seventy-four of these had CT imaging of sufficient quality for morphological analysis. The vast majority of acute patients were treated for rupture or end-organ ischemia whereas most chronic patients were treated for asymptomatic aneurysms. In 80% of patients, the false lumen thrombosed along the stent graft but it remained perfused distal to the stent graft fixation in 50% of patients. Only 5% of patients presented with aortic enlargement of the stent grafted area when adequate proximal sealing was achieved. The distal, uncovered aorta displayed expansion in 16% of patients. CONCLUSIONS: The stent grafted thoracic aorta after type B dissection appears to be stabilized by covering the primary entry site with a stent graft in the majority of both acute and chronic dissections. The uncovered portion of the aorta distal to the stent graft, however, remains at risk of continuous dilatation. Stent grafting for complicated type B thoracic dissections seems to be a treatment option with reasonable morbidity and mortality even though the incidence of severe complications is still significant.

Investigation of the excluded stomach after Roux-en-Y gastric bypass.

BACKGROUND: One problem with Roux-en-Y gastric bypass (RYGBP) is that it leaves the bypassed segment not readily available for endoscopic or radiographic examinations. MATERIALS AND METHODS: Three males, 50, 54 and 64 years old, suffered from repeated, gastrointestinal bleeding of unknown origin requiring transfusion 1/2, 1 and 7 years after RYGBP. Access to the stomach was obtained by an ultrasound-guided percutaneous gastrostomy. RESULTS: We could perform endoscopy, barium studies and gastric acid output measurements through the gastrostomy. Histological gastritis, low acid output and absence of H. pylori infection were found. CONCLUSION: We were able to exclude severe gastric disease in our patients.

Tumour inhomogeneities on magnetic resonance imaging, a new factor with prognostic information in non-Hodgkin's lymphomas.

The prognostic importance of inhomogeneities on magnetic resonance imaging (MRI) in non-Hodgkin lymphomas (NHL) was evaluated. Forty-six consecutive patients with high-grade NHL were examined and, for comparison purposes, 13 patients with low-grade NHL. The degree of inhomogeneity was measured with a quantitative method (IH8) and a subjective evaluation was also performed. Patients with localized disease (stage I), who had all been treated with radiotherapy, had an excellent prognosis, which was independent of the degree of tumour inhomogeneity. In generalized NHL (stages II-IV) treated with chemotherapy, IH8 provided prognostic information in high-grade NHL. Patients with pronounced tumour inhomogeneity, in particular, had a very poor prognosis. The prognostic impact was also seen if the analyses were performed with high-grade and low-grade NHLs grouped together. The inhomogeneities may indicate a mechanism related to treatment failure after chemotherapy, but not after fractionated radiotherapy.

Macroprolactinomas: serial MR imaging in long-term bromocriptine therapy.

PURPOSE: To study the changes in macroprolactinomas during long-term bromocriptine therapy by means of serial MR imaging, and to correlate the findings to the serum prolactin (S-PRL) levels. PATIENTS AND METHODS: Thirteen patients with macroprolactinomas were studied before and during bromocriptine therapy; six to 11 MR examinations were performed with a duration of follow-up of 22 to 74 months. Tumor size, extension, relationship to adjacent structures, and signal intensity patterns were evaluated. Signal intensity ratios and T2 values were calculated in areas of apparently solid tumor tissue. RESULTS: Bromocriptine effectively reduced the size of all tumors; the size reduction was already significant at 1 week, but often continued for several years. Reenlargement during therapy was seen in three cases. The development of chiasmal herniation parallel to increasing cisternal invagination into the sella was a common finding, but was not correlated to visual symptoms. Signal intensity patterns corresponding to hemorrhage, cysts or necrosis were frequently observed, and transitions from one pattern to another were common. Hemorrhage occurred mainly in tumors corresponding to high initial serum prolactin levels. After 1 year of therapy, there was a significant increase in T2 values, indicating an increased water content in residual solid tumor tissue. CONCLUSIONS: MR is valuable for follow-up in bromocriptine therapy of macroprolactinomas, and provides new information on the tumor size changes, the inner structure of the tumors, and the optic chiasm.

Diagnostic methods in planning palliation of spinal metastases.

In a prospective study of 30 patients with newly diagnosed spinal metastases the benefit of different imaging techniques in planning palliation was studied. Magnetic resonance imaging (MRI) was compared to scintigraphy, conventional radiography and computerized tomography (CT), prior to radiotherapy or surgery. In the first comparison, a total of 159 pathologic lesions could be evaluated. MRI was superior in the detection of suspect metastases compared to conventional radiography and scintigraphy (P less than 0.0001 and p less than 0.01, respectively). MRI also gave useful information about adjacent soft tissue components, vessels, nerves and spinal cord compression, i.e. useful information when planning stabilizing surgery. Both MRI and CT were sensitive and specific methods but when comparing 120 pathologic lesions the detection rate of MRI was significantly higher than that of CT (p less than 0.01). In conclusion, scintigraphy and conventional radiography are adequate enough if palliative radiotherapy is planned. When considering surgery MRI is advocated preoperatively for defining operability.

Relative proton density and relaxation times in liver metastases during interferon treatment.

Relaxation times and relative proton densities were calculated from magnetic resonance examinations of the liver in eight patients with liver metastases from neuroendocrine tumours. Single, spin-echo sequences with eight different repetition times and a four-echo sequence were used to calculate T1 and T2 in tumour and normal liver, and the proton density tumour-liver quotient, before and during treatment with interferon. Changes over time of these parameters were compared with variations in tumour marker levels and changes in size and number of the metastases. During therapy, six out of eight cases showed a decrease in tumour T1, five responding to therapy and one with stationary disease, while the two patients with progressive disease showed unchanged tumour T1. The proton density quotient also decreased in a corresponding way, indicating a change in water content in tumours responding to interferon therapy. No significant change in liver T1, tumour T2 or liver T2 occurred in any patient. It is thus possible to perform reliable measurements of relaxation parameters over time, which may be valuable in follow-up of tumour treatment.

Disc degeneration and associated abnormalities of the spine in elite gymnasts. A magnetic resonance imaging study.

The thoracolumbar spine was examined by magnetic resonance imaging (MRI) and the history of back pain was analyzed in 24 male elite gymnasts (age range, 19-29 years) and in 16 male nonathletes (age range, 23-36 years). Disc degeneration, defined as reduced disc signal intensity, was significantly more common in athletes (75%) than in nonathletes (31%). The gymnasts also had a higher incidence of other abnormalities of the thoracolumbar spine, and there was a significant correlation between reduced disc signal intensity and the other abnormalities among the gymnasts. There were also significant correlations between back pain and reduced disc signal intensity and abnormal vertebral configuration when the gymnasts run a high risk of developing severe abnormalities of the thoracolumbar spine, and they often have a history of back pain.

1991 Volvo Award in clinical sciences. Smoking and lumbar intervertebral disc degeneration: an MRI study of identical twins.

The primary objective of this study was to determine whether disc degeneration, as assessed through magnetic resonance imaging, is greater in smokers than in nonsmokers. To control for the maximum number of potentially confounding variables, pairs of identical twins highly discordant for cigarette smoking were selected as study subjects. Data analyses revealed 18% greater mean disc degeneration scores in the lumbar spines of smokers as compared with nonsmokers. The effect was present across the entire lumbar spine, implicating a mechanism acting systemically. This investigation demonstrates the efficiency of using carefully selected controls in studying conditions of multifactorial etiology, such as disc degeneration.