Microdosimetry of an accelerator based thermal neutron field for Boron Neutron Capture Therapy.

The MUNES project (MUltidisciplinary NEutron Source) aims at the realization of an intense accelerator-based source of thermal neutrons, suitable for Boron Neutron Capture Therapy (BNCT). This exploits the interaction of 5 MeV protons onto a beryllium target, producing a fast neutron spectrum, which is moderated to the thermal range by a large assembly made of a Polytetrafluoroethylene (PTFE) tank filled with heavy water, surrounded by graphite blocks. The thermal neutron field is extracted through a bismuth beam port. The microdosimetric characterization of this field was performed using a cylindrical avalanche-confinement Tissue Equivalent Proportional Counter (TEPC) equipped with interchangeable cathode walls, positioned in front of the beam port. Measurements were taken both with a boron-doped wall and with an undoped one. The comparison of the two microdosimetric distributions allows to distinguish the relative dose contribution due to alpha particles and lithium ions from the BNC reaction from that of photons and other particles from neutron interactions on the cathode walls. The Relative Biological Effectiveness (RBE) was also calculated from the convolution of the measured spectra with a biological weighting function. This paper describes the experimental microdosimetric approach and the results of measurements with a boron-loaded cathode performed for the first time at an accelerator-based BNCT source.

Commissioning of high current H+/D+ ion beams for the prototype accelerator of the International Fusion Materials Irradiation Facility.

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is aiming at demonstrating the low energy section of a 40 MeV/125 mA IFMIF deuteron accelerator up to 9 MeV with a full beam current in cw operation. For such a high-power beam, the LIPAc injector is required to produce a 100 keV D+ beam with 140 mA and match it for injection into the Radio Frequency Quadrupole (RFQ) accelerator. The injector is designed by CEA-Saclay based on the high intensity light ion source (SILHI). In 2019, the commissioning of the RFQ to demonstrate the D+ beam acceleration at a low duty cycle (0.1%) was conducted. A nominal beam current of 125 mA D+ beam was accelerated up to 5 MeV through the RFQ successfully. The LIPAc injector fully satisfied the requirements for RFQ beam commissioning at the pulse mode.

Development and installation of a radio frequency quadrupole cooler test.

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.

The Manitoba Cataract Waiting List Program.

This article describes the Manitoba Cataract Waiting List Program. This program uses a centralized database to track and prioritize all patients waiting for cataract surgery. It provides an objective and reliable measure of the length of the wait, and patients on the waiting list are treated in a more equitable fashion through application of a uniform method of prioritization. The program will allow for long-term tracking of quality of care through monitoring of the average length of wait for patients with comparable functional impairment. It will also allow for long-term monitoring of thresholds for surgery. It has brought to light previously undocumented issues, such as the simultaneous booking of both eyes for cataract surgery and variations in waiting time between surgeons.

Intraoperative clinical practice and risk of early complications after cataract extraction in the United States, Canada, Denmark, and Spain.

OBJECTIVE: To examine variation in intraoperative clinical practice and rates of adverse events after cataract surgery across four different healthcare systems. DESIGN: Multicenter cohort study. PARTICIPANTS: Patients were recruited from ophthalmic clinics in the United States (n = 75); in the Province of Manitoba, Canada (n = 12); in Denmark (n = 17); and the City of Barcelona, Spain (n = 10). In all, 1420 patients undergoing first eye cataract surgery were enrolled, with preoperative, perioperative, and postoperative clinical data collected on 1344 patients (95%). MAIN OUTCOME MEASURES: Occurrence of 23 specified intraoperative and early postoperative adverse events was measured. Four-month postoperative visual acuity outcome also was measured. RESULTS: Phacoemulsification was performed in two thirds of the extractions in the United States and Manitoba, in one third in Denmark, and in 3% in Barcelona (P < 0.001). More than 96% of extractions in North America and Denmark were performed with the patient under local anesthesia, whereas general anesthesia was used for 38% of extractions in Barcelona (P < 0.001). Rates of intraoperative adverse events were 11% to 12.8% in Manitoba, Denmark, and Barcelona and significantly lower in the United States (6%), mainly because of a lower rate of capsular rupture (P < 0.01). Significantly higher rates of early postoperative events were seen in the United States (18.8%) and Manitoba (20.4%) compared to Denmark (7.9%) and Barcelona (5%) (P < 0.001). The differences among sites in rates of events could not be explained by differences in recorded patient characteristics or surgical techniques. The occurrence of perioperative events was significantly associated with a worse 4-month visual outcome. CONCLUSION: The observed variation in clinical practice might represent a general trend of a slower diffusion of new medical technology in Europe compared with that of North America. Rates of intraoperative and early postoperative events varied significantly across sites.

Visual outcomes of cataract surgery in the United States, Canada, Denmark, and Spain. Report From the International Cataract Surgery Outcomes Study.

OBJECTIVE: To compare visual outcomes obtained following cataract surgery in 4 sites in North America and Europe where considerable differences in the organization of care and patterns of clinical practice have been previously described. METHODS: Patients scheduled for first eye-cataract surgery and aged 50 years or older were enrolled consecutively in a prospective multicenter study that collected clinical and patient interview data preoperatively and postoperatively. From the United States, 772 patients were enrolled; from the Province of Manitoba (Canada), 159; from Denmark, 291; and from the City of Barcelona (Spain), 200. Preoperative and 4-month postoperative visual acuity was obtained for 92% of the patients (n = 1291). RESULTS: The mean 4-month postoperative visual acuity of eyes operated on varied significantly across the 4 sites (P < .001) and had the following Snellen decimal fraction measurements: 0.49 in Barcelona, 0.65 in Denmark, 0.66 in Manitoba, and 0.74 in the United States. However, while crude visual acuity outcome figures varied significantly, no significant difference was observed across the 4 sites regarding the risk of poorer visual outcome after controlling for differences in age, preoperative visual acuity, and general health status for patients with no ocular comorbidity. Older age, poorer preoperative visual acuity, poorer preoperative general health status, and coexisting ocular comorbidity were predictors of a poorer visual outcome. CONCLUSION: A previously identified variation in treatment modalities across the 4 sites did not seem to affect patients' visual acuity outcomes.

Ophthalmology undergraduate education in Canada.

OBJECTIVE: To compile a database recording components of undergraduate education in ophthalmology in Canada. DESIGN: Mailed questionnaire survey. SETTING: The 16 Canadian medical schools. PARTICIPANTS: All ophthalmology undergraduate program directors. OUTCOME MEASURES: Teaching hours, subjects and clinical skills taught, examination methods. RESULTS: Almost all schools covered a similar curriculum and used multiple-choice examinations. The number of hours devoted to preclerkship teaching was similar, but only seven schools had a mandatory clerkship rotation. Overall, 69% of the annual graduating medical school class receive clinical exposure to ophthalmology during their clerkship. Almost all schools provided electives that were similar in structure. CONCLUSIONS: There was great similarity in the curricula for medical student teaching in Canada. Efforts should be undertaken to increase the proportion of medical students receiving clinical teaching in ophthalmology. Increased coordination and collaboration in undergraduate teaching can be achieved in specific areas with future data sharing.

Variation in indications for cataract surgery in the United States, Denmark, Canada, and Spain: results from the International Cataract Surgery Outcomes Study.

BACKGROUND/AIMS: International comparisons of clinical practice may help in assessing the magnitude and possible causes of variation in cross national healthcare utilisation. With this aim, the indications for cataract surgery in the United States, Denmark, the province of Manitoba (Canada), and the city of Barcelona (Spain) were compared. METHODS: In a prospective multicentre study, patients scheduled for first eye cataract surgery and aged 50 years or older were enrolled consecutively. From the United States 766 patients were enrolled; from Denmark 291; from Manitoba 152; and from Barcelona 200. Indication for surgery was measured as preoperative visual status of patients enlisted for cataract surgery. Main variables were preoperative visual acuity in operative eye, the VF-14 score (an index of functional impairment in patients with cataract) and ocular comorbidity. RESULTS: Mean visual acuity were 0.23 (USA), 0.17 (Denmark), 0.15 (Manitoba), and 0.07 (Barcelona) (p < 0.001). When restricting the sample to eyes with normal retina and macula, no significant difference between United States and Denmark was observed (p > 0.05). Mean VF-14 scores were 76 (USA), 76 (Denmark), 71 (Manitoba), and 64 (Barcelona) (p < 0.001). CONCLUSION: Similar indications for cataract surgery were found in the United States and Denmark. Significantly more restricted indications were observed in Manitoba and Barcelona. Possible explanations for the results are discussed, including differences in sociodemographic characteristics, access to care, surgeons' willingness to operate, and patient demand.

International variation in anesthesia care during cataract surgery: results from the International Cataract Surgery Outcomes Study.

OBJECTIVES: To describe international variation in anesthesia care and monitoring during cataract surgery and to discuss its implications for cost and safety. METHODS: A standardized questionnaire was sent to random samples of ophthalmologists in the United States, Canada, and Barcelona, Spain, and to all ophthalmologists in Denmark. The survey was conducted in 1993 and 1994. Certified ophthalmologists who had performed 1 or more cataract extractions in the previous year were eligible for enrollment. RESULTS: The response rates were 62% in the United States (n=148), 67% in Canada (n=276), 70% in Barcelona (n=89), and 80% in Denmark (n=82). The anesthetic technique for cataract surgery varied significantly between sites (P<.001). Surgeons reported that retrobulbar blocks were used for 46% of the cataract extractions in the United States, 70% in Canada, 66% in Denmark, and 31% in Barcelona. In Barcelona, general anesthesia was used for 23% of the cataract extractions; it was used for less than 3% of the extractions at the other 3 sites. Peribulbar blocks or topical anesthesia was used for the remaining extractions. In the United States, Canada, and Barcelona, surgeons reported that vital functions were monitored during more than 97% of the extractions and anesthesia surveillance was used during more than 78% of the extractions. In Denmark, ophthalmologists reported that vital functions were monitored and anesthesia surveillance was used for 1% of the cataract extractions (P<.001). CONCLUSIONS: Substantial international variation in anesthesia care and monitoring during cataract surgery was observed. The findings suggest a need for further research to determine whether less intensive monitoring is cost-effective.

Practices associated with cataract surgery in Canada: results of a national survey.

OBJECTIVE: To examine Canadian ophthalmologists' reported practices related to cataract surgery. DESIGN: Mailed questionnaire survey. SETTING: Canada. PARTICIPANTS: Random sample of 698 ophthalmologists from the mailing list of the Canadian Ophthalmological Society. Of the 528 eligible ophthalmologists 353 completed the questionnaire (response rate 67%). A total of 276 respondents were classified as cataract surgeons (performed at least one cataract operation in the preceding year [1992]) and were included in the study. OUTCOME MEASURES: Reported use of preoperative ophthalmic tests, surgical technique, cataract anesthesia (including type of block and who administers it) and postoperative care. RESULTS: Most of the preoperative tests examined either were so routine as to be done in almost all cases or were rarely done at all. A total of 52% of the respondents were identified as predominantly extracapsular cataract extraction surgeons (ECCE), 46% as predominantly phacoemulsification surgeons and 2% as predominantly intracapsular cataract extraction surgeons. Overall, 57% of the respondents reported high use of retrobulbar anesthesia, 18% reported high use of peribulbar anesthesia, and 0.7% reported high use of general anesthesia. The mean number of postoperative visits in the first 4 months after surgery was 4.25. The mean rate of Nd:YAG laser capsulotomy in the first year after cataract surgery was 17.9%; 91% of the respondents reported a rate less than 40%. CONCLUSIONS: There seems to be limited use of nonessential preoperative ocular testing by Canadian cataract surgeons. Although ECCE remains the most common type of surgery performed, there appears to be a substantial number of surgeons trying phacoemulsification, and this will likely become the predominant technique in the near future. The self-reported practices of Canadian surgeons with relation to preoperative testing and postoperative follow-up appear to be consistent with the Clinical Practice Guideline for cataract surgery set by the US Agency for Health Care Policy and Research. However, variations in the number of postoperative visits and Nd:YAG capsulotomy rates merit further investigation.

International variation in ophthalmologic management of patients with cataracts. Results from the International Cataract Surgery Outcomes Study.

OBJECTIVES: To describe international variation in the management of patients with cataacts in 4 health care systems and to discuss the potential implications for cost and utilization of services. DESIGN: To characterize current clinical practice on patients with no coexisting medical or ocular conditions, a standardized questionnaire was sent to random samples of ophthalmologists in the United States (response rate, 82.5%), Canada (66.9%), and Barcelona, Spain (70.4%), and to all ophthalmologists in Denmark (80.1%). From the United States, 526 ophthalmologists who performed cataract surgery participated in the study; there were 276 from Canada, 89 from Barcelona, and 82 from Denmark. RESULTS: Although in all 4 sites most surgeons reported that they performed A-scanning, fundus examination, and refraction routinely before surgery, significant crossnational variation was observed in preoperative ophthalmic and medical testing. While preoperative medical tests were virtually unused in Denmark, they were widely used in the other sites. A significantly higher proportion of the surgeons in the United States and Barcelona reported that they performed less than 100 extractions per year compared with surgeons in Canada and Denmark (P < .001). A significantly higher proportion of the surgeons in the United States and Canada were performing predominantly phacoextraction compared with surgeons in Denmark and Barcelona (P < .001). Both within and across sites, considerable variation in number of follow-up visits and postoperative tests was observed. CONCLUSIONS: Significant international variation in the management of healthy patients with cataracts has been observed. If less intensive care is not associated with poorer outcomes, there is the potential for less costly care of patients with cataracts. Further research identifying the most cost-effective practices is needed.

Securing silicone stents in dacryocystorhinostomy.

Silicone stents are commonly used in dacryocystorhinostomy to help maintain a patent mucosal passageway into the nose. It is not unusual for a tube to become displaced and migrate laterally (stent prolapse), and, at times, it may be difficult to reposition it. We describe how stent prolapse may be prevented by using aneurysm clips to secure the silicone stents once they are in place.

Preoperative testing for cataract surgery.

A survey was carried out to examine variation in preoperative testing of healthy patients scheduled to undergo cataract surgery in Canada. The results showed significant variations in which investigations are mandatory and in how close to the time of surgery the tests had to be done. A literature review questioning the value of routine preoperative testing is presented. Eliminating low-yield pre-operative screening tests is a safe way to reduce expenditures on cataract surgery without compromising patient care.

The "O" sign--clue to a lost lens.

The authors describe two patients who lost a hard contact lens beneath the upper lid. After a year they presented with mass lesions as the lens eroded into the lid. There were no external features to point to the correct diagnosis. In both cases a round hole in the conjunctiva over the embedded lens was noted, and the authors also noted this finding in clinical photographs from other case reports in the literature. This finding, the "O" sign, should suggest the possibility of a lost hard contact lens embedded in the upper lid.

Parasellar syndrome caused by plasma cell leukemia.

A 71-year-old man had incomplete third cranial nerve palsy caused by plasma cell leukemia and a parasellar plasmacytoma. This is the first reported case of plasma cell leukemia in which a central nervous system sign was the initial manifestation. Only one previous case of intracranial plasmacytoma associated with plasma cell leukemia has been reported. The characteristics of intracranial plasmacytomas and of plasma cell leukemia are discussed.

Lecithin:cholesterol acyltransferase deficiency.

Lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare familial disease inherited in an autosomal recessive pattern. It is characterized by a combination of plasma lipoprotein, corneal, erythrocyte and, in most patients, renal changes. The corneal changes consist of scattered stromal dots that are lipid deposits. Their composition is unique and suggests an intrinsic corneal metabolic defect. The corneal clouding is usually asymptomatic. Patients with the condition must be followed closely because renal failure may develop. We describe a patient with LCAT deficiency.