Norms of the Attitudes Toward Intellectual Disability Questionnaire.

BACKGROUND: The Attitudes Toward Intellectual Disability Questionnaire (ATTID) has demonstrated good psychometric qualities for measuring the attitudes of different groups of adults in the general population toward intellectual disability (ID). A significant advantage of the ATTID is that it addresses the concept of attitudes using a three-dimensional model (affective, cognitive and behavioural). To our knowledge, there are no normative data published regarding attitudes toward ID on general population-based samples. METHODS: The sample of 1605 men and women was stratified to be representative of the general adult population of Quebec. The ATTID was administered by phone interview through an independent survey firm. RESULTS: Normative data are presented as percentile scores associated with the raw score of the ATTID by gender and age categories. Analysis of the variance yielded significant differences in attitude by gender and age. The directions and the strength of these associations vary according to each of the five factors used to define attitudes. CONCLUSION: These norms will provide an essential tool to compare different groups and assess the effectiveness of various public campaigns to encourage more positive attitudes towards persons with ID. These norms would also allow international comparisons.

Public attitudes towards intellectual disability: a multidimensional perspective.

BACKGROUND: Public attitudes towards persons with intellectual disabilities (IDs) have a significant effect on potential community integration. A better understanding of these can help target service provision and public awareness programmes. OBJECTIVE: The objective of the present study is threefold: (1) describe public attitudes towards persons with ID along affective, cognitive and behavioural dimensions; (2) compare and contrast attitudes according to sex, age, education and income, as well as frequency and quality of contacts with persons with ID; and (3) ascertain whether the level of functioning has an effect on attitudes. METHODS: The Attitudes Toward Intellectual Disability Questionnaire (ATTID) was administered by phone to 1605 randomly selected adult men and women, stratified by region in the province of Québec, Canada. The ATTID uses a multidimensional perspective of attitudes that reflect affective, cognitive and behavioural dimensions. RESULTS: The results showed that public attitudes were generally positive regarding all three attitudinal dimensions. Public attitudes towards persons with ID are presented in terms of the five factors measured through the ATTID: (1) discomfort; (2) sensibility or tenderness; (3) knowledge of causes; (4) knowledge of capacity and rights; and (5) interaction. Attitude factor scores vary as a function of participant characteristics (sex, age, education and income) and the degree of knowledge about ID, the number of persons with ID known to the participants, as well as the frequency and quality of their contacts with these persons. Men had greater negative attitudes than women as regards the discomfort factor, while women had more negative attitudes regarding the knowledge of capacity and rights factor. More positive attitudes were revealed among younger and more educated participants. Attitudes were generally not associated with income. Public attitudes tended to be more negative towards people with lower functioning ID. CONCLUSION: These results yield useful information to target public awareness and education.

Risk and Quality in Brachytherapy From a Technical Perspective.

AIMS: To provide an overview of the history of incidents in brachytherapy and to describe the pillars in place to ensure that medical physicists deliver high-quality brachytherapy. MATERIALS AND METHODS: A review of the literature was carried out to identify reported incidents in brachytherapy, together with an evaluation of the structures and processes in place to ensure that medical physicists deliver high-quality brachytherapy. In particular, the role of education and training, the use of process and technical quality assurance and the role of international guidelines are discussed. RESULTS: There are many human factors in brachytherapy procedures that introduce additional risks into the process. Most of the reported incidents in the literature are related to human factors. Brachytherapy-related education and training initiatives are in place at the societal and departmental level for medical physicists. Additionally, medical physicists have developed process and technical quality assurance procedures, together with international guidelines and protocols. Education and training initiatives, together with quality assurance procedures and international guidelines may reduce the risk of human factors in brachytherapy. CONCLUSION: Through application of the three pillars (education and training; process control and technical quality assurance; international guidelines), medical physicists will continue to minimise risk and deliver high-quality brachytherapy treatments.

Accuracy of liver ablation zone prediction in a single 2450MHz 100 Watt generator model microwave ablation system: An in human study.

PURPOSE: To compare manufacturer provided predictions and realized ablation dimensions in the liver using one 2450MHz 100 Watt generator model microwave ablation (MWA) system. MATERIALS AND METHOD: Between 1/1/2015 and 2/1/2018, MWAs were performed in 86 patients who underwent a total of 103 MWAs with a single MWA system. There were 64 men and 22 women with a mean age of 63.9±9.9 (SD) years (range: 30-88 years). Demographic, procedural, and outcomes data was recorded. The manufacturer predicted ablation zone sizes in three dimensions (anterior-posterior [AP], transverse [TR], and cranial caudal [CC]) were recorded and then compared to the actual ablation zone sizes at one month follow-up imaging. RESULTS: MWAs were most commonly performed to treat hepatocellular carcinoma (92/103, 89.3%). Dividing the actual ablation size by the manufacturer prediction in the AP, TR, and CC directions resulted in a mean of 88.3±20.6 (SD) % (range: 33.3-156.4%), 80.2±26.5 (SD) % (range: 29.6-182.9%), and 86.7±25.1 (SD) % (range: 37-186.1%), respectively. The realized AP direction was statistically closer to the manufacturer prediction than the TR (P<0.01). Ablation Watt setting of 100 Watts resulted in more accurate predictions than the 75 or 45 Watt settings in the AP direction (P=0.03). CONCLUSIONS: This 2450MHz 100 Watt generator MWA system manufacturer provided model fairly accurately predicts ablation zone dimensions, but tends to over predict realized dimensions in this mainly hepatocellular carcinoma, and therefore cirrhotic, cohort. The TR is the most inaccurately predicted dimension and manufacturer predictions appear to be best in the 100W setting, important aspects for interventionalists to consider during ablation planning and execution.

Dandy-Walker-Like Malformation in a Free-Ranging Atlantic Harbour Seal Pup (Phoca vitulina concolor).

An 88.5 cm long, 12.9 kg, 3-week-old stranded male Atlantic harbour seal (Phoca vitulina concolor) presented with cerebellar ataxia, delayed postural reactions, hyperaesthesia and nystagmus. The skull was enlarged and domed. Ultrasound through a persistent fontanelle in the frontal bone revealed hydrocephalus. Magnetic resonance imaging showed diffuse enlargement of the ventricular system, an absent cerebellar vermis, hypertrophy of the choroid plexus of the fourth ventricle and enlargement of the caudal fossa. Throughout rehabilitation, the seal failed to achieve milestones critical for successful release or placement in a managed care facility, including the ability to feed independently and haul out. Three months into rehabilitation it began to regurgitate and staff had difficulty administering food to the seal. The seal was euthanized due to a poor prognosis. Post-mortem examination confirmed a) aplasia of the dorsal cerebellar vermis and hypoplasia of the most dorsal portions of the right and left cerebellar hemispheres, b) severe, diffuse, congenital communicating hydrocephalus, and c) aplasia of the interthalamic adhesion and corpus callosum. This case represents the first report of Dandy-Walker-like malformation (DWLM) in a marine mammal and illustrates the importance of advanced imaging and thorough post-mortem examination in free-ranging pinnipeds that strand with evidence of neurological disease.

[Public health surveillance and role of administrative data]. / Importance de la surveillance en santé publique et utilité des données administratives.

BACKGROUND: Public health surveillance constitutes an important activity since it helps in identifying health needs through data collection, and contributes to decision making and actions by analyzing and interpreting data and communicating key results. METHODS: This paper presents a discussion on the concept of public health surveillance, its objectives and its historical evolution. It deals with the importance of surveillance systems while describing their components and challenges. In addition, the authors point out the importance of administrative data as a relevant source for the surveillance of public health problems, particularly chronic diseases and risk factors. RESULTS: This theoretical discussion leads to the proposal of a conceptual model for surveillance systems, which integrates implementation and evaluation. CONCLUSION: This article provides a summary of the concept of public health surveillance and underlines the general aspects to be considered by the managers of surveillance systems. It also discusses the use of administrative data for surveillance.

Probing microtubules polarity in mitotic spindles in situ using Interferometric Second Harmonic Generation Microscopy.

The polarity of microtubules is thought to be involved in spindle assembly, cytokinesis or active molecular transport. However, its exact role remains poorly understood, mainly because of the challenge to measure microtubule polarity in intact cells. We report here the use of fast Interferometric Second Harmonic Generation microscopy to study the polarity of microtubules forming the mitotic spindles in a zebrafish embryo. This technique provides a powerful tool to study mitotic spindle formation and may be directly transferable for investigating the kinetics and function of microtubule polarity in other aspects of subcellular motility or in native tissues.

[Poverty and sociocultural factors in the use of maternal health services in Ivory Coast]. / Pauvreté et déterminants socioculturels de l'utilisation des services de santé maternelle en Côte d'Ivoire.

BACKGROUND: Better health for populations is linked to the adequate access to health services. This is particularly important in developing countries, where a number of economic, social, and geographic barriers exist. Pregnant women are particularly at risk, as they have many health needs and problems. In addition, the use of maternal health services is particularly influenced by economic and socio-cultural factors. Therefore, we intended to appreciate the association between poverty, socio-cultural factors and use of maternal health services in Ivory Coast. METHODS: For this study, our data were from the demographic and health survey in Ivory Coast in 1998. We used the logistic regression models to analyze the relation between poverty, socio-cultural factors and use of services (antenatal care, type of delivery). RESULTS: 62.4% of women used antenatal care adequately and 48.9% delivered in good conditions. Poverty is strongly linked to the use of services whatever the socio-cultural and demographic aspects are, with the poor using less services than the richer. Concerning the impact of socio-cultural characteristics, women living alone or with one adult (OR=1.60; 95% IC=1.06-2.42), those who are Christian (OR=1.83; 95% IC=1.25-2.67) or Akan are more likely to have adequate antenatal care than women living with 5 adults or more, having traditional or no religion, and those who are Senoufo or non Ivorian. Besides, when the number of children increases, they are less likely to consult. Primiparous, Christians (OR=2.45; 95% IC=1.68-3.59) or Muslims (OR=1.73; 95% IC=1.10-2.72) are more likely to deliver in a health center with a qualified assistance. CONCLUSION: Poverty has a negative effect on the use of maternal services but one should also take into account certain socio-cultural characteristics, namely number of adults in the household, parity, ethnicity and religion. While reducing poverty, it appears important to involve family members and religious or ethnic leaders in order to improve this use.

Long-term results for Stage IIIB cervical cancer patients receiving external beam radiotherapy combined with either HDR (252)Cf or HDR (60)Co intracavitary brachytherapy.

PURPOSE: The aim of this work was to compare the long-term curative effects and complications of patients diagnosed with cervical cancer International Federation of Gynecology and Obstetrics IIIB (n = 430) as treated with Californium-252 ((252)Cf) or cobalt-60 ((60)Co) intracavitary brachytherapy (ICBT) combined with external beam radiotherapy (EBRT). METHODS AND MATERIALS: Cervical cancer cases with a history of treatment with (252)Cf or (60)Co ICBT combined with EBRT were selected from the Lithuanian National Cancer Institute database. Complications and second primary malignancies were compared in both patients groups. Estimates of the 5-, 10-, and 15-year overall survival and disease-free survival rates were computed with the Kaplan-Meier method and a Cox proportional hazards model applied using STATA software. RESULTS: At 5, 10, and 15 years, the overall survival rates were 46.9%, 39.3%, and 34.6% for the (252)Cf group and 35.4%, 26.9%, and 22.5% for the (60)Co group (p = 0.004), respectively. The disease-free survival rates were 42.1%, 35.0%, and 31.0% for the (252)Cf group and 32.0%, 25.1%, and 21.4% for the (60)Co group (p = 0.009), respectively. Histopathologic type of adenocarcinoma increased the risk of death for the (252)Cf group (hazard ratio 3.62). Histopathologic tumor type (hazard ratio 7.48) and recurrence (hazard ratio 2.83) were factors that statistically and significantly influenced the patient prognosis for the (60)Co group. CONCLUSIONS: Applying (252)Cf ICBT with EBRT was effective for International Federation of Gynecology and Obstetrics IIIB cervical cancer patients. Moreover, long-term followup data demonstrated higher survival rates in patients treated with (252)Cf ICBT than (60)Co ICBT. Complications in patients treated with neutron ICBT were not more frequent or severe than those treated with (60)Co ICBT.

Shielding evaluation of a medical linear accelerator vault in preparation for installing a high-dose rate 252Cf remote afterloader.

In support of the effort to begin high-dose rate 252Cf brachytherapy treatments at Tufts-New England Medical Center, the shielding capabilities of a clinical accelerator vault against the neutron and photon emissions from a 1.124 mg 252Cf source were examined. Outside the clinical accelerator vault, the fast neutron dose equivalent rate was below the lower limit of detection of a CR-39 etched track detector and below 0.14 +/- 0.02 muSv h(-1) with a proportional counter, which is consistent, within the uncertainties, with natural background. The photon dose equivalent rate was also measured to be below background levels (0.1 muSv h(-1)) using an ionisation chamber and an optically stimulated luminescence dosemeter. A Monte Carlo simulation of neutron transport through the accelerator vault was performed to validate measured values and determine the thermal-energy to low-energy neutron component. Monte Carlo results showed that the dose equivalent rate from fast neutrons was reduced by a factor of 100,000 after attenuation through the vault wall, and the thermal-energy neutron dose equivalent rate would be an additional factor of 1000 below that of the fast neutrons. Based on these findings, the shielding installed in this facility is sufficient for the use of at least 5.0 mg of 252Cf.

Prevalence estimates of diabetes and of other cardiovascular risk factors in the two largest Algonquin communities of Quebec.

OBJECTIVE: To compare the prevalence of non-insulin-dependent diabetes mellitus (NIDDM) in the two largest Algonquin communities of Quebec (Canada) with that of other native groups and to describe the different patterns of NIDDM and other cardiovascular risk markers in these communities (River Desert [RD] and Lac Simon [LS]). RESEARCH DESIGN AND METHODS: The population-based study targeted all residents aged 15 years and older. In the age-group considered here (30-64 years), there were 480 eligible subjects and 299 participants (50.8% in RD and 86.9% in LS). All except those with confirmed diabetes underwent an oral glucose tolerance test. Serum triglyceride and lipoprotein cholesterol levels, blood pressure, body mass index (BMI), and waist-to-hip ratio (WHR) were measured. RESULTS: The age-standardized (world population) prevalence of NIDDM in women was twice as high in LS as in RD (48.6% vs. 23.9%). In men, it was 23.9% in LS and 16.3% in RD. Upper-body obesity followed the same pattern. In contrast, high-risk serum low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels were significantly more prevalent in RD than in LS, particularly among men. The rate of high blood pressure was twice as high in men as in women, with little community differences. When we controlled for age, sex, diabetic, and obesity status, mean fasting serum glucose remained significantly higher triglycerides and LDL cholesterol lower in LS than in RD. There was also an independent community effect on WHR but no on BMI. CONCLUSIONS: The prevalence of NIDDM in LS women reaches the rate observed in Pima Indian women. The observed differences between two Algonquin communities suggest a highly heterogeneous pattern of NIDDM and cardiovascular disease risk factors in Amerindian populations, even within a given tribe and a limited geographic area.

Fetal dose measurements and shielding efficiency assessment in a custom setup of (192)Ir brachytherapy for a pregnant woman with breast cancer.

PURPOSE: To assess the radiation dose to the fetus of a pregnant patient undergoing high-dose-rate (HDR) (192)Ir interstitial breast brachytherapy, and to design a new patient setup and lead shielding technique that minimizes the fetal dose. METHODS: Radiochromic films were placed between the slices of an anthropomorphic phantom modeling the patient. The pregnant woman was seated in a chair with the breast over a table and inside a leaded box. Dose variation as a function of distance from the implant volume as well as dose homogeneity within a representative slice of the fetal position was evaluated without and with shielding. RESULTS: With shielding, the peripheral dose after a complete treatment ranged from 50 cGy at 5 cm from the caudal edge of the breast to <0.1 cGy at 30 cm. The shielding reduces absorbed dose by a factor of two near the breast and more than an order of magnitude beyond 20 cm. The dose is heterogeneous within a given axial plane, with variations from the central region within 50%. Interstitial HDR (192)Ir brachytherapy with breast shielding can be more advantageous than external-beam radiotherapy (EBRT) from a radiation protection point of view, as long as the distance to the uterine fundus is higher than about 10 cm. Furthermore, the weight of the shielding here proposed is notably lower than that needed in EBRT. CONCLUSIONS: Shielded breast brachytherapy may benefit pregnant patients needing localized radiotherapy, especially during the early gestational ages when the fetus is more sensitive to ionizing radiation.

A round-robin gamma stereotactic radiosurgery dosimetry interinstitution comparison of calibration protocols.

PURPOSE: Absorbed dose calibration for gamma stereotactic radiosurgery is challenging due to the unique geometric conditions, dosimetry characteristics, and nonstandard field size of these devices. Members of the American Association of Physicists in Medicine (AAPM) Task Group 178 on Gamma Stereotactic Radiosurgery Dosimetry and Quality Assurance have participated in a round-robin exchange of calibrated measurement instrumentation and phantoms exploring two approved and two proposed calibration protocols or formalisms on ten gamma radiosurgery units. The objectives of this study were to benchmark and compare new formalisms to existing calibration methods, while maintaining traceability to U.S. primary dosimetry calibration laboratory standards. METHODS: Nine institutions made measurements using ten gamma stereotactic radiosurgery units in three different 160 mm diameter spherical phantoms [acrylonitrile butadiene styrene (ABS) plastic, Solid Water, and liquid water] and in air using a positioning jig. Two calibrated miniature ionization chambers and one calibrated electrometer were circulated for all measurements. Reference dose-rates at the phantom center were determined using the well-established AAPM TG-21 or TG-51 dose calibration protocols and using two proposed dose calibration protocols/formalisms: an in-air protocol and a formalism proposed by the International Atomic Energy Agency (IAEA) working group for small and nonstandard radiation fields. Each institution's results were normalized to the dose-rate determined at that institution using the TG-21 protocol in the ABS phantom. RESULTS: Percentages of dose-rates within 1.5% of the reference dose-rate (TG-21+ABS phantom) for the eight chamber-protocol-phantom combinations were the following: 88% for TG-21, 70% for TG-51, 93% for the new IAEA nonstandard-field formalism, and 65% for the new in-air protocol. Averages and standard deviations for dose-rates over all measurements relative to the TG-21+ABS dose-rate were 0.999±0.009 (TG-21), 0.991±0.013 (TG-51), 1.000±0.009 (IAEA), and 1.009±0.012 (in-air). There were no statistically significant differences (i.e., p>0.05) between the two ionization chambers for the TG-21 protocol applied to all dosimetry phantoms. The mean results using the TG-51 protocol were notably lower than those for the other dosimetry protocols, with a standard deviation 2-3 times larger. The in-air protocol was not statistically different from TG-21 for the A16 chamber in the liquid water or ABS phantoms (p=0.300 and p=0.135) but was statistically different from TG-21 for the PTW chamber in all phantoms (p=0.006 for Solid Water, 0.014 for liquid water, and 0.020 for ABS). Results of IAEA formalism were statistically different from TG-21 results only for the combination of the A16 chamber with the liquid water phantom (p=0.017). In the latter case, dose-rates measured with the two protocols differed by only 0.4%. For other phantom-ionization-chamber combinations, the new IAEA formalism was not statistically different from TG-21. CONCLUSIONS: Although further investigation is needed to validate the new protocols for other ionization chambers, these results can serve as a reference to quantitatively compare different calibration protocols and ionization chambers if a particular method is chosen by a professional society to serve as a standardized calibration protocol.

The dexamethasone suppression test in an elderly population.

Impaired suppression of plasma cortisol levels following a single midnight dose of dexamethasone has been well documented in a large subgroup of depressed patients. To interpret meaningfully this 24-hr dexamethasone suppression test in geriatric patients, the effect of age per se was examined by comparing the pattern and duration of suppression in ten healthy elderly and ten healthy young subjects. Advanced age did not appear to affect the overnight dexamethasone suppression in healthy humans and should not invalidate the use of dexamethasone suppression test as a laboratory tool in the diagnosis and investigation of depression.

Dexamethasone suppression test and cortisol circadian rhythm in primary degenerative dementia.

Before the dexamethasone suppression test (DST) can be accepted as a valid diagnostic tool for differentiating depression from dementia, it must be demonstrated that dementing illnesses per se are not associated with a positive DST. The authors studied cortisol circadian rhythm and the overnight DST in 15 nondepressed patients with advanced primary degenerative dementia and 15 normal control subjects. Seven dementia patients and no control patients were DST positive. The DST-positive dementia patients had a blunted predexamethasone circadian cortisol rhythm. These results cast doubt on the utility of the DST in diagnosing depression that complicates advanced primary degenerative dementia.

Impact of a false positive blood culture result on the management of febrile children.

OBJECTIVE: To evaluate the impact of a preliminary positive blood culture result, subsequently confirmed to be a false positive blood culture result on rate of hospitalization, antibiotic therapy and use of microbiologic tests. DESIGN: Retrospective chart review. PATIENTS AND METHODS: Children between 1 month and 18 years old on whom a blood culture was performed were eligible, excluding those with an underlying condition for whom a false positive blood culture may be difficult to assess. During the 1-year study period 9959 blood cultures were performed of which 778 (7.8%) produced growth. Charts of 81 patients with a false positive blood culture were reviewed and compared with those of 162 patients with a true negative blood culture. Patients already hospitalized when blood culture was drawn (n = 24) were analyzed separately from those who were not (n = 219). Among these, patients were divided into those who were followed as outpatients (n = 104) and hospitalized (n = 115). RESULTS: Both groups (false positive vs. true negative) were comparable for age, sex, temperature at consultation, white blood cell count and illness severity. Twenty-six percent of patients followed as outpatients who had a false positive blood culture were hospitalized because of a preliminary positive blood culture result. Among patients hospitalized at the initial assessment, the frequency of antibiotic therapy (91% vs. 71%, P < 0.01), the frequency of use of intravenous antibiotics (80% vs. 58%, P < 0.01) and the percentage of unwarranted antibiotic prescription (13% vs. 0%, P < 0.01) were significantly greater in the false positive group than in the true negative group. The same results were found for each of these outcomes among the group of patients followed as outpatients (61% vs. 28%, P < 0.01, 17% vs. 0%, P < 0.01 and 39% vs. 0%, P < 0.01) for false positive vs. true negative, respectively. Patients with false positive blood cultures had more blood cultures drawn subsequently (P < 0.01). Children already hospitalized when the blood culture was obtained did not show significant differences in main outcomes. CONCLUSIONS: False positive blood culture results generate unnecessary hospitalizations, antibiotic therapy and use of microbiologic tests.

Measurements and calculations of thermal neutron fluence rate and neutron energy spectra resulting from moderation of 252Cf fast neutrons: applications for neutron capture therapy.

252Cf is a neutron emitting radioisotope which has promise for both standard brachytherapy and neutron capture enhanced brachytherapy. In this study, experimental measurements and calculations were used to determine the thermal neutron fluence rate, phi(th) [n cm(-2) s(-1) mg(-1)], in the vicinity of 252Cf applicator tube (AT) type sources. Results of these measurements were confirmed with Monte Carlo calculations performed in a distributed manner on multiple workstations using MCNP. Three studies were executed: (1) relative phi(th) as a function of distance from a 252Cf AT source in an A-150 tissue equivalent plastic phantom using thermoluminescent dosimeters (TLDs) of varying 6Li/Li enrichment, (2) phi(th) measured with gold foils in a 114 liter water phantom 5 cm from two 252Cf AT sources, and (3) calculations of the impact of phantom material composition (e.g., A-150, water, brain, muscle) on phi(th) from moderated 252Cf fast neutrons. TLD results and Monte Carlo calculations in A-150 of relative phi(th) typically agreed within 1% and at most differed by 3% for distances from 1 to 6 cm. Foil measurements followed the ASTM E 262-86e protocol, and the ratio of activated plain and Cd encased gold foils (7.31) agreed well with the calculated ratio (7.26). Measured phi(th) at 5 cm (1.70+/-0.10 x 10(7) n cm(-2) s(-1) mg(-1)) was 10% greater than that determined using MCNP (1.55+/-0.12 x 10(7) n cm(-2) s(-1) mg(-1)), but was within the combined uncertainties. Compared with A-150 at a distance of 1 cm, phi(th) was 20%, 22%, and 32% less for water, brain, and muscle, respectively; these ratios decreased to 16%, 16%, and 24% less, respectively, at a distance of 5 cm from the source in a 15 cm diameter phantom. Comparisons of these results generally agreed with those in the literature for a value of 2 x 10(7) n cm(-2) s(-1) mg(-1) in water at 3 cm.

Neutron dosimetry for a general 252Cf brachytherapy source.

This paper extends previous work to characterize neutron dosimetry in the vicinity of 252Cf brachytherapy sources. A general source is examined with an arbitrary length, diameter, and encapsulation using Monte Carlo methods. Fast neutron dosimetry and thermal neutron fluence rates were determined in a variety of clinically relevant media of varying dimensions. Applicator Tube, point source, high dose rate VariSource, and high dose rate muSelectron source geometries were analyzed. Fast neutron dosimetry was relatively independent of encapsulation thickness for an assortment of encapsulation materials less than 2 mm thick. Large variations in phantom size made minimal differences in the fast neutron dose close to the source. Specific source geometries were compared with dosimetry obtained from a simplified point model. The consequence of these results is a convenient means of accurately predicting clinical fast neutron dosimetry characteristics around a general 252Cf brachytherapy source in a variety of media without requiring neutron transport. Thermal neutron fluence rates were determined for a variety of source encapsulation materials, encapsulation thicknesses, and phantom sizes. At a distance of 3 cm from the source center, the thermal neutron fluence rate for a 30 cm diameter phantom was a 2.65 times greater than for a 10 cm diameter water phantom. These results demonstrate 252Cf thermal neutron fluence rate is relatively independent of encapsulation thickness and composition, yet highly dependent on hydrogen mass density and phantom size for phanta with diameters <30 cm.

Burst calculations for 252Cf brachytherapy sources.

Due to helium production following alpha decay, it is necessary to demonstrate the structural integrity of new 252Cf sources at elevated temperatures for special form certification by the U.S. Department of Transportation. Effects of temperature, capsule composition, and capsule dimensions are examined and reduced to a simple mathematical model. This highly conservative model assumes that all gas products leaving the radioactive source wire are retained by the capsule, and upon elevation to a temperature of 800 degrees C the capsule exhibits negligible expansion or change in internal volume and no increase in gas-phase components due to vaporization of spontaneous fission products. The calculated maximum loadings for the ORNL-made Applicator Tube and three proposed high dose rate 252Cf sources encapsulated in Pt/Ir-10% (VariSource, microSelectron classic, and a novel design) were 10.8, 0.508, 0.708, and 2.12 mg 252Cf, respectively.

Dosimetry for 252Cf neutron emitting brachytherapy sources: protocol, measurements, and calculations.

The mixed-field dosimetry for 252Cf Applicator Tube (AT) type medical sources available from Oak Ridge National Laboratory (ORNL) has been characterized using ionization chambers, a GM counter, and Monte Carlo methods. Unlike the AAPM Task Group No. 43 (TG-43), specification of dose to muscle instead of water is recommended for clinical dosimetry of 252Cf medical sources. A dosimetry protocol similar to ICRU 45 was formulated with parameters determined specifically for 252Cf brachytherapy. Comparisons of experimental and calculative dosimetry results with Colvett et al. [Phys. Med. Biol. 17, 356-364 (1972)] and Krishnaswamy [Phys. Med. Biol. 17, 56-63 (1972)] were performed, and correction factors were determined to compare the different dosimetry formalisms. Using a Maxwellian model for the 252Cf neutron energy spectrum, kerma relative to muscle was determined for a variety of materials, and compared with relative kermas for external neutron beams of three different energies. Neutron isodose distributions and data necessary for clinical implementation of 252Cf AT sources are also presented.