Radiation Protection Of Personnel Research Articles

Positron emission and single-photon emission imaging: synergy rather than competition

Some proponents of positron imaging have suggested that single-photon imaging procedures would be totally replaced by PET imaging [1–3]. Proponents and opponents of such a scenario have each argued about the relative merits of the two modalities, and the issues involved in the clinician's choice in different health-care systems [4–7]. These issues include availability of a PET alternative to a planar/SPECT procedure, regulatory approval of the radiopharmaceuticals and procedures, cost/reimbursement issues, and radiation protection for personnel. The growth of PET examinations in recent years has been impressive, although at different rates in different parts of the world. In a country where diffusion of clinical PET started early, such as the USA, the number of PET examinations increased by about 35% in the period 2005–2008, although with a declining computed annual growth rate (CAGR) from 14.5% in 2006 to 4.4% in 2008 (source: IMV, Des Plaines, IL). Where diffusion of clinical PET started more recently, as in Western Europe, the number of PET procedures increased by 82% with a smaller decline in CAGR, from 29% to 21%, over the same period (sources: Medical Options, London, UK; European Association of Nuclear Medicine). Contrary to what one would expect for PET gradually replacing single-photon imaging, this increase in PET has not been mirrored by a corresponding decrease in planar/SPECT examinations. This confirms the overall vitality of functional imaging with nuclear medicine. In fact, the only single-photon procedure that has declined consistently (by 7–8%) is ventilation/perfusion lung scanning for pulmonary embolism, clearly due to competition from multidetector spiral-CT pulmonary angiography [8] and not from PET. The number of all other planar/SPECT procedures has remained stable in Europe or has actually increased, either moderately (+2% for brain and myocardial perfusion), or markedly: +17.4% for infection/inflammation imaging, +17.5% for sentinel node scintigraphy, +42.1% for brain receptor imaging. In this pattern one can see the effects of an ongoing crossfertilization already in place between the two imaging methodologies. Transfer of PET/CT cross-sectional imaging expertise to SPECT/CT has clearly revitalized the latter for both preclinical and clinical applications [9–11]. The advantages include not only improved topographic localization compared with radionuclide-based transmission/emission imaging, but also more accurate attenuation correction making quantitation possible also with SPECT [12]. Therefore, future scenarios for nuclear medicine are taking on new perspectives, especially considering that the shortage of molybdenum-99 [13] seems now to be solved [14]. This change in perspective is reflected by a recent surge in new SPECT/CT installations; in the third quarter of 2010 a major manufacturer has seen revenues from sales of SPECT installations exceed those from PET installations for the first time in years (personal communication), a large proportion of which are multimodality SPECT/CT devices. Likewise, transfer of conventional SPECT studies to PET/CT is being explored with a synergistic flow in the opposite direction with questions such as: "How might we image infection and/or inflammation with PET/CT?" and "What would a high resolution ventilation/perfusion PET/CT lung scan look like?". PET and SPECT are synergistic for introducing new radiopharmaceuticals for both preclinical and clinical G. Mariani (*) Regional Center of Nuclear Medicine, University of Pisa Medical School, Via Roma 67, I-56100 Pisa, Italy e-mail: g.mariani@med.unipi.it

Evolution of Radiation Protection Trends ― the Malaysian Perspective

The growing application of radiation sources demands a better control and efficient radiation protection program, aimed at reducing occupational radiation exposures. In Malaysia, there are continuous efforts and challenges in further promoting radiation protection and safety. A proper, transparent and equitable procedure for competent radiation protection personnel or auditor will require continual development. By having these mechanisms, uniformity of competence and performance can be assured in the promotion of safe behaviour at all levels of the workforce utilising ionizing radiation facilities. Much of the success of occupational radiation protection programmes can be attributed on instituting controls on the radiation work. Individual monitoring service given by Secondary Standard Dosimetry Laboratory, SSDL-Nuclear Malaysia, has undergone a significant evolutionary period during the past few decades. General improvement of protection techniques and technology is expected to continue. Upgrading of the individual dose monitoring service is also highlighted. Reporting program through web based e-SSDL is regarded as a vital step to provide a user-friendly and higher level of confidence on the results generated for occupational dose monitoring of the individual monitoring service. It, thus, enhances the status of the radiation protection framework in the country.

The top ten list of challenges for radiation protection dosimetry in 2011

Lists of things are apparently very popular. One can find on the Internet top 10 lists of music, movies, sports heroes, highest mountains, most picturesque cities and so on. There are even lists of lists. Not to be left out, this Editorial proposes a list of the top 10 challenges for radiation protection dosimetry for the coming year. The items listed and their relative positions represent a very arbitrary choice on the part of the author based upon the perceived importance of the items as judged by items in the news, session titles at scientific meetings and articles published in our journal. There are some items that have been of significance and importance for many years, and a few that have moved to the forefront fairly recently. Radiation has found applications in a number of areas of technology, and new applications are constantly under development. If such a list is updated in a year or two, or in ten, it may change somewhat, but likely not by very much. So, without further ado, here is the list according to the Editor-in-Chief. Items that should have been on the list or items that should not be on the list are undoubtedly emerging in the mind of the reader. That being the case, perhaps every reader can generate their own list. Why is it necessary to have a list at all? This list-making may have some use if plans are to be made as to where precious resources are to be allocated. Radiation protection budgets are often limited, and radiation protection personnel may be expected to monitor activities in a variety of areas. So, it may be useful to keep in mind long-term problems and newly emerging areas of radiation protection.

Radiation protection practices

This study was carried out to assess the standard of personnel radiation protection practices in industrial radiography in Port Harcourt, Rivers State. A non-experimental prospective survey design was used for the study. A sample size of 11 inspection Companies and 26 radiation workers were randomly selected for the survey. The objectives of the study were to determine the standard of personnel radiation monitoring practices, training given to personnel, quality assurance practices and to assess the adequacy of the work area design used for industrial radiography. Results showed that personnel are provided with radiation monitoring devices and are routinely monitored. They undergo medical check ups and attend periodic seminars. However, majority of the personnel were not fundamentally trained in radiography prior to industrial radiography work. Regular quality assurance tests were done and the work area design was adequate. Results suggest that adequate fundamental training of personnel in general radiography prior to industrial radiography work will further improve the standard of personnel radiation protection practices in industrial radiography. Nigerian Medical Practitioner Vol. 54 (3-4) 2008: pp. 61-65

2007 Recommendations of the ICRP Change Basis for Estimation of the Effective Dose: What is the Impact on Radiation Dose Assessment of Patient and Personnel?

In radiation protection regulations the algorithm for effective dose calculation is based on Publication 60 (1990) of the International Commission on Radiological Protection (ICRP). The modifications to the tissue weighting factors in Publication 103 (2007) of the ICRP will affect the present methodology of calculating the effective dose and will also have an impact on its assessment. This paper evaluates circumstances under which the application of the new model yields relevant dose differences compared to the prevailing model. Effective doses were calculated and compared from the measured organ doses according to ICRP 60 and ICRP 103, respectively. The measurements of patient doses were carried out with an anthropomorphic phantom for thoracic and coronary CT examinations. Exposure of radiological personnel was measured based on the geometry of angiographic examinations using two anthropomorphic phantoms. The change of the weighting factor for the breast from 0.05 to 0.12 leads to a noticeable increase in the effective dose for thoracic (21 %) and coronary (31 %) CT examinations. Calculating sex-specific effective doses based on ICRP 60, the dose for coronary CT examination for women is 1.7 times higher than for men. Based on ICRP 103, the difference between female and male doses increases to a factor of 3.3. Due to the consideration of organs in the head and neck region as introduced in ICRP 103, for angiography the personnel is exposed to 24 - 50 % and 38 - 142 % higher doses with and without thyroid protection, respectively. Thereby, the official personal dosimetry will underestimate the effective dose according to ICRP 103 by a factor of 1.6 - 2.4 with thyroid protection and 1.1 - 1.4 without thyroid protection. The revision of the parameters for effective dose calculation leads to higher doses and greater sex-specific differences for radiological examinations involving exposure of the breast. This effect should be considered when justifying any radiological examination. For the personnel, the new model results in higher effective doses due to increased emphasis on the organs in the head and neck region. Hence to optimize radiation protection of personnel, the use of radiation-protective shielding for this region becomes more important.

Technical basis for using nose swab bioassay data for early internal dose assessment

One of the challenges to the dose assessment team in response to an inhalation incident in the workplace is to provide the occupational physicians, operational radiation protection personnel and line managers with early estimates of radionuclide intakes so that appropriate consequence management and mitigation can be done. For radionuclides such as Pu, where in vivo counting is not adequately sensitive, other techniques such as the measurement of removable radionuclide from the nasal airway passages can be used. At Los Alamos National Laboratory (LANL), nose swabs of the ET1 region have been used routinely as a first response to airborne Pu releases in the workplace, as well as for other radionuclides. This paper presents the results of analysing over 15 years of nose swab data, comparing these with dose assessments performed using the Bayesian methods developed at LANL. The results provide empirical support for using nose swab data for early dose assessments. For Pu, a rule of thumb is a dose factor of 0.8 mSv Bq(-1), assuming a linear relationship between nasal swab activity and committed effective dose equivalent. However, this value is specific to the methods and models used at LANL, and should not be applied directly without considering possible differences in measurement and calculation methods.

Amylase and blood cell-count hematological radiation-injury biomarkers in a rhesus monkey radiation model—use of multiparameter and integrated biological dosimetry

Effective medical management of suspected radiation exposure incidents requires the recording of dynamic medical data (clinical signs and symptoms), biological assessments of radiation exposure, and physical dosimetry in order to provide diagnostic information to the treating physician and dose assessment for personnel radiation protection records. The need to rapidly assess radiation dose in mass-casualty and population-monitoring scenarios prompted an evaluation of suitable biomarkers that can provide early diagnostic information after exposure. We investigated the utility of serum amylase and hematological blood-cell count biomarkers to provide early assessment of severe radiation exposures in a non-human primate model (i.e., rhesus macaques; n = 8 ) exposed to whole-body radiation of Co 60 -gamma rays (6.5 Gy, 40 cGy min - 1 ). Serum amylase activity was significantly elevated ( 12.3 ± 3.27 - and 2.6 ± 0.058 -fold of day zero samples) at 1 and 2-days, respectively, after radiation. Lymphocyte cell counts decreased ( ⩽ 15 % of day zero samples) 1 and 2 days after radiation exposure. Neutrophil cell counts increased at day one by 1.9 ( ± 0.38 ) -fold compared with levels before irradiation. The ratios of neutrophil to lymphocyte cell counts increased by 13 ( ± 2.66 ) - and 4.23 ( ± 0.95 ) -fold at 1 and 2 days, respectively, after irradiation. These results demonstrate that increases in serum amylase activity along with decreases of lymphocyte counts, increases in neutrophil cell counts, and increases in the ratio of neutrophil to lymphocyte counts 1 day after irradiation can provide enhanced early triage discrimination of individuals with severe radiation exposure and injury. Use of the biodosimetry assessment tool (BAT) application is encouraged to permit dynamic recording of medical data in the management of a suspected radiological casualty.

Excessive leakage radiation measured on two mobile X-ray units due to the methodology used by the manufacturer to calculate and specify the required tube shielding

During the quality control (QC) procedure of a new mobile X-ray unit, it was revealed that the leakage radiation was well in excess of the current limit of 1 mSv h(-1). As a result, this unit was returned to the vendor company and it was replaced by a new unit of the same brand and model. Leakage measurements revealed that the second unit presented the same problem. After consulting the vendor company and the tube manufacturer, it was discovered that the excessive leakage identified in these two X-ray units was not due to a defective construction, but due to the methodology with which the maximum permissible leakage and therefore the tube shielding had been determined. In this study, the implications of using such methods to the radiation protection of personnel and public are discussed.

Shielding variation effects for 250 MeV protons on tissue targets

This paper provides results of computer simulation studies with the goal to analyse issues regarding radiation protection for personnel, patients and third persons involved in hadron therapy treatment. The treatment room and the patient are modelled by simple cylindrical geometries at incident proton energies of 250 MeV. Monte Carlo simulations of the energy and angular dependence of proton, neutron and photon radiation fields and resulting ambient dose equivalent distributions outside the shielding walls are performed. In order to investigate systematic uncertainties due to the shielding materials and inherent to the computer models, various concrete compositions, densities and water contents are modelled, and the influence of simulation parameters on the results obtained is determined. Generally, good agreement is found between results provided by MCNPX and FLUKA computer codes. Variations in neutron ambient dose attenuation from -50 to +/-30% are found due to varying concrete composition. Changes in the water content of the concrete in the order of 8% may cause variations up to 20%.

EARLY-RESPONSE BIOLOGICAL DOSIMETRY???RECOMMENDED COUNTERMEASURE ENHANCEMENTS FOR MASS-CASUALTY RADIOLOGICAL INCIDENTS AND TERRORISM

The effective medical management of a suspected acute radiation overexposure incident necessitates recording dynamic medical data, measuring appropriate radiation bioassays, and estimating dose from dosimeters and radioactivity assessments in order to provide diagnostic information to the treating physician and a dose assessment for personnel radiation protection records. The accepted generic multiparameter and early-response approach includes measuring radioactivity and monitoring the exposed individual; observing and recording prodromal signs/symptoms and erythema; obtaining complete blood counts with white blood cell differential; sampling blood for the chromosome-aberration cytogenetic bioassay using the "gold standard" dicentric assay (translocation assay for long times after exposure) for dose assessment; bioassay sampling, if appropriate, to determine radioactivity contamination; and using other available dosimetry approaches. In the event of a radiological mass-casualty incident, current national resources need to be enhanced to provide suitable dose assessment and medical triage and diagnoses. This capability should be broadly based and include stockpiling reagents and devices; establishing deployable (i.e., hematology and biodosimetry) laboratories and reference (i.e., cytogenetic biodosimetry, radiation bioassay) laboratories; networking qualified reference radioactivity-counting bioassay laboratories, cytogenetic biodosimetry, and deployable hematology laboratories with the medical responder community and national radiation protection program; and researching efforts to identify novel radiation biomarkers and develop applied biological dosimetry assays monitored with clinical, deployable, and hand-held analytical systems. These research and applied science efforts should ultimately contribute towards approved, regulated biodosimetry devices or diagnostic tests integrated into a national radioprotection program.

ACCF/AHA/HRS/SCAI Clinical Competence Statement on Physician Knowledge to Optimize Patient Safety and Image Quality in Fluoroscopically Guided Invasive Cardiovascular Procedures

ACCF/AHA/HRS/SCAI Clinical Competence Statement on Physician Knowledge to Optimize Patient Safety and Image Quality in Fluoroscopically Guided Invasive Cardiovascular Procedures

Parathyroid Adenoma Radiation Dose Simulator

As the number of radioisotope localization cases increased at our facility, the pathologists expressed concern regarding radiation exposure from parathyroid specimens. The radiation safety officer was consulted to analyze personnel radiation protection issues. Analysis of simulated specimens was performed for a range of activities and masses corresponding to the values that have been observed. The radiation dose rates from these samples were measured using a Ludlum Model 14C survey meter with a Model 44-38 energy compensated GM probe and a Ludlum Model 3 Geiger counter with a Model 44-9 "pancake" style GM probe (Ludlum Measurements, Inc., Sweetwater, Texas). Additionally, 3 consecutive 10-second counts were performed using a USSC Navigator Gamma Guidance System (United States Surgical Corporation, Norwalk, CT). The per-second average readings were recorded. Our sample count-rates ranged from 139 to 2,830 counts/second. The majority of these values fell within the 100 to 1,000 count/second range typically observed during surgery. Based on our sample set, our dose rates at contact with these samples ranged from 0.17 to 4.0 mR/hour depending on the instrument, sample activity, and sample volume. The variation between count rate and dose rate for each observed volume varied linearly with activity. Based on these observed radiation doses, we concluded that there is no need to hold parathyroid specimens for 24 to 48 hours after surgical removal for handling because the typical radiation doses are quite low and would not result in significant radiation exposure to pathology personnel.

USING HIGH-CURRENT NANOSECOND LOW-ENERGY ELECTRON BEAMS FOR RADIATION STERILIZATION OF POWDERED DRUGS

Modern technological schemes of manufacturing tabletized drugs usually eliminate microbiological contamination of processed and intermediate products. Therefore, sterility of the final drugs is determined by microbiological cleanness of the initial powdered materials. Powdered drug components cannot always be sterilized by even the most effective thermal method, because the parent drugs frequently possess insufficient thermal stability. Chemical sterilization by volatile agents (ethylene oxide, ozone) is also problematic because of the risk of toxin accumulation. Under these conditions an alternative is offered by the radiation sterilization process, since ionizing radiation is a universal damaging factor for microbiological flora of any kind (fungi, bacteria, spores, viruses), while a required sterilization dose of 25 – 50 kGy (irrespective of the radiation type) usually produces no detectable physicochemical changes in the irradiated material [1]. Radiation sterilization is usually produced using -radiation from isotope sources or high-energy (above 5 MeV) electron beams possessing considerable penetration ability in condensed matter. Construction of such radiation sources involves significant expenditures for the radiation protection of personnel. As a rule, special sterilization centers are built around such sources, where the final products are sterilized in a ready-to-use packed form [2, 3]. There is certain experience in using low-energy (150 – 500 keV) electron beams for sterilization purposes. The creation and use of such radiation sources requires neither capital investment for special buildings nor large expenditures for radiation protection. These systems can be arranged and operated immediately on enterprises. A disadvantage of such radiation sources is the relatively small penetration depth of low-energy electrons in solids (not exceeding 1.5 mm in water-equivalent materials). For this reason, use of these systems is restricted to surface sterilization, mostly of films, foils, paper, and related packaging materials [2 – 7]. Nevertheless, low-energy electron beams can ensure not only surface sterilization but bulk treatment as well, provided that the objects processed admit leveling of the irradiation in depth by means of intense stirring [8] or aeration, whereby the average density of the target decreases and the effective electron penetration depth increases [9]. In resent years, nanosecond pulse low-energy electron accelerators capable of operating at a high repetition rate (50 – 400 Hz) have been developed [10, 11], which possess the advantages of long working life, small dimensions, and relatively low cost. Low-energy electron beams of nanosecond pulse duration, characterized by high absorbed radiation dose rates per pulse, can be used for the sterilization of radiation-unstable preparations (some vitamin solutions, enzymes, etc.), since the doses required for sterilization under such conditions are significantly (3 – 10 times) lower [12, 13]. One possible variant of drug powder sterilization by low-energy electron beams is implemented in an experimental setup developed at Pharmaceutical Chemistry Journal Vol. 36, No. 12, 2002

Risk of microbial contamination of iodinated contrast media on multiple use of large-volume bottles

Large-volume bottles of iodinated contrast material (CM) offer advantages over single-dose vials in respect of handling, radiation protection of personnel, cost and waste. Because non-ionic CM are considered to be susceptible to microbial contamination, the probability of such contamination was investigated under practical conditions with reference to the duration of use. Under conditions identical to those in practice, contamination was found in only about 1% of bottles examined after a single piercing. Under worst-case conditions, a maximum of 9 microorganisms/bottle was found. No pathogen multiplication was observed within 24 h in microbial challenge tests; rather, the nosocomial pathogens examined died quickly in iopromide, the only exception being Pseudomonas aeruginosa. There was not a single case of bacterial multiplication on clinical use of 500-ml infusion bottles in patients undergoing routine computed tomography, using either injection by hand or an automatic infusion device. In conclusion, the microbial count rate did not differ from that of small-volume parenterals used up immediately after piercing. To ensure an adequate safety margin for the avoidance of septicemia or pyrogenic reactions, the CM should be used within 1 examination day.

Characterisation of LiF:Cu,Mg,P (GR-200) for Personnel Thermoluminescence Dosimetry

Abstract We report the results of our dosimetric characterisation of hot-pressed GR-200 LiF:Cu,Mg,P chips for personnel radiation protection. The TL sensitivity was studied as a function of the maximum temperature of glow curve readout and heating rate. In order to achieve acceptable re-usability we recommend a maximum temperature of 240 ± 2 oC or alternatively 235 ± 5 oC, although the latter choice will lead to a significantly higher residual signal. The TL sensitivity is not a function of glow curve heating rate. We have also studied the dependence of the residual TL signal (TMAX = 240 ± 2 oC) on a large number of experimental and radiation field parameters. Our main conclusion is that the ratio of the second and subsequent readouts to first readout is, to a good approximation, independent of all parameters except for TMAX and its duration, LET and possibly the time between readouts. The dependence on LET arises from the preferential population of the high temperature peak at 270 oC in alpha particle and neutron irradiation. The use of 'unannealed' LiF:Cu,Mg,P individually calibrated dosemeters is thus possible in personnel dosimetry applications if the prior irradiation history of the dosemeters is permanently recorded and the proper corrections (of the order of 10%) are applied. This represents a serious shortcoming of the currently available dosemeters for personnel dosimetry applications.

Intermediate dose rate remote afterloading brachytherapy for intraluminal control of bronchogenic carcinoma

Forty-five patients with symptomatic proximal malignant airway disease received 128 intraluminal intermediate dose rate (IDR) brachytherapy treatments by remote afterloading technique. Multiple small catheters were bronchoscopically placed. Iridium-192 sources delivering an intermediate dose rate (200–1000 rads/hr) were guided under remote computer control. Treatment times were 1–4 hr. Fourteen of these patients also received YAG laser photoresection. External beam radiation was also given (6000 rads) to 16 patients for curative intent and (3000 rads) to 9 patients for palliative intent. Twenty recurrent disease patients were also treated, but they did not receive external irradiation. An obstruction score (OS) was developed in an attempt to quantitate the improvement in intraluminal narrowing. Patients treated with curative intent showed 66% improvement after initial therapy. Initial therapy for palliative patients showed an 84% improvement and for recurrent disease patients, 64% of luminal narrowing was seen. Patients who received laser in addition to brachytherapy showed a 70% reduction. A 67% improvement was seen in those who did not receive laser therapy. The entire group averaged a 69% improvement of narrowing. Four complications, three minor, (1 bronchospasm, and 2 episodes of transient intratreatment increased ventricular irritability) and one major (pneumothorax) were noted. The relatively short treatment times allowed most of the treatments to be performed on an outpatient basis and were well-tolerated by the patients. Forty-four of the 45 patients experienced significant symptomatic improvement. The remote afterloading technique allowed improved radiation protection for personnel.

Institutional storage and disposal of radioactive materials

Storage and disposal of radioactive materials from nuclear medicine operations must be considered in the overall program design. The storage of materials from daily operation, materials in transit, and long-term storage represent sources of exposure. The design of storage facilities must include consideration of available space, choice of material, occupancy of surrounding areas, and amount of radioactivity anticipated. Neglect of any of these factors will lead to exposure problems. The ultimate product of any manipulation of radioactive material will be some form of radioactive waste. This waste may be discharged into the environment or placed within a storage area for packaging and transfer to a broker for ultimate disposal. Personnel must be keenly aware of packaging regulations of the burial site as well as applicable federal and local codes. Fire codes should be reviewed if there is to be storage of flammable materials in any area. Radiation protection personnel should be aware of community attitudes when considering the design of the waste program.

An evaluation of the external radiation exposure dosimetry and calculation of maximum permissible concentration values for airborne materials containing 18F, 15O, 13N, 11C and 133Xe.

To better understand the dose equivalent (D.E.) rates produced by airborne releases of gaseous positron-emitting radionuclides under various conditions of cloud size, a study of the external radiation exposure dosimetry of these radionuclides, as well as negatron, gamma and x-ray emitting 133Xe, was undertaken. This included a calculation of the contributions to D.E. as a function of cloud radii, at tissue depths of 0.07 mm (skin), 3 mm (lens of eye) and 10 mm (whole body) from both the particulate and photon radiations emitted by these radionuclides. Estimates of maximum permissible concentration (MPC) values were also calculated based on the calculated D.E. rates and current regulations for personnel radiation protection (CFR84). Three continuous air monitors, designed for use with 133Xe, were evaluated for applications in monitoring air concentrations of the selected positron emitters. The results indicate that for a given radionuclide and for a cloud greater than a certain radius, personnel radiation dosimeters must respond acceptably to only the photon radiations emitted by the radionuclide to provide acceptable personnel dosimetry. For clouds under that radius, personnel radiation dosimeters must also respond acceptably to the positron or negatron radiations to provide acceptable personnel dosimetry. It was found that two out of the three air concentration monitors may be useful for monitoring air concentrations of the selected positron emitters.

Professional status of radiation protection personnel.

Professional status of radiation protection personnel. M S LittleCopyRight https://doi.org/10.2105/AJPH.61.10.1947 Published Online: August 29, 2011

A serviceable irradiator-shield device.

A need arose for a device in which a radioactive isotope (cobalt-60) could be stored, and which also could be used for irradiating insects in various research programs, or for irradiating seeds or other small objects. We have designed, and are using, the device which was custom constructed by a local machine shop at very low cost. It is safe, and can be handled without any danger that the operator will be overexposed to radiation escaping from it. Allowable leakage tolerances and requirements for radiation protection of personnel are indicated by the Atomic Energy Commission Regulations (1963). Further technical radiation information was available from Glasstone (1958), Comar (1955), Bacq and Alexander (1961), and Andrews (1961).