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PubMed1987

Results after beta-irradiation (106Ru/106Rh) of choroidal melanomas. Twenty years' experience.

For two decades, from 1964 to 1984, 309 patients suffering from choroidal melanoma were treated with 106Ru/106Rh applications, following confirmation of diagnosis by a variety of tests. A total of 216 patients (69.9%) were treated successfully and have been under observation for a mean period of 6.7 years after irradiation. 188 patients were followed for more than five years. Results indicate that enucleation for choroidal melanoma, especially in cases of eyes with good vision, may no longer be the standard treatment for this disease. This appears particularly true inasmuch as almost 50% of all patients with large choroidal melanomas who have enucleation die from metastases within 5 years of the operation. Therefore, conservative methods such as photocoagulation, irradiation, and microsurgical excision have been used with more or less success to destroy tumor and save a functioning eye.

Beta Particles↗
PubMed1975

Depolarization block and phase II block at the neuromuscular junction.

The effects of repeated doses of decamethonium or succinylcholine in muscles of the cat, dog, and rabbit have been examined. In particular, the relation of degree of neuromuscular block to intensity of the electrical change at the end-plate region has been found to be more consistent when the peak spatial gradient of depolarization is used as a measure of electrical effect than when the peak depolarization is used; the reason for this difference is discussed. A plot of twitch height against electrical change provides a convenient frame of reference for following the development of phase II block quantiatively. Examples presented show that the extent and kinetics of phase II block can vary considerably among species or among muscles in a given species.

Anesthesia, Intravenous↗
PubMed1994

Another look at pterygium surgery with postoperative beta radiation.

Although complications associated with the use of beta radiation after pterygium surgery can occur, the author has found the use of beta radiation to be beneficial in preventing recurrences when used with pterygium surgery. An effective surgical regime of pterygium surgery is presented. A procedure made up of steps that tend to prevent revascularization of the operative site after pterygium surgery will decrease the recurrence rate. The use of strontium 90 and the mechanism of action of beta ray therapy in treatment of the pterygium is discussed. Few complications have occurred in > 200 surgically treated cases of pterygium with postoperative beta radiation administered with a strontium 90 applicator. No cases of radiation cataract have been observed.

Beta Particles↗
PubMed2003

Long-term follow-up results of lamellar keratoplasty as a treatment for recurrent pterygium and for scleral necrosis induced by beta-irradiation.

PURPOSE: To evaluate the efficacy and safety of lamellar keratoplasty (LK) in the treatment of recurrent pterygium and of scleral necrosis induced by beta-irradiation. METHODS: A retrospective review of patients who, between 1988 and 2001, underwent LK for the above indications. Recurrence rates, tectonic outcomes, pre- and postoperative visual acuities, and complications were analyzed. RESULTS: In the recurrent pterygium group, LK was performed on 68 eyes. The mean age (mean +/- SD) at presentation was 45.1 +/- 13.7 years (range 17 to 77). The recurrence rate following LK was 5.9%, with a mean time to recurrence of 6.2 +/- 2.9 months (range 3 to 10). In all cases, the recurrence occurred above or below the lamellar grafts, and a second LK prevented any further recurrence. The mean length of follow-up was 27.1 +/- 26.6 months (range 3 to 132). The best-corrected visual acuity (BCVA) improved or remained unchanged in 65 of the 68 eyes (95.6%) but was reduced in the remaining three eyes (4.4%). In the scleral radionecrosis group, LK was performed on 30 eyes. The mean age at presentation was 67.7 +/- 10.3 years (range 37 to 85). Tectonic restoration was achieved in all patients. The mean length of follow-up was 49.0 +/- 45.1 months (range 8 to 120). The BCVA improved or remained unchanged in all patients. No significant complications were identified. CONCLUSION: Lamellar keratoplasty is a safe and effective treatment option for both recurrent pterygium and beta-irradiation-induced scleral necrosis. In our opinion, LK is the treatment of choice for multiple or aggressive recurrences of pterygium and a successful management option for scleral radionecrosis.

Adolescent↗
PubMed1985

Toxicology of 85Kr: effects of whole-body immersion exposure on newborn rats.

Newborn rats exposed to 85Kr exhibited acute radiation effects, e.g. epilation, skin scaling and abnormal development of the extremities, at beta immersion doses in excess of 1000 rad to the skin surface. The incidence of skin tumors, principally basal-cell carcinomas, was increased at all dose levels over the range from 1000 to 4750 rad. The effective skin-surface dose to induce basal-cell carcinoma in the newborn Wistar rat is apparently less than 1000 rad, the lowest dose employed in this study. No lung tumors attributable to 85Kr exposure were observed in these rats.

Animals↗
PubMed1985

Regulatory development of the interim and revised regulations for radioactivity in drinking water--past and present issues and problems.

Developing the Revised Regulations for Radioactivity in Drinking Water under the Safe Drinking Water Act requires information from all related areas and disciplines. As one step in the regulatory process, the background and history of that process as it applies to radioactivity in drinking water is described. The issues involved in developing the revised regulations are as follows: monitoring and sources of exposure, dose evaluation, health effects, engineering, economics and general policy development.

Animals↗
PubMed1985

A new type of 3H surface-contamination monitor.

A new type of 3H surface-contamination monitor has been developed which uses a windowless air proportional counter as the detector. The monitor offers several advantages. First, a high detection efficiency is obtained for 3H beta rays due to the windowless construction of the detector, permitting a minimum detection level of less than 10(-4) muCi cm-2 for surface contamination by 3H. Second, since no special gases other than room air are used as the counter gas, gas cylinders are not required thereby permitting increased convenience and lower costs. Finally, the detector is insensitive to external light due to the height discrimination of proportional counter pulses, which allows the monitor to be used in brightly illuminated places.

Beta Particles↗
PubMed1985

Experimental evaluation of a method for performing personnel beta dosimetry using multi-element thermoluminescent dosimeters.

Two multi-element thermoluminescent (TL) dosimeter designs were calibrated in a gamma field and then exposed to beta sources emitting different beta spectra. The TL readouts from the dosimeters were analyzed using an algorithm designed to enable calculation of the beta doses from the dosimeter readings without performing any beta calibrations. The results suggest that the method is promising for application in personnel beta dosimetry.

Beta Particles↗
PubMed1986

Effects of selected materials and geometries on the beta dose equivalent rate in a tissue equivalent phantom immersed in infinite clouds of 133Xe.

Most calculations of dose equivalent (D.E.) rates at 70-micron tissue depths in tissue equivalent (T.E.) phantoms from infinite clouds (radius exceeds maximum beta range in air) of 133Xe do not consider the possible effects of clothing overlays. Consequently, a series of measurements were made using a 1-mm-thick plastic scintillation detector assembly mounted in a tissue equivalent (T.E.) phantom with an overlay of 70 micron of T.E. material. This assembly was placed in an infinite cloud containing a known concentration of 133Xe. Material samples were placed at selected distances from the detector phantom, both individually and in various combinations. Pulse-height spectra resulting from beta radiations were converted to relative D.E. rates at a 70-micron tissue depth. The relative D.E. rates were reduced from values with no clothing cover by as little as 45% when placing a single thin nylon cloth 1 cm from the phantom, to 94% for a T-shirt material plus wool material plus denim placed 1/2, 1 and 3 cm, respectively, from the phantom. The results indicate that even loosely fitting clothing can have an important effect on reducing the D.E. rate. Close-fitting clothing appears to provide better protection.

Beta Particles↗
PubMed1987

An optimized computational method for determining the beta dose distribution using a multiple-element thermoluminescent dosimeter system.

This paper describes an optimization method for determining the beta dose distribution in tissue, and it describes the associated testing and verification. The method uses electron transport theory and optimization techniques to analyze the responses of a three-element thermoluminescent dosimeter (TLD) system. Specifically, the method determines the effective beta energy distribution incident on the dosimeter system, and thus the system performs as a beta spectrometer. Electron transport theory provides the mathematical model for performing the optimization calculation. In this calculation, parameters are determined that produce calculated doses for each of the chip/absorber components in the three-element TLD system. The resulting optimized parameters describe an effective incident beta distribution. This method can be used to determine the beta dose specifically at 7 mg X cm-2 or at any depth of interest. The doses at 7 mg X cm-2 in tissue determined by this method are compared to those experimentally determined using an extrapolation chamber. For a great variety of pure beta sources having different incident beta energy distributions, good agreement is found. The results are also compared to those produced by a commonly used empirical algorithm. Although the optimization method produces somewhat better results, the advantage of the optimization method is that its performance is not sensitive to the specific method of calibration.

Algorithms↗
PubMed1987

Electron dose-rate conversion factors for external exposure of the skin from uniformly deposited activity on the body surface.

Dose-rate conversion factors have been calculated for external exposure of the skin from electrons emitted by sources that are deposited uniformly on the body surface. The dose-rate factors are obtained from electron scaled point kernels developed by Berger (Be71; Be73; Be74). The dose-rate factors are calculated at depths of 4, 8, and 40 mg cm-2 below the body surface as recommended by Whitton (Wh73), and at a depth of 7 mg cm-2 as recommended in ICRP Publication 26 (ICRP77). The dependence of the dose-rate factors at selected depths on the energy of the emitted electrons is displayed. The dose-rate factors for selected radionuclides of potential importance in radiological assessments are tabulated.

Beta Particles↗
PubMed1987

Angular dependence of shallow dose from energetic electrons.

A definite angular dependence of shallow dose from energetic electrons was observed when measuring the angular response of several detectors. This angular dependence of dose appeared to be fundamental, not a detector artifact. The theoretical response of a detector is discussed and compared to measurements of shallow dose with tissue and phantom response detectors. The energy-dependent angular response of the dose observed could not be explained by simple trigonometric arguments. The response, which is backscatter-dependent, must be considered in detector design and dose measurements. It is not possible for standard detectors to follow this response.

Beta Particles↗
PubMed1988

Two methods for examining angular response of personnel dosimeters.

The American National Standard ANSI N13.11-1983 is used to test the accuracy (bias plus precision) of dosimetry processors as part of the dosimetry accreditation program of the National Voluntary Laboratory Accreditation Program (NVLAP). Section 3.8 of the ANSI N13.11-1983 standard requires that a study of the angular response of a dosimeter be carried out once, although no pass/fail criterion is given for angular response. The NVLAP accreditation program excluded Section 3.8, and thus no angular response data have been generated in an organized fashion. The objective of this project is to examine the feasibility of two alternative methods to test the angular response of personnel dosimeters. The first alternative involves static irradiations with the dosimeters at fixed angles to a radiation source. The second alternative involves dynamic irradiations with the dosimeters mounted on a rotating phantom. A Panasonic UD-802 personnel dosimetry system** was used to generate data to examine both alternatives. The results lead to two major conclusions. Firstly, Section 3.8 of the ANSI N13.11-1983 standard should be amended to require a pass/fail test for angular response. Secondly, a comparison between angular response data generated with a fixed or a rotating phantom shows that the rotating phantom is the more cost-effective method.

Algorithms↗
PubMed1988

The next decade in external dosimetry.

In recent years, a number of external dosimetry problems have been solved. However, changes in standards and legal concepts relating to the application of dosimetry results will require further enhancements in measurement techniques and philosophy in the next 10 y. The introduction of effective dose equivalent and the legal use of probability of causation will require that much greater attention be given to determination of weighted organ dose from external exposure. An imminent change--an increase in the fast neutron quality factor--will require a new round of technology development in a field that has just received a decade of close scrutiny. For the future, we must take advantage of developments in microelectronics. The use of random access memory (RAM) and metal-on-silicon (MOS) devices as detector elements, particularly for neutron dosimetry, has exciting possibilities that are just beginning to be explored. Advances in microcircuitry are leading, and will continue to lead, in the development of a new generation of small, rugged and "smart" radiation survey instruments that will make the most of detector data. It has become possible with very compact instruments to obtain energy spectra, linear-energy-transfer (LET) spectra, and quality factors in addition to the usual integrated dosimetric quantities: exposure, absorbed dose, and dose equivalent. These instruments will be reliable and easy to use. The user will be able to select the level of sophistication that is required for any specific application. Moreover, since the processing algorithms can be changed, changes in conversion factors can be accommodated with relative ease. During the next decade, the use of computers will continue to grow in value to the health physicist. Personal computers and codes designed for dosimetry applications will become prominent, providing the health physicist with the ability to perform sophisticated data reduction, spectra unfolding and even radiation modeling and transport calculations on the desk top. In the far term, the use of computers could extend to the development of sophisticated tracking systems that would follow and record the workers' movements throughout a radiation area. These data, together with information from area monitors, air samplers and personnel dosimeters, could be used to develop truly integrated dose estimates, including reconstruction of organ doses.

Beta Particles↗
PubMed1988

A small, multi-element fingertip dosimeter for beta radiation.

Many occupations involve potential exposures, directly or indirectly, to sources of beta radiation. The region of highest exposure, in many cases, will be the extremities and in particular the fingertips of people handling beta sources. Because current extremity dosimeters can significantly underestimate beta doses to the fingertips, an improved fingertip beta dosimeter was developed. The dosimeter employs a multi-element, multi-filter concept by stacking four or five thin (0.13 mm) LiF-Teflon TLDs to form the beta detector element. The entire dosimeter is approximately 1 mm thick, flexible and rugged enough for field use without interference of the user's manual dexterity. The fingertip dosimeter provides data for determining the beta energy of each exposure. The beta energy can be used to determine the TLD correction factor for converting the TLD output to beta dose. The data can be used to reconstruct the beta depth dose curve and the depth dose curve can be used to calculate the beta dose in tissue at 7 mg cm-2, for legal reporting purposes, or at any other desired depth within the range of the beta radiation. Relationships between the effective mass absorption coefficient and beta energy and between the beta correction factor and beta energy were determined for use in this study. Beta sources were fabricated for these studies, and an extrapolation chamber was used to determine reference beta doses. Tests of the fingertip dosimeter were performed by exposing it to single beta sources and to multiple beta sources. The dosimeter should be useful for monitoring exposures to beta energies ranging from 0.29-2.5 MeV.

Beta Particles↗