An updated radiation protection program prospectus based on 20 years of data describing program drivers and activities

In 1992, the University of Texas Health Science Center at Houston (UTHSCH) Radiation Safety Program began assembling data on a monthly basis that described various program drivers and associated activities. At the end of calendar year 2002, a decade of data had been collected, so the information was summarized into a novel program prospectus, displaying various program indicator parameters in a format similar to that used in a commercial enterprise prospectus provided to potential investors. The consistent formatting of the data afforded a succinct and easily digestible snapshot of program activities and trends. Feedback from various program stakeholders, even those unfamiliar with radiation safety matters, was overwhelmingly positive. By the end of 2012, a total of 20 years of data had been collected, so an updated and slightly modified prospectus was created. The summary document has helped to describe the drivers of the program, revealed some interesting trends, and has aided in maintaining program support even in challenging economic times. The data summary has also proved to be useful in making future projections regarding program needs.

Tissue-engineered, hydrogel-based endothelial progenitor cell therapy robustly revascularizes ischemic myocardium and preserves ventricular function

OBJECTIVES

Cell-based angiogenic therapy for ischemic heart failure has had limited clinical impact, likely related to low cell retention (<1%) and dispersion. We developed a novel, tissue-engineered, hydrogel-based cell-delivery strategy to overcome these limitations and provide prolonged regional retention of myocardial endothelial progenitor cells at high cell dosage.

METHODS

Endothelial progenitor cells were isolated from Wistar rats and encapsulated in fibrin gels. In vitro viability was quantified using a fluorescent live-dead stain of transgenic enhanced green fluorescent protein(+) endothelial progenitor cells. Endothelial progenitor cell-laden constructs were implanted onto ischemic rat myocardium in a model of acute myocardial infarction (left anterior descending ligation) for 4 weeks. Intramyocardial cell injection (2 × 10(6) endothelial progenitor cells), empty fibrin, and isolated left anterior descending ligation groups served as controls. Hemodynamics were quantified using echocardiography, Doppler flow analysis, and intraventricular pressure-volume analysis. Vasculogenesis and ventricular geometry were quantified. Endothelial progenitor cell migration was analyzed by using endothelial progenitor cells from transgenic enhanced green fluorescent protein(+) rodents.

RESULTS

Endothelial progenitor cells demonstrated an overall 88.7% viability for all matrix and cell conditions investigated after 48 hours. Histologic assessment of 1-week implants demonstrated significant migration of transgenic enhanced green fluorescent protein(+) endothelial progenitor cells from the fibrin matrix to the infarcted myocardium compared with intramyocardial cell injection (28 ± 12.3 cells/high power field vs 2.4 ± 2.1 cells/high power field, P = .0001). We also observed a marked increase in vasculogenesis at the implant site. Significant improvements in ventricular hemodynamics and geometry were present after endothelial progenitor cell-hydrogel therapy compared with control.

CONCLUSIONS

We present a tissue-engineered, hydrogel-based endothelial progenitor cell-mediated therapy to enhance cell delivery, cell retention, vasculogenesis, and preservation of myocardial structure and function.

How the University of Texas system responded to the need for interim storage of low-level radioactive waste materials

Faced with the prospect of being unable to permanently dispose of low-level radioactive wastes (LLRW) generated from teaching, research, and patient care activities, component institutions of the University of Texas System worked collaboratively to create a dedicated interim storage facility to be used until a permanent disposal facility became available. Located in a remote section of West Texas, the University of Texas System Interim Storage Facility (UTSISF) was licensed and put into operation in 1993, and since then has provided safe and secure interim storage for up to 350 drums of dry solid LLRW at any given time. Interim storage capability provided needed relief to component institutions, whose on-site waste facilities could have possibly become overburdened. Experiences gained from the licensing and operation of the site are described, and as a new permanent LLRW disposal facility emerges in Texas, a potential new role for the storage facility as a surge capacity storage site in times of natural disasters and emergencies is also discussed.

Staffing benchmarks: a model for determining how many security officers are enough

The authors describe the development of a model which assists with answering the question, "for a facility with certain characteristics, what would be the industry average number of security FTE's?" Through the use of multiple regression analysis using actual field data, an objective means of making this determination is possible, they report.

Surge capacity volunteer perspectives on a field training exercise specifically designed to emphasize likely roles during a disaster response

Experience gained from involvement in a number of emergency response activities since September 2001 in Texas indicated that the likely roles of statewide medical reserve corps units typically included aspects such as crowd control, registration and tracking, and information management. The need for training specifically focused on these likely roles became apparent. A novel field training exercise was developed that specifically focused on these likely roles. The exercise centered on a scenario involving the surreptitious placement of radioactivity in high traffic areas across the country, resulting in the contamination of large numbers of individuals. Because the source of the contamination was unknown, surge capacity contamination screening and data collection centers became necessary. Feedback collected from drill participants was measured to be overwhelmingly positive, with the vast majority of participants indicating a marked improvement in their understanding of their likely roles in a disaster of this type. The approach used in this training effort may be of use to other disaster surge capacity organizations as part of their strategic planning efforts as a means of ensuring that individuals involved in response activities possess familiarity with their likely roles during a wide scale public health disaster event.

Risk communication considerations to facilitate the screening of mass populations for potential contamination with radioactive material

Experience gained during a field training exercise with a Medical Reserve Corps unit on the screening of large groups of individuals for possible contamination with radioactive material revealed that while exercise participants were generally attentive to the proper use of protective equipment and detectors, they tended to overlook important basic risk communications aspects. For example, drill participants did not actively communicate with the persons waiting in line for screening, a step which would provide re-assurance, possibly minimize apprehension, and would clarify expectations. When questioned on this issue of risk communication, drill participants were often able to craft ad hoc messages, but the messages were inconsistent and likely would not have significantly helped diminish anxiety and maintain crowd control. Similar difficulties were encountered regarding messaging for persons determined to be contaminated, those departing the screening center, and those to be delivered to the media. Based on these experiences, the need for a suggested list of risk communication points was identified. To address this need, a set of risk communication templates were developed that focused on the issues likely to be encountered in a mass screening event. The points include issues such as the importance of remaining calm, steps for minimizing possible intake or uptake, considerations for those exhibiting acute injuries, expected screening wait times, the process to be followed and the information to be collected, the process to be undertaken for those exhibiting contamination, and symptoms to watch for after departure. Drill participants indicated in follow-up discussions that such pre-established risk communication templates would serve to enhance their ability to assist in times of emergency and noted the potential broader applicably of the approach for use in responses for other disasters types as well.

Situational photographic postings for enhancing the proper operation of infrequently utilized x-ray devices

Radiation safety surveillance activities conducted at The University of Texas Health Science Center at Houston indicated that x-ray devices were not being operated properly in settings where the device was used infrequently and where there were high demands of other job responsibilities. This situation was considered to be a possible precursor to the delivery of unnecessary dose to patients and workers and poor diagnostic image quality. To enhance the proper operation of such devices, photographic reminders customized for each use setting were created and posted in the rooms near the x-ray equipment. Each poster consisted of operators and patients exhibiting proper techniques while using appropriate protective equipment. The photographs were captured digitally and then augmented with brief informational textboxes that highlighted key aspects. Verbal feedback from the user community after reviewing these simple images has been very positive, as many operators indicated that work demands impacted their ability to thoroughly reread instrument operating manuals prior to use. Therefore, the capturing of a simple situational photograph inclusive of the persons actually using the unit can serve as a powerful reminder of the desired and safe means of collecting quality x-ray images while avoiding unnecessary radiological exposure to health care professionals and patients.

Validation of orthopaedic bench models for trauma surgery

The aim of this study was to validate the use of three models of fracture fixation in the assessment of technical skills. We recruited 21 subjects (six experts, seven intermediates, and eight novices) to perform three procedures: application of a dynamic compression plate on a cadaver porcine model, insertion of an unreamed tibial intramedullary nail, and application of a forearm external fixator, both on synthetic bone models. The primary outcome measures were the Objective Structural Assessment of technical skills global rating scale on video recordings of the procedures which were scored by two independent expert observers, and the hand movements of the surgeons which were analysed using the Imperial College Surgical Assessment Device. The video scores were significantly different for the three groups in all three procedures (p < 0.05), with excellent inter-rater reliability (alpha = 0.88). The novice and intermediate groups specifically were significantly different in their performance with dynamic compression plate and intramedullary nails (p < 0.05). Movement analysis distinguished between the three groups in the dynamic compression plate model, but a ceiling effect was demonstrated in the intramedullary nail and external fixator procedures, where intermediates and experts performed to comparable standards (p > 0.6). A total of 85% (18 of 21) of the subjects found the dynamic compression model and 57% (12 of 21) found all the models acceptable tools of assessment. This study has validated a low-cost, high-fidelity porcine dynamic compression plate model using video rating scores for skills assessment and movement analysis. It has also demonstrated that Synbone models for the application of and intramedullary nail and an external fixator are less sensitive and should be improved for further assessment of surgical skills in trauma. The availability of valid objective tools of assessment of surgical skills allows further studies into improving methods of training.

Identifying the cellular basis for reimplantation failure in repair of the rotator cuff

We examined cultured osteoblasts derived from paired samples from the greater tuberosity and acromion from eight patients with large chronic tears of the rotator cuff. We found that osteoblasts from the tuberosity had no apparent response to mechanical stimulation, whereas those derived from the acromion showed an increase in alkaline phosphatase activity and nitric oxide release which is normally a response of bone cells to mechanical strain. By contrast, we found that cells from both regions were able to respond to dexamethasone, a well-established promoter of osteoblastic differentiation, with the expected increase in alkaline phosphatase activity. Our findings indicate that the failure of repair of the rotator cuff may be due, at least in part, to a compromised capacity for mechanoadaptation within the greater tuberosity. It remains to be seen whether this apparent decrease in the sensitivity of bone cells to mechanical stimulation is the specific consequence of the reduced load-bearing history of the greater tuberosity in these patients.

Developments in shoulder arthroplasty

Indications for shoulder arthroplasty are numerous, mainly owing to glenohumeral osteoarthritis, rheumatoid arthritis, or fracture of the proximal humerus. However, the anatomy and the biomechanics of the shoulder are complex and shoulder arthroplasty has evolved significantly over the past 30 years. This paper presents the main recent evolutions in shoulder replacement, the questions not answered yet, and the main future areas of research. The review focuses firstly on the design, positioning, and fixation of the humeral component, secondly on the design, positioning, and fixation of the glenoid implant, and thirdly on other concepts of shoulder arthroplasty such as the reversed prosthesis, the cementless surface replacement arthroplasty, and the bipolar arthroplasty. This review demonstrates that more research is needed. Although, in the long term, large randomized trials are needed to settle the fundamental questions of what type of replacement and which kind of fixation should be used, biomechanical research in the laboratory should be focused primarily on the comprehension of glenoid loosening, which is a major cause of total shoulder arthroplasty failure, and the significance of radiolucent lines which are often seen but with no clear understanding about their relation with failure.

A security vulnerabilities assessment tool for interim storage facilities of low-level radioactive wastes

Limited permanent low-level radioactive waste (LLRW) disposal capacity and correspondingly high disposal costs have resulted in the creation of numerous interim storage facilities for either decay-in-storage operations or longer term accumulation efforts. These facilities, which may be near the site of waste generation or in distal locations, often were not originally designed for the purpose of LLRW storage, particularly with regard to security. Facility security has become particularly important in light of the domestic terrorist acts of 2001, wherein LLRW, along with many other sources of radioactivity, became recognized commodities to those wishing to create disruption through the purposeful dissemination of radioactive materials. Since some LLRW materials may be in facilities that may exhibit varying degrees of security control sophistication, a security vulnerabilities assessment tool grounded in accepted criminal justice theory and security practice has been developed. The tool, which includes dedicated sections on general security, target hardening, criminalization benefits, and the presence of guardians, can be used by those not formally schooled in the security profession to assess the level of protection afforded to their respective facilities. The tool equips radiation safety practitioners with the ability to methodically and systematically assess the presence or relative status of various facility security aspects, many of which may not be considered by individuals from outside the security profession. For example, radiation safety professionals might not ordinarily consider facility lighting aspects, which is a staple for the security profession since it is widely known that crime disproportionately occurs more frequently at night or in poorly lit circumstances. Likewise, the means and associated time dimensions for detecting inventory discrepancies may not be commonly considered. The tool provides a simple means for radiation safety professionals to assess, and perhaps enhance in a reasonable fashion, the security of their interim storage operations. Aspects of the assessment tool can also be applied to other activities involving the protection of sources of radiation as well.

An analysis of 20 years of radiation-related health care complaints in Texas for the purposes of quality improvement

In an effort to reveal the possible underlying causes of radiation-related health care complaints in the State of Texas, complaint data were evaluated using historical Texas Department of Health-Bureau of Radiation Control (TDH-BRC) reports. A major aim of the study was to generate a summary of the most commonly reported complaints that might be generalized to health care providers using sources of radiation across Texas. A generalizable list of common complaints would be a valuable tool for education and prevention programs, serving to possibly reduce the overall incidence of radiation-related medical complaints. Descriptive text summary reports of complaints were obtained from the TDH-BRC for the 20-y period inclusive of 1981 to 2001. The information was systematically coded into a computerized database. During the 20-y period of study, 481 health care-related complaints were identified, with approximately 74% consisting of claims of an "uncredentialed technician" (39%), "overexposure" (21%), or "regulatory violation" (14%). The most common categories of complaints imply some patient understanding or knowledge of the credentialing requirements of workers, the applicable dose limits, or the regulatory requirements associated with medical procedures. Since it is unlikely that an average patient would be aware of such issues, the findings suggest the complaints are not actually indications of the inappropriate uses of radiation, but are rather based on the patient's broader perception of services rendered. Most of the complaints levied during the period of study were done so anonymously (58%) and were levied against a generic facility (61%) rather than a specific technician (5%), doctor (4%), or student (1%). Approximately 61% of the complaints resulted in the issuance of a notice of violation upon investigation by the TDH-BRC, but the available data did not permit definitive linkage between the initial complaint and the violation issued. Taken in aggregate, the analysis suggests that improved communications between health care providers and the patients they serve could possibly serve to prevent future complaints. Although the analysis was limited to the data from a single state, the results may be of use to quality assurance programs on a broader scale because of the objective identification of likely common issues. Possible options for improving the means of systematically collecting initial compliant data in the future are also discussed.

Reported events of stolen radioactive sources in Texas from 1956 to 2000

Incident reports describing stolen source events in Texas from the years 1956 to 2000 were obtained from the Texas Department of Health-Bureau of Radiation Control and recorded into a computerized database using a pre-established set of codes. The data were then analyzed for the identification and characterization of trends. Over the 45-y period of analysis, 113 sources were reported as stolen. The radionuclides most commonly reported in theft events were Am, Cs, and Ir. The proportion of sources including Am as the sole source or Am combined with Be, or as a companion source with Cs, represented 56% of the total reported as stolen. Key risk factors identified as associated with source theft appear to include portability status, transportation status, transporter status, and radionuclide type. Based on the observations noted, suggested improved security measures are postulated including additional permitting controls, enhanced inspections, improved locking and storage procedures, and steps for communication to the public to enhance the prospects for recovery. Suggested enhancements to further improve data collection are proposed so that crime prevention information can be derived in future research.

Characterization and geographic location of sources of radioactivity lost downhole in the course of oil and gas exploration and production activities in Texas, 1956 to 2001

Case reports describing sources of radioactivity lost downhole in Texas from 1956 to 2001 were obtained from the Texas Department of Health Bureau of Radiation Control and entered into a computerized database. The events of the 45-y period of analysis were characterized, examining aspects such as source type, amount of activity, location of loss, depth, and date of occurrence. Results of the study found that 316 downhole source incidents were reported to the agency during this period of time, representing a total of 426 distinct sources of radioactivity lost downhole within the boundaries of the State of Texas. The sources lost were predominantly AmBe, accounting for 74 TBq of radioactivity at the time of loss, and Cs, accounting for 16.3 TBq of radioactivity. A longitudinal analysis of the data showed the average loss per active oil and gas rig in Texas (known as "rig count") at approximately 24 losses per 1,000 rigs. Specific geographic information was largely missing from many of the records, which prevented the geolocation of wells described to contain lost radioactive sources. As a result, most wells could only be located to the county level, and no comprehensive geographical information system (GIS) map could be accurately created from the data. However, when available, source location information was standardized to permit the characterization of the sources reported as lost. This effort produced the first dedicated compendium of lost downhole sources for the State of Texas and provides an important source of information for regulatory agencies. The ability to provide prompt information about the fate and location of sources of radioactivity is important to regulatory officials, given the recent concerns about radiation source inventory control in the post 9/11 world as it relates to the possible creation of radiological dispersal devices.

An analysis of variables influencing the number of radiation overexposure events in Texas from 1970 to 2000

Sources of radiation are used in a variety of modern work settings, including industrial, medical, research, and agricultural applications. Although regulatory controls exist to limit radiation exposures in these different settings, instances of radiation doses in excess of acceptable limits (referred to as overexposures) do occur. A unique study examined overexposure events in Texas over a 45-y period from 1956 to 2001. The primary purpose of the study was to characterize the factors associated with overexposure events. As part of this characterization, an interesting trend in the number of overexposures by year was observed, but not completely explained. The data revealed a dramatic increase in the number of overexposure events, followed by three apparent phases of decline. These declines are of particular interest because, while the increase and subsequent decrease in overexposures occurred, the number of permits to possess radiation sources in Texas generally increased over the same time period. This study focused on the identification of the factors that led to the trends in overexposure events. Data describing the reported overexposure events in Texas from 1970 to 2000 were obtained from the Texas Department of Health Bureau of Radiation Control (TDH BRC) and entered into a computerized database. With the assistance of senior members of the TDH BRC, the three primary factors influencing the number of overexposures were identified. These included domestic oil and gas exploration and production from 1970 to 2000, wherein sources of radiation are employed in various operations; the establishment of a training and certification requirement for industrial radiographers during the period of 1986 to 1988; and modification of the applicable regulations between 1992 and 1994. The generally accepted indicator of oil and gas exploration and production activity, known as "rig count," is the measure of the number of active oil and gas exploration and production platforms at any given time. Rig count is a parameter of particular interest in Texas because the state's economy is significantly tied to the market value of this important natural resource. The rig count parameter was shown to have a strong correlation with overexposure events (Pearson correlation coefficient of 0.82, p < 0.0001). Interestingly, the sources causing the overexposures indicate that the events stem primarily not from the oil and gas exploration activity itself, but rather from support activities in the form of industrial radiographic procedures. The number of overexposure events was also determined to be influenced by the imposition of the training requirement for radiographers and the modification of the applicable regulations (e.g., the elimination of the quarterly dose limit). The relative magnitude of these influences, however, was far overshadowed by the identified predominant predictor of rig count. The determination of rig count as the significant influencing factor in overexposure events is useful in possibly recognizing the potential for future occurrences of the same nature. This assessment also serves to highlight an apparent significant public health success story, as the number of overexposures per radioactive material licensee is shown to have declined significantly over the 30-y period of study. The factors contributing to this phenomenon are described to serve as a model for use in other settings.

A comparison of the results of regulatory compliance inspections in 1999 by the states of Texas, Maine, and Washington

Inspection outcome data provided by the state of Washington Department of Health, Division of Radiation Protection, for licensees of radioactive materials was encoded according to a system established by the Texas Department of Health, Bureau of Radiation Control. The data, representing calendar year 1999 inspection activities, were then analyzed and the results compared to previously published studies for the same year in the states of Texas and Maine. Despite significant differences in regulatory program size, age, and geographic proximity, the most frequently cited violation for radioactive materials licensees were shown to be similar for all three states. Of particular note were the violations that were identified to be consistently issued in all three states. These included physical inventories and utilization logs not performed, not available, or incomplete; leak testing not performed or not performed on schedule; inadequate or unapproved operating and safety procedures; radiation survey and disposal records not available or incomplete; detection or measurement instrument calibration not performed or records not available; and radiation surveys or sampling not performed or performed with a noncalibrated instrument. Comparisons were made in an attempt to generate a summary of the most commonly issued violations that could be generalized to users of radioactive materials across the United States. A generalized list of common violations would be an invaluable tool for radiation protection programs, serving to aid in the reduction of the overall instance of program non-compliance. Any reduction in instances of non-compliance would result in the conservation of finite public health resources that might then be directed to other pressing public health matters.

An analysis of 45 years of reported overexposure incidents in Texas, 1956 to 2001

Sources of ionizing radiation are commonly encountered in a wide variety of modern work settings. The controls in place to ensure the safe use of these sources have proven to be quite effective, as events involving occupational doses in excess of established limits are quite rare. Nonetheless, instances of doses in excess of established limits, commonly referred to as "overexposures," do occur, but the rarity of such events has resulted in a body of scientific knowledge that consists essentially of sporadic case reports. In this study, incident reports describing radiation overexposure events recorded in Texas from the years 1956 to 2001 were obtained and recorded into a computerized database using a pre-established set of codes. The data were then analyzed for the identification of possible trends or commonalties. During the 45-y period of study, overexposure events accounted for 50% (n = 3,796) of all the radiation-related incidents recorded in Texas for the time period (n = 7,534). Of the overexposure events, 65% (n = 2,342) resulted in the actual deposition of energy in the individual exposed. The remainder were determined to be doses recorded only by a personal dosimetry device. In most of the cases where doses were actually delivered to an individual, the doses were less than 0.05 Sv (5 rem). In only 0.5% of the cases (n = 13) were doses greater than 1 Sv (100 rem). The predominant sources reported as involved in the events included 192Ir, 60Co, and 137Cs. The information derived from the analysis may serve as a basis for a variety of interventions, such as preventative education activities, regulatory modifications, and the possible re-design of equipment identified as commonly associated with such events. The results of the study can also assist in the training of health care providers, as the recognition of common causes and sources of overexposures and subsequent treatments can be forecasted and summary treatment protocols developed.

Sonochemical degradation of phenolic pollutants in aqueous solutions

The sonochemical degradation of phenol, 2-chlorophenol and 3,4-dichlorophenol in aqueous solutions as a function of several operating conditions has been investigated. Experiments were performed at initial substrate concentrations of 0.1, 0.5 and 1 g l(-1), liquid phase volumes of 0.05, 0.07 and 0.08 l, electric power outputs of 125, 187.5 and 250 W, liquid bulk temperatures of 20, 35, 50 and 70 degrees C and an ultrasound frequency of 20 kHz. Substrate concentration was determined as a function of time by means of high performance liquid chromatography. At the conditions under consideration, the rate of degradation follows first order kinetics with respect to the substrate concentration and increases with increasing electric power and decreasing liquid volume. The relative reactivity appears to decrease in the order: 2-chlorophenol > 3,4-dichlorophenol > phenol. Measurements of liquid phase total organic carbon content showed that degradation by-products are more recalcitrant than the original substrate. The rate of 2-chlorophenol degradation was also found to decrease with decreasing liquid bulk temperature and increasing initial concentration. Addition of t-butanol as a hydroxyl radical scavenger only partially inhibited degradation, thus implying that degradation is likely to proceed via both radical-induced and thermal reactions. Addition of Fe2+ ions at concentrations as low as about 0.2 x 10(3) g l(-1) resulted in increased degradation rates; this is attributed to iron being capable of readily decomposing hydrogen peroxide (generated by water sonolysis) in a Fenton-like process to form hydroxyl radicals as well as being an effective oxidation catalyst. The implications of the use of ultrasound in wastewater treatment are also discussed.

A radiation protection program prospectus based on the collection of 10 years of key performance indicator data

In 1992, the University of Texas Health Science Center at Houston Radiation Safety Program began assembling data on a monthly basis that described various program activities. At the end of calendar year 2002, a decade of data had been collected, so the information was summarized into a novel program prospectus, displaying various indicator parameters in a format similar to that used in a commercial enterprise prospectus provided to potential investors. The consistent formatting of the data afforded a succinct and easily digestible snapshot of program activities and trends. Feedback from various program stakeholders, even those unschooled in radiation safety matters, was overwhelmingly positive. The prospectus aided in communicating the scope of work undertaken by the program, and has helped maintain program support, even in challenging economic times. The data summary is also proving to be useful in making future projections regarding program needs.

Effectively displaying broad scope sub-licensee radioactive material inventory allocations and possession quantities

As part of its annual broad scope license radiation protection program review, the University of Texas Health Science Center at Houston radiation safety program discovered that although inventory control and monitoring mechanisms were being effectively implemented at the sublicensee level, a method did not exist to demonstrate compliance with collective broad scope license possession limits at the institutional level. To address this shortcoming, the radiation safety program data warehouse system was modified, and an automatic summary report showing collective sub-licensee maximum possession authorizations was created. But this report did not effectively present the summary information in a manner that key stakeholders could readily comprehend, as the data was not referenced to collective institutional possession limits. So a graphic version of the summary report was created wherein, for each isotope possessed, the collective institutional limit was displayed, along with the totals of all the individual sub-licensee maximum possession limits and current amounts on hand. This simple graphic served to effectively communicate the current status of the institution's radiation source inventory to the radiation safety committee, executive management, and state regulatory officials. The effort has served to simplify the sometimes-complicated source inventory control process and has facilitated subsequent program reviews. In the future, the method is expected to assist the radiation protection program in anticipating when broad license amendments may be needed to accommodate operational changes.

Statistical validation of a commonly used method for personnel dosimetry issuance determinations

In 1992, the federal requirements for personnel monitoring of occupational radiation doses were modified, making monitoring compulsory only for individuals "likely" to exceed 10% of the applicable annual dose limits. This regulatory change served as a catalyst for many radiation protection programs to re-evaluate their personnel monitoring issuance criteria to determine if some monitoring services might be reduced or eliminated. But in the absence of any clear definition of the term "likely," radiation protection programs relied on adjustments largely based on reviews of previous monitoring results and professional judgment. Although such semi-quantitative assessments may have been appropriate, the approach was not without inherent programmatic risks, as radiation dosimetry programs have been shown to be a consistent source of regulatory non-compliance upon inspection and serve as essential elements in defense against litigation efforts purporting workplace-related radiation injury. The objective of this study was to subject this commonly used method for post-regulatory change dosimetry issuance determinations to statistical validation. Personnel monitoring data from The University of Texas Health Science Center at Houston Radiation Safety Program pre- and post-1992 regulatory changes were accessed and descriptively analyzed. The dynamic nature of the institutional environment made direct comparisons of individuals between years impractical, so 1990 mean dose levels for various independent variables were compared using the Kruskal-Wallis non-parametric ANOVA test at a significance level of alpha = 0.05. The data from 1998 were then analyzed to ascertain if the groupings identified as statistically different in 1990 were still being monitored. The analyses statistically validated the monitoring program reductions made by the University of Texas Health Science Center at Houston radiation protection program. In addition, statistical support for further monitoring program reductions were identified, if such reductions were deemed to be necessary in the future.