Radiation protection at an aviation museum.

The U.S. Nuclear Regulatory Commission (U.S. NRC) will soon publish a proposed amendment to its rules that will classify the naturally occurring isotope Ra as "byproduct material" subject to its regulatory control. One of the uses of radium in the first half of the twentieth century was as a source of energy that would make certain consumer products "glow in the dark." In addition to wristwatches and other timepieces, this form of self-luminescence was widely used on aircraft instruments. There have been a number of facilities where large numbers of such instruments were stored and leakage of this isotope occurred. Subsequent decontamination of these areas, including expensive disposal of the radioactive waste, was required. We were asked to evaluate the potential hazards of aircraft and aircraft instruments at a museum in New York City, specifically the decommissioned aircraft carrier USS Intrepid. We present the results of our investigation and discuss the implications as they relate to the proposed new U.S. NRC regulations and compatibility issues with State regulations.

Minimizing entrance door thickness for direct-entry radiotherapy rooms.

When medical linear accelerator rooms are constructed without entrance mazes, the entrance doors can be as thick as 50 cm, weigh 10,000 kg, and cost 50-60 thousand dollars. We describe a method of room design in which the therapy unit is positioned 180 degrees from the usual orientation. A short stub wall that attenuates the leakage component of the secondary radiation protects the door. Using this approach, the door can be reduced to approximately half the usual thickness with a significant impact on cost. For these motor-driven doors, there are also long-term benefits related to maintenance of the operating hardware.

The upward spiral of drug costs: a time series analysis of drugs used in the treatment of hemophilia.

BACKGROUND: Hemophilia is an expensive disease because its treatment is heavily dependent on costly clotting factor drugs. Over the last nine years,a consortium of three Comprehensive Hemophilia Treatment Centers and other hospitals, which purchased clotting factors for their patients, has seen treatment costs escalate on average 17% annually. Currently, new, even more expensive drugs are entering the market. METHODS: This study analyzes 3,244 purchases that were made over a nine-year period totaling nearly 500 million units of clotting factor, representing every product on the market. Purchases were made both apart from and under the Federal Public Health Service (PHS)discount pricing rules. FINDINGS: The main cause of the increases was the move to newer, more expensive products. The average price of existing products increased less than 2%per year, but new products were priced, on average, 47% higher than existing products. Overall consumption increased by an average of 5% per year, likely reflecting prophylactic treatment modalities that require greater amounts of clotting factor. Government pricing programs, such as the PHS program, were ineffective or counterproductive at reducing costs. There is a notable absence of competition in this market, with a few dominant companies having a functional monopoly in the largest segments of the market. Prices of older products are not lowered, even when new products are brought to market. A few products that serve small patient groups have had their prices increased substantially. INTERPRETATION: This escalation is likely to continue as new, more expensive clotting factor drugs are developed. Since these new products are not proven to be any safer or more effective than the current products, this situation creates a risk of intervention by government and insurers to address both treatment costs and exhaustion of patients' insurance caps. Drug companies are not serving the patients by pricing new, but often very similar, products so aggressively. The trends seen in this patient group will likely be seen in other patient groups in the future. Ultimately, doctors and patients will lose treatment options and health care availability unless collaborative strategies are developed to reduce costs.

In-flight radiation exposure during pregnancy.

During high-altitude flight, the cosmic radiation dose rate in an airliner is greater than it is at ground level. For a casual traveler, the impact on pregnancy from cosmic radiation exposure during flight is trivial. Pregnant frequent flyers, pilots, and flight attendants can, however, receive exposures that exceed current recommended values if they do not appropriately modify their work schedules. In addition to the galactic cosmic-ray background that is the source of this radiation, severe disturbances on the sun may cause eruptions that significantly raise radiation levels at airliner altitudes for brief periods, possibly having an impact even on casual travelers. This article will help obstetrician-gynecologists provide advice to their pregnant patients about in-flight radiation risks. That advice should be influenced by an understanding of recommended radiation exposure limits and a perspective on how those limits relate to the potential for real harm. Resources provided by the U.S. Federal Aviation Administration and others to help pregnant women and their physicians make informed decisions about the acceptability of this type of exposure are described.

Lead equivalence in glass: the default value vs. a defined value.

To most health physicists, the specification of lead-equivalent thickness in a glass viewing window is a request for equal attenuation by the glass and sheet lead of the same stated thickness. A failure to specify the energy at which equivalence is desired can lead to a significant deviation from the intended attenuation value. The reason for this is an alternative or "default" definition of lead equivalence that is used by the glass suppliers when the energy information is omitted.

Shielding design for multiple-energy linear accelerators.

The introduction of medical linear accelerators (linacs) capable of producing three different x-ray energies has complicated the process of designing shielding for these units. The conventional approach for the previous generation of dual-energy linacs relied on the addition of some amount of supplementary shielding to that calculated for the higher-energy beam, where the amount of that supplement followed the historical "two-source" rule, also known as the "add one HVL rule," a practice derived from other two-source shielding considerations. The author describes an iterative approach that calculates shielding requirements accurately for any number of multiple beam energies assuming the workload at each energy can be specified at the outset. This method is particularly useful when considering the requirements for possible modifications to an existing vault when new equipment is to be installed as a replacement for a previous unit.

An unrecognized occupancy change in the vicinity of a medical linear accelerator.

It seems obvious that if a significant increase in occupancy occurs in the immediate vicinity of any radiation room a reexamination of the adequacy of the shielding should be performed. We discuss a facility where a new building was constructed in close proximity to an existing medical linear accelerator and no consideration was given to the consequences of that construction as it might impact the doses received by occupants of the new structure. For more than 10 years some areas in that building may have received exposures greater than the allowed regulatory limit. The situation reported here should serve as a cautionary tale for those who have the responsibility for providing radiation protection at any site where new construction or increases in occupancy might require a reanalysis of the previously designed radiation shielding.