Radiation Source Use and Replacement Abbreviated Version (2008) / Chapter Skim
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5 SELF-CONTAINED IRRADIATORS
5 SELF-CONTAINED IRRADIATORS
Pages 85-100
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From page 85... ...
, a rare but usually fatal complication of transfusion. Most self-contained irradiators use a radionuclide radiation source, with the vast majority being cesium-137 because of its long half-life, relatively low cost, and relatively modest shielding requirements, which make it possible to place a device in the upper floors of some hospitals and blood banks.
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From page 86... ...
Chemotherapy or radiotherapy treatments are prescribed for patients with a number of hematological cancers requiring bone marrow or peripheral blood stem cell transplants. Donor T cells that contaminate red cell and platelet units will recognize the recipients' cells as foreign, proliferate, and mount an immune response against recipient tissues.
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From page 87... ...
This is because irradiated red cells leak potassium at twice the rate of normal red cells and some patients are susceptible to adverse cardiac events from potassium following transfusion. Therefore, in many hospitals, red cell units are irradiated just prior to transfusion.
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From page 88... ...
SOURCE: Image provided by the committee. FIGURE 5-3 Typical self-shielded blood irradiator and typical 500-ml blood bag and small irradiation canister.
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From page 89... ...
The weights of cesium blood irradiators do, however, require more support than is found in the upper floors of many buildings, in which case the irradiators may need to be located next to a structural support for the building or have additional support installed to spread out the weight. REPLACEMENTS FOR BLOOD IRRADIATORS There are several alternatives to radioactive cesium chloride self-contained irradiators.
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From page 90... ...
(Regulatory reviews are needed for alternative forms of radioactive material used in current radiation source devices, as noted in Chapter 10.) Cobalt-60 Blood Irradiators Use of blood irradiators containing a radionuclide metal, with limited solubility and considerable resistance to explosive dispersion, would reduce the potential for widespread contamination of large areas if it were used in a radiological dispersal device.
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From page 91... ...
, the RS 3000, received Food and Drug Administration approval for use and has been available as an alternative to cesium-137 and cobalt-60 irradiators since August 1999. The device, which is similar in size and lower in weight than cesium-137 blood irradiators, utilizes 160-kVp x rays and can irradiate up to 2–3 units of red cells, depending on the bag manufacturer, with 25–37.6 Gy in approximately 5 minutes (Table 5-2)
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From page 92... ...
A course for training service personnel for installation and maintenance of the Raycell®, including x-ray tube replacement and alignment, high-voltage generator replacement, and dosimetry is offered by MDS Nordion and listed as Can$1,500. However, service needs for a failed instrument are urgent, the complexity of required preventive maintenance is much greater than for radionuclide sources and beyond the abilities of many blood bank staff, and the need to maintain good manufacturing practice conditions lead users to purchase an annual maintenance and service agreement for the device.
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From page 93... ...
However, it is not feasible to have centralized electron-beam irradiation of blood. Blood products typically are irradiated "on demand." The short 5-day shelf life of platelet products, in particular, would not permit adequate shipping time, "in queue" time as other materials are irradiated, and processing time necessary to send units to centralized irradiation facility.
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From page 94... ...
Studies with amotosalen and UVA light have demonstrated pathogen reduction and inactivation of human white cells comparable to and greater than that achieved in irradiation (a factor of 250,000 reduction in viable white blood cells) (Grass et al., 1998)
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From page 95... ...
Further development of S-303 will require repeating clinical studies with revised protocols to prevent red cell surface modifications. RESEARCH IRRADIATORS Research irradiators are used to expose biologic and nonbiologic materials to radiation of various types in order to evaluate the response of target materials to various doses, dose rates, and energies of the applied radiation source.
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From page 96... ...
They will deliver dose rates of 1 to 3 Gy/min at 50- to 80-cm distance. Self-contained units are housed in a dedicated room in a laboratory (see Figure 5-5)
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From page 97... ...
This new tube has a cylindrical gold target that will be used in a new type of specimen and blood irradiator that Rad Source reports will be capable of up to 450 Gy/min with multiple tubes and rotating specimen chambers (see Figure 5-6b)
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From page 98... ...
Additional security is required at most of these facilities because of other nuclear material or radioactive sources that are used at the facilities or for other reasons. Replacement of the cesium chloride sources could be made with glass or pollucite forms of cesium since very high specific activity is not required.
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From page 99... ...
. These alternative material forms use the same cesium-137 as radioactive cesium chloride; thus, the gamma rays and the half-life are identical, but the specific activity of these sources is smaller and the pollucite is more difficult to fabricate, especially for high-activity sources.
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From page 100... ...
Shielding challenges can be addressed in part by switching from lead shields to more effective tungsten or depleted uranium shielding, but tungsten shielding is more expensive than lead and manufacturing depleted uranium shielding is a very specialized, expensive operation. The shorter useful lifetime of radiation sources requires that they be replaced periodically, which entails transportation of a fresh source and, in some cases, the used source, with the attendant risks associated with source transportation.
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