Radioactive Sources Applications and Alternative Technologies (2021) / Chapter Skim
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4 Radiation Sources and Alternative Technologies in Medicine and Research
4 Radiation Sources and Alternative Technologies in Medicine and Research
Pages 69-96
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From page 69... ...
Reducing the risk of TA-GvHD is based on blocking T-cell replication by treating cellular blood products prior to transfusion into a susceptible patient. In the United States and Europe, only blood components used for the treatment of patients with identified risk require treatment such as irradiation.
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From page 70... ...
powder sealed in stainless steel capsules; referred to as cesium irradiators in this chapter) have been the standard method for irradiation of blood components to inactivate lymphocytes and prevent TA-GvHD for decades.
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From page 71... ...
4.1.2 Alternative Technologies There are two alternatives to cesium-irradiators: x-ray irradiators for all blood components and pathogen reduction methods for some blood components. These are discussed in the following sections.
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From page 72... ...
The throughput of x-ray devices is comparable to cesium irradiators with typical exposure times of about 5 minutes. The x-ray devices are about the same size as gamma irradiators but weigh slightly less.
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From page 73... ...
Several companies have attempted to develop the next generation of low-energy compact accelerators dedicated to replacing radioisotopes in cesium blood irradiators. For example, in 2010, RadiaBeam Systems developed a novel fabrication process for linacs with the goal to reduce the costs and size, making them suitable for these applications.
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From page 74... ...
. Whole-blood pathogen reduction can potentially produce both platelet and red cell inactivated blood components by standard blood bank centrifugation methods.
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From page 75... ...
A similar cost-benefit analysis conducted by a smaller medical center, the Christus Spohn Hospital in Texas, also demonstrated financial savings by transitioning to the x-ray irradiator.5 The American Red Cross, the largest blood treatment and supply organization in the United States, began replacing its cesium irradiators with x-ray irradiators in 2017. At that time, the American Red Cross had 33 blood irradiators.
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From page 76... ...
, implying that the Indian vitrified cesium pencils cannot be used in existing blood irradiators, which would have to be redesigned to accommodate the much lower specific activity material. Use of pathogen reduction methodologies is another promising alternative to gamma irradiation for some blood components.
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From page 77... ...
4.2.1 Radioisotope Technologies Research irradiators using gamma sources are similar in design to blood irradiators. The typical activity of the Category 1 and Category 2 cobalt-60 or cesium-137 radiation sources is approximately 1,200–3,000 Ci (44.4–111.0 TBq)
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From page 78... ...
. Public Health England recently published a comprehensive report that includes a decision tree to help guide selection of a replacement technology for cesium irradiators for research (and blood)
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From page 79... ...
for use in external beam radiotherapy are called teletherapy machines. In high-income countries, there generally is sufficient access to radiotherapy, although regional and population disparities in access and outcomes do exist.
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From page 80... ...
. Modern teletherapy machines have a SAD of 80 cm or 100 cm (see Figure 4.5)
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From page 81... ...
In Africa, there are about 230 radiotherapy centers serving a population of more than 1.2 billion.9 There are approximately 410 teletherapy machines and 350 linacs in these centers,10 indicating that cobalt-60 teletherapy continues to be essential for radiotherapy delivery. 4.3.2 Alternative Technologies Medical linacs are a widely used alternative to cobalt-60 teletherapy.
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From page 82... ...
SOURCE: Image courtesy of oncologymedicalphysics.com. Further Advancements in Alternative Technologies Advancements in medical technologies for external beam radiotherapy continue to evolve and include new techniques and even new particles.
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From page 83... ...
An x-ray beam between 4 and 6 MeV has a penetration profile that is comparable to a cobalt-60 source. If such a system were available at a cost similar to a cobalt-60 teletherapy machine and had a flexible, resilient FIGURE 4.7 Compact linac developed by Euclid Techlabs LLC.
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From page 84... ...
TibaRay's primary goal is to produce a 16-accelerator system arrayed around the patient (see Figure 4.8) to deliver treatment to the patient at a very high dose rate, equivalent to FLASH radiotherapy described earlier in the chapter and do this at a price equivalent to existing single-accelerator systems.
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From page 85... ...
Some features of linacs, such as multileaf collimators, dynamic wedges, and dynamic operation, can also be installed on cobalt-60 teletherapy machines to improve treatment. However, in the absence of a market in high- and many middle-income countries, manufacturers of cobalt-60 machines have FIGURE 4.9 Number of electrical outages in a typical month.
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From page 86... ...
are not always involved in the decision-making process to ensure that machine specifications meet operational needs; • Lack of reliable power supply can lead to long downtimes for the linacs and therefore delays in patient cancer treatments; • Lack of a sustainable pathway for equipment repair and maintenance leads to even longer downtimes for the linacs; and • Cobalt-60 teletherapy machines that are replaced by linacs are not always immediately disposed of. Based on these case studies, it is likely that at least for the foreseeable future, cobalt-60 teletherapy will play an important role in cancer therapy in LMICs due to the lower cost, simplicity of design, reliability, and ease of operation.
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From page 87... ...
Ghana Ghana has five operating radiotherapy machines (three linacs and two cobalt-60 machines) located in three radiotherapy centers that serve a population of 29 million.
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From page 88... ...
Zambia Zambia has three radiotherapy machines (one linac and two cobalt-60 teletherapy machines) located in a radiotherapy center that serves a population of 17 million.
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From page 89... ...
Zambia plans to expand radiotherapy services to other regions of the country in the near future. 4.4 STEREOTACTIC RADIOSURGERY Despite the transition from cobalt-60 teletherapy to linacs for external beam therapy, many radioisotope-based devices are still in use for a subset of radiotherapy known as stereotactic radiosurgery (SRS)
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From page 90... ...
4.4.2 Alternative Technologies There are currently three options for nonradioisotope alternatives to gamma-based SRS: SRS with standard isocentric linac; SRS with dedicated isocentric linac; and miniature linac on a robotic arm (CyberKnife®)
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From page 91... ...
The study attributed the increase use of linac-based SRS to availability (specifically in community medical centers as opposed to academic medical centers) and location (in non-western states compared to western states)
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From page 92... ...
Once the timed treatment is completed, the radioactive sources and catheters are removed. Though most HDR brachytherapy requires a few sessions to deliver the entire prescribed treatment, it is typically performed in an outpatient setting and the patient leaves the facility between cycles.
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From page 93... ...
However, elsewhere, HDR brachytherapy sources are considered Category 2 sources based on the IAEA categorization system. 4.5.2 Alternative Technologies Electronic brachytherapy offers several unique features compared to traditional brachytherapy, including lower energy (typically less than 120 kVp)
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From page 94... ...
Radiating Hope, a nonprofit organization whose mission is to provide radiation therapy equipment to underresourced countries, provided an HDR brachytherapy unit in 2013 to the Institut Curie's cancer center in Dakar, Senegal, which enabled thousands of Senegalese women with cervical cancer to receive treatment (Einck et al., 2014)
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From page 95... ...
These comparison studies consume resources that are typically scarce in research institutions. Recommendation F: The National Nuclear Security Administration should engage with federal partners such as the Department of Health and Human Services, the National Science Foundation, and the Food and Drug Administration to support equivalency studies for researchers who are considering replacing their cesium or cobalt research irradiators with alternative technologies.
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From page 96... ...
In situations in which local resources and infrastructure cannot support alternatives, efforts should focus on enhanc ing radiological security for existing radioactive sources, assisting with building the infrastructure, and supporting research and development projects to adjust the technologies to operate effectively in resource-constrained environments, for example, when there is unreliable electricity supply. LMICs have an increasing need for cancer therapy capabilities and capacity.
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