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14 Cards in this Set
- Front
- Back
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What is IVB?
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Intravascular brachytherapy
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What is IVB used for?
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IVBT is used to reduce the incidence of restenosis following the removal or reduction of artery blockage with angioplasty.
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What sources are used in IVB?
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A variety of Beta and gamma ray sources are available for IVBT. Examples include:
- Strontium-90 - yttrium-90 - phosphorus-32 - iridium-192 |
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How large is the target volume?
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The target volume is confined to the region of the angioplasty.
Typically, it is 2 to 5 cm in length of the artery and 0.5 to 2 mm in thickness of arterial wall. |
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What is the dose for a typical IVB treatment?
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The target dose of 15 to 20 Gy to a 2- to 3-cm length of teh involved arterial wall at a radial distance of approx. 2mm from the source center.
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What is the difference between temporary and permanent IVB treatment?
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Temporary implants: Sealed sources or liquid-filled balloons
Permanent implants: Radioactive stents |
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What are the delivery systems for IVB treatment?
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Cordis Checkmate
Guidant Galileo Novoste Beta-Cath |
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Describe the Cordis Checkmate system
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- Consists of three components: a) a nylon ribbon containing an array of 192Ir seeds, b) a delivery catheter, and c) a ribbon delivery device.
- The iridium seeds are 3 mm in length and 0.5 mm in diameter. - The seeds are strung in a nylon ribbon with an inter-seed spacing of 1 mm. - - The number of seeds in a ribbon can be altered to provide source lengths of 10 to 80 mm. - Each 192 Ir seed has an activity of approximately 33 mCi. - Treatment time 15 - 25 minutes |
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Describe the Guidant Galileo system
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- Beta-ray source, 32P
- The 32P source is hermetically sealed in the distal 27-mm tip of a flexible 0.018-inch nitinol wire. A spiral centering balloon catheter, which centers the source wire, is flexible to navigate throught the arteries and also has perfusion capabilities to limit mycardial ischemia during the procedure. |
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Describe the Novoste Beta-Cath system
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The system consists of two main components:
a) a transfer device for housing and hydraulic delivery of a radiation source train, and b) a delivery catheter to transport the source train. The major advantages of the Novoste system include: - Use of the 90Sr/90Y source, which is one of the highest energy Beta-ray emitters with a long half-life (28 years) - High dose rate. Consequently, the treatment time is short (approximately 5 minutes) The major disadvantage is the lack of a catheter-centering device, which could result in extreme dosimetric hot and cold spots within the target volume. |
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What type of radiation is used in IVB?
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A variety of Beta and Gama rays sources are used
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How are the sources calculated?
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Gamma-ray sources:
- Same as for conventional brachytherapy. - A well type reentrant chamber may be used. - In terms of absorbed dose to water at a depth of 2mm Beta-ray sources: - Strength is specified in terms of dose rate in water at the reference point, where r0 = 2mm and angle0 = pie/2 - A well-type reentrant chamber with a source holder for a specific IVBT Beta-ray source |
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How do you measure the dose distribution?
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Dose distribution around IVBT sources is beast measured by film dosimetry.
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What QA is used in an IVB program?
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AAPM TG-60
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