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182 Cards in this Set
- Front
- Back
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Brachy means
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Short
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In the past ________ and ________ sources were used for brachytherapy
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radium and radon
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Today use of artificially produced radionuclides such as ____, ____, ____, and ___ is increasing
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Cs 137, Ir192, Au 198 and I 125
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the first interstitial implant was in
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1911
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what new technological advances have stimulated interest in brachytherapy
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introduction of artificial isotopes, afterloading devices to reduce personnel exposure, automatic devices w/ remote control to deliver controlled radiation exposure from high-activity sources, US guided applicators
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Major of brachytherapy is that
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a very high dose of radiation can be delivered locally to the tumor in a relatively short amt of time
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electrons may often be used as an alternative to _____________
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interstitial implants
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Interstitial Brachytherapy is characterized by the placement of radioactive sources _____________
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directly into a tumor or tumor bed
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Types of interstitial brachytherapy implants
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Temp and Permenant
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Temporary: where the sources are ______________
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removed after desired dose has been delivered
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Permenant: Where the sources are .....
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left in the implanted tissues
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Ex. of temporary interstitial implant
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radium needles, iridium wires or iridium seeds
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Ex. of permenant interstitial implant
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Au 198 and I125
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In general the _____________provides better control of source distribution and dosimetry than ___________
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temporary and permenant
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Permenant implants are preferred for some tumors such as those in the
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abdominal and thoracic cavity
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Intracavity places radioactive sources within _____________
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a body cavity for tx
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Intracavity has been used in the tx of __________CA for more than ________years. It is also used in the tx of _________ and ___________
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cervix, 50, uterus and vagina
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Intraluminal brachytherapy: a rapidly emerging tx modality w/ potential applications for ________, ______________, and __________ in addition to is application for ___________.
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peripheral vessel angioplasty, bypass graft anastamoses, and arteriovenous dialysis grafts; coronary vessels
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The use of stents and radiation can reduce the rate of ___________ in the vessel
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re-stenosis
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Topical BT places the radioactive sources on ________; _______ of the _______treated may be taken and prepared to place the sources in definite arrangements to deliver te prescribed dose
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top of the area to be treated; molds, body part
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Source strength plays 3 roles in BT
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provides a commonly accepted standard means of describing quantities of emitted radiation; it allows practitioners to form a basis for computational dosimetry, which is the calculation of dose w/ the aid of a computerized system; it serves as a prescription parameter in BT
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Historically the term used to describe activity in terms of the number of disintergrations per unit of time is the
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Curie
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The Curie is
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3.7 X 10(10) disintegrations per second from 1g of radium
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The ________ is the becquerel (Bq)
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SI
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one Bq equals
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one disintegration per second
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1 mCi =
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3.7 x 10(7) disintegration/sec
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1 uCi =
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3.7 x 10(4) disintegration/sec
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1 MBq
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1 x 10(6) disintegration/sec
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1 mCi = ______MBq
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37
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1GBq =
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1 x 10(9) disintegration/sec
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1 Ci = GBq
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37
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The relationship between the number of atoms and the unit of time in the radioactive decay formula is ___________
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proportional
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_____________-- is the rate of decay of a radioactive material or the change in the number of atoms in a certain amt of time
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actively
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The activity is ____________ proportional to the decay constant.
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directly
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_______________ is the concept used to deal with the isotope disintegration.
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half-life
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The relationship between half-life and activity is ___________ proportional.
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inversely
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Halflife of Radium 226
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1622 years
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Halflife of Cobalt 60
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5.26 years
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Halflife of Cesium 137
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30.0 years
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Halflife of Iridium 192
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Halflife of Iodine 74.1 days
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Halflife of Iodine 125
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60.2 days
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Halflife of Gold 198
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2.7 days
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Halflife of Radon 222
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3.82 days
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Halflife of Copper 64
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12.8 hours
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the avg lifetime for the decay of radioactive atoms
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mean life
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mean life formula is
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T1/2 x 1.44
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Brachytherapy most commonly uses _____ radioactive sources within or adjacent to a tumor volume
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sealed
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A sealed source is ____________ by welded ends
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encapsulated
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The metal casing on encased isotopes serves what two fxns
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preventing escape of radioactivity and absorption of beta particles
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A wipe test for sealed sources is an example of a
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leak test method
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First isotope to be identified
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Radium 226
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Brachytherapy most commonly uses _____ radioactive sources within or adjacent to a tumor volume
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sealed
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A sealed source is ____________ by welded ends
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encapsulated
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The metal casing on encased isotopes serves what two fxns
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preventing escape of radioactivity and absorption of beta particles
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A wipe test for sealed sources is an example of a
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leak test method
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First isotope to be identified
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Radium 226
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Brachytherapy techniques were developed using __________
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Radium 226
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Radium decays mainly by
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alpha emission
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Before it decays to a stable lead radium decays to form
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radon a heavy inert gas
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The advantage of radium is its ____________
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high specific activity
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The disadvantage of radium is the ______________that accompany its use
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inherent radiation hazards
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A typical radium source consists of a ____________made of platinum or stainless steel
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hollow needle or tube
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The length of the area in which the radioactivity lies in the source is called the ________-
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active length
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The ____________is the total length of the source from end to end
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physical length
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_____________or strength of source: milligrams of radium content
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activity
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1mg of _____________ has an activity of 1mCi
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radium
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_____________: transverse thickness of the capsule wall usually expressed in millimeters of platinum
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filtration
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________________: can be found by dividing the activity by the active length
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linear activity of a source
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____________sources have the same concentration throughout their active length
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uniform
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__________-needles are heavily loaded at one end with lighter concentration at one end
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indian club
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heavily loaded at both ends with lighter concentration in the middle
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dumbbell needles
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the technique of loading the radioactive source after the technician has left the room is known as
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after loading
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____________is the most widely used radium sub
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Cesium 137
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______________has largely replaced radium as the primary iso for brachytherapy for the cervix and uterus
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Cesium 137
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____________ has a primary photon energy of 662 keV (its comparble to radium's 830keV making it easier to convert)
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Cesium 137
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Cesium 137's advantage over radium include
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the lower energy (reduces radiation safety hazard), longer half-life, widely available
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________________ is supplied in the form of wires of iridium-platinum alloy or as small seeds of this alloy attachedd to nylon ribbons with a spacing of 1cm between seeds
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Iridium 192
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Iridium 192 undergoes _____decay
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beta
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Iridium 192 has an avg energy of __________--
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370keV
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___________'s short half life makes it better than Cesium for temp implants off easily reached tumor sites such as breast or tongue
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Iriddium 192
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Since _____________ is produced in a nuclear reactor, it can be reactivated for future use
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Iridium
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_____________- is most commonly used in standard brachytherapy app today
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Cobalt 60
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_________ has a high specific activity which allow for fabrication of small sources but is more expensive than cesium
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Co60
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________ has been used as an external bm rad source, opthalmic applicators and in some countries in needles and tubes, HDR and Gamma knife procedures
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Co60
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__________ has a very short half-life and a monoenergetic (only one energy is produced 412 keV)
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Gold 198
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___________is a popular sub for Radon 222 for use in interstitial perm implants
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Gold 198
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__________is supplied in the form of cylindrical grains or seeds encapsulated in platinum
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Gold 198
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the low dose of ___________ makes rad safety less of a prob and more of the dose is absorbed locally
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Gold 198
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Due to the _______half-life of Gold the seeds are shipped with very high activities so that by the time they are used they have an activity in the range of 5 miCi/seed
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short
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gold gives the tissue a very ___________ in a short time
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high dose rate
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A method called HDR ans is ideal for
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prostate implants
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The use of __________is becoming more pop in interstitial seed implants
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I 125
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____________is produced as a daughter product from the neutron activation of xenon 124 to xenon 125; the xenon 125 decays by e- capture to produce the daughter ___________
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Iodine 125 (both blanks)
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____________ decays by e- capture to produce useful 35.5 keV gamma ray, low energy and half-life make shielding minimal
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I 125
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The dose is deposited very close to the seeds, reducing the dose to __________
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structures next to the tumor
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___________ is a type of LDR
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I 125
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Both ________ and _______ are replacements for radon 222
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I 125 and Au 198
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If an _______ seed breaks the radioactivity becomes airborne and can be inhaled causing great damage to the lung tissue
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Radon 222
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A central component of the calculation techniques is the ________
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gamma factor
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___________ can be defined as the exposure rate at 1m from a radioactive source of known activity
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gamma factor
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The units of gamma factor are:
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Roentgen x CM2/MCi x hr
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An important limitation to the use of the gamma factor is that it is
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applicable only to a point source of radiation
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A radioactive source will place a limitation on the distance at which the ________can be applied
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gamma factor
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Rx dose of .5 to 2 cGy/min
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LDR
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20cGy/min or higher
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HDR
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LDR has a long history of being used to treat cancers of the________HDR can also be used for management of these same CAs
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head and neck, gyn, breast and prostate
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the major advantage to HDR is
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more convenient for pt and tx facility in terms of time and space, and less expensive w/ sim outcome
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Cesium and Cobalt were commonly used in the past but _____ is the most commonly used HDR source today
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Iridium 192
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__________is chosen for HDR b/c of its high specific activity (which allows for smaller source for the same activity) and low photon energy requires less shielding
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Iridium 192
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the disadvantage of Iridium 192 as HDR is
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short half-life requiring replacement every 3-4mos
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Medium dose rate
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> 2 Gy/hr but <12Gy/hr
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External applicators or molds are used when a pt has a well circumscribed _________________ that requires a high localized dose
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suface lesion
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Molds should fit ________ and provide ________for adjacent sensitive structures
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tightly;shielding
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Areas commonly treated with molds
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skin, oral cavity, nasal cavity, hard palate, and orbital cavity
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_______________ places the radioactive sources directly into or adjacent to the tumor or tumor bed (perm or temp)
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Inerstitial applicators
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___________interstitial apps are performed when the tumor to be treated is inaccessible
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permenant
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___________ and ___________ are ideally suited for permenant implants b/c of their short half-lifes
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gold and iodine
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External applicators or molds are used when a pt has a well circumscribed _________________ that requires a high localized dose
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suface lesion
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Molds should fit ________ and provide ________for adjacent sensitive structures
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tightly;shielding
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Areas commonly treated with molds
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skin, oral cavity, nasal cavity, hard palate, and orbital cavity
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_______________ places the radioactive sources directly into or adjacent to the tumor or tumor bed (perm or temp)
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Inerstitial applicators
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___________interstitial apps are performed when the tumor to be treated is inaccessible
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permenant
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___________interstitial implants are used to treat inaccessible tumors and ______ and _____ are often used for their short half-lifes
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Permenant; I 125 and Au 198
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___________ are used for deep seated lesions in the pelvis (prostate;rectum) ab and lungs using I125 and Au198
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permenant interstitial implants
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_______ interstitial implants are used where there is no _______
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temporary; body cavity
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______ is used in most temp interst after loading implants
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Iridium 192
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To improve accuracy of the needle placement and to maintain a good position during the tx___________ can be used
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stabilizers and guides
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Common areas to be treated with temp interstitial implants
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rectum, prostate, vagina, and urethra
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GYN insertions may be done w/ _____ or ________
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LDR or HDR
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A ________ and a __________ are commonly used in brachytherapy app of the cervix
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central tandem and pair of lateral ovoids
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The______ is a long narrow tube that inserts into the opening of the cervix
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tandem
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The _______ or ___________ are oval shaped and insert into the lateral fornices of the vagina
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ovoids or colpostats
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The ovoids provide shielding to the __________and __________
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bladder and rectum
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The tandem and ovoids are stabilized with________which also displaces the rectum and bladder
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packing(sterile gauze)
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Once loaded with sourcees the tandem and ovoids generally demonstrate a __________isodose distribution
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pear shaped
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The dose at point ___ is typically about 1/3 the dose at point ____
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B; A
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__________is located 2 cm superior and 2 cm lateral to the center of the cervical canal (at the cervical os) in the plane of the uterus
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Point A
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__________was originally 3 cm lat to point A but is currently being noted as being 1cm lat to the medial aspect of the pelvic side wall
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point B
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The anatomical points used historically for cervical and uterine tx are
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points A and B
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_______ and ________ are examples of intracav implants
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heyman capsules, vag cylinders
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____________: all the uterus is packed w/ stainless steel capsules that house Cesium sources to treat uterine cancers that are inop
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Heyman capsules
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With the _________ metal wires are numbered for removal which can be done with remote afterloading
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Heyman capsules
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___________ protrude out of the vagina
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Heyman capsules
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____________ are a variety of apps designesd to give a high dose to vaginal lesions w/o excess to bladder or rectum
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Vaginal Cylinders
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The _______design of the vaginal cylinder are designed for simultaneous tx of the uterine cav, cervix and vag walls
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Declose uterine-vaginal after loading system
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Vaginal cylinders are available in several _____,________, and _________
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designs, lengths and shielding designs
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____________ places radioactive sources w/in body tubes such as the esophagus, trachea, and biliary tract
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Intraluminal brachytherapy
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_____________ can be addressed by placing radioactive sources onto or adjacent to the lesions
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obstructive lesions
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_____________HDR apps for obstructive lesions using Cesium 137 and Iridium 192 have been done successfully
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Pulsed
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Many clinical trials are evaluating the role of ____________ following PTCA an alternative to CABG
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Intravascular stent application
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It is thought that using Intravascualar stent apps may reduce the rate of _____ in pts receiving stent therapy this can be done with brachy or external rad
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restenosis
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Because of __________ external rad may be better for irrad of peripheral vessels than coronary vessels
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heart motion
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__________ are the preferred method of Intravascualr brachy
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Catheter-based
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_________systems consists of a linear array of sources, like gamma Ir 192, attached to a guide wire and inserted into the balloon cath and pushed into place in the stented area (other cath systems use beta sources such as P32 and yttrium 90 and stronium90/yttrium 90)
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Catheter based
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Radioactive stents are ____________ implants using P32, yttrrium 90 and vanadium 48 all beta emitters
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permenant
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The advantage to a radioactive stent is
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it provides irradiation and stent into one
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the disadvantage to a radioactive stent is
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much more complicated dosimetry
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Three types of systems used for dosimetry and dose distribution for interstitial implants ___________,_____________, and ________
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Patterson-Parker, Quimby and Paris
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In the 1930s ___________ and _________ at the Manchester hospital in England developed guidelines and dosimetry methods for Radium dosimetry
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Ralston Patterson and H.M. Parker
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The Patterson-Parker System estab a set of guidelines that if followed will provide a dose of ____w/in the implanted area
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+/- 10%
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implantation philosophy strives to deliver a __________ dose to a plane or volume
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uniform
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the patterson-parker uses a __________ of radioactive materials to produce a ________ distribution of a dose
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non-uniform;uniform
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The patterson-parker assumes the use of ______ sources to be implanted in tissue in planes or other geometrical shapes and gives rules for placing the radium sources in each case
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linear
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Rules have been established for both planar and volume implants with the _________
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patterson-parker
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Planar implants can have ___________,_________, or ______-
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both ends crossed, one end crossed or both ends uncrossed
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With the patterson-parker with _________ the planes should be 1 cm apart and parallel
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multiple plane implants
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With ___________If there is not a crossing at one or both ends the area is reduced by 10% for each uncrossed end
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multiple plane implants
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With ____________ If the plane is not square, increase the MG-HR by the appropriate elongation factor for the ratio of the long side to the short side
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multiple plane implants
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With _____________the activity should first be placed on the periphery, preferably using more than five sources with spacing no greater than the tx distance
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circular implants
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With ____________more sources can be arranged in an inner circle of half the diameter of the original area
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circular implants
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With __________distribution of activity is governed by the ratio of the diameter to the tx distance
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circular implants
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With _________the shape of the implanted volume resembles a 3D shape, more than one plane
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volume implants
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With __________shapes defined by the Patterson-parker include cylinders, ellipsoids, spheres and cubes
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volume implants
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With __________calc is usually done for seed implants of the prostate and other implants in which the activity is evenly spread out inside an organ or structure
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volume implants
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Volume implants can have _____ or ______ ends crossed
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one or both
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The ____________ is similar in concept to the Patterson-Parker system, it provides a set of tables used to calc dose given a # of implant parameters such as area, volume or total activity
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Quimby-Memorial
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In the Quimby the implant is assumed to be made up of ____________ w/in the implant giving a ___________ dose distribution
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uniform distribution of activity; non-uniform dose distribution
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The ___________ system uses uniform dose distribution of the rad sources as seen in the Quimby
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Paris system
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With the _________system the sources must be rectilinear and arranged so that their centers are in the same plane which is called the central plane, but not restricted to the plane
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Paris system
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this system is intended for use with removable long line implants, such as Ir-192 wires
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paris
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In the ______computers began to be used for calculating the dose distribution from specific brachytherapy implant using a method called the ___________
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1970s and Sievert Integral
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obtained by placing a source on unexposed film for a period of time, long enough to darken the film then the film may be scanned to check for dose uniformity
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an autoradiograph
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