Brachytherapy
Terms
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- Characterized by dose rates as high as 400 cGy/min
- HDR
- Characterized by dose rates of 40 - 200 cGy/hr
- LDR
- Which surgical brachytherapy implant technique may include permanent seeding?
- Interstitial
- Name the two commonly used sealed LDR sources.
- Cesium 137 and Iridium 192
- Name commonly used sealed source for HDR.
- Iridium 192
- Name the three sources used for permanent seeding in brachytherapy.
- Iodine-125, Pd-103, Gold-198
- Which system of interstitial implants is characterized by a uniform distribution of sources with intersource spacing of 1 cm?
- Quimby
- Which system of interstitial implants defines the stated dose as the maximum dose in the specified plane?
- Quimby
- Which system of interstitial implants defines the specified dose in a plane 0.5 cm from the implant plane and 10% higher than the minimum dose in the implant plane?
- Manchester or PP
- The philosophy of this implant system is to achieve a +/- 10% dose uniformity in the specified plane.
- Manchester or PP
- Which system of interstitial implants is characterized by constant linear activity of the implant sources?
- Quimby and Paris
- Which system of interstitial implants does not use crossing needles and why?
- Paris. System uses active needle lengths 40% longer than target tissue.
- Which system of interstitial implants is characterized by a spacing ratio of planar implants depending on target size?
- Manchester Or PP
- Which system of interstitial implants was developed for removable implants of long lines of sources?
- Paris
- Which system of interstitial implants technically works well for small implants such as Ra needles?
- Manchester or Quimby
- Why can't Quimby tables be applied to Ir-192 implants, even though they are equal intensity sources?
- Differing geometrical shapes
- Define the basal dose used to calculate the reference isodose for the Paris system.
- (85% of ...) The average of minimum doses between all sources.
- Define point B as used in the Manchester system for cancer of the uterus and its anatomical significance.
- 3 cm lateral to point A, represents level obdurator nodes
- What reference points are used for calculation dose in the ICRU system for intercavitary brachytherapy?
- Bladder and rectal wall points, lymphatic trapezoid, and pelvic wall points
- How is total source strength defined in the ICRU system for intercavitary brachytherapy?
- As total reference air kerma as a 1-m distance.
- Dose distribution in tissue for brachytherapy sources follow the inverse square law because...
- scatter dose build up and attenuation cancel each other out
- radioactive sources used in tandem and ovoids are in this shape
- tubes
- radiactive sources used in tandems and ovoids
- Cesium 137
- Define point A for gyno implants
- 2 cm cephalad of external cervical os and 2 cm lateral uterine tandem
- Isotope most frequently used in nasopharyngeal implants
- Cesium 137
- Radionuclide w energy 370 keV
- Ir - 192
- Radionuclide with energy 410 keV
- Gold 198
- Energy Pd 103
- 21 keV
- Energy gold 198
- 410 keV
- Radionuclide w energy 29 keV
- I-125
- I 125 used as what?
- Perm implant
- Cs 137 used for what?
- tandem and ovoids, LDR
- Ir 192 used for what?
- LDR HDR
- What kind of specific activity is needed by sources in HDR?
- High specific activity
- Typical initial dose rate in Pd 103
- 20 cGy/min
- How is Sr 90 made
- fission by-product nuclear reactor
- Typical volume for dose chamber used to calibrate brachy source
- 100 cm3
- Typical source length for pellet in vascular brachy
- 3 mm
- How is a batch of seeds calibrated?
- Average activity is taken to find activity per seed
- Half life Sm 145
- 1 year
- define apparent activity
- activity source, taking into account abs and atten in encapsulated material
- Sr 89 is used even as an unsealed source because...
- electrons have max energy 1.5 MeV
- What type of emitters in vascaular brachy?
- beta or gamma
- End result of Ra 226 decay series is stable:
- Lead 206
- Typical activity of C0 60 used in remote afterloaders
- 1 - 10 Ci
- How is Gold 198 made?
- Gold 197 bombarded w neutrons in reactor
- Periodicity for autoradiographing source in remote afterloader
- quarterly
- Typical activity Cs 137 used for remote afterloaders
- 40 mCi
- When can a patient with seeds leave hospital?
- Dose at 1 meter less than 5 mR/hr
- How is effective half life of source determined?
- function of physical and biological half life
- How is Pd 103 made?
- Bombard Rh 103 with proton in cyclotron
- Which radiopharmaceutical consists of tiny spheres in a liquid
- Y 90