radioactive sources

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Author:
azangari
ID:
120256
Filename:
radioactive sources
Updated:
2011-12-02 08:52:52
Tags:
brachy
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Description:
brachy
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  1. radioactive sources used in brachytherapy
    • radium
    • cs-137
    • ir-192
    • co-60
    • au-198
    • i-125
  2. radium 226
    • 1622 yrs
    • 830 kv (emits alpha and gamma)

    • -high specific activity
    • -uniform sources (tube/needle loaded by alternating radium sources and bone wax throughout)
    • -can be used for afterloading as well
  3. disadvantages of radium
    • *long half life - needs to be kept in patient for a long time
    • *very rigid placing of needles - possibility of them breaking
    • *needles have to be loaded mechanically - staff exposure
  4. Cs-137
    • *most widely used*
    • *most common source for afterloading machines*

    • 30 years
    • 662 kv
  5. advantages of cs 137
    • *longer half life than some - doesn't need to be replaced as often
    • *widely available
    • *low (photon) energy - storage not an issue
  6. Ir - 192
    • 74 days
    • 370 kv

    -typically temp. placement/use for H/N and breast
  7. Co-60
    • 5.26 years
    • 1.25 Mv

    not common for brachy - used for Cobalt-60 machine
  8. Au-198
    • 2.7 days
    • 412 Kv

    • *ideal source for permanent placement (b/c of short half life)
    • *prostate - permanent seeds
  9. I-125
    • 60.2 days
    • 35.5 Kv

    • *prostate seed implants
    • *ocular and uveal melanomas

    • *daughter from xenon124 (gas)
    • *lowest energy of brachy source
  10. those with intracavitary implants my leave the hospital/go home as outpatient once their source activity goes below....
    • 30 mCi
    • (must be below 30/30mCi and up =hospital)
  11. most common application/type of brachytherapy?
    • interstitial
    • -needles, wires, catheters right in the tissue
    • Ex: prostate, H/N, breast, soft tissue sarcomas
  12. most common intracavitary treatment
    cervical
  13. intralumenal treatments
    esophagus, bronchus, rectum, uterus, endometrium
  14. intravascular
    • -in a vessel, use intravascular stents to reopen occluded vessels
    • -source placed in or next to coronary vessel to oppen it up
  15. topical treatments
    pterygiums/eyes, skin cancers, keloids
  16. 1 Ci= ___________dps
    3.7x1010 dps

    unit of radioactivity = Ci (usually rep'ed as mCi)

    allows us to measure source strength (strength defined as # of disintegrations per unit time)
  17. SI unit of radioactivity
    • Bq
    • 1 Bq= 1 disintegration/second

    allows us to measure source strength (strength defined as # of disintegrations per unit time)

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