Need to Know Flashcards
Protons have a ____ charge
Positive
Neutrons have a _____ charge
No Charge
Electrons have a ______ charge
Negative
Half life order from least to most:
Y, Au, I131, Pd, Sr-89, I125, Ir, Co, Sr-90, C, Ra
-Yttrium (Y-90)
-Gold (Au-198)
-Iodine (I-131)
-Palladium (Pd-103)
-Strontium (Sr-89)
-Iodine (I-125)
-Iridium (Ir-192)
-Cobalt (Co-60)
-Strontium (Sr-90)
-Cesium (C-137)
-Radium (Ra-226)
Half life order from least to most (numbers): Y, Au, I131, Pd, Sr-89, I125, Ir, Co, Sr-90, C, Ra
-2.67 days (Y-90)
-2.7 days (Au-198)
-8 days (I-131)
-17 days (Pd-103)
-50.5 days (Sr-89)
-59.4 days (I-125)
-73.8 days (Ir-192)
-5.26 years (Co-60)
-28 years (Sr-90)
-30 years (C-137)
-1,622 years (Ra-226)
Tx area for: Y-90 (Yttrium) =
Liver and lymphoma tx
Tx area for: Au-198 (Gold) =
Prostate seeds
Tx area for: I-131 (Iodine) =
Thyroid
Tx area for: Pd-103 (Palladium) =
Prostate implants
Tx area for: Sr-89 (Strontium) =
Bone met pain
Tx area for: I-125 (Iodine) =
Prostate implants
Tx area for: Ir-192 (Iridium) =
HDR tx, nylon ribbons w seeds
Tx area for: Co-60 (Cobalt) =
External beam tx
Tx area for: Sr-90 (Strontium) =
Cancers in the eye
Tx area for: C-137 (Cesium) =
Brachytherapy for cervix or uterus
Radium is the ____ isotope
Original
4 R’s of Radiation
-Repopulation
-Redistribution
-Repair
-Reoxygenation
Repopulation is:
Remaining cells undergo mitosis to repopulate tissues
Redistribution is:
Cells transition into a more radiosensitive cell cycle (easier destruction)
Repair is:
Healthy tissues use O2 to repair, malignant cells are hypoxic and cannot repair
Reoxygenation is:
Malignant (hypoxic) cells become radiosensitive by O2
Linear energy transfer (LET):
Rate of energy deposited into material as radiation travels through it
Hounsfield Units in tissue:
-1000 = air
-400/-600 = lung
-50/-100 = fat
0 = water
+15 = CSF
+30/+45 = blood
+50 = muscle
+1000 = dense bone
2 types of electron interactions:
Bremsstrahlung, Characteristic
Bremsstrahlung Interaction:
electron interacts near nucleus by slowing, but never directly interacts with it, instead changes direction creating brem x-ray
Characteristic interaction:
electron interacts with orbiting electron from either the K, L, M shell. K shell creates the highest energy photon and can be used for diagnostic X-rays, not therapeutic
Photon interactions:
Coherent scatter, Compton scatter, photoelectric effect, pair production, photodisintegration (photonuclear)
Coherent Scatter:
Photon interacts with OUTER shell electron, changes direction with NO energy lost
-creates excitation
-low energies <10 kEv
Compton Scatter:
Photon interacts with OUTER shell, changes direction with SOME energy lost
-most common interaction in radiation therapy
Photoelectric Effect:
Photon interacts with INNER shell electron, energy is ABSORBED by the electron and then EJECTED as a photoelectron
-characteristic interaction is a secondary effect to fill the gap
-most common interaction in diagnostic radiation
Pair production:
Photon interacts with the NUCLEUS, disappearing and reappearing as an ELECTRON PAIR (positron + electron)
-threshold : >1.022 MeV
Photodisintegration (photonuclear):
Photon interacts with NUCLEUS releasing NEUTRON
-occurs in high Z# material + energies >10 mV
Cell Cycle:
M, G1, S, G2
Most radioresistant cell cycle phase:
S
Most radiosensitive cell cycle phase:
M, G2
Law of Bergonie and Tribondeau
Rapidly proliferating/dividing cells (ie. stem, precursor) are easily affected by radt compared to mature cells (kidney, liver, muscle)
Dose-response curves:
Linear Threshold
Linear Non-threshold
Non-Linear Threshold
Non-linear non-threshold
Linear:
response is directly proportional to the dose received
Non-linear:
response is not proportional to the dose received
Threshold:
response does not occur before a specific dose (threshold)
Non-Threshold:
response can occur before a certain threshold (can occur at any time)
Example of a linear non-threshold model:
Incidence of cancer with radiation exposure
Example of a linear threshold model:
Erythema occurring after 1600 cGy
After radiation damage cells either ____ or _____
regenerate or repair
regeneration after damage is
cells being replaced by the same cell type
repair after damage is:
cells being replaced by different cell type (causes fibrosis and scarring)
Somatic Effects:
-early
-late
-stochastic
-deterministic
Early effects:
Occur within 6 mo of tx (ie. erythema)
Late effects:
Occur after 6 mo. of tx (ie. scarring)
Stochastic effects:
Linear, non-threshold. NON-PREDICTABLE
The chance of the effect depends on the dose (ie. more exposure to radiation = more likely to develop cancer)
Deterministic effects:
Non-linear, threshold. PREDICTABLE
The chance of the effect depends on the severity of dose (ie. cataracts develops at a certain threshold with certain severity)
Absorbed dose:
Energy absorbed in MATTER
SI: Gy / Traditional: rad
Dose equivalent:
Energy absorbed by a PERSON
SI: sV / Traditional: rem
Exposure:
Ionizations in air
SI: Coulomb/kilo / Tradiitonal: Roentgen
Tissue weighting:
Bone/skin: 0.1
Bladder/breast/liver: 0.05
Bone marrow, colon, lung: 0.12
Gonads: 0.20
Cerrobend is made of:
BLT w Cheese
Bismuth (50%)
Lead (27%)
Tin (13%)
Cadmium (10%)
1 Gy =
1 sV
100 cGy
100 rad
1 sV =
1 Gy
100 rem
1,000 mSv
1 rem =
1 rad
10 mSv
1,000 mrem
Cardinal Principles of ALARA:
Time, Distance, Shielding
OCCUPATIONAL exposure limits:
Annual: 5 rem (50 mSv)
Cumulative: 1 rem x age
Lens of Eye: 15 rem
Skin, Hands, Feet: 50 rem
PUBLIC exposure limits:
Annual (frequent): 0.1 rem (1 mSv)
Annual (infrequent): 0.5 rem (5 mSv)
Lens of eye: 1.5 rem
Skin, Hands, Feet: 5 rem
** remember 10x less than occupational exposure **
Barrier for alpha rays:
Paper/skin
Barrier for beta rays:
Aluminum
Barrier for gamma rays:
Lead
Barrier for neutrons:
Concrete
Radiation area:
> 0.005 rem/hr
High radiation area:
> 0.1 rem/hr
