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Radiation Therapy

Comprehensive Review of Radiation Therapy for CQR studying

1 Curie (Ci) = 3.7 x 10^10 bq (dps)
1 mCi = 3.7 x 10^7 bq (dps)
1 Roentgen (R) = 2.58 x 10^-4 C/kg or 0.96 cGy (or rads), Unit of Exposure, amount of ionization produced by a beam of radiation in AIR, For >1 MeV, 1 R in Air represents approx. 0.96 cGy in Tissue
Rad = 100 erg/g
Gy = 1 J /kg
Dose Equivalent = absorbed dose in Gy x quality factor
Half Life (T1/2) = ln2 / λ
Decay Constant (λ) = 0.693 / T1/2 or ln2 / T1/2
HVL (Half Value Layer) = 0.693 / µ, Reduces the exposure rate (intensity) by one-half
ln2 = 0.693
1 Sieverts (Sv) = 100 rem
1 Gray (Gy) = 100 rad
Quality Factors = Xray, Gamma, Beta = 1, Alpha = 20, and Neutrons, Protons = 10 (Protons sometimes = 1 or 2)
Dose Equivalent (100 rem=1Sv) = Absorbed Dose (100 rad=1Gy) x Quality Factor
Inverse Square Law Formula = I1 / I2 = (D2 / D1)^2 , I=Intensity, D=Distance, 1=old, 2=new, *Don't forget to square the distance
Inverse Square Law Definition = The intensity of radiation at a given distance from a point source is inversely proportional to the square of the distance. Increasing distance, reduces the intensity.
Relative Biologic Effectiveness (RBE) = Dose in Gy of 250 kVp / Dose of test radiation
Percentage Depth Dose (%DD) = %DD = TD-Absorbed (Tumor dose) / GD-Prescribed (Given dose) times 100 if decimal form
Applied Dose = Tumor Dose / %DD
SSD MU Formula MU = Dose / %DDxBSFxCFxOPxTFxWF (Back scatter factor, Correction Factors, Output factor, Tray Factor, Wedge Factor)
OER = Oxygen Enhancement Ratio = Dose without O2 / Dose with O2
Transmission Factor = Dose with device / Dose without device
Field Magnification = Image Size / Object Size
FS1 / SSD1 = FS2 / SSD2
Kwashiorkor Protein malnutrition
Marasmus Calorie & Protein malnutrition
Undifferentiated Immature & Unspecialized (ex: stem cell, spermatogonia, erythroblast)
Differentiated Specialized function (ex: spermatozoa, erythrocyte)
L'Hermitte's Electrical shock down body when head is flexed (ex: spinal cord compression or XRT of C or Upper T Spine)
Trismus Difficulty opening mouth, Jaw spasm (ex: XRT chewing muscle)
Tenesmus Spasm of anal or vesical sphincter with pain (ex: XRT Pelvis, desire to empty bladder or bowel)
Alpha Positive, 2 protons+2 neutrons, Great mass, Little penetration
Beta Negative, Little Mass, Great penetration
X-ray Manmade, Originates in electron cloud in tube
Gamma NOT manmade, Originates in nucleus
Low LET (Linear Energy Transfer) (Xray, Gamma), Sparse ionizing radiation separated by long distances
High LET (Linear Energy Transfer) (Alpha, Neutrons), More damage, Dense ionization separated by short distances
Front pointer To find isocenter
Back Pointer To find exit point
Beam Splitter (Half-beam blocks) Splits beam in half to get sharper edge without divergence (XRT H&N & Breast)
Partial Transmission Blocks Used for beam modification rather than shaping
Attenuation Process by which a beam of radiation is reduced in intensity when passing through some material
SAD Source to Axis Distance - 100 cm on Linear Accelerator, 80 cm on Cobalt
Bolus Tissue equivalent used to raise surface dose or compensate or deficit tissue
Compensator Device used to manipulate the dose distribution of the beam
Field Size Dependence Radiation doses affected (aka: Central axis dose increases as...field size increases)
Mayneord's Factor Only used for Extended SSD treatments, a conversion used to show the amount the %DD & MU will increase as the SSD increases
Cobalt Dmax 0.5 cm
Dmax The reference depth is normally the level of maximum dose, Dose decreases as the depth increases
4MV Dmax 4MV = 1.0 cm
6 MV Dmax 6MV = 1 .5 cm
10 MV Dmax 10 MV = 2.5 cm
15 MV Dmax 15 MV = 3.0 cm
20 MV Dmax 20 MV = 4.0 cm
25 MV Dmas 25 MV = 5.0 cm
Monitor Units (MU) Unit of Time, Basic unit of machine output
Cerrobend (Lipowitz) BLT with Cheese, 50% Bismuth, 26.7% Lead, 13.3% Tin, 10% Cadmium(toxic)
Custom Blocks melt at 70ºC (158º F) - Low melting point
C - A - U - T - I - O - N C=change in bowel or bladder habits, A=a sore that does not heal, U=unusual bleeding or discharge, T=thick or lump anywhere, I=indigestions/difficulty swallowing, O=obvious change in wart or mole, N=nagging cough or hoarseness
ALARA As low as reasonable achievable
IMRT Intensity Modulated Radiation Therapy
ALL Acute Lymphatic Leukemia - Most common in children
LD 50/30 Lethal dose - 50% will die in 30 days (humans 250-300 cGy total body dose)
LD 50/60 More frequently used - 50% will die in 60 days (humans 350-400 cGy total body dose)
Best way to minimize patient movement Communication
Single most important way to prevent the spread of infection Handwashing
Most RadioResistant Cell Cycle S cell cycle (broadest shoulder)
Most RadioSensitive Cell Cycle M (mitosis) cell cycle (shallow shoulder/steepest slope), Then G2
Most common site for Breast cancer Left Breast, Upper Outer Quadrant
Cobalt Beam Polyenergetic or Heterogeneous because more than one energy is decaying from isotope, for XRT purposes 2 energies are averaged to 1.25 MeV
Need High Radiation Area Sign if: Greater than 100 mrem/hr
Most RadioSensitve Organ Testes and Ovaries
Most RadioSensitive Cell Lymphocytes (WBC)
Which wedge tilts the most and what is it directly proportional to 60º wedge tilts the most, Higher the degree of wedge=The greater the Tilt
What corrects for divergence? Couch kicks, Independent jaws, Half beam blocks
Beam shaping should be how close to the patient's skin NOT closer than 15 cm from patient's skin
2D compensators Wedges - Cephalic/Caudal directions only
3D compensators For Right/Left directions only
Attenuation capability of Cerrobend 85% lead density, which means cerrobend blocks must be. 15% thicker than lead to achieve the same attenuation
Most common lymph node chain for H&N Jugulodigastric (Subdigastic), Also, Node of Rouviere (lateral retropharyngeal)
Most common lip carcinoma Men and Lower Lip
Most common site for Epstein Barr Virus Nasopharynx
The tolerance of radiation is inversely proportional to... the volume of the organ irradiated
5 stages of death and dying - Kubler-Ross DABDA = Denial/Shock, Anger, Bargaining, Depression, Acceptance
6 'Rights' of Drug Administration Right Patient, Drug, Dose, Route, Time, Documentation
3 Stages of Malignant Transformation (normal to malignant) 1. Initiation (altered DNA), 2. Promotion(acts on other cells/NOT DNA, 3. Progression (change to malignant, once detectable (1cm) contains 1 billion cancer cells
3 most common cancers in Men 1. Prostate, 2. Lung, 3. Colon
3 most common cancers in Women 1. Breast, 2. Lung, Colon
3 most common cancer deaths in Men 1. Lung, 2. Prostate, 3. Colon
3 most common cancer deaths in Women 1. Lung, 2. Breast, 3. Colon
Hyperfractionation Decrease in Dose/fx (below conventional 1.8-2 Gy, but More fractions, Allows higher total dose & tumor control without increasing late complications
Hypofractionation Increase in Dose/fx (higher than conventional 1.8-2 Gy, but Less fractions, Will lower the therapeutic ratio between tumors and late responding tissues, Used on Palliative cases where late effects are not a concern
Accelerated Fractionation Increased rate of dose delivery (above 10 Gy/week), Bad early effects, ^Dose/fx, ^Fx/day, ^Fx/week
Carcinoma spreads Centrifugally
Sarcoma spreads Longitudinally
Temporary Hair Loss Dose 20-40 Gy
Permanent Hair Loss Dose 55 Gy
Protraction Early Effects, Length of time which total dose is delivered
Fractionation Late Effects, When the total dose of radiation is divided into several, smaller doses over a period of several days, there are fewer toxic effects on healthy cells
RBC Male: 4.32-5.72 trillion cells/L (4.32-5.72 million cells/mcL), Female: 3.90-5.03 trillion cells/L
WBC 3.5-10.5 billion cells/L
Platelets 150-450 billion/L
Hemoglobin Male: 13.5-17.5 grams/dL (135-175 grams/L), Female: 12.0-15.5 grams/dL
Hemotocrit Male: 38.8-50.0 percent, Female: 34.9-44.5 percent
BUN 10-20 mg/dl
1 J/kg Gray
100 ergs/g Rad
If %DD is 0.80, it means... 80% is absorbed (transmitted), and 20% is attenuated (reduced, surface dose)
Therapeutic Ratio Formula = NTTD (healthy) / LD (tumor)
Split Field Test Test for longitudinal displacement of the collimator for jaw symmetry, Done using plastic-covered blocked xray film with beams 180º apart, checks the alignment between 2 parallel-opposed fields
Misalignment of Split Field Test is caused by: 1. Focal spot displacement, 2. Misalignment of collimator jaws/collimator, 3. Gantry Rotation Axis
Superficial 50-140 kVp, 15-20 cm distance, Dmax=0, 1-6 mm Al
Orthovoltage 150-500 kVp, 50-70 cm distance, Tin (by xray target), 1-4 mm Cu, Tin (closest to patient), Thoraeus Filter
VanDeGraff 2-3 MeV, 100 cm distance, Used to treat Seminoma
Betatron Circular orbit, Noisy, Used for Industrial radiation
Cyclotron Protons, 15-50 MeV, Less treatments needed
Radium (Ra226) Half Life (T1/2) 1600 Years, No longer used for treatments
Cesium (Cs137) Half Life (T1/2) 30 Years, Breast/Cervix, Tubes/Needles
Strontium (Sr90) Half Life (T1/2) 28 Years, Pterygium (eye), Topical
Cobalt Half Life (T1/2) 5.26 Years, 1.25 MeV, Encased spheres
Iridium Half Life (T1/2) 74 days, Breast/Cervix, Seeds
Strontium (Sr89) Half Life (T1/2) 52.7 days, Bone, Solution/Intravenous
Iodine (I125) Half Life (T1/2) 60 days, Prostate, Seeds
Palladium (Pd103) Half Life (T1/2) 17 days, Prostate, Seeds
Phosphorus (P32) Half Life (T1/2) 14.3 days, Ovarian, Solution/Injection
Iodine (I131) Half Life (T1/2) 8 days, Thyroid, Capsule
Radon (Rn222) Half Life (T1/2) 3.83 days, No longer used (Gold 198 replaced it)
Gold (Au198) Half Life (T1/2) 2.7 days, Prostate, Seeds
Yttrium (Y90) Half Life (T1/2) 64 HOURS, Liver, Topical
TEDE Limits Total Effective Dose Equivalent Limits
Controlled Area - TEDE Limits 0.1 rem/week
Uncontrolled Area - TEDE Limits 0.01 rem/week
Cumulative (Lifetime) - TEDE Limits 10 mSv (1 rem) x (Age in years)
Stochastic - Occupational Workers (Annual - only job exposure) - TEDE Limits 50 mSv (5 rem)
Nonstochastic - Occupational Workers (Annual - only job exposure) - TEDE Limits Threshold=500 mSv (5 rem), LensEye=150mSv(15rem), Organs=500mSv(50rem)
Public Annual - TEDE Limits Frequent=1mSv(0.1rem), Infrequent=5mSv(0.5rem), LensEye=15mSv(15rem), Organs=50mSv(5rem)
Embryo-Fetus TEDE Limits 5mSv(0.5rem), Monthly=0.5mSv(0.05rem)
2 Types of Gas-filled radiation measuring devices 1. Ionization Chamber (Cutie pie), 2. Geiger-Muller Counter
Ionization Chamber Two electrodes and applied voltage, Measured in mR/hr (not good for low levels), Pocket dosimeter (type of ionization chamber)
Geiger-Muller Counter Uses more voltage so secondary ions, More sensitive (good for low levels, but not high)
4 Types of Personnel Monitoring devices 1. Film Badges, 2. Pocket Dosimeter, 3. Thermoluminescent Dosimeter (TLD), 4. Optically Stimulated Luminescent Dosimeter (OSL)
Film Badges Crystal Silver Bromide, Metal filters and film packet, Low (do not penetrate filters, but gets where no filters), Med (penetrate tin but not lead filter), High (penetrates all filters)
Pocket Dosimeter Can be read immediately, NO permanent record, Expensive, Errors
Thermoluminescent Dosimeter (TLD) Crystals of Lithium Fluoride, Gives off light when heated that is proportional to amount of radiation, Badges/Rings
Optically Stimulated Luminescent Dosimeter (OSL) Aluminum Oxide, Laser reads luminescent in proportion to radiation exposure, Extremely accurate, Luxel by Landauer-Hexagon
Xray's wavelength Short wavelength
Xray production 99% heat, only 1% xray (75-80% Brems)
Energy and Frequency Directly proportional
Wavelength Inversely proportional to Energy and Frequency
Stochastic Randomly determined, Random probability distribution or pattern, May be analyzed statistically but may not be predicted precisely
Nonstochastic Fixed probability determined, Threshold dose to which the effects will not occur, Threshold dose and Time over which the dose was received cause the effect (ex: acute vs. chronic exposure)
Examples of Nonstochastic Effects Ex: erythema, cataract formation, sterility, radiation sickness and death. Threshold dose and Time over which the dose was received cause the effect (ex: acute vs. chronic exposure)
Lead High Atomic #=More Dense,=Attenuates more, Wall=LowAtomic#=LowerAttenuation
5 Types of Photon Interactions 1. Coherent Scatter (Rayleigh/Thompson/Classical/Simple), 2. Photoelectric (Einstein's Nobel Prize, 3. Compton (Incoherent), 4. Pair Production, 5. Photodisintegration
Coherent Scatter (Rayleigh/Thompson/Classical/Simple) 1-50 kVp, Interacts with: Atoms/Electrons oscillates, Energy: No change/Slight direction change, By-product: None
Photoelectric (Einstein's Nobel Prize) <1 MeV, Interacts with: INNER K-shell Electron, Energy: Changed/All e- transferred/Total Absorption, By-product: Characteristic Photons or Auger Electrons
Compton (Incoherent) 200 kVp-2 MeV, Interacts with: OUTER shell Electrons/Free e-/Low binding energy, Energy: Reduced/Partial Energy Transfer, By-product: Compton Scattered electron/photon
Pair Production 1.022 MeV, 3-10 MeV is most common, Interacts with: Nucleus, Energy: Absorbed & transforms into positron & negatron/Important at 10 MeV/Predominant at >50 MeV, By-product: Positron & Negatron (annihilate into two 0.511 MeV photons
Photodisintegration >10 MeV, Interacts with: Nucleus & emits neutrons & gamma rays, Energy: Absorbed by Nucleus/High Z material/Neutron contamination hazard, By-product: Neutrons/possible protons/Proton-Neutron(Deuteron)/Alpha
2 Types of Electron Interactions 1. Collision (Characteristic), 2. Radiative (Bremsstrahlung)
Collision (Characteristic) Most common Electron Interaction, Electron beam lose energy by collision interaction more than radiation interaction due to low Z # of tissue, Electron loss is 2 MeV/cm of tissue
Radiative (Bremsstrahlung) Increase with increasing energy and increasing Z# of absorber
Two types of Electron Collision Interactions: 1. Elastic (incoming electrons give up all of its energy (No kinetic energy lost), 2. Inelastic (allow bounce back where the incoming electrons share its energy)
Practical range of electrons = MeV / 2
Depth of 80% isodose line = MeV / 3
Depth of 90% isodose line = MeV / 4
Electron Lead Shielding in mm = MeV / 2
Tolerance Doses (TD5/5) = The radiation dose that would result in 5% risk of severe complications within 5 years after irradiation
Testes - TD 5/5 - TD 50/5 1-2 Gy
Ovaries - TD 5/5 - TD 50/5 6-10 Gy
Eyes (Lens) - TD 5/5 - TD 50/5 6-12 Gy
Kidney - TD 5/5 - TD 50/5 20-30 Gy
Thyroid - TD 5/5 - TD 50/5 20–40 Gy
Lung - TD 5/5 - TD 50/5 23–28 Gy
Skin - TD 5/5 - TD 50/5 30–40 Gy
Liver - TD 5/5 - TD 50/5 35–40 Gy
Bone Marrow - TD 5/5 - TD 50/5 40–50 Gy
Heart - TD 5/5 - TD 50/5 43–50 Gy
Gastrointestinal - TD 5/5 - TD 50/5 50–55 Gy
Vasculoconnective tissue - TD 5/5 - TD 50/5 50–60 Gy
Spinal Cord - TD 5/5 - TD 50/5 50–60 Gy
Brain - TD 5/5 - TD 50/5 55–70 Gy
Peripheral nerve - TD 5/5 - TD 50/5 65–77 Gy
Mucosa - TD 5/5 - TD 50/5 65–77 Gy
Bone and cartilage - TD 5/5 - TD 50/5 >70 Gy
Muscle - TD 5/5 - TD 50/5 >70 Gy
Dose for Skin Reactions 15-30 Gy=Hair Loss, 20Gy=Erythemia, 30Gy=Dry Desquamation, 40Gy=Wet Desquamation
Increase kVp = Penetration ⬆️, Contrast ⬇️, More scatter, Directly Proportional to=kvP,Penetration,&Scatter, ⬆️kVP=⬆️Penetration=⬆️Scatter
Increase Mass = Penetration ⬇️, Contrast ⬆️(for Larger patients), Directly Proportional to=Mass,Contrast,&Density, ⬆️Mass=⬆️Density=⬆️Contrast
CT Hounsfield Units - Air, Water, Bone Air = -1000, Water = 0, Bone = +1000
Bremsstrahlung Inelastic electron nuclei collisions, Most important method for producing xray beams, high z# material (lead)
Compton Dominant process for energy level use in RT, Most common interaction in RT
Beam Modifiers 1. Shielding (Cerrobend blocks, Asymmetric jaws, MLC), 2. Compensation (Compensators, Bolus), 3. Wedge Filtration (Wedges), 4. Flattening (Flattening Filters)
Oxygen Enhancement Ratio (OER) = Dose withOUT O2 / Dose WITH O2
Organ At Risk (OAR) = Dose OFF center / Dose at CAX
Attenuation Factors (Wedge/Tray) = Dose WITH device in radiation beam / Dose withOUT device in radiation beam
TD (Dose at Depth) = Given (Dmax Dose) x %DD
Protons High LET, Delivers energy all at once due to heavy particle and Braggs Peak
Gross Clinton Planted Trees Irradically Gross Tumor, Clinical Target (GTV + micro), Planned Target (GTV+CTV+move), Treated Volume (95% isodose line), Irradiated Volume (All Treated)
Electron Skin Treatments En Face = Gantry parallel to pt's skin, central ray perpendicular to pt's skin
QA Tolerances - Crosshairs, Light Field, Collimator, & ODI/SSD Within 2 mm
Back Scatter Factor (BSF) BSF ⬆️ = Field Size i⬆️, ⬆️beam energy = scatter ⬇️ = BSF ⬇️
Dose Rate Constancy (Electron & Xray) - DAILY 3%
Electron Flatness & Symmetry (Monthly) 3%
Xray Flatness & Backup Timer/MU (Monthly) 2%
How often for Isocenter Check (Gantry/Collimator/Couch/Table/Axes) Yearly - 2mm
Linear Leakage 0.1% of useful beam at 1m
Sign - Caution Radiation Area 5-100 mrem/hr
Sign - Caution HIGH Radiation Area >100 mrem/hr
Sign - Grave Danger Radiation Very High >500 rem/hr
4 Nonspecific Phase Chemo Drugs 1. Alkylating Meds, 2. Antitumor Antibiotics, 3. Hormonal Meds, 4. Nitrosoureas
Alkylating Meds Affects the synthesis of DNA by cross linking to inhibit cell reproduction, Cisplatin (plantinol), Nitrogen mustard, Cyclophosphamide (cytoxin), Alopecia
Antitumor Antibiotics Interferes with DNA & RNA synthesis, gonadal suppression, Doxorubicin (Adriamycin), Bleomycin Sulfate (Blenoxane), Daunorubicin (Cerubidine), Heart & Lung Problems, Anaphylaxis
Hormonal Meds Suppresses the immune system & blocks normal hormones, Changes balance & slows growth, Sex characteristics, electrolyte imbalance, gyneomastia, weight gain, hypertention, hot flashes, Hydrocortisone, Prednisone, Tomoxifin (Nalvadex-decreses estrogen)
Nitrosoureas Can cross the Blood brain barrier, Inhibits DNA & RNA sythesis, Carmustine, Lomustine
2 Specific Phase Chemo Drugs 1. Plant Alkaloids (M phase), 2. Antimetabolite (S phase)
Plant Alkaloids (M Phase) Prevents cell division causing cellular death, Neurotoxicity, Ptosis (drooping eyes), Hoarseness, Neuropathy, Taxol (anaphylaxis), Vincristine (oncovin)-Most common for neurotoxicity, Vinbsislasine
Antimetabolite (S Phase) Replaces normal proteins required for DNA synthesis to halt synthesis of cell protein, 5FU (fluorouracil, adrucil, Alopecia, Stomatis (mouth sores), diarrhea, Methotrexate (Folex)-Alopecia, Gastrointestional, Skin Toxicity
Candidiasis Thrush
Stomatitis Mouth Sores
Normal Respiration (breaths/min) Adult = 12-20, Child = 22-50
Normal Pulse (beats/min) Adult = 60-100, Child = 100-140
Normal Blood Pressure (Systolic/Diastolic) Adult = 120/80, Child = 100-60
Normal Temperature 98.6º F (37º C)
Hypoglycemia (Low Blood Glucose) Result of Insulin overdose, Cool Moist Pale Skin, Blurred Vision, Difficulty Talking, Blurred Vision, Increased Heart Rate, Eat or drink Glucose rich food
Hyperglycemia (High Blood Glucose) Hot Dry Flushed Skin, Increased thirst (Polydipsia), Nausea, Vomiting. Polyuria (Increased urine), Need IV Fluids and possibly insulin
Hypovelemic Direct loss of circulating blood volume, Anxiety
Septic Caused by decreased tissue perfusion and oxygen delivery from severe infection
Asepsis Free from all disease
Medical Asepsis (clean technique) Helps reduce number and hinder transfer of pathogens
Surgical Asepsis Free of all Microorganisms
Sterile Technique Process that Destroys all microbial life forms, Autoclave (heat, steam, pressure), Gas, Chemicals (Amphyl, Cidex)
Disinfection Process that Reduces microbial life forms, Boiling water, Liquid chemicals, Chlorine compounds
Nosocomial Infections Infections that develop/acquired in the hospital
Universal Precautions Prevent transmission of HIV, hepatitis, and other pathogens that spread through bodily fluids, Use protective barriers.
Strict Isolation Spreads by direct contact or air, Gown, Gloves, Mask required, Private room with door closed and negative air flow (special ventilation), Articles from room labeled and bagged
Reverse (Protective) Isolation To protect immunosuppressed patients from infection, Mask, Gown, & Sterile Gloves, Patient isolated from dust, dirt, plants, wet areas
Contact Isolation Spreads by close or direct contact, Mask, Gown, Gloves if close contact
Respiratory Isolation Spreads by large droplets in short distances, Private Room required, Mask required if close contact (No gown or gloves)
TB (Tuberculosis) / Acid-fast Bacilli (AFB) Isolation Spreads by airborne (Long), Private room with door closed and negative air flow, Mask NOT adequate, Respirator recommended (NO gown or gloves)
Enteric Precautions Spread by direct or indirect contact with fecal material, ONLY mask, gown, and gloves if in contact with fecal material
Drainage and Secretion Precautions Spread by direct/indirect with secretion/drainage, ONLY mask, gown, and gloves if in contact with infectious material
6 Cycles of Infection 1. Causative Agent (source), 2. Mode of Transmission, 3. Reservoir (for microorganism growth, 4. Portal of Entry, 5. Susceptible Host, 6. Portal of Exit
Fomite Objects or materials that are likely to carry infection, such as clothes, utensils, and furniture
Vector Organisms, such as intermediate parasites or microbes, but it could be an inanimate medium of infection such as dust particles
5 Methods of Transmission 1. Contact (Direct & Indirect)-Most common nosocomial, 2. Droplet (Short-doesn't linger), 3. Airborne (Long-Days), 4. Common Inanimate Vehicles (food, blood, feces), 5. Vector Borne (insect or animal)
6 Intentional - Tort Law (legal wrong) 1. Civil Assault (threaten), 2. Civil Battery (touch), 3. False Imprisonment (confinement), 4. Libel (Written), 5. Slander (Oral), 6. Invasion of Privacy (Pt exposed/Info released)
2 Unintentional - Tort Law (legal wrong) 1. Negligence (neglect), 2. Malpractice (Lack of skill/Misconduct)
Doctrine of Respondent Superior holding employer responsible for negligent employee
Res Ipss Loquitor "the thing speaks for itself", Court can decide, No need for witness present
Doctrine of Forseeability Knowledge of actions or lack of information that could cause injury
Pacemaker Dose Most <500 cGy so blocking required
Latent Period for Cataracts 200 cGy=8-35 yrs, 250-650 cGy=8 yrs, 650-1150 cGy = 4 yrs
Hormesis The hypothesis that low doses of radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease
Metaplasia Abnormal change in nature of tissue (ex: change cell type)
Anaplasia Loss of cell differentiation, hard to define origin (rapid growth of malignant tumor)
Kyphosis Excessive Convex Spine Posteriorly (hunch back)
Lordosis Excessive Convex L-Spine (arch back)
Reticuloendothelial cells Kupffer's cells in Liver
Crypt Cells Peyer patches in Small Intestines
Lymph Flow Interstitial > Capillaries > Afferent vessels > Nodes > Efferent vessels > Lymphatic Trunk > Collecting Ducts > Subclavian Veins
# of Bones 206 bones (29 Skull, 14 Facial, 33 Vertebral, 12 pairs of Ribs), 7 C-spine, 12 T-spine, 5 L-spine, 4 Coccygeal, C1 Atlas-Yes, (No body), C2 Axis-No, (Ondontoid-dens), 7 True Ribs, 8-12 False Ribs, 11-12 Floating Ribs
Genetic Restitution Single radiation-induced break into 2 fragments (can join)
Genetic Structural Changes Damaged cells can survive and may or may not be able to reproduce to produce more damaged cells
Genetic Gene Amplification DNA replication becomes selective and reproduce at increased rate
Genetic Chromosome Transposition Broken cell fragment tries to repair and rejoin
Genetic Gene Transposition Cell creates wrong genetic code
Genetic Mutation Missing an element
Electromagnetic Spectrum Colors Roy G Biv: Red, Orange, Yellow, Green, Blue, Indigo, Violet
Electromagnetic Spectrum Types R MIVUX G: Radiofrequency (MRI), MIcrowaves, Infared, Visible Light, Ultraviolet, Xray, Gamma
Xray = Short wavelength, High Energy & Frequency
3 Stages of Tumor Development (Carcinogenesis) 1. Initiation, 2. Promotion, 3. Progression
Initiation - Tumor Development (Carcinogenesis) Direct exposure of DNA to a carcinogen, change must be permanent and unrepairable
Promotion - Tumor Development (Carcinogenesis) Threshold effect then enhances growth, effects may be reversible if period between
Progression - Tumor Development (Carcinogenesis) Detectable tumor that must develop own blood supply to survive
3 Embryo/Fetus Stages of Development for 250 cGy 1. Preimplantation, 2. Organogenesis, 3. Fetal
Preimplantation Stage of Development - Embryo/Fetus for 250 cGy Day 0-10, No growth retardation if brought to term, mostly death
Organogenesis Stage of Development - Embryo/Fetus for 250 cGy Day 10-Week 6, Neonatal death, CNS and Skeletal abnormalities
Fetal Stage of Development - Embryo/Fetus for 250 cGy Week 7-Until Birth, Mental retardation & Microcephaly, LD50 equal to adults
5 Cellular Stage of Radiosensitivity (from most sensitive to lease) - Lymphocyte is exception 1. VIM, 2. DIM, 3. Vessel/Connective, 4. RPM, 5. FPM
VIM - Cellular Stage of Radiosensitivity Most sensitive, Type A Spermatogonia, Basal cells, Crypt cells
DIM - Cellular Stage of Radiosensitivity Myelocytes and Intermediate Spermatogonia
Vessel/Connective - Cellular Stage of Radiosensitivity Endothelial cells and Fibroblasts
RPM - Cellular Stage of Radiosensitivity Lymphocytes (BUT Sensitive) and Parenchymal of Liver
FPM - Cellular Stage of Radiosensitivity Least sensitive, Muscle, Nerve, Erythrocytes
Dose / Response Relationship 10 Gy for Early effects, 3 Gy for Late effects, *So late responding tissues are more sensitive to changes in fractionation.
Biological Effect of Radiation Directly proportional to Dose & Volume --- Effect ⬆️as Dose & Volume⬆️, Inversely proportional to Time of administration ---Longer the time, ⬇️ the effect
Histology - Kidney 80% Renal Cell-Adenocarcinoma, 5% Renal Pelvis-mostly Transitional
Histology - Ureters Transitional
Histology - Urinary Bladder Transitional
Histology - Prostate Adenocarcinoma
Histology - Cervix (SMA 12 serum test) Squamous Cell Carcinoma (SCC) - begins in endocervical canal (external os)
Histology - Vaginal Squamous Cell Carcinoma (SCC) - posterior upper third of vagina
Histology - Uterus Adenocarcinoma (most common), Fundus (upper part of uterus), *Clear cell & Papillary Carcinoma - poor prognosis, Adenocanthoma (benign or combo), Secretory Adenocarcinoma, Leiomyosarcoma (smooth muscle)
Histology - Ovarian (CA125 serum test) Epithelial Carcinoma (most common), (Stomal & Germ cell-less common)
Histology - Larynx Glottic (most common-65%), Supraglottic (2nd), Subglottic (3rd),
Histology - Breast Infiltrating Ductal Carcinoma (IDC) (most common), Infiltrating Lobular Carcinoma (2nd), Mucinous, Colloid, Tubular, Papillary Carcinoma
Histology - Esophagus 90% Squamous Cell Carcinoma (SCC) (epithelial lining), 10%Adenocarcinoma (closer to stomach)
Histology - Stomach Adenocarcinoma, 95% Columnar (glanular epithelium), Lymphoma, Leimyosarcoma
Histology - Pancreas Adenocarcinoma, Islet cell (2 types)
Histology - Colo/Rectal 90% Adenocarcinoma, Lymphoma, Leiomyosarcoma
Histology - Anus Squamous Cell Carcinoma (SCC)
Nonstochastic Deterministic/Threshold dose required, EARLY effects, SEVERITY increases with dose.
Stochastic Nonthreshold, LATE effect, PROBABILITY increases with dose.
Total Body Irradiation 3 Stages & Symptoms 1. Prodromal (minutes-days)(N-V-D), 2. Latent (hours-weeks)(no symptoms, but damage), 3. Manifest Illness (hours-weeks)(organ system damage)(3 Syndromes)
3 Syndromes of Manifest Illness Stage of TBI 1. Hematopoitic (Bone Marrow) syndrome-1-10 Gy, 3 w-6 m if survive, 2. Gastrointestinal (Small Intestines) syndrome-10-50 Gy, death3-10 days, 3. Cerebrovascular (CNS) syndrome-⬆️10 Gy, death under 3 days
3 Main Factors Affecting Responses to Radiation 1. Physical Factors - LET, RBE, & Dose Rate, 2. Chemical Factors - Radiosensitizers, Radioprotectors, & Oxygen Enhancement Ratio (OER), 3. Biological Factors - Cell Cycle - How cells distributed in cell cycle and Sensitive of phase in cell cycle
LET Linear Energy Transfer (LET), High & Low LET, Rate of energy loss along the path of the particle
Low LET Electromagnetic radiation, X-ray & Gamma rays (short wavelengths, high energy), Sparse ionization over Long distances, Cause damage through indirect action over long distances, free radical damage
High LET Particulate radiation, Neutrons & Alpha particles (large mass, Dense over Short distances), More destructive than Low LET, lose energy fast, DNA death
Radiobiology Study of absorption, effects, and damage from ionizing radiation on living systems
Ionization Occurs when an electron is ejected from the shell of atom and becomes charged, which then interacts with matter causing damage to tissue in path
2 Basic Types of Interactions with Ionization 1. Direct (Deoxyribonucleic Acid-DNA damage), Alpha, Proton, Electron 2. Indirect - X-ray, Gamma, Neutrons, & Fast Electrons, free radicals interact w/H20, (hydroxyl & hydrogen peroxide), INDIRECT Action is leading cause of damage since bodies 80% water.
3 Cellular Responses to Radiation 1. Division (Mitotic Delay)-Most Common, 2. Interphase Death (NONmitotic), 3. Reproductive Failure (Mitotic Death)
Somatic Effect Radiation-Induced Cancer
Genetic Effect Offspring of person irradiated, genetic mutation
RBE Relative Biologic Effectiveness (RBE) - calculation comparing the effectiveness of different types of radiation to produce a specific biological response, RBE=Dose (Gy) of 250 kVp X-ray / Dose (Gy) Test Radiation
Dose Rate Effect Directly proportional to Field Size, Inversely proportional to Distance, High dose rate will produce more damage, Significant with low LET due to cellular repair, NOT relevant with High LET due to cell death
Radiosensitizers Most common is Oxygen, Oxygenation agents - Nitromidazoles
If cell survival curve has a shallower shoulder (increased survival), what cells are they? Hypoxic Cells
Radioprotectors Cysteine, Cysteamine, Amofostin (WR2721), DRF (Dose Reduction Factor)-used to determine the effectiveness of radioprotector
OER Oxygen Enhancement Ratio (OER) - hypoxic cells more resistant to radiation, Means Low LET (xray/gamma) 2 1/2-3 times more resistant to radiation than oxic cells
Oxygen Fixation Hypothesis Indirect damage from Low LET becomes permanent when oxygen is present
Law of Bergonie & Tribondeau States cells are more sensitive to radiation if they are Actively dividing, Have long mitotic life, and undifferentiated (embryo, young child)
Ancel & Vitemberger Revised Law Cell sensitivity depends on biological condition of cell, Damage is the same, but undetected until the cell divides
Rubin & Casarett Identified the 5 Cell Populations - Vegetative Intermitotic VIM, Differentiated Intermitotic DIM, Multipotential Connective Tissue, Reverting Postmitotic RPM, Fixed Postmitotic FPM
Most Radiosensitive Cell Cycle Phase M (Mitotic) Phase
Most Radioresistent Cell Cycle Phase S (Synthesis) Phase
Reason for Fractionation (fx) in Radiation Treatments (tx) Fx allow repair of sublethal damage to healthy cells, *Mitotic Index-proportion of cells in mitosis at any one time, If dose under 10 Gy, then cells can repair causing mitotic index to ⬆️ as delayed cells are allowed to progress into mitosis
Four R's of Radiobiology (5th discussed is Radiosensitivity) 1. Repair, 2. Reoxygenation, 3. Redistribution (Reassortment), 4. Repopulation
Repair - 1st R's of Radiobiology (NORMAL Cells), After radiation, damage is repaired as long as the injury was sublethal and there is rest period between exposures
Reoxygenation - 2nd R's of Radiobiology (TUMOR Cells), Occurs during rest period, Tumor cells generally become oxygenated after radiation is delivered contributing to radiosensitivity before next treatment
Redistribution (Reassortment) - 3rd R's of Radiobiology (Normal or Tumor cells), Relates to the Cell Cycles, Goal is to irradiate on daily basis in order to damage tumor cells as they enter sensitive phase (Mitosis) resulting in more tumor cell death
Repopulation - 4th R's of Radiobiology (Normal or Tumor Cells), Important reason for fractionation, Protraction (overall tx time), As healthy tissue is repopulating, undesirable tumor regrowth also can occur during tx
Protraction Overall treatment time, Prolonging total dose given over time
Standquist Isoeffect Led to Fractionation, NTTD (Normal Tissue Tolerance Doses) were established
Therapeutic Ratio Measures success potential of radiation using TLD (Tumor Lethal Dose), TR=NTTD/TLD
TD5/5 5% will have complications in 5 years
Ellis developed... NSD (Norminal Standard Dose), 2 flaws-neglected cell sensitivity & volume of tissue irradiated, Now, Biologic Effective Dose (BED) is used
BED Biologic Effective Dose (BED) - Aids treatment planning because it includes the aspects that Nominal Standard Dose (NSD) calculation lacks which is neglecting cell sensitivity & volume of tissue irradiated
2 Healing Processes of Radiation Exposure 1. Regeneration, 2. Repair
Healing Process of Radiation Exposure - Regeneration *Same cell type replaces damaged cell type, Most common in structures that received acute side effects and have actively dividing cells
Healing Process of Radiation Exposure - Repair *Different cell type replaces damaged cell type, Most common in radioresistent structures as a result of chronic, irreversible changes
Apoptosis Programmed Cell Death, Normal process by human body, cleans unwanted cells, Important for Tissue Homeostatis
Necrosis Accidental Cell Death, Caused by tissue damage due to cancer or radiation treatments
Candidiasis Thrush
Atlas Vertebra C1
Axis Vertebra C2 - Dens (Odontoid)-protrudes up through c1
External Anatomic Location - C4 Hyoid Bone
External Anatomic Location - C4-5 Thyroid Cartilage
External Anatomic Location - C4-5 Larynx
External Anatomic Location - C6 Cricoid Cartilage
External Anatomic Location - C7 Prominent Spinous Process
External Anatomic Location - T3 SSN (Suprasternal Notch)
What happens internally at level - T4 Clavicles & 1st ribs articulates
What is located internally at level T5 Carina (Bifurcation of Trachea)
External Anatomic Location - T9-10 Xiphoid Process
What is located internally at level - T11-L3 Kidneys
What happens at level L2 internally? Spinal Cord ends
External Anatomic Location - L3 Umbilicus
External Anatomic Location - L4 Illiac Crest
External Anatomic Location - S2 PSIS (Posterior Superior Iliac Spine)
External Anatomic Location - Coccyx Pubic Symphysis & Greater Trochanters
What quadrant - Liver & Pancreas Right Upper Quadrant
What Quadrant - Spleen & Stomach Left Upper Quadrant
Histology - Oropharynx Squamous Cell Carcinoma (SSC)
Histology - Maxillary Sinus Squamous Cell Carcinoma (SSC)
Histology - Hodgkins Lymphoma Reed-Sternberg Cells in lymph nodes
Histology - Wilm's Tumor Nephroblastoma (Kidney cancer in children), Unfavorable histologies - Anaplastic, Sarcoatoid, Clear cell, Rhabdoid
Esophagus - most common site 45% Middle, 40% Lower, 15% Upper (worst prognosis)
Stomach - most common site 50% Pylorus (lower, leads to duodenum), 25% Lesser Curvature, 10% Cardia (Upper-worst prognosis), 2-3% Greater Curvature
Pancreas - most common site 70% head of pancreas
ColoRectal - most common site 50% Rectum, 20% Sigmoid, 16% Cecum, 8% Transverse/Splenic Flexure, 6% Descending Colon
Ewing's Sarcoma - most common site Diaphysis of Long Bones, Lower half of the body
Bladder - Staging / Grading Systems Jewett-Marshall Zero & A-D, AJCC TNM
Prostate - Staging / Grading Systems Gleason, TNM, Am. Urological A-D
Cervical - Staging / Grading Systems FIGO, TNM
Hodgkins - Staging / Grading Systems Ann Arbor Staging, REAL, WHO
Procedure for Esophagus Ivor Lewis
Procedure for Pancreas Whipple
Most common Dose per day 180-200 cGy
Most common Palliative Dose 300 cGy x 10 days
Tenesmus Constant feeling the need to defacate
Proctitis Inflamed rectum
Cystitis Inflamed bladder
Telangiescasia small blood vessels breaking
Fistula or Perforation Opening in wall
Fissure Tear
How to calculate the time to deliver a specific dose... MU (Time) = Dose / All other factors, If using Cobalt, take the answer and multiple by 1/60 (___sec x 1min/60sec = ___min___sec)
How to calculate for Field Size and SSD changes... FS1 / SSD1 = FS2 / SSD2
What is SSD if SAD is 100 with a target depth of 12? 88, (100 SAD - 12 depth = 88 SSD)
Patient is treated using SAD method to 10x15cm field. At SAD of 100. What is the field size on skin surface if the target depth is 12 cm? 8.8 x 13.2 cm, (SAD - 12 = SAD), then (FS1 / SSD1 = FS2 / SSD2)
If dose is 200 cGy at 100 cm, what is the dose at 80 cm? 312.5 cGy, (I1 / I2 = (D2 / D1)2, *Don't forget to square the distance, *Only use Inverse Square Law when Dose & Distance are asked! (200cGy/x = (80/100)2 = 312.5 cGy)
What shielding of lead should be used in mm for 16 MeV? 8 mm of lead, (MeV / 2 = shielding of lead)
X, Y, Z Coordinates X = Lateral, Y = Longitudinal, Z = Vertical
80% isodose depth = 80% isodose depth = MeV / 3
90% isodose depth = 90% isodose depth = MeV / 4
If using 10 MeV, at 2 cm what is the MeV at that depth? 6 MeV, Electron beam loses energy at approximately 2 MeV / cm so 2x2=4, then 10 - 4 = 6 MeV
If 3 fields, AP, Rt Lat, & Lt Lat, treated with 300 cGy, what is each dose if AP=50%, RtLat=30%, LtLat=20%? *AP = 300 x 0.5 = 150 cGy, *Rt Lat = 300 x 0.3 = 90 cGy, *Lt Lat = 300 x 0.2 = 60 cGy
If AP and lateral field are treated with 2:1 weighting with dose of 200, what dose wi each field getting? dose / # of weighting = Dose per weightings, 200 / 3 = 66.7, then 66.7 x 2 = 133.67 for AP field and 66.7 for Lateral field
Field magnifications calculations... SFD / SAD or Larger # / Smaller # = how many times more magnified at the SAD
If cobalt was to deliver 150 cGy in 6.23 minutes and treatment was terminated after 3.06 minutes, what was the dose delivered? 73.6 cGy, 6.23 x 60sec/1min = 373.8sec, 3.06 x 60sec/1min = 183.6sec, then (150cGy / 373.8sec = X / 183.6sec)
If machine is to deliver 90 cGy in 112 MU and shuts down after 43 MU, how much dose was delivered? 35 cGy, *Proportion Formula, 90 / 112 = X / 43, X=cGy
Patient is being treated on a 6 MV at 100 cm SSD. Collimator setting is 15x15cm. No blocking or MLC. Prescription states 300 cGy/fraction is to be delivered at Dmax (given dose), what is the dose delivered at 5 cm? PDD=87.9 263.7 cGy, *%DD = TD/GD x 100, then (87.9 = X/300 x 100), X = 87.9x300 / 100 = 263.7
If tumor dose is 350 cGy and given dose is 425 cGy, what is the %DD? 82.4%, *%DD = TD (absorbed) / GD (prescribed/given/dmax) x 100 (*or simply change decimal to a percentage)
What is the formula for Given/Applied Dose? Applied Dose = TD / %DD (decimal form)
If %DD is 0.638 and tumor dose is 280 cGy, what is the given dose? 438.87 cGy, Given dose = TD / %DD, *If %DD is listed as 63.8%, simple change to decimal form prior to calculation.
If you hav an AP field and Lateral Wedge fields, what will be the hinge angle and what degree of wedge will be used? 90º hinge angle, 90 / 2 = 45º wedge used
100 rad = ? Gy 1 Gy
100 rem = ? Sv 1 Sv
What is the quality factor for alpha particles? 20
What is the quality factor for xray and gamma? 1
What is the dose equivalent for absorbed dose of 7.98 Gy of Alpha radiation? 159.6 Sv, DE(Sv) = AD(Gy) x QF, Quality Factor of Alpha is 20
If a radiographer receives 1.4795 Sv over a lifetime, what is their lifetime in rems? 147.95 rem, 1 Sv = 100 rem, (1.4795 x 100)
Convert 45.84 rem into mSv: 458.4, 1 Sv = 100 rem & 1 Sv = 1000 mSv, (45.84/100x1000)
Convert 377.943 Sv into mSv: 377,943, 1 Sv = 1000 mSv, (377.943x1000)
Convert 325 Gy into rads: 32,500 rads, 1 Gy = 100 rads, (325x100)
Convert 39.72 rads into Gy: 0.3972 Gy, 1 Gy = 100 rad, (0.3972 Gy)
Convert 30 Gy into cGy: 3000 cGy, 1 Gy = 100 cGy, (30x100)
What is the dose equivalent for absorbed dose of 2 rads of xray? 2 rem, DE(Sv/rem) = AD(Gy/rad) x QF, rads >rem, Gy>Sv
If an individual was exposed to 1 Gy of Xray, 1 Gy of Alpha, and 1 Gy of Gamma, what is the dose equivalent? 22 Sv, DE(Sv/rem) = AD(Gy/rad) x QF, rads>rem, Gy>Sv
Concert 27 R into C/kg: 0.006966 C/kg, 1 R = 2.58 x 10^-4 Coulombs/kg
5 Gy of test radiation and 20 Gy of 250 kVp xray to produce same reaction. What is the RBE? RBE = 4, (RBE=20 / 5 = Dose of 250 kVp/Dose of test radiation
5 Steps to Improve Setup Accuracy 1. Use comfortable, relaxed position for patient, 2. Use lasers during sim & tx, 3. Use surface markings as much sup, inf, and lat as possible, 4. Use external landmarks, 5. Make reproducible positioning and immobilization devices.
6 Objectives of Immobilization 1. Limit patient movement, 2. Reduce position errors, 3. Reduce setup time, 4. Provide pt reassurance so they feel secure/safe, 5. Reduce need for cooperation by allowing them to be relaxed, 6. Provide conversation w/rigid body position
Why is a High Therapeutic Index good? Comparison of the dose likely to provide cure to the dose that will cause harm. (Toxid Dose / Therapeutic dose), The Higher the index, the Better the chance of good outcome
2 Things that will Increase the Therapeutic Index 1. Reproducible Simulation, 2. Treatment Planning
Brachytherapy Means 'close or near', radiotherapy delivered at close proximity to the tumor site using a radioisotope (low or high dose)(emits radiation during its decay)
Cobalt Radioisotope that produces Gamma radiation of approximately 1.25 MeV
Depth Dose Percentage of the maximum dose delivered as a function of the depth within tissue, various beams and energies
EBRT Also called Teletherapy (from a distance), radiation delivered by linear accelerator, cobalt machine, and orthovoltage machines
Superficial Machine 50-125 keV, skin cancers, keloids
Orthovoltage Machine 125-500 keV, skin cancer
Megavoltage (Supervoltage) Machine Greater than 1 MeV
Monoclonal Antibiody Targeted therapy against specific cell or pathway, Antibody (type of protein) made from single clone of immune cells that can be used to produce specific targeted meds , used with radioisotope in radioimmunotherapy
Gamma Knife Cobalt sources used for SRS (Stereotactic Radiosurgery)
CyberKnife Robotic Linear Accelerator for SRS (Stereotactic Radiosurgery) & SBRT (Stereotactic Body Radiotherapy)
What product must be in a lead radiation therapy room door? What is this product shielding? Borated Polyethylene, Required because lead does NOT stop Neutrons (produced with energy over 10 MeV)
EPID Electronic Portal Imaging Device - Used for imaging the tx fields and comparing to DRR (Digitally Reconstructed Radiographs) from simulation
What is MLC made of? Multi-Leaf Collimator is made out of Tungsten leaves
What is Alpha Cradles made of? Polyurethane foam cast
Abscopal Effect Effects outside of treatment field, Can be positive (regress disease outside treated area) or negative (pneumonitis), most likely result of activating immune response
Alpha/Beta Ratio Attempts to quantify the dose response of early and late responding tissues, Shows where radiation damage is equal. Generally, 10 Gy for Early and 2 Gy for Late responding tissue.
Accelerated Hyperfractionation used for... Rapidly growing or Poor responsive tumors, Often for retreatment of areas
Xerostomia Dry Mouth
Pterygia Abnormal growth of tissue on cornea
Radiation therapy used to prevent what benign or non cancerous... Pterygia, Keloids, Heterotopic Bone Formation, Acoustic neuromas, hemangiomas, Fibromatoses, Meningiomas, Exophthalmos (Graves disease), Gynomastia, Trigeminal Neuralgia
PBI and PCI Partial Breast Irradiation or Prophylactic Cranial (Brain) Irradiation (often when small cell lung cancer)
Skin sparing Maximum radiation absorbed dose occurs Below the surface of skin, ALL MeV RT due to Compton Absorption, Penetration of beam increases as energy increases
1 of the 4 R's of Radiobiology that ONLY affects NORMAL cells Repair
1 of the 4 R's of Radiobiology that ONLY affects TUMOR cells Reoxygenation
2 of the 4 R's of Radiobiology that can affect Normal OR Tumor Cells Redistribution (reassortment) & Repopulation
Created by: mkzimmy