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93 Cards in this Set
- Front
- Back
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what % of cancer patients are treated with RT
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60%
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what is the goal of RT
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to deliver a precisely measured dose of irradiation to a defined tumor volume with minimal damage to surrounding healthy tissue, resulting in eradication of the tumor, high quality of life, and prolongation of survival
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what are the 2 ways ionizing radiation works
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direct and indirect
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what is the direct effect of ionizing radiation
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it strikes the tissue and causes direct damage to DNA
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what are the 3 charged particles of direct ionizing radiation
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alpha
protons electrons |
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what is the indirect effect of ionizing radiation
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ionizing particles penetrate the cells nucleus and interact with the water content to form oxygen radicals
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what % of cells is water
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80%
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why don't we want patients taking antioxidants when treated with RT
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it effects free radicals b/c that's whats doing the damage to the tissue
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what are the 2 kinds of ionizing radiation
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electromagnetic
particulate |
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what is electromagnetic radiation made of
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x rays and gamma rays
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where are x rays produced
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outside the nucleus in electron shell
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where are gamma rays produced
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emitted from the nucleus of a radioisotope
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what is particulate radiation
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any particle in motion and possessing kinetic energy (ionizing)
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what are examples of particulate radiation
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alpha
beta neurons protons mesons heavy ions |
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what does LET stand for
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linear energy transfer
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what is LET
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the rate at which energy is deposited by charged particles as they travel through matter
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what is low LET
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smaller particles that deposit energy over a great distance of tissue
sparsely ionizing |
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what are examples of low LET
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x rays and gamma rays
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what is high LET
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bulkier particles that deposit energy over smaller distances in the cell
densely ionizing |
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LET is directly proportional to what? and inversely proportional to?
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proportional to the square of the charge and inversely proportional to velocity
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what are the 4 types of equipment
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grenz ray
superficial orthovoltage megavoltage |
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what is the energy of the grenz ray
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10-15kVp
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where was the grenz ray absorbed
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first mm of skin
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what was the normal treatment for a grenz ray
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200 Roentgens once a week for 4 weeks
(can't treat everyday b/c such a high dose would cause horrible skin reactions) |
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what did grenz ray mostly treat
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inflammatory disorders, bowen's disease, micosisfungoides, herpes simplex
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what is the energy for superficial units
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50-150kVp
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what are superficial units filtered by?
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aluminum
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what does aluminum do in superficial units
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hardens the beam
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what is hardening of the beam in superficial units measured in
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HVLs
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what is SSD of superficial units
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15-20cm
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we won't treat anything deeper than ____cm on superficial machines
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0.5
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what is the energy of orthovoltage
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150-500kVp
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what is the HVL of orthovoltage
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1-4mm of copper
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what is the SSD of orthovoltage
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50cm
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orthovoltage is used to treat tumors less than
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3 cm deep
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what kinds of cancers do we use with orthovoltage
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skin
mouth cervical |
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what is the energy of megavoltage
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> 1 MeV
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what was the first megavoltage
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cobalt
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what are the 4 other megavoltage machines
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vandigraph
betatron linear accelerators cyclotrons (protons) |
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what is D max
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depth of maximum build up in which 100% of the dose is deposited
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what is d max of cobalt?
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0.5cm
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what is d max of 6MV
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1.5cm
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what is d max of 15MV
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3cm
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is cobalt SSD or SAD and why
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SAD b/c we're now in the body
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what is the SAD of cobalt
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80-100cm
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what is the disadvantage of cobalt
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has to be replaced every 4-5 years b/c its an actual source
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how does linear accelerator work
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charged particle travels in a straight line as they gain energy from alternating electromagnetic field
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what is SAD of linear accelerator
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100cm
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what are some benefits of linear accelerator
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higher energy
greater skin sparing sharply defined field edges technology |
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what is intraoperative RT
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single high dose treatment to the organ of interest
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when is intraoperative RT performed
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during surgical procedure
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what is intraoperative RT used for
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colorectal
bladder pancreas cervix |
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what is the cone called thats used in intraoperative RT
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lucite
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cyclotrons is used to treat patients with
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neutrons
protons pions pi mesons alpha particles |
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what is the bragg peak
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when charged particles pass through tissue and deposit most of their energy at the end of their path
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depth at which bragg peak occurs depends on what 3 things
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energy
mass charge of particle |
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when is neutron beam therapy used. 6 things
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for large slow growing tumors
unresectable salivary gland non responsive prostate soft tissue sarcomas NSCLC SCCA of H&N |
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what are the benefits of neutron beam therapy
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less influences by hypoxia and DNA repair process like protons
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what are protons and alpha particles
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positively charged nuclear particles that deliver their radiation dose at a defined tissue depth to small non infiltrating tumors situated in highly radiation sensitive tissues
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how many proton centers are there in the world
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20
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how are alpha particles made
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by radionuclides that emit alpha particles. extremely toxic to cells
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what are the 4 characteristics given about proton therapy
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same properties as x rays
dose distribution is key sparse path high LET possible to confine dose to tumor volume |
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what are some tumors that protons are good for
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uveal melanoma
base of skull paranasal nasopharyngeal spinal cord prostate pediatric |
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what are pions and pi mesons used with
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cyclotrons
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what does brachytherapy do
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delivers large amounts of radiation to a specific site over a short period of time
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what is HDR
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high dose radiation
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what is a common HDR site
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mammosites twice a day
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what is a common LDR site
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cervical
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what are the two forms of brachytherapy
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interstitial
intracavitary |
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what is half life
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time it takes for activity to decay to half its original value
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what was first source to be used in brachy
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radium 226
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what is radium 226 half life
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1622 years
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what brachy source is used for cervical, uterine, and vag cancers
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cesium 127
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what is cesium 127 half life
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30 years
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what source is common for mammosites and interbronchial lesions
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iridium 192
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what source is used for prostate and pulmonary bronchi
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gold 198
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what source is mainly used for prostate
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iodide 125
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brachy materials are chosen on basis of what 2 things
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half life
photon energy |
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as the brachy sources decay they emit
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photons
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encapsulated or sealed brachy sources include what 7 things
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ribbons
wires seeds capsules needles tubes molds |
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in brachy is encapsulated or non encapsulated most common
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encapsulated
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what 3 ways are unsealed brachy sources administered
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orally
iv intracavitary |
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what is trigium
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extra tissue on eye. what leslie might have. ha. not cancerous
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what is interstitial therapy
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involves placement of radioactive sources directly into a tumor or tumor bed
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what is the most common interstitial therapy
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prostate seed implants
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what is tandum and ovoids
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long straight applicator that fits into cervix and goes to endometrium
ovoids go to vagina |
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what is intracavitary therapy
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involves placement of sources into a body cavity adjacent to a tumor
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what are some side effects of brachy
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skin
nausea vomiting diarrhea alopecia esophagitis cough anorexia bone marrow suppression |
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what is a big side effect of brachy
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vaginal stenosis
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what 4 thigs does radiosensitivity depend on
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phase of cell life
division rate of cell degree of differentiation oxygenation |
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clinical response to RT is determined by
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rate of tissue turnover
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radiation dose is determined by what 3 things
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radiosensitivity of tumor
normal tissue tolerance volume of tissue to be irradiated |
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what is subclinical damage
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damage you cannot see. no symptoms
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