Radiation Therapy Flashcards
three princpal modalities used in the treatment of cancer
radiation theraphy
surgery
chemotherapy
most often delivered daily
monday - friday
2-8 weeks
dosages range from
2000 cGy and 8000 cGy
prescribes the quantity of radiation and determines anatomic region to be treated
radiation oncologist
responsible for calibration and maintenance of radiation-producing equipment and gives advice on dosage calculations
medical physicist
devises a plan for delivering treatments to irradiate tumor while protecting normal tissue
medical dosimetrist
obtaining radiogphs or CT scans
administering treatments
keeping accurate recods of dose delivered
monitoring the patents physical and emotional well being
radiation therapist
responsible for patient education on radiation side effects and side effect management
oncology nurse
biological effects of ionizing radiation observed
epilation
erythema
dr. emile grubb irradiated a women with carcinoma of the left breast
Jan 29 1896
dr. clarence skinner performed the first reported curative treatment using ionizing radiation on a woman with malignant fibrosarcoma
Jan 1902
the woman dr. skinner treated was declared free of her malignant fibrosarcoma
Apr 1909
two major categories for application of radiation for cancer treatment
external-beam
brachytherapy
also called teletherapy
the patient lies underneath a machine that emits radiation of generates a beam of xrays
external-beam
radioactive material is placed within the patient
brachytherapy
radioactive source is placed in close proximity to a lesion
mould technique
placement of radioactive source in the body cavity
intracavitary implant technique
radioactive source is placed directly into the tumor site and adjacent tissue
interstitial implant technique
for treatment of superficial lesions
low-energy beam deposits all or most of its energy on or near the surface
120-kVp superficial xray unit
for treatment of moderatly superficial lesions
250 kVp orthovoltage unit
average energy is 1.25 MeV
replaced orthovoltage units
first skin-sparing machine
known as the “work horse” reliablity and simplicity
cobalt-60 gamma ray source
is most suitable for tumors deep beneath the body
high energy
machine rotates around a fixed point and maintains the same distance from source of radiation
isocentric machine
source for high energy electrons
developed in 1952 first used in the us in 1956
6-35 MV linear accelerator or betartron
is produced by accelerating a stream of electrons twoard a target
photon beam
is most suitable for tumors deep within the body
megavoltage high-energy beam
steps in radiation therapy
simulation
dosimetry
treatment
done with a fluroscopy or CT simulator to determine the volume of tissue to be encompasssed within the radiation field
simulation
referes to the measurement of radiation dose and its distribution throuhout the patients body
dosimetry
devises a treatment plan that delivers a homogenous dose to the tumor while not exceeding the tolerance dose of a specific organ
monitors the dosage that critical anatomy is receiving and keeps the dose within established guidelines
dosimetrist
is an outline of the external surface of the patients body at the level of the central axis (center of treatment field)
contour
ensuring optimum treatment requires
precision posistioning of the machine, proper selection of the treatment field and MLC, accurate placement of cerrobend blocks of wedges, implementation of any changes in the patients treatment plae
treatment
produce a digital image that is displayed on a computer screen adjacent to the linac computer console
Electronic Portal Imaging Devices (EPIDs)
treatment varies by type and stage of disease
therapy used in conjunction with surgery and chemo
5000-6000 cGy of 10 MeV
lung cancer
radiation therapy is standard treatment
surgical removal of the prostate gland is another common approach
four fields are used AP PA laterals using 10MV and 7000 cGy
brachytherapy can also be used (early-stage)
prostate cancer
small lesion in the mouth can be treated with 6000 cGy for 4 weeks with orthovoltage beam
head and neck cancers
early diagnosed cancers can be treated with either radiation or surgery
cervical cancer
patient age and extent of disease determines treatment and prognosis
hodgkins disease
uses two tangetical fields to the chest wall of intact breast
breast cancer
cancer of the larynx is best treated with
megavoltage radiation
turmors confined to the true vocal cords with normal cord mobility have a 90% 5 year cure rate; in addition the voice remains useful
laryngeal cancer
carcinomas of the skin are usually squamous cell or basal cell lesions that may be treated with superficial radiation or surgery
cure rates tend to run between 80% and 90% and basal cell lesions less than 1 cm in diameter have a cure rate of almost 100%
skin cancer
the tumor is radiosensitive and patients who have had treatment of the entire cerbrospinal axis have a 5 year cure rate of greater than 60%
medulloblastoma
