prelims Flashcards
- referred to as Radiation Oncology, began approximately a year after x rays were discovered in 1895.
- medical specialty that involves the treatment of malignant and benign tumors by the application of ionizing radiation
radiation therapy
aim of Radiation Therapy
deliver a precisely measured dose of radiation to a defined tumor volume with minimal damage to surrounding healthy tissues. This results in the eradication of tumor, high quality of life and prolongation of life.
virulent or malignant cell growth, manifest itself as a localized tumor of disseminated throughout the body.
cancer
4 SPECIFIC MODES OF TREATMENT
- Surgery
- Radiation Therapy
- Cytotoxic Drugs
- Hormone Therapy
CLASSIFICATIONS OF TREATMENT
- radical
- palliative
attempt, heroic, if necessary, to remove all malignancy present.
radical (multiple beam radiation)
thought to be impossible, the aim is to relieve symptoms
palliative (simple)
AMOUNT OF DOSE GIVEN IS DEPENDENT ON
- Size of Tumor
- Extent of Tumor
- Type of tumor
The radiation is delivered once a day in fraction
The total fraction is __
30
Average treatment
usually 25 times
Radiation absorbed Dose unit
Gray (Gy)
RADIATION THERAPY STAFF
- Radiation Oncologist
- Medical Physicist
- Medical Dosimetrist
- Radiologic Technologist (Radiation Therapy Technologist, Radiation Therapist)
- Physician skilled in the act of applying radiation in the treatment of benign and malignant tumors.
- Prescribes the amount of Radiation dose to kill the tumor
RADIATION ONCOLOGIST
- is responsible for calibration and maintenance of the radiation-producing equipment.
- also advises the physician about dosage calculation and complex treatment technique.
MEDICAL PHYSICIST
- person responsible for the calculation of the proper radiation treatment dose who assist the radiation oncologist in designing the individual treatment plans.
- Devises a plan for delivering the treatments in a manner to best meet the physician’s goals of irradiating the tumor while protecting vital normal structures.
MEDICAL DOSIMETRIST
- person trained to assist and take directions from radiation oncologist in the use of ionizing radiation for the treatment of disease.
- responsible for obtaining radiograph that localize the area to be treated, administering the treatment, keeping the accurate record of the dose delivered each day and monitors the patient’s physical and emotional being.
RADIATION THERAPIST
TWO BROAD CLASSES OF NEOPLASMS OR TUMORS
- BENIGN/SIMPLE
- MALIGNANT/CANCEROUS
universal since they include the common birthmarks. They are harmless and their growth is strictly localized and/or never widespread.
benign or simple
cancers; treatment must aim destruction of every cancer cell or the abolition of their capacity to reproduce. They have the power of “invasion”.
malignant/cancerous
carcinogens
- chronic irritation
- radiation
- infection
- hormones
- worms
- viruses
metastases
- Local invasions
- By lymphatic vessels
- By blood vessels
- Across cavities
- geographical estimation of the extent to which any tumor has spread
- determines the spread of cancer
staging of cancer
tumor confined to organ of origin
stage 1
local lymph nodes invaded
stage 2
distant nodes invaded or local spread beyond organ or origin
stage 3
blood borne metastases present
stage 4
– local extension of primary Tumor
T
– condition of regional lymph Nodes
N
– presence of Metastases beyond regional lymph nodes
M
– indicates inflammation
itis
– used to indicate a neoplasms or swelling of any nature
“oma”
- there is a probability of long term survival after adequate therapy, some side effect of therapy although undesirable, may be acceptable.
curative
- there is no hope of total eradication of the tumor, done to relieve suffering and to prolong life
palliative
- treatment of some parts of the body that is suspected of harboring tumor cell but without any symptoms.
prophylactic
WAYS OF CANCER TREATMENT
- surgery
- chemotherapy
- radiation therapy
- involves the removal of the tumor plus some surrounding tissues
surgery
uses drugs taken by mouth or injected into the patient’s vein. These drugs travel throughout the body working to destroy cancer cells.
chemotherapy
- uses photons, electron and other sources of radiation to destroy cancer cells
radiation therapy
METHODS OF RADIATION THERAPY
- Teletherapy Method or External Beam Radiation Therapy
- Brachytherapy or Plesiotherapy
radiotherapy technique in which the source of radiation is at some distance from the patient
Teletherapy Method or External Beam Radiation Therapy
- placement of radioactive substance or nuclides in or on neoplasm to deliver cancercidal dose
Brachytherapy or Plesiotherapy
TREATMENT PLANNING
- GTV
- CTV
- PTV
all known disease, including abnormally enlarged lymph nodes.
Gross Tumor Volume (GTV)
encompasses TV plus regions considered to harbor potential microscopic diseases.
Clinical Target Volume (CTV)
provides margins around TV to allow for internal target motion, other anatomic motion during treatment.
Planning Target Volume (PTV)
radiation therapy technique for which the source of radiation is at some distance from the patient
TELETHERAPY OR EXTERNAL BEAM RADIATION THERAPY
Classification of EBRT Machines
Grenz Ray Therapy
Contact Therapy or Endocavitary
Superficial Therapy Units
Orthovoltage Therapy or Deep Therapy Unit
Supervoltage Therapy Unit
Megavoltage Therapy Unit
Describes treatment with beams of very soft (low-energy) x-rays produced at potentials below 20kV.
Because of the very low depth of penetration, such radiations are no longer used in radiotherapy
Grenz Ray Therapy
• operates at potentials of 40 to 50 kV and facilitates irradiation of accessible lesions at very short source (focal spot) to the surface of the skin (SSD of 2cms.) It operates with a tube current of 2 mA.
• To absorb low energy x-rays a 0.5 - 1.0 mm aluminum filter is utilized. This quality of radiation is useful for tumors not deeper than 1 to 2 mm and the beam is almost completely absorbed with 2 cm of sof tissue.
Contact Therapy or Endocavitary
- applies to treatment with x-rays produced at potential ranging from 50 to 150 kV. The maximum absorbed dose or energy deposited in a mass of tissue occupying a small volume is produced on the surface with rapid fall off of dose with increasing depth. This equipment produces a large amount of soft (low energy) x-rays which can produce severe skin reaction thus. it is useful for irradiating tumors to about 5mm depth.
• source to skin distance (SSD) typically ranges from 15 to 20 cm. The machine is usually operated at the tube current of 5 to 8 mA.
superficial therapy units
• used to describe treatment with x-rays produced at potentials ranging from 150-500 kV. Reasonable tissue penetration of the resultant x-ray beam is achieved with this equipment, which also must be operated with filters to reduce the soft x-rays.
• maximum dose is achieved on the skin as with the superficial units; however, the additional penetrating power of these “hard” x-rays allows treatment of lesions located within a few centimeters of the surface without delivering excessive dose to the skin. The SSD is usually set at 50 cm.
Orthovoltage Therapy or Deep Therapy Unit
•X-ray therapy in the range of 500 to 1,000 kV has been designated as high-voltage therapy or supervoltage therapy. In the quest for higher energy x-ray beam, considerable progress was made after World War II toward developing the high voltage machines. Since the electron attain high energies before striking the target, a transmission type target may be used to obtain the x-ray beam on the other side of the target.
Supervoltage Therapy Unit
•X-ray beams of energy 1 MV or greater can be classified as megavoltage beams. Although the term strictly applies to x-ray beams, the gamma ray beams produced by radionuclides are also commonly included in the category if their energy is 1 MeV or greater
Megavoltage Therapy Unit
electrostatic accelerator designed to accelerate charged particles. The unit accelerates electrons to produced high energy x-rays typically at 2MV
Van de Graaf Generator
- based on the principles that an electron in a changing magnetic field experiences acceleration in a circular orbit. The accelerating tube is shaped like a hollow doughnut and is placed between the poles of an alternating current magnet. A pulse of electrons is introduced into this evacuated doughnut by an injector at an instant that the alternating current cycle begins.
- were first used for radiotherapy in the early 1950s.
betatron
device that uses high frequency electromagnetic waves to Accelerate charged particles such as electrons to high energies through a linear tube. The high-energy electron beam itself can be used for treating superficial tumors, or it can strike a target to produce X-rays for treating deep- seated tumors. Developed by Wilderoe in 1928 which accelerate heavy ions. Electron accelerators was first developed during the late 1940s by Fry, Ginzton, and Chodorow.
Linear Accelerator
Radiation Therapy and surgery are used for the control of systemic tumors while chemotherapy is reserved for localized tumors (T or F)
- F. it is the reverse
Describes treatment with beams of very soft (low-energy) x-rays produced at potentials below 20kV. Because of the very low depth of penetration, such radiations are no longer used in radiotherapy
grenz ray therapy
other term for contact therapy
endocavitary
energy of contact therapy
40-50kV
treatment with x-rays produced at potential ranging from 50 to 150 kV
superficial therapy unit
Contact Therapy is useful for tumors not deeper than___
1-2mm
distance of contact therapy
SSD 2cm
Superficial Therapy units uses an SSD of
15-20 cm
Other term for orthovoltage therapy
deep therapy unit
Tube current of Superficial Therapy units
5-8 mA
Tube current of Contact Therapy
2 mA
This equipment produces a large amount of soft (low energy) x-rays which can produce severe skin reaction thus. it is useful for irradiating tumors to about 5mm depth.
superficial therapy units
used to describe treatment with x-rays produced at potentials ranging from 150-500 kV.
orthovoltage therapy
Aluminum filter used by Contact Therapy
0.5 - 1.0 mm
X-ray therapy in the range of 500 to 1,000 kV has been designated as
Supervoltage therapy unit
X-ray beams of energy 1 MV or greater can be classified as megavoltage beams. Although the term strictly applies to xray beams, the gamma ray beams produced by radionuclides are also commonly included in the category if their energy is 1 MeV or greater
Megavoltage Therapy Unit
Beam of Contact Therapy is completely absorbed within___cm of soft tissue
2cm
based on the principles that an electron in a changing magnetic field experiences acceleration in a circular orbit
betatron
is a device that uses high frequency electromagnetic waves to Accelerate charged particles such as electrons to high energies through a linear tube
linear accelerator
An electrostatic accelerator designed to accelerate charged particles. The unit accelerates electrons to produced high energy x-rays typically at 2MV
van de graaf
In LINAC, the high-energy electron beam itself can be used for treating superficial tumors, or it can strike a target to produce X-rays for treating deep- seated tumors. Developed by ____which accelerate heavy ions.
Wilderoe 1928
Type of decay that Co-60 undergoes
beta minus decay
The accelerating tube is shaped like a hollow doughnut and is placed between the poles of an alternating current magnet
betatron
In cobalt-60, the beta decay energy is ____, and the Gamma rays are produced at 1, 173,210 and 1,332,470 eV energies with nearly 100% frequency of occurrence
2.824 Me
Electron accelerators was first developed during the late 1940s by ____
Fry, Ginzton, and Chodorow.
Half-life of Cobalt-60
5.27 years
pulse of electrons is introduced into this evacuated doughnut by an injector at an instant that the alternating current cycle begins. Betatrons were first used for radiotherapy in the early ___
1950s
ave energy of Co-60
1.25MV gamma ray
Source housing of Co-60 is called____. It consists of a steel shell filled with lead for shielding purposes and a device for bringing the source in front of an opening in the head from which the useful beam emerges
sourcehead
