Overview Of Radiation Therapy Flashcards
High level radiation is in
Megavoltage
It destroys the cell ability to divide or multiply
Law of bergonie and tribondeau
Damage to healthy cells are the reason for
Side effects of radiotherapy
Goal of Radiotherapy
Curative
Palliative
Curative
Cure from cancer
Palliative
Relieve symptoms
Curative is also called
Radical radiotherapy
Considered emergency cases in radiotherapy
Bone metastasis with spinal cord compression
Cases with profuse bleeding
Mass obstructing the lungs
Brain matastasis
Aim of radiotherapy
Deliver a PRECISE measured dose of radiation to a DEFINED tumor volume
Members of radiotherapy team
Radiation Oncologist
Medical Phycist/Dosimetrist
Radiotherapy Technologist
Sample of immobilization devices
Alpha Cradle
Thermoplastic mask
Two forms of radiotherapy
External Beam (Teletherapy) Internal Beam (Brachytherapy)
Given to a careful defined area through a machine that directs the high energy rays from outside the body at the cancer and the normal tissues
External Radiation Therapy
Places the source of the inside the body, as close as possible to the cancer cells
Internal Radiation Theraphy
The radioactive substances used typically include
Radium
Cesium
Iodine
Phosphorus
2 types of external beam radiation
Photon beam
Proton beam
The dose prescribed by the Radiation Oncologist to be received by the patient that must be absorbed at the tumor site from the radiation beam
Dose of Radiation
Unit of absorbed dose
Gray (Gy)
Made under simulated condition will assure the delivery of the exact prescribed dose
Detailed measurement
Dose of Radiation determination
Size tumor
Extent tumor
Grade of tumor
Response to radiation
Largest amount of dose that can be accepted without the production of injurious symptoms
Tolerance Dose
Factors affecting tolerance dose
Dose per fraction/dose rate
Volume irradiated
Sensitivity of the tissues
Amount of recovery which can take place between fractions
The dose that can be tolerated by normal tissue in the treatment zone varies with the total time over which the dose is given
Dose per fraction/dose rate
Dose that could be given in a longer period of time is ____ than given over a short period
Larger
Alter the biological effect
Size of each fraction dose
Time interval between the fractions
The higher the fraction dose
The greater the late damage potential
The smaller the volume to be treated
The higher total dose which may be tolerated
The type of tissue treated, poor dietary of fluid intake or concomitant drug treatment, may affect the level of dose tolerated
Patient and Biological Factors
Good oxygenation increases the chance of radiation damage to cells
Oxygen effect
Large cell mass where there is no organized blood supply
Hypoxic
If the number of cells doubles within the time interval between two fractions, treatment may fail
Cell Doubling Time
The administration of a course of radiation treatment in a planned series of fractions of total dose
Fractionation
Fractionation is needed to
Allow recovery of normal cells while depleting the number of surviving tumor cells
Some patients (head and neck) are at survival disadvantage
If treatment duration is lengthened
Fractionation Regimes
Conventional fractionated courses
Less than 5 fractions per week
Reason for lowered fractionation regimes
Consist of once-daily doses given 5 days per week, recovery period at weekend
Conventional fractionated courses
Once, twice, or three times weekly treatments with higher dose of radiation
Less than 5 fractions per week
Fewer visits and less traveling time for patients
Shortage of treatment machine
Clinical indications
Reason for lowered fractionation regimes
Shortening the treatment course duration but giving a high number of small fractions
Hyperfractionation
Given to rumors with a fast cell-doubling time such as 5 days
Hyperfractionation
Three distinct region for target volume
Gross tumor volume
Clinical target volume
Planning target volume
Denotes the demonstrable tumor
Gross tumor volume
Denotes the GTV and subclinical disease
Clinical target volume
Denotes the CTV and includes margins for geometric/position uncertainties
Planning Target Volume
Volume of tissue enclosed by an isodose surface
Treated volume
Is always larger than the PTV and usually has a simpler shape
Treated volume
Volume of tissue that receives a dose considered significant in relation to tissue tolerance
Irradiated volume
Necessary to make the marks permanent for the basis of body alignment
Tattoo Process
Factors to consider for side effects
Total dose delivered
Time over which the dose was delivered
Volume irradiated
Side effects are generally limited to the
Region of the body being treated
A skin condition that is a common side effect of radiation Theraphy
Radiation Dermatitis
Radiation can affect the membranes of the mouth and GI Tract causing discomfort
Nutritional problems
Most common side effects of radiation therapy
Fatigue
The use of high level radiation to destroy cancer cells
Radiation Therapy
