Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
20 Cards in this Set
- Front
- Back
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Grenz-ray"
|
Energy: 20 kV
Filtration: N/A TX capabilities: No longer used in radiation therapy |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Contact Therapy"
|
Energy: 40 to 50 kV
Filtration: 0.5-1.0 thick aluminum TX capabilities: Is useful for tumors not deeper than 1 to 2 mm SSD: 2.0 cm or less |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Superficial Therapy"
|
Energy: 50 to 150 kV
Filtration: 1 to 6 mm aluminum TX capabilities: Useful for irradiating tumors confined to about 5 mm depth (90% depth dose). SSD: 15 to 20 cm |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Orthovoltage Therapy"
|
Energy: 150 to 500 kV
Filtration: 1 to 4 mm Cu TX capabilities: SSD: 50 cm |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Supervoltage Therapy"
|
Energy: 500 to 1,000 kV
Filtration: TX capabilities: SSD: |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Megavoltage Therapy"
|
Energy: 1 MV or greater
Examples of clinical Megavoltage machines are accelerators such as Van de Graaff generator, linear accelerator, betatron and microtron, and teletherapy y ray units such as cobalt-60. |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Van De Graff generator"
|
Energy: 2 to 10 MV
TX capabilities: No longer used. |
|
List the capable energies, filtration, tx capabilities, and any other pertinent information for: "Linear Accelerator"
|
Energy: 4MV to 20MV
Filtration: Flattening Filter made of lead, tungsten, uranium, steel, aluminum, or combination. TX capabilities: SSD: 100 cm |
|
List the steps that occur for treating a patient with a linear accelerator in high energy photon mode. Make sure to state what each part along the beam path does. Start with incoming power.
|
-Modulator is a section of electronics where direct current (DC) voltage is converted into high-voltage flat-topped DC pulses of a few microseconds in duration. It contains the pulse-forming network and a high-voltage switch tube known as hydrogen thyratron.
-High-voltage pulses from the modulator are delivered to the magnetron or klystron and simultaneously to the electron gun. -Microwave pulses from the magnetron or klystron are injected into the accelerator structurethrough a waveguide system. At the proper instant, electrons from an electron gun are also in-jected into the accelerator structure. -In the higher-energy linacs, the accelerator structure is too long and, therefore, placed horizon-tally or at an upward angle with respect to the horizontal. The electrons are then bent througha suitable angle (usually about 90º–270º). -Transmission type tungsten target intercepts the electron beam to generate x-ray beam(bremsstrahlung). -Since the kinetic energy of electrons striking the target is in the megavoltage range, the x-raybeam intensity is peaked in the forward direction. To make the intensity uniform in cross sec-tion, a flattening filter is inserted in the beam. |
|
List the steps that occur for treating a patient with a linear accelerator in electron mode. Make sure to state what each part along the beam path does. Start with incoming power.
|
--Modulator is a section of electronics where direct current (DC) voltage is converted into high-voltage flat-topped DC pulses of a few microseconds in duration. It contains the pulse-forming network and a high-voltage switch tube known as hydrogen thyratron.
-High-voltage pulses from the modulator are delivered to the magnetron or klystron and simultaneously to the electron gun. -Microwave pulses from the magnetron or klystron are injected into the accelerator structurethrough a waveguide system. At the proper instant, electrons from an electron gun are also in-jected into the accelerator structure. -In the higher-energy linacs, the accelerator structure is too long and, therefore, placed horizon-tally or at an upward angle with respect to the horizontal. The electrons are then bent througha suitable angle (usually about 90º–270º). -In the electron mode of accelerator operation, both the target and the flattening filter moveout of the way and a scattering foil is inserted to intercept the electron beam. |
|
List the characteristics of a cobalt treatment device.
|
-A typical cobalt teletherapy source consists of 60 Co disks encapsulated in a steel cylinder of diameter ranging from 1 to 2 cm. It is housed in a well-shielded shell, called the sourcehead.
-A typical cobalt teletherapy source consists of 60 Co disks encapsulated in a steel cylinder of diameter ranging from 1 to 2 cm. It is housed in a well-shielded shell, called the sourcehead. -Because of the relatively large source size (1–2 cm diameter), a 60 Co beam is associated with amuch larger geometric penumbra than a linac x-ray beam that has a focal spot size of approxi-mately 2 to 3 mm. |
|
List the formula for geometric pneumbra.
|
Pd= s(SSD + d - SDD) / SDD
s=source diameter, SDD=source to diaphragm distance, d=depth |
|
Calc the geometric penumbra for a 1.5 cm source, 100 cm SSD, depth 4 cm and 38 cm SDD
|
2.60 cm
|
|
State how the factors of the geometric penumbra affect the penumbra size if you increase one and the others remain constant. i.e. if source size and all other factors fixed.
|
Penumbra width increases with increase in source diameter, SSD, and depth
Penumbra decreases with an increase in SDD |
|
List the characteristics of a betatron.
|
Based on the principle that an electron in a changing magnetic field experiences acceleration in a circular orbit.
Energy ranges from 6 to more than 40 MeV Low dose rate and small field size |
|
List the characteristics of a microtron.
|
A magnetic field forces the electrons to move in a circular orbit and return to the cavity.
|
|
Define what Bragg Peak is and describe it. What does it occur for?
|
The dose deposited is approximately constant with depth until near the end of the range where the dose peaks
out to a high value followed by a rapid falloff to zero. The region of high dose at the end of the particle range is called the Bragg peak. Protons and Heavy Ions |
|
What are the characteristic of protons and what are they used for?
|
Proton beams for therapeutic application range in energy from 150 to 250 MeV.
Produced by a cyclotron or a linear accelerator. Used for brain, head and neck, prostate. |
|
What are the characteristics of heavy ions and what are they used for?
|
Exhibit a sharp drop-off in dose (Bragg Peak)
|
|
What are the characteristics of a negative pion?
|
Pions of energy close to 100 MeV are of interest in radiation therapy, providing a range in water of about 24 cm.
The Bragg peak exhibited by pions is more pronounced than other heavy particles because of the additional effect of nuclear disintegration by π- capture. Low dose rates, beam contamination, and high cost. |