X-ray Therapy: Tube Potential and Current

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Who is credited with the invention of the cobalt-60 teletherapy machine?

Harald E. Johns (correct)

Albert Einstein

Enrico Fermi

Marie Curie

What is the reason for replacing the source in a cobalt-60 machine every five years?

To reduce the machine's weight

To change the type of radiation produced

To improve the machine's efficiency

Due to the decay of the source by approximately 1% per month (correct)

Why are cobalt-60 machines still used in developing countries?

They are more expensive than modern machines

They have a simpler design and lower cost (correct)

They produce higher energy radiation

They require advanced technical support

What is the purpose of the gantry in a modern cobalt therapy machine?

To rotate the source about a horizontal axis Signup and view all the answers

What is the process by which cobalt-60 is produced?

Irradiation of neutrons of the common stable form of 59Co Signup and view all the answers

What is the primary reason for exact and reproducible selection of tube potential and current in therapeutic use of X-rays?

To achieve more precise therapy than diagnostic purposes Signup and view all the answers

What is the significance of the source-axis distance (SAD) in a cobalt-60 machine?

It is either 80 cm or 100 cm Signup and view all the answers

What is the ideal type of selection for tube potential, current, and filter on a therapy machine console?

Press-the-button type Signup and view all the answers

What is the purpose of the switches on the console of the therapy machine?

To select the needed filter Signup and view all the answers

What type of movement is allowed by the design of the tube stand?

Both translational and rotational movement Signup and view all the answers

What is the purpose of the electrical or mechanical brakes on the tube stand?

To fix the position of the beam during treatment Signup and view all the answers

What is the purpose of the scales on the tube stand?

To record the treatment setup position or changes Signup and view all the answers

What is the primary purpose of the steel shell with lead in the source head?

For shielding purposes Signup and view all the answers

What happens when the source is in the BEAM-OFF position?

A light source appears in the BEAM-ON position Signup and view all the answers

What is the purpose of the source indicator rod?

To indicate when the beam is ON Signup and view all the answers

What should be done first in case of an accidental source stuck?

Turn the gantry to the opposite direction Signup and view all the answers

What is the purpose of the T-rod?

To push the source to the OFF position Signup and view all the answers

What is the safety feature incorporated in both methods of moving the tele-therapy source?

Automatic termination of the beam in case of power failure Signup and view all the answers

What was the primary advantage of the rotating gantry-mounted machines in gamma-ray teletherapy?

They allowed for isocentric treatment of the patient with multiple beams. Signup and view all the answers

What was the consequence of the massive shielding for the radioactive source on the gantry assembly?

It presented a considerably heavy load for the gantry assembly to accommodate. Signup and view all the answers

What was the advantage of the pitch and roll movements available on some machines?

They allowed for treatment of poorly non-ambulant patients in an upright position. Signup and view all the answers

How did the compact room design address the radiation protection requirements?

By balancing the radiation head on the gantry with a shield. Signup and view all the answers

What was the purpose of the wedges used in these machines?

To shape the radiation beam. Signup and view all the answers

What type of treatments were often performed using the pitch and roll movements?

Single-field and single-shot treatments. Signup and view all the answers

What was used to control the radiation delivery in the absence of dosimetry monitoring?

A timer Signup and view all the answers

What is the purpose of modifying the exposure time with a transit time?

To accommodate the finite time it takes for the source to reach the treatment position Signup and view all the answers

X-ray Therapy: Tube Potential and Current

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