Part 3: Radiation Therapy Equipment

Simulation

The use of images and simulation software to localize the treatment iso center, define the size and shape of the treatment volume relative to important normal tissue, and translate this information back on the patient with a laser based patient marking system. The patient is marked and documented for daily set up and treatment.

Fusion imaging

Involves combining anatomical imaging with functional imaging.

Ex: PET CT or PET MRI

Slip ring

Allows continuous rotation of tube and detectors

Auxiliary devices

Patient immobilization and positioning devices; aid in daily treatment set up and reproducibility; devices designed to place the patient in a particular position for treatment

Justification

The use of radiation for each patient must be ______ and the benefits need to out weight the risks

Optimization

Practicing ALARA, radiation doses to be as low as possible while achieving the required clinical outcomes

Dose limitation

Ensure the radiation exposure does not exceed safety limitations for patients and staff

Medical emergencies

Patient health issues such as fainting, seizures, or cardiac arrest

Radiation emergencies

Unintended exposure or radiation leaks

Equipment failures

Malfunction or breakdown of the simulation equipment

Environmental emergencies

Fire, power outages, or natural disasters

Image-Guided Radiation Therapy (IGRT)

Using imaging technologies to verify and adjust a patient’s positioning and the location of the tumor immediately before and sometimes during a radiation therapy treatment

Wavelength

Distance between crests in the wave

Frequency

Number of complete cycles/second

Thermionic emission

A phenomenon in which electrons are omitted from the surface of a material due to thermal energy (filament on cathode). When a material, typically a metal (tungsten) or semiconductor, is heated to a high temperature, the thermal energy provided to the electrons overcomes the work function of the material (the minimum energy needed to remove an electron from the surface). As a result, electrons gain enough energy to escape from the surface into the surrounding vacuum or another medium.

Potential difference

causes the negative electrons to be repelled from the cathode and drawn towards the positive anode very quickly.

X-ray production

The electron strikes the anode, causing an interaction with the tungsten atoms on the anode, creating either heat or x-rays.

Bremsstrahlung radiation

The main form of radiation produced in x-ray tube (75-80%) output; electrons are attracted to the nucleus of the atom and are drawn to them hence changing their direction and kinetic energy

Characteristic radiation

Direct interaction between incoming electron and electrons on inner shell of an atom; The incoming electron has enough energy to remove the electron from its shell (ionization); this causes a vacancy that another orbital electron moves into fill thus releasing radiation; The change in potential energy from one orbital shell to another is what is released as radiation

Ionization

The ability for an electron or photon to cause an atom to admit radiation. This can be done through interactions with orbital electrons or with the nucleus. Only UV-C, x-rays, and gamma rays have the ability to ionize

Kinetic energy

When matter is in motion

Binding energy

The connection between the nucleus and its orbital electrons; Electrons closer to the nucleus have a higher _________; depends on orbital shell

Potential energy

The inherent energy the electron carries; It’s ability to “do work “; Varies depending on the orbital shell; Electrons closer to the nucleus carry less _____.

Penetration

Ability of an x-ray (photon) to pass through a human

Cathode

One of the electrodes found in the x-ray tube

Negatively charged

Consists of two parts: filament and focusing cup

Primary function: produce electrons and focus the stream toward the metal anode

Filament

Small coil of wire made of thoriated tungsten (has high melting temp); current runs through wire.

Most x-ray tubes have dual _______ to permit a large or small source of electrons

Current heats the coil, electrons boil off and are omitted from _____.

Focusing cup

A negatively charged component that surrounds the filament and focuses the emitted electrons into a narrow beam, directed towards the anode.

Anode

Positively charged electrode (often made of tungsten) that Attracts electrons and is the target where x-rays are produced

Straight, divergent path

What kind of path do the x-rays have?

High voltage power supply

Provides the necessary potential difference (kilovolts, kV) between the cathode and anode, accelerating the electrons toward the anode

Vacuum envelope

Removes air from the x-ray tube and allows uninterrupted flow of electrons from the cathode to the anode

Cooling system

Dissipation of heat generated during x-ray production, using methods such as oil or water, circulation, cooling fins, and fans

Protective Housing

Shields against radiation, protects the x-ray tube components, provides electrical insulation, and manages heat indirectly through elements like insulating oil

Imaging Phantoms

Objects that simulate human tissue and are used to calibrate and test the performance of imaging devices

Contrast Agents

Substances used to enhance the visibility of structures or fluids within the body

Specialized Software

Includes treatment planning systems, image, processing, and verification software