Radiology and X-Ray Physics Lecture Review

Flashcards covering x-ray discovery, physics principles, equipment components, radiation safety, and digital imaging terminology.

Roentgen

The individual who discovered x-rays in November 1895.

SID exposure reduction

An increase in SID to $48\,\text{inches}$ can reduce the patient's exposure by $12-15\%$,.

Trendelenburg

A patient position where the head is lower than their feet.

X-rays

A type of ionizing radiation that travels at the speed of light.

Grid

A device placed between the patient and the IR to absorb scatter radiation; typically utilized when part thickness is greater than $10\,\text{cm}$.

Collimation

A process that should be symmetrical and parallel to IR margins; the device itself controls the size of the field of view.

Rectification

The process of changing the current to the x-ray tube from alternating to direct.

Inherent filtration

Components including the glass envelope, insulating oil, and glass window.

Small focal spot

The focal spot size that provides better recorded detail.

Anode

The component of the x-ray tube that has a positive charge.

ADC

A device that converts an analog signal to a digital signal.

Focusing cup

A component in the x-ray tube that has a negative charge.

X-ray production efficiency

$98-99\%$ of energy used to produce x-rays results in heat.

AEC (Automatic Exposure Control)

A system that terminates the exposure when the IR has received the correct amount of exposure.

Radiosensitivity of cells

Epithelial cells are more radiosensitive, while muscle cells are less radiosensitive.

Reproductive death

A state that occurs when a cell receives $1-10\,Gy$ (gray) of radiation and loses its ability to reproduce.

Cells

The basic component of all living things.

PBL (Positive Beam Limitation)

A feature that automatically restricts the primary beam to the size of the IR.

Line focus principal

A principal resulting from the electron beam striking an angled target.

Secondary radiation

The combination of scatter and leakage radiation.

Crooke's tubes

The type of tubes used for all early x-rays.

Anode heel effect

The effect explaining why the intensity of the x-ray beam is greater on the cathode side of the tube.

Filament circuit

The circuit responsible for delivering electrical current to the x-ray tube filament.

Synchronous timer

The least accurate of all timers for exposures less than $1/60$ a second.

Autotransformer controls

Basic controls located on the control circuit.

Cathode

The source of electrons in the x-ray tube; typically contains a filament made of tungsten.

KVP meter

A device connected to the autotransformer that measures the voltage output.

Added filtration

An aluminum sheet that can be added to the outside of the x-ray tube.

Geometric factors

Factors including recorded detail, distortion, and magnification.

Matrix

A larger version of this allows for more pixels in an image.

Quantum mottle

A condition occurring when the system is unable to record detail due to too few x-ray photons; reduced by increasing mAs.

Motion

The cause of blurring on a medical image.

Distortion

Caused by improper alignment of the tube or CR.

mAs

The factor used to control density, quantity of radiation, and reduce quantum mottle.

Image annotation

A feature allowing technicians to add text or markers to an image post-exam.

Pair production

An interaction that produces $2$ electrons.

Benefit vs Risk

The principle an ordering physician should use when requesting x-rays.

Target theory

States that there is a specific molecule in a cell that must be inactivated to damage the cell or cause cell death.

3 Cardinal principles of radiation protection

Time, distance, and shielding.

Lymphocyte

A cell with a lifespan of $24\,\text{hours}$.

DQE

A measurement of how efficiently the system can convert x-rays into a useful image.

Late somatic effects

Effects that occur months or years after radiation exposure.

Spatial resolution

The ability of the imaging system to show small details.

Direct effect

Occurs when the x-ray beam interacts directly with DNA.

Compton effect

An interaction where the x-ray photon interacts with outer shell electrons.

Mass

The amount or quantity of matter.

Coherent scattering

Also known as Thompson's scattering.

Ionization

A process where an electron is removed from its energy shell.

Indirect effect

Occurs when an x-ray photon interacts with a non-critical molecule such as water.

Ion

An atom that has lost or gained an electron.

Fluoroscopy

X-ray in motion.

Epilation

The medical term for hair loss.

ALARA

As low as reasonably achievable.

Physics

The branch of science dealing with matter, energy, and their relation.

Artifacts

Any unwanted features on a medical image that may obscure anatomy.

PACS

Picture archiving and communication system.

Bremsstrahlung

German for 'braking'.

Window level

A digital control used to change the brightness of an image.

Long scale contrast

A minimal difference between light and dark areas of an image.

Window width

Used to adjust the black/white contrast of an image.

Gamma rays

High energy electromagnetic radiation resulting from radioactive decay.

Personnel monitoring devices

Includes OSL'S, TLD'S, and pocket ionization chambers.

Binding energy

The amount of energy necessary to remove an electron from its orbital shell.

Thermionic emission

The process of 'boiling' off electrons.

Acute radiation syndrome

The official term for radiation illness.

Law of Bergoine and Tribondeau

Establishes the basis for human radiosensitivity to ionizing radiation, noting that immature tissues/organs are more radiosensitive.

Stochastic

An effect that is NOT dose dependent.

Skin erythema

The first observed effects of radiation.

Fetal dose limit

The total allowable dose for a fetus is $5\,mSv$ (millisieverts).