DRAD1003: The Journey of an X-ray Image - From Patient to PACS

Comprehensive vocabulary flashcards covering the radiographic imaging pathway from exposure factor selection, X-ray physics, and patient interaction to digital image formation, dosimetry, and PACS archiving.

Primary X-ray Beam

The emerging X-ray beam exiting through the window of the X-ray tube that traverses the patient before unattenuated radiation reaches the detector.

X-ray Quality

The penetrating ability of an X-ray beam determined by photon energy ($\text{keV}$), which is principally governed by the peak tube voltage ($\text{kVp}$).

X-ray Quantity

The total number of photons within the X-ray beam, determining beam intensity and primarily regulated by the product of tube current and exposure time ($\text{mAs}$).

Tube Current ($\text{mA}$)

A measure of the rate of flow of electrical charge carriers travelling from the filament cathode to the target anode inside the X-ray tube.

Filtration

The insertion of absorbing materials (such as aluminium or copper) into the beam path to remove non-penetrating, low-energy photons, thereby improving beam quality and decreasing patient dose.

Small Focal Spot

An X-ray tube target setting producing a narrow beam origin that minimizes geometric blur and maximizes spatial resolution, but possesses a lower heat-loading capacity.

Large Focal Spot

An X-ray tube target setting that distributes electron bombardment over a broader area to safely handle high heat outputs and exposure workloads, at the expense of greater geometric unsharpness.

Focus to Detector Distance ($\text{FDD}$)

The measured distance from the focal spot on the target anode to the surface of the image receptor, which alters detector exposure according to the inverse square law.

Attenuation

The gradual reduction in the intensity of an X-ray beam as it traverses matter, occurring through a combination of partial absorption, scattering, and total absorption processes.

Linear Attenuation Coefficient ($\mu$)

The fractional reduction in intensity of a monoenergetic, parallel X-ray beam per centimetre thickness of a specified absorbing material.

Half Value Thickness ($\text{HVT}$)

The thickness of an attenuating material (such as aluminium) required to reduce the initial intensity of an X-ray beam by $50\%$, commonly measured during quality assurance.

Absorbed Dose

The physical quantity representing the total radiation energy deposited per unit mass of matter, expressed in units of joules per kilogram ($\text{J\,kg}^{-1}$) or grays ($\text{Gy}$).

Equivalent Dose

A radiation protection quantity calculated by weighting the absorbed dose by a radiation weighting factor ($W_R$) to reflect the biological harm associated with a specific radiation type.

Effective Dose

A radiation quantity that estimates the total biological risk to a patient by weighting equivalent doses across various irradiated organs according to their specific tissue weighting factors ($W_T$), measured in sieverts ($\text{Sv}$).

Photoelectric Absorption

An interaction where an incident X-ray photon transfers all of its energy to an inner-shell orbital electron, ejecting it as a photoelectron and causing total photon absorption, which enhances radiographic contrast.

Compton Scatter

An interaction where an incident photon ejects a loosely bound outer-shell electron and is deflected in a new direction with reduced energy, creating scatter radiation that degrades image quality.

Pair Production

A high-energy interaction requiring photon energies exceeding $1.02\,\text{MeV}$, where a photon interacts with a nuclear electric field and transforms into an electron-positron pair.

Computed Radiography (CR)

A digital imaging technique that captures a latent image on a reusable photostimulable phosphor (PSP) plate inside a cassette, which is subsequently scanned with a laser inside a dedicated reader to release visible light.

Direct Digital Radiography (DR)

An imaging system using a flat-panel detector (direct or indirect conversion) that immediately captures and converts incident X-rays into digital signals without requiring a separate plate reader.

Histogram

A discrete frequency distribution plot illustrating the number of pixels at each digital exposure value recorded by an image receptor, used to guide image processing algorithms.

Window Width

A digital post-processing control that governs displayed radiographic contrast by defining the specific range of pixel values assigned across the full greyscale display.

Window Level

A digital post-processing control that adjusts overall image brightness by establishing the central midpoint value of the displayed greyscale range.

PACS (Picture Archiving and Communication System)

A specialized medical network architecture designed for electronically storing, retrieving, managing, and distributing digital radiological images across clinical workstations.

DICOM (Digital Imaging and Communications in Medicine)

The universal standard file format and communications protocol that enables the seamless transmission, viewing, and exchange of medical images and demographic metadata across multi-vendor equipment.

The Three Pillars of Radiation Protection

The fundamental principles guiding clinical radiation safety practice: Justification (ensuring clinical benefit), Optimisation (applying ALARA to minimize dose), and Protection/Dose Limitation.