Radiologic Technology Licensure Examination (RTLE) Comprehensive Review: Cluster 1

Comprehensive practice flashcards in vocabulary style covering Imaging Equipment & Maintenance, Imaging Science Informatics, Radiation Physics & Characteristics, Radiation Protection, Radiobiology, and Quality Assurance/Control for the Philippine RTLE board exam review.

Electrostatics

The branch of physics that studies stationary electrical charges or electrons at rest.

Law of Repulsion–Attraction

The fundamental electrostatic law stating that like electrical charges repel each other and unlike charges attract.

Coulomb's Law

A mathematical law stating that electrostatic force between two charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them: $F = \frac{k(q_1 q_2)}{r^2}$, where $k = 9 \times 10^9\text{ N}\times\text{m}^2/\text{C}^2$.

Law of Concentration

The electrostatic law stating that electric charge concentration is greatest on the surface of highest or sharpest curvature, which necessitates smooth and rounded designs for x-ray tube housings to prevent electrical discharge.

Electrodynamics

The study of electric charges in motion in a predominantly single direction, creating an electric current.

Superconductor

A material (such as titanium or niobium) that exhibits zero electrical resistance to electron flow without requiring an electric potential, typically operating under conditions of extreme cold.

Potential Difference (Voltage)

The electrical pressure from a power source that pushes electrons through a circuit, measured in volts ($\text{V}$), where $1\text{ V} = 1\text{ Joule/Coulomb}$.

Ohm's Law

A fundamental electrical law stating that the voltage across a circuit or circuit element is equal to the current multiplied by the resistance: $V = IR$.

Capacitance

The ability of an electrical component or circuit to store energy in the form of accumulated electrostatic charge across two conducting plates separated by an insulator, measured in farads ($\text{F}$), where $1\text{ F} = 1\text{ C}/1\text{ V}$.

Series Circuit

An electrical circuit where elements are connected in a single path along a conductor, characterized by constant current ($I_T = I_1 = I_2 = I_3$), additive voltage ($V_T = V_1 + V_2 + V_3$), and additive resistance ($R_T = R_1 + R_2 + R_3$).

Parallel Circuit

An electrical circuit containing components that bridge across multiple branches, characterized by constant voltage across branches ($V_T = V_1 = V_2 = V_3$), additive current ($I_T = I_1 + I_2 + I_3$), and total resistance calculated as the reciprocal sum: $\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}$.

Magnetic Dipole

A tiny magnet with north and south poles created by the orbital motion and spin of an electron or nuclear proton.

Magnetic Permeability

The ability of a material to attract lines of magnetic field intensity or magnetic flux.

Magnetic Susceptibility

The degree or ease to which a material can be magnetized when placed in an external magnetic field.

Ferromagnetic Material

A material possessing high magnetic permeability and strong attraction to magnetic fields (such as iron, cobalt, nickel, and alnico alloys) that can be permanently magnetized.

Paramagnetic Material

A material possessing low magnetic permeability and weak, temporary attraction to magnetic fields (such as gadolinium, tungsten, and aluminum) with only a slight majority of aligned dipoles.

Diamagnetic Material

A material that is weakly repelled by both poles of a magnetic field and cannot be artificially magnetized (such as water, lead, gold, and silver).

Transformer

An electrical device that transforms alternating electric potential and current into higher or lower levels without altering AC frequency, operating on the principle of mutual induction between two coils sharing a magnetic core.

Transformer Law

The principle stating that voltage induced across coils is directly proportional to their turns ratio: $\frac{V_s}{V_p} = \frac{N_s}{N_p}$, while current is inversely proportional: $\frac{I_s}{I_p} = \frac{N_p}{N_s}$.

Autotransformer

A variable transformer featuring a single winding on a central iron core that operates on self-induction, utilizing selectable taps to adjust incoming line voltage to proper levels for the high-voltage and filament circuits.

Copper Loss ($I^2R$ Loss)

Power loss in a transformer caused by the electrical resistance of the wire windings, which dissipates energy as heat according to the formula $P = I^2R$.

Hysteresis Loss

Energy lost as heat in a transformer core due to the delayed magnetic response (lagging) of magnetic domains as the core repeatedly magnetizes and demagnetizes in alternating current.

Eddy Current Loss

Energy loss in transformer cores caused by circulating loops of induced electrical current flowing perpendicularly to the changing magnetic flux, minimized by laminating the core into thin sheets.

Shell-Type Transformer

The most efficient transformer design, constructed with a laminated iron core forming a double magnetic circuit and concentric primary and secondary windings wrapped around a central limb.

Rectification

The process of converting alternating current ($\text{AC}$) into unidirectional direct current ($\text{DC}$) to ensure electrons flow exclusively from cathode to anode inside the x-ray tube.

Half-Wave Rectification

A rectification circuit utilizing 1 to 2 diodes that permits current flow only during the positive half of the AC cycle, producing pulsating DC with 60 pulses per second and $100\%$ voltage ripple.

Full-Wave Rectification

A rectification circuit utilizing at least 4 diodes in a bridge arrangement to invert the negative half-cycle of AC, producing 120 pulses per second of pulsating DC with $100\%$ voltage ripple.

Voltage Ripple

The percentage drop in voltage from the maximum peak potential to zero or a lower level during each power cycle, measuring the degree of DC fluctuation.

High-Frequency Generator

A compact x-ray generator that converts incoming $60\,\text{Hz}$ power into $400\text{ to }25,000\,\text{Hz}$ high-frequency waveforms, producing a near-constant potential with less than $1\%$ voltage ripple.

Spinning-Top Test

A quality control procedure used on single-phase equipment where a spinning metal disc with a hole is exposed to evaluate timer accuracy or identify defective rectifiers by counting dots on film ($12\text{ dots}$ expected at $0.1\,\text{s}$ in full-wave rectification).

Synchronous Spinning-Top Test

A timer testing device driven by a synchronous motor for three-phase or high-frequency equipment that produces a continuous black arc on film, where the arc angle equals $360^\circ \times \text{exposure time (s)}$.

X-ray Tube

An evacuated electronic diode tube enclosed in a protective lead-lined housing that accelerates electrons from a cathode to an anode target to produce x-rays and heat.

Thermionic Emission

The emission or boiling off of electrons from a metallic filament (typically thoriated tungsten) when heated past approximately $2,200^\circ\text{C}$ by a low-voltage, high-current supply.

Focusing Cup

A negatively charged nickel shroud in the cathode assembly that electrostatically condenses the emitted electron cloud and directs it toward the focal track on the anode.

Space Charge Effect

The electrostatic phenomenon where an accumulated cloud of emitted electrons around the filament exerts a repulsive force that prevents additional electrons from leaving the wire until sufficient kVp is applied.

Line-Focus Principle

The geometric principle of angulating the anode target bevel ($7^\circ\text{ to }20^\circ$, typically $12^\circ$) so that the effective focal spot projected toward the patient is significantly smaller than the actual focal area struck by electrons, maximizing spatial resolution while preserving thermal capacity.

Anode Heel Effect

The absorption of x-rays within the heel of the angled target, causing radiation intensity to be higher on the cathode side ($\approx 120\%$) than on the anode side ($\approx 75\%$), creating an intensity variation of up to $45\%$ along the tube axis.

Off-Focus (Extrafocal) Radiation

X-ray photons produced when electrons bounce off the focal spot and interact with other areas of the anode, cathode, or vacuum envelope outside the designated focal track.

Stator

An induction-motor assembly consisting of a ring of electromagnets positioned outside the glass vacuum envelope that generates a rotating magnetic field to turn the rotor.

Rotor

An internal induction-motor component made of copper and soft iron mounted on silver-lubricated steel ball bearings inside the vacuum envelope, attached to the anode disk via a molybdenum shaft.

Heat Unit (HU)

A traditional measure of thermal energy deposited in the anode target, calculated for single-phase units as $\text{HU} = \text{kVp} \times \text{mA} \times \text{s}$ and for three-phase/high-frequency units as $\text{HU} = 1.4 \times \text{kVp} \times \text{mA} \times \text{s}$.

Radiographic Rating Chart

A manufacturer-supplied chart plotting kVp against exposure time for specific mA stations that indicates which combinations of exposure parameters are safe (below curve) or hazardous (above curve) for a single exposure.

Anode Cooling Chart

A thermal management graph illustrating the maximum heat capacity of an x-ray tube anode and the time required for the anode to cool after heat deposition.

Automatic Exposure Control (AEC)

A radiation-measuring device (such as a parallel-plate ionization chamber) that automatically terminates the radiographic exposure time when the image receptor has received a preset, diagnostic amount of radiation.

Minimum Response Time

The shortest possible exposure time that an automatic exposure control system requires to detect radiation and terminate the exposure (typically $\approx 0.001\,\text{s}$ in modern SCR-based units).

Backup Timer

A safety timer mechanism set to terminate an AEC exposure if the system fails to prevent excessive patient exposure and tube overloading, recommended at $150\%$ of expected mAs (with a maximum regulatory limit of $600\,\text{mAs}$ above $50\,\text{kVp}$).

Automatic Brightness Control (ABC)

A fluoroscopic feedback system that automatically modulates tube potential (kVp) and tube current (mA) to compensate for variations in patient thickness or density, maintaining constant image brightness at the input phosphor.

Charge-Coupled Device (CCD)

A solid-state semiconducting device in digital fluoroscopy that replaces the television camera tube, converting visible light from the output phosphor directly into electrical charges with high sensitivity, low noise, and minimal image lag.

Informatics

The interdisciplinary science concerned with the storage, processing, communication, management, and optimal use of information and data in healthcare.

Biomedical Informatics (BMI)

An interdisciplinary field combining medicine, biology, and computational methods to develop platforms supporting clinical care, research, and public health across five subspecialties: translational bioinformatics, clinical research informatics, clinical informatics, consumer health informatics, and public health informatics.

Picture Archiving and Communication System (PACS)

A networked electronic system that acquires, stores, distributes, and displays digital medical images across modalities without physical film.

Hospital Information System (HIS)

A comprehensive, enterprise-wide software platform managing administrative, legal, financial, scheduling, and general healthcare operations for an entire hospital.

Radiology Information System (RIS)

A departmental software system specific to radiology that handles patient scheduling, worklists, examination tracking, billing, and radiologist diagnostic reporting.

Electronic Health Record (EHR)

A comprehensive digital compilation of a patient's lifelong health history, laboratory results, medications, and medical imaging reports accessible across facilities and via patient portals.

Vendor Neutral Archive (VNA)

An enterprise image-storage archive that stores medical images in standard non-proprietary formats, enabling cross-platform interoperability among different PACS, HIS, and RIS vendors.

DICOM (Digital Imaging and Communications in Medicine)

The global standard protocol established by the ACR and NEMA in 1983 (standardized in 1993) for producing, transmitting, storing, retrieving, displaying, and printing digital medical images across diverse equipment vendors.

Service Object Pair (SOP)

A DICOM concept combining an Information Object Class (defining data, such as a CT scan) with a Service Class (defining an action, such as image storage).

Health Level 7 (HL7)

An international standard protocol operating at the application layer that defines the formatting and transmission of clinical and administrative non-imaging healthcare data (such as orders, admissions, and lab results).

Integrating the Healthcare Enterprise (IHE)

An initiative launched in 1998 by healthcare professionals and IT industry leaders to improve interoperability by coordinating the seamless implementation of DICOM and HL7 standards in clinical workflows.

Pixel

A single 'picture element' representing the smallest individual two-dimensional unit of a digital matrix, with an assigned numerical value corresponding to tissue brightness or grayscale level.

Voxel

A three-dimensional 'volume element' representing a volume of patient tissue, calculated as the pixel area multiplied by the slice thickness ($\text{Voxel} = \text{pixel area} \times \text{slice thickness}$).

Bit Depth

The number of bits allocated per pixel determining the available shades of gray in a digital image, calculated as $2^{\text{bit depth}}$.

Flat-Fielding

An automatic software preprocessing calibration that corrects pixel-to-pixel, row-to-row, and column-to-column sensitivity differences across a digital detector using offset and gain images.

Window and Level

A post-processing adjustment where window width adjusts the displayed contrast scale and window level adjusts image brightness across the dynamic range.

Lossless Compression

A reversible data compression technique where no image information is lost upon reconstruction, preserving all original pixel data for diagnostic interpretation.

Lossy Compression

An irreversible compression method that achieves high compression ratios by discarding redundant or fine detail, carrying potential risk in primary diagnostic interpretation.

Photometry

The science measuring the response of the human eye to visible light, established with standard CIE human vision sensitivity curves (peaking at $555\,\text{nm}$ for photopic and $505\,\text{nm}$ for scotopic vision).

Luminance

The quantitative measure of brightness from an active light source (such as a digital monitor or viewbox), expressed in candela per square meter ($\text{cd/m}^2$) or nits.

Luminance Meter

A photometric device used in quality control to verify display monitor brightness, uniformity, and adherence to the DICOM Grayscale Standard Display Function (GSDF).

Aperture Ratio

The fraction or percentage of a liquid crystal display (LCD) pixel face available for transmitting backlight, typically ranging from $50\%$ to $80\%$.

Ionization

The process of adding or removing an orbital electron from an atom, producing a separated free electron and a positive ion termed an ion pair.

Excitation

The addition of energy to an atomic system that raises orbital electrons to higher energy states without expelling them from the atom.

Alpha Particle

A particulate form of radiation emitted from the nucleus of heavy radionuclides ($Z > 82$), consisting of 2 protons and 2 neutrons ($\text{mass} = 4\,\text{amu}$, $\text{charge} = +2$) characterized by high linear energy transfer and low penetration.

Beta Particle

An energetic electron or positron ($\text{mass} = 0\,\text{amu}$, $\text{charge} = \pm 1$) emitted from the nucleus of an unstable radionuclide during radioactive decay.

Gamma Radiation

High-energy electromagnetic packets of radiant energy (photons) emitted from the nucleus of an unstable radionuclide during nuclear rearrangement.

Electron Binding Energy ($E_b$)

The strength of attachment of an orbital electron to the atomic nucleus, which increases with proximity to the nucleus (highest in K-shell) and with higher atomic number ($Z$).

Isotopes

Atoms possessing the same atomic number ($Z$, number of protons) but different atomic mass numbers ($A$, different number of neutrons).

Isobars

Atomic nuclei possessing the same atomic mass number ($A$) but different atomic numbers ($Z$), representing different chemical elements.

Isotones

Atoms possessing different atomic numbers ($Z$) and different mass numbers ($A$) but an identical number of neutrons ($A - Z$).

Isomers

Identical atomic nuclei sharing the same atomic number ($Z$) and mass number ($A$) that exist at different nuclear energy states, such as technetium-99m.

Bremsstrahlung Radiation

Radiation produced when a projectile electron is decelerated and deflected by the strong electrostatic force field of the tungsten target nucleus, releasing energy as a continuous x-ray spectrum comprising $80\%\text{ to }90\%$ of the diagnostic beam.

Characteristic Radiation

Discrete x-rays produced when an incident electron ejects an inner-shell electron (such as the K-shell) and an outer-shell electron transitions into the vacancy, emitting a photon whose energy equals the difference in binding energies between the two shells.

Coherent Scattering

An interaction occurring below $10\,\text{keV}$ where an incident x-ray photon excites an entire atom, causing the photon to change direction without transferring energy or causing ionization.

Compton Scattering

An interaction occurring throughout the diagnostic range where an incident photon ejects an outer-shell electron (Compton electron), deflecting the photon with reduced energy and longer wavelength, serving as the main source of image fog and occupational exposure.

Photoelectric Effect

An interaction where an incident photon is completely absorbed by an inner-shell electron, ejecting a photoelectron ($E_{\text{KE}} = E_i - E_b$) and producing characteristic secondary radiation, providing primary radiographic subject contrast while increasing patient dose.

Pair Production

A high-energy interaction requiring an incident photon of at least $1.02\,\text{MeV}$ that interacts with the nuclear force field to disappear, creating a negatron (electron) and a positron.

Annihilation Radiation

The reaction where a positron created during pair production loses kinetic energy and unites with an electron, converting their rest mass into two $0.511\,\text{MeV}$ photons traveling in opposite directions ($180^\circ$ apart), forming the physical basis of PET imaging.

Photodisintegration

A high-energy photon interaction requiring a minimum threshold of $10\,\text{MeV}$ where an incident photon is absorbed directly by the atomic nucleus, causing the ejection of a nucleon (proton or neutron) or nuclear fragment.

Differential Absorption

The difference in x-ray absorption between tissues that produces radiographic contrast, governed primarily by the competition between photoelectric absorption (proportional to $Z^3$ and mass density) and transmission.

Half-Value Layer (HVL)

The thickness of designated absorbing material (typically aluminum) required to reduce the intensity of an x-ray beam to one-half of its original value, serving as the standard measure of beam quality.

Tenth-Value Layer (TVL)

The thickness of absorbing material that reduces radiation beam intensity to one-tenth of its initial value, approximately equivalent to $3.3\text{ HVL}$.

ALARA

A core radiation safety philosophy meaning 'As Low As Reasonably Achievable', designed to minimize radiation exposure to patients and workers while accounting for economic and societal factors.

Air Kerma ($\text{Gy}_a$)

The SI unit representing kinetic energy released per unit mass of air during the ionization and excitation of air molecules by photons, measured in joules per kilogram ($\text{J/kg}$).

Absorbed Dose ($\text{Gy}_t$)

The physical radiation quantity expressing energy deposited per unit mass of irradiated material or biological tissue, where $1\,\text{Gray} = 1\,\text{J/kg} = 100\,\text{rad}$.

Equivalent Dose ($H$)

A radiation protection quantity calculated as absorbed dose multiplied by the dimensionless radiation weighting factor ($W_r$) to quantify relative biological harm from different radiation types: $H = D \times W_r$, expressed in sieverts ($\text{Sv}$).

Effective Dose ($E$)

The overall risk indicator calculated as the sum of equivalent doses to individual organs multiplied by tissue weighting factors ($W_t$): $E = \sum (D \times W_r \times W_t)$, representing equivalent whole-body stochastic risk in sieverts ($\text{Sv}$).

Primary Protective Barrier

A radiation shielding partition designed to intercept the direct useful x-ray beam, requiring at least $1.5\,\text{mm}$ ($1/16\text{ inch}$) lead equivalence extending to a height of $2.1\,\text{meters}$ ($7\text{ feet}$) from the floor.

Secondary Protective Barrier

A shielding partition designed to attenuate scatter and leakage radiation only, typically requiring $0.8\,\text{mm}$ ($1/32\text{ inch}$) lead equivalence running to the ceiling (such as control booth walls).

Primary vs. Secondary Radiation

The two primary classifications of radiation accounted for in room shielding design: the direct useful beam exiting the x-ray tube window versus secondary radiation composed of leakage escaping the housing and scatter deflected from the patient.

Controlled Area

A designated hospital workspace occupied by monitored radiation personnel and patients, regulated by an annual occupational limit of $50\,\text{mSv/year}$ ($1\,\text{mSv/week}$ design limit).