IEM

What is a machine's reliability affected by?

A machine can still work even if it has a defect, however, it is not reliable, which is why maintenance is required.

What is electric current?

The flow of electrons.

What does voltage or potential difference relate to in an electrical context?

It is responsible for thermionic emission.

What type of current is preferred in radiologic technology?

Direct Current (DC) because it is more stable than alternating current.

What is the function of Diala Oil in an X-ray machine?

It absorbs heat generated from the X-ray tube to prevent the housing from becoming too hot to touch.

What happens to a filament when it burns out?

The filament is thin and evaporates instead of melting due to high temperatures.

How does electric current actually travel?

Electric current does not really travel in a wave-like pattern; it peaks and dips into zero.

What is the basic function of equipment maintenance?

To keep equipment in reliable working order, including routine upkeep and corrective repairs.

What allows fluoroscopy to continuously view physiology?

Its ability to allow real-time imaging of bodily functions.

What is the relationship between current and voltage according to Ohm's Law?

Current is directly proportional to applied potential difference and inversely proportional to the resistance.

What occurs during thermionic emission in an X-ray tube?

Electrons are emitted from the heated filament.

What does an electrical transformer do?

Transfers electricity from one circuit to another while changing the voltage level.

What is the main difference between a step-up and step-down transformer?

A step-up transformer increases voltage while a step-down transformer decreases it.

What are the three causes of X-ray tube failure?

Filament burn-out, inactivity, and slow leaks.

What does the filament affect in an X-ray tube?

The number of electrons released during operation.

What is the purpose of a circuit breaker?

To protect an electrical circuit from damage caused by overcurrent or overload.

What is the significance of the Anode Heel Effect?

It causes radiation intensity to vary along the anode-cathode axis of the X-ray tube.

What is the function of capacitors in electrical systems?

To store electrostatic energy and release it when needed.

How is a high-frequency generator beneficial in X-ray technology?

It is more efficient and produces sharper, better quality images than traditional generators.

Formula for potential difference according to Ohm's Law

$$V = I \times R$$

Three primary physical effects produced by an electric current

Heat generation, magnetic field creation, and chemical transformation.

Reason alternating current (AC) is avoided in radiology

It can cause overloading because unconsumed power flows back into the device.

Unit of measurement for electrical resistance

Ohms ($\Omega$).

Fundamental law of magnetic poles

Like magnetic poles repel one another, while unlike magnetic poles attract.

Faraday's Law of Induction

States that a changing magnetic field near a conductor induces an electric current in that conductor.

Circuit protection mechanism of a fuse

Melts when electrical current exceeds its rating, opening the circuit to prevent component damage.

Purpose of an Uninterrupted Power Supply (UPS) in medical imaging

Provides temporary backup power to stabilize voltage fluctuations and allow proper equipment shutdown during power outages.

Live Wire

A high-voltage active wire without an insulating jacket, typically located on utility poles.

Cause of copper loss in electrical transformers

Resistance to electric current within the primary and secondary wire windings, generating heat loss.

Cause of eddy current loss in a transformer core

Unwanted circulating currents induced in the magnetic core material by changing magnetic fields ($I^2 R$ loss).

Hysteresis loss in transformer cores

Energy loss caused by continuous magnetization and demagnetization of the core material during alternating current cycles.

Difference in energy storage between capacitors and batteries

Capacitors store potential energy as electrostatic charges in an electric field, whereas batteries store energy through chemical reactions.

Difference in discharge speed between capacitors and batteries

Capacitors discharge energy rapidly in milliseconds, whereas batteries discharge continuously over minutes or hours.

Function of a diode in a rectifier circuit

Acts as a one-way electrical valve that permits current flow in only a single direction.

Material composition of an X-ray tube anode target

Tungsten-Rhenium alloy.

Atomic number and melting point of Tungsten

Atomic number $74$, with a melting point of $3422\,^\circ\text{C}$.

Atomic number and melting point of Rhenium

Atomic number $75$, with a melting point of $3182\,^\circ\text{C}$.

Comparison between stationary and rotating anode operation

Stationary anodes receive electron impacts on a single fixed surface, while rotating anodes spread impacts around a spinning target disc.

Glass material used for X-ray tube envelopes

Pyrex glass.

Function of the cathode focusing cup

Houses the filament and electrostatically concentrates the electron beam toward the target during thermionic emission.

Operating voltage range across a diagnostic X-ray tube

$40$ to $120\,\text{kV}$.

Line Focus Principle

The physical geometric principle where angling the anode target creates an effective focal spot size smaller than the actual focal spot size.

Penumbra in radiographic images

The blurred margin or geometric unsharpness at object edges caused by the finite dimensions of the focal spot.

Energy conversion ratio in diagnostic X-ray production

Less than $1\%$ of electron kinetic energy produces useful X-rays, while over $99\%$ is lost as heat.

Target micro-cracking cause

Thermal stress produced by rapid surface heating during intense electron beam exposures on the anode target.

Function of a line voltage compensator

Measures incoming line voltage and adjusts it to a constant $220\,\text{V}$ before supplying the autotransformer.

Auto Transformer

A transformer with a single continuous wire winding wrapped around a core that functions as a flexible voltage regulator.

Falling Load High Frequency Generator

A generator design that automatically starts exposures at the highest safe mA and reduces current over time to minimize exposure duration.

Recommended exposure settings for standard tube warm-up

Low tube voltage ($60\text{--}70\,\text{kVp}$) combined with a long exposure duration ($1\text{--}5\,\text{s}$).

Machine defect vs reliability

Defective equipment can still function, but it lacks reliability, making regular maintenance necessary.

Linearity in imaging equipment calibration

The proportional relationship where system output scales directly with input (e.g., $100 = 100$).

Primary clinical function of fluoroscopy

Continuous real-time visual assessment of internal anatomical structures and physiological functions.

Definition of electric current

The flow rate of electric charge carriers (such as electrons) passing through a conductor.

Definition of electrical potential difference (voltage)

The electrical force or charge energy differential between two points driving current flow.

Three primary physical effects of electric current

Generation of heat, creation of a surrounding magnetic field, and induction of chemical transformations.

Direct current (DC)

Unidirectional flow of electric charge with constant direction over time.

Alternating current (AC)

Electric current that continuously changes magnitude and periodically reverses direction over time.

Disadvantage of using alternating current (AC) in radiology

Causes electrical overloading because unconsumed power flows back into the device.

Electrical resistance definition and unit

The opposition to electric current flow within a material, measured in ohms ($\Omega$).

Mathematical expression of Ohm's Law

$$V = I \times R$$

Fundamental law of magnetic poles

Like magnetic poles repel each other, while unlike magnetic poles attract.

Faraday's Law of Induction

Principle stating that a moving or changing magnetic field near a conductor induces an electric current.

Protective action of an electrical fuse

Melts its internal metal wire when current exceeds rated limits, creating an open circuit.

Electro-mechanical circuit breaker operation

Uses an internal electromagnet during excessive current draw to pull electrical contacts apart.

Purpose of electrical grounding (earthing)

Provides a low-impedance path to the earth to safely discharge excess electricity and protect users.

Function of an Uninterrupted Power Supply (UPS)

Delivers temporary emergency backup power during outages to prevent voltage spikes and enable safe equipment shutdown.

Electrical transformer principle

Transfers electrical energy between circuits via magnetic induction, altering voltage while maintaining constant frequency.

Live wire definition

Uninsulated high-voltage utility wire mounted on poles above residential lines.

Step-up transformer operational shift

Converts low voltage and high current into high voltage and low current.

Step-down transformer operational shift

Converts high voltage and low current into low voltage and high current.

Advantage of three-phase transformer construction

Prevents electrical current from dipping to zero, maintaining high output stability.

Copper loss in transformer windings

Waste heat generated by resistance in primary and secondary copper coil wires ($I^2 \times R$ loss).

Method to reduce copper loss in transformers

Constructing primary and secondary windings using wire with a larger cross-sectional area.

Cause of eddy current loss in a transformer core

Unwanted circulating currents induced inside the magnetic core material by alternating magnetic fields.

Hysteresis loss in a transformer core

Energy loss resulting from continuous molecular magnetization and demagnetization cycles in AC operation.

Energy storage mechanism in capacitors vs batteries

Capacitors store potential energy electrostatically in an electric field; batteries store potential energy chemically.

Discharge rate difference between capacitors and batteries

Capacitors release energy in milliseconds; batteries discharge slowly and steadily over minutes or hours.

Current type compatibility for capacitors vs batteries

Capacitors function with both AC and DC; batteries function exclusively with DC.

Rectification process

Electrical conversion of alternating current (AC) into direct current (DC).

Function of a diode in a rectifier

Acts as a unidirectional valve allowing electric current to flow in only one direction.

Historical significance of the Crookes tube

Sealed vacuum glass tube invented by Sir William Crookes to study gases, leading to electron and X-ray discoveries.

Primary feature of the Coolidge tube

First practical X-ray tube (introduced in $1913$) to utilize thermionic emission from a hot tungsten filament.

Glass composition of an X-ray tube envelope

Pyrex glass.

Function of the evacuated vacuum envelope

Eliminates air molecules so electrons can accelerate from cathode to anode without collisions.

Role of Diala Oil in X-ray tube housing

Insulating oil that absorbs thermal energy from the tube, keeping the housing cool to touch.

Material used for X-ray tube housing insulation

Lead lining to prevent leakage radiation escape.

Composition of an X-ray target disc

Tungsten-Rhenium alloy.

Atomic number and melting point of Tungsten

Atomic number $\text{Z} = 74$, melting point $3422\,^\circ\text{C}$.

Atomic number and melting point of Rhenium

Atomic number $\text{Z} = 75$, melting point $3182\,^\circ\text{C}$.

Purpose of adding Rhenium to Tungsten in anode targets

Increases electron binding energy and structural elasticity to withstand thermal shock.

Stationary anode target limitation

Electron collisions strike a single fixed target spot, causing rapid overheating and limiting power capacity.

Rotating anode operation speed and temperature

Rotates target discs up to $10000\,\text{rpm}$ at operating temperatures reaching $2000\,^\circ\text{C}$.

Anode Heel Effect definition

Phenomenon where X-ray beam intensity is higher on the cathode side and lower on the anode side due to target self-attenuation.

Molybdenum rotor neck properties

Atomic number $\text{Z} = 42$, melting point $2623\,^\circ\text{C}$, selected for high heat dissipation and structural support.

Operating principle of an X-ray tube stator

Uses driving coils outside the vacuum envelope to create a rotating magnetic field that turns the rotor by electromagnetic induction.

Cathode filament alloy composition

Thorium-plated Tungsten wire.

Atomic number and melting point of Thorium

Atomic number $\text{Z} = 90$, melting point $1755\,^\circ\text{C}$.

Function of the cathode focusing cup

Electrostatically focuses the thermionically emitted electron cloud toward the anode target focal spot.

Operating potential difference range across diagnostic X-ray tubes

$$40\text{--}120\,\text{kV}$$

Line Focus Principle

Angling the anode target ($6\text{--}15^\circ$) produces an effective focal spot size smaller than the actual focal spot size.