Physics Chapters 1-4

Energy and Radiation

• Energy is defined as the ability to do work.
• Radiation is the transfer of energy from one location to another through electromagnetic waves.

Elements and the Periodic Table

• There are approximately 300 known elements.
• The periodic table of elements is attributed to Dimitri Mendeleev.
• The horizontal rows in the periodic table are called periods.
• Hydrogen is the only element that is not placed in any group of the periodic table.

X-rays and Electromagnetic Radiation

• A single unit of electromagnetic radiation is also called a photon.
• The frequency of electromagnetic radiation is constant for all radiation.
• X-rays are a form of electromagnetic radiation.
• The energy of characteristic x-rays increases with increasing atomic number of the target material.
• Bremsstrahlung radiation has velocity varying from zero to the speed of light.
• Characteristic x-rays have energy characteristic of the target material.

Radiation Protection

• Time, distance, and shielding are methods of radiation protection.
• The inverse square law states that intensity is inversely proportional to the square of the distance.

Electricity and Electronics

• Electrification can occur through excitation, induction, or diffusion.
• Static electricity can result in magnetism.
• The unit of electrostatic charge is the coulomb.
• The principal electrostatic law states that like charges repel, and opposite charges attract.
• An electron will repel a proton.
• Objects become electrified because of the transfer of electrons.
• The autotransformer operates on the principle of Faraday's law.

X-ray Tubes and Equipment

• The principal component of an x-ray tube is the anode.
• The cathode is negatively charged.
• The filament transformer increases current.
• The effective focal spot and radiation intensity on the anode side of the x-ray beam are affected by the heel effect.
• Electric energy can be converted into thermal energy by a lamp.

Physics and Measurements

• The fundamental unit of force is the newton.
• The binding energy of an electron to a nucleus is higher for a low-Z atom than for a high-Z atom.
• The energy of an electron is expressed in electron volts (eV).
• The development of modern quantum mechanics is attributed to Max Planck.
• The inverse square law states that intensity is inversely proportional to the square of the distance.
• A posteroanterior (PA) chest radiograph delivers approximately 100 μGy to the patient.

Miscellaneous

• Isomers are atoms that have different energy states or number of neutrons.
• Radioisotopes have unstable nuclei.
• White light refracted through a prism produces a spectrum of colors, with red having the longest wavelength.
• The energy of an electron is expressed in electron volts (eV).
• Kinetic energy (KE) is directly proportional to the square of velocity.Here are the study notes for the given text:
• X-ray Imaging*

X-ray Tube Components

• Filament transformer: a step-down transformer that supplies lower voltage to the filament
• Anode and cathode: the two principal parts of the x-ray tube
• Tungsten is the choice material for x-ray anodes because of its high atomic number and high melting point

X-ray Interactions

• Two common types of x-ray interactions: Compton scatter and photoelectric effect
• Compton scattering: results in a longer wavelength and lower energy x-ray
• Photoelectric effect: results in the complete absorption of the x-ray energy

X-ray Quantity and Quality

• X-ray quantity is inversely proportional to the square of the distance from the source (inverse square law)
• X-ray quality is principally a function of kVp
• Increasing kVp increases x-ray quantity and energy, and decreases the effect of filtration

Filtration

• Inherent filtration: present in the x-ray tube and is approximately 0.5 mm Al equivalent
• Added filtration: used to reduce the intensity of the x-ray beam and can be in the form of aluminum or copper filters
• Total filtration: the sum of inherent and added filtration

Digital Radiography (DR)

• Three main components of DR: coupling, collecting, and capturing the x-ray energy
• CCD (Charge-Coupled Device) is used for indirect conversion digital radiography
• a-Se (amorphous selenium) is used as an image receptor in direct radiography

Radiographic Technique

• The four prime factors of radiographic technique: kVp, mA, time, and SID
• Increasing kVp increases the x-ray energy and quantity, and decreases the effect of filtration
• AEC (Automatic Exposure Control) is used to terminate the x-ray exposure when the proper radiation exposure to the IR has been reached

Image Characteristics

• Contrast: the difference in brightness between two areas of the image
• Noise: random variations in the image brightness
• Spatial resolution: the sharpness of the image
• Artifacts: unwanted images or distortions on the radiograph

Let me know if you'd like me to continue with the rest of the questions!### Reducing OID

• To reduce OID, increase SSD or decrease SID.
• OID stands for Object to Image Distance.

Distortion of an X-ray Image

• Distortion of an x-ray image results from unequal exposure of the object.
• Other options that can cause distortion are:
  • Focal spot
  • Heel effect
  • Magnification
  • SID (Source to Image Distance)

Minimum Magnification

• To obtain minimum magnification, position the anatomy close to the image receptor.
• Other options that can help achieve minimum magnification are:
  • Making sure the object is positioned on the central axis
  • Selecting a short SSD (Source to Sensor Distance)
  • Using maximum collimation

Area Beam versus Scanned Projection Radiography

• The principal disadvantage of the use of an area beam versus scanned projection radiography is increased patient dose.

Direct Radiography

• An x-ray system used for direct radiography definitely has at least two video monitors.

Soft Tissue Contrast

• Soft tissue contrast is most important for contrast resolution.

Spatial Frequency

• Spatial frequency consists of units of line pair/millimeter.

Magnetic Resonance Imaging

• If the dynamic range of a magnetic resonance imaging system is 12 bits, there are 4096 shades of gray present.

Patient Radiation Dose

• Patient radiation dose should be lower when digital imaging is used than when screen-film imaging is used, principally because of detective quantum efficiency (DQE).

Technique Creep

• Technique creep is an attempt to reduce patient radiation dose by instituting increased detective quantum efficiency (DQE).

Image Distortion

• Image distortion occurs when there is a misalignment of the x-ray tube (i.e. angulation).

Radiographic Contrast

• Radiographic contrast can be increased by:
  • Increasing the kVp and decreasing the mAs
  • Positioning the object close to the image receptor
  • Using a faster image receptor
  • Using a high-ratio grid

Radiologic Technologist and Patient Scheduling

• The radiologic technologist is responsible for producing a quality medical image with attention to each of the following except image artifacts.

Image Quality Control

• Image quality control (QC) concentrated on wet chemistry and view boxes in the past, but today QC concentrates on digital display devices and ergonomics.

Digital Display Devices

• Digital display devices include:
  • LED monitors
  • LCD monitors
• Digital display devices have a low intrinsic noise, which results in a better SNR (Signal-to-Noise Ratio).
• Digital display devices are affected by ambient light, which can be evaluated by cycling the room lighting on and off.

Postprocessing

• Postprocessing the radiographic image includes all of the following except image inversion.
• Image inversion is when the image is opposite in color, e.g., bone appears black and soft tissue/contrast media appear white.

Radiologist Interpretation

• When a radiologist interprets an image to be abnormal and the image is later shown to be normal, that interpretation is labeled as a false positive.

Digital Image Illumination

• Digital image illumination is measured in lux or candelas per square meter.
• One lumen per square meter is equal to one lux.

Ergonomics

• Ergonomics requires the quality control (QC) technologist to have some metric data knowledge of:
  • Illumination
  • Noise
  • Temperature
  • Work schedule
  • Workstation

PACS (Picture Archiving and Communication System)

• PACS' primary use is to store digital images.
• PACS supports patient scheduling and digital image protocols.
• The four principal components of a PACS include:
  • Acquisition system
  • Display system
  • Storage system
  • Workstation

Medical Imaging

• Medical imaging programs support patient scheduling and digital image protocols.
• The fluoroscope was invented by Thomas Edison.

Eye Anatomy

• The retina is located in the eye.
• Rods are responsible for night vision, and cones are responsible for color vision and are concentrated at the center of the retina in an area called the fovea centralis.

Image Perception

• Higher object contrast is required for image perception under low illuminance.

Visualization

• The primary purpose of a fluoroscopic examination is to visualize dynamic images.

This quiz covers the basics of physics, including definitions of energy and radiation, and general knowledge of elements.