Intercepts the x-ray photons that are able to exit the patient (remnant radiation). Converts the energy of x-rays into an image.
Image receptor (IR)
Classes of Diagnostic Radiographic Imaging.
Film-screen Computed Radiography (CR) Digital Radiography (DR) Fluoroscopic imaging (NOTE: there are also cassette-based and cassette-less systems)
Requirements for x-ray production.
1. Vacuum inside x-ray tube 2. Source of electrons 3. Method to accelerate electrons to great speed 4. Method to stop electrons
Source of electrons.
1. Cathode 2. Filament (Within the cathode)
Method to accelerate electrons to great speed
Method to stop electrons
Classes of Radiation
Primary radiation Scatter radiation Absorbed radiation Remnant radiation
The radiation (beam of photons) before it interacts with a patient's body. (Leaves the tube)
Type of radiation that provides little diagnostic information to image. Detracts from image quality with the creation of 'fog'.
Radiation that does not exit the patient.
Radiation that exits the patient and creates an image in the IR. Creates chemical changes within the receptor that are invisible.
What is the reason an x-ray tube must have a vacuum?
The vacuum removes all of the air so gas molecules will not interfere with the production of x-rays
Loss of radiation energy as a result of passing through an absorbing material (body).
Degree of attenuation that occurs in radiopaque matter. (X-rays cannot pass through.)
Degree of attenuation that occurs in radiolucent matter.
Different materials absorb radiation energy differently based primarily upon density and atomic number.
Invisible image created after exposure but before processing. (It must be processed to convert it to a visible image)
Considered an analog type of imaging
photostimulable phosphor (PSP) technology or storage phosphor technology
Computed radiography (CR)
Two methods of digital image capture. Can be indirect or direct?
Digital radiography (DR)
Digital radiography key features.
Uses no cassettes Image is displayed in seconds Detectors can be direct or indirect Uses thin-film transistors (TFT) Image brightness is not the same as radiographic density and is not related to exposure
Type capture that x-ray photons are immediately converted into an electrical signal.
Type capture that x-ray photons are converted to light and then converted into an electronic signal.
Determines image quality in digital cassette-less systems. The more _________ the better the image.
How do Film-screen systems work?
Intensifying screens convert the X-ray energy to light, and light energy creates chemical changes in film.
Exposed X-ray film is chemically processed in a ________ _____________ automatic processor.
Exposure Index (EI)
A numeric representation of total x-ray exposure to the receptor. It is not an indicator of the patient's absorbed dose.
Prime technical exposure factors that a radiographer has direct control over.
Milliampere-second (mAs) Kilovoltage peak (kVp) Source-to-image distance (SID)
A proper balance between _____________ and __________ qualities is required for optimum image quality.
photographic and geometric
affecting the visibility of the image
The two primary image photographic quality factors:
IR exposure/Density Contrast
Contribute to image quality by affecting image resolution, size, and shape. Affect sharpness and accuracy of the image. Also known as recorded detail, sharpness of detail, and definition.
The overall darkness or blackness of an image as demonstrated on a polyester-based film media
What aspects primarily affects Image Receptor Exposure?
milliamperage (mA), exposure time (S), source-to-image distance (SID), kVp
Determines how many x-rays are produced by the x-ray tube. (It directly controls the quantity of x-ray photons produced)
quantity of x-ray production
What is the relationship between mAs and density?
Directly proportional If the mAs is doubled the density is doubled. If the mAs is halved the density is halved
_____________ is the electrical current passing through the xray tube
_____ is the duration of the exposure
S Can be expressed in decimals, fractions or milliseconds
mAs reciprocity law
Regardless of the mA and time combinations, the same mAs value will yield the same exposure
Measure of the electrical pressure forcing the current through the tube. It controls penetrating ability of the beam. (It affects the quality and quantity of x-ray photons produced)
X-ray beam is ______________ or _______________________.
poly-energetic or heterogeneous.
Higher kVp values _________ skin exposure to patients.
Increasing kVp ?% will double image receptor exposure
To maintain exposure, if increasing kVp by 15%, must ________ mAs
Used to reduce scatter. It intercepts a portion of the remnant radiation and improves image quality. Requires higher exposure technique when used.
Distance between point of x-ray emission in the x-ray tube (focal spot) and the IR. (It affects intensity of radiation that reaches the IR as well as the geometric properties of the image)
What law deals with distance and intensity?
Inverse Square Law
What is the formula for the Inverse Square Law?
What law deals with distance and mAs?
Direct Square Law
What is the formula for the Direct Square Law?
mAs1/mAs2 = D1²/D2²
Can improve image quality and reduce dose as well as control scatter
Two types of primary beam modification:
-Filtration -Beam limitation (collimation)
Beam modification that involves use of attenuating material (aluminum) and removes low energy x-ray photons to decrease patient exposure. The more __________ used, the less intense the beam.
Beam modification that decreases patient dose as well as improving image quality.
Beam limitation (collimation)
Factors affecting recorded detail
Motion Object unsharpness Focal spot size SID OID Material unsharpness Distortion
Most common cause of image unsharpness.
Motion distortion (Caused by voluntary and involuntary patient motion)
Loss in resolution caused by the inherent shape of the patient's anatomic structures relative to the divergence of the x-ray beam.
Optimum use of __________, __________, and __________ can lessen object unsharpness.
Focal point size OID SID (Increased SID makes image sharper)
The smaller the focal spot size, the __________ the detail.
Any misrepresentation of the true size or shape of the patient's anatomy.
Two types of distortion.
Size distortion is minimized by using _________ and __________.
Longer SIDs Minimum OIDs
Distortion controlled by alignment of central ray, patient's anatomy, and IR. It is also called 'true distortion'.
Accomplished by angling or rotating the patient relative to the central ray. Helps overcome superimposition of anatomic structures.
Overall darkness or blackness of an image. It is directly related to x-ray exposure hitting the IR.
Term used for the amount of absorbing material that will reduce the intensity of the x-ray beam to half its original value. It is a way to express x-ray beam quality.
_________________ is most popular filtration material.
_________ detect the remnant radiation from the patient and convert it into chemical or electrical changes that make up the latent image
Three types of image receptors
Film/screen systems -Close to obsolescence Storage phosphor technology (CR) Flat-panel detectors using thin-film-transistor (TFT) technology
Exposed IP in cassette is placed in a reader for electronic processing of the latent image into a manifest image displayed on a monitor. Ultimately creates a digital image through computer software
Exposure to plate is stored in ___________ _________ ________ that create electron "traps."
barium fluorohalide crystals
Underexposure will produce an image that is "grainy" or noisy due to _____________.
How does CR work?
-Cassette with IP placed in CR reader -Reader scans the IP with laser energy and recovers the energy from the electron traps -Energy converts into manifest image
__________ detector uses cesium iodide as a scintillator with amorphous silicon.
Digital Cassetteless Systems use ____________ arranged in a matrix
How does Indirect Detector Technology work?
-Uses a scintillator material bonded to amorphous silicon -Scintillator receives the X-ray energy and converts it to light energy. -Light energy is captured by amorphous silicon and converted to electrons. -Electrons are collected by TFT and sent to computer.
uses amorphous silicon (aSi)
Digital detectors possess ___________ exposure latitude than conventional film-screen systems.
DR systems can be operated at varying system sensitivities, known as ___________ _________.
How does Direct Detector Technology work?
.-Uses amorphous selenium as the active detector material -Uses TFT to capture electrons from X-ray interactions -TFT collects and amplifies the electron signal. -Electron signals are converted to computer data and displayed as an image.
uses amorphous selenium (aSe)
controls image brightness.
Window width (WW)
During __________, x-ray exposures are much less than radiographic exposures. Use of x-rays to create real-time images of patient anatomy and function Images taken are digital images and can be played back for review or sent to an archival system for long term storage (PACs)