Digital Imaging and Radiography

These flashcards cover key concepts related to digital imaging and radiography, including systems, components, processes, and diagnostic efficiency.

What are the two categories of digital receptors?

Digital radiography and computed radiography.

What do computed radiography systems use to store energy?

Storage phosphorus.

What method do digital radiography systems use to read out electronic systems?

Direct and indirect.

What is inside the cassette of a CR system?

Photo stimulable phosphor plate (PSP).

What are the parts of a CR system?

Cassette, plate reader, PSP plate, computer workplace.

What is the container for the PSP plate called?

The cassette.

What is the image receptor of a CR system called?

The photo stimulable phosphor plate.

What is the phosphor layer of the PSP plate made with?

Barium fluorohalide with europium.

What are the two layers of phosphor layers?

Turbid and structured phosphor layers.

What is the difference between a turbid and structured phosphor layer?

Turbid has random distribution of phosphor crystals, structured has columnar phosphor crystals.

What is considered the heart of the PSP plate?

The phosphor layer.

What are the layers of the PSP plate from top to bottom?

Protective layer, phosphor layer, reflective layer, conductive layer, support layer.

Where does the reflective layer in a PSP plate reflect light to during the process?

Toward the photo detector.

What does the conductive layer of a PSP plate do?

It conducts away static.

What does the support layer of a PSP plate do?

Gives the plate rigidity.

What happens to electrons in a PSP plate?

Some electrons leave phosphor atoms; about 50% become trapped in the conduction band of the phosphor layer.

What do the electrons within the conduction band do?

They create a latent image.

The energy of trapped electrons is released in a process called?

Photo stimulable luminescence.

What is used to collect released light from the PSP plate during scanning?

Photo detector.

What replaces the Bucky assembly in a DR system?

Detector array.

What is needed to read the light from a PSP plate?

The amplified signal is sent to an analog to digital converter.

What are the two forms of indirect capture in DR?

Charge couple device or complementary metal oxide, semiconductor scintillator plus optics; scintillator plus photos detectors plus thin film transistor (TFT).

What is a material that absorbs x-ray energy and emits visible light in response?

A scintillator.

What is a light-sensitive device that can respond to very low light intensities?

A charged couple device.

What is the process in which several CCD detectors create one large one?

Tiling.

What are scintillators made of crystalline silicone matrix called?

Complementary metal oxide semiconductors (CMOS).

What are complementary metal oxide semiconductors compared to?

Charge couple device.

What type of scintillator is made of a crystalline silicone matrix?

CMOS.

What is the problem with indirect capture methods?

There is an extra step in the conversion of x-rays into light, causing a drop in resolution.

What do direct capture methods use instead of scintillator?

Photo conductors and a thin film transistor array.

What are photoconductors made of?

Amorphous selenium.

What kind of system allows for the capture of image forming radiation transferred to a computer from a detector array for almost instant viewing?

Direct radiography systems.

What are the layers of direct capture flat panel detectors from top to bottom?

Bias electrode, amorphous selenium, TFT connect storage capacitors.

What happens before exposure with the direct capture system?

An electric field is applied through the bias electrode across the surface of the amorphous selenium layer.

When the computer processes exposure and incidents of a pixel for each exposure level, what is it called?

Histogram analysis.

What happens when the software selects stored histogram data sets to display in the image?

Values of interest (VOI).

What causes histogram errors?

Computer cannot identify at least three edges of calculation on the exposure, including raw exposure and scatter outside the field.

What is the scanning area speed of the CR PSP plate called when it is removed from the cassette?

Slow scan.

What is the scanning movement of the laser on the CR PSP plate that releases trapped electrons?

Fast scan.

What happens after electrons return back to their shells during a PSP reading?

The electrons release light which goes to the photo detector.

What happens after the light reaches the photo detector during PSP plate processing?

It is converted to an analog signal, passed through an ADC and made into digital pixels and image.

What is the frequency at which data is recorded from the detector called?

Sampling frequency.

How do digital detectors sample the x-ray exposure?

Sampling pitch.

What is the number of shades of gray that can be displayed within one pixel called?

Bit depth.

What is the maximum bit depth a CR or DR system can have?

2^14 or 16,384 shades of gray.

How does the indirect form of capture work with a CCD?

X-rays absorbed by scintillator > light transmitted to CCD > electronic analog signal > ADC > digitized into an image.

How does the indirect form of capture work with a CMOS?

X-rays absorbed by scintillator > goes to CMOS > converted to light that is sent to photo detector > electronic analog signal > collected by DELS > ADC > digitized into an image.

How does the direct form of capture work?

Electric field is applied via electrodes across the surface > x-rays absorbed by amorphous selenium > electric charge stored in capacitors connected to TFTs > converted to digital code > ADC > digital image.

What does exposure latitude represent?

The digital receptor’s ability to record a wide range of exposure values.

What is the range of exposure in intensities that an image receptor can respond to and used to acquire image data called?

Dynamic range.

What is a problem with post processing?

Doing too much post processing can negatively affect the data set of the image.

What material does the CCD method of indirect capture use within the scintillator?

Cesium iodide phosphor.

What material does the CMOS method of indirect capture have in the scintillator?

Crystalline silicone.

What happens when increasing the window width?

Increases the number of shades of gray.

What happens when decreasing the window width?

Decreases the number of shades of gray.

What happens to contrast after decreasing window width?

High contrast occurs.

Why is it important for the exposure indicator to show exposure within an acceptable range?

Ensures post-processing can be done without compromising the image data.

What do DR systems use as an exposure indicator?

Dose area product (DAP).

What does the dose area product number reflect?

Both the dose to the patient and the total volume of tissue being irradiated.

What does DQE stand for?

Detective Quantum Efficiency.

What is true about DQE conversion efficiency?

No imaging system has a DQE of 100%, meaning it can’t capture all exposure.

How does DQE affect patient dose?

Higher DQE means lower patient dose.

What problem can happen if DQE is too high?

The image receptor might not get enough exposure, resulting in grains or noise.

What is the Nyquist frequency?

The highest spatial frequency (number of line pairs per millimeter) a digital detector can record.

What is special resolution equal to?

1/2 the Nyquist frequency of the system.

What are electronic components layered onto a glass substrate that include readout, charge collector, and light-sensitive materials?

TFT - thin film transistor.

What material is a CCD made of in the scintillator?

Cesium iodide phosphor.

What material is CMOS made of in the scintillator?

Crystalline silicone.

What is limiting spatial resolution?

The ability of a detector to resolve small structures, measured using a bar pattern.

What are the two measures of spatial resolution?

Modulation transfer function (MTF) and limiting spatial resolution (LSR).

What are histograms of luminescence values used for?

As a reference to evaluate the input intensities and assign predetermined grayscale values.

What is the daily assessment for digital imaging quality control?

The TG18-QC test that looks at general image quality and presence of any image artifacts.

What is involved in the monthly/quarterly assessment for digital imaging quality control?

Geometric distortion, luminance response, luminance dependencies, and resolution assessment.

How often should CR plates be cleaned?

Every three months.

When should CR plates be erased?

Every 48 hours.

What kind of grid is recommended for digital systems?

High frequency grid.

What are the parts of the Picture Archiving and Communication System (PACS)?

Acquisition, a secure network for exchanging patient images, storage/archive server.

What is the average size for a digital radiography study?

38 MB.

What is a common language for different PACS systems to communicate?

The digital imaging and communications in medicine (DICOM).

When was the digital imaging and communications in medicine established?

1983.

What allows image files to be accessed from various workstations throughout the facility?

Teleradiology.

What size monitor is appropriate for non-interpreting physicians to look at images?

One megapixel (Mp).

What size monitor is appropriate for interpreting physicians?

One megapixel (Mp).

What allows for advanced manipulation of medical images?

Quality control display station.

Do you have access to different functions for changing a medical image?

No, access may be protected to avoid damaging the image.

What scintillator is used in indirect receptors that don’t use CCD or CMOS?

Cesium iodide or gadolinium oxysulfide.

What are the photo detectors in indirect receptors made of?

Amorphous silicone photodiode.

What allows for images and data from different systems to be stored on a common infrastructure?

Vendor neutral archive (VNA).

What does HIPAA require regarding clinic image data storage?

Maintain storage of image data for years.

What is a recent trend for PACS storage?

Using a cloud-based system.

What are the basic archiving components of PACS?

Image manager and image storage.

What is the storage medium for image storage?

Optical disc or flash drive.

What are the classifications of PACS?

Online, nearline, and offline.

How is online storage connected to the PACS?

Direct attached storage or network attached storage.

What is the oldest storage technology?

Magnetic tape.

What storage technology has a reflective surface?

Optical disc/compact disc.

What storage technology uses ferromagnetic material bonded to plastic?

Magnetic tape.

What storage technology uses a photosensitive layer burned by light from a laser?

Optical disc/compact disc.

What is a newer way of compressing data without loss with an array?

High capacity flash drive arrays (73-146 GB).

What is a newer way of storing compressed data that can hold up to one TB?

Holographic storage device with laser technology.