Chapter 2: Digital Imaging Characteristics

What is the difference between the

actual exposure (K _IND ) and the target

exposure (K _TGT ), except that it is

represented in a logarithmic fashion?

Deviation Index (DI)

Also known as a picture element, it is the smallest element in a digital image.

Pixel

Refers to a device or system that captures or measures a continuously changing signal

Analog

Anything that interferes with the formation of an image is called:

Noise

The measurement of the radiation that was the incident exposure on the imaging plate (IR) for that particular exposure is called:

Indicated equivalent air Kerma

_______ are recorded as multiple numeric values and are divided into an array of small elements that can be processed in many different ways.

Digital Images

Each pixel contains bits of information. The number of bits within a pixel is known as:

Bit depth

When determining the appropriate exposure techniques used for a particular body part, the radiologist and technologist must decide how much noise can be tolerated on an image. This is known as _____.

Signal-to-noise ratio

The ability of the imaging system to demonstrate small details of an object is called:

spatial resolution

What is the measurement of radiation

energy (joules or J) absorbed in a unit

of air (kG)?

Air Kerma

This is used to place a relative value on noise. It describes the spatial frequency content of the noise, and its spatial characteristics.

Noise power spectrum (NPS)

How efficiently a system converts the x-ray input signal into a useful output image is called:

Detective quantum efficiency (DQE)

what is the measurement for a standard exposure typical of that imaging receptor system?

The standardized radiation

exposure

Refers to the appearance of the digital image on the display monitor of the computer and is a function on a monitor’s ability to emit light through the surface of the display:

Brightness

What is the square arrangement of numbers (pixel values) in columns and rows?

Matrix

The abruptness with which the edges of bone or soft tissue transitions to an adjacent tissue or background density:

Sharpness

The ability of the entire system to respond to varying levels of exposure is:

Dynamic range

A set of values , established by either the system manufacturer or the system user, that represents an optimal exposure for each specific body part and view

Target equivalent air Kerma value

What is the amount of body part or patient included in the image called? it is synonymous with the x-ray field.

Field of view

Refers to the ability of the digital system to display subtle changes in the shade of gray

Contrast resolution

The ability of a system to record available spatial frequencies is:

Modulation transfer function (MTF)

The range of exposure diagnostic image values the image detector is able to produce

Latitude

Multiple numeric values divided into an array of small elements capable of being processed is the definition of _____ images

Digital

The continuous and varying levels of brightness and colors describe _____ images.

Analog

Each square in a matrix is called a:

Picture element (Pixel)

The size of the pixel is determined by the:

Matrix

If a pixel has a bit depth of 8, the number of gray tones that pixel can produce is

256

The measurement for radiation that was incident on the image receptor for a particular exposure is known as:

KIND

Deviation index is the difference between _____ and _____ expressed in logarithmic fashion.

KIND;KTGT

How dark or light a digital image appears on a display monitor is known as:

Brightness

The ability of a digital system to display subtle changes in shades of gray is called:

Contrast resolution

The ability of an imaging system to demonstrate small details of an object is known as:

Spatial resolution

A system’s ability to respond to varying levels of exposure, resulting in more detail, is referred to as:

Dynamic range

“The sum of the components in a recording system cannot be greater than the system as a whole” is a definition of:

modulation transfer function (MTF)

A perfect image processing system would have an MTF of:

100%

The more light spread, the ______ the MTF.

lower

The range of exposure values the image detector is able to produce is known as:

Latitude

The efficiency of a system to convert the x-ray input signal into a useful output image is known as:

Detective quantum efficiency (DQE)

A ________________, or picture element, is the smallest element in a digital image.

pixel

To ______________ gain or loss of resolution, a mathematical theorem was developed that stated that spatial resolution can be broken down into individual components and that the _______________ of each component affects the total amount of resolution

quantify; quality

The size of the pixel is directly related to the amount of ____________________ or detail in the image.

spatial resolution

In an analog system such as _______, x-ray energy is converted into light, and the light waves are recorded just as they are. In _______ analog signals are converted into numbers that are recorded

film/screen radiography; digital radiography

The ability of a system to record available spatial ______ is known as modulation transfer function (MTF). The ______ of the components in a recording system cannot be greater than the system as a whole

frequencies; sum

Noise that occurs during the acquisition of the image is known as _______ noise.

radiographic

Each pixel contains pieces or ________ of information. The number of _______ within the pixel is known as _______ bit depth

bits; bits; pixel

The size of the matrix determines the size of the _____.

pixels

If superimposition of body parts occurs, this is known as _____ noise.

anatomical

Spatial resolution comes down to this: the _________ the pixels, the ________ the spatial resolution

smaller; greater

Both in _________ and _________, anything that interferes with the formation of an image is considered noise

film/screen; digital

As SNR ________, the noise decreases, but at a cost of higher exposure to the ________.

increases; patient

The critical qualities of a digital image are separated into two categories known as signal image and final displayed image. The primary influences on the signal image are ________ (mAs), subject contrast (kVp) noise, sharpness (focal spot), geometric magnification(SID/SOD, ration of SID to SOD) and shape distortion (alignment).

receptor exposure

When determining the appropriate exposure techniques to use for a particular body part, the radiologist and technologist must decide how much _________ can be tolerated in the image.

noise

Latitude is dependent on the image ________; the higher the dynamic range of the ________, the more values can be detected.

detector; detector

Systems with higher quantum efficiency can produce higher-quality images at ________ doses.

lower

Amorphous selenium, amorphous silicon TFT, CCD, and CMOS detector technology have increased _________ over PSP.

detective quantum efficiency

Any interruption of the image signal by the patient or the equipment will be known as _________.

noise

_________ phosphor layers and smaller pixels produce images with higher resolution

thin

How efficiently a system converts the x-ray input signal into a useful _________ image is known as detective __________ efficiency

output; quantum

Contrast resolution in digital imaging is directly related to ________ of the pixels in the image.

bit depth

Whereas the ratio of SID to OID will cause ________ of the part imaged, digital systems allow the operator to selectively magnify an area or anatomy or to _______ the entire mage without significant loss of resolution

magnification; zoom

Contrast resolution in digital imaging is affected by the amount of ________ caused during the image production process. Digital systems are much more ________ in recording scatter

scatter; sensitive

The ________ can be used to adjust technical factors if the image must be repeated. A perfect image according to the deviation index has a _______ value of zero (0.0). if the DI is _________, the image has been underexposed. If the DI is _______ the image has been overexposed

DI; DI; negative; positive

________ detectors have the highest DQE.

Amorphous selenium