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 (K _IND )

_______ 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 (K _STD )

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

It is 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

Is 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)

Refers to 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

Each square in a matrix is called a

picture element (Pixel)

The size of the pixel is determined by the:

matrix

Which of the following statements is not true?

A. Exposure index refers to the amount of exposure to the patient.

B. Exposure index refers to the amount of exposure to the image receptor.

C. Exposure is not uniformly represented across manufacturers.

D. Exposure index standardization is beneficial to the technologist

A. Exposure index refers to the amount of exposure to the patient.

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

actual exposure (K_IND); target exposure (K_TGT)

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

Brightness

“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

1.0 or 100%

The more light spread, the ______ the MTF.

lower

True or False Air kerma is the measurement of radiation energy absorbed in a unit of air

True

True or False The reflection of ambient light can be problematic with monochromatic monitors.

True

True or False MTF is a way to quantify the contribution of each system component and the component’s overall efficiency

False; to the overall efficiency of the entire system, not just individual components.

True or False It is possible to achieve an MTF of 100%.

False; an MTF of 100% indicates perfect imaging performance, which is unattainable in practice.

True or False In medical imaging there are 3 types of images: analog, digital, and computed.

False; there are two main types of images: analog and digital

True or False The size of the pixel is directly related to the amount of spatial resolution or detail in the image.

True

True or False A perfect image according to the deviation index has a DI value of 1.0.

True

True or False Systems with higher quantum efficiency can produce higher-quality images at lower doses.

True

True or False You may rely on the DI as the sole determining factor of image quality

False

True or Flase The exposure index refers to the amount of exposure received by the patient.

False; received by the IR not the patient

True or False Each body part and view has its own unique optimal exposure.

True

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

spatial resolution

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

radiographic

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

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

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

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

the bit depth

________ detectors have the highest DQE.

Amorphous selenium