How is image quality measured in CT?

Fundamentally, image quality in CT, as in all medical imaging, depends on 4 basic factors: image contrast, spatial resolution, image noise, and artifacts. Depending on the diagnostic task, these factors interact to determine sensitivity (the ability to perceive low-contrast structures) and the visibility of details.

What is CT performance parameters?

There are five important performance parameters which are to be measured: Noise, Contrast scale, Nominal tomographic section thickness, High and Low contrast resolution (MTF). The sixth parameter is, of course the dose per scan and slice which gives the patient dose for the certain diagnostic procedure.

What is the resolution of CT scan?

Current CT scanners have a spatial resolution of 0.5–0.625 mm in the z-axis, and approximately 0.5 mm in the x- to y-axes. A basic requirement for adequate multiplanar reconstruction is that the resolution is isotropic; eg, the resolution is approximately equal in all directions.

What is LP cm?

Resolution is measured in line pairs per centimeter (lp/cm) i.e. the number of line pairs that can be imaged as separate structures within one centimeter. Types of resolution.

How is image quality measured?

Measure Of Image Quality Resolution is determined by the ratio of pixels in proportion to image size. This is measured in PPI (Pixels Per Inch). A high resolution image will usually have more pixels to every square inch in an image.

How do you measure pixels in Connecticut?

The pixel size can be calculated by dividing the DFOV in mm by 512 (the matrix). The depth the pixel represents is determined by the slice thickness.

What is pitch in CT?

The term detector pitch is used and is defined as table distance traveled in one 360° gantry rotation divided by beam collimation 2. For example, if the table traveled 5 mm in one rotation and the beam collimation was 5 mm then pitch equals 5 mm / 5 mm = 1.0.

What is slice thickness in CT?

Slice thickness and slice increment are central concepts that surround CT/MRI imaging. Slice thickness refers to the (often axial) resolution of the scan (2 mm in the illustration). Slice Increment refers to the movement of the table/scanner for scanning the next slice (varying from 1 mm to 4 mm in the illustration).

What is the resolution of an MRI scan?

Nowadays, most MRI scanners used for medical purposes have B0 values of 1.5 or 3 T and can reach typical resolutions of around 1.5×1.5×4 mm3.

What is high resolution CT scan used for?

High-resolution CT technology uses a narrow X-ray beam and advanced computer analysis to create very detailed pictures of your body, allowing physicians to see small details that would not be possible with an older, tradiational CT.

What does low temporal resolution mean?

It also means that at the end of the experiment we will only have a relatively few number of volumes. For example, if you scan a person for 5 minutes, you will get less than 300 time points. Low sensitivity can be compensated by long monitoring (data acquisition) times, but that reduces the temporal resolution.

What is high contrast resolution?

High-contrast resolution is the ability to detect finely spaced lines or holes with whose signals differ considerably from background. Low-contrast resolution is the ability to detect and discern objects with only subtle differences in signal intensity.

How are image quality metrics used in CT?

When CT images are reconstructed using the standard filtered back-projection (FBP), these methods are commonly used to characterise a CT unit. The objective image quality metrics assess separate aspects of the features of the image, and therefore need to be combined to give an overall representation of the image quality.

How is the quality of a CT scan determined?

-The total x-ray beam exposure in CT is dependent on a combination of mA setting, scan time, and kVp setting. mA and scan time together are referred to as mAs and defines the quantity of the x-ray energy. kVp setting defines the quality (average energy) of the x-ray beam. 3.

How does radiation dose affect CT image quality?

• The Uncoupling Effect – The relationship between radiation dose and CT image quality is complex not like FSC (↑kVp+↑mAs→↑Pt dose” over-exposed”). – The uncoupling effect does not play a role when the mA or kVp setting is too low,because quantum noise will result and provide evidence of the inadequate exposure settings.

Why is image quality important in computed tomography?

Evaluation of image quality (IQ) in Computed Tomography (CT) is important to ensure that diagnostic questions are correctly answered, whilst keeping radiation dose to the patient as low as is reasonably possible. The assessment of individual aspects of IQ is already a key component of routine quality control of medical x-ray devices.