What is CT noise?
Noise in computed tomography is an unwanted change in pixel values in an otherwise homogeneous image. Often noise is defined loosely as the grainy appearance on cross-sectional imaging; more often than not, this is quantum mottle.
What is the matrix size in CT?
512 x 512
The typical CT image is composed of 512 rows, each of 512 pixels, i.e., a square matrix of 512 x 512 = 262,144 pixels (one for each voxel).
What is CT spatial resolution?
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 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).
How do you reduce noise in CT?
Noise reduction can occur at various stages of the CT imaging process. In conventional analytic filtered backprojection (FBP)–based reconstruction, a smooth filter is typically applied to control noise.
What affects noise CT?
CT image noise depends on number of x-ray photons contributing to image. (A and B) Comparison of noise from scans using 270 mAs (typical clinical value) and 100 mAs. (C) Appearance of image noise is strongly affected by reconstruction filter; sharp filter such as bone also sharpens (enhances) appearance of noise.
What is CT scan principle?
CT uses ionizing radiation, or x-rays, coupled with an electronic detector array to record a pattern of densities and create an image of a “slice” or “cut” of tissue. The x-ray beam rotates around the object within the scanner such that multiple x-ray projections pass through the object (Fig 1).
What improves spatial resolution?
Another way to enhance spatial resolution is to improve the sampling of detector units by deflecting the focal spot on the x-ray tube anode along longitudinal and fan angle direction (2–4).
What is effective slice thickness in CT?
An optimal slice thickness is therefore expected between 2.5 and 5 mm for lesions ~5 mm in diameter.
What does a 64 slice CT mean?
Washington Hospital’s Outpatient Imaging Center uses a state-of-the-art 64-slice computed tomography (CT) scanner. The Scanner creates 64 high-resolution anatomical images per rotation. This will decrease scan times to several seconds, less than 15 seconds in most cases.