What causes noise in CT?
The source of the electronic noise in CT is a combination of the noise of the detector system and the reconstruction kernel (sharper kernels give noisier images). Noise in a CT scan image can be decreased by increasing the mAs, by increasing the tube current or changing filters during reconstruction.
What is voxel in CT scan?
A voxel is the smallest 3D element of the volume,2 and is typically represented as a cube or a box, with height, width and depth.
What is CT pixel size?
found that the reconstructed slice thickness in computed tomography (CT) varied from 3 to 6 mm and that the pixel size varied from 0.59 to 0.94 mm [6, 7]. In another study of CT texture features in 39 patients with metastatic renal cell cancer, the pixel sizes ranged from 0.59 to 0.78 mm [8].
What is matrix image?
The image of a linear transformation or matrix is the span of the vectors of the linear transformation. (Think of it as what vectors you can get from applying the linear transformation or multiplying the matrix by a vector.) It can be written as Im(A).
What is statistical noise in CT?
The statistical noise in CT reconstructions is closely re- lated to the dose. The dose efficiency of a given scanner may be obtained by comparison of its delivered dose to that required by an ideal x-ray scanner to achieve the same NEQ.
How do you reduce CT noise?
Iterative reconstruction (IR) algorithms are the most widely used CT noise-reduction method to improve image quality and have greatly facilitated radiation dose reduction within the radiology community. Various IR methods have different strengths and limitations.
What is pixel and voxel in CT?
These images consist of pixels. Every pixel has certain dimensions (XY, where mostly X=Y) and a certain gray value that is related to the material it represents. The images are a certain distance apart (Z). This distance gives the pixels a certain depth; a VOlume piXEL is called a voxel.
What voxel means?
A voxel is a unit of graphic information that defines a point in three-dimensional space. Since a pixel (picture element) defines a point in two dimensional space with its X and Y coordinates , a third z coordinate is needed.
What is CT image quality?
CT image quality, as in most imaging, is described in terms of contrast, spatial resolution, image noise, and artifacts.
How many pixels are in a matrix?
The typical number of pixels in a matrix ranges from about 512 × 512 to 1024 × 1024 and can be as large as 2500 × 2500.
What is the matrix used for?
Matrices have wide applications in engineering, physics, economics, and statistics as well as in various branches of mathematics. Matrices also have important applications in computer graphics, where they have been used to represent rotations and other transformations of images.
What is CT collimation?
Abstract. Dynamic collimation is an important dose reduction mechanism for helical CT scans, especially for modern wide-beam scanner models. Its implementation and efficacy need to be studied to optimize CT scan protocols and to reduce unnecessary patient dose.
How do you evaluate noise in a CT image?
Noise in CT is measured via the signal to noise ratio (SNR); comparing the level of desired signal (photons) to the level of background noise (pixels deviating from normal). The higher the ratio, the less noise is present in the image.
What is image quality in CT?
Image quality can be defined in terms of physical, psychophysical and observer performance tests. Examples of physical measures are: uniformity, linearity and noise; while psychophysical tests include spatial resolution and contrast resolution. These are discussed with their relevance to CT image quality optimization.
Is a CT scan noisy?
CT scans utilize X-rays, which are radioactive, to capture individual image slices of the body. They are effective at making detailed images of the head, abdomen, chest, skeletal system, and more. CT scans are generally quieter and more comfortable for the patient, and faster than MRI scans.
What is difference between pixel and voxel?
Every pixel has certain dimensions (XY, where mostly X=Y) and a certain gray value that is related to the material it represents. The images are a certain distance apart (Z). This distance gives the pixels a certain depth; a VOlume piXEL is called a voxel. It has XYZ dimensions.