Contents
What is projection in tomography?
Optical projection tomography is a form of tomography involving optical microscopy. It is in many ways the optical equivalent of X-ray computed tomography or the medical CT scan. OPT differs in the way that it often uses ultraviolet, visible, and near-infrared photons as opposed to X-ray photons.
What is a Sinogram in CT?
A sinogram is a special x-ray procedure that is done to visualize any abnormal opening (sinus) in the body, following the injection of contrast media (x-ray dye) into the opening.
How is a sinogram formed?
Any number of projection images can be generated given an image slice; these projection images differing in the angle of projection. The projection images are generated through a mathematical entity called the Radon Transform. This article is about the use of Radon Transforms to generate the Sinogram of an image.
How many projections are in a CT scan?
Field of View. CT images are reconstructed from approximately 1000 projections that are acquired as the x-ray tube rotates through 360º around the object (patient).
What is the reconstruction method used in CT?
The most commonly used analytical reconstruction methods on commercial CT scanners are all in the form of filtered backprojection (FBP), which uses a 1D filter on the projection data before backprojecting (2D or 3D) the data onto the image space.
What is meant by sinogram?
A sinogram is a similar procedure done to assess a sinus, an abnormal passage or cavity that originates or ends in one opening, often on the skin. Contrast material is used to help identify the start of the fistula/sinus, its pathway and what organs are involved. top of page.
What is a sinogram PET?
Comparing the raw data acquired in PET to that in SPECT, each projection image in SPECT represents the data acquired at that projection angle across all slices, whereas in PET each sinogram represents the data acquired for that slice across all projection angles.
What is FOV CT?
DFOV: Display field of view– determines how much of the scan field of view is reconstructed into an image. DFOV can be less than or equal to the SFOV but cannot be more than the SFOV.
What is back projection in psychology?
noun. a method of projecting pictures onto a translucent screen so that they are viewed from the opposite side, used esp in films to create the illusion that the actors in the foreground are moving. Also called: background projection.
How are the different types of reconstruction algorithms different?
Reconstruction algorithms use the raw data to determine attenuation values for each voxel; differences between reconstruction techniques involve determining how this attenuation value is assigned in the final image. There are two major classes of reconstruction algorithms: analytical and iterative.
How is iterative reconstruction used in CT imaging?
Owing to recent advances in computing power, iterative reconstruction (IR) algorithms have become a clinically viable option in computed tomographic (CT) imaging. Substantial evidence is accumulating about the advantages of IR algorithms over established analytical methods, such as filtered back projection.
When was IR first used for CT reconstruction?
IR approaches are not new and were, in fact, the initially proposed method for data reconstruction in the early days of CT technology during the 1970s ( 2 ). However, due to its mathematically demanding properties and the large amount of data in CT imaging, until recently IR has not been practical for clinical purposes.
Why are reconstruction techniques used in nuclear medicine?
Instead, this reconstruction technique became the default method for nuclear medicine emission tomography imaging modalities with lower spatial and temporal resolution, such as single photon emission CT and positron emission tomography, because of the smaller data volumes and less complex data handling ( 12 ).