What is CT image reconstruction?

What is CT image reconstruction?

Image reconstruction in CT is a mathematical process that generates tomographic images from X-ray projection data acquired at many different angles around the patient. Image reconstruction has fundamental impacts on image quality and therefore on radiation dose.

How does iterative reconstruction work?

Iterative reconstruction is an algorithmic method that uses statistical and geometric models to variably weight the image data in a process that can be solved iteratively to independently reduce noise and preserve resolution and image quality.

What is a sinogram image?

All projection images are stacked and the 1D projections (or, simply, projections) that belong to the same slice (those between the vertical dotted lines) are grouped into a sinogram. This process is repeated for every slice. Therefore, there will be as many sinograms as slices. Source publication.

What is the difference between SFOV and DFOV?

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. High contrast resolution: The ability to distinguish sharp edges between small objects that differ greatly in density.

What is 3D reconstruction for CT?

Three dimensional CT (3D CT) is essentially a method of surface rendition of anatomy by means of a special computer software. The software is available in modern CT scanners as an optional package, or may be available as an auxiliary unit to be used in tandem with an existing scanner [1].

What is iterative reconstruction in CT scan?

Iterative reconstruction refers to an image reconstruction algorithm used in CT that begins with an image assumption, and compares it to real time measured values while making constant adjustments until the two are in agreement.

What is filtered back projection vs iterative reconstruction?

Low-dose head CT protocols using filtered back-projection are susceptible to increased noise and decreased image quality. Iterative reconstruction noise suppression allows the use of lower-dose techniques with maintained image quality.

What is a sinogram image reconstruction?

A sinogram acquired using projection imaging (forward projection) may be used to reconstruct an image of the original object through a process called backprojection. Information acquired at each projection angle is spread out along the path of that projection.

What is sinogram procedure?

A fistulogram or sinogram is an x-ray procedure to view an abnormal passage (fistula/sinus) between two or more organs. It may include a passage from inside the body to an opening on the skin. Contrast (once called x-ray dye) is used to identify the start of the fistula/sinus, its pathway and what organs are involved.

Why is back projection blurry?

The backprojection method has several drawbacks: First, it produces an image which has a high density in the center. This is due to the fact that many different images are being overlapped in this area. Secondly, the resulting image is severely blurred, as shown in the figures below.

What is forward projection in CT?

The forward projection (FP) operation is the mathematical model of the physical data acquisition process in computed tomography and tomosynthesis. The backprojection (BP) operation is the corresponding reverse model. The forward- and backprojection pair is a key module in reconstruction algorithms.

How is DFOV calculated in CT?

The formula for DFOV is pixel dimension x the matrix size. 320 x . 75 mm = 240mm or 24 cm DFOV.

What is window in CT?

Windowing, also known as grey-level mapping, contrast stretching, histogram modification or contrast enhancement is the process in which the CT image greyscale component of an image is manipulated via the CT numbers; doing this will change the appearance of the picture to highlight particular structures.

What are the limitations of 3-D reconstructions?

A potential limitation of MDCT and 3D reconstruction, is their inability to provide a surgical roadmap of biliary anatomy and anomalous anatomy in both the donor and recipient. Failure to appreciate anomalous biliary anatomy can lead to graft failure and post-procedure bile leakage.

What determines slice thickness in CT?

Slice thickness is determined by the detector width and pitch, while reconstruction interval can be chosen arbitrarily. The narrower the reconstruction interval, the better 3-D reconstructions.

What is CT iterative reconstruction?

What is the advantage of filtered back projection?

FBP has the advantages that computational time is less, the amplitude scale is linear, and there is less noise superimposed on peaks in images. It is useful to reconstruct images by both methods and compare results.

How does a sinogram work?

In CT and SPECT imaging, a sinogram is generated by rotating detectors around a patient, and storing the detected projection profiles at each angle in the sinogram, as depicted in the gif above.