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Describe the CT computer and image processing system.

The applications for 3D imaging are becoming more demanding. 3D imaging uses 3D surface and volumetric reconstruction. These algorithms are based on computer graphics and visual perception science. These techniques allow for the user to interactively visualize manipulate and measure the large 3D objects on the average work computer.

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Describe the image reconstruction in helical CT.

The two different types of Helical Ct scanners are single-slice spiral and multi-slice spiral. Just as stated earlier the algorithms mentioned are used in single-slice CT which is a back projection algorithm used because of the constant movement of the patient. Multi-slice and Single slice main difference are that multi-slice uses multiple detecter rows that cover more volume while moving faster meaning they require new algorithms. Multi-slice CT scanners allow for the reconstruction of variable slice thickness and address the problems of increased tissue volume and the speed of the gantry while the patients are inside.

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Discuss the concepts of Fourier transform, convolution, and interpolation

Fourier reconstruction is used in MRI but not in modern CT scanners because it requires more complicated mathematics. This concept does have many advantages such as smoothing or edge enhancement, the computer can perform the manipulations with digital processing and frequency information can be used to measure the image quality of the image through the point spread function line spread function, and modulation transfer function. Convolution data is used today with CT scanners which is a filtered back projection algorithm. This data is usually filtered and improved through the removal of a blur. Interpolation is crucial with SSCT because the image is retrieved through continuous movement int he gantry which would lead to a blurred image.

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Describe the image reconstruction algorithms

Image reconstruction algorithms from projections include many assorted algorithms These include back projection, iterative methods, and analytic methods. The first algorithm known as back projection is a simple procedure and is best explained as a graph or number approach. It is when four beams of x rays also known as projection profiles pass through an unknown object. These projected datasets are back-projected to form the corresponding image of the object. The second known algorithm is the iterative method which uses an assumption and compares the assumption with the measured values attained and makes corrections to match the two best as possible. Lastly, analytic methods were developed to overcome the shortcomings of the other two methods that were mentioned. Filtered back projection is a modern algorithm used in CT that removes the star-like blurring of an image.

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Describe the basic principles of image reconstruction.

For CT machines to reconstruct an image of a patient the x-ray tubes and detectors must rotate around the patient at least 180 degrees plus the fan beam angle. The standard of CT machines has changed in the past years, including dual-source ray tubes and detectors, meaning they only need to rotate 90 degrees to get a full data acquisition. Present-day CT scanners collect more attenuation data than the older CT scanners meaning the more data collected from the scanner the better the image quality and better overall diagnosis of the patient.

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1. Discuss rotating anode X-ray tubes

Rotating anode x ray tubes are. Pe made of Rhenium, Tungsten, and Molybdenum alloy. The rotation because of the material used can rotate at speeds of 3,600-10,000 evolutions per min. This helps produce heterogeneous beam of radiation from a larger diameter anode disk. With focal spot sizes to facilitate the spatial resolution requirements of the scanner.

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2. Discuss X-ray tube in Helical/spiral

The advancements for specific X ray tubes like Helical and spiral scanners have placed new demands and requirement needed to have them reach full potential. They must be able to sustain higher power levels, withstand additional heat gen, expand heat storage, Lastly, increase heat dissipation. Due to these new requirements advancements had to be changed on technical aspects of the tube design in order to sustain and deal with these matters. Such as tube envelope, cathode, and anode assembly.

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3. Discuss the tube envelope and anode assembly

It was only fitting to make technical changes to CT machines being powered and continually rotating longer. The main changes made were to the envelope and the anode. The envelope ensures there’s a secure vacuum that uses internal getters to remove air molecules to ensure less less electrical arcing from the tungsten deposits. The anode can be made of three different materials of the disks. Metal, brazed graphite, and chemical vapor deposition graphite. This design helps to provide smooth rotation of the disk. High speed anode rotation is 10,000 RPM are possible with increased frequency to the stator windings.

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4. Discuss filtration

Filtration I’m CT. Has numerous purposes such as removing long wavelengths in order to harden the beam. Filtration also shapes the energy of the radiation beam to produce more uniformity which hardens when X-rays pass through the filter and the object.