The Relationship Between Grey Levels And Hounsfield Units In Cone Beam CT ( CBCT ) Scanners

Digital radiography (DR) is a revolutionary invention in radiography. With this technology, no cassette is needed for an x-ray examination meaning that there is no need to reload films or to erase imaging plate in every examination. This is a distinctive feature which conventional radiography and computed radiography (CR) do not have. DR was first introduced in 1996 (Carroll, 2011). Miniature electronic x-ray detectors are used as the image receptor. The detectors enable the direct capture of the x-ray image without conversion steps (like the conversion of x-ray photos into light photons). This technology is widely used nowadays since it has many advantages and it brings much convenience to radiographers. One of the main advantages of DR is image post-processing in which the quality of the film (in terms of contrast and brightness, etc.) can be adjusted to reach the desired standard. Therefore, the tolerance of the deviation of the exposure factors is greater and the need of repeating the examination is greatly reduced so the patient dose is reduced. This follows the as low as reasonably achievable principle for radiation protection and this also improve the final image quality simultaneously. Besides, many DR systems were installed with preset for numerous anatomical studies which can improve the post processing. Like CR, the images produced are in digital format so this provides convenience for radiographers to store and retrieve the image easily. DR is also capable to work with PACS

A focus on the equipment is most important as it relates to the human-machine interaction (we learnt about this in the HCI project in class, as well as in lab). That is to say, the need is not necessarily for more powerful x-rays but rather x-ray imaging that facilitates screeners’

Using CT (Toshiba Scanner Activio, Toshiba) for measurement and analysis image using the processing software (OsiriX, Newton Graphics) for calculated splenic

The CT is also known as a CAT scan, and was first discovered in 1972. Godfrey Hounsfield, a British engineer, invented the CT along with help from Allan Cormack of South Africa. Hounsfield worked for EMI Laboratories in England, and Cormack was a physicist at Tufts University located in Massachusetts. The first CT was a full body machine and was available for us by the 1980’s. When the first CT’s were distributed, only about 6,000 of them were distributed in the United States, whereas 30,000 were distributed around the world. In the beginning, the CT machine delivers imagines that were not available before. However, they were not the best of quality, and took quite some time to gather. Now CT scanners can collect almost perfect images in seconds (“Brief history of CT”). In the end, the CT machine has come a long way, and is very beneficial for hospitals to

Computed Tomography is more commonly known as a CT scan. This medical instrument uses x-ray radiation, which “combines multiple x-ray images into a 3D model of a region of interest,” (Lucas 1). The various organs in the body absorb x-rays differently. A computer monitors the process of absorption with “30,000 x-ray beams,” (Timberlake 171), that is directed at the organ being scanned, such as, the brain. An x-ray wavelength has two different types, a soft and hard x-ray. A soft x-ray wavelength ranges between “3x10^16 hertz to about 10^18 hertz,” (Lucas 1). On the other hand, hard x-rays range between “10^18 hertz to higher then 10^20 hertz, with a wavelength from 100 pm to about 1 pm,” (Lucas 1). CT scans give doctors specific information about their patient.

Due to the various advancements of technologies in the field of radiography, sometimes it can be difficult to choose with imaging modality can be used to provided the best care for the patient and diagnose Clinicians must be aware of the potential benefits and drawbacks of each imaging modality to balance its use with healthcare costs, radiation dose to the patient, as well as patient safety.

Qu XM, Li G, Sanderink GC, Zhang ZY, Ma XC (2012). Dose reduction of cone beam CT

To review the principles of CT, first we need to know the physics basic of X-ray imaging. Attenuation, which is defined as the removal of X-ray photons from the beam, occurs in biologic

The computed tomography (CT) scan is a procedure that uses x-rays and digital technology to construct conception of the body. It can make a reflection of every part of the body, for example bone and blood vessels.CT scans are used to examine the inner structures of the body which cannot be seen by human eye.Examples are blood cots or tumors.CT scan can also be used to measure precisely the density of bone in assess osteoporosis.

Furthermore, the cost of Nuclear Imaging is relatively high and, as a result, is not being commonly installed in hospitals. The reason is the necessity of having the PET facility close to a cyclotron since the useful radioisotopes have small half-lives; thus the time between its production and the final injection must be small. In this way, the optimal use of high levels of radioactivity during the first few half-lives can be utilised to produce high-quality images (Andrew Olesnicky, Neville Lawrence,

CT scan is a computerized tomography, it is when slices of images are put together to make up a three-dimensional image of the body produced using an advanced x-ray. It is used to diagnose medical diseases. It has improved widely to provide comfort to patients as the scan can be done quickly. It displays high-resolution images assisting doctors to make diagnosis. For example, the CT scan can help doctors to visualize small nodules or tumors, which they cannot see with a plain film X-ray.

The first PET scanners were rather basic and had few radiation sensors, therefore images that were produced were of a very low quality. As the world’s technological understanding increased so did the machinery used in the PET scanners until they reached the accuracy of today’s scanners.

Since the evolution from conventional to digital radiography the radiation dose to patients have been significantly decreased.

The denser areas are shown as white while the soft areas appear dark in the film but sometimes some organs may block x-rays from showing broken or cracked bones and for this reason CAT (Computer Axial Tomography) was invented. Firstly, the person requiring the scan is put inside of a scanner, which is a long tube-shaped machine and then x-rayed from all angles, after a computer puts all of the images together so that doctors can analyse them. CAT are mainly used for head and brain injuries and appropriate shielded should be provided to cover the areas not being x-rayed.

X-Ray’s are used to generate pictures that show the inside of the human body such as finding broken bones. In Otto Zhou of the University of North Carolina, Dr Zhou and his colleagues are bringing X-radiography into the world of modern electronics. In doing so, there is a hope to create X-ray