CT scan
CT scan formerly called computed axial tomography scan or CAT scan is a medical imaging scan technique used to obtain detailed internal images of the body. Personnel who perform CT scans are radiographers or radiology technologists.
CT scanners measure the X-ray attenuations of different tissues by placing a row of detectors inside a rotating gantry containing an X-ray tube. The multiple X-ray measurements taken from varied angles are computed with a computer running tomographic reconstruction algorithms to produce computer-generated tomographic cross-sectional images of virtual slices of a body. CT scans can be performed on patients with metallic implants or pacemakers for whom MRI is contraindicated.
Since its development in the 1970s, CT scanning has been an excellent imaging method. While CT is mostly applied in the medical field for diagnostic purposes, CT scan, MRI, ECO, Ultra sound, X-ray. it can also be applied to produce images of non-living objects. In 1979, Allan MacLeod Cormack and Godfrey Hounsfield shared the Nobel Prize in Physiology or Medicine for the development of computer-assisted tomography.
Types of CT scan
Sequential CT
Sequential CT scan , also known as step-and-shoot CT, is one of the scanning techniques in which the CT table moves stepwise. The table increments to a particular location and then stops which is followed by the X-ray tube rotation and the taking of one slice. The table increments again and so takes another slice. The table does not move during the collection of slices. This leads to an increased scan time.
Spiral CT
CT scanning of the thorax. The right axial slice is the image that corresponds to the number 2 33 on the left coronal slice. Spinning tube, which is generally referred to as spiral computer tomography or helical CT, refers to an imaging technique in which the whole X-ray tube is spun around the central axis of the area being scanned. These are the most common type of scanners because they have been in production the longest, which means there is a lower cost of production and purchase
. The biggest limitation of this type of CT scan is the bulk and inertia of the equipment X-ray tube assembly and detector array on the other side of the circle, which limits how fast the equipment can spin. Some designs use two X-ray sources and offset detector arrays by an angle, as a means of increasing temporal resolution.
Electron beam tomography
Electron beam tomography EBT is one form of CT scan where a large enough X-ray tube is constructed so that only the path of the electrons traveling between the cathode and anode of the X-ray tube is spun using deflection coils. This design had a significant advantage as sweep speeds can be significantly faster, allowing less blurry imaging of moving structures such as the heart and arteries. Fewer scanners of this design have been produced compared with spinning tube types this is primarily due to the increased cost of building a much larger X-ray tube detector array and limited anatomical coverage.
Dual Energy CT
Dual Energy CT, also known as Spectral CT is the advanced version of Computed Tomography. The dual energies here generate two sets of data. A Dual Energy CT could use a Dual source, a Single source with a dual detector layer, and a single source with energy switching methods to achieve two different sets of data.
The current single-tube CT scan is highly replaced by modern advanced scanners known as dual-source CT that contain a two X-ray tube detector system. These two detector systems are mounted on a single gantry and are placed at 90° in the same plane. Dual Source CT scanners allow fast scanning with a higher temporal resolution by acquiring a whole CT slice in only half a rotation.
Fast imaging reduces motion blurring at higher heart rates and may offer a shorter breath-hold time. This may be helpful for patients who have poor conditions, such as finding it difficult to hold their breaths or are unable to take medications to lower their heart rate. Another mode of Dual-energy CT is Single Source with Energy switching where a single tube is operated at two different energies through frequent changing of the energies.
CT scan use in Medical
Since its development in the early 1970s, CT scan has become an indispensable modality in medical imaging that, along with conventional X-ray imaging and medical ultrasonography, makes up the backbone of diagnostic techniques applied today. It also acquired high usage in preventive medicine or as a means of screening for the disease, such as computer tomography colonography in individuals at high risk of colon cancer or full-motion heart scans of individuals having a high risk of heart disease. Many organizations have been offering whole-body scanning to the public although this practice goes against the advice and official position of most professional bodies in the industry primarily because of the radiation exposure.
Other uses of CT scan
Industrial use
Industrial CT scanning industrial computed tomography is a technique that utilizes X-ray technology to create 3D images of components both internally and externally. Industrial CT scan have been used in several industrial fields for inspecting the internals of components. Some of the important applications for CT scanning are flaw detection, failure analysis, metrology, assembly analysis, image-based finite element methods, and reverse engineering applications. CT scanning is also applied in the field of museum artifacts’ imaging and preservation.
Aviation security
It has even found an application in transport security in particular, and airport security where it is currently being used in a materials analysis context for detecting explosives. A device called the CT scan explosive-detection device is used here. It is also under consideration for automated baggage parcel security scanning using computer vision-based object recognition algorithms that target specific threat items based on 3D appearance, such as guns, knives, and liquid containers.
Its usage in airport security piloted by Shannon Airport in March 2022 put a stop to the ban of liquids over 100 ml there, a measure that Heathrow Airport plans to implement fully from 1 December 2022, and the TSA invested US$781.2 million in an order for over 1,000 scanners, and it will be coming online this summer.
Geological usage
X-ray computer tomography is a geologic exploration technique whereby the composition of materials within a drill core can easily be identified. Dense minerals, such as pyrite and barite, look bright, and less dense materials, such as clay, appear dull on CT images.
Procedure
The procedure for a CT scan differs with various types of studies such as MRV, MRA, X-ray, brain tumor, laser screening and the organ to be imaged. The patient is placed on the CT table and centering of the table is performed according to the body part. In contrast-enhanced CT, an IV line is initiated. After selecting the appropriate rate of contrast from the pressure injector, radiation-induced cancer a scout is taken to localize and plan the scan. Once the plan has been chosen, then contrast will be administered.
According to the study, raw data processing is carried out with proper windowing to make the scans easy to diagnose. Preparation Depending on the type of scan, the preparation of the patient may vary. The general patient preparation involves.
Signing of informed consent. Removal of metallic objects and jewelry from the region of interest. Change to hospital gown according to the protocol of the hospital. Checking of kidney function, especially creatinine and urea levels.
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