ABOUT CT SCAN

Computed Tomograph (CT) Imaging or in other name “CAT Scanning” (Computed Axial Tomography). Greek word “tomos” which mean slice or section and word “graphia” mean describing is refer to word tomography. Based on history, in 1972 this CT scan was invented by British engineer Godfrey Hounsfield of EMI Laboratory, England and South Africa born physicist Allan Cormack of Tufts University, Massachusetts.

Between 1972 and 1976, the first clinical CT scanner was installed. At first, the original system was dedicated to head imaging only. After that in 1976, whole body system with large patient opening was created and available. Four years later in 1980, this device became widely around the world. In US only, about 6000 CT Scanner installed and about 30,000 installed worldwide.

The first CT Scan that created by Hounsfield in his lab at EMI need several hours to acquire the raw data for a single scan or slice. A single image from a raw data also need a couple days to complete this process. In contrast, the latest multi-slice CT system can collect up to four slice of data 350 ms and less than a second needed to reconstruct a 512 x 512 –matrix image from the millions of data. An entire chest (forty 8 mm slices) can be scanned in five to ten seconds using the most advanced multi-slice CT system.

As the time flow, CT scan has made great improvement and upgrade in speed, patient comfort, and resolution. As the CT scan time gotten faster, less time needed by an anatomy to do this scan process. Another benefit when this process going faster is it also help to eliminate artifact from the patient motion such as breathing and peristalsis. Compare the old one, CT scan now are quicker and more patient friendly than ever before. Tremendous research and development has been made to provide excellent image quality for diagnostic confidence at the lowest possible x-ray dose.  

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FUNCTION

·      Produce very detailed images of many structures of human body, including the internal organs, blood vessels and bone. 

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· Used to diagnose diseases such as pancreatic cancer, further guidance for tests and treatments like surgery and biopsy and monitor the condition of a patient. 

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·  Used to produce images of head, lungs, cardiac, abdomen pelvis, pulmonary arteries, and complex fractures.

COMPONENTS OF CT SCAN

a)      Gantry of CT scan

·  It is made up of all the equipment that are related to the patient which are:

Ø  the patient support, 

Ø the positional couch, 

Ø  the mechanical support,

Ø  the scanning housing. 

·    X-ray tube (heart of CT Scan) works as a detector that :

Ø   generates x-ray

Ø  detects x-ray. 

X-Ray Tube

 X-Ray Detector

·  Patient will be given contrast material by mouth, injection, and enema to help in highlighting the part of the examined body. 

· This contrast material will block the x-ray and appears white on the image.

 This can help to emphasize the blood vessels, intestines, and other structures.

 Gantry of CT Scanner

b)      Operating console of CT scan

The operating console is the control center of the CT scan. 

·         It is used to put all the factors gained from the scanning. 

·         This control center consists :

Ø  a computer, 

Ø  a keyboard, 

Ø  multiple monitors.  

·         There are two different control consoles :

Ø   used by the CT scanner operator,

Ø   used by the physician. 

·         The operator's console controls features such as:

Ø  the thickness of the imaged tissue slice 

Ø   mechanical movement of the patient couch. 

·         The physician's viewing console 

Ø  allows him to view the image without interfering with the scanner. 

Ø  Image manipulation can diagnose and store image. 

Console of CT scanner

HOW IT WORKS

CT scanning works like an x-ray examinations. The x-ray absorption varies in different types of body parts which is crucial to differentiate from one another on an x-ray film or CT electronic image.

In a conventional x-ray examination, small amount of radiation is bombarded and pass through the targeted area. The image is then recorded on a special electronic image recording tools. Bones will appear white on the film while the soft tissue such as the organs will produce gray image, and air appears black.

As the body moves through the arc, a CT scanner will emit a series of narrow beams. The final image produce by CT scan is far more detailed than X-ray image.  There is an x-ray detector inside the CT scanner which can see various levels of density. It can see tissue inside a solid organ. The data is transferred to a computer which will process it into a 3D cross-sectional picture of the targeted body parts and displays it on the screen. When the image slices are rearranged by computer software, the result is detailed multidimensional view of the targeted body part.

Sometimes, a contrast material is used to provide a clearer image of the targeted area. If a targeted area is abdomen, the patient needs to drink a barium meal. Barium will appear white on the scan as it travels through the digestive system. If the targeted is at lower body such as the rectum, then the patient may be given a barium enema. If the targeted are is blood vessels the patient will be injected with barium.

The accuracy and speed of CT scans can be improved with the application of spiral CT. The x-ray beam takes a spiral path during the scanning. The CT scanner then will gather continuous data with no gaps between the images. 

WHAT IS THE SYSTEM OF CT SCAN ?

INPUT SYSTEM:

   

     Input component of CT scan is  gantry. The patient is placed inside the gantry that contains several x-ray tubes and detector. The gantry will rotate around patient and the ray from the x-ray tube will penetrate through patient’s body and the rays will be collected by the detectors. The rays collected will be converted into data (in electrical signal) and transferred to the computer. The gantry will rotate several times to produce complete 3-dimensional views. A complete scan produces a complete data set that contains sufficient information for the reconstruction of an image. 

Gantry rotates around patient

OUTPUT SYSTEM:

Output system include hardware and software. Computer is the main hardware that is used in CT imaging system. The computer is used to display the CT images and situated at the workstation that have operator’s console. 

There are 3 consoles at the workstation that are used to operates the imaging system by:

1.   the technologist, 

2.   for post processing filming 

3.   for viewing and manipulating images by the physician. 

The software in the computer allows the operator to program the scan sequence, display scan images, edit, and measures the image, enter patient data, and send and receive images from storage.

 CT image formation consist 3 steps:

 1. Scanning phase 

·  in the input system where the patient is scan by using gantry thus produce data.

 2. image reconstruction phase

·  the data/raw data is produced.

 3. image display. 

·   the image is display on the computer’s monitor.

·          black and white or colour.

                                        

                 Images displayed at monitor

The software that used for communications of data or images between CT scan to other devices is known as DICOM (Digital Imaging and Communications in Medicine). It uses in variety of medical appliances such MRI, Ultrasound, and CT scan. DICOM allows the transferring text data and images to workstations, printers, display monitors in the department. DICOM can operates with Picture Archiving and Communications System (PACS). PACS allow the CT images to be send to other workstations in other department such in intensive care unit to view the images at the same time.