CT Scanners are complicated medical imaging devices, with each component contributing to the creation of successful images. However, different manufacturers don’t always use the same component design, which makes things even more complicated. Here’s a guide that will help you understand the basic function of each CT Scanner component as well as some of the major variations you’ll see in designs.
It’s true that each CT Scan system has a lot in common: each has a scanning gantry, x-ray generator, computer system, console panel and a physician’s viewing console. In addition, most CT Scanning systems include a laser printer for transferring CT images to film, although most of the time workstation viewing and electronic archiving are used.
The three basic segments of image processing are Data Acquisition, Image Reconstruction and Image Display.
When the x-ray passes through a patient to strike a detector and are recorded, data is acquired. The gantry and patient table are the major components involved in this phase of image creation.
About The Gantry
The gantry is the ring-shaped part of the CT Scanner, housing many of the components necessary to produce and detect x-rays. The components are mounted on the rotating scan frame. The diameter of the opening or aperture varies in size, as does the gantry as a whole. The aperture range size is usually 70-90 cm.
The gantry can be tilted forward or backward as needed to accommodate a variety of patients and examination protocols, usually 15-30 degrees. This, too, can vary between manufacturers. On either side of the gantry opening you’ll find control panels used by radiologic technologists to control the alignment lights, gantry tilt and table movement. These functions can also be controlled with the operator’s console in most scanners. There is also a microphone in the gantry that allows communication between the radiologic technologist and the patient throughout the scanning procedure.
About Slip Rings
Today’s newer systems use electromagnetic devices called slip rings, which use a brush-like apparatus that provides continuous electrical power and electronic communication across a rotating surface. Slip rings allow the gantry frame to rotate continuously. This eliminates the need to straighten system cables that would get twisted. By allowing the gantry frame to continuously rotate, helical scan modes are made possible.
About the Cooling System
Cooling mechanisms are located in the gantry. They keep other components from being affected by temperature fluctuations. However, they can take different forms, including filters, blowers or devices that perform oil-to-heat exchange.
About The Generator
CT Scanners currently use high frequency generators. They’re designed to be small enough to fit within the gantry. In the past, highly stable three-phase generators were used. These stand-alone units were located near the gantry and required cables.
Generators produce high voltage and transmit it to the x-ray tube. The power capacity of the generator (listed in kilowatts or kW) determines the range of exposure techniques like kV and mA settings, which are available on a particular system. The generator usually produces high kV (120-140 kV) to increase the beam intensity and reduce patient dose. A higher kV setting helps reduce the heat load on the x-ray tube by allowing a lower mA setting. By reducing the heat load on the tube the life of the tube will be extended.
The source collimation looks like small shutters with an adjustable opening that determines slice thickness. In MDCT systems, slice thickness is also influenced by the detector element configuration, with choices ranging from 0.5-10mm.
There are CT Scan systems that use predictor collimation or post patient collimation. The scan occurs below the patient and above the detector array. This collimate shapes the beam after it has passed through the patient. This approach ensures the beam is the proper width as it enters the detector and prevent scatter radiation from reaching the detector.
This is Part One of CT Components.
In our next blog you will be able to check out X-Ray Tubes, Filtration and Collimation. In part three you will learn everything about Detectors.
Talk To An Expert
If you have questions about CT Scanner systems or their components, talk to an expert at Atlantis Worldwide. We’ve been providing used and refurbished medical imaging equipment to hospitals, clinics, urgent care facilities, veterinary clinics and other healthcare practices for more than 27 years and would be happy to help you.
Follow Atlantis Worldwide on Twitter: @AtlantisLLC
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- Extend The Life of Your Medical Imagining Equipment or Replace It?
- Plan Ahead For Medical Imaging Equipment Purchases
- Free CT Resources
About the author: Vikki Harmonay