Dr Amit Chakraborty, Jan 2023
What is a CT scan and how does it work?
A CT scan stands for ‘Computed Tomography’. It uses radiation to produce images, although the way it does so is very different to that of a conventional x-ray machine.
Unlike an x-ray machine, the CT scanner looks like a giant doughnut. The x-ray tube rotates around the patient in a 360° circular motion and produces a comprehensive set of images that are much more detailed than the conventional x-ray.
What are the advantages of a CT scan?
i. A CT image is much more detailed than an x-ray or ultrasound machine. Internal structures are visualised from a 360° angle which allows for better detection of abnormalities.
ii. Due to its 360° imaging capability, a CT scan is able to produce clearer images of deeper organs which can be hard to image with other techniques such as ultrasound.
iii. A CT scan is a great tool for imaging bones, deeper soft tissue organs as well as gas containing organs such as lungs.
A powerful computer processes the obtained images in a manner that allows for the images to be viewed at any angle. This means that various structures and abnormalities can be examined from angles that provide the best visibility and diagnostic interpretation.
The use of contrast dye with CT scans can provide valuable additional information. It can help to differentiate abnormalities from normal tissue. It can help assess the level of blood supply to a particular structure. Organs that lie in close proximity can be better visualised by using the dye. Critical blood vessels and related abnormalities can also be clearly imaged by using contrast dye medium.
A radiologist uses CT guidance to access sensitive, deep-seated organs for biopsy or cortisone injection. Spinal nerve pain relief injection is a good example. The use of CT scan allows for precise needle positioning, and significantly enhances the safety and effectiveness of the treatment.
Surveillance of thyroid nodules: Certain types of thyroid cancers can be deadly. If you have been diagnosed with thyroid nodules, follow up imaging at 12 to 24 months interval can significantly increase the chances of detecting a cancerous nodule early. A cancerous nodule can be detected and removed much earlier if routine surveillance is done by an ultrasound examination.
What are the disadvantages?
A CT scanner uses radiation. The dose of radiation is usually higher than that used by an x-ray machine. More on this later.
A CT scan requires a patient to lie flat on a bed. This can be challenging for people with respiratory or mobility difficulties.
Healthy renal function is required for the use of contrast dye.
Patients are required to hold their breath and stay still for the duration of the examination. This can be difficult for people with respiratory difficulties or movement disorders.
A CT scan can sometimes find it hard to differentiate between a solid and liquid structure such as a solid tumour and a cyst.
CT scan and radiation:
Although the CT scan uses more radiation dose than a conventional x-ray, the risk vs benefit ratio is significantly in favour of the CT scan. That is, the information gathered by a CT scan carries significantly more benefit than the radiation dose that it imparts.
Modern CT scanners use sophisticated computer algorithms and other various dose reduction technologies which enable them to obtain images using substantially less radiation than the previous generation of scanners. For example, the CT scanners at CareScan are equipped with the latest industry standard ‘Tin filter’ technology. This produces a dramatic reduction in the amount of radiation received by the patient. With our scanners, the radiation dose received by the patient from a CT scan is often comparable to a conventional x-ray. This means that getting CT scans is now just as effective and safe as an x-ray, although the benefits are significantly more.
The latest generation CT scanners are extremely fast and accurate. This means the amount of time that the patient has to spend lying inside a scanner is significantly less than before. These advanced scanners also mean that the amount of contrast dye used to obtain the same quality images is now substantially less.
At CareScan imaging, we provide CT scan Liverpool locals can trust. We are proud to offer latest generation CT capability to the general public at little to no cost. All body parts that were previously imaged by x-rays can now be safely and quickly imaged by a CT scanner which provides quicker and more accurate diagnosis. The radiation dose is only minimally greater than that of a conventional x-ray examination.