Investigations

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X-rays

X-rays are a type of radiation that can pass through the body and is absorbed at different rates by different parts of the body. A detector on the other side of the x-ray machine picks up the x-rays after they have passed through the body and turns them into an image. X-rays are carried out by trained specialists called radiographers.

During the procedure, the part of your body examined will be exposed to a low level of radiation for a fraction of second. The amount of radiation you are exposed during an x-ray is equivalent to between a few days and a few years of exposure to natural radiation from the environment. It has less than one in 1 million chance of causing cancer in the long term. It is better to discuss with your doctors with regards to the benefits and risks of having an x-ray before having one.

 

Ultrasound scan

The ultrasound scans are a sonogram that uses high-frequency sound waves to create an image of part of inside of the body. Most scans last between 15 to 45 minutes and they do not carry the risk of radiation exposure. During the scan the radiographers or the specialist uses a hand held probe which is placed on your skin and moved over the part of your body being examined. A lubricating gel is put on to your skin to allow the probe to move smoothly. In some patients based on the request from the surgeons the radiologist may inject steroid or local anaesthetic into the inflamed area or joint. The advantage of having this injection under ultrasound guidance is that it is more accurate and is targeted to the area where the problem lies.

 

CT scans

A computerised tomography scans uses multiple x-rays that is then processed in a computer to create detailed images of inside of the body. Some scans may involve injecting contrast just before that. Any allergies or kidney problems should be mentioned to the surgeon who is ordering the test and to the radiographer who is performing the scan. Besides the scan is not advisable for pregnant woman unless it is an emergency as there is a small chance that the x-ray could harm the baby.
The scan usually takes around 10 to 20 minutes and you will usually be lying on your back on a flat bed that passes into the scanner. The scanner usually has a ring that rotates around a small section of your body as you pass through it. Unlike MRI scan the CT scan rarely cause claustrophobia.

The amount of radiation you are exposed during a CT scan varies and is dependent on the amount of body that is scanned. The risk of developing cancer is less than one in 2000. The benefits and risks of having a CT scan should be discussed with the ordering surgeon beforehand.

 

MRI scans

Magnetic resonance imaging is a type of scans which uses strong magnetic fields and radio waves to produce images of inside of the body. The scan can last up to an hour and it is very important to keep as still as possible during the scan. During the scan you will be lying on a flatbed that is moved into a doughnut shaped scanner. You will be lying in a large cylinder shaped magnet during the time when the scan is performed. When you are inside the scanner you will be able to talk to the radiographer through an intercom and they will be able to see you on a television monitor throughout the scan. During the scan the scanner will make loud tapping noises and is because of the electric current in the scanner coils being turned on and off. You can use earplugs or headphones during the scan.

Though MRI scan is safe and painless it can cause claustrophobia. However most of the patients can manage with support from radiographers. As there is a very strong magnetic field around the patient any electronic devices or metal implants in the body should be informed to the radiographer beforehand.

 

Nerve Conduction Study or Nerve Conduction Velocity

A nerve conduction study (NCS) is a measurement of the speed of conduction of an electrical impulse through a nerve. It is used to assess nerve compression, damage and destruction. It usually takes around 45 minutes for the test. During the test, the nerve is stimulated, usually with surface electrode patches attached to the skin. Two electrodes are placed on the skin over the nerve. One electrode stimulates the nerve with a very mild electrical impulse and the other electrode records it. The resulting electrical activity is recorded by another electrode. This is repeated for each nerve being tested. The nerve conduction velocity (speed) is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
A related procedure that may be performed is electromyography (EMG). An EMG measures the electrical activity in muscles and is often performed at the same time as NCS. Both procedures help to detect the presence, location, and extent of diseases that damage the nerves and muscles.
Before you have the test, you should:

  • Remove any jewellery, as this will make it easier for the electrophysologist to attach the electrodes. Leaving your jewellery at home is also a better way of keeping it safe.
  • Wear clothing with short sleeves and/or loose clothing e.g. loose trousers or a skirt, as this will make it easier if we need to look at your legs or arms.
  • Avoid using lotions and creams before your test as cream or lotion on your skin can make it difficult for us to attach the electrodes.
  • Eat and take any medication as normal. It is helpful if you bring a list of your current medications with you.

 
Further information:

  1. X-Rays: https://www.nhs.uk/Conditions/X-ray/Pages/Introduction.aspx
  2. Ultrasound scans: https://www.nhs.uk/conditions/ultrasound-scan/Pages/Introduction.aspx
  3. CT scans: https://www.nhs.uk/Conditions/CT-scan/Pages/Introduction.aspx
  4. MRI scans: https://www.nhs.uk/conditions/mri-scan/Pages/Introduction.aspx
  5. Nerve conduction study: https://www.healthline.com/health/nerve-conduction-velocity#overview1

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