The different forms of medical imaging

Recently there was a middle aged woman who was demanding for an X-ray because she had severe burning pain in the abdomen. Aware that the scan would not establish the cause of the problem, health officials had to dissuade the patient from having the X-ray. Medical imaging is the technique and process of creating visual representations of the interior of body for purposes of medical diagnosis or intervention. There are several imaging techniques available today and one should be aware of the usefulness of different techniques. X-rays have been in existence since now almost 100 years. X-rays are a form of electromagnetic radiation. A radiograph is an X-ray image obtained by placing a part of the patient in front of an X-ray detector and then illuminating it with a short X-ray pulse. Because of the high density due to calcium, skeletal system including bones absorbs X-rays very well. Hence it is very useful to diagnose disease and disorders of bones like fractures, tumors, etc. They also aid in detecting diseases of some other body parts like diseases of the lungs, enlargement of the heart, etc. Bullets and other foreign items lodged in some part of the body can be detected very well with an X-ray. In special situations like diagnosing obstruction in the food pipe or stomach, special X-rays are taken after using barium sulphate as contrast medium. Depending on the site of alimentary system to be visualized, it can be swallowed or used as enema. This fills in normal part, but fails to reach beyond an obstruction. X-rays are also useful in treating some kind of advanced cancers and goiter where the cells of hyperthyroid goiter or tumor are killed by radiation. However it does not show all that is wrong in the body. X-rays cannot detect soft tissue injuries like muscle or ligament tear. Problems in the food pipe and stomach like ulcers and inflammation of the inner lining are not seen so well by X-ray. One needs endoscopy for their diagnosis, where the endoscopy tube is put through the nose and the alimentary system from food pipe to the first part of small intestines is visualized very clearly and even a small piece can be taken for biopsy if needed. Computerised scan (C.T. scan) is an advanced form of scan where X-rays are taken from different cross sections of the organ being studied. The different images are processed through computer. This scan gives a 3 dimensional picture of the organ under study. It helps to diagnose tumors, extent of injuries, cause of stroke in the brain and many other problems. Magnetic resonance imaging (MRI) gives visual picture in greater detail than a C.T. scan. Other specialized scans like scinti scan, isotope scan help in diagnosing extent of spread of tumor or infection in body parts, extent of ischemia or damage caused to heart muscle. The machines used for X-rays or C.T. scans currently are very safe and there is negligible risk of one getting adverse effects of radiation by just undergoing these tests. In ultrasound, very high frequency of sound waves is directed to the part of the body under examination through a probe and the image formed by reflection is visualized on a screen. Ultrasound is very safe to use in pregnancy as X-rays can harm the baby inside the uterus. It also helps in diagnosing diseases of visceral parts of body like heart, pancreas, liver, gall bladder, kidneys; e.t.c. Doppler is part of ultrasound which can show state of blood vessels of body. However ultrasound does not pass through dense parts of body like bones or those which trap air/gas like bowels. Hence as per the patient’s complaints and suspected diagnosis, a clinician can decide if he needs imaging and which kind. Dr Rachna Pande is a specialist in internal medicine at Ruhengeri Hospital

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The different forms of medical imaging