Techniques (such as CAT scan, MRI, X rays, ultrasound, and radioactive scans) that permit visualizing (seeing) areas of the body.
These are methods that generate images of structures inside the body.
The most widely used and straightforward techniques are X-rays, also known as plain X-rays, which provide views of dense structures like bones. Common X-ray examinations involve the chest, skull, and limbs after an injury.
Contrast X-rays involve introducing a substance into the body that is opaque to X-rays. Various techniques utilize this approach, including barium X-ray examinations (for the oesophagus, stomach, and intestine); cholecystography (to visualize the gallbladder and common bile duct); bronchography (for the airways connecting the windpipe to the lungs); angiography and venography (for imaging blood vessels); intravenous urography (to view the kidneys and urinary tract); and ERCP (where the pancreatic duct and biliary system are examined by introducing a contrast medium through an endoscope).
Numerous X-ray techniques have been replaced by newer procedures that are easier to conduct and offer improved safety and comfort for the patients.
Ultrasound scanning employs high-frequency sound waves transmitted through the body via a transducer placed against the skin. The waves are reflected differently by structures of varying density, and the resulting echo pattern is electronically recorded on a screen. Nowadays, ultrasound scanning can generate three-dimensional images and moving visuals, revealing phenomena such as the opening and closing of a valve or blood flow within a vessel.
Numerous scanning techniques rely on computers to process raw imaging data and generate the final image. In computed tomography (CT) scanning, X-rays are directed through the body at various angles. The computer analyzes the data to create cross-sectional images (referred to as “slices”) of the examined tissues. Modern CT scanners can employ a spiral technique to produce three-dimensional images of structures.
During MRI (magnetic resonance imaging), the patient is positioned inside a powerful magnetic field within the scanner, and radiofrequency waves pass through the body. A computer analyzes the alterations in the magnetic alignment of the nuclei in the hydrogen cells, resulting in either a cross-sectional or a three-dimensional image of the tissues. This technique offers better contrast between normal and abnormal tissues compared to CT scanning.
PET scanning (positron emission tomography scanning) includes the administration of short-lived radioisotopes into the brain tissues. A computer then analyzes the paths of the gamma rays emitted by these radioisotopes, providing valuable information about both the structure and function of the brain.
In radionuclide scanning, a gamma camera captures radiation emitted from tissues that have been exposed to a radioactive substance. The recorded data is transformed into images by a computer, which can provide additional information from the results. Various radioactive substances are absorbed to different extents by different tissues, enabling the study of specific organs in isolation.