Digital Imaging Helps In Medical Research – Viewing The Brain
Digital imaging system helps in medical research. Some imaging modalities rely on the use of beams of ionizing radiation. These include x-rays, angiography and CT scanning. Others require the injection of radioisotopes, like PET scanning. Magnetic Resonance Imaging (MRI) and Functional Magnetic Resonance Imaging (fMRI) require a strong magnetic field. Magnetoencephalography (MEG) is a new way of looking at the brain.
A CT scanner passes over the patient lying on a special table and records the first x-ray image. It takes a series of x-rays around the patient’s head by moving around in small increments. The computer manipulates the collection of images to produce cross-sectional and sometimes 3D views of the head. The procedure takes about half an hour and is completely painless.
Molecules like oxygen or glucose can be labelled with radioisotopes and then injected into the blood stream. From there, they migrate to regions of the brain that are metabolically active. When a radioisotope breaks down, a neutron and a position are formed. When a positron inevitably collides with an electron, both particles are destroyed yielding two gamma rays. These gamma rays are visualized via the PET scan to display a functional image of the brain.
Magnetic Resonance Imaging employs a strong magnetic field along with radio waves to produce very detailed pictures of soft tissues such as the brain. Similar to CT, the patient lies on a special table that slides into the digital imaging system. It is essential that the patient removes all exterior metal jewelry, watches, etc, and does not have any internal metal implants that can interfere with the image and cause discomfort or even damage to the patient. MRI has been in routine use since the early 1980s.
The first MRI scanners had very little space for the patient and the scans took a long time to produce – as long as 45 minutes or more. In some people, this can trigger severe anxiety or a condition called claustrophobia (the fear of enclosed spaces). For this reason, as many as 20 per cent of patients refused to go ahead with the procedure. Modern equipment allows the patient to remain standing and fewer patients are refusing. If necessary, light sedation or cognitive behavioural techniques can make the patient more comfortable.
Functional MRI can detect increased use of oxygen and glucose as well as changes in blood flow to areas of the brain that are particularly active. It therefore provides a functional as well as anatomical picture of the brain.
Following injection with a special dye, a number of x-rays are performed. This technique produces a picture of the network of the brain’s blood vessels. This is called an angiogram.
Magnetoencephalography is a new method of imaging the brain. It measures the activity of the brain in real time. In patients who are diagnosed with seizures, MEG and MRI used concurrently can assist the neurosurgeon to identify and cut out the damaged tissue and leave healthy brain behind. MEG can determine the location of the lesion more accurately than MRI on its own.
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