CT scanner

A CAT scan or a CT scanner machine is a large machine in the shape of a doughnut. The patient is made to lie on a couch. The couch can slide backwards and forwards. The couch slips into the center of the doughnut shaped machine which takes the x-ray images around the body. The actual procedure takes anywhere from half an hour to one and half hours. During the CAT scan procedure, the patient's bodily movement has to be minimal and should remain as still and quiet as possible. This significantly helps to increase the clarity of the x ray images.

Some CAT scans need special preparations before hand. The preparation may vary according to the type of scan taken.

• For abdominal CT scans, the patient is asked not to eat or drink anything after midnight, the night before the scan. A 'contrast medium' has to be drunk or an injection of 'contrast medium' is administered to the patient. Some of this liquid can be taken at home but more of the liquid is taken in the x ray department before the scan. The contrast medium makes the digestive system show more clearly in the scan. This does not have any side effects.
  
• For CT scans of the head, the patient is given an injection of 'contrast medium' dye beforehand to make the scan clearer.
  
• For CT scans of the chest, the injection of 'contrast medium' dye is administered beforehand to show up the tissues in the area containing cancer or blood vessels more clearly.
  
• For pelvic CT scans, the patient is asked not to eat or drink after midnight of the night before the scan. An injection of 'contrast medium' is given before the scan. An injection of a drug to slow down the movement of the pelvis area is given so that there will be distortion during the time of the scan.
  
• For a rectal scan, the patient is given an enema occasionally. This makes the outline of the bowel stand out more during the scan.
  
• In certain detailed scans of the bowel called virtual colonoscopy, the patient is asked not to eat or drink for 36 hours before the study and two doses of a strong laxative the day before the scan is advised.
  

Bone density test

Special x-rays are used to determine how many grams of bone mineral content (calcium and other bone minerals) is filled into a section of the bone. Bones with high mineral content indicate very dense bones thus indicating the bones are strong and have fewer chances of breakage. Bone density tests are recommended by doctors to check for osteoporosis. Bone density tests are done either by central or peripheral devices. Central devices are huge machines on which the patient can lie down. Such devices are mainly used to check the lumbar vertebrae (lower region of the spine), the narrow neck of the femur bone adjoining the hip and the bones of the wrist and the forearm.

Dual energy X-ray absorptiometry (DXA): This test produces exact results and is the most preferred choice to diagnose osteoporosis. The patient will be asked to lie down on a padded platform as an imager (an apparatus like a mechanical arm) passes above the body. The required information is captured by the device and the test is completed within 20 minutes. The amount of radiation exposure in this test is equal to one-tenth of a chest x-ray radiation. DXA scan can detect even a 1% change in the bone, that which can not be achieved through an ordinary x-ray.

Quantitative CT scan: The bone density (especially spine) is measured with the help of a computerized tomography (CT) scanner along with computer software. The scan produces a three-dimensional picture which also relates to the aging consequences of the bone and diseases other than osteoporosis. The patient is made to lie down on a movable table that is directed into a big tube-like area where images are pictured. The test is completed within 20 minutes and the radiation exposure is slightly more when compared to the DXA scan.

Peripheral devices are moveable machines that measure the bone density on the periphery of the skeleton. e.g. finger, wrist or heel. They are smaller machines when compared to the central devices and can be found in pharmacies and have their own restrictions. These machines are used to check for the bone density in the heel, or wrist or fingers.