2011年11月22日 星期二

Pet Scans Vs CT Scans


The CAT scan (Computerized Axial Tomography), also known as a CT scan, was invented by Sir Godfry and Robert Ledley in 1975. It was the first diagnostic tool able to see inside the body and brain. A CT scanner emits a group of narrow beams of radiation through the human body, unlike an X-ray machine that uses just one beam of radiation. The key drawback of a CT scan is the use of radiation. CT scans use radiation that can cause damage to a person's DNA after continued exposure. However, some radiology departments still use CT scans as a preferred screening test for ailments including chest ailments and broken bones.

Positron Emission Tomography (PET) scans measure emissions from positron-emitting molecules. In the 1970s, PET scanning was introduced to the medical community. During the 1980s, the technology that underlies PET advanced greatly. Commercial PET scanners have resolution that is more precise and images that are more accurate than CT scanners. Many of the steps required for producing a PET scan are performed by a trained technician or an experienced physician, thereby reducing the cost and complexity of the procedure. The main difference between the CT and PET scans is the PET scan shows molecular function and activity instead of structure, and therefore can often differentiate between normal and abnormal tissue. A PET scan produces three dimensional images and usually compliments rather than replaces the information obtained from a CT scan. By measuring blood flow and metabolic rate within the heart, physicians using PET scans can discover areas of decreased blood flow, such as those areas with blockages, and differentiate living muscle from damaged muscle that has inadequate blood flow. This information is particularly important for patients who have had previous myocardial infarction or who are being considered for a procedure such as a coronary artery bypass surgery or angioplasty.

The information provided here shows the need for discernment in deciding which or how many scans to consider. Each test has its place depending on exactly what type of condition needs to be diagnosed.




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