One of the first scans made by a photoscanner. The photorecording (dark bands), superimposed on an X-ray picture for orientation, shows radioactivity in a cancer in the patient’s neck.
It should be evident that tracers used in diagnosis—to identify disease or improper body function—are present in such small quantities that they are relatively harmless. Their effects are analogous to those from the radiation that every one of us continually receives from natural sources within and without the body. Therapeutic doses—those given for medical treatment—by contrast, are given to patients with a disease that is in need of control, that is, the physician desires to destroy selectively cells or tissues that are abnormal. In these cases, therefore, the skill and experience of the attending physician must be applied to limit the effects to the desired benefits, without damage to healthy organs.
This booklet is devoted to these two functions of radioisotopes, diagnosis and therapy; the field of medical research using radioactive tools is so large that it requires separate coverage.[7]
DIAGNOSIS
Pinpointing Disease
Mr. Peters, 35-year-old father of four and a resident of Chicago’s northwest side, went to a Chicago hospital one winter day after persistent headaches had made his life miserable. Routine examinations showed nothing amiss and his doctor ordered a “brain scan” in the hospital’s department of nuclear medicine.
Thirty minutes before “scan time”, Mr. Peters was given, by intravenous injection, a minute amount of radioactive technetium. This radiochemical had been structured so that, if there were a tumor in his cranium, the radioisotopes would be attracted to it. Then he was positioned so an instrument called a scanner could pass close to his head.
As the motor-driven scanner passed back and forth, it picked up the gamma rays being emitted by the radioactive technetium, much as a Geiger counter detects other radiation. These rays were recorded as black blocks on sensitized film inside the scanner. The result was a piece of exposed film that, when developed, bore an architectural likeness or image of Mr. Peters’ cranium.
The inset picture shows a brain scan made with a positron scintillation camera. A tumor is indicated by light area above ear. (Light area in facial region is caused by uptake in bone and extracellular space.) The photograph shows a patient, completely comfortable, receiving a brain scan on one of the three rectilinear scanning devices in the nuclear medicine laboratory of a hospital.