• What type of scans are produced?
• What Happens During a Nuclear Medicine Scan?

What Is a Nuclear Scan?

Nuclear medicine differs from standard radiology or x-rays in a number of fundamental ways. In standard radiology, a source of x-rays is placed outside the patient and as the x-rays penetrate the patient, an image is created. In nuclear medicine imaging, a very small source of radioactivity is given to the patient either by mouth or by vein and the gamma rays emitted are measured by a special device called a gamma camera and the data is stored in a computer. The data in the computer is used to generate an image or provide other functional information. The source of radioactivity is in the form of a radiopharmaceutical which travels to an intended organ of interest.

A tremendous amount of research has gone into the development of these radiopharmaceuticals. A diphosphonate derivative images bone, while a compound called MIBI images the heart, and still another known as MAG-3 is specific for the kidney. Aside from just taking pictures or images, nuclear medicine can also study physiological functions of specific organs; for instance the blood flow to the heart, filtration function of the kidney, and iodine metabolism of the thyroid.

In addition, nuclear medicine is a treatment modality for diseases of the thyroid (iodine-131) and cancer (Strontium-89). This triple capability (imaging, function, and treatment) gives nuclear medicine a unique role in medicine. Nuclear medicine provides an extremely sensitive methodology or detecting abnormalities. In the future, we will have radiopharmaceuticals that can detect specific cancers and even treat them effectively.

There is no significant danger from nuclear medicine scans. Only a small amount of a radionuclide is received which is eliminated from the body in one to two days. Usually 95% of the radioactivity is eliminated in just one day.
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What type of scans are produced?

• Bone scan: Used for bone cancer, tumors, fractures, infection. The bone-scanning agent is given and a quick image may be taken and the patient returns three hours later for the complete scan which takes one to one and a half hour to finish.


• Heart scan: A three-dimensional image of the heart is obtained depicting the blood flow to the heart and even the specific blood vessel involved. Special instructions are given for this study. The patient remains in the department for up to five hours.


• Lung scan: Demonstrates blood clots or embolism in the lung.


• Kidney and Bladder scan: Determines the function of the kidney and relative blood flow to each kidney and whether obstruction exists. This technique can be used on small children.


• Thyroid scan: Determines the function of the gland, especially hyperactivity. It is used to image thyroid cancers. The patient is given the dose of radioisotope usually by mouth and returns six hours later for the scan. Occasionally a short visit the following morning is necessary to complete the study.


• Gallbladder scan: Determines the function of the gallbladder.

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What Happens During a Nuclear Medicine Scan?

Scans usually take between one to one and one-half hours to complete. A heart-scan study may take the entire morning because both a rest and exercise portion must be completed.

Be sure to tell the technologist or nuclear medicine physician if you are pregnant or if there is any possibility that you are pregnant. The technologist in the nuclear medicine department will review your entire case history (i.e. whether you have had radiation therapy, x-rays, surgery, what drugs you are taking). The nuclear medicine scan at times has to be tailored to a particular situation and patient. The nuclear medicine scan is correlated with other studies that have been done, for instance a standard X-ray, CAT scan or MRI scan. The nuclear medicine physician may even do a brief physical examination.

The following steps take place after the initial interview.

• You will lie on the scanning table with your clothes on. The technologist will position you under the gamma camera.
  
• You will then be given the radiopharmaceutical by vein or you may have already received it some time beforehand by mouth or vein.
  
• Most scans require different images. Each image takes from five to 15 minutes. A whole body scan may be done (usually only with the bone-scanning agent) which requires about 35 minutes. The camera may be rotated around the organ in question to acquire a so-called SPECT study (single photon emission computed tomography). This is routinely done with heart studies and takes about 35 minutes.
  
• When the scan is completed, you may go home. The results will be reported to your physician the day after the study is performed. Emergency studies will be reported the same day. Sometimes an additional study may have to be ordered but your doctor will discuss this with you.

This article was written by Dr. Lawrence Basso of the Nuclear Medicine Department of the Palo Alto Medical Clinic.

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