Our Health Information Library provides information about radiology exams, including nuclear medicine, CT scans and ultrasound.

Nuclear Medicine

Many nuclear medicine tests involve at least one visit to the nuclear medicine department. All of these procedures involve the administration of a radioactive substance to the patient.

Frequently, making a picture of an organ in the body follows this procedure. Sometimes, instead of a picture, a measurement is made of the amount of tracer that travels though the organ. A few nuclear medicine tests involve collecting a urine specimen and measuring the tracer in the specimen. Most of the nuclear medicine procedures involve injecting a small volume of radioactive tracer into an arm vein.

Beyond the injection, there is little discomfort. Testing can usually be done in ordinary clothing. It's important to emphasize that these are all diagnostic tests and not treatments. Therefore, the tracer you receive will not have any effect on how you feel.

In all nuclear procedures, there is a small amount of radiation exposure. The amount of radiation is ordinarily about the same as that received from a conventional x-ray. This amount of radiation exposure produces no detectable effects on the body.

The staff of the nuclear medicine department includes certified nuclear medicine technologists and a physician who is a specialist in this field. Should you have any questions about the test you will be undergoing, please feel free to ask any of the technologists or the physician present.

For more information about nuclear medicine, including how to prepare for frequently-ordered exams, click here.

CT Scan

Computed tomography, more commonly referred to as CT or CAT scan, is a special type of x-ray procedure that makes cross sectional images of various parts of the body. These cross-sectional pictures show the various structures contained within the region being examined. For example, a CT scan of the body shows the various structures contained within the abdomen, chest or pelvis

Preparing for a CT scan can involve detailed procedures, but as a general guideline, food and fluids should not be taken 3-4 hours prior to exams using contrast media. Although not all CT exams use contrast media, contrast is used for certain CTs in order to highlight specific structures.

As with any injected drugs, there are certain risks associated with the use of contrast agents. Although these risks are minimal, certain patients will have greater risk than others, so the patient is asked specific questions in order to determine risk factors. The benefits provided by contrast agents, as well as by the CT procedure itself, should outweigh the risk significantly. A physician must order this exam for a specific reason so that the area examined and the range of pictures obtained provide the appropriate diagnostic information.

For more information about CT scans, including how to prepare for commonly-ordered exams, click here.

Ultrasound

Ultrasound, also called ultra sonography, is a diagnostic procedure that can be performed on various parts of the body. The principles of ultrasound are similar to that of sonar used commonly in submarines. High frequency sound waves are transmitted through instruments called transducers to visualize structures of the body. The sound waves travel through the body and bounce off the structures of interest, returning echoes of sound waves to the transducer. The transducer, by way of sophisticated electrical equipment, translates the returning echoes into images representing the anatomical structures in the region examined by ultrasound. These images can be viewed on a television monitor as well as printed on paper or film.

Ultrasound has no known harmful effects. There is no radiation used, nor any injection of contrast materials. Although many exams require no advance preparation, certain exams do require simple preparations. For example, exams of the abdomen require fasting prior to the exam in order to prevent ingestion of air. For gallbladder exams, ingestion of fatty foods is prohibited prior to examination because fats will stimulate the gall bladder to contract, making the visualization of stones difficult. For pelvic and obstetrical exams, a full bladder displaces gas filled bowels allowing for sound waves to penetrate the entire region of interest, therefore drinking water before exam time is required.

For more information about ultrasound, including how to prepare for commonly-ordered studies, click here.