Nuclear Medicine Imaging Studies

COMMENTS?

 

 
In Nuclear Medicine, the patient is given a radioactive tracer agent either by mouth (capsule) or injected intravenously. The tracer goes to the target organ and can then be imaged with a Gamma Camera which takes pictures of the radiation photons emitted by the radioactive tracer.

Allergies: As a general statement, there are no allergic reaction to radionuclide tracer agents.

Bone Scan: The tracer is taken up by the bones and shows area of bone activity such as fracture, arthritis, tumor, metastatic disease, etc. The patient is injected intravenously in the morning with the bone scan agent and returns to the department three hours later for imaging of the skeleton under a gamma camera. See images below.

Normal Radionuclide Bone Scan example images

Bone scan shows multiple rib fractures (red arrows) from coughing (osteoporosis ribs)

Liver Spleen Scan: The patient is injected with technetium 99M sulfur colloid particles which are selectively taken up by the liver cells. The scan shows the Liver and Spleen (see image at right). This is useful in detecting space occupying lesions in the liver and is used as a screening test for intrahepatic metastatic disease from cancer.

Renal Scan: The patient is injected intravenously with technetium 99-m MAG-3 which is excreted by the kidneys. Images of the kidneys are taken with a Gamma Camera immediately after injection showing blood flow into the kidneys. Images are then taken over the next 20 to 30 minutes showing renal function. This is useful to show ureteral obstruction due to stone or tumor, residual renal function and renal artery stenosis. For more sensitive detection of renal artery stenosis, the patient may be given a Captopril tablet 1 hour before the MAg-3 renogram test.

MAG-3 renogram shows obstructive uropathy (blocked ureter)

Ventilation and Perfusion Lung Scan: The patient is injected intravenously with technetium 99-M macroaggregates or particles. This is a radioactive tracer which goes to the lungs and becomes trapped in the small capillary vessels of the lungs. See normal lung scan images at the left. If there is a blood clot in one of the pulmonary arteries, then the radioactive tracer particles are blocked from entering this segment of lung tissue and it shows up as a filling defect on the lung scan. This is useful in detection pulmonary emboli or clots lodged in the pulmonary arteries. A ventilation scan image is also done by giving the patient radioactive xenon to inhale. The ventilation images helps the radiologist to interpret the perfusion lung scan.

Normal Perfusion Lung Scan

Abnormal Multiple Perfusion Defects Positive for pulmonary embolus

 

Hepatobiliary Scan: This is useful for evaluation of acute cholecystitis (a Hot Gallbladder). The patient usually has a prior GB Ultrasound test which shows Gallstones, and may have right upper abdominal pain, fever, nausea, and other symptoms.

   Procedure: The patient is injected IV with the radiotracer agent, over the next 2 hours images of the lever and gallbladder and biliary tree are taken with a Gamma Camera. If the Gallbladder does not visualize within 2 hours, then this indicates acute cholecystitis with cystic duct obstruction, and surgical removal of the Gallbladder is usually done as the next step.

Thallium Scan: The purpose of this test is to demonstrate coronary artery disease.

The patient is exercised on a treadmill with EKG monitor in place under supervision of a nurse and cardiologist. At peak cardiac stress, maximal exercise, the patient is injected i.v. with the thallium radiotracer, which is then taken up by the heart muscle. The patient is then placed under the gamma Camera and pictures of the heart are taken. The patient returns 3 hours later for a second set of pictures, which are done in the resting state.

Thallium scan is useful for showing coronary artery disease which shows up as areas of heart muscle with less thallium radiotracer in it because of the reduced blood flow from the narrowed vessels.

As the next step, Cardiac catheterization may be performed to evaluate the coronary arteries more completely and to perform angioplasty or stenting if needed.

Thyroid Uptake and Scan: Precautions: if the patient is recently had an IVP or CAT scan with iodinated contrast, then the scan should not be performed since it will not show the thyroid gland.

   Procedure: The study consists of two parts: The 24 hour uptake, and the thyroid images.

The 24-hour uptake is a quantitative number, which indicates how active the thyroid gland is. It is increased in hyperthyroidism (Grave’s Disease) and decreased in hypothyroidism. It is named 24-hour uptake because, the patient takes the radioactive iodine by mouth and returns the next day and the activity in the neck is counted by a scintillation counter.

The thyroid scan may be performed with I-131, I123 or merely technetium pertechnitate. The scan shows the size of the gland, masses, nodules, cysts, etc. Thyroid ultrasound is frequently done as the next test to further define the anatomy.

Technetium labeled WBC scan: The image on the right shows a technetium labeled white blood cell scan of the feet of a diabetic patient with infection in the great toe of the left foot. Notice the dark spot at the site of infection. This test is useful for showing sites of infection where white blood cells accumulate such as in osteomyelitis of the extremities, abdominal abscess etc.

Technetium labeled RBC scan: This test labels the red blood cells with a radioactive tracer. It is useful for imaging the beating heart called a MUGA or gated wall motion scan. It is also useful in patients with gastrointestinal bleeding for detecting the site of GI bleeding (this is called a GI bleeding scan).