The term nuclear scintigraphy is commonly used in veterinary medicine. In human medicine, the term nuclear medicine or molecular imaging replaced nuclear scintigraphy. In any case the terminology means the same thing. Nuclear medicine is a branch of radiology similar to x-ray, ultrasound, CT, and MRI.
Nuclear Scintigraphy deals with the physiology of the body and verifies how things are functioning. A radioactive isotope or material is injected, ingested, or inhaled by the animal. A short period of time later, the animal can be imaged to look for any specific abnormality in the body.
Nuclear Scintigraphy deals with radioactive materials and is controlled by the NRC (Nuclear Regulatory Commission). The government requires specific precautions, procedures, safe handling, and determines the length of stay in the veterinary facility.
Some common nuclear scintigraphy exams used in veterinary medicine may include:
- Bone Scintigraphy in Equine and Small Animals
- Thyroid Disorders in Small Animals
- Renal Scintigraphy
- Ventilation Perfusion Lung Imaging
- Gallbladder Imaging
- Portal Scintigraphy
Bone Scintigraphy or bone scanning evaluates the skeletal system of animals. The distribution of a these radioactive isotopes is dependent on the rate of bone turnover and blood flow. The images obtained reveal changes in bone metabolism more than changes in bone structure. Images can be taken at different times in order to evaluate blood flow verses soft tissue and bone metabolism. Lesions like fractures, infections, tumors and arthritis can be seen on Bone Scintigraphy before they appear on plain radiographs (X-ray).
Unexplained lameness in equine as well as small animals can be evaluated with bone scintigraphy. Localization of the source of lameness in a veterinary patient is frequently difficult. This is difficult because the patient cannot communicate and explain the source of their pain.
Thyroid disorders have become more common in older cats and dogs. Older cats predominately have hyperthyroidism which is an over active thyroid gland. Dogs on the other hand may acquire hypothyroidism which is an underactive thyroid gland.
Hyperthyroidism therapy can include medications to block the manufacture of thyroid hormones, surgery, or radioactive iodine therapy. Surgery can be difficult to perform on the small thyroid glands but in certain cases is available. Medications can be affective in the treatment of hyperthyroidism but may require giving 1-3 tablets a day to your cat. Other application methods of medicating are available but still require time to give to your cat. The best treatment option for feline hyperthyroidism is radioiodine I-131 therapy.
Canine hypothyroidism if diagnosed can be treatment with medication alone.
In both hyperthyroidism and hypothyroidism, patients can be identified with various blood sample testing.
Renal Scintigraphy is a valuable tool for evaluations of kidney function and the urinary tract. With renal scintigraphy, the relative amount of radioactive isotope extracted from the blood by a kidney is proportional to that kidney’s function. This is also called Glomerular Filtration rate (GFR). Both the anatomical and functional information can be obtained using renal scintigraphy.
Renal disease is one of the most common illnesses affecting veterinary patients. Potential kidney diseases may include: neoplasia, cysts, nephrtolithiasis (stones), and injury from toxic exposure.
Ventilation and Perfusion Lung Imaging
A ventilation and perfusion lung scan is also called a V/Q scan and is used to detect a blood clot that is preventing normal blood flow to part of a lung (pulmonary embolism).
Two types of lung scans are usually done together:
During a ventilation scan, a radioactive gas or mist is inhaled into the lungs. Images from this scan can show areas of the lungs that are not receiving enough air or that retain too much air. Areas of the lung that retain too much air show up as bright or “hot” spots on the pictures. Areas that are not receiving enough air show up as dark or “cold” spots.
During a perfusion scan, a radioactive isotope is injected into a vein. It travels through the bloodstream and into the lungs. Images of the lungs can verify if the lungs are receiving enough blood. The isotope is absorbed evenly in areas of the lung where the blood flow is normal. These areas show up with the tracer distributed evenly. Areas that are not receiving enough blood show up as cold spots.
If the lungs are working normally, blood flow on a perfusion scan matches air flow on a ventilation scan. A mismatch between the ventilation and perfusion scans may indicate a pulmonary embolism.
Ventilation and perfusion scans can be done separately or together to diagnose certain lung diseases. If both scans are done, the test is called a V/Q scan.
V/Q scans in dogs and cats can be helpful in diagnosing chronic cough, breathing problems, bronchitis, potential blood flow and air flow concerns, and other lung disorders.
The gallbladder is a balloon shaped organ that is located in the lobes of the liver. Its function is for the storage of bile to aid in digestion. Gallbladder disease can occur when there is an obstruction of the gallbladder or bile ducts that restrict the flow of bile from the gallbladder.
Nuclear scintigraphy gallbladder imaging can detect if the gallbladder is properly functioning and the cause of the animals systemic problems.
Transcolonic portal scintigraphy is a procedure available for diagnosing portal systemic shunts in dogs and cats. The portal system is comprised of blood vessels collecting and draining blood from the stomach and intestines. The portal system ensures that the liver has the opportunity to utilize nutrients.
A portosystemic shunt is an abnormal communication between the portal circulation and the systemic circulation (the blood supply to the rest of the body). Shunts are placed in animals with poor growth or central nervous system signs such as seizures, tremors, circling, and high levels of toxins in the blood stream.
A patient with a shunt has been identified as having a congenital (at birth) abnormal blood vessel. Shunt vessels allows the blood from the gastro-intestinal tract to bypass the liver and go directly into the systemic circulation.