Nuclear Cardiology

Overview

In the Western world, heart disease is the leading cause of mortality. More than 500,000 men and women die in the United States each year as a result of coronary artery disease. Over the last two decades, significant advances have been achieved in the detection and treatment of cardiac disease. Nuclear cardiology has been critical in establishing the diagnosis of heart disease, as well as in assessing disease extent and predicting outcomes in the setting of coronary artery disease.

Nuclear cardiology studies employ noninvasive techniques to examine myocardial blood flow, assess the heart's pumping function, and visualize the magnitude and location of a heart attack. Myocardial perfusion imaging is the most often utilized nuclear cardiology technology.

What is Nuclear Cardiology?

Nuclear cardiology is a subspecialty of general cardiology, a noninvasive functional diagnostic method that, as single photon imaging, has been used as a clinical cardiac tool for decades.

The distribution of biomolecules tagged with modest dosages of radioactive isotopes with short half-lives is evaluated, allowing evaluation of myocardial perfusion, contractile function, and metabolism. The usual approach is single photon emission computed tomography (SPECT), which delivers great diagnostic accuracy, reliability, and repeatability. PET and the innovative hybrid systems that are now available are projected to improve accuracy much further, particularly in large patients.

Nuclear cardiologists must finish up to eight years of secondary school, as well as a residency program, before enrolling in a four-year program at a Liaison Committee on Medical Education (LCME) recognized university. They must then finish a nuclear cardiology residency program before becoming certified by the Certification Board of Nuclear Cardiology (CBNC).

Indications for Nuclear Cardiology

Physicians use cardiac nuclear medicine studies to help diagnose cardiac disease. The symptoms include:

unexplained chest pain.
chest pain brought on by exercise (called angina).
shortness of breath with exertion.
abnormal electrocardiogram.

Cardiac nuclear medicine imaging is also performed:

a myocardial perfusion scan is used to visualize blood flow patterns to the heart walls.
to assess the existence and severity of suspected or established coronary artery disease.
to assess the amount of cardiac harm following a heart attack, also known as a myocardial infarction.
to assess the outcomes of bypass surgery or other revascularization operations aimed at restoring blood flow to the heart.
a method known as cardiac gating is used in combination with an electrocardiogram (ECG) to measure heart-wall movement and overall heart function.

What Does The Equipment Look Like?

Nuclear medicine imaging techniques include a specific gamma camera and single-photon emission computed tomography (SPECT).

The gamma camera captures and transforms the energy emitted from the radiotracer in your body into a picture. The gamma camera itself emits no radiation. It has radiation detectors known as gamma camera heads. These are enclosed in metal and plastic, commonly in the shape of a box, and are attached to a circular, donut-shaped gantry. The patient is lying on an exam table that glides between two parallel gamma camera heads, one above and one below the patient. The gamma camera heads are sometimes oriented at a 90-degree angle over the patient's torso by the doctor.

The gamma camera heads in SPECT rotate around the patient's body to produce detailed, three-dimensional images.

A gamma camera is used in the majority of nuclear medicine procedures. Some nuclear medicine equipment has CT capabilities that help improve the images and increase the ability to combine functional imaging (nuclear medicine) and anatomic imaging (CT).

A computer creates the images using the data from the gamma camera.

How Should I Prepare?

During the test, you may choose to wear a gown or your own clothes.

If a woman is pregnant or nursing, she should always inform her doctor and a technologist. More information on pregnancy and nursing in nuclear medicine imaging may be found on the Safety in X-ray, Interventional Radiology, and Nuclear Medicine Procedures page.

Inform your doctor and exam technologist of any drugs you are taking, including vitamins and herbal supplements. List any allergies, recent illnesses, and any medical issues you may have.

If you are pregnant or nursing, or if you have any of the following conditions, you should notify your doctor:

had a recent heart attack or myocardial infarction.
heart failure.
asthma.
chronic lung disease.
conduction abnormalities within the heart (such as AV block), aortic stenosis or other abnormalities with the valves of your heart.
any abnormality with the heart and lungs.

Also, notify your doctor if you have difficulty with your knees, hips, or keeping your balance, since this may restrict your ability to undertake the activity required for this surgery. You should dress comfortably and use walking shoes. On the day of the exam, do not apply any oil, lotion, or cream on your skin. If you take an inhaler for asthma or other breathing issues, bring it to the test and make sure the health care team overseeing your stress test is aware of your use.

Leave jewelry and accessories at home, or take them off before the exam. These things may obstruct the operation.

Caffeine (caffeinated and decaffeinated coffee, hot and cold tea, caffeinated soft drinks, energy drinks, chocolate, and caffeine-containing drugs, etc.) and smoking should be avoided for up to 48 hours before your test. More detailed instructions may be given to you by your doctor or radiologist.

You should not eat or drink anything after midnight on the day of your procedure, but you may continue to take medicines with tiny quantities of water unless your doctor instructs you differently. If you use beta-blocker or calcium channel blocker medication (Inderal, metoprolol, Norvasc, etc.), you should speak with your doctor about temporarily discontinuing it. If you have diabetes, consult your doctor about particular instructions for taking your diabetes medication on the day of the exam.

How Does The Procedure Work?

Ordinary x-ray tests use x-rays to generate a picture by passing them through the body. Radioactive compounds known as radiopharmaceuticals or radiotracers are used in nuclear medicine. This substance is usually injected into your bloodstream by your doctor. You can also ingest it or inhale it as a gas. The substance accumulates in the region under investigation, emitting gamma rays. Special cameras detect this energy and, with the assistance of a computer, generate images that show how your organs and tissues appear and work.

Heart scans are frequently conducted soon after patients have engaged in physical exercise (called a stress test) to increase blood flow throughout the heart, making any blockages of the coronary arteries easier to detect. These heart pictures are compared to heart imaging captured while the patient is at rest. Patients who are unable to exercise are given a medication that boosts blood flow to the heart.

What Will I Experience During & After The Procedure?

Most nuclear medicine treatments, with the exception of intravenous injections, are painless. Significant pain or adverse effects have been reported seldom.

When the technician puts the needle for the intravenous line into your vein, you will feel a little pin prick. During the radiotracer injection, you may feel a cool feeling move up your arm. There are no further negative effects in general.

You will be asked to exercise until you are either too exhausted or short of breath to continue, or if you encounter chest pain, leg pain, or other discomfort that makes you want to quit.

If you are given a prescription to boost blood flow because you are unable to exercise, the medicine may cause you to feel worried, dizzy, queasy, shaky, or short of breath for a short amount of time. Mild chest pain is also possible. Any symptoms that do arise usually go away as soon as the infusion is finished. In rare cases, if the medication's side effects are severe or cause you undue discomfort, additional medications can be used to counteract the effects.

It is critical to keep motionless during the examination. Nuclear imaging is not painful. However, having to stay motionless or in one position for lengthy periods of time might be uncomfortable.

Unless your doctor instructs you differently, you may continue your routine activities following your exam. Before you depart, a technician, nurse, or doctor will give you any particular instructions that are required.

The little quantity of radiotracer in your body will lose its radioactivity over time due to the natural process of radioactive decay. It may also flow out of your body through your urine or feces in the hours or days following the test. Drink lots of water to help flush the substance out of your system.

Benefits Vs. Risks

Benefits:

Nuclear medicine exams provide unique information that is often unattainable using other imaging procedures. This information may include details on the function and anatomy of body structures.
Nuclear medicine supplies the most useful diagnostic or treatment information for many diseases.
A nuclear medicine scan is less expensive and may yield more precise information than exploratory surgery.

Risks:

If you have coronary artery disease, you may have chest discomfort during activity or when a medication is administered for the stress test. Your heart, however, will be checked, and if required, medicine for your chest discomfort will be administered.
If your cardiologist suspects that you have life-threatening heart illness based on the test results, he or she may recommend same-day cardiovascular intervention.
Nuclear medicine exams provide a minimal radiation exposure since they employ a little dosage of radiotracer. This is sufficient for diagnostic examinations. As a result, the possible advantages of a screening exceed the very minimal radiation risk.
Nuclear medicine diagnostic procedures have been utilized by clinicians for more than six decades. There are no known long-term deleterious repercussions of such low-dose exposure.
Your doctor will carefully assess the advantages of nuclear medicine therapy against potential hazards. Prior to treatment, your doctor will go over the important risks with you and offer you the opportunity to ask questions.
Allergic responses to radiotracers are exceedingly infrequent and typically minor. Any allergies you may have should always be disclosed to the nuclear medicine professionals. Describe any issues you may have encountered during past nuclear medicine tests.
The radiotracer injection may produce little discomfort and redness. This should be resolved soon.
Women should always inform their doctor and radiological technician if they suspect they are pregnant or nursing. More information on pregnancy, nursing, and nuclear medicine exams may be found on the page Safety in X-ray, Interventional Radiology, and Nuclear Medicine Procedures.

Limitations of Cardiac Nuclear Medicine

Nuclear medicine procedures might take a long period. The radiotracer might accumulate in the region of interest for several hours to days. Furthermore, imaging might take many hours to complete. In rare circumstances, updated equipment can significantly reduce process time.

Nuclear medicine pictures may not have the same image resolution as CT or MRI images. Nuclear medicine scans, on the other hand, are more sensitive for a number of purposes. The functional information they provide is frequently inaccessible using conventional imaging techniques.

Clinical Diagnostic Procedures

1. Myocardial Perfusion SPECT (Single Photon Emission Computed Tomography):

SPECT imaging, also known as myocardial perfusion imaging, is a non-invasive technique used to evaluate the anatomy, function, and blood flow of the heart. A SPECT scan is acquired after a person has performed either treadmill exercise or a chemical/pharmacologic stress test.

Small quantities of radioactive chemicals are injected into a vein, and pictures of the heart are produced by a special camera. Cardiologists can use these pictures to measure blood flow to the heart muscle and find regions of dysfunctional heart muscle. SPECT scan data can be used to do the following:

determine coronary artery blockages (blood vessels of the heart).
assess whether a person has suffered a previous heart attack.
anticipate which people are at high risk of having a heart attack in the future.
evaluate the heart's health following cardiac bypass surgery or angioplasty (i.e. coronary artery stent placement).

2. Myocardial Perfusion PET:

Positron emission tomography (PET) myocardial perfusion imaging (MPI) is a type of imaging that displays how effectively blood flows to the heart muscle (myocardium). This test is performed to determine whether or not you have coronary artery disease.

A radioactive tracer (rubidium-82 or ammonia-13) is delivered into the patient's circulation and absorbed by the heart. The radiation emitted by the tracer is detected by a PET camera, which produces pictures of the heart. Two sets of pictures are taken: one after a rest injection and one following a stress test with persantine (dipyridamole) medicine, which simulates exercise.

3. Viability Imaging:

This examination is used to measure blood flow to the heart and is conducted entirely at rest (no stress component). A section of the heart muscle may be irreparably destroyed after a heart attack. Other areas of the heart, however, may be affected but not irrevocably destroyed. These locations are known as hibernation. Traditional imaging procedures, such as an echocardiography, cannot detect these sleeping portions of the heart muscle. The wounded heart areas are still alive, but they have not totally healed. As a result, cardiac function may be temporarily impaired.

A viability study would identify hibernating areas and provide your Cardiologist with further information about whether restoring blood flow to that part of the heart will enhance cardiac function.

4. MUGA (Multiple Gated Acquisition) Scan:

MUGA scans, also known as radionuclide cineangiograms (RNCA), are used to assess heart function by measuring how much blood is pumped out of the ventricles of the heart with each heartbeat (ejection fraction). A little quantity of a non-hazardous radioactive tracer solution is injected into a vein. This chemical binds to red blood cells, which are tracked as they pass through the heart by a special camera and computer. Based on the computer-generated pictures, the ejection percent is calculated.

A MUGA scan may be done to:

check how well the heart is pumping.
evaluate the size of the heart chambers.
check the pumping action of the lower ventricles.
find any abnormalities in the muscle walls of the ventricles.
see any abnormal movement of blood between chambers.
track the effect of certain kinds of chemotherapy drugs on the heart to make sure it is safe to continue with chemotherapy.
follow up and monitor the late side effects of cancer treatment.

5. Amyloid Pyrophosphate (PYP) Imaging:

Cardiac amyloidosis is a silent cause of heart failure or heart muscle weakening. Two forms of amyloid deposits can harm the heart: misfolded light chain and TTR (transthyretin) proteins. The differentiation between these two forms of cardiac amyloid is crucial in determining prognosis and treatment.

With a sensitivity and specificity of more than 97 percent, imaging with our SPECT cameras employing a tracer, Tc-99m PYP, is particularly accurate in detecting patients with TTR-type cardiac amyloid. This approach is especially beneficial in those for whom an invasive cardiac biopsy would be too risky.

Conclusion

Radiotracers, which are minuscule quantities of radioactive material, are used in nuclear medicine. Nuclear medicine is used by doctors to diagnose, assess, and treat a variety of disorders. Cancer, heart illness, gastrointestinal, endocrine, or neurological diseases, and other ailments are examples. Nuclear medicine examinations identify molecular activity. This provides them the ability to detect sickness in its early stages. They can also indicate whether or not you are responding to treatment.

Cardiac nuclear medicine can help in the diagnosis and assessment of coronary artery disease. It is also used to assess cardiomyopathy and identify potential cardiac damage caused by chemotherapy or radiation.

Nuclear medicine is a non-invasive treatment. With the exception of intravenous injections, it is normally painless. These tests employ radioactive chemicals known as radiopharmaceuticals or radiotracers to aid in the diagnosis and assessment of medical disorders.

To create unique perspectives, several imaging facilities mix nuclear medicine pictures with computed tomography (CT) or magnetic resonance imaging (MRI). Image fusion or co-registration are terms used by doctors to describe this process. Picture fusion enables the doctor to integrate and understand data from two separate exams on a single image. This results in more precise data and a more precise diagnosis. Both single photon emission CT/CT (SPECT/CT) and positron emission tomography/CT (PET/CT) machines are capable of performing both tests concurrently. PET/MRI imaging is a new imaging method. It isn't yet accessible everywhere.