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In the areas of biology and medicine, nuclear tracers are usually radiopharmaceutical products whose molecules contain a radioactive element - a marker.

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Patient Information on Nuclear Imaging

Nuclear Medicine (NM) Nuclear medicine scans are safe and non-invasive

There is some risk involved in having a stress test especially if you have severe heart disease. Our staff is very experienced performing cardiac stress tests. Your vital signs will be monitored very carefully during the entire test. The test will be stopped if the physician believes that your safety may be compromised. We are prepared to handle any emergencies should they occur.

The radioactive agents are used to show the blood flow to your heart. These tracers have been used for over thirty years and are considered very safe. The amount of radioactivity that you receive is about the same amount you would normally be exposed to over a period of 1-2 years just from background radiation. The only restriction to this test would be if there is any possibility you may be pregnant, currently trying to become pregnant, or nursing.

What is a Nuclear Cardiology Stress Test

Medical tests of this kind involve administering a radioactive tracer, chosen carefully for its ability to follow a metabolism or provide information about the working of a given organ. The tracer can be an individual atom (for instance iodine 123), a marked molecule (such as a diphosphonate marked with technetium 99m), an hormone or even an antibody marked with an isotope. The isotope has to be chemically attached to the relevant molecule without altering its properties and metabolism. The bond must also be a solid one in order to follow the molecule and not an eventually shaken off radioactive atom.

So-called 'radiopharmaceutical' products (molecules containing radioactive isotopes) are generally inserted intravenously, though some can also be inhaled or even swallowed.

When it comes to internal body scans, the game is to localize the radiopharmaceutical product inside the body from an external detection while exposing the body to a minimal dose of radiation. Gamma emitters are therefore the ideal radioelements : gamma rays are relatively low ionisers and simultaneously penetrative enough to be detected outside of the body. Another important property of the radioelement is its half-life, which has to be long enough to follow the biological process in question and yet short enough to avoid any unnecessary exposure.

Technetium 99m is by far the most commonly used radioelement (as it is used in 80-90% of all scintigraphy scans), as it allows for the exploration of numerous body parts and emits only rays whose energy (of 140 ) is well adapted to the gamma-camera detectors. Beta-plus () emitters are used in the field of 'positron emission tomography' (PET scans). In the field of metabolic therapy, beta-minus emitters are used to deliver a highly localized dose of radiation.

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When you first come in, a brief medical history will be taken by a technologist or nurse. An intravenous line (IV) will be started. A radioactive dose may be injected and rest images may be done if you having a dual isotope test or a one day Sestamibi test. These images take about 15-20 minutes using a
specialized gamma camera. A nurse will then put on EKG leads on your chest to monitor your heart.

If a patient cannot walk on treadmill very fast due to a physical reason or has certain EKG abnormalities such as a left bundle branch block, the physician may order a low level treadmill adenosine stress test or an adenosine stress test without exercising. If a patient has severe asthma or very significant lung disease, the physician may order a dobutamine stress test.

Adenosine is a pharmacological agent that will cause dilation of all the blood vessels in the body. You may experience a flushing feeling, chest pressure and/or shortness of breath, similar to exercising. This part only takes 6 minutes and any of the side effects resolve quickly after the infusion is done. It has been found that walking very slowly on a treadmill during the 6 min adenosine infusion decreases the severity of any side effects and optimizes the heart images. Your blood pressure and EKG will be monitored by a nurse and a cardiologist. The radioactive material, 99mTc Sestamibi will be injected into the IV by the Nuclear Medicine Technologist at the mid point of the adenosine infusion. After the stress test is over, you will receive a beverage and have a break before the stress images are acquired.

Dobutamine is pharmacological agent that causes the heart rate to rise and the blood pressure to increase. This test is done with the patient lying down. Your blood pressure and EKG will be monitored by a nurse and a cardiologist. The dobutamine will be slowly infused into your IV, increasing the amount every three minutes. When your heart rate has reached a certain target determined by your age, the Nuclear Medicine Technologist will inject the 99mTc Sestamibi material into the IV. The infusion will continue for another minute. This part usually takes a total of 6-12 minutes.

After the stress test is over, you will receive a beverage and have a break before the stress images are acquired. Three EKG patches will be left on your chest and they will be wired up to acquire “gated” images to analyze the wall motion and left ventricular ejection fraction of the heart.

The stress images will be compared to rest images to look at the blood flow to the heart. If a significant blockage is present in your coronary arteries a perfusion defect will show. If there is a defect in the stress but the rest images look normal, this is called ischemia. If there are matching defects in both the stress and rest, an infarction has occurred. If there are no defects then the study is normal.

Nuclear medicine uses radioactive substances (radioisotopes) incorporated into pharmaceuticals. These "radio-pharmaceuticals" or "radio-tracers" are designed to target specific tissues and organs, allowing the delivery of the radioactive substance to specific areas of the body.