Cardiac Nuclear Medicine

 Cardiac SPECT Perfusion image showing the blood flow pattern in the walls of the heart at rest and during exercise

What is Cardiac Nuclear Medicine and How Does Nuclear Imaging Help People with Heart Disease?

 

Like many nuclear medicine procedures, cardiac molecular imaging involves the injection of a radioactive label, or “radiotracer”, which circulates into the heart. Using either a PET or SPECT scanner, the patient then undergoes a scan of the heart that detects the radioactive signal from the heart and produces a detailed three-dimensional image. A Nuclear Medicine physician can then determine the amount of blood flow (perfusion) that the walls of the heart are receiving, whether the cells in the heart are functional and healthy (viability), and whether the heart has suffered permanent damage from a prior heart attack (myocardial infarction).

When evaluating the blood flow (perfusion) to a patient’s heart, it is very useful to evaluate the blood flow while the heart is working faster and harder (under “stress”) and compare the blood flow to when the heart is beating normally (at “rest”). When evaluating the functional (viability) status of the heart, it is not necessary to test the heart under stress.

Depending on your personal medical history and clinical situation, your physician may order any of the following exams for you:

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What are SPECT and PET Imaging?

When imaging the heart in Nuclear Medicine, there are two types of scanners: SPECT and PET scanners. Single Photon Emission Computed Tomography (SPECT) imaging is well established and routinely used and is the primary functional imaging tool used to evaluate the heart. Positron Emission Tomography (PET) offers higher resolution and imaging speed and is becoming more widely available for cardiac imaging.

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Cardiac SPECT Perfusion:
What should I expect and how do I prepare for my exam?


3-D image of the blood flow and functional status of the heart at rest and stress using Cardiac SPECT Perfusion imaging

You have been scheduled for a diagnostic exam to evaluate the blood supply to your heart. You will receive up to 2 injections of a radioactive tracer that flows in the blood vessels of your heart in order to create 2 images of the blood supply to your heart, one image while resting and a second image after cardiac stress.

A small intravenous catheter will be placed in your arm. Imaging is performed twice, once at rest and a second after cardiac stress. The cardiac stress test is accomplished either by walking/jogging on a treadmill or by using a drug to challenge your heart. In total, the exam will take about 3-4 hours.

For Patients Scheduled to Perform a TREADMILL Stress Test

If you are physically unable to walk/jog on a treadmill, please alert the Nuclear Medicine staff to allow for an alternative (e.g. switch to a cardiac stress test using a drug). Once on the treadmill, the speed and incline will be gradually increased until you have symptoms or fatigue, pain, or cardiac abnormality occurs.

For Patients Scheduled to Perform a DRUG (PHARMACOLOGIC) Stress Test

A drug, either regadenoson (Lexiscan) or adenosine, will be administered as an injection. Regadenoson or adenosine dilates the blood vessels that supply your heart. The medicine may cause a sensation of flushing, shortness of breath, a pounding in your head, dizziness or chest pain in some patients. If necessary, you will be given an intravenous medicine called aminophylline which will reverse the side effects and the test will be stopped.

Risks and Discomfort

If you have any additional questions later, any of the Stanford Nuclear Medicine faculty can be reached at 725-4711 and will be happy to answer your questions.

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Cardiac PET Perfusion:
What should I expect and how do I prepare for my exam?


3-D image of the heart using a combination of PET and CT Angiography showing the viability of the heart (orange/red color) and anatomy of the cardiac vessels (black and white)

You have been scheduled for a diagnostic exam to evaluate the blood supply to your heart. You will receive up to 2 injections of a radioactive tracer that flows in the blood vessels of your heart in order to create 2 images of the blood supply to your heart, one image while resting and a second image after cardiac stress.

A small intravenous catheter will be placed in your arm. Imaging is performed twice, once at rest and a second after cardiac stress. The cardiac stress test is accomplished either by walking/jogging on a treadmill or by using a drug to challenge your heart. In total, the exam will take about 3-4 hours.

A drug, either regadenoson (Lexiscan) or adenosine, will be administered as an injection. Regadenoson or adenosine dilates the blood vessels that supply your heart. The medicine may cause a sensation of flushing, shortness of breath, a pounding in your head, dizziness or chest pain in some patients. If necessary, you will be given an intravenous medicine called aminophylline which will reverse the side effects and the test will be stopped.

Risks and Discomfort

If you have any additional questions later, any of the Stanford Nuclear Medicine faculty can be reached at 725-4711 and will be happy to answer your questions.

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Cardiac PET Viability:
What should I expect and how do I prepare for my exam?

You have been scheduled for a Cardiac PET Viability exam. This exam performed in conjunction with Cardiac SPECT perfusion or Cardiac PET perfusion imaging during the same appointment. Depending your clinical situation, the cardiac stress test (e.g. treadmill exercise) may not be required.

Prior to Your Appointment

Please do not eat or drink flavored liquids for 8 hours prior to the scheduled exam (it is OK to take water and medications). If you are a diabetic and are injecting greater than 100 units of regular insulin per day, please contact the Nuclear Medicine staff and your Cardiologist prior to the appointment, we may need to make modifications to the imaging protocol.

During the Appointment

During the appointment, you will be injected with dextrose (sugar water) and, possibly, insulin to help improve the image quality of your heart. The radioactive label that we inject, called FDG, is a form of sugar and used to assess the function of the heart and whether the heart tissue is alive and using sugar for energy to pump blood. Once the FDG is injected, you will rest for approximately 45 minutes prior to imaging in the PET/CT scanner.

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Cardiac PET Sarcoid:
What should I expect and how do I prepare for my exam?

Night Before Appointment

  1. The night before your scan, at your regular dinnertime start a high fat, high protein no carbohydrate diet and avoid sugars (glucose, fructose, sucrose, etc). Your choice of breakfast and dinner can include:
    1. Fatty unsweetened foods (fried in butter or olive oil, broiled, but not grilled):
    2. Chicken, turkey, fish, meats (steak, ham etc), meat only sausages, fried eggs, bacon, scrambled eggs prepared without milk, omelet prepared without milk or vegetables, fried eggs and sausages, fried eggs and bacon, hotdogs (plain -without the bun), hamburgers (plain - without the bun or vegetables)
  2. Please do not eat the following foods:
    1. Milk, cheese, bread, bagels, cereal, cookies, toast, pasta, crackers, muffins, peanut-butter, nuts, fruit juice, potatoes, candy, fruit, rice, chewing gum, mints, cough drops, vegetables, beans, alcohol
  3. You should drink clear liquids without milk or sugars
    1. Diet Pepsi or Diet Coke, Coffee without milk or sugar, Can use sweet n’ low, nutra-sweet or equal, Tea without milk or sugar.

Morning/Day of Appointment

  1. You should have breakfast 3 - 5 hrs before your scan, even if you scan is at 7:20 a.m. Do not skip breakfast. Stick to the high fat, high protein, no carbohydrate diet, as listed above. Then do not eat anything else until after your scan. You may drink water (or diet Coke or diet Pepsi) up to the time of your scan. If your scan is scheduled for the late afternoon, you can also have a high fat, high protein, no carbohydrate meal for lunch 3-5 hours prior to your scan.
  2. If you are going to have a separate CT or MRI study, please make sure it is scheduled after your PET/CT scan. All other studies for which you need to be NPO (not eat beforehand) need to be scheduled for another day.

Insulin Dependent Diabetics

If you are an insulin dependent diabetic (require injected insulin), you should schedule your appointment in the early afternoon. You should have breakfast at least 3 hours before your study (using the menu above), and take your usual insulin. Do not eat anything else until after your scan. If that is not possible, then please call and discuss your diabetic control with us.

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