A multigated acquisition (MUGA) scan is a popular type of radionuclide imaging test often performed on cancer patients or cancer survivors to screen for heart conditions or evaluate the effects on the heart from some cancer treatments. It is also used for patients with congestive heart failure as well as obese patients or ones who have chronic obstructive pulmonary disease to test for coronary artery disease. The MUGA scan works by generating video images of the lower chamber of the heart to determine if blood is pumping properly through the ventricles by measuring the ejection and injection fractions of the left ventricle. According to Walker et al., "Serial monitoring of LV ejection fraction (LVEF) using noninvasive cardiac imaging is the most important clinical diagnostic tool in early recognition of cardiac dysfunction." 
Simply put, the MUGA test works by injecting radioactive tracer into the vein of the patient, typically in their arm. The patient is placed under a gamma camera that detects the radiation released by the tracer and takes pictures of the gamma rays emitted when the radiopaque dye in the tracer decays. During the test the camera records between 14 to 64 points of the cardiac cycle, allowing the images to be studied like a video that helps doctors evaluate cardiac function. The images show the dye concentration in a particular area allowing the doctors to see damaged or decreased tissue and see which regions might not be contracting normally. The MUGA routinely estimates resting left ventricle ejection fraction (LVEF). 
There are two common types of MUGA tests, resting or stress, which are performed depending on the objective of the test. The resting test the patient lies stationary under the camera. During the stress MUGA, the patient is active during the scan. This test evaluates heart function during exercise and under stress. Many physicians promote the use of MUGA scanning because it is more objective with less observer variation making it more standardized and stable.  MUGA is also a noninvasive procedure and tends to be less expensive than an angiogram. It also has been found to have little to no side effects. Although MUGA has high reproducibility and low variability, some issues surrounding it could include problems of radiation and some studies have noted inaccurate LVEF measurements in patients with unknown arrhythmias. Because of this, sometime echocardiography is used as either an alternative form of imaging or confirmation of poor LVEF found by MUGA. 
Karkos et al. explain the mechanisms in which they used MUGA to test the subjects of the study's possible heart complications.  They state that MUGA scan uses "a standard ECG-gated equilibrium technique after in vivo labeling of red blood cells with 600-MBq technetium-99m pertechnetate after stannous pyrophosphate priming. A three-lead ECG was attached to the patient to give a distinct R wave, which was used to enable the trigger to the gated acquisition cycle. [...] Measurements were taken in the left anterior oblique 45-degree projection for 15 minutes with 16 frames per cardiac cycle on a 64 × 64 computer matrix [using the gamma camera]. The LVEF, calculated with this method, was considered as healthy when it was more than 50%." 
According to Walker et al., "The most common cardiotoxic side effect of the anthracycline drug class is a dose-dependent decline in ejection fraction, which may result in dilated cardiomyopathy."  Many of the side effects of radiation and chemotherapy appear asymptomatic until later in the course of the developing diseases. Because of this, MUGA scans are particularly useful and necessary in patients who have received cancer treatments. As rates of survival for cancer patients increases, MUGA scanning has become essential to evaluate survivors heart performance because some possible side effects of the cancer treatments. MUGA scanning can also be used earlier in cancer treatments to detect any unknown heart defects in the patients before treatment that oncologists would need to be aware of. 
© Abigail Lebovitz. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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