Nuclear Medicine 4: Radionuclide Ventriculography (MUGA Scan)

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Clinical Practice Keywords Stannous agent/Cardiac cycle/Cardiotoxicity/Ejection fraction Review This article has been Nuclear medicine double-blind peer reviewed In this article... ● Principle of radionuclide ventriculography, also known as a MUGA scan ● How radionuclide ventriculography is used to monitor cardiotoxicity ● Precautions required with, and around, patients who undergo a MUGA scan

Nuclear medicine 4: radionuclide ventriculography (MUGA scan)

Key points Authors Joseph Purden and Faye Morton are lecturers in medical physics technology, Radionuclide College of Human and Health Sciences, Swansea University. ventriculography uses repeat images Abstract Nuclear medicine provides imaging modalities that can be used to observe of the heart to physiological processes in the human body, particularly in the bones, heart, lungs, monitor ejection renal system and brain. This fourth article in a five-part series explains how fraction radionuclide ventriculography – also called a multiple-gated acquisition (MUGA) scan – works and what precautions need to be taken with and around patients undergoing It is also called this investigation. multiple-gated acquisition (MUGA) Citation Purden J, Morton F (2019) Nuclear medicine 4: radionuclide ventriculography scan because of the (MUGA scan). Nursing Times [online]; 115: 6, 63-64. imaging technique that is used adionuclide ventriculography Imaging – during which the patient is The ejection fraction uses images of the heart to in a supine position with their arms above is often used as a determine the ejection fraction their head – is undertaken approximately measure of R(Box 1). The ejection fraction is 20 minutes after the radioactive element chemotherapy- often used as a measure of the cardiotox- has been injected. A three-lead electrocar- induced icity that can be caused by some chemo- diogram (ECG) triggers the acquisition of cardiotoxicity therapy agents (Metcalfe, 2005). As an images timed to systole and diastole. Each example, radionuclide ventriculography image takes approximately 10-15 minutes Precautions to avoid can be used to monitor the ejection frac- to acquire (Hesse et al, 2008). Images are radioactive tion of patients who are receiving the mon- obtained from the left anterior oblique contamination are oclonal antibody trastuzumab as part of a view (or projection) and additional projec- needed for 24 hours chemotherapy protocol for breast cancer tions are sometimes used (Fig 1). after a MUGA scan (Chavez-MacGregor et al, 2015). The ECG trace is split at each R wave Radionuclide ventriculography is also into 24 segments. The imaging system called a multiple-gated acquisition assigns the counts detected during each of (MUGA) scan because of the imaging tech- the 24 segments of the cardiac cycle to cor- nique used. responding ‘bins’. Data from each bin is compiled to produce an image of the heart How does it work? in each phase of the cardiac cycle. A radioisotope (see part 1) is injected into Emissions from the radioisotope are the patient intravenously, travels in the detected by a gamma camera, which allows circulation and moves into the red blood nuclear medicine professionals to see the cells. To ensure that it remains in the red outline of the left ventricle. Views of the blood cells, a stannous (tin) agent is heart are taken to work out the volume of injected into the patient 10-30 minutes blood it contains during diastole and sys- before the procedure. This is taken up by tole. The difference between the two is the the red blood cells and makes them ‘sticky’, ejection fraction. A baseline ejection frac- so they are able to ‘trap’ the radioisotope tion is calculated and repeat investigations when it is administered. are performed.

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Fig 1. ProjectionsLeft anterior oblique used view in radionuclideAnterior ventriculography view Left lateral view Left anterior oblique view Anterior view Left lateral view Left anterior oblique view Anterior view Left lateral view

Left Left Left ventricle Left ventricle Left ventricleLeft ventricle Right ventricle ventricle Rightventricle 1 Right 1 1 ventricle 1 1 ventricle 4 2 1 2 4 5 4 2 2 4 5 4 2 3 2 4 5 3 3 3 2 1 3 1 Right 3 3 2 1 3 Right 3 2 Rightventricle Right Rightventricle Left ventricle Right ventricle ventricle Left ventricle ventricle ventricleLeft ventricle 1. Basal 1. Antero-lateral 1. Posterior 1. Basal 1. Antero-lateral 1. Posterior 1.2. Basal Posterior-lateral 1.2. Antero-lateral Apical 1.2. Posterior Inferior 2. Posterior-lateral 2. Apical 2. Inferior 2.3. Posterior-lateral Inferior-apical 2.3. Apical Inferior 2.3. Inferior Apical 3. Inferior-apical 3. Inferior 3. Apical 3.4. Inferior-apical Septal 3. Inferior 3.4. Apical Antero-septal 4. Septal 4. Antero-septal 4. Septal 4.5. Antero-septal Basal 5. Basal 5. Basal 1a. Left anterior oblique view 1b. Anterior view 1c. Left lateral view

Source: Adapted from Hesse et al (2008)

PreparingSource: patients Adapted from Hesse et al (2008)Radiation protection members of staff should not care for Source: Adapted from Hesse et al (2008) Patients whoSource: are about Adapted to undergofrom Hesse a MUGA et al (2008) Patients should be encouraged to drink patients who have just had a MUGA scan, scan usually go to the nuclear medicine and urinate often after the scan (unless and all staff need to take extra care to department. If they have reduced mobility, contraindicated), to help clear the radiop- reduce their own exposure to radiation. it is useful to inform the department harmaceutical from their system. After 24 hours, normal staff rotas and beforehand, to ensure the correct protocols If samples of blood, urine or faeces need standard care protocols can be resumed. NT are adhered to during imaging. There is to be collected from a patient in the minimal preparation and patients should: 24 hours after a MUGA scan, nurses should References (2015) Cardiac l Chavez-MacGregor M et al Follow their normal diet; take extra care by: monitoring during adjuvant trastuzumab-based l Take their normal medications. l Wearing gloves, an apron and shoe chemotherapy among older patients with breast A cannula is usually inserted before the coverings; cancer. Journal of Clinical Oncology; 33: 19, procedure so the stannous agent and radi- l Using absorbent pads to clean up any 2176-2183. Foley TA et al (2012) Measuring left ventricular oisotope can be administered using one spillages. ejection fraction: techniques and potential pitfalls. injection site. If possible, it is advisable to either per- European Cardiology Review; 8: 2, 108-114. In cases of severe urinary incontinence, form sample collection before the investi- Hesse B et al (2008) EANM/ESC guidelines for radionuclide imaging of cardiac function. European it is advised that patients have a catheter in gation or more than 24 hours after it. Journal of Nuclear Medicine and Molecular situ for the duration of the procedure to Patients should not have close contact Imaging; 35: 4, 851-885. avoid contamination of the camera by with young children or pregnant women – Metcalfe MJ (2005) The cardiovascular system. In: spills of radioactive urine. The catheter the two groups most at risk from radiation Sharp PF et al (eds) (2005) Practical Nuclear Medicine. London: Springer Verlag. bag should be emptied regularly to prevent – for 24 hours after administration of the Mininni NC, Tasota FJ (2003) Measuring injection an accumulation of radioactive urine. radiopharmaceutical. Ideally, pregnant fraction with a MUGA scan. Nursing; 33: 7, 26.

Box 1. Ejection fraction CLINICAL The ejection fraction is the volume of blood ejected from the left ventricle during SERIES ‘Nuclear medicine’ series each heartbeat. It indicates how strong the left ventricle is (Hesse et al, 2008). A Part 1: Technique, indications Mar good ejection fraction is ≥55% (Mininni and Tasota, 2003). and the nurse’s role It is calculated as follows: Bit.ly/NTNuclear1 Part 2: Bone scintigraphy Apr EDV-ESV Ejection fraction (%) = x 100 Bit.ly/NTNuclear2 EDV Part 3: Myocardial perfusion imaging May Bit.ly/NTNuclear3 EDV = end diastolic volume; ESV = end systolic volume. Part 4: Radionuclide ventriculography Jun

Part 5: Ventilation/perfusion scintigraphy Jul Source: Foley et al (2012) PETER LAMB PETER

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