IJCS | Volume 33, Nº2, March / April 2020

DOI: 10.5935/2359-4802.20190035 188 CASE REPORT International Journal of Cardiovascular Sciences. 2020; 33(2):188-191 Mailing Address: Angelica Mazzoletti Piazzale Spedali Civili,1. Postal Code: 25123, Brescia – Italy. E-mail: mazzolettiangelica@gmail.com Quantification of Myocardial Ischemia: Comparison between Myocardial SPECT and 13 NH 3 PET/TC Angelica Mazzoletti, 1 F rancesco Dondi, 1 Maria Gazzilli, 1 R affaele Giubbini 2 University of Brescia and Spedali Civili Brescia - Nuclear Medicine, 1 Brescia - Italy Azienda Socio Sanitaria Territoriale degli Spedali Civili di Brescia, 2 Brescia - Italy Manuscript received October 02, 2018; revised manuscript October 02, 2018; accepted November 26, 2018. Myocardial Ischemia/diagnosis; Coronary Artery Disease/diagnostic imaging; Tomography Emission- Computed Single-Photon/methods; Positron-Emission Tomography/method. Keywords Introduction Myocardial perfusion is a very important tool to diagnose and quantify hypoperfusion related to coronary artery disease (CAD). Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a widely available nuclear medicine imaging tool. Cardiac 13 N-ammonia positron emission tomography/computed tomography ( 13 NH 3 PET/CT) has increased its capability to provide quantitative measures of myocardial blood flow at rest and under stress, as well as of coronary flow reserve (CFR), in addition to better image quality. Case report A 61-year-old male patient with a history of hypertension, dyslipidemia andprevious atrial fibrillation underwent a kidney transplant in 2001 because of post- pyelonephritic chronic kidney disease. In 2007, in the presence of typical angina with anterior ST-depression, he underwent coronary angiography, which showed critical stenosis in the Left Anterior Descending Artery (LAD). He also underwent percutaneous transluminal coronary angioplasty (PTCA) and stenting. From 2007 to 2017 he remained asymptomatic and all cardiac examinations he underwent did not reveal any abnormalities. In January 2018, a treadmill stress test demonstrated ST-depression in the anterior and lateral leads that appeared only during the recovery and disappeared after 3 minutes. Therefore, he was submitted to a pharmacological stress-rest SPECT-MPI using a CZT gamma camera; an intravenous infusion of 400 μg regadenoson was performed, followed by the 99m Tc- tetrofosmin injection at 7 minutes. Stress acquisition started 15-25minutes after the radiotracer administration. Rest injectionwas administered 2 hours later, and images were obtained about 15-30 minutes later. Both stress and rest studies were acquired in list mode for 9 minutes using a gated 16 frame-per-cycle acquisition. The images showed a small hypoperfusion area in the lateral wall, while it was not possible to evaluate the inferior wall because of the presence of artifacts due to persistent diaphragmatic attenuation (Figure 1). The inducible ischemia in the LCX coronary territory was reported as 16%. CFR was also evaluated during the test : it was normal in the LAD and CDX territory, whereas it was 1.58 in the LCX territory. A subsequent 13 NH 3 PET/CT study was performed to better define the perfusion and coronary blood flow measurement of the left ventricular inferior wall (Figure 2). The examination was performed again at stress and at rest with 400 μg of regadenoson and the dose was 370 MBq of 13 NH 3 both at stress and at rest. The PET studies were acquired in 3D and list mode for 10 minutes, starting acquisition immediately before 13 NH 3 injection using a Discovery PET/CT 690 (GE Healthcare, Milwaukee, Wisconsin, USA). A low-dose CT attenuation correction (140 kV, 120-150 mA) was acquired for optimal imaging position on a CT scout scan and for attenuation correction. The examination result was an increased area of inducible ischemia in the LCX coronary territory of 46%. The global CFRwas also evaluated during the PET/