R E V I E W A R T I C L E Single Photon Emission Computed Tomography as a diagnostic method in ischemic heart disease – basic technical aspects Jarosław Pleśniak Endocrinology and Isotope Therapy Clinic with Nuclear Medicine Unit, 109 Military Hospital, Szczecin, Poland Author’s address: Jarosław Pleśniak, Endocrinology and Isotope Therapy Clinic with Nuclear Medicine Unit, 109 Military Hospital, Szczecin, Poland, e-mail: jaroslawplesniak@gmail.com Summary Ischemic Heart Disease (IHD) poses an important diagnostic problem. Clinical picture of the disease is often atypical. SPECT is one of the main diagnostic tools in ischemic heart disease. Radioisotope study evaluates distribution of a radiopharmaceutical agent in the heart through a series of scintigraphic images taken by an external gamma camera. This article discusses the technical aspects of cardiac SPECT imaging, starting with a detection system, through image reconstruction, and ending with image filtering. Signature: © Pol J Radiol, 2011; 76(3): 49-52 Received: 2011.01.13 Accepted: 2011.05.31 Key words: SPECT • mTc-MIBI • myocardial perfusion PDF file: http://www.polradiol.com/fulltxt.php?ICID=881952 Background Nuclear medicine is one of the most important medical spe- cialties. It utilizes radioactive isotopes for diagnostic and therapeutic purposes, providing necessary information about the anatomy of a given organ, its position and func- tion [1,2]. Radioisotope diagnostics, due to its dynamic evo- lution and non-invasiveness became a recognized research method that provides a lot of prognostic data regarding car- diovascular events [3]. We owe the development of radioisotope imaging to a diag- nostic method that involves detection of the activity of a radioisotope accumulated over a diagnosed organ along consecutive lines, and uses a single detector. Single Photon Emission Computed Tomography (SPECT), available since 1960, is one of the basic tools in contem- porary diagnostics of ischemic heart disease (IHD) [4]. For the first time, single-headed SPECT was used for research in mid 70s, to carry out a topographic reconstruction of an image with a filtered back projection (FBP) algorithm [5]. Radiopharmaceuticals In single-photon tomography, radiopharmaceuticals emitting g photons are used. Emitters of g photons most commonly used for diagnosing ischemic heart disease are 99mTc and 201Tl isotopes, which accumulate in the myocar- dium [6] via active transport through cell membranes, pro- portionally to myocardial perfusion. The Tl-201 isotope has been used in the diagnostics of myo- cardial perfusion since 1975, and 99mTc – MIBI complex since mid 80s [7,8]. The 99mTc is used for this kind of diag- nostics due to its physical and biological properties, as well as cost and availability. The short half-life of 99mTc (Table 1) reduces patient’s exposition to ionizing radiation connect- ed with the application of diagnostic doses of radioactive technetium. SPECT Detection System The device used for g photon detection in radioisotope diag- nostics of ischemic heart disease is a rotating single- or dou- ble-headed gamma camera composed of a collimator, a crys- tal, photomultipliers, positioning system and other parts. The detector, while rotating around the patient, detects g photons that are perpendicular to the openings of the col- limator [9]. There are different shapes and sizes of collima- tors, but most often used are parallel collimators that look like a honeycomb. Gamma photons, after passing through the collimator, are absorbed by a scintillation crystal 49