ASNC IMAGING GUIDELINES FOR NUCLEAR CARDIOLOGY PROCEDURES Instrumentation quality assurance and performance Kenneth J. Nichols, PhD, a Stephen L. Bacharach, PhD, b Steven R. Bergmann, MD, PhD, b Ji Chen, PhD, b S. James Cullom, PhD, b Sharmila Dorbala, MD, b Edward P. Ficaro, PhD, b James R. Galt, PhD, b Darcy L. Green Conaway, MD, b Gary V. Heller, MD, PhD, b Mark C. Hyun, CNMT, NCT, RT(N)(R), b Jonathan Links, PhD, b and Josef Machac, MD b INTRODUCTION The proper choice of equipment to acquire clinical data for specific purposes and a well-designed quality assurance (QA) program are both essential requirements for optimizing diagnostic accuracy. The following guide- lines are intended to provide appropriate means of assessing equipment function in conjunction with nu- clear cardiology imaging. Because equipment manufac- turers can vary considerably with the optimal manner in which to perform specific tests, this document should be used as guidelines only and is not intended to replace the recommendations by manufacturers of specific models of imaging equipment. A thorough and rigorous QA pro- gram is essential to ensure consistent high-quality imaging. EQUIPMENT Planar imaging. The small–field-of-view (FOV) scin- tillation camera is ideal for cardiac imaging. The 10-inch FOV covers the heart and shows enough surrounding area to evaluate lung uptake and to sample extracardiac back- ground activity. A 128  128 matrix over this FOV results in pixel spacing of about 2 mm. A camera with a 15-inch FOV should be zoomed using a magnification factor of 1.2 to 1.5 so that the pixel size is less than 3 mm and approximately equal to 2.5 or 2.0 mm. Energy windows should be symmetric about the photopeak. A window of 20% is standard for technetium 99m. With the improved energy resolution of many modern cameras, a 15% window can be used with little loss of primary gamma rays, with some improvement in contrast. The low energy and greater width of the thallium 201 photopeak require a wider window. An energy window setting of 30% is appropriate for the 70-keV peak of Tl-201 and a 15% energy window for the 167-keV peak. The absolute energy calibration can be unreliable at the low energy of Tl-201 falling at slightly different energy positions in the spectrum of different cameras. Thus energy peak and window settings should be established for each individual camera based on the energy spectrum display. 1 Parallel-hole collimation is standard. The low-en- ergy, high-resolution collimator is usually best for Tc- 99m, although some “all-purpose” collimators give ex- cellent results. Imaging with Tl-201 is usually best with the low-energy, medium-resolution (all-purpose) colli- mators because count statistics become limiting when using high-resolution collimators. The difference in me- dium- and high-resolution collimators is usually that the collimator depth (length of the collimator hole) is greater in high-resolution collimators. They have similar near- field resolution. The “high-resolution” collimator main- tains good resolution at a greater distance from the collimator face. The difference is more important in single photon emission computed tomography (SPECT) imaging, where the distance from patient to collimator is greater. 2 Collimators. The selection of which collimator to use is important to resultant image quality. A con- founding aspect of this selection is that collimators with the same name (eg, “general purpose”) vary in performance from one manufacturer to another. Table 1 gives approximate values for collimator specifica- tions. Refer to specific imaging protocols for appro- priate collimator selection. It is important to perform periodic assessment of collimator integrity, as failure to detect and correct for localized reduced sensitivity can generate uniformity-related artifacts, including reconstruction artifacts. 3,4 SPECT imaging. SPECT detectors are scintillation cameras mounted on a gantry. Many variables dictate the performance of a SPECT imaging system, including the number of detectors for a given device. Single-head cameras have been used widely for cardiac imaging. Adding more detectors is beneficial, since doubling the number of detectors doubles acquired counts, if all other variables remain fixed. For cardiac SPECT studies in From the Chair. a Member. b J Nucl Cardiol 2007;14:e61-78. 1071-3581/$32.00 Copyright © 2007 by the American Society of Nuclear Cardiology. doi:10.1016/j.nuclcard.2007.09.024 e61 Journal of Nuclear Cardiology November/December 2007