The motivation to reproject gated blood pool SPECT data as planar data

Abstract

See related article, pp. 358-366In the current issue of the Journal, Wells et al, describe the results of deriving left ventricular (LV) ejection fraction (EF) values from planar radionuclide ventriculography (RNV) images that are not conventionally obtained via best septal view planar imaging, but rather by reprojecting gated blood pool SPECT data as planar RNV images.1 This is a topic of relevance for laboratories having SPECT-only cameras which are requested to perform gated blood pool scans.The most common reason for requesting RNV studies is to monitor possible cardiotoxicity caused by chemotherapeutic agents, such as the use of anthracycline-based chemotherapy to treat breast carcinoma in adults 2 and to treat Hodgkin disease (HD) in children. 3Serial RNV studies of EF during therapy provide a sufficient means of avoiding drug-induced congestive heart failure. 4 Some published guidelines for evaluating anthracycline cardiotoxicity in children advocate using both echocardiography and planar RNV studies.5 However, as treatment protocols can extend over several weeks or months, serial evaluations of EF are required, so that in general serial measurement of EF for children is performed by echocardiography, 5 but for adults is performed by planar RNV as it has been considered the best non-invasive EF method. 6 Subjects can be followed for 10 years or more because features of abnormal cardiac function will sometimes appear only many years later after completion of treatment. Planar EFs have long been the desired means of evaluating EFs because of the simplicity of the imaging conditions. Planar RNV imaging also provides diastolic filling parameters, which progressively deteriorate with anthracycline therapy, along with phase histograms and fairly robust visual images that can be used for quality control and to corroborate significant changes in the value of EF. In terms of acquiring images, it is relatively undemanding to identify the angle for the best planar septal LAO view. In terms of processing acquired data, automated algorithms are often successful at generating LV and background regions that are satisfactory, but when they require manual correction, the process of manually drawing a ROI to isolate LV activity is fairly straightforward. So, it is the simplicity of the imaging setup in combination with the simplicity of data analysis that facilitates reproducible EF values. It is considered feasible to obtain planar EF values with a reproducibility of 4-5%. 9,10 No test is perfect, and the shortcomings of planar RNV imaging have long been recognized. Because red blood cells in the lungs in front of and behind the LV contribute to cross talk counts, along with scattered radiation from other non-ventricular structures, counts in the ROI intended to isolate the LV may be contaminated. Subtracting average background counts as estimated using neighboring regions helps to correct for tissue cross talk, but the major impediment to planar RNV EF absolute accuracy is variability from one patient to another in the d...

Radiation reduction and faster acquisition times with SPECT gated blood pool scans using a high-efficiency cardiac SPECT camera

“…[17][18][19] Patients are often followed for a number of years after traditional anthracycline-based therapy requiring serial studies, 20,21 and newer classes of chemotherapeutic drugs often have a spectrum of cardiotoxic effects. Based on the degree of agreement between planar LVEF's and the 3-minute SPECT acquisition (no statistically significant difference), injected activity or imaging time could be decreased by 40%.…”