How to stop breathing: On the matter of getting respiratory motion under control

Excerpt

Respiratory motion is a recognized potential source of artifacts in single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI). Respiration leads to a complex three-dimensional movement of the heart predominantly in the cranio-caudal axis, potentially introducing anterior and particularly inferior wall blurring in SPECT MPI.1 Among other techniques, respiratory gating has repeatedly been proposed to address the issue.2,3 However, with conventional SPECT gamma cameras, implementation of respiratory gating is difficult and cumbersome due to the inherent step-and-shoot acquisition of the rotating detectors. The introduction of gamma cameras with cadmium-zinc-telluride (CZT)-based semiconductor detector technology may facilitate detection and correction of respiratory motion due to the combination of a stationary camera design without the need of rotating the detectors around the patient, and list-mode data acquisition. The beneficial properties of CZT cameras have also paved the way for other approaches such as prospective respiratory triggering, where acquisition is only performed at a certain inspiration level (e.g., during inspiration breath-hold only) thus eliminating respiratory motion altogether.4,5 However, such an approach inevitably leads to complication and prolongation of acquisition protocols. This may prove problematic particularly in view of the current strive to reduce radiation dose exposure by lowering the isotope doses because the latter inevitably leads to an increase in acquisition time.6 Thus, implementation of motion detection and correction algorithms may offer a more promising strategy for routinely controlling respiratory motion in nuclear cardiac imaging. These may come as software-based and purely data-driven solutions without any additional burden neither for the patient nor for the technician such as, for example, more complicated acquisition techniques, prolonged acquisition time hampering patient comfort and throughput, or even the need for increased radiotracer activity. …