Multisection dynamic CT perfusion for acute cerebral ischemia: the "toggling-table" technique

Abstract

A new CT perfusion technique providing extended anatomic coverage was evaluated in 12 patients with suspected acute middle cerebral artery ischemia. With a multidetector CT scanner, scans were obtained in an alternating fashion at two distinct "toggling" table positions (two 1-cm sections each) during a 40-mL contrast agent bolus (approximately 5 seconds per image), and perfusion parameter maps were created. The CT perfusion results were compared with follow-up images. Nine patients showed focal perfusion abnormalities in at least one section, most commonly on mean transit time maps. Using a single table location would have underestimated or missed the involved tissue in most cases. In three of 12 patients, perfusion maps failed to delineate any abnormality. In two patients, perfusion and diffusion MR imaging confirmed the absence of perfusion abnormality and tissue injury, respectively. In one case, a small ischemic injury was revealed by diffusion MR imaging. By using the toggling-table approach, perfusion images can be obtained over an extended anatomic area and, thus, reveal the presence and the extent of presumed tissue injury.

fig 1.

The CT perfusion maps of a patient with an acute onset of a right-sided weakness (patient 2 in the Table). Noncontrast CT scan was negative for acute infarct signs. The infarcted area is covered only on the most superior location (sections 3 and 4) of the four sections from the toggling-table technique (arrows) and would have been missed if a single section location (eg, at the level of the third ventricle) would have been chosen