Seung Hun Sheen
Intravenous flat detector CT (IV FDCT) is an emerging technology for generating CT-like images from a rotating flat panel detector in a biplane angiographic system. Clinical applications of IV FDCT have included the early detection of cerebral infarction1 and periprocedural complications, and a follow-up tool for intracranial stenting.2
The Artis zee Biplane system (Siemens, Erlangen, Germany) was introduced at our hospital in December 2008. After consultation with Professor Ito Yasushi (Niigata University), we have investigated the feasibility of IV FDCT in measuring intracranial arterial3 and extracranial carotid stenosis.4 With the help of my clinical fellow Jin Sue Jeon, and in collaboration with neuroradiologists, we have reported that IV FDCT has a sensitivity of 97.6%, specificity of 96.9%, and negative predictive value (NPV) of 96.9% for identifying ≥ 50% stenosis, with DSA as the reference value. Moreover, IV FDCT showed a high reliability for detecting severe intracranial stenosis ≥ 70% (sensitivity of 91.9%, specificity of 98.2%, and NPV of 97.4%) and stenosis length (Spearman rank correlation test, r=-0.12; P=.13).
Among the various radiologic methods used to evaluate patients suspected of acute cerebral infarction, we prefer MRI to evaluate ischemic penumbra and IV FDCT to obtain anatomic information such as the degree and length of the stenosis, occlusion level, collateral circulation, calcification, and patency of the anterior and posterior communicating arteries. Consequently, rapid assessment and prompt endovascular management can be achieved.
We have been asked about the feasibility of IV FDCT in evaluating vasospasm after the obliteration of a ruptured aneurysm since our report was first published. The reason being early detection and subsequent endovascular intervention seem to be beneficial particularly in patients with SAH. Although IV FDCT has not been effective in evaluating clipped or coiled aneurysms such as parent artery patency and residual neck presence due to metal artifacts in some studies,5, 6 its role in the accurate detection, measurement, and treatment of vasospasms still remains undetermined. From our experience, IV FDCT appears to have a high accuracy in detecting severe vasospasm when using reconstructed images in various directions (Figure). The feasibility of IV FDCT to measure vasospasm is now under investigation at our institute.
Concerns remain about image degradation because of beam-hardening and motion artifacts. Further study for a new algorithm to reduce such concerns is needed. In addition, available software to show physiological parameters, including cerebral blood flow, mean transit times, and time to peak as well as cerebral blood volume, is required.
