Z-score mapping method for extracting hypoattenuation areas of hyperacute stroke in unenhanced CT.

RATIONALE AND OBJECTIVES The purpose of this study was to develop a z-score mapping method on the basis of a voxel-by-voxel analysis to visualize hypoattenuation areas of hyperacute stroke on unenhanced computed tomographic (CT) images. MATERIALS AND METHODS The algorithm of the developed method consisted of five main steps: anatomic standardization, the construction of a normal reference database, calculation of the z scores, the elimination of false-positive areas, and the extraction of hypoattenuation areas. The obtained z-score map was then superimposed on the original CT images for identifying hypoattenuation areas of hyperacute stroke on the unenhanced CT images. The method was applied to 21 patients with infarctions of the middle cerebral artery territory <3 hours after symptom onset. The performance of the method was evaluated using receiver-operating characteristic analysis. RESULTS Hypoattenuation regions could be significantly distinguished from normal regions by z-score values (P < .0001). The area under the receiver-operating characteristic curve for distinction between 68 hypoattenuation regions and 142 normal regions was 0.834. CONCLUSIONS The developed method has the potential to accurately indicate high-signal intensity areas corresponding to hypoattenuation areas on CT images in the hyperacute stage of stroke.

[1]  K. Furie,et al.  Acute brain infarct: detection and delineation with CT angiographic source images versus nonenhanced CT scans. , 2007, Radiology.

[2]  Noriyuki Takahashi,et al.  Adaptive partial median filter for early CT signs of acute cerebral infarction , 2007, International Journal of Computer Assisted Radiology and Surgery.

[3]  H Matsuda,et al.  Automated discrimination between very early Alzheimer disease and controls using an easy Z-score imaging system for multicenter brain perfusion single-photon emission tomography. , 2007, AJNR. American journal of neuroradiology.

[4]  Karl J. Friston,et al.  Spatial registration and normalization of images , 1995 .

[5]  J. Wardlaw,et al.  Early signs of brain infarction at CT: observer reliability and outcome after thrombolytic treatment--systematic review. , 2005, Radiology.

[6]  A. Demchuk,et al.  Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy , 2000, The Lancet.

[7]  D L Schriger,et al.  Cranial computed tomography interpretation in acute stroke: physician accuracy in determining eligibility for thrombolytic therapy. , 1998, JAMA.

[8]  J A Maldjian,et al.  Automated CT segmentation and analysis for acute middle cerebral artery stroke. , 2001, AJNR. American journal of neuroradiology.

[9]  R. Grubb,et al.  Guidelines for the Early Management of Patients With Ischemic Stroke: A Scientific Statement From the Stroke Council of the American Stroke Association , 2003, Stroke.

[10]  R. Koeppe,et al.  A diagnostic approach in Alzheimer's disease using three-dimensional stereotactic surface projections of fluorine-18-FDG PET. , 1995, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[11]  D. Tsai,et al.  Novel noise reduction filter for improving visibility of early computed tomography signs of hyperacute stroke: evaluation of the filter's performance—preliminary clinical experience , 2007, Radiation Medicine.

[12]  Y Lee,et al.  Improvement of detection of hypoattenuation in acute ischemic stroke in unenhanced computed tomography using an adaptive smoothing filter , 2008, Acta radiologica.

[13]  J. Ashburner,et al.  Nonlinear spatial normalization using basis functions , 1999, Human brain mapping.

[14]  Robert Adams,et al.  Guidelines for the early management of patients with ischemic stroke: 2005 guidelines update a scientific statement from the Stroke Council of the American Heart Association/American Stroke Association. , 2005, Stroke.