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Usefulness of Z-Score Mapping for Quantification of Extent of Hypoattenuation Regions of Hyperacute Stroke in Unenhanced Computed Tomography: Analysis of Radiologists' Performance

Takahashi, Noriyuki PhD; Tsai, Du-Yih PhD; Lee, Yongbum PhD; Kinoshita, Toshibumi MD, PhD; Ishii, Kiyoshi MD; Tamura, Hajime MD, PhD; Takahashi, Shoki MD, PhD

Journal of Computer Assisted Tomography: September/October 2010 - Volume 34 - Issue 5 - pp 751-756
doi: 10.1097/RCT.0b013e3181e66473
Neuroradiology

Objective: The purpose of this study was to evaluate the usefulness of z-score mapping method on neuroradiologists' performance in quantification of the extent of hypoattenuation regions of hyperacute stroke on unenhanced computed tomographic (CT) images by using the Alberta Stroke Programme Early CT Score system.

Methods: Twenty-one patients with infarction (<3 hours) were retrospectively selected. Five neuroradiologists interpreted CT images first without and then with z-score maps by using the Alberta Stroke Programme Early CT Score system. Their performances in the quantification of the extent of hypoattenuation were compared.

Results: Average accuracies for the quantification without and with the z-score maps were 82.6% and 86.6%, respectively (P < 0.0001). The average area under the receiver operating characteristic curve for detection of focal hypoattenuation significantly increased from 0.883 to 0.925 (P = 0.01) by use of z-score maps.

Conclusions: The use of z-score mapping method has the potential to help neuroradiologists quantify the extent of hypoattenuation regions of hyperacute stroke on unenhanced CT images.

From the *Department of Radiological Technology, Graduate School of Health Sciences, Niigata University, Niigata; †Department of Radiology, Research Institute of Brain and Blood Vessels-Akita, Akita; and ‡Department of Radiology, Sendai City Hospital; §Department of Noninvasive Diagnostic Imaging, Tohoku University Graduate School of Medicine; and ∥Department of Diagnostic Radiology, Tohoku University School of Medicine, Miyagi, Japan.

Received for publication January 5, 2010; accepted April 9, 2010.

Reprints: Noriyuki Takahashi, PhD, Department of Radiological Technology, Graduate School of Health Sciences, Niigata University, 2-746, Asahimachi-dori, Chuou-ku, Niigata, Niigata, 951-8518, Japan (e-mail: kiyurino1189@happy.odn.ne.jp).

This research was supported in part by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (Tokyo, Japan) through a grant-in-aid for Scientific Research (19591402).

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