European Radiology

, Volume 29, Issue 2, pp 759–769 | Cite as

Detection of suspected brain infarctions on CT can be significantly improved with temporal subtraction images

  • Thai AkasakaEmail author
  • Masahiro Yakami
  • Mizuho Nishio
  • Koji Onoue
  • Gakuto Aoyama
  • Keita Nakagomi
  • Yoshio Iizuka
  • Takeshi Kubo
  • Yutaka Emoto
  • Kiyohide Satoh
  • Hiroyuki Yamamoto
  • Kaori Togashi



To assess whether temporal subtraction (TS) images of brain CT improve the detection of suspected brain infarctions.


Study protocols were approved by our institutional review board, and informed consent was waived because of the retrospective nature of this study. Forty-two sets of brain CT images of 41 patients, each consisting of a pair of brain CT images scanned at two time points (previous and current) between January 2011 and November 2016, were collected for an observer performance study. The 42 sets consisted of 23 cases with a total of 77 newly developed brain infarcts or hyperdense artery signs confirmed by two radiologists who referred to additional clinical information and 19 negative control cases. To create TS images, the previous images were registered to the current images by partly using a non-rigid registration algorithm and then subtracted. Fourteen radiologists independently interpreted the images to identify the lesions with and without TS images with an interval of over 4 weeks. A figure of merit (FOM) was calculated along with the jackknife alternative free-response receiver-operating characteristic analysis. Sensitivity, number of false positives per case (FPC) and reading time were analyzed by the Wilcoxon signed-rank test.


The mean FOM increased from 0.528 to 0.737 with TS images (p < 0.0001). The mean sensitivity and FPC improved from 26.5% and 0.243 to 56.0% and 0.153 (p < 0.0001 and p = 0.239), respectively. The mean reading time was 173 s without TS and 170 s with TS (p = 0.925).


The detectability of suspected brain infarctions was significantly improved with TS CT images.

Key Points

• Although it is established that MRI is superior to CT in the detection of strokes, the first choice of modality for suspected stroke patients is often CT.

• An observer performance study with 14 radiologists was performed to evaluate whether temporal subtraction images derived from a non-rigid transformation algorithm can significantly improve the detectability of newly developed brain infarcts on CT.

• Temporal subtraction images were shown to significantly improve the detectability of newly developed brain infarcts on CT.


Multidetector computed tomography Stroke Brain infarction Computer assisted diagnosis Subtraction technique 



Apparent diffusion coefficient


Alternative free-response receiver operating characteristic


Computer-aided detection


Cerebral cortex lesion


Contrast-to-noise ratio


Diffusion-weighted imaging


Deep white matter lesion


Early hyperacute lesion


Fluid attenuation inversion recovery


Figure of merit


False positives per case


Graphics processing unit


Hyperdense artery sign


Jackknife alternative free-response receiver operating characteristic


Large deformation diffeomorphic metric mapping


Signal-to-noise ratio


Temporal subtraction



The author K.T. has received funding from Canon Inc.

Compliance with ethical standards


The scientific guarantor of this publication is Kaori Togashi.

Conflict of interest

The authors G.A., K.N., Y.I., K.S. and H.Y. declare relationships with the following companies: employees of Canon Inc.

All other authors have no conflicts of interest to disclose.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

• experimental study

• performed at one institution

Supplementary material

330_2018_5655_MOESM1_ESM.docx (930 kb)
ESM 1 (DOCX 929 kb)


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Copyright information

© European Society of Radiology 2018

Authors and Affiliations

  • Thai Akasaka
    • 1
    Email author
  • Masahiro Yakami
    • 1
    • 2
  • Mizuho Nishio
    • 1
    • 2
  • Koji Onoue
    • 1
  • Gakuto Aoyama
    • 3
  • Keita Nakagomi
    • 3
  • Yoshio Iizuka
    • 3
  • Takeshi Kubo
    • 1
  • Yutaka Emoto
    • 4
  • Kiyohide Satoh
    • 3
  • Hiroyuki Yamamoto
    • 5
  • Kaori Togashi
    • 1
  1. 1.Diagnostic Imaging and Nuclear MedicineKyoto University Graduate School of MedicineKyotoJapan
  2. 2.Preemptive Medicine and Lifestyle-Related Disease Research CenterKyoto University HospitalKyotoJapan
  3. 3.Medical Imaging System Development CenterR&D Headquarters, Canon Inc.TokyoJapan
  4. 4.Kyoto College of Medical ScienceKyotoJapan
  5. 5.Business Development Promotion CenterCorporate Planning Headquarters, Canon Inc.TokyoJapan

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