European Radiology

, Volume 28, Issue 9, pp 3936–3942 | Cite as

Ischemic stroke enhancement using a variational model and the expectation maximization method

  • Allan Felipe Fattori Alves
  • Rachid Jennane
  • José Ricardo Arruda de Miranda
  • Carlos Clayton Macedo de Freitas
  • Nitamar Abdala
  • Diana Rodrigues de PinaEmail author
Computed Tomography



In order to enable less experienced physicians to reliably detect early signs of stroke, A novel approach was proposed to enhance the visual perception of ischemic stroke in non-enhanced CT.


A set of 39 retrospective CT scans were used, divided into 23 cases of acute ischemic stroke and 16 normal patients. Stroke cases were obtained within 4.5 h of symptom onset and with a mean NIHSS of 12.9±7.4. After selection of adjunct slices from the CT exam, image averaging was performed to reduce the noise and redundant information. This was followed by a variational decomposition model to keep the relevant component of the image. The expectation maximization method was applied to generate enhanced images.


We determined a test to evaluate the performance of observers in a clinical environment with and without the aid of enhanced images. The overall sensitivity of the observer’s analysis was 64.5 % and increased to 89.6 % and specificity was 83.3 % and increased to 91.7 %.


These results show the importance of a computational tool to assist neuroradiology decisions, especially in critical situations such as the diagnosis of ischemic stroke.

Key Points

• Diagnosing patients with stroke requires high efficiency to avoid irreversible cerebral damage.

• A computational algorithm was proposed to enhance the visual perception of stroke.

• Observers’ performance was increased with the aid of enhanced images.


Stroke Brain Algorithms Tomography Early diagnosis 



Alberta Stroke Program Early CT Score


Central Processing Unit


Computed tomography


Digital Imaging and Communications in Medicine


Evaluation 1


Evaluation 2


False negative


False positive


Hounsfield units


Magnetic resonance image


Non-enhanced computed tomography


Observer 1-6


True Negative


True Positive


Variational Model



The authors wish to thank all clinical personnel of the Botucatu Medical School Radiodiagnostic facility. We also thank the Laboratories I3MTO from University of Orleans and LAFAR from São Paulo State University.


Financial support was provided by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).

Compliance with ethical standards


The scientific guarantor of this publication is José Ricardo de Arruda Miranda from São Paulo State University, Brazil.

Conflict of interest

The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was not required for this study because all CT scans used were retrospective and no confidential patient information was used throughout this study.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

• diagnostic or prognostic study

• performed at one institution

Supplementary material

330_2018_5378_MOESM1_ESM.docx (39 kb)
ESM 1 (DOCX 38 kb)


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Copyright information

© European Society of Radiology 2018

Authors and Affiliations

  • Allan Felipe Fattori Alves
    • 1
  • Rachid Jennane
    • 2
  • José Ricardo Arruda de Miranda
    • 1
  • Carlos Clayton Macedo de Freitas
    • 3
  • Nitamar Abdala
    • 4
  • Diana Rodrigues de Pina
    • 5
    Email author
  1. 1.Instituto de Biociências de Botucatu, Departamento de Física e BiofísicaUNESP—Universidade Estadual PaulistaBotucatuBrazil
  2. 2.Laboratory I3MTO – University of OrleansOrléansFrance
  3. 3.Departamento de Neurologia, Psicologia e Psiquiatria, Faculdade de Medicina de BotucatuUNESP—Universidade Estadual PaulistaBotucatuBrazil
  4. 4.Departamento de Diagnóstico por ImagemEscola Paulista de Medicina – UNIFESPSão PauloBrazil
  5. 5.Departamento de Doenças Tropicais e Diagnóstico por Imagem, Faculdade de Medicina de BotucatuUNESP—Universidade Estadual PaulistaBotucatuBrazil

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