title: A malaria diagnostic tool based on computer vision screening and visualization of Plasmodium falciparum candidate areas in digitized blood smears.
abstract: BACKGROUND
  Microscopy is the gold standard for diagnosis of malaria, however, manual evaluation of blood films is highly dependent on skilled personnel in a time-consuming, error-prone and repetitive process. In this study we propose a method using computer vision detection and visualization of only the diagnostically most relevant sample regions in digitized blood smears.
  
  
  METHODS
  Giemsa-stained thin blood films with P. falciparum ring-stage trophozoites (n = 27) and uninfected controls (n = 20) were digitally scanned with an oil immersion objective (0.1 µm/pixel) to capture approximately 50,000 erythrocytes per sample. Parasite candidate regions were identified based on color and object size, followed by extraction of image features (local binary patterns, local contrast and Scale-invariant feature transform descriptors) used as input to a support vector machine classifier. The classifier was trained on digital slides from ten patients and validated on six samples.
  
  
  RESULTS
  The diagnostic accuracy was tested on 31 samples (19 infected and 12 controls). From each digitized area of a blood smear, a panel with the 128 most probable parasite candidate regions was generated. Two expert microscopists were asked to visually inspect the panel on a tablet computer and to judge whether the patient was infected with P. falciparum. The method achieved a diagnostic sensitivity and specificity of 95% and 100% as well as 90% and 100% for the two readers respectively using the diagnostic tool. Parasitemia was separately calculated by the automated system and the correlation coefficient between manual and automated parasitemia counts was 0.97.
  
  
  CONCLUSIONS
  We developed a decision support system for detecting malaria parasites using a computer vision algorithm combined with visualization of sample areas with the highest probability of malaria infection. The system provides a novel method for blood smear screening with a significantly reduced need for visual examination and has a potential to increase the throughput in malaria diagnostics.
authors.affiliation: Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland.
authors.forename: Nina
authors.initials: N
authors.lastname: Linder
authors.affiliation: Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Turkki
authors.affiliation: Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland.
authors.forename: Margarita
authors.initials: M
authors.lastname: Walliander
authors.affiliation: Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mårtensson
authors.affiliation: Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
authors.forename: Vinod
authors.initials: V
authors.lastname: Diwan
authors.affiliation: Department of Computer Science and Engineering, University of Oulu, Oulu, Finland.
authors.forename: Esa
authors.initials: E
authors.lastname: Rahtu
authors.affiliation: Department of Computer Science and Engineering, University of Oulu, Oulu, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Pietikäinen
authors.affiliation: Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland.
authors.forename: Mikael
authors.initials: M
authors.lastname: Lundin
authors.affiliation: Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland; Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Lundin
mesh_terms: D006801:Humans; D008288:Malaria / Q000175:diagnosis / Q000469:parasitology*; D016778:Malaria, Falciparum / Q000175:diagnosis / Q000503:physiopathology; D018512:Parasitemia / Q000503:physiopathology; D010963:Plasmodium falciparum / Q000502:physiology*