title: Susceptibility weighted imaging: differentiating between calcification and hemosiderin.
abstract: OBJECTIVE
  To present a detailed explanation on the processing of magnetic susceptibility weighted imaging (SWI), demonstrating the effects of echo time and sensitive mask on the differentiation between calcification and hemosiderin.
  
  
  METHODS
  Computed tomography and magnetic resonance (magnitude and phase) images of six patients (age range 41- 54 years; four men) were retrospectively selected. The SWI images processing was performed using the Matlab's own routine.
  
  
  RESULTS
  Four out of the six patients showed calcifications at computed tomography images and their SWI images demonstrated hyperintense signal at the calcification regions. The other patients did not show any calcifications at computed tomography, and SWI revealed the presence of hemosiderin deposits with hypointense signal.
  
  
  CONCLUSIONS
  The selection of echo time and of the mask may change all the information on SWI images, and compromise the diagnostic reliability. Amongst the possible masks, the authors highlight that the sigmoid mask allows for contrasting calcifications and hemosiderin on a single SWI image.
authors.affiliation: Master, Fellow PhD degree, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto da Universidade de São Paulo (FFCLRP-USP), Ribeirão Preto, SP, Brazil.
authors.forename: Jeam Haroldo Oliveira
authors.initials: JH
authors.lastname: Barbosa
authors.affiliation: PhD, Professor, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP), Ribeirão Preto, SP, Brazil.
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Santos
authors.affiliation: PhD, Professor, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto da Universidade de São Paulo (FFCLRP-USP), Ribeirão Preto, SP, Brazil.
authors.forename: Carlos Ernesto Garrido
authors.initials: CE
authors.lastname: Salmon
keywords: Calcification; Hemosiderin; Magnetic resonance imaging; Magnetic susceptibility; SWI