title: The effect of intravenous gadolinium-DTPA on diffusion-weighted imaging.
abstract: BACKGROUND
  Diffusion-weighted imaging (DWI) is usually performed before injection of intravenous paramagnetic contrast medium. Occasionally, it may be necessary to perform or to repeat DWI after such administration. Our purpose was to evaluate the effect of intravenous gadodiamide (Gd [DTPA-BMA]) on DWI.
  
  
  METHODS
  DWI was performed on 88 brain lesions immediately before, immediately after, and 5-10 min following the end of 0.1 mmol/kg Gd [DTPA-BMA] administration. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the lesions, and the SNRs of normal brain tissue were calculated on b=0 s/mm(2) and b=1,000 s/mm(2) DW images. Apparent diffusion coefficient (ADC) values of the lesions were measured on ADC maps. A paired t-test was used to determine the significance of differences between the values before and after administration of contrast medium.
  
  
  RESULTS
  The lesions consisted of 23 intraaxial and 11 extraaxial masses, 19 ischemic strokes, 15 intracranial hemorrhages and 20 demyelinating lesions. Images before and after contrast administration were not significantly different regarding SNRs and CNRs on DWI. This statement was also true for strongly enhanced lesions. However, ADC values significantly decreased after contrast medium injection on early post-contrast DWI in normal brain tissue (1%, P<0.049) and (3%, P<0.008) in lesions. By contrast, on late images, ADC values were normalized.
  
  
  CONCLUSIONS
  Contrast medium injection had significant and time-dependent effects on ADC values. Therefore, only pre-contrast and late DW images should be used in quantitative ADC studies.
authors: Department of Radiology, Turgut Ozal Medical Center, Inonu University Medical Faculty, Malatya 44280, Turkey. akfirat@inonu.edu.tr
authors: Ahmet Kemal
authors: AK
authors: Firat
authors: Bayram
authors: B
authors: Sanli
authors: Hakki Muammer
authors: HM
authors: Karakaş
authors: Gulnur
authors: G
authors: Erdem