title: Radiation-induced microbleeds after cranial irradiation: evaluation by phase-sensitive magnetic resonance imaging with 3.0 tesla.
abstract: BACKGROUND
  Although there are many reports regarding radiation-induced microbleeds, its frequency, relation to dose and latency after radiation are not fully elucidated. The purpose of this study was to evaluate the frequency, latency, patient factors and dose relation of radiation-induced microbleeds after cranial irradiation using phase-sensitive magnetic resonance imaging (PSI) at 3.0 T.
  
  
  METHODS
  Retrospective evaluation of 34 patients (age range, 13-78 years; mean, 49 years; follow-up period, 3-169 months; mean 29 months) who had undergone cranial irradiation using magnetic resonance (MR) imaging including PSI was performed. Twenty-three patients received high-dose irradiation (44-60 Gy), and 11 patients received 24-30 Gy whole brain irradiation. When microbleeds were detected on MR imaging in these high-dose irradiation patients, dose distribution maps were reproduced by reviewing the clinical records. Then the irradiated areas were divided into 6 radiation-dose classes: regions > 55 Gy, 45-55 Gy, 35-45 Gy, 25-35 Gy, 15-25 Gy and 5-15 Gy. The frequency of microbleeds in each radiation-dose class was analyzed.
  
  
  RESULTS
  Microbleeds were detected in 7 (21%) of 34 patients on T2-weighted imaging, whereas they were detected in 16 (47%) of the 34 patients on PSIs. The frequency of microbleeds was higher than previously reported. The latency of radiation-induced microbleeds after radiation was 3 months to 9 years (mean, 33 months). In high-dose irradiation patients, the frequency of microbleeds significantly was associated with radiation dose. There were no foci that were observed in regions that had received < 25 Gy.
  
  
  CONCLUSIONS
  Radiation-induced microbleeds occurred more frequently in the present study than has been previously reported. PSI can be used to detect these vascular changes earlier than other conventional MR imaging techniques.
authors.affiliation: Division of Radiology, Department of Pathophysiological and Therapeutic Science, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Tanino
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Kanasaki
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Tahara
authors.forename: Koichi
authors.initials: K
authors.lastname: Michimoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kodani
authors.forename: Suguru
authors.initials: S
authors.lastname: Kakite
authors.forename: Toshio
authors.initials: T
authors.lastname: Kaminou
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Toshihide
authors.initials: T
authors.lastname: Ogawa
keywords: cranial irradiation; magnetic resonance imaging; radiation injury
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