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Radiation-induced microbleeds after cranial irradiation: evaluation by phase-sensitive magnetic resonance imaging
Tomohiko Tanino1, Yoshiko Kanasaki, Takatoshi Tahara
1Division of Radiology, Department of Pathophysiological and Therapeutic Science, School of Medicine, Tottori University Faculty of Medicine, Yonago 683-8504, Japan.
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.
Conclusion:
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.
Insights
Phase-sensitive imaging (PSI) detected more radiation-induced microbleeds after cranial irradiation than conventional MRI. These microbleeds were linked to higher radiation doses and appeared as early as 3 months post-treatment.
Area of Science:
- Radiology
- Neuroimaging
- Radiation Oncology
Background:
- Radiation-induced microbleeds are a known complication of cranial irradiation.
- The exact frequency, dose relationship, and latency period of these microbleeds require further clarification.
Purpose of the Study:
- To investigate the frequency, latency, and dose-response relationship of radiation-induced microbleeds.
- To evaluate the utility of phase-sensitive imaging (PSI) in detecting these changes after cranial irradiation.
Main Methods:
- Retrospective analysis of 34 patients undergoing cranial irradiation.
- Utilized magnetic resonance (MR) imaging with phase-sensitive imaging (PSI) at 3.0 T.
- Analyzed microbleed frequency across different radiation dose classes (5-15 Gy to >55 Gy).
Main Results:
- Microbleeds were detected in 47% of patients using PSI, compared to 21% with T2-weighted imaging.
- Microbleed frequency significantly correlated with higher radiation doses (>25 Gy).
- Latency ranged from 3 months to 9 years, with a mean of 33 months.
Conclusions:
- Radiation-induced microbleeds occur more frequently than previously reported.
- Phase-sensitive imaging (PSI) is more sensitive for detecting early vascular changes post-irradiation.
- Higher radiation doses are associated with an increased risk of microbleeds.
