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Radiat Oncol. 2013 Mar 7;8:54. doi: 10.1186/1748-717X-8-54.

Magnetic resonance spectroscopic study of radiogenic changes after radiosurgery of cerebral arteriovenous malformations with implications for the differential diagnosis of radionecrosis.

Author information

  • 1Department of Neurosurgery, University of Bonn Medical Center, Sigmund-Freud-Str, 25, Bonn 53105, Germany. Jan.Bostroem@ukb.uni-bonn.de

Abstract

BACKGROUND:

The incidence of radionecrosis after radiosurgery is 5-20%. That radionecrosis after radiosurgery may be confused with a malignant tumor is a known phenomenon and problem.

METHODS:

Three similarly treated patients with cAVM, 1 patient with symptomatic radionecrosis and 2 patients with normal post-radiation MRI changes, were selected and studied in detail with magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and magnetic resonance spectroscopy (MRS). 2 cAVM were located in eloquent locations and were classified as Spetzler-Martin grade (SM) III such that interdisciplinary radiosurgery was recommended; a third patient with a left frontal SM II cAVM refused surgery. 1 patient was male, and 2 were female. The patient's ages ranged from 38 to 62 years (median, 39 years). The nidus volume (= planning target volume = PTV) ranged from 2.75 to 6.89 ccm (median, 6.41 ccm). The single dose was 20 Gy at the isocenter of the PTV encompassing the 80 - 90% isodose. The median follow-up period was 20 months (range, 16 - 84 months). Toxicities were evaluated with the Common Terminology Criteria (CTC) for adverse events version 3.0.

RESULTS:

No patient suffered a bleeding from cAVM during the study period. A complete nidus occlusion was shown in all patients with time-resolved MRA. All patients showed radiogenic MRI changes, 1 patient showed excessive radionecrosis. This patient was oligosymptomatic and under temporary corticoid therapy symptoms resolved completely.Following patterns associated with radionecrosis in the MRS studies were identified in our collective: 2D spectroscopic imaging (2D-SI) revealed much lower concentrations of metabolites in the lesion as compared to contralateral healthy tissue in all patients. Whereas regions with regular post-radiosurgery effects showed almost normal levels of Cho and a Cho/Cr ratio < 2.0, regions with radionecrosis were characterized by increased lipid levels and a Cho/Cr ratio > 2.0 in conjunction with decreased absolute levels of all metabolites, especially of Cr and NAA.

CONCLUSIONS:

MRS is an increasingly valuable tool for the differential diagnosis of radiation reactions. Specific patterns of MRS spectra in radionecrosis were identified; in synopsis with clinical parameters, these changes have to be taken into account to avoid misdiagnosis.

PMID:
23497623
[PubMed - indexed for MEDLINE]
PMCID:
PMC3621843
Free PMC Article

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