Characteristics of 1H-magnetic resonance spectroscopy of the radiation injury of brain

doi:10.3321/j.issn:1673-8225.2004.34.020

Abstract：BACKGROUND: The radiation injury of brain is the severe complication of nasopharyngeal carcinoma(NPC) after radiation therapy. But it is difficulty to diagnose in the early stage. Magnetic resonance spectroscopy(MRS) is sensitive to the cellular metabolism in the tissue of brain, so it is the best method to detect the radiation injury of brain after radiation therapy.OBJECTIVE: To investigate the expression of MRS for the radiation injury of brain.DESIGN: A non-randomized homochronous and controlled trial based on the diagnosis.SETTING: Department of Radiation, the First Affiliated Hospital of Sun Yat-sen University.PARTICIPANTS: As lesion group, 76 patients, who was selected from the Department of Radiation of the First Affiliated Hospital of Sun Yat-sen University, were given follow-up therapy and assayed with MRI and MRS from October 1998 to April 2002. All patients were treated with the radiation therapy of nuchae and nasopharynx after the clinical diagnosis of NPC. As control group, 25 health persons with neither NPC nor the history of radiotherapy were selected and assayed with the same method.INTERVENTIONS: The software of 1.5T MR imaging system and hydrogen(H) spectroscopy were used to assay normal MRI and MRS. The sequences of spectrum were as follows: single volume spectroscopy( SVS ), stimulated-echo acquisition method(STEAM) . And MRI scan parameters consisted of repetition time(TR) =2 000 ms, echo time(TE) = 135 ms, field of view(FOV)= 180 mm × 180 mm, volume of interest(VOI) = 20 mm × 20 mm × 20 mm(8 cm3), and acquisition time = 6.5 minutes. The analysis of MRS peak form: There were 3 types on the basis of different peak values of NAA, Cr and Cho, including type Ⅰ, type Ⅱ and type Ⅲ. The analysis of integral peaks values: Three main integral peak values (NAA, Cr, Cho) were detected and the ratios of NAA/Cr, NAA/(Cr+Cho) and Cho/Cr were calculated by randomization software in central, lateral and normal area of lesion.MAIN OUTCOME MEASURES: ① Forms of different sites in lesion group and control group. ② Peak values and the ratios of different sites in lesion group and control group.RESULTS: Forms of MRS peak was predominantly shown as type Ⅰ pattern(86. 67% ) in healthy control groups. Lesion groups: Type Ⅱ patterns of MRS spectra were mainly found in the centers of focus(68.42% ), and type Ⅰand type Ⅲ were seen in the margins (44. 74% and 39.47% ,respectively ) . Type Ⅰ pattern was mainly found in the normal area(84.21%) . Peak values and ratios of NAA, Cr, Cho, NAA/Cr, NAA/(Ct + Cho) and Cho/C were significant different among different area of the brain ( P ＜ 0. 01 ).CONCLUSION: The patterns of MRS spectra and the changes of integral peak values of metabolism may indicate the degree of the radiation injury of brain. Type Ⅱ spectra demonstrates the existence of the radiation injury of brain. The possibility of radiation injury of brain should be considered if typeⅢ spectra is found and the ratios of NAA/Cr and NAA/(Cr + Cho) are less than one.