RESUMEN
Proton MR spectroscopy was used to observe long-term post-irradiation metabolic changes in epileptogenic tissue and in the contralateral parts of the brain which are not available with conventional imaging methods. We studied these changes in the temporal lobe in six patients, following radiosurgery on the amygdala and hippocampus. (1)H MR spectroscopy at 1.5 T with short and long echo times (TE=10 and 135 ms) were used together with standard MR imaging sequences (T1-, T2-weighted). The treatment was performed by Leksell Gamma Knife with a dose of 50 Gy to the center and a 50% isodose to the margin of the target, represented by the mean volume of approximately 7.5 ml. Magnetic resonance imaging and MR spectroscopy examinations were performed at least once per year for 3 years. The most significant changes in spectra were observed approximately 1 year after the irradiation when edema in irradiated area was observed and strong signal of lipids was identified. Later, edema and lipid signals disappeared and follow-up was characterized by a decrease of NAA, Cr, and Cho concentrations in the ipsilateral region of the brain to the irradiation (LCModel calculation from voxel of interest 3.8-4.5 ml positioned into the centrum of target volume). The concentration of NAA, Cr, and Cho after radiosurgery was significantly different from control values ( p<0.05) and also from concentrations in the contralateral part of the brain ( p<0.05). In the contralateral part, the concentration of NAA was significantly increased ( p<0.05) (NAA: before treatment 8.81, after treatment 11.33 mM). No radiotoxic changes were observed in the contralateral part of the brain or behind the area of target volume. The MR spectroscopy findings precluded MRI observation and MRS results completed data about the development of radiotoxic changes in the target volume.
Asunto(s)
Ácido Aspártico/análogos & derivados , Epilepsia del Lóbulo Temporal/diagnóstico , Epilepsia del Lóbulo Temporal/cirugía , Radiocirugia , Adulto , Ácido Aspártico/metabolismo , Ácido Aspártico/efectos de la radiación , Encéfalo/metabolismo , Encéfalo/efectos de la radiación , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/cirugía , Colina/metabolismo , Colina/efectos de la radiación , Creatina/metabolismo , Creatina/efectos de la radiación , Epilepsia del Lóbulo Temporal/metabolismo , Femenino , Estudios de Seguimiento , Ácido Glutámico/metabolismo , Ácido Glutámico/efectos de la radiación , Glutamina/metabolismo , Glutamina/efectos de la radiación , Humanos , Metabolismo de los Lípidos , Lípidos/efectos de la radiación , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Masculino , Complicaciones Posoperatorias/diagnóstico , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/metabolismo , Traumatismos por Radiación/diagnóstico , Traumatismos por Radiación/etiología , Traumatismos por Radiación/metabolismo , Tolerancia a Radiación/fisiología , Radiocirugia/efectos adversos , Convulsiones/diagnóstico , Convulsiones/etiología , Convulsiones/metabolismo , Factores de Tiempo , Insuficiencia del TratamientoRESUMEN
To investigate a method to reduce the amount of mutagenic/carcinogenic heterocyclic aromatic amines formed during frying of ground beef, the mutagenic activity in Salmonella strain TA98 was assessed and the amount of known heterocyclic amines was determined by solid-phase extraction and HPLC. The beef patties received microwave treatment for various times before frying. Microwave pretreatment for 0, 1, 1.5, 2 or 3 min before frying at either 200 degrees C or 250 degrees C for 6 min per side reduced heterocyclic aromatic amine precursors (creatine, creatinine, amino acids, glucose), water, and fat up to 30%, in the patties and resulted in a decrease in mutagenic activity up to 95%. The sum of the four heterocyclic aromatic amines shown to be present--2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4,8-trimethylimidazo-[4,5-f]quinoxaline (DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)--decreased three- to nine-fold compared with control, non-microwaved beef patties fried under identical conditions.