RESUMEN
PURPOSE: To segment fiber tracts in the limbic circuit and to assess their sensitivity to radiation therapy (RT). METHODS: Twelve patients with brain metastases who had received fractionated whole brain radiation therapy to 30 Gy or 37.5 Gy were included in the study. Diffusion weighted images were acquired pre-RT, at the end of RT, and 1-month post-RT. The fornix, corpus callosum, and cingulum were extracted from diffusion weighted images by combining fiber tracking and segmentation methods based upon characteristics of the fiber bundles. Cingulum was segmented by a seed-based tractography, fornix by a region of interests (ROI)-based tractography, and corpus callosum by a level-set segmentation algorithm. The radiation-induced longitudinal changes of diffusion indices of the structures were evaluated. RESULTS: Significant decreases were observed in the fractional anisotropy of the posterior part of the cingulum, fornix, and corpus callosum from pre-RT to end of RT by -14.0%, -12.5%, and -5.2%, respectively (p < 0.001), and from pre-RT to 1-month post-RT by -11.9%, -12.8%, and -6.4%, respectively (p < 0.001). Moreover, significant increases were observed in the mean diffusivity of the corpus callosum and the posterior part of the cingulum from pre-RT to end of RT by 6.8% and 6.5%, respectively, and from pre-RT to 1-month post-RT by 8.5% and 6.3%, respectively. The increase in the radial diffusivity primarily contributed to the significant decrease in the fractional anisotropy, indicating that demyelination is the predominant radiation effect on the white matter structures. CONCLUSIONS: Our findings indicate that the fornix and the posterior part of the cingulum are significantly susceptible to radiation damage. We have developed robust computer-aided semiautomatic segmentation and fiber tracking tools to facilitate the ROI delineation of critical structures, which is important for assessment of radiation damage in a longitudinal fashion.
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Axones/efectos de la radiación , Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/secundario , Sistema Límbico/patología , Sistema Límbico/efectos de la radiación , Algoritmos , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/patología , Difusión , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Factores de TiempoRESUMEN
The prefrontal cortex and the hippocampus exhibit converging projections to the nucleus accumbens and have functional reciprocal connections via indirect pathways. As a result, information processing between these structures is likely to be bidirectional. Using evoked potential measures, we examined the interactions of these inputs on synaptic plasticity within the accumbens. Our results show that the direction of information flow between the prefrontal cortex and limbic structures determines the synaptic plasticity that these inputs exhibit within the accumbens. Moreover, this synaptic plasticity at hippocampal and prefrontal inputs selectively involves dopamine D1 and D2 activation or inactivation, respectively. Repeated cocaine administration disrupted this synaptic plasticity at hippocampal and prefrontal cortical inputs and goal-directed behavior in the spatial maze task. Thus, interactions of limbic-prefrontal cortical synaptic plasticity and its dysfunction within the accumbens could underlie complex information processing deficits observed in individuals following psychostimulant administration.
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Cocaína/administración & dosificación , Inhibidores de Captación de Dopamina/administración & dosificación , Dopamina/metabolismo , Sistema Límbico/fisiología , Plasticidad Neuronal/efectos de los fármacos , Núcleo Accumbens/efectos de los fármacos , Corteza Prefrontal/fisiología , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/farmacología , Anfetamina/farmacología , Animales , Conducta Animal/efectos de los fármacos , Agonistas de Dopamina/farmacología , Antagonistas de Dopamina/farmacología , Relación Dosis-Respuesta en la Radiación , Interacciones Farmacológicas , Estimulación Eléctrica/métodos , Potenciales Evocados/efectos de los fármacos , Potenciales Evocados/fisiología , Potenciales Evocados/efectos de la radiación , Sistema Límbico/efectos de los fármacos , Sistema Límbico/efectos de la radiación , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Modelos Biológicos , Núcleo Accumbens/fisiología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/efectos de la radiación , Ratas , Ratas Sprague-Dawley , Factores de TiempoRESUMEN
Responses of single olfactory bulb neurons in rats to x-irradiation of the head were examined during the perfusion through the nasal cavities of gas containing various concentrations of oxygen. Response to x-ray was unchanged with oxygen concentrations of from 100 percent down to about 5 percent. Progressively larger response decrements were observed with oxygen concentrations of 2 percent and less.
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Sistema Límbico/efectos de la radiación , Neuronas/efectos de la radiación , Consumo de Oxígeno , Efectos de la Radiación , Animales , Cabeza/efectos de la radiación , Sistema Límbico/fisiología , Mucosa Nasal/metabolismo , Neuronas/fisiología , RatasRESUMEN
Weak (<1 microT) complex magnetic fields (CMFs) may exert their behavioral influences through the hippocampus by resonating by accident or design with intrinsic electrical patterns. Rats were exposed prenatally to one of four intensities of a CMF (either <5 nanoTesla [nT], 10-50 nT, 50-500 nT, or 500-1000 nT) designed to interact with the process of Long-Term Potentiation (LTP) in the hippocampus. Rats then underwent testing in the forced swim, open field, and fear-conditioning procedures. The cell densities of all amygdaloid nuclei, specific hypothalamic structures, and the major regions of the hippocampus were quantified. Results showed that acquisition of conditioned fear was strongly inhibited in animals exposed to LTP-CMFs. Rats exposed to intensities above 10 nT showed decreased cell density in the CA2 fields of the hippocampus; more neurons were present in the CA1 fields of rats exposed to the 10-50 nT intensities compared to all other groups. A decrease in cell density in the medial preoptic nucleus was linearly dependent on field intensity. In the forced-swim test, swimming was decreased in rats that had been exposed to low (10-50 nT) and medium intensity (50-500 nT) LTP-CMFs in a manner consistent with monoamine modulation. In the open field, exposed rats were indistinguishable from controls. These findings support the hypothesis that continuous exposure during prenatal development to CMFs designed to simulate intrinsic LTP within the hippocampus can affect adult behaviors specific to this structure and produce quantitative alterations in neuronal density.
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Condicionamiento Psicológico/efectos de la radiación , Campos Electromagnéticos/efectos adversos , Sistema Límbico/fisiopatología , Sistema Límbico/efectos de la radiación , Potenciación a Largo Plazo/efectos de la radiación , Efectos Tardíos de la Exposición Prenatal/fisiopatología , Animales , Reacción de Prevención/fisiología , Reacción de Prevención/efectos de la radiación , Recuento de Células , Condicionamiento Psicológico/fisiología , Miedo/fisiología , Miedo/efectos de la radiación , Femenino , Hipocampo/patología , Hipocampo/fisiopatología , Hipocampo/efectos de la radiación , Sistema Límbico/patología , Potenciación a Largo Plazo/fisiología , Masculino , Neurogénesis/fisiología , Neurogénesis/efectos de la radiación , Neuronas/patología , Neuronas/efectos de la radiación , Embarazo , Efectos Tardíos de la Exposición Prenatal/patología , Área Preóptica/patología , Área Preóptica/fisiopatología , Área Preóptica/efectos de la radiación , Ratas , Ratas WistarRESUMEN
Repetitive transcranial magnetic stimulation (rTMS) has been shown to alter cortical excitability depending on the stimulus-frequency used, with high frequency (5 Hz and higher) increasing it but low frequency (usually 1 Hz or lower) reducing it. To determine the efficiency of different rTMS protocols in inducing cortical network activity, we tested the acute effect of one low-frequency rTMS protocol (1 Hz) and two different high-frequency protocols (10 Hz and intermittent theta-burst stimulation, iTBS) on the expression of the two immediate early gene (IEG) proteins c-Fos and zif268 in the rat brain. The cortical expression of both IEGs was specifically changed in an rTMS-dependent manner. One and 10 Hz rTMS enhanced c-Fos protein expression in all cortical areas tested, while iTBS was effective only in limbic cortices. Zif268 expression was increased in almost all cortical areas after iTBS, while 10 Hz rTMS was effective only in the primary motor and sensory cortices. One Hertz rTMS had no effect on cortical zif268 expression. Furthermore, sham-rTMS had no effect on zif268 expression but increased c-Fos in limbic cortices. This is the first study demonstrating that cortical zif268 and c-Fos expression can be specifically modulated by acute rTMS depending on the pattern of stimulation applied.
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Encéfalo/metabolismo , Encéfalo/efectos de la radiación , Proteína 1 de la Respuesta de Crecimiento Precoz/metabolismo , Campos Electromagnéticos , Proteínas Proto-Oncogénicas c-fos/metabolismo , Estimulación Magnética Transcraneal/métodos , Animales , Mapeo Encefálico , Recuento de Células , Corteza Cerebral/metabolismo , Corteza Cerebral/efectos de la radiación , Potenciales Evocados/genética , Potenciales Evocados/efectos de la radiación , Regulación de la Expresión Génica/genética , Regulación de la Expresión Génica/efectos de la radiación , Genes Inmediatos-Precoces/genética , Genes Inmediatos-Precoces/efectos de la radiación , Inmunohistoquímica , Sistema Límbico/metabolismo , Sistema Límbico/efectos de la radiación , Masculino , Red Nerviosa/metabolismo , Red Nerviosa/efectos de la radiación , RatasRESUMEN
The article provides an overview of modern physiological evidence to support the hypothesis on cortico limbic sys tem dysfunction due to the hippocampal neurogenesis impairment as a basis of the brain interhemispheric asym metry and neurocognitive deficit after radiation exposure. The importance of the research of both evoked poten tials and fields as a highly sensitive and informative method is emphasized.Particular attention is paid to cerebral sensor systems dysfunction as a typical effect of ionizing radiation. Changes in functioning of the central parts of sensory analyzers of different modalities as well as the violation of brain integrative information processes under the influence of small doses of ionizing radiation can be critical when determining the radiation risks of space flight. The possible long term prospects for manned flights into space, including to Mars, given the effects identified are discussed. Potential risks to the central nervous system during space travel comprise cognitive functions impairment, including the volume of short term memory short ening, impaired motor functions, behavioral changes that could affect human performance and health. The remote risks for CNS are considered to be the following possible neuropsychiatric disorders: accelerated brain aging, Alzheimer's disease and other types of dementia. The new radiocerebral dose dependent effect, when applied cog nitive auditory evoked potentials P300 technique with a possible threshold dose of 0.05 Gy, manifesting in a form of disruption of information processing in the Wernicke's area is under discussion. In order to identify neurophys iological biological markers of ionizing radiation further international researches with adequate dosimetry support are necessary.
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Envejecimiento Prematuro/etiología , Corteza Cerebral/efectos de la radiación , Sistema Límbico/efectos de la radiación , Trastornos Neurocognitivos/etiología , Trastornos Psicomotores/etiología , Exposición a la Radiación/efectos adversos , Envejecimiento Prematuro/diagnóstico , Envejecimiento Prematuro/fisiopatología , Corteza Cerebral/fisiopatología , Cognición/fisiología , Cognición/efectos de la radiación , Radiación Cósmica/efectos adversos , Potenciales Evocados/fisiología , Potenciales Evocados/efectos de la radiación , Humanos , Sistema Límbico/fisiopatología , Memoria a Corto Plazo/fisiología , Memoria a Corto Plazo/efectos de la radiación , Trastornos Neurocognitivos/diagnóstico , Trastornos Neurocognitivos/fisiopatología , Trastornos Psicomotores/diagnóstico , Trastornos Psicomotores/fisiopatología , Radiación Ionizante , Vuelo EspacialRESUMEN
Human brain in prenatal period is a most vulnerable to ionizing radiation body structure. Unlike atomic bombings or radiological interventions in healthcare leading at most to external irradiation the intensive internal exposure may occur upon nuclear reactor accidents followed by substantial release and fallout of radioactive 131I. The latter can lead to specific neuroradioembryological effects. OBJECTIVE: To create an experimental model of prenatal cerebral radiation effects of 131I in human and to determine the experimental and clinical neuroradioembryological effects.Study object. The neuroradioembryological effects in Vistar rats exposed to 131I in prenatal period. Nervous system status and mental status in 104 persons exposed to ionizing radiation in utero due to the ChNPP accident and the same in 78 not exposed subjects. METHODS: Experimental i.e. behavioral techniques, including the spontaneous locomotive, exploratory activity and learning ability assessment, clinical i.e. neuropsychiatric, neuro and psychometric, neuropsychological, neurophys iological methods, both with dosimetric and statistical methods were applied. RESULTS: Intrauterine irradiation of Wistar rats by 131I was simulated on a model of one time oral 27.5 kBq radionu clide administration in the mid gestation period (0.72±0.14 Gy fetal thyroid dose), which provides extrapolation of neuroradioembryological effects in rats to that in humans exposed to intrauterine radiation as a result of the Chornobyl catastrophe. Abnormalities in behavioral reactions and decreased output of conditioned reflex reactions identified in the 10 month old rats suggest a deterioration of cerebral cognition in exposed animals. Specific cog nitive deficit featuring a disharmonic intellectual development through the relatively decreased verbal intelligence versus relative increase of nonverbal one is remained in prenatally exposed persons. This can indicate to dysfunc tion of cortical limbic system with especial involvement of a dominant hemisphere hippocampus. Decreased theta band spectral power (4-7 Hz range) of cerebral bioelectrical activity in the left frontotemporal area is suggestive of hippocampal dysfunction mainly in dominant hemisphere of prenatally irradiated persons. Disorders of hippocam pal neurogenesis due to prenatal exposure by radioactive iodine can be a biologic basis here. Innovative approach es in social adaptation, psychoprophylaxis and psychorehabilitation involve the maximum effective application and development of just the most developed psychological and cognitive abilities in survivors.
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Accidente Nuclear de Chernóbil , Disfunción Cognitiva/fisiopatología , Radioisótopos de Yodo/administración & dosificación , Exposición Materna/efectos adversos , Efectos Tardíos de la Exposición Prenatal/fisiopatología , Exposición a la Radiación/efectos adversos , Traumatismos Experimentales por Radiación/fisiopatología , Adulto , Animales , Estudios de Casos y Controles , Corteza Cerebral/fisiopatología , Corteza Cerebral/efectos de la radiación , Disfunción Cognitiva/etiología , Disfunción Cognitiva/psicología , Condicionamiento Clásico/efectos de la radiación , Embrión de Mamíferos/efectos de la radiación , Conducta Exploratoria/efectos de la radiación , Femenino , Humanos , Sistema Límbico/fisiopatología , Sistema Límbico/efectos de la radiación , Locomoción/efectos de la radiación , Masculino , Pruebas de Estado Mental y Demencia , Embarazo , Efectos Tardíos de la Exposición Prenatal/psicología , Desempeño Psicomotor/efectos de la radiación , Traumatismos Experimentales por Radiación/psicología , Ratas , Ratas WistarRESUMEN
In the present study, adult Long-Evans rats were exposed either to natural conspecific aversive 22-kHz vocalizations or to artificial call-like stimuli with comparable frequency-temporal features, followed by c-Fos immunohistochemistry. The natural 22-kHz vocalizations was either played from a recording or produced by a foot-shocked animal located nearby (live vocalizations). In comparison with controls (non-exposed animals), c-Fos immunoreactivity was significantly increased in the inferior colliculus (IC), auditory cortex (AC), periaqueductal grey (PAG), basolateral amygdala (BA), and hippocampus (Hip) of rats exposed to either live or recorded 22-kHz natural vocalizations. Exposure to live natural vocalizations of the foot-shocked animal resulted in a similar pattern of c-Fos activity, as did exposure to the playback of the natural vocalizations. In contrast to this, foot-shocked rats (emitting the 22-kHz vocalizations) had the c-Fos positivity increased markedly in the PAG and only slightly in the AC. The expression of c-Fos also increased in the IC, AC, and in the PAG in animals exposed to the artificial call-like stimuli, when compared to controls; however, the increase was much less pronounced. In this case, c-Fos expression was not increased in the hippocampus or basolateral amygdala. Interestingly, almost no c-Fos expression was found in the medial nucleus of the geniculate body in any of the experimental groups. These findings suggest that differences exist between the processing of important natural conspecific vocalizations and artificial call-like stimuli with similar frequency-temporal features, and moreover they suggest the specific role of individual brain structures in the processing of such calls.
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Corteza Auditiva/metabolismo , Corteza Auditiva/efectos de la radiación , Sistema Límbico/metabolismo , Sistema Límbico/efectos de la radiación , Proteínas Proto-Oncogénicas c-fos/metabolismo , Vocalización Animal , Estimulación Acústica , Animales , Mapeo Encefálico , Femenino , Ratas , Ratas Long-Evans , Vocalización Animal/fisiologíaRESUMEN
Spontaneous locomotor activity and the locomotor response to amphetamine and apomorphine were studied in rats subjected to either radiofrequency (RF), 6-hydroxydopamine (6-OHDA) or both RF and 6-OHDA lesions of the mesolimbic dopamine (DA) system. Large 6-OHDA lesions of the ventral tegmental area (VTA) or of the nucleus accumbens (N.Acc.) produced hypo-activity in the open field, a complete blockade of the locomotor stimulating effects of D-amphetamine and a profound supersensitive response to apomorphine as measured by a significant increase in locomotor activity as compared to sham-operated animals. In contrast, smaller 6-OHDA lesions of the VTA produced significant increases in spontaneous daytime and nocturnal activity with the biggest effect occurring at the lowest dose. RF lesions to the VTA produced even greater hyperactivity which was blocked by the addition of a 6-OHDA lesion to the N.Acc. The rats with RF lesions to VTA alone that were spontaneously hyperactive remained hyperactive after injection of amphetamine, whereas apomorphine produced a significant decrease in this hyperactivity. In contrast, the rats with the combined RF lesion and N.Acc. 6-OHDA lesion showed a blockade of the locomotor stimulating effects of D-amphetamine and a potentiated response to apomorphine identical to that observed with a N.Acc. lesion alone. All lesion groups revealed massive depletion of DA in the N.Acc. and anterior striatum with significantly greater depletions in those groups showing hypoactivity and hypo-responsiveness to amphetamine. All groups except the N.Acc. 6-OHDA alone group showed significant depletions of DA in the posterior striatum. Thus, limited destruction of the mesolimbic DA system can produce hyperactivity, but more extensive destruction of this system in the region of the N.Acc. and anterior striatum can reverse this hyperactivity and produce a hypo-responsiveness to the locomotor stimulating effects of amphetamine. These results suggest an essential role for dopamine in the expression of spontaneous and stimulant-induced activity. Furthermore, the much larger increase in spontaneous activity in the RF-VTA lesion group as compared to the VTA-6-OHDA groups suggests the presence of an, as yet unidentified, powerful inhibitory influence to the mesolimbic DA system within the midbrain tegmentum.
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Dopamina/fisiología , Sistema Límbico/fisiología , Actividad Motora/fisiología , Animales , Apomorfina/farmacología , Mapeo Encefálico , Dihidroxifenilalanina/análogos & derivados , Dihidroxifenilalanina/farmacología , Sistema Límbico/efectos de la radiación , Masculino , Núcleo Accumbens/fisiología , Ondas de Radio , Ratas , Tegmento Mesencefálico/fisiologíaRESUMEN
Previous work from our laboratory has shown that naïve Wistar Audiogenic Rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), are seizure-prone to a variety of pro-convulsive stimuli (e.g., transauricular electroshock, pentylenetetrazole and pilocarpine). On the other hand, repetitive acoustic stimulation of WARs causes a slow recruitment of limbic structures, known as audiogenic kindling, changing seizure expression to include behavior characteristic of temporal-lobe epilepsy. Thus, our hypothesis is that WARs have facilitated acoustic-limbic projections when compared to Wistar controls. Wistar controls (n = 9) and WARs (n = 9) underwent EEG electrode implants in the cortex-Cx, amygdaloid complex-AMY and inferior colliculus-IC and received one low current transauricular electrical stimulus (ES) daily, for three consecutive days, with intensities of 10, 20 and 30 mA, respectively. The video-electroencephalographic activity was recorded 1 min before and 4 min after ES. Our results confirm previously described data indicating a greater susceptibility of WARs to seizure. However, low current ES (e.g., 20 mA) triggered epileptiform activity in the AMY only after epileptiform EEG was visible in the Cx and IC electrode leads. The AMY after-discharge continued even though no evident epileptiform activity was present in the Cx. In conclusion, our results add electrophysiological data to previously published behavioral evidence of WAR enhanced susceptibility to ES seizures and, also, support the hypothesis that the acoustic-limbic circuitry is facilitated even in unkindled WARs.
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Estimulación Acústica/efectos adversos , Electrochoque , Epilepsia Refleja/fisiopatología , Epilepsia del Lóbulo Temporal/etiología , Animales , Conducta Animal , Modelos Animales de Enfermedad , Relación Dosis-Respuesta en la Radiación , Electroencefalografía/métodos , Electroencefalografía/efectos de la radiación , Epilepsia del Lóbulo Temporal/fisiopatología , Sistema Límbico/anatomía & histología , Sistema Límbico/fisiopatología , Sistema Límbico/efectos de la radiación , Masculino , Ratas , Ratas Wistar , Reclutamiento Neurofisiológico , Estadísticas no ParamétricasRESUMEN
The classical cortico-reticular theory on absence epilepsy suggests that a hyperexcitable cortex is a precondition for the occurrence of absence seizures. In the present experiment seizure thresholds and characteristics of cortical and limbic epileptic afterdischarges (AD) were determined in a comparative cortical stimulation study in young and old adult genetically epileptic WAG/Rij, congenic ACI and Wistar rats. Fifteen-second series of 8Hz stimulation of the sensory-motor cortex were applied in 80- and 180-day-old rats with implanted electrodes. Strain differences were found for the threshold for movements directly induced by stimulation, low frequency spike-and-wave AD, maximal clonic intensity of seizures accompanying direct stimulation, and frequency characteristics of low frequency AD. None of these results agreed with a higher cortical excitability exclusively in WAG/Rij rats. However, WAG/Rij rats had the longest duration of the low frequency AD, and the lowest threshold for the transition to the limbic type of AD. The decrease of this threshold correlated with the increase of the incidence and total duration of spontaneous SWDs in WAG/Rij rats. It is concluded that the elevated excitability of the limbic system or pathways mediating the spread of the epileptic activity into this system can be attributed to the development of genetic epileptic phenotype in WAG/Rij rats.
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Corteza Cerebral/efectos de la radiación , Epilepsia Tipo Ausencia/fisiopatología , Sistema Límbico/efectos de la radiación , Factores de Edad , Análisis de Varianza , Animales , Corteza Cerebral/fisiología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta en la Radiación , Estimulación Eléctrica/métodos , Electrodos Implantados , Electroencefalografía/métodos , Electroencefalografía/efectos de la radiación , Epilepsia Tipo Ausencia/genética , Sistema Límbico/fisiología , Masculino , Movimiento/efectos de la radiación , Ratas , Ratas Endogámicas , Ratas Wistar , Umbral Sensorial/efectos de la radiación , Especificidad de la Especie , Factores de TiempoRESUMEN
INTRODUCTION: The aim of this study was to assess the feasibility of sparing contralateral or bilateral neural stem cell (NSC) compartment, hippocampus and limbic circuit during partial brain radiotherapy (PBRT). METHODS AND MATERIALS: Treatment plans were generated for five hemispheric high-grade gliomas, five hemispheric low-grade gliomas and two brainstem gliomas (12 patients). For each, standard intensity-modulated radiotherapy (IMRT) plans were generated, as well as IMRT plans which spared contralateral (hemispheric cases) or bilateral (brainstem cases) limbic circuit, hippocampus, and NSC. Biologically equivalent dose for late effects (BED(late effects)) was generated for limbic circuit, hippocampus and NSC. Per cent relative reduction in mean physical dose and BED was calculated for each plan (standard vs. sparing). RESULTS: We were able to reduce physical dose and BED(late effects) to these critical structures by 23.5-56.8% and 23.6-66%, respectively. CONCLUSION: It is possible to spare contralateral limbic circuit, NSC and hippocampus during PBRT for both high- and low-grade gliomas using IMRT, and to spare the hippocampus bilaterally during PBRT for brainstem low-grade gliomas. This approach may reduce late cognitive sequelae of cranial radiotherapy.
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Neoplasias Encefálicas/radioterapia , Irradiación Craneana/métodos , Glioma/radioterapia , Hipocampo/efectos de la radiación , Sistema Límbico/efectos de la radiación , Células Madre Pluripotentes/efectos de la radiación , Traumatismos por Radiación/prevención & control , Estudios de Factibilidad , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Dosificación Radioterapéutica , Radioterapia de Intensidad ModuladaRESUMEN
INTRODUCTION: The study aims to assess the feasibility of dosimetrically sparing the limbic circuit during whole brain radiation therapy (WBRT) and prophylactic cranial irradiation (PCI). METHODS AND MATERIALS: We contoured the brain/brainstem on fused MRI and CT as the target volume (PTV) in 11 patients, excluding the hippocampus and the rest of the limbic circuit, which were considered organs at risk (OARs). PCI and WBRT helical tomotherapy plans were prepared for each patient with a 1.0-cm field width, pitch = 0.285, initial modulation factor = 2.5. We attempted to spare the hippocampus and the rest of the limbic circuit while treating the rest of the brain to 30 Gy in 15 fractions (PCI) or 35 Gy in 14 fractions (WBRT) with V(100) >or= 95%. The quality of the plans was assessed by calculating mean dose and equivalent uniform dose (EUD) for OARs and the % volume of the PTV receiving the prescribed dose, V(100). RESULTS: In the PCI plans, mean doses/EUD were: hippocampus 12.5 Gy/14.23 Gy, rest of limbic circuit 17.0 Gy/19.02 Gy. In the WBRT plans, mean doses/EUD were: hippocampus 14.3 Gy/16.07 Gy, rest of limbic circuit 17.9 Gy/20.74 Gy. The mean V(100) for the rest of the brain (PTV) were 94.7% (PCI) and 95.1% (WBRT). Mean PCI and WBRT treatment times were essentially identical (mean 15.23 min, range 14.27-17.5). CONCLUSIONS: It is dosimetrically feasible to spare the hippocampus and the rest of the limbic circuit using helical tomotherapy while treating the rest of the brain to full dose.