RESUMO
To discern if specific structures of the rat brain contained more foci of lymphocytes following induction of experimental allergic encephalomyelitis and exposures to weak, amplitude-modulated magnetic fields for 6 min once per hour during the scotophase, the residuals between the observed and predicted values for the numbers of foci for 320 structures were obtained. Compared to the brains of sham-field exposed rats, the brains of rats exposed to 7-Hz 50 nT (0.5 mG) amplitude-modulated fields showed more foci within hippocampal structures and the dorsal central grey of the midbrain while those exposed to 7-Hz 500 nT (5 mG) fields showed greater densities within the hypothalamus and optic chiasm. The brains of rats exposed to either the 50 nT or 500 nT amplitude-modulated 40-Hz fields displayed greater densities of foci within the midbrain structures related to rapid eye movement. Most of the enhancements of infiltrations within the magnetic field-exposed rats occurred in structures within periventricular or periaqueductal regions and were both frequency- and intensity-dependent. The specificity and complexity of the configurations of the residuals of the numbers of infiltrated foci following exposures to the different fields suggest that the brain itself may be a "sensory organ" for the detection of these stimuli.
Assuntos
Encéfalo/efeitos da radiação , Ritmo Circadiano/efeitos da radiação , Campos Eletromagnéticos , Encefalomielite Autoimune Experimental/fisiopatologia , Ativação Linfocitária/efeitos da radiação , Linfócitos/efeitos da radiação , Animais , Encéfalo/anatomia & histologia , Encéfalo/imunologia , Ventrículos Cerebrais/fisiologia , Quimiotaxia de Leucócito/imunologia , Quimiotaxia de Leucócito/efeitos da radiação , Ritmo Circadiano/imunologia , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/imunologia , Feminino , Hipocampo/imunologia , Hipocampo/efeitos da radiação , Hipotálamo/imunologia , Hipotálamo/efeitos da radiação , Mesencéfalo/imunologia , Mesencéfalo/efeitos da radiação , Quiasma Óptico/imunologia , Quiasma Óptico/efeitos da radiação , Ratos , Ratos Endogâmicos Lew , Sono REM/imunologia , Sono REM/efeitos da radiaçãoRESUMO
OBJECTIVES: The present study characterized glial cell injury provoked in adult rat chiasm within 24 hours after a single, high-dose irradiation of 20 Gy. METHODS: All chiasmal glial cells in a section were counted, and the percentage of TUNEL-positive glial cells exhibiting apoptotic morphology was defined as the apoptotic rate. RESULTS: Numbers of apoptotic cells increased significantly (p<0.0001) from 3 to 8 hours after exposure, but returned to baseline levels by 24 hours. Little evidence of apoptosis was observed in non-irradiated chiasms. Similar patterns of increase in apoptotic rate were observed in the genu of the corpus callosum, but the extent was significantly lower (p=0.047) in the optic chiasm, with a maximal rate of 1.9%. Immunohistochemically, apoptotic cells were positive for CNP, a marker for oligodendrocytes. DISCUSSION: These data indicate that chiasmal irradiation induces limited, but significant apoptotic depletion of the oligodendroglial population, and may participate in the development of radiation-induced optic neuropathy.
Assuntos
Apoptose/efeitos da radiação , Oligodendroglia/efeitos da radiação , Quiasma Óptico/citologia , Lesões Experimentais por Radiação/patologia , Radiação , Análise de Variância , Animais , Contagem de Células , Corpo Caloso/efeitos da radiação , Relação Dose-Resposta à Radiação , Imuno-Histoquímica/métodos , Marcação In Situ das Extremidades Cortadas , Masculino , Nucleosídeo-Trifosfatase/metabolismo , Oligodendroglia/citologia , Quiasma Óptico/efeitos da radiação , Lesões Experimentais por Radiação/metabolismo , Ratos , Ratos Wistar , Fatores de TempoRESUMO
BACKGROUND AND PURPOSE: The aim of this study is to evaluate and delineate the deficiencies in conventional two-dimensional (2-D) radiotherapy planning of nasopharyngeal carcinoma (NPC) treatment and to explore the means for improvement of the existing treatment technique aiming at enhancing local tumor control and reducing treatment complications. METHODS AND MATERIALS: Ten patients with NPC sparing the skull base and without intracranial extension or cranial nerve(s) palsy were chosen in the present study. Two sets of CT images for Phases I and II of the radiotherapy treatment were taken with patient immobilized in the flexed-head and the extended-head positions, respectively. Based on the CT images and endoscopic findings, the gross tumor volume (GTV) was defined. The clinical target volume (CTV) circumscribing the GTV was defined according to Ho's (Halnan, K.E. (ed.) Treatment of Cancer. London: Chapman and Hall, 1982. pp. 249-268) description of the organs at risk of tumor infiltration. The planning target volume (PTV) was defined by adding a margin to the CTV which catered for geometrical inaccuracies. The field borders and shields were set at standard distances from certain bony landmarks and were drawn on the simulator radiograph. Data on the beams and shield arrangements were then transferred to the planning computer via a digitizer. By applying 3-D volumetric dose calculation using a commercial three-dimensional (3D) treatment planning computer, the dose-volume-histograms (DVHs) of GTV, CTV, PTV and critical normal organs were generated for both phases of Ho's treatment technique. The same patients were re-planned using a modified Ho's technique which used 3-D beams-eye-view (BEV) in placing the shielding blocks and the same set of DVHs were generated and compared with those obtained from Ho's technique. RESULTS: The median volumes of GTV, CTV and PTV covered by the 95% isodose in Ho's phase I treatment were around 60%. The dose coverage was unsatisfactory in the superior and inferior and the posterolateral regions. In phase II treatment, the median volume of GTV, CTV and PTV covered by the 95% isodose were 99, 96 and 72%, respectively. Even though the dose coverage of the PTV in both phases of treatment were unsatisfactory, radiotherapy with the original Ho's technique had consistently produced good local control for NPC. However, there is potential room for enhancing the local control further because after modifying Ho's technique by using 3-D BEV customization of the treatment portals, the median volume of the target covered by the 95% isodose was defined as V(95). The V(95) of the PTV during the Phase II treatment was improved by 13%. The 90% of the volume of temporo-mandibular joints and parotid glands were both irradiated to 53 Gy and 43.6 Gy of the total prescribed dose of 66 Gy, respectively, in phase I and II treatments. With the addition of a hypothalamus-pituitary shield to Ho's technique, 50% of the volume of optic chiasma and temporal lobes received, respectively, 19.3 Gy and 4.5 Gy. However, small volume of the temporal lobes received a maximum dose (D(max)) of 62.8 Gy (95.2% of 66Gy). Most of the brainstem was shielded from the lateral portals but 5% of its volume received a dose ranging from 25.4 to 50.4Gy. The spinal cord (at C1/C2 level) received a D(max) of 40.8 Gy in phase I and of 4.8 Gy in phase II. After modifying Ho's technique by 3-D BEV customization of the treatment portals, the D(max) to the brainstem, the optic chiasma and the temporal lobes could be reduced by 8, 12 and 5%, respectively. CONCLUSIONS: Our study indicated that the dose-coverage of the PTV in Ho's radiotherapy technique for the early T-stage NPC was less than satisfactory in the superior and inferior and the posterolateral regions. However, in view of the excellent historical local tumor control with Ho's technique, we have to postulate that the present definition of CTV (and hence the PTV after adding margins to the CTV) lacks clinical significance and can be improved. It appears that the inclusion of the entire sphenoid sinus floor and both medial and lateral pterygoid muscles in the CTV is not necessary for maximal tumor control in the absence of clinical/radiological evidence of tumor infiltration of these organs. Ho's technique can be improved by using 3-D BEV to customize the treatment portals with multileaf collimators or blocks.
Assuntos
Carcinoma/radioterapia , Neoplasias Nasofaríngeas/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Conformacional/métodos , Tronco Encefálico/efeitos da radiação , Endoscopia , Humanos , Hipotálamo/efeitos da radiação , Imobilização , Recidiva Local de Neoplasia/prevenção & controle , Quiasma Óptico/efeitos da radiação , Glândula Parótida/efeitos da radiação , Hipófise/efeitos da radiação , Postura , Estudos Prospectivos , Músculos Pterigoides/efeitos da radiação , Proteção Radiológica , Dosagem Radioterapêutica , Medula Espinal/efeitos da radiação , Lobo Temporal/efeitos da radiação , Articulação Temporomandibular/efeitos da radiação , Tomografia Computadorizada por Raios XRESUMO
A 71-year-old woman developed complete third nerve palsy and total blindness of the right eye one month after completing a course of radiotherapy for sphenoid sinus carcinoma over a 13-month period. Differential diagnosis included recurrence of the tumor, radiation-induced second neoplasm, empty sella with chiasmal prolapse and secondary chiasmal arachnoid adhesions, and radionecrosis. Magnetic resonance imaging demonstrated gadolinium contrast enhancement of the right intracranial optic nerve and chiasm, suggesting a radionecrosis process.
Assuntos
Cegueira/etiologia , Carcinoma/radioterapia , Quiasma Óptico/efeitos da radiação , Nervo Óptico/efeitos da radiação , Neoplasias dos Seios Paranasais/radioterapia , Lesões por Radiação/etiologia , Seio Esfenoidal/efeitos da radiação , Idoso , Carcinoma/etiologia , Quimioterapia Adjuvante , Cisplatino/uso terapêutico , Diagnóstico Diferencial , Feminino , Fluoruracila/uso terapêutico , Humanos , Imageamento por Ressonância Magnética , Neoplasias Induzidas por Radiação/etiologia , Segunda Neoplasia Primária/etiologia , Doenças do Nervo Oculomotor/diagnóstico , Doenças do Nervo Oculomotor/etiologia , Atrofia Óptica/etiologia , Quiasma Óptico/patologia , Nervo Óptico/patologia , Neoplasias dos Seios Paranasais/etiologia , Campos VisuaisRESUMO
Thirteen patients with delayed radiation injury to the optic nerves and chiasm were treated with hyperbaric oxygen (HBO) and corticosteroids. These patients experienced painless, abrupt loss of vision in one (6 patients) or both (7 patients) eyes between 4 and 35 months after receiving radiation doses of at least 4500 cGy to the region of the chiasm. Diagnostic evaluation including neuro-imaging and lumbar puncture showed no recurrent tumor and no other cause for visual loss. No patient's vision improved during treatment or follow-up lasting between 1 and 4 years. There were no serious complications of treatment.