RESUMEN
In vivo cell electropermeabilization can be used alone or in combination with a hydrophilic, nonpermeant cytotoxic drug such as bleomycin (electrochemotherapy) to efficiently treat tumors. We used magnetic resonance imaging to detect rapid structural modifications in tumors treated by electroporation-based methods. Water diffusion coefficient (ADC), transverse relaxation time (T(2)) and tumor volume of fibrosarcomas xenografted on syngenic mice were measured upon 3 groups of 6 treated mice within the 48 hrs following ECT done with a normal (BE) or a high dose of bleomycin (HBE), and after irreversible electroporation (IRE), and in three control groups. As expected, the tumor volume increased in the control groups at 48 hrs (p < 0.05) and the values of ADC and T2 did not varied significantly in the control groups except for ADC decrease and T2 increase observed between 3 hrs and 24 hrs (p < 0.03) in the group that received bleomycin only. Tumor volumes decreased significantly at 24 hrs in the IRE and HBE groups. The mean tumor ADC increased significantly at 24 hrs (117.6%, p < 0.03) in the BE group, probably reflecting apoptosis, while in the HBE group the mean tumor ADC increased earlier, at 10 hrs (119%, p < 0.03) because of the speed of the pseudoapopototic process. In the IRE group, the mean tumor ADC decreased significantly at 1 hrs (p < 0.05) and 3 hrs (p < 0.03), and T(2) decreased (p < 0.03), both probably reflecting cell swelling induced by the vascular lock. Thus ADC and T(2) changes in the treated tumors correlated with previous histological observations on the same tumor models. Noteworthy, ADC allowed the visualization of early and rapid changes in the treated tumors, when tumor volume monitoring was not yet able to detect any effect of the treatments.
Asunto(s)
Imagen por Resonancia Magnética , Neoplasias Experimentales/diagnóstico , Animales , Línea Celular Tumoral , Electroquimioterapia , Electroporación , Ratones , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Resultado del Tratamiento , Carga TumoralRESUMEN
To evaluate the ability of MR T2 mapping (8.5 T) to characterize ex vivo longitudinally, morphologically and quantitatively, alginate-based tissue engineering in a rat model of patellar cartilage chondral focal defect. Calibrated rat patellar cartilage defects (1.3 mm) were created at day 0 (D0) and alginate sponge with (Sp/C+) or without (Sp/C-) autologous chondrocytes were implanted. Animals were sacrificed sequentially at D20, D40 and D60 after surgery and dissected patellae underwent MRI exploration (8.5 T). T2 values were calculated from eight SE images by using nonlinear least-squares curve fitting on a pixel-by-pixel basis (constant repetition time of 1.5 s, eight different echo times: 5.5, 7.5, 10.5, 12.5, 15.0, 20.0, 25.0 and 30.0 ms). On the T2 map, acquired in a transversal plane through the repair zone, global T2 values and zonal variation of T2 values of repair tissue were evaluated versus control group and compared with macroscopic score and histological studies (toluidine blue, sirius red and hematoxylin-eosin). "Partial", "total" and "hypertrophic" repair patterns were identified. At D40 and D60, Sp/C+ group was characterized by a higher proportion of "total" repair in comparison to Sp/C- group. At D60, the proportion of "hypertrophic" repair was two fold in Sp/C- group versus Sp/C+ group. As confirmed morphologically and histologically, the T2 map also permitted the distinction of three types of repair tissue: "total", "partial" and "hypertrophic". "Total" repair tissue was characterized by high T2 values versus normal cartilage (p<0.05). Zonal variation, reflecting the collagen network organization, appeared only at D60 for Sp/C+ group (p<0.05). "Hypertrophic" tissue, mainly observed at D60, presented high T2 global values without zonal variation with cartilage depth. These results confirm the potency of the MR T2 map (8.5 T) to characterize macroscopically and microscopically the patterns of the scaffold guided-tissue repair of a focal chondral lesion in the rat patella ("total", "partial" and "hypertrophic"). On T2 map, three parameters (i.e. MRI macroscopic pattern, T2 global values and zonal variation of T2 values) permit to characterize chondral repair tissue, as a virtual biopsy.
Asunto(s)
Cartílago Articular/patología , Cartílago Articular/cirugía , Condrocitos/patología , Condrocitos/trasplante , Regeneración Tisular Dirigida/métodos , Imagen por Resonancia Magnética/métodos , Cicatrización de Heridas/fisiología , Animales , Cartílago Articular/crecimiento & desarrollo , Cartílago Articular/lesiones , Aumento de la Imagen/métodos , Masculino , Ligamento Rotuliano/lesiones , Ligamento Rotuliano/patología , Ligamento Rotuliano/cirugía , Pronóstico , Ratas , Ratas Wistar , Regeneración , Índice de Severidad de la Enfermedad , Ingeniería de Tejidos/métodos , Resultado del TratamientoRESUMEN
OBJECTIVE: To evaluate the ability of T2 mapping on an 8.5 T imager to characterize morphologically and quantitatively spontaneous repair of rat patellar cartilage following full thickness defect. METHODS: Patellar cartilage defects were created in 24 rats knees on D0. Eight rats per time-point were killed on D20, D40 and D60 after surgery. T2 maps of repair tissue in patellar defects were obtained from eight different axial spin echo images on an 8.5 T imager. Global, superficial and deep T2 values were evaluated in spontaneous repair tissues (3x8 right patellae) vs the opposite patellae (3x8 left patellae) of the same animals. MR data were compared with macroscopic and histological studies. RESULTS: T2 map was able to identify morphologically three types of repair tissue observed macroscopically and histologically: 'total', 'partial' and 'hypertrophic' repair tissue. 'Total' and 'partial' repair tissues were characterized by global T2 values almost similar to controls, whereas 'hypertrophic' repair tissues were characterized by T2 global values higher than controls. Zonal variation between superficial and deep T2 values observed in controls was not depicted in repair tissue before D60. CONCLUSION: T2 map is able to characterize quantitatively and qualitatively rat patellar cartilage repair, and thus can be promoted, as a non invasive technique, in clinical longitudinal studies of articular cartilage repair.
Asunto(s)
Cartílago Articular/patología , Traumatismos de la Rodilla/patología , Imagen por Resonancia Magnética/métodos , Rótula/patología , Animales , Condrocitos/patología , Modelos Animales de Enfermedad , Fibroblastos/patología , Masculino , Ratas , Ratas Wistar , Cicatrización de HeridasRESUMEN
PURPOSE: To investigate the usefulness of magnetic resonance (MR) T2 mapping in characterizing the evolution of cartilage matrix content and thickness during the maturation and aging process. MATERIALS AND METHODS: Patellae from four groups of rats aged 4 weeks, 8 weeks, 4 months, and more than 6 months ("old rats") were studied ex vivo with an 8.5-T microimager. T2 values were calculated on transverse rat patellar sections and displayed with a color scale (the T2 map) on a pixel-by-pixel basis. Biochemical and histologic studies were performed to evaluate the influence of proteoglycans and collagen contents on T2 values of the patellar cartilage. RESULTS: On the T2 map, the maturation process until 10 weeks was characterized by a decrease in T2 values and in cartilage thickness. The biochemical data revealed a global decrease in proteoglycans and a progressive global increase in collagen content, whereas the histologic study revealed subtle zonal variation in matrix constituents with depth. As aging progressed, the T2 values were low, without important variations, whereas the global cartilage thickness decreased. The cartilage matrix became globally more fibrotic, especially in the deepest zone. Biochemical analysis revealed that collagen content was more determinant of MR signal intensity than was proteoglycans content during maturation and aging. CONCLUSION: T2 mapping allows characterization of variations in cartilage matrix constituents and thickness.
Asunto(s)
Envejecimiento , Cartílago Articular/química , Cartílago Articular/crecimiento & desarrollo , Imagen por Resonancia Magnética , Rótula , Animales , Cartílago Articular/citología , Proteoglicanos Tipo Condroitín Sulfato/análisis , Colágeno/análisis , Hidroxiprolina/análisis , Masculino , Ratas , Ratas WistarRESUMEN
The study of trabecular bone is receiving increasing interest within the medical community working in the field of skeletal diseases, such as osteoporosis. Quantification of trabecular bone structure usually requires as a starting point a correct segmentation of the trabecular network. We have developed a probabilistic relaxation labelling technique, which uses local features of the trabecular bone images to improve segmentation. Tests on synthetic images show that bone labelling performs a more accurate segmentation than conventional techniques such as thresholding, especially by preserving the connectivity of the trabecular network. Tests on acquired data show that porosity values obtained after segmentation are in good agreement with experimental values obtained by weighing the bone samples.