ABSTRACT
Objetivo: Determinar la efectividad del co-registro de imágenes PET/RM (tomografía de emisión de positrones y resonancia magnética) en el diagnóstico de recidiva tumoral vs.. radionecrosis en pacientes con patología tumoral cerebral primaria previamente tratados. Material y métodos: El diagnóstico de tumor cerebral se determinó por RM e histopatología. Después de 3 a 5 meses postratamiento se realizó RM y PET como parte del seguimiento. El análisis de dichas imágenes se hizo de manera visual y semicuantitativa mediante la obtención de un índice de captación de 18F-FDG de tejido tumoral/ tejido cerebral sano. Resultados: Se estudiaron 57 pacientes; un total de 37 gliomas astrocíticos, 9 gliomas mixtos, 5 tumores embrionarios, 1 tumor meníngeo y 1 tumor oligodendroglial . Todas las imágenes de RM presentaban áreas de reforzamiento, dejando sospecha entre radionecrosis o viabilidad tumoral; con el co-registro PET/RM se diagnosticaron 21 estudios negativos (30 %) y 36 positivos (70 %). El índice tejido tumoral/tejido cerebral sano se correlacionó adecuadamente con los resultados visuales obtenidos. Conclusión: La RM sobreestima el área tumoral a valorar. La presencia de la actividad metabólica analizada mediante PET sobre las áreas de reforzamiento por RM permite determinar la presencia de viabilidad tumoral. Esto aumenta la certeza diagnóstica de ambas técnicas de imagen.
OBJECTIVE: To evaluate the role of PET and MRI fused image study inpatients with primary brain tumors previously treated, to determine the presence of radionecrosis vs residual tumor viability. METHODS: Primary brain tumors were diagnosed by biopse and MR. 18FDG-PET scan and T1 enhanced MRI follow-up studies were performed between 3 and 5 months after treatment. The 18F-FDG uptake was semiquantitavively calculated by a region-of-interest based Tumor hotspot/normal brain tissue index. RESULTS: Fifty-seven patients were studied, 37 had high grade gliomas; 9 had oligoastrocytomas; 5 had Embrionary tumors; I had a meningyoma and I had an oliodendroglial tumor. All MR studies showed tumor enhancement, without determine wether if it was radionecrosis or tumor viability. PET/MR fused study diagnosed 21 negative studies (30%) and 36 positive results (70%). Tumor hotspot/normal brain tissue index correlated well with the visual analysis registered. CONCLUSIONS: Visual analysis in the contrast enhanced MR overestimates the tumoral area, without defining a possible diagnosis between tumor viability and radionecrosis. Metabolic activity in the 18F-FDG PET study in the enhanced area, determines the presence of residual tumor viability. Therefore, coregistration can be used to obtain a more specific diagnosis optimizing the cinical use.
Subject(s)
Humans , Male , Female , Adolescent , Adult , Middle Aged , Radiopharmaceuticals , Glioma/diagnosis , Glioma , Magnetic Resonance Imaging/methods , Brain Neoplasms/diagnosis , Brain Neoplasms , Positron-Emission Tomography/methods , Data Interpretation, Statistical , Diagnosis, Differential , Radiation Injuries/diagnosis , Radiation Injuries , Models, Theoretical , NecrosisABSTRACT
PURPOSE: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. MATERIALS AND METHODS: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. RESULTS: Using our newly developed method, robust extraction of head boundary was possible and spatial regishation was successfully performed. Mean displacement error was less than 2.0mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. CONCLUSION: Our refined technique could practically enhance the performance of automated three dimensional coregistration.