ABSTRACT
In ultrasound/computed tomography (CT) fusion images, ultrasound allows visualization of the target in real time. CT provides a navigation for ultrasound scanning and improves the overview in areas of limited visualization with ultrasound. This study was performed to investigate the feasibility of ultrasound/CT fusion based on an electromagnetic tracking technique using external fiducial markers for canine ocular and periocular regions. In 7 Beagle dogs, contrast-enhanced CT images of the head were obtained with placing external fiducial markers over the frontal region and both sides of the forepaws of the dog. Ultrasonography was performed under a magnetic field by installing a position sensor in the linear probe, without changing the dog's position. The positions of the external fiducial markers were adjusted and matched, based on the CT images. The execution time of co-registration and the distance between the regions of interest and the co-registration points, the frontal bone, cornea, retina, and optic nerve, were estimated. Approximately 60% of external fiducial markers were properly recognized in all dogs. After adjustment, all external fiducial markers were precisely matched. The co-registration execution time was less than 1 min. The distances between the regions of interest and co-registration points were less than 3 mm in all dogs. The electromagnetic tracking technique using external fiducial markers was a simple and applicable method for fusion imaging of a canine head using real-time ultrasonography and CT. This technique can be useful for interventional procedures of retrobulbar and periorbital lesions.
Subject(s)
Animals , Dogs , Cornea , Fiducial Markers , Frontal Bone , Head , Magnetic Fields , Magnets , Methods , Optic Nerve , Retina , Tomography, X-Ray Computed , UltrasonographyABSTRACT
Objective To study the predictive value of magnetic resonance imaging (MRI),positron emission computed tomography (PET)and PET/MRI coregistration in intractable epilepsy of children.Methods A retrospec-tively analysis was performed based on the surgery data at the Department of Children Epilepsy Center of Peking Univer-sity First Hospital from September 2015 to March 2016.The clinical data,surgery and follow－up study data,interictal and ictal electroencephalogram,MRI,PET and PET/MRI coregistration data were collected.By comparison with the epi-leptogenic zone designed by pre－surgical workup,the accuracy of MRI,PET and PET/MRI coregistration in detecting lesion was assessed.In the patients who had no seizure during≥1 year follow－up,their sensitivity,specificity,positive predictive value,negative predictive value of MRI,PET and PET/MRI coregistration were calculated.Results (1)A total of 62 patients underwent surgery,30 boys and 32 girls. The average age on epilepsy onset was 2. 50 years (2 days－11.70 years),and average age on surgery was 5.10 years old(0.75－15.60 years old).(2)Surgical treat-ment of 62 cases included the resection of the focal or lobar (32 cases,51.6%),and the multilobar (16 cases, 25. 8%).Hemispherotomy was done in 14 cases (22.6%).During ≥1 year follow－up,seizure outcome was Engel class Ⅰ in 57 cases (91.9%)out of the 62 patients,Engel classⅡto Engel classⅣin 1 case,3 cases,and 1 case, respectively.(3)Referred to epileptogenic zone designed by presurgical workup,MRI represented 64.5%(40/62 ca-ses)results with accordance,PET and PET/MRI coregistration was 72.5%(45/62 cases)and 85.5%(53/62 cases), respectively,and the difference was significant(χ2＝7.25,P＝0.03).(4)Based on the patients of Engel class Ⅰ, their sensitivity and specificity were 66.7%,60.0% in MRI,75.4%,60.0% in PET %,and 85.9%,80.0% in PET/MRI coregistration,respectively.(5)There were 11 ＂non－lesion＂ cases of all focal cortical dysplasia in patholo-gy,and subtle structural abnormalities were de tected in 9 cases by reviewing MRI.Conclusions PET/MRI coregistra-tion can improve lesion detection of intractable epilepsy in children.
ABSTRACT
Objective Introduce a technique for creating 3-dimensional (3D) brain models of subdural electrodes , ideal for demonstrating the space-relationship of seizure localization and eloquent cortices , and discuss its usefulness for presurgical evaluation of epileptic patients. Methods Patients with medically intractable epilepsy were underwent a thorough preoperative MR brain scan including a T1-weighted high-resolution 3D sequence. Intraoperative photographs were taken with the digital camera. After the surgical implantation of subdural electrodes for epileptic zone localization , the thin-slice CT scan of the electrodes were taken and coregistered to preoperative brain 3D MR images in the Medtronic StealthMerge software environment. After the iEEG monitoring , multiple habitual seizures were recorded , eloquent areas were also identified by electrical stimulation of the cortex. The epileptic zone and the eloquent areas were marked on the subdural electrodes respectively. Then, 3D tessellations of the epileptic zone and the eloquent areas were rendered. Results Six patients (4 male, 2 female) were enrolled in this study. The mean time of iEEG monitoring was 13.7 days. After the coregistration of postoperative CT with preoperative 3D MRI , the 3D stereoscopic reconstruction provided an accurate representation of the implanted electrodes with highly detailed visualization of the underlying anatomy. The visual comparison between 3D reconstructions and intraoperative photographs indicated a good correspondence. The patients were followed for 3 to 6 months after the secondary operation , and had continuing improvement in seizure control. Conclusions The results indicate that the 3D reconstruction of subdural electrodes can reveal the precise localization of subdural electrodes , and can be useful for the presurgical evaluation of epileptic patients.
ABSTRACT
The interpretation of nuclear medicine studies is largely based on function. However, this interpretation becomes more accurate and reliable when there is a corresponding precise anatomical localization. Hybrid systems are opening up a new era in SPECT imaging. A tertiary hospital in the Philippines has acquired the country's first hybrid imaging device combining a dual-detector, variable angle gamma camera with a low dose X-ray tube attached to the same gantry. This study evaluates the clinical utility of a hybrid imaging system, SPECT/CT for functional mapping with selected radiotracers. SPECT data were first interpreted alone and then re-assessed with the addition of SPECT/CT co-registered images. Patients referred for various nuclear medicine procedures with SPECT components in the first six months of operation studied for various clinical situations were evaluated in the study. Our study included sixty-four (64) patients in the first year of operation of SPECT/CT co-registered imaging systems. This included 23 with I-131, six with sulfur colloid, four with Gallium 67, five with Tc99m Sestamibi and 26 with Tc99m HOP. The pathologic sites in 28 out of 64 (44 percent) patients were noted in both SPECT and SPECT/CT co-registered images. Additionally, SPECT/CT co-registered images provided the precise anatomical localization in 12 (19 percent) patients not clearly evident in SPECT images alone and enabled the exclusion of disease in sites of physiologic tracer deposition in 16 (25 percent) patients found suspicious in SPECT alone leading to a change in the therapeutic approach. SPECT/CT allows a more precise interpretation of scintigraphic studies using selected radiotracers for various clinical situations. It provides additional information that improves diagnostic accuracy of SPECT and impacts on patient management indicating that SPECT/CT co-registered systems are suited for routine use in clinical practice.
Subject(s)
Humans , Male , Female , Colloids , Gallium , Gamma Cameras , Multimodal Imaging , Nuclear Medicine , Philippines , Radionuclide Imaging , Sulfur , Technetium Tc 99m Sestamibi , Tertiary Care Centers , Tomography, Emission-Computed, Single-Photon , Tomography, X-Ray Computed , X-RaysABSTRACT
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.