Retinal fundus photographs are employed as standard diagnostic tools in ophthalmology. Serial photographs of the flow of fluorescein and indocyanine green (ICG) dye are used to determine the areas of the retinal lesions. For objective measurements of features, the registration of the images is a necessity. In this paper, we employ optimization techniques for registration with the help of 2-parameter translational motion model of retinal angiograms, based on non-linear pre-processing (Wiener filtering and morphological gradient) and computation of the similarity criteria for the alignment of the two gradient images for any given rigid transformation. The optimization methods are effectively employed to minimize the similarity criterion.
The presence of noise, the variations in the background and the temporal variation of the fluorescence level pose serious problems in obtaining a robust registration of the retinal images. Moreover, local search strategies are not robust in the case of ICG angiograms, even if one uses a multiresolution approach.
The present work makes a systematic comparison of different optimization techniques, namely the minimization method derived from the optical flow formulation, the Nelder-Mead local search and the HCIAC ant colony metaheuristic, each optimizing a similarity criterion for the gradient images. The impact of the resolution and median filtering of gradient image is studied and the robustness of the approaches is tested through experimental studies, performed on macular fluorescein and ICG angiographies.
Our proposed optimization techniques have shown interesting results especially for high resolution difficult registration problems. Moreover, this approach seems promising for affine (6-parameter motion model) or elastical registrations. 相似文献
We report the MRI features in a series of four patients with primary angiitis of the central nervous system (PACNS). Based on MRI features, clinical presentation, paraclinical investigations and laboratory tests, including cerebrospinal fluid (CSF) analysis, various differentials were considered. In two patients with MRI findings of cortical, subcortical and deep white matter lesions, lack of mass effect, focal areas of bleed and heterogeneous parenchymal, leptomeningeal or pial enhancement and a normal magnetic resonance angiography, a differential diagnosis of primary angiitis of the CNS was also considered. In all patients, an open brain biopsy was advised to establish a definitive diagnosis of PACNS. Here, we briefly discuss the MRI features, correlation with clinical presentation and paraclinical parameters for the diagnosis of this entity. We also briefly review the literature. 相似文献
The diagnosis of acute disseminated encephalomyelitis (ADEM) is frequently missed or delayed with consequent delay in instituting therapy in the crucial phase of the illness. The role of MRI in the diagnosis of ADEM is well established, however, the value of its early utilization of treatment on the outcome of patients has not been adequately stressed. Three patients with ADEM are described. Delay in the diagnosis of the first was associated with severe sequelae, while in the other two early diagnosis and institution of corticosteroid therapy which was facilitated by MRI, was associated with a better outcome. MRI should be carried out early once the diagosis of ADEM is entertained. 相似文献
A case of cystadenocarcinoma of the liver is reported. The patient was a 73-year-old woman in whom a tumor was detected in
the lateral segment of the liver during a health examination. Ultrasonograms and computed tomograms showed a multilocular
cystic mass. Magnetic resonance imaging (MRI) showed a multilocular lowintensity mass, including a high-intensity portion
and a portal branch compressed by the tumor. MRI with gadolinium showed an enhanced cyst wall. The cystic part of the tumor
became smaller and the solid part became larger over a 1-month period, indicating that the tumor was malignant. Subsegmentectomy
(S3) was performed and cystadenocarcinoma with cystadenoma was diagnosed by histopathological examination. Identification of
changes in the appearance of a tumor should be helpful for the differential diagnosis of cystadenoma and cystadenocarcinoma. 相似文献