The purpose of this article is to provide a pictorial review of the findings and interpretative pitfalls about focal fluorodeoxyglucose(FDG)uptake in the absence of corresponding computer tomography(CT)lesion or abnor...The purpose of this article is to provide a pictorial review of the findings and interpretative pitfalls about focal fluorodeoxyglucose(FDG)uptake in the absence of corresponding computer tomography(CT)lesion or abnormality on an integrated positron emission tomography(PET)-CT.The integrated CT images in the PET-CT scanner allow correct co-registration and fused imaging of anatomical and functional data.On FDG PET-CT imaging,a real pathologic process often demonstrates abnormal uptake associated with a visible corresponding CT lesion or abnormality.When focal uptake is seen on PET imaging but no corresponding anatomic abnormality is visualized on the integrated CT,one should always be aware of possible mis-registration or mismatch of the PET and CT images due to the patient’s respiratory or body motion.While most of the hot spots in the absence of corresponding anatomic abnormalities are artefactual or secondary to benign etiologies,some may represent small sized or early staged neoplasm or metastases,especially in the gastrointestinal tract and skeletons.Caution should be exercised to simply diagnose a pathology based on the presence of the uptake only,or exclude the disease based on the absence of anatomic abnormality.展开更多
The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the sate...The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the satellite image.A physics-based bidirectional reflectance distribution function(BRDF)and atmospheric correction model in conjunction with a 1-second DSM was used to conduct the analysis in this paper.The results show that for the examples used from Australia,the 1-second DSM,can provide an effective product for this task.However,it was found that some remaining artefacts in the DSM data,originally due to radar shadow,can still cause significant local errors in the correction.Where they occur,false shadows and over-corrected surface reflectance factors can be observed.More generally,accurate co-registration between satellite images and DSM data was found to be critical for effective correction.Mis-registration by one or two pixels could lead to large errors of retrieved surface reflectance factors in gully and ridge areas.Using low-resolution DSM data in conjunction with high-resolution satellite images will also fail to correct significant terrain components where they occur at the finer scales of the satellite images.DSM resolution appropriate to the resolution of satellite image and the roughness of the terrain is needed for effective results,and the rougher the terrain,the more critical will be the accurate registration.展开更多
文摘The purpose of this article is to provide a pictorial review of the findings and interpretative pitfalls about focal fluorodeoxyglucose(FDG)uptake in the absence of corresponding computer tomography(CT)lesion or abnormality on an integrated positron emission tomography(PET)-CT.The integrated CT images in the PET-CT scanner allow correct co-registration and fused imaging of anatomical and functional data.On FDG PET-CT imaging,a real pathologic process often demonstrates abnormal uptake associated with a visible corresponding CT lesion or abnormality.When focal uptake is seen on PET imaging but no corresponding anatomic abnormality is visualized on the integrated CT,one should always be aware of possible mis-registration or mismatch of the PET and CT images due to the patient’s respiratory or body motion.While most of the hot spots in the absence of corresponding anatomic abnormalities are artefactual or secondary to benign etiologies,some may represent small sized or early staged neoplasm or metastases,especially in the gastrointestinal tract and skeletons.Caution should be exercised to simply diagnose a pathology based on the presence of the uptake only,or exclude the disease based on the absence of anatomic abnormality.
文摘The accuracy of topographic correction of Landsat data based on a Digital Surface Model(DSM)depends on the quality,scale and spatial resolution of the DSM data used and the co-registration between the DSM and the satellite image.A physics-based bidirectional reflectance distribution function(BRDF)and atmospheric correction model in conjunction with a 1-second DSM was used to conduct the analysis in this paper.The results show that for the examples used from Australia,the 1-second DSM,can provide an effective product for this task.However,it was found that some remaining artefacts in the DSM data,originally due to radar shadow,can still cause significant local errors in the correction.Where they occur,false shadows and over-corrected surface reflectance factors can be observed.More generally,accurate co-registration between satellite images and DSM data was found to be critical for effective correction.Mis-registration by one or two pixels could lead to large errors of retrieved surface reflectance factors in gully and ridge areas.Using low-resolution DSM data in conjunction with high-resolution satellite images will also fail to correct significant terrain components where they occur at the finer scales of the satellite images.DSM resolution appropriate to the resolution of satellite image and the roughness of the terrain is needed for effective results,and the rougher the terrain,the more critical will be the accurate registration.
