Biomedical subjects
Publications and source records attributed to M Riemer.
By integrating concepts of computer graphics and artificial intelligence, novel ways of representing medical knowledge become possible. They allow unprecedented possibilities ranging from three-dimensional interactive atlases to systems for surgery rehearsal.
It is a drawback of classical multimedia programs for the visualization of spatial knowledge, that they are based on a limited number of predefined views. This paper describes a model that combines pictorial and symbolic knowledge about spatial structures in a way that allows arbitrary views of the scene and the interrogation of the model in the context of the actual view. The style of the pictorial presentation only depends on the objective and the phantasy of the user. The functionality of the approach is demonstrated with the example of the human head. It is furthermore shown that the model potentially allows the simulation or generation of all classical visual teaching aids for anatomy.
Explore the source record for details and available documents.
In current practice, anatomical atlases are based on a collection of planar images presented in a book or, recently, stored on digital media. We present a new kind of interactive true three-dimensional (3D) anatomical atlases based on a volume model derived from MRI and CT. The model has a two-layer structure. The lower level is a volume model with a set of semantic attributes connected to each voxel. The semantic attributes are assigned by an anatomist using a volume editor. THe upper level represents a set of relations between these attributes. Interactive visualization tools such as multiple surface display, preparation of transparent material and cutting are provided. It is shown that the combination of this model with advanced tools for volume visualization provides the 'look and feel' of real dissection. The system therefore represents a bridge between real dissection of a cadaver and textbooks and classical atlases of anatomy. First tests have shown that the atlas system may be used successfully for teaching anatomy, but also as a reference for radiologists or surgeons. The powerful underlying data structure potentially includes all classical visual teaching aids. As a replacement of classical atlases, however, spatial resolution has still to be improved.
The treatment planning for radiotherapy with fast neutrons requires modifications of the planning systems used for photons. The neutron- and photon-component of the treatment fields must be determined and can then be used for separate calculations. The corrections for inhomogeneities are performed by use of attenuation coefficients and the corresponding corrections for changes in the kerma. The treatment planning system MEVAPLAN (Siemens) was modified to follow these requirements. Thus treatment planning for 14 MeV DT-neutrons could be performed. The multiplanar option is used to calculate 3D-dose distributions based on up to 40 serial CT slices. The generated three-dimensional dose matrix and the CT data are transferred via magnetic tape to the visualization system VOXEL-MAN developed at the University Hospital of Hamburg. This system uses a ray casting algorithm based on the generalized Voxel-model to display detailed 3D-images of human anatomy together with the calculated dose distribution. Different treatment plans for neutrons and photons are calculated and visualized. Various manipulations of the data-sets are displayed to improve the critical examination of the simulated dose distribution and to discern the quality of treatment techniques.
The 3D-visualization of the entire spatial radiation dosage in cooperation with the 3D-radiation volume requires several data volumes. The structure of the interface between the 3D-treatment planning program "ProPlan" and the 3D-imaging system "VOXEL-MAN" is explained. The first results in the radiological application point out the possibilities of the complex registration of dose distributions and the critical examination of the irradiation technique.
Digital angiography has achieved broad clinical application as a morphological imaging modality through the technique of temporal subtraction known as digital subtraction angiography (DSA). After applying the Fourier transform to the intensity time curves (ITC) of an angiographic sequence, we are able to produce both morphological and functional images. The resulting pictures show an improved signal-to-noise ratio, reduction of motion artifacts, easy application of phase-synchronous subtraction, and integration and quantitative visualization of blood flow. The methods are demonstrated with nonselective angiograms and intravenous levocardiograms. Furthermore, when applied to angiographic sequences, the Fourier transform leads to a significant reduction in data without loss of important information.
With the use of a digital image-processing method three-dimensional reconstructions of the arrangement of spermatocytes in human seminiferous tubules were performed. With this method it was possible to investigate the cellular distribution in the tubule in nearly any given perspective and projection. In addition, by means of simple mathematical procedures, such as by transformation of Cartesian coordinates into cylindrical coordinates, it was possible to vary the shape of a reconstruction, i.e., to convert the cylindrical image of a tubular portion into a right-angled r-phi-z-representation. The present work not only confirms the existence of a complex helical plan of organization of the human seminiferous epithelium but also provides further aspects of the phenomenon of physiological germ-cell loss and its integration into the kinetics of spermatogenesis.
Craniofacial anomalies are conventionally investigated by cephalometry using ordinary radiographs and by computed tomography. Both methods have the major disadvantage of trying to demonstrate a complex three-dimensional structure, such as the skull, in two dimensions and they therefore cannot display a true spatial image. We present the principle underlying a three-dimensional display derived from computer tomographic studies and discuss the clinical application in the diagnosis of craniofacial anomalies.
Testicular tissue of two adult crab-eating macaques was used to investigate the distribution of the spermatids in the seminiferous tubules. For this purpose, morphological criteria for distinction among the various degrees of development of these cells were elaborated. Subsequently, based upon analyses of serial sections, three-dimensional reconstructions of the cellular distribution pattern were generated by means of digital image processing. In these reconstructions it became evident that the spatial extension of a single differentiation stage can vary considerably. Large tubular portions that contained a single differentiation stage alternated with those exhibiting several differentiation stages which occupied only small patch-like areas of the seminiferous epithelium. Particularly in the latter portions of the tubule a helical continuity of subsequent stages in the sense of a wave of spermatogenesis became immediately obvious. Transitory changes in the direction of the wave (modulations) occurred frequently. The present findings support the suggestion that an uniform kinetic principle of mammalian spermatogenesis exists, which is subjected to slight modifications during the evolution of primates.
The significance of digital examination methods continues to grow. Since the introduction of computer tomography, two additional digital imaging modalities-digital subtraction angiography (DSA) and magnetic resonance imaging (MRI)--have been developed. In this paper we present basic techniques of computerized image processing and outline foreseeable future developments. Furthermore, we discuss the possibilities and problems presented by digital picture archiving and communication systems (PACS).
PURPOSE: To develop an anatomic atlas of the human head based on a volume model derived from MR and CT. METHODS: Every voxel of this model was labeled by a neuroanatomist concerning its membership to a structural and/or functional region. A computer program was written that, instead of displaying precomputed images, allows the user to choose and compose arbitrary views. RESULTS: The user can subtract parts and ask for annotations just by using the mouse. Conversely, one can compose images by choosing objects from the list of anatomical constituents which is displayed on the screen. A set of dissection tools allows a "look and feel" that comes near to a true dissection. Operations that are not possible in a real dissection, such as reassembly or filling cavities, can be performed. CONCLUSION: The authors have developed a computerized model that can be used for anatomy teaching and also as a reference for radiologists or surgeons. To replace classical atlases, the spatial resolution must be improved and speed must approach real time. Functional imaging data (position emission tomography and single photon emission CT) can be added to the system. The system is mobile and can be situated in classrooms, operating rooms, reading rooms, and libraries.
In current practice, anatomical atlases are based on a collection of planar images presented in a book or, recently, stored on digital media. We present a new method for generating interactive true three-dimensional (3D) anatomical atlases based on a volume model derived from MRI and CT. The model has a two layer structure. The lower level is a volume model with a set of semantic attributes connected to each voxel. The semantic attributes are assigned by an anatomist using a volume editor. The upper level is a set of relations between these attributes. Interactive visualization tools such as multiple surface display, transparent rendering, and cutting are provided. It is shown that the combination of this data structure with advanced volume visualization tools provides the "look and feel" of real dissection. First tests show that the atlas system cannot only be used successfully for anatomy teaching, but also as a reference for radiologists or surgeons. As a replacement of classical atlases, however, the spatial resolution has still to be improved.
While digital techniques in radiology develop rapidly, problems arise with archival storage and communication of image data. This paper reports on experiments concerning data reduction of digital image sequences of the heart and the brain. The time-intensity curves corresponding to every picture element are subjected to the Fourier transform and reconstructed from a number of coefficients smaller than the original number of images. The reconstruction error is assessed by visual inspection and by determining the mean-square deviation of the original and the reconstructed curve. It is shown that compression factors between 5 and 10 may be achieved without loss of diagnostic information. It is furthermore demonstrated that storage of the images in the form of Fourier coefficients leads to advantages in fast retrieval, enhancement of morphology, and possibility of further quantitative analysis.