A new method for representing the human anatomy.

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.

A computerized three-dimensional atlas of the human skull and brain.

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.

Improvement of 3D acquisition and visualization in MRI.

Three-dimensional (3D) visualization techniques are becoming an ever more important aid in the interpretation of tomographic data. Up to now, however, they have not received widespread use in MRI, because both acquisition and visualization techniques have been inadequate. In this paper we describe new 3D acquisition techniques which can acquire up to 128 slices with a resolution of 256 x 256 pixels in from 8 to 20 min. These techniques produce 3D data sets with excellent contrast and few motion artifacts, which are very well suited for 3D visualization techniques. For the visualization we investigate several rendering techniques, describe some improvements and compare their results. We found that there is no single method which renders all objects equally well. We show which shading method is best suited for different objects and why the other methods fail. Our studies suggest that in a 3D view with several objects each object should be rendered with a separate shading method. In so doing, 3D views can be generated which look like the real human anatomy.

3-D segmentation of MR images of the head for 3-D display.

Algorithms for 3-D segmentation and reconstruction of anatomical surfaces from magnetic resonance imaging (MRI) data are presented. The 3-D extension of the Marr-Hildreth operator is described, and it is shown that its zero crossings are related to anatomical surfaces. For an improved surface definition, morphological filters-dilation and erosion-are applied. From these contours, 3-D reconstructions of skin, bone, brain, and the ventricular system can be generated. Results obtained with different segmentation parameters and surface rendering methods are presented. The fidelity of the generated images comes close to anatomical reality. It is noted that both the convolution and the morphological filtering are computationally expensive, and thus take a long time on a general-purpose computer. Another problem is assigning labels to the constituents of the head; in the current implementation, this is done interactively.

[Functional imaging of blood flow velocity amd myocardial perfusion using the Fourier transform parameter]. / Funktionsbilddarstellung der Blutflussgeschwindigkeit sowie der Myokardperfusion durch Parameter der Fouriertransformation.

In the past, the radiology of the cardiovascular system has consisted of angiographic investigations which only demonstrate morphology. The introduction of digital techniques into radiology has made possible the demonstration of pure morphology and beyond that, calculations which provide functional information. We demonstrate functional images which, by using Fourier transformations, provide information on blood flow and organ perfusion. In this way, it is possible to obtain important additional diagnostic information concerning the cardiovascular system, without imposing any further stress on the patient.