High-resolution flat-panel volume-CT of temporal bone--part 1: axial preoperative anatomy.
ABSTRACT The purpose of this four-part series is to show the high-resolution axial and coronal anatomy of the temporal bone from a flat-panel detector-based volume CT (parts 1 and 2); these imaging planes are then used to outline the effect of different surgical procedures commonly applied to the temporal bone (parts 3 and 4). The structures that are removed or altered in 11 different surgical procedures are color-coded and inscribed in axial and coronal sections. Clinically important imaging features and complications following these surgeries will also be discussed. In these high-resolution images, many structures that are below the resolution limit of conventional CT can be seen and localized. It is hoped that one would be able to picture these structures and surgeries, in the mind's eye, even when they fall below the resolution limit using a conventional CT scanner. This article (part 1) focuses on the preoperative axial anatomy.
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ABSTRACT: The development and performance of a system for x-ray cone-beam computed tomography (CBCT) using an indirect-detection flat-panel imager (FPI) is presented. Developed as a bench-top prototype for initial investigation of FPI-based CBCT for bone and soft-tissue localization in radiotherapy, the system provides fully three-dimensional volumetric image data from projections acquired during a single rotation. The system employs a 512 x 512 active matrix of a-Si:H thin-film transistors and photodiodes in combination with a luminescent phosphor. Tomographic imaging performance is quantified in terms of response uniformity, response linearity, voxel noise, noise-power spectrum (NPS), and modulation transfer function (MTF), each in comparison to the performance measured on a conventional CT scanner. For the geometry employed and the objects considered, response is uniform to within 2% and linear within 1%. Voxel noise, at a level of approximately 20 HU, is comparable to the conventional CT scanner. NPS and MTF results highlight the frequency-dependent transfer characteristics, confirming that the CBCT system can provide high spatial resolution and does not suffer greatly from additive noise levels. For larger objects and/or low exposures, additive noise levels must be reduced to maintain high performance. Imaging studies of a low-contrast phantom and a small animal (a euthanized rat) qualitatively demonstrate excellent soft-tissue visibility and high spatial resolution. Image quality appears comparable or superior to that of the conventional scanner. These quantitative and qualitative results clearly demonstrate the potential of CBCT systems based upon flat-panel imagers. Advances in FPI technology (e.g., improved x-ray converters and enhanced electronics) are anticipated to allow high-performance FPI-based CBCT for medical imaging. General and specific requirements of kilovoltage CBCT systems are discussed, and the applicability of FPI-based CBCT systems to tomographic localization and image-guidance for radiotherapy is considered.Medical Physics 07/2000; 27(6):1311-23. · 2.91 Impact Factor
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ABSTRACT: Clinical CT has reached a very high performance level by now. The introduction of spiral scanning and of multirow detectors have allowed to image even large body sections in very short time and with isotropic, high spatial resolution of better than 1 mm. For further improvements with respect to detector technology the use of flat-panel detectors (FPD), which have been developed for radiographic applications, is currently under investigation. In this article we discuss the general demands on CT detectors and specifically the suitability of FPDs with respect to CT imaging. FPDs offer excellent performance for the imaging of high-contrast structures with high spatial resolution.Low-contrast resolution and dose efficiency, however, do not yet reach the level of performance of dedicated CT detectors; temporal resolution is also limited. FPDs appear primarily suited for special applications in CT as for example 3D angiography or intraoperative imaging which also allows for improvements in workflow. For standard diagnostic CT they are not to be recommended at present, last but not least for dose reasons. The respective technical developments will have to be reassessed constantly in the future. The development of detector systems which are equally suited for radiography and CT constitutes an attractive goal.Der Radiologe 06/2003; 43(5):379-87. · 0.47 Impact Factor
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ABSTRACT: A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution as compared with a multi-section CT (MSCT) scanner. Our purpose was to determine how well a prototypical volume CT (VCT) scanner with a flat-panel detector system defines fine structures in temporal bone. Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel detector system at an isometric resolution of 150 microm at the isocenter. These specimens were also depicted by state-of-the-art multisection CT (MSCT). Forty-two structures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT. Qualitative assessment of anatomic structures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P < .001). Structures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduct, the interscalar septum, and the modiolus) had higher contrast and less partial-volume effect with VCT. The flat-panel prototype provides better definition of fine osseous structures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.American Journal of Neuroradiology 09/2004; 25(8):1417-24. · 3.17 Impact Factor