Bruce D. Doust

Knowledge-based method for segmentation and analysis of lung boundaries in chest X-ray images.

We present a knowledge-based approach to segmentation and analysis of the lung boundaries in chest X-rays. Image edges are matched to an anatomical model of the lung boundary using parametric features. A modular system architecture was developed which incorporates the model, image processing routines, an inference engine and a blackboard. Edges associated with the lung boundary are automatically identified and abnormal features are reported. In preliminary testing on 14 images for a set of 18 detectable abnormalities, the system showed a sensitivity of 88% and a specificity of 95% when compared with assessment by an experienced radiologist.

The Cerebellopontine Angle: Does the Translabyrinthine Approach Give Adequate Access?

A long‐standing but unfounded criticism of the translabyrinthine approach is the misperception that this approach does not give adequate access to the cerebellopontine angle. Because of what is perceived as limited visualization and operating space within the cerebellopontine angle, some surgeons still believe that the translabyrinthine approach is inappropriate for large acoustic tumors. In this study, the surgical access to the cerebellopontine angle by virtue of the translabyrinthine approach is measured and analyzed. The parameters are compared with those measured for the retrosigmoid approach. This series objectively confirms that the translabyrinthine approach offers the neurotologic surgeon a shorter operative depth to the tumor, via a similar‐sized craniotomy. This permits superior visualization by virtue of a wider angle of surgical access. Such access is achieved with the merit of minimal cerebellar retraction.

Model-based assessment of lung structures: inferencing and control system

A general methodology has been developed for computer interpretation of medical images, based on an explicit anatomical model. A test system for analyzing posterior- anterior (PA) chest x-rays has been implemented. The inferencing and control system identifies the major lung structures in the image, and then flags any suspected abnormalities. Image and model data are transformed into a feature space where they are represented in terms of edge descriptions. The inference engine compares the image and model in feature space to label the edges anatomically, and check for normality. The control system schedules events within the inference engine and coordinates interaction with the model and image processing routines. The control architecture is blackboard-based, with a separate data frame for each structure to be identified. The anatomical model uses fuzzy sets to provide ranges of feature values which are considered normal or indicative of a particular abnormality. This allows the inference engine to give a confidence score and linguistic description to each decision. Mediastinum, cardiac border, domes of the diaphragm, ribs and lung outline have been modeled. Their automatic identification allows diagnostic checks such as the cardiothoracic ratio, comparison of right and left lungs to identify lobular collapse and inspection of interfaces in terms of shape and clarity. The inference engine provides simple comments on its findings, making it suitable for pre- and double-checking of images.

A radiologic study of the tympanic bone: anatomy and surgery.

Objective The aim of this study was to obtain data on the anatomic structure of the tympanic bone using parasagittal reformatted images created from high-resolution axial computed tomographic scans. In particular, the thickness of the bone in the region of the temporomandibular joint and the floor of the external auditory canal was assessed. The findings are discussed with particular emphasis on the relevance to surgery in this area. Background Surgical management of the tympanic bone forms the basis of canalplasty, which is an essential step in the management of disorders of the external auditory canal. Adequate canalplasty is also crucial in the provision of access for tympanoplasty and to ensure optimal cavity geometry in canal wall down mastoidectomy. Tympanic bone removal is a major step in approaches to the lateral skull base and infratemporal fossa. The tympanic bone is also important because it has critical neurovascular relations in this region of the skull base. Methods Computed tomography of the tympanic bone (parasagittal reformatted images) in 54 consecutive adults. Results The mean thickness of the anterosuperior, anteroinferior, and inferior aspects of the tympanic bone are 2.6, 2.8, and 8 mm, respectively. Conclusion Canalplasty is safely performed in the regions outlined. The technique of canalplasty described in this article is essential for good exposure in external ear, middle ear, mastoid, and skull base surgery