Biomedical Engineering: Applications, Basis and Communications

In the diagnosis of hepatic diseases, “Contrast-Enhanced Computerized Tomography” (CECT) and “Non-Contrast CT” (NCT) are usually simultaneously adopted. In this paper, a system consisting of a fuzzy diagnosis engine and a feature quantizer, which extracts hepatic features from CECT and NCT images, is proposed for assisting hepatic disease diagnosis. Compared with existing methods, this paper differs in two folds. First, a more complete feature set composed of not only lesion textures, but also lesion morphological structure and lesion contrast to normal tissues is used. These features are described through mathematical models built inside the feature quantizer and served as the input of fuzzy diagnosis engine. Second, because of the use of the fuzzy diagnosis engine, the system is intrinsically with the capability of storing rules and may infer and adapt its rules according to learning data. Furthermore, uncertainty associated with disease diagnosis can be appropriately taken into considerations. The system has been tested using 131 sets of image data, which are to be classified into 4 types of diseases: liver cyst, hepatoma, cavernous hemagioma and metastatic liver tumor. Experimental results indicate that among these test data 78% of them are accurately classified as one type, while the remaining 22% of data are classified as more than one types of diseases. Even so, within these 22% of multiple-classified data, the correct type is always included in the output in each test, showing a promise of the system.

Drilling tools currently used in surgery depends only on the surgeon's manual skills to stop the penetration when completing a hole. This paper presents a modular mechatronic system for automatic bone drilling in surgery. The development of a “modular system” that is compatible with motor-driven drills that are commercially available, rather than developing a new surgical drill, is emphasized. A fuzzy controller analyzes the electric current consumed by the DC motor of the drill. When break-through is detected, the power will be cut and stops drilling in order to prevent excessive protrusion of the drill bit. In extensive drilling tests on real human skulls, there were no unexpected failure, and the overshoots of all tests were well less than 2mm.

The assessment of vascular structure gives important information on pathological processes, particularly for the investigation of diseased vessels. In this study the Mulvany wire myogarph is adapted for spectroscopic examination of small arterial blood vessels obtained from hypertensive and normal rat specimens. An experimental study of 20 vessels obtained from adult Wistar rats and Goldblatt (one kidney one clip) hypertensive rats was carried out. Segments of small resistance arteries mounted under isometric conditions on a wire myograph and set to normalised conditions of passive force directly obtained from its circumferential length-tension relationship were morphologically examined and transmission spectra obtained. Features of the observed transmission spectra were extracted by means of an empirical non-linear model using the quasi-Newton method. These features were correlated for the first time with standard descriptors of vessel morplzology, media:lumen ratio and with arterial blood pressure. The extent and significance of such correlations are sufficient to distinguish the presence of hypertension in isolated arterial segments from hypertensive animals. This technique may provide an alternative to light microscopy as well as a potential new tool for the analysis of small blood vessels in the study of vascular disease.

Maximum likelihood estimate (MLE) is a widely used approach for PET image reconstruction. However, it has been shown that reconstructing emission tomography based on MLE without regularization would result in noise and edge artifacts. In the attempt to regularize the maximum likelihood estimate, we propose a new and efficient method in this paper to incorporate the correlated but possibly incomplete structure information which may be derived from expertise, PET systems or other imaging modalities. A mean estimate smoothing the MLE locally within each region of interest is derived according to the boundaries provided by the structure information. Since the boundaries may not be correct, a penalized MLE using the mean estimate is sought. The resulting reconstruction is called a cross-reference maximum likelihood estimate (CRMLE). The CRMLE can be obtained through a modified EM algorithm, which is computation and storage efficient. By borrowing the strength from the correct portion of boundary information, the CRMLE is able to extract the useful information to improve reconstruction for different kinds of incomplete and incorrect boundaries in Monte Carlo studies. The proposed CRMLE algorithm not only reduces the estimation errors, but also preserves the correct boundaries. The penalty parameters can be selected through human interactions or automatically data-driven methods, such as the generalized cross validation method.

The purpose of this paper is to examine the relationship between the control parameters and the tumor/bone conditions, and also to determine the domain determined by the treatable tumor size and tumor depth for an external ultrasound hyperthermia. This work employs computer simulation programs based on a simplified model of a scanned ultrasound transducer power deposition, the steadystate bio-heat transfer equation, and a search algorithm. The low bounds of SR (specific absorption rate ratio) and f · SR (f : ultrasound frequency) are determined based on the temperature distributions for large ranges of blood perfusion and ultrasound frequencies. These low bounds of SR and f · SR are then used to investigate the relationship between the control parameters and the tumor/bone conditions and to determine the treatable domain. The control parameters considered are the acoustic window size, ultrasound frequency; and the tumor/bone conditions are tumor size, tumor depth, and the depth of post-target bone. Simulation results demonstrate that a) the low bounds of SR and f · SR are functions of blood perfusion; b) the ultrasound frequency to obtain the largest treatable tumor size depends on the tumor depth and the depth of post-target bone, however it is independent of the acoustic window size; and c) the treatable domain is proportional to the acoustic window size and the depth of post-target bone, and a proper frequency can result in a larger treatable domain. The results of this study can be a guideline for designing an optimal ultrasound heating system, arranging the transducers, and implementing further treatment planning for the external ultrasound hyperthermia.