生物工程与生物医学杂志

Image segmentation is an important task involved in different areas from image processing to image analysis. One of the simplest methods for image segmentation is thresholding. However, many thresholding methods are based on a bi-level thresholding procedure. These methods can be extended to form multi-level thresholding, but they become computationally expensive because a large number of iterations would be required for computing the optimum threshold values. In order to overcome this disadvantage, a new method based on a Shrinking Search Space (3S) algorithm is proposed in this paper. The method is applied on statistical bi-level thresholding approaches including Entropy, Cross-entropy, Covariance, and Divergent Based Thresholding (DBT), to achieve multi-level thresholding and used for intracranial segmentation from brain MRI images. The paper demonstrates that the impact of the proposed 3S technique on the DBT method is more significant than the other bi-level thresholding approaches. Comparing the results of using the proposed approach against those of the Fuzzy C-Means (FCM) clustering method demonstrates a better segmentation performance by improving the similarity index from 0.58 in FCM to 0.68 in the 3S method. Also, this method has a lower computation complexity of around 0.37s with respect to 157s processing time in FCM. In addition, the FCM approach does not always guarantee the convergence, whilst the 3S technique always converges to the optimum result.

Objective:The objective of this study was to test a newly developed implant for the treatment of intertrochanteric fractures, the X-Bolt, against the current gold standard, the Dynamic Hip Screw (DHS), by comparing the amount of energy required to cause failure of both of them.

Methods:Push out studies were performed with both the dynamic hip screw and the X-Bolt in an artificial bone substrate in the form of polyurethane foam blocks, which have predefined mechanical properties. These push out studies were performed as a means to investigate each implants resistance to ‘cut out’ as this is the most common mode of failure with the DHS.

Results: The results demonstrate that the X-Bolt produced a force displacement curve with a different pattern of failure than the DHS. The X-Bolt initially required less energy to move it within the test material, than the DHS. However, the further the X-Bolt advanced within the test material, the greater the resistance and as this was the opposite as to what occurred with the DHS, the X-Bolt eventually required more energy than the DHS to advance through the test material and fail due ‘cut out’.

Conclusion:The X-Bolt is a new concept with regard to fixation of intertrochanteric fractures. It produces a different force displacement curve than the dynamic hip screw. However further investigations are necessary before the true potential of this new implant is known.

Oral malodor, also called halitosis or bad breath, is universally experienced condition that has a variety of etiologic factors. It is extremely common and majority of adult population have had it at some point in time. Halitosis may be physiological, pathological, and sometimes psychological also. Although numerous non-oral sites and many different causes have been correlated to bad breath, an estimated 80 percent to 90 percent of all bad breath odors originate from the mouth, and bacteria are directly responsible for most of the offensive gases. Specific groups of bacteria have been identified with the production of oral malodor, in particular, gram- negative, anaerobic bacteria. The unpleasant smell of breath mainly originates from volatile sulfide compounds (VSCs), especially hydrogen sulfide (H2S), methylmercaptan (CH3SH), and dimethylsulfide [(CH3)2S] result from the proteolytic degradation of peptides present in saliva, shed epithelium, food debris and gingival crevicular fluid (GCF). This article reviews the etiology, diagnosis, and treatment of oral malodor and gives a brief description of Halitosis Associated Life-quality Test (HALT) questionnaire, a specific 20-item quality-of-life measure for halitosis.

The proton relaxation rate dispersion of paramagnetic ions in blood samples was studied in the frequency interval from 10 kHz to 10 MHz. With the Field cycling method we applied, the samples were first magnetized by a relatively high magnetic field (0.5 T). By electronic means this field was rapidly (1 ms) reduced to a lower value in the interval 0.1 mT - 0.5 T, where the excited proton spin may relax during a time interval of about 3·T1max. Then the magnetic field is again quickly raised up to the higher level for the detection of the NMR-signal. The relaxation characteristics were analyzed by applying a model with three compartments of water proton-spin exchange. For each compartment we estimated a correlation frequency by fitting the dispersion curves to a sum of Lorentz distributions. We found that low concentrations of paramagnetic ions have a large influence on the relaxation rate dispersion in the low frequency region <10 MHz. This effect is suggested to be used for mapping of inorganic paramagnetic or organic free-radical compounds in medical applications as contrast agents and for tracing cellular activity by subtracting MR images recorded at high (>100 mT) and low (<10 mT) relaxation fields. Such sequences of images could be used to study the oxygen status and metabolism of the brain as well as the generation and distribution of reactive oxygen species (ROS). This technique called “Magnetic resonance Relaxation Dispersion Imaging” (MARDI) would be particularly suitable to analyze various neurological diseases such as stroke, MS, Alzheimer´s disease as well as brain tumor progression. It might also be suitable for imaging of tumour oxygenation and in vivo ROS distributions in radiation therapy, which could be used in dose planning and for analyzing and optimizing the effect of various radiation therapy regimes.

The aim of this study is to estimate strains in the restored macerate edentulous mandible bone by using the ARAMIS three-dimensional image correlation system. The system uses two digital cameras that provide a synchronized stereo view of the specimen and the results show the complete strain field during the tests. The highest strain (5%) was detected within mandible-denture contact, mental foramen (8%) and trigonum retromolar (15%). The strain is the consequence of the complete denture vertical displacement.

Objective: The aim of this study is to evaluate whether the differentiation of BMMSC to osteoblasts seeded in a biocompatible scaffold in vitro, would enhance bone formation in vivo over existing bone.

Background: The use of bone marrow derived mesenchymal stem cells (BMMSC) with appropriate scaffolds in critical size defects and ectopic sites has been proven to be a valuable bone tissue engineering (BTE) technique that could potentially overcome the drawbacks of the current bone graft modalities, but the use of such techniques to grow bone over existing cortical bone has not been investigated yet. Materials and Methods: Autologous rabbit BMMSC grown in Chitosan scaffolds and pretreated with dexamethasone (Dx) were transplanted subperiosteally and bilaterally over the calvarial bone of syngeneic rabbits. Biopsies were analysed using radiographical, histological and histochemical methods for the assessment of bone formation within the scaffolds and its integration to the host calvarial bone.

Results: With Dx stimulation, alkaline phosphatase protein level and activity of BMMSC cultured in vitro increased by three folds and the proliferation rate decreased up 90%. In vivo, all cell seeded implants resulted in the formation of an outer collar of bone integrated with the host cortical, regardless of pre-differentiation.

Conclusion: BMMSC had osteogenic features in vitro and in vivo in conjunction with Chitosan scaffold which can have diverse clinical applications in maxilofacial bone regeneration.