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At least 559 records · Page 31Linked to original sources
PubMed2005

Engineering craniofacial scaffolds.

OBJECTIVE: To develop an integrated approach for engineering craniofacial scaffolds and to demonstrate that these engineered scaffolds would have mechanical properties in the range of craniofacial tissue and support bone regeneration for craniofacial reconstruction. EXPERIMENTAL VARIABLE: Scaffold architecture designed to achieve desired elasticity and permeability. Scaffold external shape designed to match craniofacial anatomy. OUTCOME MEASURE: Final fabricated biomaterial scaffolds. Compressive mechanical modulus and strength. Bone regeneration as measured by micro-CT scanning, mechanical testing and histology. SETTING: Departments of Biomedical Engineering, Oral/Maxillofacial Surgery, and Oral Medicine, Pathology and Oncology at the University of Michigan. RESULTS: Results showed that the design/fabrication approach could create scaffolds with designed porous architecture to match craniofacial anatomy. These scaffolds could be fabricated from a wide range of biomaterials, including titanium, degradable polymers, and degradable calcium phosphate ceramics. Mechanical tests showed that fabricated scaffolds had compressive modulus ranging 50 to 2900 MPa and compressive strength ranging from 2 to over 56 MPa, within the range of human craniofacial trabecular bone. In vivo testing of designed scaffolds showed that they could support bone regeneration via delivery of BMP-7 transduced human gingival fibroblasts in a mouse model. Designed hydroxyapatite scaffolds with pore diameters ranging from 400 to 1200 microns were implanted in minipig mandibular defects for 6 and 18 weeks. Results showed substantial bone ingrowth (between 40 and 50% at 6 weeks, between 70 and 80% at 18 weeks) for all scaffolds, with no significant difference based on pore diameter. CONCLUSION: Integrated image-based design and solid free-form fabrication can create scaffolds that attain desired elasticity and permeability while fitting any 3D craniofacial defect. The scaffolds could be manufactured from degradable polymers, calcium phosphate ceramics and titanium. The designed scaffolds supported significant bone regeneration for all pore sizes ranging from 300 to 1200 microns. These results suggest that designed scaffolds are clinically applicable for complex craniofacial reconstruction.

Animals↗
PubMed1993

Building a strategic technology management program.

Strategic technology management decisions are one of the best opportunities for healthcare providers to positively meet clinical needs, patient expectations and competitiveness goals. Technology management must not be treated as an event (annual capital budgeting) but as a well-thought-out, long-range business plan. A strategic technology management team should be formed that includes all the key strategic business areas, plus ad hoc members from the clinical and biomedical engineering areas. Current and future needs should be assessed and the performance of the plan monitored. A plan will help achieve buy-in from clinicians and reduce unwarranted expenditures on technology.

Budgets↗
PubMed2006

Current status of medical technology.

BACKGROUND: Medical Technology (MT) provides innovative instrumentation and methods designed for the purpose of improving prevention, diagnostics, therapy and rehabilitation. MT rooting in science, engineering and the biosciences is characterized by its inter- and transdisciplinarity. METHOD: The current status of MT is described emphasizing the five aspects: (1) review of milestones, (2) the impact of MT on the health care system, (3) the economic significance of MT, (4) the financial resources dedicated to research and development in MT, and (5) the challenges for education and training in MT. The material used is a government issued survey on the situation of MT in Germany, data of health care authorities and congress reports from World Conference on Medical Physics and Biomedical Engineering 2005. RESULTS: The following fields of MT have emerged in recent years and will dominate future development: BioMEMOS, imaging technology, minimally invasive surgery, computer assisted diagnosis, therapy and treatment monitoring, e-health/telemedicine/ networking, and medical engineering for regenerative medicine. Development of MT is driven by the following facts, (1) early and individualized diagnosis enables better treatment, (2) MT enhances cost effectiveness in health care, (3) MT is an economic factor based on fast innovation cycles, a roughly 50% export share and a 6% growth rate in turnover during the last 10 years. A downward tendency of the domestic MT market is a challenge for appropriate measures in improving both the economic and the academic infrastructure, in particular by targeted actions to support research and education. CONCLUSION: The impact of MT on prevention, diagnostics, therapy and rehabilitation is significant and still increasing. Due to a wide spreading in all medical areas, the high innovation rate, and the potential to improve health care, MT is considered one of the key technologies even in the future.

Biomedical Research↗
PubMed2005

Understanding the biodegradation of polyurethanes: from classical implants to tissue engineering materials.

After almost half a century of use in the health field, polyurethanes (PUs) remain one of the most popular group of biomaterials applied for medical devices. Their popularity has been sustained as a direct result of their segmented block copolymeric character, which endows them with a wide range of versatility in terms of tailoring their physical properties, blood and tissue compatibility, and more recently their biodegradation character. While they became recognized in the 1970s and 1980s as the blood contacting material of choice in a wide range of cardiovascular devices their application in long-term implants fell under scrutiny with the failure of pacemaker leads and breast implant coatings containing PUs in the late 1980s. During the next decade PUs became extensively researched for their relative sensitivity to biodegradation and the desire to further understand the biological mechanisms for in vivo biodegradation. The advent of molecular biology into mainstream biomedical engineering permitted the probing of molecular pathways leading to the biodegradation of these materials. Knowledge gained throughout the 1990s has not only yielded novel PUs that contribute to the enhancement of biostability for in vivo long-term applications, but has also been translated to form a new class of bioresorbable materials with all the versatility of PUs in terms of physical properties but now with a more integrative nature in terms of biocompatibility. The current review will briefly survey the literature, which initially identified the problem of PU degradation in vivo and the subsequent studies that have led to the field's further understanding of the biological processes mediating the breakdown. An overview of research emerging on PUs sought for use in combination (drug + polymer) products and tissue regeneration applications will then be presented.

Absorbable Implants↗
PubMed2002

Vascular assembly in natural and engineered tissues.

With the advent of molecular embryology and exploitation of genetic models systems, many genes necessary for normal blood vessel formation during early development have been identified. These genes include soluble effectors and their receptors, as well as components of cell-cell junctions and mediators of cell-matrix interactions. In vitro model systems (2-D and 3-D) to study paracrine and autocrine interactions of vascular cells and their progenitors have also been created. These systems are being combined to study the behavior of genetically altered cells to dissect and define the cellular role(s) of specific genes and gene families in directing the migration, proliferation, and differentiation needed for blood vessel assembly. It is clear that a complex spatial and temporal interplay of signals, including both genetic and environmental, modulates the assembly process. The development of real-time imaging and image analysis will enable us to gain further insights into this process. Collaborative efforts among vascular biologists, biomedical engineers, mathematicians, and physicists will allow us to bridge the gap between understanding vessel assembly in vivo and assembling vessels ex vivo.

Adult↗
PubMed2000

The patchwork engine: image segmentation from shape symmetries.

We propose blind segmentation of images into shape-related 'patches' based on pre-calculated local symmetries (Van Tonder, G.J. & Ejima, Y. (1999). (Forthcoming a) Flexible computation of shape symmetries. Submitted for publication) in shape boundary contours. First, lateral weights between all points in the boundary contour map are assigned analogous to Euclidean distance maps in watershed segmentation (Beucher, S. & Lantejoul, C. (1979). Use of watersheds in contour detection. Proceedings of the International Workshop on Image Processing, CCETT, Rennes, France.). Lateral weights are then used to: (1) extract local maxima in symmetries; (2) link maxima within locally enclosed boundary contours; and (3) reconstruct shape contours using symmetry maxima as 'seeds'. The new model overcomes weaknesses of watershed segmentation. The new model closes gaps in relatively more solid image contours, but it is fundamentally different from methods based on contour interpolation (Grossberg, S., Mingolla, E. & Todorovć, D. (1989). A neural network architecture for preattentive vision, IEEE Transactions on Biomedical Engineering 36, 65-84; Heitger, F. & von der Heydt, R. (1993). A computational model of neural contour processing: figure-ground segregation and illusory contours. Proceedings of the Fourth International Conference on Computer Vision, IEEE Computer Society Press, Washington D.C. (pp. 32-40)). Images are segmented into shape-relevant color-by-number-like patches which compare well to related methods (Gauch, J. & Pizer, M. (1993). The intensity axis of symmetry and its application to image segmentation, IEEE Transactions on Pattern Analysis and Machine Intelligence, 15 (8), 753-770; Ilg, W. & Ogniewicz, R. (1995). The application of Voronoi skeletons to perceptual grouping in line images, Proceedings of the 11th International Conference on Pattern Recognition, The Hague, The Netherlands, pp. 382-385; Zhu, S.C. & Yuille, A.L. (1996) FORMS: a flexible object recognition and modeling system, International Journal of Computer Vision, 20 (3), 187-212.). Two primitive operations, comparison and merging of patches, are proposed as drives for exposing more global shape contours from patches. We conclude that symmetry goes beyond abstract shape morphology: it can contribute to figure-ground segmentation in early vision and form part of primitive operations needed to create hypotheses of complex shape.

Animals↗
PubMedDate not supplied

Clinical engineering services at the VA Medical Center, Los Angeles.

A large, modern Medical Center requires clinical engineering services to account for all medical equipment utilized in the treatment of the short-visit clinic patient, as well as the critically ill, who require extensive hospital, surgical or medical health care. The clinics act as multiphasic screening systems, providing simple treatment and referral for more extensive medical treatment. The hospital provides the necessary medical systems to accommodate the extensive daily patient flow. Few of the clinics can provide the facilities or machines to handle the expense of newer diagnostic and therapy requirements. Manpower and funding for maintenance today is concentrated in the fast-growing Radiology, Radiation Therapy/Nuclear Medicine, and Laboratory areas of the Medical Center. These departments require service specialists, and large amounts of dedicated funding to balance and insure reasonable maintenance of the newer, high-technology equipment. Growth of such technology in the hospital must be matched by the growth of service professionals in biomedical engineering departments.

California↗
PubMed2002

Multi-resolution and wavelet representations for identifying signatures of disease.

Identifying physiological and anatomical signatures of disease in signals and images is one of the fundamental challenges in biomedical engineering. The challenge is most apparent given that such signatures must be identified in spite of tremendous inter and intra-subject variability and noise. Crucial for uncovering these signatures has been the development of methods that exploit general statistical properties of natural signals. The signal processing and applied mathematics communities have developed, in recent years, signal representations which take advantage of Gabor-type and wavelet-type functions that localize signal energy in a joint time-frequency and/or space-frequency domain. These techniques can be expressed as multi-resolution transformations, of which perhaps the best known is the wavelet transform. In this paper we review wavelets, and other related multi-resolution transforms, within the context of identifying signatures for disease. These transforms construct a general representation of signals which can be used in detection, diagnosis and treatment monitoring. We present several examples where these transforms are applied to biomedical signal and imaging processing. These include computer-aided diagnosis in mammography, real-time mosaicking of ophthalmic slit-lamp imagery, characterization of heart disease via ultrasound, predicting epileptic seizures and signature analysis of the electroencephalogram, and reconstruction of positron emission tomography data.

Algorithms↗
PubMed2002

Virtual center for renal support: technological approach to patient physiological image.

The patient physiological image (PPI) is a novel concept which manages the knowledge of the virtual center for renal support (VCRS), currently being developed by the Biomedical Engineering Group of the University of Seville. PPI is a virtual "replica" of the patient, built by means of a mathematical model, which represents several physiological subsystems of a renal patient. From a technical point of view, PPI is a component-oriented software module based on cutting-edge modeling and simulation technology. This paper provides a methodological and technological approach to the PPI. Computational architecture of PPI-based VCRS is also described. This is a multi-tier and multi-protocol system. Data are managed by several ORDBMS instances. Communications design is based on the virtual private network (VPN) concept. Renal patients have a minimum reliable access to the VCRS through a public switch telephone network--X.25 gateway. Design complies with the universal access requirement, allowing an efficient and inexpensive connection even in rural environments and reducing computational requirements in the patient's remote access unit. VCRS provides support for renal patients' healthcare, increasing the quality and quantity of monitored biomedical signals, predicting events as hypotension or low dialysis dose, assisting further to avoid them by an online therapy modification and easing diagnostic tasks. An online therapy adjustment experiment simulation is presented. Finally, the presented system serves as a computational aid for research in renal physiology. This is achieved by an open and reusable modeling and simulation architecture which allows the interaction among models and data from different scales and computer platforms, and a faster transference of investigation models toward clinical applications.

Aged↗
PubMed1999

Image-guided surgery: preliminary feasibility studies of frameless stereotactic liver surgery.

BACKGROUND: Liver surgery can be difficult because there are few external landmarks defining hepatic anatomy and because the liver has significant vascularity. Although preoperative tomographic imaging (computed tomography or magnetic resonance imaging) provides essential anatomical information for operative planning, at present it cannot be used actively for precise localization during surgery. Interactive image-guided surgery involves the simultaneous real-time display of intraoperative instrument location on preoperative images (computed or positron-emission tomography or magnetic resonance imaging). Interactive image-guided surgery has been described for tumor localization in the brain (frameless stereotactic surgery) and allows for interactive use of preoperative images during resections or biopsies. HYPOTHESIS: The application of interactive image-guided surgery (IIGS) is feasible for hepatic procedures from a biomedical engineering standpoint. METHODS: We developed an interactive image-guided surgery system for liver surgery and tested a porcine liver model for tracking liver motion during insufflation; liver motion during respiration in open procedures in patients undergoing hepatic resection; and tracking accuracy of general surgical instruments, including a laparoscope and an ultrasound probe. RESULTS: Liver motion due to insufflation can be quantified; average motion was 2.5+/-1.4 mm. Average total liver motion secondary to respiration in patients was 10.8 +/-2.5 mm. Instruments of varying lengths, including a laparoscope, can be tracked to accuracies ranging from 1.4 to 2.1 mm within a 27-m3 (3 X 3 X 3-m) space. CONCLUSION: Interactive image-guided surgery appears to be feasible for open and laparoscopic hepatic procedures and may enhance future operative localization.

Animals↗
PubMed1996

Synthesis of phenylazido-derivatized substances and photochemical surface modification to immobilize functional groups.

Phenylazido-derivatized low-molecular-weight substances and copolymers containing hydrocarbon- or fluorocarbonalkyl group, sulfonato or amino group, and hydroxyl group were prepared. Upon coating and subsequent ultraviolet (UV) light irradiation, covalent fixation of these substances or copolymers took place only at irradiated portions of polymer surfaces, providing a hydrophobic, ionic, or hydrophilic nature. These were verified with electron spectroscopy for chemical analysis (ESCA) spectra and water contact-angle measurement. Endothelial cells adhered on photochemically modified surfaces which have alkyl, sulfonato, or amino groups on their surfaces, whereas little adhesion occurred on a hydroxyl group-bearing hydrogellike surface. When UV light was irradiated through a photomask on the polymer surfaces, patterned and microprocessed surfaces having cell-adhering and nonadhering regions were obtained. The potential application of this photochemical surface processing method in biomedical engineering is discussed.

Adsorption↗
PubMed2005

Novel copolyanhydrides combining strong inherent fluorescence and a wide range of biodegradability: synthesis, characterization and in vitro degradation.

In this work, a novel diacid monomer was synthesized in a very convenient scheme. The monomer is derived from naturally occurring products and emits strong fluorescence when polymerized to polyanhydride. The chemical structure of the monomer dCPS is as follows: HOC(O)ArOC(O)(CH2)2C(O)O--Ar--COOH. Copolyanhydrides composed of dCPS and sebacic acid were further prepared by melt copolycondensation, and characterized by IR, NMR, UV-Vis, DSC and fluorometry. The emission wavelength (lambda(em)) of the copolymers could be tuned by the excitation wavelength (lambda(ex)). Fluorescence intensity increased with the increase of dCPS content. The microspheres fabricated from the copolymer with dCPS content as low as 10% could be clearly visualized with fluorescence microscopy. Either blue or green images of the microspheres could be captured with an excitation of UV and visible light. The degradation rate of the copolyanhydrides decreased as the dCPS fraction increased, and the degradation duration could be modulated from several days to more than three months. In addition, it was found that the copolyanhydrides displayed surface degradation characteristics. In view of the advantages of the novel copolyanhydrides, such as easy preparation, unique inherent luminescent properties, and widely adjustable degradation rate, they might be useful for biomedical engineering.

Decanoic Acids↗