bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Trunk Muscles in Generating Follower Load in the Lumbar Spine of Neutral Standing Posture
Authors: Kim Kyungsoo , Kim Yoon Hyuk
Published: July 2008

Recently, experimental results have demonstrated that the load carrying capacity of the human spine substantially increases under the follower load condition. Thus, it is essential to prove that a follower load can be generated in vivo by activating the appropriate muscles in order to demonstrate the possibility that the stability of the spinal column could be maintained through a follower load mechanism. The aim of this study was to analyze the coordination of the trunk muscles in order to understand the role of the muscles in generating the follower load. A three-dimensional finite element model of the lumbar spine was developed from T12 to S1 and 117 pairs of trunk muscles (58 pairs of superficial muscles and 59 pairs of deep muscles) were considered. The follower load concept was mathematically represented as an optimization problem. The muscle forces required to generate the follower load were predicted by solving the optimization problem. The corresponding displacements and rotations at all nodes were estimated along with the follower forces, shear forces, and joint moments acting on those nodes. In addition, the muscle forces and the corresponding responses were investigated when the activations of the deep muscles or the superficial muscles were restricted to 75% of the maximum activation, respectively. Significantly larger numbers of deep muscles were involved in the generation of the follower load than the number of superficial muscles, regardless of the restriction on muscle activation. The shear force and the resultant joint moment are more influenced by the change in muscle activation in the superficial muscles. A larger number of deep trunk muscles were activated in order to maintain the spinal posture in the lumbar spine. In addition, the deep muscles have a larger capability to reduce the shear force and the resultant joint moment with respect to the perturbation of the external load or muscle fatigue compared to the superficial muscles.
Friction Behavior of Poly (Vinyl Alcohol) Gel Against Stainless Steel Ball in Different Lubricant Media
Authors: Pan Yu-Song , Xiong Dang-Sheng , Chen Xiao-Lin
Published: July 2008

The effects of different variables on the friction coefficient of poly(vinyl alcohol) (PVA) hydrogel and stainless steel ball counterpart were investigated by a ball-on-plate friction and wear tester. Factors included lubrication condition, sliding speed, diameter of stainless steel ball, and load. It is shown that the free water in PVA hydrogel has a good lubrication on the friction counterpart. The friction coefficients have little difference between dry and lubricated conditions during the initial test stage. With the time prolonged, friction coefficient of PVA hydrogel under dry condition sharply increased within a short time. Friction coefficient decreased with increasing sliding speed and diameter of stainless steel ball. The decrease in the friction coefficient in bovine serum was 55.38% while the sliding speed increased from 45rpmto225rpm. The friction coefficient increased as the load increased, and the effect was more conspicuous at low load region.
An Ultrasound Probe Holder for Image-Guided Surgery
Authors: Yousef Basem Fayez , Patel Rajni V. , Moallem Mehrdad
Published: July 2008

Automating image-guided therapy and registering a medical image to a patient require knowledge of the locations of both the medical image source (e.g., ultrasound) and the surgical tool with respect to a global coordinate system that is known relative to the patient. Also, sturdiness of the medical instrumentations is essential. A novel compact stabilizer-tracker integrated assembly is designed to serve as a holder that can be used to support, manipulate in six degrees-of-freedom, and firmly lock-in-place ultrasound imaging probes and other instruments for use in image-guided surgery as well as to provide the position and orientation of the probe in 3D space with respect to a known reference origin. The stabilizer’s configuration allows a clinician to easily manipulate an ultrasound probe in 3D space, and demonstrate improved sturdiness when locked. A reliable validation technique using forward kinematics was used to evaluate the performance of the holder. Performance tests show that the tracker assembly can acquire the position and orientation of the ultrasound probe with an average displacement accuracy of 0.66mm and roll, pitch, and yaw angular accuracies of 0.24deg, 0.38deg, and 0.19deg, respectively. The improved sturdiness demonstrated by the compact-sized stabilizer and the high accuracy of the tracking mechanism make the integrated holder mechanism well suited for use in image-guided robot-assisted brachytherapy. It is anticipated that this will lead to improvement in accuracy and clinical outcomes for the procedure. The novel tracker can also be used to acquire the positions and orientations of other passive mechanisms of complex designs.
Patient-Specific MRI-Based 3D FSI RV/LV/Patch Models for Pulmonary Valve Replacement Surgery and Patch Optimization
Authors: Tang Dalin , Yang Chun , Geva Tal , del Nido Pedro J.
Published: July 2008

A patient-specific right/left ventricle and patch (RV/LV/patch) combination model with fluid-structure interactions (FSIs) was introduced to evaluate and optimize human pulmonary valve replacement/insertion (PVR) surgical procedure and patch design. Cardiac magnetic resonance (CMR) imaging studies were performed to acquire ventricle geometry, flow velocity, and flow rate for healthy volunteers and patients needing RV remodeling and PVR before and after scheduled surgeries. CMR-based RV/LV/patch FSI models were constructed to perform mechanical analysis and assess RV cardiac functions. Both pre- and postoperation CMR data were used to adjust and validate the model so that predicted RV volumes reached good agreement with CMR measurements (error <3%). Two RV/LV/patch models were made based on preoperation data to evaluate and compare two PVR surgical procedures: (i) conventional patch with little or no scar tissue trimming, and (ii) small patch with aggressive scar trimming and RV volume reduction. Our modeling results indicated that (a) patient-specific CMR-based computational modeling can provide accurate assessment of RV cardiac functions, and (b) PVR with a smaller patch and more aggressive scar removal led to reduced stress/strain conditions in the patch area and may lead to improved recovery of RV functions. More patient studies are needed to validate our findings.
Respiratory System Model for Quasistatic Pulmonary Pressure-Volume (P-V) Curve: Generalized P-V Curve Analyses
Authors: Amini R. , Barnes T. A. , Savran A. , Narusawa U.
Published: July 2008

A normalized P-V curve is proposed for quantitative comparisons of quasistatic P-V curves from different sources, including data from different investigators, airway pressure-volume curves versus transpulmonary pressure-volume curves, normal versus injured respiratory system, and animal tests versus clinical data. Similarities and differences among five different data groups we analyzed are shown to be quantified through the nondimensional pressure range of an individual data set, combined with the magnitudes of two nondimensional parameters of the inflation limb, derived from a respiratory system model previously reported.
The Static Performance Analysis of Foil Journal Bearings Considering Three-Dimensional Shape of the Foil Structure
Authors: Lee Dong-Hyun , Kim Young-Cheol , Kim Kyung-Woong
Published: July 2008

To obtain the foil bearing characteristics, the fluid film pressure must be coupled with the elastic deformation of the foil structure. However, all of the structural models thus far have simplified the foil structure without consideration of its three-dimensional shape. In this study, a finite element foil structural model is proposed that takes into consideration the three-dimensional foil shape. Using the proposed model, the deflections of interconnected bumps are compared to those of separated bumps, and the minimum film thickness determined from the proposed structural models is compared to those of previous models. In addition, the effects of the top foil and bump foil thickness on the foil bearing static performance are evaluated. The results of the study show that the three-dimensional shape of the foil structure should be considered for accurate predictions of foil bearing performances and that too thin top foil or bump foil thickness may lead to a significant decrease in the load capacity. In addition, the foil stiffness variation does not increase the load capacity much under a simple foil structure.
Experimental Research on Tribological Properties of Mn0.78Zn0.22Fe2O4 Magnetic Fluids
Authors: Li-jun Wang , Chu-wen Guo , Yamane Ryuichiro
Published: July 2008

The synthesis and application of nanometer-sized particles have received considerable attention in recent years because of their different physical and chemical properties from those of the bulk materials or individual molecules; however, few experimental investigations on the tribological properties of lubricating oils with and without nanoferromagnetic particles have been performed. This work investigates the tribological properties of Mn0.78Zn0.22Fe2O4 nanoferromagnetic as additive in 46# turbine oil using a four-ball friction and wear tester. It is shown that the 46# turbine oil containing Mn0.78Zn0.22Fe2O4 nanoparticles has much better friction reduction and antiwear abilities than the base oil. The 46# turbine oil doped with 6wt%Mn0.78Zn0.22Fe2O4 nanoparticles show the best tribological properties among the tested oil samples, and PB value is increased by 26%, and the decreasing percentage of wear scar diameter is 25.45% compared to base oil.
Modeling of Asperity Collisions and Their Effects in a Frictionless Sliding Contact of Nominally Flat Metallic Surfaces
Authors: Chang L.
Published: July 2008

The collision process of a pair of asperities on two opposing surfaces is modeled in frictionless sliding motion with an analytically traceable approach. Equations of a sufficiently general representation are derived for the contact force, the load-carrying capacity, and the motion resistance of the asperity collision. A system model of the contact of two nominally flat metallic surfaces is subsequently developed incorporating the effects of asperity microcontact collisions. Results of a general nature are presented of the load capacity and motion resistance of the contact system in sliding motion. The model and the results may provide a first-order approximation of the effects of the asperity collisions in a sliding contact system.
Optimization of Groove Geometry for Thrust Air Bearing to Maximize Bearing Stiffness
Authors: Hashimoto Hiromu , Ochiai Masayuki
Published: July 2008

Hydrodynamic gas film bearings are widely used for very-high-speed, lightly loaded rotating machinery. In the design of hydrodynamic gas film bearings, it is of cardinal importance to enhance the stiffness of gas films to minimize vibration due to external excitations. Among various types of hydrodynamic gas film thrust bearings, grooved bearings have an advantage of high stiffness and load-carrying capacity, but the stiffness of the bearings strongly depends on groove geometry. Therefore, when the groove geometry is suitably designed, it is expected to considerably improve the stability characteristics of the bearings. However, conventional bearing geometries are based on a fixed logarithmic spiral curve, and there is no literature on how to effectively change the groove geometry to drastically improve the bearing characteristics. In this paper, the entirely new optimum design methodology, in which the groove geometry can be flexibly changed by using the spline function, is presented to maximize the stiffness of gas films for grooved thrust bearings. The effectiveness of the methodology is experimentally verified.
Cavitation Erosion Mechanism Based on Analysis of Erosion Particles
Authors: Abouel-Kasem A. , Ahmed S. M.
Published: July 2008

The mechanism of cavitation erosion is investigated in detail through observations of the removed particles from pure aluminum (Al-99.999). The particles removed during the incubation stage have distinctive characteristics compared to those removed in the subsequent stages. These characteristics are distinguished by lamellae structure, foldness, waviness, large size as well as one of the particle surfaces appeared to be part of the original face of the specimen. Therefore, these characteristics can be used as a monitor for early detection of cavitation erosion in closed systems. Systematic observations of disloged particles and eroded surface morphology show that the dominant failure mode in cavitation erosion is fatigue.
Investigation of Tribological Behavior of Al–Si Alloy Against Steel Lubricated With Ionic Liquids of 1-Diethylphosphonyl-n-propyl-3- Alkylimidazolium Tetrafluoroborate
Authors: Mu Zonggang , Wang Xiaoxuan , Zhang Shuxiang , Liang Yongmin , Bao Meng , Liu Weimin
Published: July 2008

A series of room temperature ionic liquids bearing with phosphonyl groups on the imidazolium cations, namely, 1-(3′-O,O-diethylphosphonyl-n-propyl)-3-alkylimidazolium tetrafluoroborate, were prepared and their physical properties were determined. They were also evaluated as promising lubricants for the contacts of aluminum on steel by using a SRV test rig. The tribological test results show that the synthetic ionic liquids exhibit better friction-reducing and antiwear abilities than the unsubstituted ionic liquid of 1-ethyl-3-hexylimidazolium tetrafluoroborate (coded as L206) and phosphazene (X-1P). Both the anions and the side substitutes attached to the imidazolium cations affect the tribological performance of lubricants. The scanning electron microscopy, energy-dispersive x-ray analysis, and x-ray photoelectron spectroscopy analyses of the worn surfaces show that complicated tribochemical reactions are involved in the sliding process. The anion decomposition and chemical adsorption of cation took place on the worn surface of aluminum alloy during the sliding process. As a result of the generation of boundary lubrication films which are composed of metal fluorides, B2O3, BN, nitrogen oxide, and FePO4 help to effectively reduce the friction and wear of the contacts.
Exact Counting of Random Height Features of Product Surfaces
Authors: Mohamed M. A. S.
Published: July 2008

Although many statistical parameters are readily derivable from the autocorrelation function, relevant computations make their acquisition infeasible if required for product surface roughness where such a function can only be expressed in its digital form. Presented is a semianalytical approach that significantly reduces numerical computations conventionally followed to obtain width-type statistics of surface topography from the height autocorrelation function (HACF). The approach is based on fitting the digital form of the HACF to an analytic damped cosine that can then be readily differentiated and integrated. The applicability and accuracy of the proposed approach are illustrated for sampled height data experimentally collected from real product surfaces. Comparison of results using both conventional and suggested approaches shows that analytic fitting of the HACF leads to a rich set of descriptive width-type statistics as accurate as but less time consuming than conventional numerical techniques.
Constrained Tibial Vibration in Mice: A Method for Studying the Effects of Vibrational Loading of Bone
Authors: Christiansen Blaine A. , Bayly Philip V. , Silva Matthew J.
Published: July 2008

Vibrational loading can stimulate the formation of new trabecular bone or maintain bone mass. Studies investigating vibrational loading have often used whole-body vibration (WBV) as their loading method. However, WBV has limitations in small animal studies because transmissibility of vibration is dependent on posture. In this study, we propose constrained tibial vibration (CTV) as an experimental method for vibrational loading of mice under controlled conditions. In CTV, the lower leg of an anesthetized mouse is subjected to vertical vibrational loading while supporting a mass. The setup approximates a one degree-of-freedom vibrational system. Accelerometers were used to measure transmissibility of vibration through the lower leg in CTV at frequencies from 20Hzto150Hz. First, the frequency response of transmissibility was quantified in vivo, and dissections were performed to remove one component of the mouse leg (the knee joint, foot, or soft tissue) to investigate the contribution of each component to the frequency response of the intact leg. Next, a finite element (FE) model of a mouse tibia-fibula was used to estimate the deformation of the bone during CTV. Finally, strain gages were used to determine the dependence of bone strain on loading frequency. The in vivo mouse leg in the CTV system had a resonant frequency of 60Hz for ±0.5G vibration (1.0G peak to peak). Removing the foot caused the natural frequency of the system to shift from 60Hzto70Hz, removing the soft tissue caused no change in natural frequency, and removing the knee changed the natural frequency from 60Hzto90Hz. By using the FE model, maximum tensile and compressive strains during CTV were estimated to be on the cranial-medial and caudolateral surfaces of the tibia, respectively, and the peak transmissibility and peak cortical strain occurred at the same frequency. Strain gage data confirmed the relationship between peak transmissibility and peak bone strain indicated by the FE model, and showed that the maximum cyclic tibial strain during CTV of the intact leg was 330±82με and occurred at 60–70Hz. This study presents a comprehensive mechanical analysis of CTV, a loading method for studying vibrational loading under controlled conditions. This model will be used in future in vivo studies and will potentially become an important tool for understanding the response of bone to vibrational loading.
Pressure Waves as a Noninvasive Tool for Artery Stiffness Estimation
Authors: El-Aklouk E. , Al-Jumaily A. M. , Lowe A.
Published: July 2008

In hypertension and aging, central elastic arteries become stiffer and hence the central pulse pressure is augmented due to the increase in the pulse wave velocity and the early return of reflected waves to the heart from the periphery. Valuable information on arterial properties, such as stiffness, can be obtained from both central (aortic) and peripheral (radial) pressure wave forms. A feasibility study for the noninvasive estimation of arterial stiffness using pressure waves detected by a pneumatic cuff wrapped around the upper arm is presented. The propagation and reflection of arterial pressure waves (generated by the heart) in the central elastic arteries are simulated using a simplified water hammer acoustic model. Furthermore, a lumped parameter model is used to describe the transmission of the pressure waves from the brachial artery to the cuff external wall. By combining the two models, we were able to simulate the pressure contours in the brachial artery and illustrate how these pressures transmit to the cuff’s external wall. The effects of aortic stiffness are investigated by simulating the model at different values of aortic elastic moduli and observing the pressure augmentation and the timing of feature points. This work was done as part of the development of a noninvasive diagnostic device by Pulsecor Ltd. The model results obtained in this work are in agreement with published experimental results and the device output; hence, the model can be used to develop the device’s stiffness estimation algorithm.
Estimation of Cavity Length in EHL Rolling Point Contact
Authors: Stadler K. , Izumi N. , Morita T. , Sugimura J. , Piccigallo B.
Published: July 2008

Reciprocating lubricated contacts sometimes suffer from oil starvation due to cavitation at the reversal of motion. However, the behavior of cavities is not well understood such that starvation can be theoretically predicted. In this study, the length of cavity in a steady state elastohydrodynamic lubricated point contact was calculated. For numerical simulation, a modified Elrod algorithm was used. An equation was obtained for the cavity enclosed in the oil meniscus. The equation was constructed with Moes dimensionless parameters M and L, assumed pressure of cavity, and viscosity pressure index of the lubricant. The dimensionless cavity length (or the ratio of cavity length by Hertzian contact radius) is proportional to the product of M−a and Lb. Careful examination of the equation elucidated that the cavity length is dominated by the viscosity, sum velocity, cavity pressure, and geometry of the contact. Experimental measurements with a ball-on-disk apparatus have shown good agreement. The validity of the equation suggests that the algorithm is applicable for complete transient simulations. In practice, the estimated cavity length can be a parameter for starvation.
Design of a Smart Inhaler System for Improved Aerosol Drug Delivery
Authors: Pausley Matthew , Seelecke Stefan
Published: July 2008

Drug delivery via inhalation of drug aerosols has long been a standard procedure for the treatment of respiratory ailments. A number of researchers have explored the use of inhaled drugs as a novel way to administer new, often aggressive, drugs. However, conventional inhalers release medication uniformly in the mouth inlet. This approach leads to low inhaler efficiency characterized by high deposition in the upper oral airway. Kleinstreuer and Zhang (2003) have shown that a controlled release of drug particles at a specific location in the mouth inlet greatly increases drug efficiency and allows targeting of specific affected sites within the lung. The methodology was further validated experimentally using a fixed exit position nozzle∕inhaler system and model airway∕lung structure. Motivated by these results, this work presents the design and fabrication of a shape memory alloy-enabled (SMA) “smart inhaler system”. Incorporating a flexible nozzle capable of moving the exit position to any desired location, the smart inhaler system will be a robust system capable of treating many patients. The system employs several novel techniques in the area of smart actuator design and implementation. Ref: Kleinstreuer, C., and Zhang, Z. (2003). Targeted drug aerosol deposition analysis for a four-generation lung airway model with hemispherical tumors, ASME Journal of Biomechanical Engineering, 125(2), 197–206.
Heart Murmur Detection∕Classification System Using Cochlea-Like Pre-Processing
Authors: Ahmad W. , Hayee M. I. , Nordehn Glenn , Burns S. , Fitzakerley Janet. L.
Published: July 2008

According to the most recent report of American Heart Association (AHA), heart disease, stroke and other cardiovascular diseases continue to remain not only the no.1 killer of Americans but also a major cause of permanent disability among American workers. Recently, many research efforts have been carried out to apply artificial intelligence (AI) to auscultation based method for rigorous detection/classification of heart murmurs but accuracy rates are not always high. All of the proposed AI techniques rely on converting the heart sound to an electrical signal and processing that signal to optimize the AI for murmur detection and classification. However, all these techniques fail to recognize that the electrical signal coming out of the cochlea is very different than the electrical signal coming out of the microphone or any other electrical sensor which is commonly used for converting heart sound to electrical signal. In this research paper, we want to take a novel approach to pre-process the electrical heart sound signal before it goes to AI for murmur detection/classification by altering the electrical signal in a similar way as is done by the human cochlea before sending the signals to the brain. Our hypothesis is that cochlea like pre-processing will change the spectral contents of the heart sound signal to enhance the murmur information which can then be efficiently detected and classified by AI circuitry. Using this approach, we plan to develop an AI based system for heart murmur classification/ detection with success rate comparable to that of an expert cardiologist.
Retention Of Cardiac Auscultation Skill Requires Paired Visual And Audio Information In New Learners
Authors: Nordehn Glenn , Strunic Spencer , Soldner Tom , Karlisch Nicholas , Kramer Ian , Burns Stanley
Published: July 2008

Introduction: Cardiac auscultation accuracy is poor: 20% to 40%. Audio-only of 500 heart sounds cycles over a short time period significantly improved auscultation scores. Hypothesis: adding visual information to an audio-only format, significantly (p<.05) improves short and long term accuracy. Methods: Pre-test: Twenty-two 1st and 2nd year medical student participants took an audio-only pre-test. Seven students comprising our audio-only training cohort heard audio-only, of 500 heart sound repetitions. 15 students comprising our paired visual with audio cohort heard and simultaneously watched video spectrograms of the heart sounds. Immediately after trainings, both cohorts took audio-only post-tests; the visual with audio cohort also took a visual with audio post-test, a test providing audio with simultaneous video spectrograms. All tests were repeated in six months. Results: All tests given immediately after trainings showed significant improvement with no significant difference between the cohorts. Six months later neither cohorts maintained significant improvement on audio-only post-tests. Six months later the visual with audio cohort maintained significant improvement (p<.05) on the visual with audio post-test. Conclusions: Audio retention of heart sound recognition is not maintained if: trained using audio-only; or, trained using visual with audio. Providing visual with audio in training and testing allows retention of auscultation accuracy. Devices providing visual information during auscultation could prove beneficial.
Real-Time Drug Release Imaging From Nanocomposite Drug and Polymer Coatings
Authors: Dong Jinping , Haugstad Greg , Frethem Chris , Foley John , Hoerr Bob , Matuszewski Mike , Puskas Judit
Published: July 2008

The ElectroNanospray process (Nanocopoeia, Inc) transforms drugs and polymers into many nanoscale material states including powders, liquids, encapsulated particles, and coatings. This allows application of polymers and drugs to the surface of medical devices such as coronary stents in a single-stage process. A model drug delivery system consisting of a polymer matrix (arborescent polyisobutylene-polystyrene, or arbIBS) and either dexamethasone or sirolimus was studied by various characterization techniques. Modification of ElectroNanospray process parameters resulted in surface coatings with rich morphologies that are revealed by SEM, Atomic Force Microscopy (AFM) and Confocal Raman Microscopy were employed to monitor the drug release process in situ, through which the mechanism of the drug-eluting process may be proposed. A Confocal Raman microscope fitted with underwater objective was used to image arbIBS∕drug films incubated in phosphate-buffered saline over 12h and at various film depths. Drug migrated from more concentrated areas into the surrounding polymer and toward the surface, beginning as early as 5min after placing the sample in buffer and continuing throughout the 12h period. High drug levels remained in the more concentrated areas at the end of incubation, suggesting the potential for prolonged release. SEM and AFM images taken from samples post incubation showed the appearance of nanoscale pores ∼100nm in diameter in areas corresponding in size and distribution to the Confocal Raman planar image areas of increased drug concentration. Confocal Raman microscopy offers a powerful new technique for demonstrating real-time drug release from therapeutic medical device coatings.
Development of Nanoporous Ultrathin Membranes For Implantable Drug Delivery
Authors: Nuxoll Eric E. , Hillmyer Marc A. , Siegel Ronald A.
Published: July 2008

For drug release or physiological sensing with advanced functionality, an implanted device must have an interface that permits passage of drugs or analytes while blocking immunoproteins and other physiological fouling agents. To this end, we have developed a composite membrane which integrates the nanoscale size selectivity of block-copolymers with the mechanical strength and order of micromachined silicon. A silicon wafer was coated with low-stress silicon nitride (LSN) and patterned with 20μm squares on the bottom side by photolithography. These squares were etched through the underlying silicon, using the LSN on the top side as an etch-stop. Poly(styrene)-poly(isoprene)-poly(lactide) (PS-PI-PLA) triblock terpolymer was spin-coated onto the top-side LSN surface and annealed under vacuum. The PLA domains self-assembled into cylinders perpendicular to the coating, nearly spanning it. The PLA was etched away, leaving 40nm pores in the polymer film. The device was subjected to hydrofluoric acid to remove the LSN capping the microscale pores and a final, brief oxygen plasma etch removed any PS capping the nanoscale pores. The resulting composite membrane consists of a 80nm thick PS layer with 40nm wide pores overlaying a 100μm thick silicon support with 20μm wide pores. Preliminary mechanical tests have demonstrated the membrane’s robustness. Such membranes should provide immuno-isolation without retarding small molecule transport and should integrate well with the burgeoning number of BioMEMS devices under development.
Methylcellulose∕Agarose Hydrogel System to Release Therapeutic Agents
Authors: Minner Eric J. , Gilbert Ryan J.
Published: July 2008

Our laboratory has previously developed an injectable hydrogel blend consisting of agarose and methylcellulose that solidifies at physiological temperatures. This study examined the feasibility of loading a chemical species into the hydrogel blend for controlled release. Free radical formation and excessive inflammation following initial central nervous system (CNS) trauma contribute to secondary injury. Therefore, the anti-oxidant glutathione and the anti-inflammatory cytokine interleukin-10 (IL-10) were loaded into the hydrogel blend for the purposes of neutralizing free radicals generated and inhibiting excessive inflammation following CNS injury, respectively. Using Ellman’s reagent, glutathione release from the hydrogel was monitored, and data from these experiments reveal that the agarose-methylcellulose hydrogel blend delivers glutathione for up to five days in vitro. Similar experiments were performed on IL-10 release, which was released for up to four days. Recent experiments have focused on implementing the glutathione-containing hydrogel in a neuronal culture model that contains elevated levels of free radical. In addition, other experiments have focused on implementing the IL-10-containing hydrogel in a monocyte culture model and observing the effects of tissue necrosis factor alpha (TNF‐α) production. Based on these preliminary findings, hydrogel blends consisting of agarose and methylcellulose loaded with glutathione and∕or IL-10 could potentially spare uninjured neurons from secondary injury. Future experiments will utilize a rat spinal cord injury model to further evaluate the efficacy of the hydrogel system. In addition to its use as an injury intervention, the hydrogel system also has the potential for use as a coating in implantable devices, especially in the CNS.
Design of a Compliant Endoscopic Suturing Instrument
Authors: Cronin James A. , Frecker Mary I. , Mathew Abraham
Published: July 2008

This paper describes the initial design and optimization of a compliant endoscopic suturing instrument. The emerging field of Natural Orifice Transluminal Endoscopic Surgery (NOTES) requires innovative instruments to meet the size limitations inherent in this type of minimally invasive surgery; using compliant mechanisms is proposed as one method of meeting this requirement. The compliant design was modeled and optimized to maximize the distal opening and provide a puncture force of at least 4.6N, while being small enough to fit within a 3.3mm working channel. The design utilizes contact for stress relief and intertwining parts for added deflection. ANSYS® was used for finite element analysis including contact and nonlinear deformations. A prototype was fabricated from the optimized geometry and experimentally tested. The best geometry is predicted to have a distal opening of 14.6mm at the tips and supply a puncturing force of 4.83N. The force supplied at the tip was measured and was found to exceed the required 4.6N. The prototype successfully passed two complete sutures and qualitative results are provided. The results of the study will lead to further refinements and improvements in future designs.
Liver Tolerance to Repeat 90Y-Microsphere Radioembolization
Authors: McNeillie Patrick , Kennedy Andrew S. , Dezarn William , Sailer Scott L. , England Mary , Overton Caroll
Published: July 2008

Purpose: Liver tolerance to multiple doses of Y90-microspheres is not known. Many patients (pts) are surviving long enough to be considered for a second and third liver treatments with internal radiation. Materials and Methods: The experience of a single center treating liver tumors with resin Y90-microspheres. Pts that received liver radiation prior to or after resin microsphere therapy were studied. Endpoints were toxicity, tumor response, shunting to lung, and effects on liver volume and function. The delivery activity of microspheres selected was not reduced below BSA dose calculation for patients without prior treatment. All patients received bilobar single session delivery. Results: A total of 38 pts; 14 women, 24 men, treated 6∕2003 to 9∕2006, with 33 pts receiving 2 courses and 5 pts with 3 courses of liver radiation. Retreatment with resin microspheres 26 pts, prior external beam radiation in 7 pts, prior glass microspheres in 2 pts, prior systemic radiotherapy in 2 pts, and prior stereotactic liver radiation in 1 pt. Liver function was stable and adequate in all patients after additional liver radiation, and no pts developed radiation-induced liver dysfunction (RILD) or veno-occlusive disease (VOD). The percentage of shunting to the lung decreased with retreatment. Conclusions: Repeated implantation in the liver with Y90-microspheres is safe in patients that have sufficient liver function and reserve based on known and accepted laboratory parameters already used for selection of microsphere therapy. No acute life-threatening, fatal, or late liver damage was observed, RILD or VOD. No specific dose reduction is recommended for retreatment of the liver.
On Formation of Uniform Microspheres for Drug Delivery Using a Perforated Silicon Membrane: A Preliminary Study
Authors: Song K-.Y. , Häfeli U. , Stoeber B. , Chiao M. , Zhang W. J.
Published: July 2008

A novel method to generate uniform biodegradable microspheres for drug delivery applications has been developed. A liquid phase containing the dissolved microsphere matrix material reaches a continuous phase through a silicon membrane with micron-sized perforations, where it forms microdroplets. The solvent diffuses out of the droplets into the continuous phase leading to the formation of solid microspheres. Experiments with poly (lactic-co-glycolic acid) (PLGA) as the matrix material produced microspheres of which 95% had a diameter between 1 and 2μm, a smaller size and a narrower size distribution than those reported elsewhere using glass or ceramic membranes. Such microspheres will be useful for the intravascular application and pharmaceutical drug delivery with a slow release of the drug at narrowly defined rates. Drug desorption and biodegradation rates induce controllable drug release from functionalized biodegradable microspheres. Those rates are directly proportional to microsphere size. One problem in conventional methods is how to achieve a desired average size and a narrow size distribution of the microspheres. Using a perforated silicon membrane, the size of the microdroplets mainly depends on the pore size and the speed of the continuous phase. By controlling these two parameters, it will be possible to fabricate monodisperse microspheres. The MEMS based approach to microsphere fabrication provided in this paper allows a better control over microsphere dimensions and therefore better control over drug delivery than those reported elsewhere.
Biodegradable Magnetic Nanocomposite Spheres Fabrication by O∕O Emulsion∕Solvent Evaporation Technique for Drug Delivery Purposes
Authors: Asmatulu R. , Fakhari A.
Published: July 2008

Drug targeting systems are important research areas for many diseases treatments (e.g., cancer, nerve damage, heart and artery, diabetic, eye and other medical treatments). Currently, magnetic field, electric field, ultrasound, temperature, UV light and∕or mechanical force systems are considered more for research and development. Magnetic targeted drug delivery system is usually preferred because targeted systems improve the therapeutic index of drug molecules by minimizing the toxic side effects on healthy cells and tissues. In this study, magnetic nanoparticles (∼10nm) were prepared by a chemical coprecipitation of ferric and ferrous chloride salts in the presence of a strong base (ammonium hydroxide) and used for a drug delivery purposes. An oil-in-oil emulsion∕solvent evaporation technique was chosen for the synthesis of nanocomposite spheres. Percentages of magnetic nanoparticles (%5, %10, %20 and%30) and poly(D,L-lactide-co-glycolide) were combined together to produce nanocomposite particles with diameters of 500nmto1.2micronmeter. The effect of particle concentrations on nanocomposite particle size and distribution and morphology were investigated by using scanning electron microscopy (SEM) and laser light scattering (LLS). Additionally, external magnetic fields with various magnet distance, magnetic field, pump speed and solid contents were applied to the nanocomposite particles in a liquid media to find out the effect of variables for the targeting of drug carrying nanocomposite spheres.
Neutral pH Ferrofluid Fabrication for Biomedical Applications
Authors: Asmatulu R. , Fakhari A.
Published: July 2008

Ferrofluids are composed of nanoscale magnetic nanoparticles (iron, cobalt, nickel, or their oxides) and strongly polarized in the presence of magnetic field. After coating the surface of these nanoscale particles (∼10nm) by surfactant molecules (e.g., oleic acid, tetramethylammonium hydroxide, citric acid, etc.), they become fully stable and do not aggregate or segregate under the strong magnetic field. Ferrofluids are used for various applications, including medical (cancer detection ∕ curing, pharmaceutical, MRI), ferrofludic seal around the spinning drive shafts, liquid coolant (megaphones and loudspeakers), friction reducer ∕ shock absorber, earthquake, as well as defense, aerospace, grain size measurement and heat transfer. Ferrofluids are produced at extreme high or low pH values in order to prevent agglomeration of the nanoparticles caused by van der Waals and magnetic forces. This limits the application of ferrofluid for various fields because of the oxidation, corrosion as well as harmful effect to body. In this study, magnetite (Fe3O4) nanoparticles (∼10nm) were produced by coprecipitation of iron (II) and iron (III) chloride salts in the presence of ammonium hydroxide, and stabilized using first citric acid at 100°C and a fatty acid at room temperature. Measured pH value of the ferrofluid was 7.0. As is known, magnetite nanoparticles that have excellent magnetic saturation (∼78emu∕g) are desirable for those applications due to the strong ferromagnetic behavior, less sensitivity to oxidation and relatively low toxicity compared to many other magnetic materials (e.g., iron, nickel and cobalt).
Temporal Resolution Phantom: A Device and Method for Measurement of a CT Scanner’s Temporal Resolution
Authors: Slocum Alexander H. , Jones Stephen E. , Gupta Rajiv
Published: July 2008

A calibration phantom that can be used to measure the temporal resolution of a CT scanner was designed utilizing a deterministic design process. The system was first defined in terms of a set of functional requirements based on parameters of the imaging modality. It was necessary to generate multiple time-varying signals visible to the scanner, each with a pre-determined temporal frequency. Roll-off in the scanner’s ability to resolve the modulation of certain signals would be used to determine the scanner’s temporal resolution. Based on size limitations imposed by the scanning environment, the phantom utilizes multiple planetary gear assemblies, driven by a common shaft, to achieve a wide range of rotational velocities. Results obtained with an alpha prototype agreed with the theory. It was determined that further development of the phantom was necessary to increase the sensitivity of the measurement. The latest prototype phantom has been used to measure the temporal resolution of two different scanners and it was shown that temporal resolution of each is different from the gantry rotation time.
An Implantable Port for Office Laparoscopy: The AbView Access Port
Authors: Shah Ajay M. , Ball Nathan , Ewoldt Randy , Ng Shen Kuan , Powers Benjamin , Fuller Arlan , Sieden Michael , Anand Arun , Slocum Alexander
Published: July 2008

Due to the tendency of ovarian cancer to spread in small sections throughout the abdominal cavity, it is presently difficult to detect early stage cancer recurrence following the primary de-bulking of initial tumors. Because metastases may initially be isolated and too small to detect with conventional scanning techniques such as CT scan and MRI, direct laparoscopic examination of the peritoneal cavity is often conducted. At present, this must be performed in a full operating room, and with the patient under full anesthesia; as a result, such examinations are performed infrequently and at high costs. An implantable port has been designed which enables repeated access of a rigid tool such as a laparoscope to the abdominal cavity with only local anesthesia. The port consists of a tube and a suturing flange, inside of which is a tricuspid valve that prevents fluid backflow out of the peritoneal cavity, even at zero backpressure. The port is implanted through the abdominal wall and sutured to the fascia just below the skin at the time of the primary debulking. Then, when examination is necessary, a commercially available trocar can be inserted through the skin and fat under local anesthesia to interface with the port, thereby enabling all functionality of normal laparoscopic procedures with minimal impact to the patient. Thus, this device has the potential to enable rapid monitoring of metastases in an outpatient setting, and may also be used for drug delivery or biopsies.
A Novel Breast Stabilization Device for MRI-Guided Interventions
Authors: Larson Blake T. , Erdman Arthur G.
Published: July 2008

A breast stabilization device or breast cradle has been developed for use in interventional procedures. The device is a three-dimensional collapsible linkage that, when actuated, lightly compresses the breast while pulling it away from the chest wall. The compression provides the pressure needed to hold the breast firm during needle biopsy, ablation, or other procedures while being more comfortable than bilateral compression plates. By collapsing radially in an open configuration, the cradle provides nearly full access to the breast, as compared to the restrictive two-dimensional layout of grid-based bilateral compression plates. By pulling the breast away from the chest wall, the breast cradle may reduce the incidence of lung puncture or other medical errors. Several iterations of the device were developed, including rigid-joint models and a compliant-joint model. The rigid models more precisely show the kinematics of the device, but the manufacturability and assembly of the joints may be tedious in a production environment. Conversely, the compliant model may be more easily mass-produced, although the design would be more complex and costly. To provide a proof-of-concept for the compliant-joint design, a rapid prototyping machine was used to quickly produce several models that could be produced by other means (i.e. vacuum forming or injection molding) in full production. These models will be tested with breast phantoms in a magnetic resonance imaging (MRI) environment to ensure compatibility. Other tests will be performed to ensure patient comfort amongst various breast sizes and shapes.
A Robotic System for Real-Time Tumor Manipulation During Image Guided Breast Biopsy
Authors: Mallapragada Vishnu G. , Sarkar Nilanjan , Podder Tarun K.
Published: July 2008

Breast biopsy guided by imaging techniques is widely used to evaluate suspicious masses within the breast. Current procedure allows the physician to determine location and extent of a tumor in the patient breast before inserting the needle. There are several problems with this procedure: Complex interaction dynamics between needle and breast tissue will likely displace the tumor from its original position necessitating multiple insertions, causing surgeons’ fatigue, patient’s discomfort, and compromising integrity of the tissue specimen. We present a new concept for real-time manipulation of a tumor using a robotic system that monitors the image of the tumor to generate appropriate external force to position the tumor at a desired location. The objective is to demonstrate that it is possible to manipulate a tumor in real-time by applying controlled external force in an automated way such that the tumor does not deviate from the path of the needle. We have demonstrated efficacy of this approach on breast phantoms. The robotic system consists of an ultrasound probe for image acquisition, a guiding mechanism for automatic probe orientation, image processing algorithm for extracting tumor position and PID (proportional-integral-derivative) controlled actuators for tumor manipulation. We have successfully tested this system for accessing mobile lesions during multiple needle insertion trials. This approach has the potential to reduce the number of attempts a surgeon makes to capture the desired tissue specimen, minimize tissue damage, improve speed of biopsy, and reduce patient discomfort.
A Measurement Device for Rotational Stiffness of the Eye
Authors: de Graaf Thijs R. , Schutte Sander , Simonsz Huib J. , Erdman Arthur G. , van der Helm Frans C. T. , Herder Just L.
Published: July 2008

Objective: A measurement of rotational stiffness of the human eye is necessary, without exerting forces to the eye. Background: Strabismus is a disorder in which the visual axes of the eyes are misaligned. In strabismus surgery, the muscles that drive the eye are altered to compensate for the deviating angle of the eye. Unfortunately, between 20% and 50% of these operations need resurgery. A sensitivity analysis has suggested that one cause for an erroneous outcome of surgery is due to interindividual differences in rotational stiffness induced by tissue surrounding the eye. Methods and Results: A measurement device comprising a moment transferring linkage mechanism was developed. A moment is transferred to the eye without imposing a stationary point of rotation. The mechanism is attached to the eye and has three degrees of freedom. The eye is free to rotate under the applied moment. The applied moment and the resulting angle are measured to calculate the rotational stiffness of the eye. Parasitic forces are minimized by keeping friction, inertia and stiffness in the mechanism to a minimum. In addition, the three degrees of freedom of the mechanism are statically balanced. Conclusion: Preliminary tests have shown the feasibility of the measurement in a sterile environment in people that are in horizontal position.