Biomedical Engineering

Pulse sequences which permit imaging and volume‐selective determination of parameters characterizing the frequency dependence of the spin‐lattice relaxation time in the rotating frame, T1ρ are presented. The contrasts are due to slowly moving macromolecules or paramagnetic contrast agents. In vivo test experiments were carried out with tumorous mice treated with a contrast agent. It is shown that the contrast effect is dramatically enhanced in T1ρ dispersion images compared with images weighted by any of the relaxation times. © 1989 Academic Press, Inc.

Background:We compared the effectiveness of stretching and strengthening exercises combined with myofascial releasing and mobilization techniques to a stretching and strengthening only home program in plantar fasciitis (PF) management.Method:The study included 53 feet of 47 patients with plantar fasciitis (35 women / 12 men; mean age 48.9±11.2 years). Pain, disability, and activity restrictions were assessed by Foot Function Index (FFI), and first step pain was graded by visual analog scale (VAS). Ankle range of motion (ROM), gastrocnemius-soleus flexibility, proprioception, dynamic balance, and foot sensation were also considered. The patients were randomly divided into outpatient clinic treatment (Outpatient, n = 27 feet) and home rehabilitation groups (Home, n = 26 feet). Patient education was routine for all at the beginning of the management programs. In the Outpatient group, the foot-ankle-hip exercise program, myofascial releasing, and joint and soft tissue mobilization techn...

We performed intra-articular reconstruction of the anterior cruciate ligament (ACL) with the semitendinosus tendon placed in 2 mm diameter tunnels in 21 skeletally immature rabbits. The operation caused 11% damage to the physis of the femur on the frontal plane and 3% of its cross-sectional area but no alteration of growth or axial deviation of the bone resulted. In the tibia, the operation caused 12% damage to the physis in the frontal plane and 4% of the cross-sectional area. Two tibiae developed valgus deformities and one was shortened. Histological examination showed no areas of epiphysiodesis. There was no abnormality of growth-plate thickness in the two cases of tibia valga. Osseous metaplasia in the grafted tendons did not occur. The results suggest the need for careful evaluation of the percentage of damage to the growth plate before using intra-articular methods for reconstruction of the anterior cruciate ligament in adolescents.

Application of umbilical cord blood (UCB) transplantation in adults as a treatment post‐chemotherapy is hampered due to delayed platelet recovery. A potential solution suggested is the transfusion of ex vivo expanded megakaryocytes (Mks) from hematopoietic stem cells (HSCs). Alternatively, large‐scale production of platelets in vitro has also been attempted with the goal of transfusing them into patients with thrombocytopenia. Glycosaminoglycans (GAGs) have been shown to influence the proliferation and differentiation of HSCs. This study sought to examine the effects of immobilized GAGs on the expansion, apoptosis, and platelet release activity of CD41a+ Mk progenitors in vitro. Freshly isolated HSCs from UCB were cultured in serum‐free media supplemented with thrombopoietin on GAG‐derivatized chitosan membranes for 17 days. Controls consisted of uncoated and chitosan‐coated wells. Wells were demidepopulated at periodic intervals and analyzed by flow cytometry. Heparin and dermatan ...

A bio-scaffold can be broadly termed as a structure used to substitute an organ either permanently or temporarily to restore functionality. The material that can be used varies with the application intended. Tissue engineering is one such application demanding certain requirements to be met before it is applied. One of the applications in tissue engineering is the tissue scaffold, which provides either a permanent or temporary support to the damaged tissues/organ until the functionalities are restored. A biomaterial can exhibit specific interactions with cells that will lead to stereotyped responses. The use of a particular material and morphology depends on various factors such as osteoinduction, osteoconduction, angiogenesis, growth rates of cells and degradation rate of the material in case of temporary scaffolds, etc. The current work reviews the state of art in tissue scaffolds and focuses on permanent scaffold materials and applications with a brief overview of temporary scaff...

Cerebral palsy (CP) is a group of nonprogressive neuro-developmental conditions occurring in early childhood that causes movement disorders and physical disability. Measuring activity levels and gait patterns is an important aspect of CP rehabilitation programs. Traditionally, such programs utilize commercially available laboratory systems, which cannot to be utilized in community living. In this study, a novel, shoe-based, wearable sensor system (pediatric SmartShoe) was tested on 11 healthy children and 10 children with CP to validate its use for monitoring of physical activity and gait. Novel data processing techniques were developed to remove the effect of orthotics on the sensor signals. Machine learning models were developed to automatically classify the activities of daily living. The temporal gait parameters estimated from the SmartShoe data were compared against reference measurements on a GAITRite mat. A leave-one-out cross-validation method indicated a 95.3% average accur...

PurposeThe purpose of this study is to safely acquire the first human head images at 10.5T.MethodsTo ensure safety of subjects, we validated the electromagnetic simulation model of our coil. We obtained quantitative agreement between simulated and experimental and specific absorption rate (SAR). Using the validated coil model, we calculated radiofrequency power levels to safely image human subjects. We conducted all experiments and imaging sessions in a controlled radiofrequency safety lab and the whole‐body 10.5T scanner in the Center for Magnetic Resonance Research.ResultsQuantitative agreement between the simulated and experimental results was obtained including S‐parameters, maps, and SAR. We calculated peak 10 g average SAR using 4 different realistic human body models for a quadrature excitation and demonstrated that the peak 10 g SAR variation between subjects was less than 30%. We calculated safe power limits based on this set and used those limits to acquire T2‐ and ‐weight...

PurposeTo investigate the feasibility of imaging the human torso and to evaluate the performance of several radiofrequency (RF) management strategies at 10.5T.MethodsHealthy volunteers were imaged on a 10.5T whole‐body scanner in multiple target anatomies, including the prostate, hip, kidney, liver, and heart. Phase‐only shimming and spoke pulses were used to demonstrate their performance in managing the inhomogeneity present at 447 MHz. Imaging protocols included both qualitative and quantitative acquisitions to show the feasibility of imaging with different contrasts.ResultsHigh‐quality images were acquired and demonstrated excellent overall contrast and signal‐to‐noise ratio. The experimental results matched well with predictions and suggested good translational capabilities of the RF management strategies previously developed at 7T. Phase‐only shimming provided increased efficiency, but showed pronounced limitations in homogeneity, demonstrating the need for the increased degree...

PurposeDespite the clear synergy between high channel counts in a receive array and magnetic fields ≥ 7 Tesla, to date such systems have been restricted to a maximum of 32 channels. Here, we examine SNR gains at 7 Tesla in unaccelerated and accelerated images with a 64‐receive channel (64Rx) RF coil.MethodsA 64Rx coil was built using circular loops tiled in 2 separable sections of a close‐fitting form; custom designed preamplifier boards were integrated into each coil element. A 16‐channel transmitter arranged in 2 rows along the z‐axis was employed. The performance of the 64Rx array was experimentally compared to that of an industry‐standard 32‐channel receive (32Rx) array for SNR in unaccelerated images and for noise amplification under parallel imaging.ResultsSNR gains were observed in the periphery but not in the center of the brain in unaccelerated imaging compared to the 32Rx coil. With either 1D or 2D undersampling of k‐space, or with slice acceleration together with 1D under...

To validate electromagnetic and thermal simulations with in vivo temperature measurements, and to demonstrate a framework that can be used to predict temperature increase caused by radiofrequency (RF) excitation with dipole transmitter arrays. Dipole arrays were used to deliver RF energy in the back/neck region of the swine using different RF excitation patterns (n = 2-4 per swine) for heating. The temperature in anesthetized swine (n = 3) was measured using fluoroscopic probes (n = 12) and compared against thermal modeling from animal-specific electromagnetic simulations. Simulated temperature curves were in agreement with the measured data. The root mean square error between simulated and measured temperature rise at all locations (at the end of each RF excitation) is calculated as 0.37°C. The mean experimental temperature rise at the maximum temperature rise locations (averaged over all experiments) is calculated as 2.89°C. The root mean square error between simulated and measure...

PurposeIn this work, we investigated the relative effects of static magnetic field exposure (10.5 Tesla [T]) on two physiological parameters; blood pressure (BP) and heart rate (HR).MethodsIn vivo, we recorded both BP and HR in 4 swine (3 female, 1 male) while they were positioned within a 10.5T magnet. All measurements were performed invasively within these anesthetized animals by the placement of pressure catheters into their carotid arteries.ResultsWe measured average increases of 2.0 mm Hg (standard deviation [SD], 6.9) in systolic BP and an increase of 4.5 mm Hg (SD, 13.7) in the diastolic BPs: We also noted an average increase of 1.2 beats per minute (SD, 2.5) in the HRs during such.ConclusionData regarding changes in BP and HR in anesthetized swine attributed to whole‐body 10.5T exposure are reported. Magn Reson Med 79:511–514, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

To explore the potential of performing body imaging at 10.5 Tesla (T) compared with 7.0T through evaluating the transmit/receive performance of similarly configured dipole antenna arrays. Fractionated dipole antenna elements for 10.5T body imaging were designed and evaluated using numerical simulations. Transmit performance of antenna arrays inside the prostate, kidneys and heart were investigated and compared with those at 7.0T using both phase-only radiofrequency (RF) shimming and multi-spoke pulses. Signal-to-noise ratio (SNR) comparisons were also performed. A 10-channel antenna array was constructed to image the abdomen of a swine at 10.5T. Numerical methods were validated with phantom studies at both field strengths. Similar power efficiencies were observed inside target organs with phase-only shimming, but RF nonuniformity was significantly higher at 10.5T. Spokes RF pulses allowed similar transmit performance with accompanying local specific absorption rate increases of 25-9...

Complete rupture of the anterior cruciate ligament (ACL) is a common problem in orthopedics. At present, there are many techniques to reconstruct ligaments, which include the use of autografts, allografts, and, in some cases, artificial ligaments. The latter have not provided good results in the short, medium, and long term. The purpose of present study was to engineer functional biological tissue that could potentially be used to replace the knee ligaments by applying tissue engineering techniques and mechanical stimulation with a bioreactor, promoting cellular differentiation and matrix synthesis. In this preliminary study, the new tissue was characterized with mechanical tests and biological tests (viability and immunochemistry), comparing their behavior with that of the native tissue. Mechanical and biological tests proved that mechanical stimulation administered with a bioreactor maintains the ligament fibroblast phenotype and promotes synthesis of the extracellular matrix.

2008 George Papaioannou / Vasilios.C. Protopappas / Tsopelas Panagiotis / Christos Mitrogiannis / George Nianios / Scott Tashman A NEW METHOD FOR PRESSURE SENSOR EQUILLIBRATION AND CONDITIONING Brazilian Journal of Biomotricity, setembro, año/vol. 2, número 003 ...

The purpose of this study was to identify the effects that X-ray source misalignment has on common measurements made from anterior-poster (AP) and medial-lateral (ML) view foot radiographs. A cadaveric foot model was used to obtain ML radiographs with ±25 degree transverse plane misalignment. From these images the calcaneal pitch angle (CPA) and lateral talometatarsal angle (LTMA) were measured. AP images were captured with up to 30 degree sagittal plane misalignment as well as ±15 degree misalignment in the transverse plane at each sagittal angle. From these images the talonavicular coverage angle (TNCA) and talometatarsal angle (TMA) were measured. On the ML images, the CPA was sensitive to transverse plane misalignment from -10 to -25 degrees and from 15 to 25 degrees (P < .005). The LTMA was a more reliable measurement than the CPA and did not demonstrate sensitivity to transverse plane misalignment. On the AP images, the TNCA and TMA were not sensitive to sagittal plane misa...

ABSTRACTThis study explored three dimensional (3D) talonavicular joint (TNJ) coverage/orientation and bone morphology to reveal parameters that could classify and identify predispositions to cavus and planus feet. 3D models of 65 feet from 40 subjects were generated from computed tomography images classified as pes cavus, neutrally aligned, or asymptomatic/symptomatic pes planus. We calculated the talar and navicular overlap (TNJ coverage). We also measured orientation of the navicular, morphological parameters of the talus and navicular, and angular position of the talar head to body. Pes cavus showed significantly less talonavicular coverage (58 ± 2% talus and 86 ± 2% navicular) compared to asymptomatic pes planus (63 ± 2% and 95 ± 2%) and neutrally aligned feet (98 ± 2% navicular), and significantly more navicular dorsiflexion and adduction relative to the talus (p < 0.0083). The talar head in cavus feet was inverted relative to the body compared to planus feet (p < 0.0083)...

In transplantation surgery, extending the criteria for organ donation to include organs that may have otherwise been previously discarded has provided the impetus to improve organ preservation. The traditional method of cold static storage (CS) has been tried and tested and is suitable for organs meeting standard criteria donation. Ex vivo machine perfusion is, however, associated with evidence suggesting that it may be better than CS alone and may allow for organ donation criteria to be extended. Much of our knowledge of organ preservation is derived from animal studies. We review ex vivo porcine organ perfusion models and discuss the relevance to the field of transplantation surgery. Following a systematic literature search, only articles that reported on experimental studies with focus on any aspect(s) of ex vivo and porcine perfusion of organs yet limited to the context of organ transplantation surgery were included. The database search and inclusion/exclusion criteria identifie...