Longitudinal split anterior tibial muscle flap with preserved function

Exposure of the tibia, preferably the upper three-fifths, can be easily covered by splitting the adjacent anterior tibial muscle longitudinally from behind and transferring the medial part of the muscle to cover the medial surface of the tibia. The function of this important muscle is preserved.     

Use of diagnostic ultrasound for assessing muscle size

The typical "gold standard" for assessing muscle size has been magnetic resonance imaging (MRI) and computerized tomography; however, these processes are very expensive and generally require a medical facility. The advent of B-mode diagnostic ultrasound (US) can perhaps offer a quick, cost-effective method to measure muscle size. The purpose of this study was to document the reliability of B-mode US for assessing muscle size in a variety of populations. Thirty-eight postmenopausal women (avg. age = 58.9 +/- 0.7 years) had both their right rectus femoris and biceps brachii imaged, 85 older men and women (avg. age = 65.0 +/- 0.4 yrs) had their right rectus femoris imaged, and 10 young men and women (avg. age = 26.1 +/- 2.4 yrs) had their right rectus femoris imaged by both US and MRI. The location used for imaging on the right rectus femoris was a point 15 cm above to the superior border of the patella following the midline of the anterior surface of the thigh, whereas the biceps brachii was measured at maximal girth following the midline of the anterior surface of the upper arm. All trials utilizing US (Fukuda Denshi, model 4500) and a 5 Mz transducer (FUT-L104) were obtained in duplicate on 2 separate days. The young subjects that also had their rectus femoris measured by MRI were imaged with a Picker 1.5 Tesla (The Edge), which used a fast spin sequence and 192 x 256 resolution to obtain 2 5-mm-thick slices separated by a 1-mm-thick space. All intraclass correlation coefficients for the various groups and muscles measured by US ranged from r = 0.72-0.99, whereas coefficients of variation (CVs) ranged between 3.5% and 6.7%. The intraclass correlation for the MRI images was r = 0.90 and the CV was 5.2%. In conclusion, it appears that diagnostic US can provide a reliable and cost-effective alternative method for assessing muscle.     

Measurement of subcutaneous adipose tissue using ultrasound images.

The objectives of this paper are to explore the potential of the ultrasound technique to quantify subcutaneous adipose tissue, and to explain the differences between skinfolds and ultrasound measurements across a large range of ages and levels of adiposity. The sample consisted of 115 men and 117 women aged 35 to 51 years, 132 girls and 145 boys aged 12 to 20 years. Subcutaneous fat thickness was measured at four sites using skinfolds calipers, and at seven sites using a real-time B-mode ultrasound scanner. Anthropometric measurements were obtained, and percent body fat was estimated using electric impedance. The agreement between skinfolds and ultrasound measurements was calculated for each age and sex group. The agreement between techniques, and the levels of correlation between body composition and fatness measurements were high in the sample of young men. However, the results were less consistent in the other groups. Site specific differences were also noted.     

Measurement of cervical multifidus contraction pattern with ultrasound imaging

Deep muscle training has become the focus of research and exercise for patients with chronic neck pain. The objective of this in vivo study was to establish a non-invasive assessment tool for the activation of deep cervical muscles. The pattern of the change in the thickness of the cervical multifidus is described with a mathematical equation and used to compare the changes among different levels of resistance (0%, 25%, 50%, 75%, and 100%) and at different cervical levels (fourth, fifth, and sixth cervical (C4, C5, and C6) vertebrae). Twenty asymptomatic subjects (five women and 15 men; 24.3 ± 4.7 years old) were recruited for this experiment. Ultrasonography (US) with synchronized force recording was used to measure the thickness of the cervical multifidus during progressive isometric extension against resistance. Linear and quadratic models were used to estimate the patterns of change in the thickness of cervical multifidus in relation to force. Two-way analysis of variance with repeated measurement and post hoc analysis were used to investigate the differences in thickness. The change in thickness and force was better fitted by quadratic model (y = ax² + bx + c) than by the linear model. The thickness at 50% of maximum contraction was significantly increased compared with that at 25% of maximum contraction. This quantitative non-invasive measurement may provide an assessment tool for further investigation for the physiological function of the deep muscles. Further research is required to investigate whether the change of thickness was predominately determined by the recruitment of muscle fibers or the extensibility of non-contractile tissues.     

Dynamics of embryonic pancreas development using real-time imaging

Current knowledge about developmental processes in complex organisms has relied almost exclusively on analyses of fixed specimens. However, organ growth is highly dynamic, and visualization of such dynamic processes, e.g., real-time tracking of cell movement and tissue morphogenesis, is becoming increasingly important. Here, we use live imaging to investigate expansion of the embryonic pancreatic epithelium in mouse. Using time-lapse imaging of tissue explants in culture, fluorescently labeled pancreatic epithelium was found to undergo significant expansion accompanied by branching. Quantification of the real-time imaging data revealed lateral branching as the predominant mode of morphogenesis during epithelial expansion. Live imaging also allowed documentation of dynamic beta-cell formation and migration. During in vitro growth, appearance of newly formed beta-cells was visualized using pancreatic explants from MIP-GFP transgenic animals. Migration and clustering of beta-cells were recorded for the first time using live imaging. Total beta-cell mass and concordant aggregation increased during the time of imaging, demonstrating that cells were clustering to form "pre-islets". Finally, inhibition of Hedgehog signaling in explant cultures led to a dramatic increase in total beta-cell mass, demonstrating application of the system in investigating roles of critical embryonic signaling pathways in pancreas development including beta-cell expansion. Thus, pancreas growth in vitro can be documented by live imaging, allowing visualization of the developing pancreas in real-time.     

pH heterogeneity in tibial anterior muscle during isometric activity studied by (31)P-NMR spectroscopy.

The occurrence of pH heterogeneity in human tibial anterior muscle during sustained isometric exercise is demonstrated by applying (31)P-nuclear magnetic resonance (NMR) spectroscopy in a study of seven healthy subjects. Exercise was performed at 30 and 60% of maximal voluntary contraction (MVC) until fatigue. The NMR spectra, as localized by a surface coil and improved by proton irradiation, were obtained at a high time resolution (16 s). They revealed the simultaneous presence of two pH pools during most experiments. Maximum difference in the two pH levels during exercise was 0.40 +/- 0.07 (30% MVC, n = 7) and 0.41 +/- 0.03 (60% MVC, n = 3). Complementary two-dimensional (31)P spectroscopic imaging experiments in one subject supported the supposition that the distinct pH pools reflect the metabolic status of the main muscle fiber types. The relative size of the P(i) peak in the spectrum attributed to the type II fiber pool increases with decreasing pH levels. This phenomenon is discussed in the context of the size principle stating that the smaller (type I) motor units are recruited first.     

Measurement of fibre pennation using ultrasound in the human quadriceps in vivo.

Real-time ultrasound scanning was used to measure the angles of fibre pennation of vastus lateralis (VL) and vastus intermedius (VI) of the human quadriceps (n = 12) in vivo. The maximum isometric force and cross-sectional area of the quadriceps were also measured. With the knee at right-angles the mean fibre angles for VL and VI respectively were 0.133 (0.021) rad [7.6 degrees (1.2 degrees)] and 0.143 (0.028) rad [8.2 degrees (1.6 degrees)] [mean (SD)], which is within the range of angles measured on cadavers. The mean angle decreased in going from the contracted [VL, 0.244 rad (14 degrees); VI, 0.279 rad (16 degrees)] to the stretched [VL, 0.105 rad (6 degrees); VI, 0.122 rad (7 degrees)] position. There was a significant positive correlation between fibre angle and muscle cross-sectional area but no relationship between fibre angle and force per cross-sectional area. No increase in fibre angle was detected after 3 months strength training. We conclude that ultrasound can be used to measure pennation angles of superficial muscle groups but we could not demonstrate a relationship between pennation and force-generating capacity.     

Enhanced ultrasound strain imaging using chirp-coded pulse excitation

To improve the quality of ultrasound strain imaging, chirp-coded pulse excitation which can enhance echo signal-to-noise ratio (eSNR) was used. The effects of various factors on chirp-coded strain imaging were investigated. Five chirp schemes were designed to investigate the relationship of the range side lobe level (RSLL), main lobe width and energy for strain imaging. We use phase zero method with amplitude modulation correction as strain estimator. The simulation results demonstrate that elastographic signal-to-noise ratio (SNRe) for chirp pulse decreases with the RSLL and the main lobe width, and that there is a tradeoff among choosing a high-energy tapering window function, reducing the RSLL and narrowing the main lobe in designing a chirp scheme for strain imaging. Chirp pulse performs much better than conventional short pulse in low eSNR, great depth or high attenuation conditions due to the increased eSNR with it. However, in high eSNR condition, the increased eSNR with chirp pulse does not improve SNRe, and the performance of chirp pulse mainly depends on the RSLL and main lobe width. Some chirp schemes still achieve higher SNRe than short pulse in high eSNR condition, because these chirp schemes have narrower main lobe than short pulse and have very low RSLL. Chirp pulse has better lesion detectability and axial strain resolution than short pulse especially in low eSNR condition, because chirp pulse can use shorter window length to get the same SNRe that is achieved by short pulse. Within the scope of five window functions (Tukey, Lanczos, Parzen, Dolph–Chebyshev and Kaiser), we tried to find the optimal chirp scheme which is possibly the combination of chirp pulse excitation with 40% tapered Tukey window and matched compression filter. A commercial elastic phantom experiment on a freehand strain imaging system further validates the superior performance of chirp pulse.     

Pulsed magneto-motive ultrasound imaging using ultrasmall magnetic nanoprobes

Nano-sized particles are widely regarded as a tool to study biologic events at the cellular and molecular levels. However, only some imaging modalities can visualize interaction between nanoparticles and living cells. We present a new technique, pulsed magneto-motive ultrasound imaging, which is capable of in vivo imaging of magnetic nanoparticles in real time and at sufficient depth. In pulsed magneto-motive ultrasound imaging, an external high-strength pulsed magnetic field is applied to induce the motion within the magnetically labeled tissue and ultrasound is used to detect the induced internal tissue motion. Our experiments demonstrated a sufficient contrast between normal and iron-laden cells labeled with ultrasmall magnetic nanoparticles. Therefore, pulsed magneto-motive ultrasound imaging could become an imaging tool capable of detecting magnetic nanoparticles and characterizing the cellular and molecular composition of deep-lying structures.     

Contractile function of the anterior tibial muscle of man at different stages of the denervation-reinnervation process

The contractile and electromyographic properties of the tibialis anterior muscle from the affected and normal side have been studied in 27 patients with lumbar radiculopathies. It was found, that at the early stages of denervation-reinnervation process (according B. M. Gecht e.a.) the rise of the strength and rate characteristics twitch contraction are determined. At the late stages this process having electromyographic signs of 'largeness' of the motor units showed the 'smallness' of the same characteristics.     

Measurement of bioreactor perfusion using dynamic contrast agent-enhanced magnetic resonance imaging.

Dynamic magnetic resonance imaging was used to monitor solute diffusion through aggregates of Chinese hamster ovary cells growing on macroporous carriers in a fixed-bed bioreactor. Diffusion-weighted (1)H magnetic resonance imaging (MRI) and scanning electron microscopy demonstrated that cell growth in the bioreactor was heterogeneous, with the highest cell densities being found at the periphery of the carriers. T(1)-weighted magnetic resonance imaging measurements of the inflow of a commonly used magnetic resonance contrast agent, gadolinium-diethylenetriaminopentaacetic acid (Gd-DTPA), showed that migration of the agent through the peripheral cell masses could be explained by diffusion. However, appearance of the contrast agent in the center of the carriers was too fast to be explained by simple diffusion and indicated that these regions were perfused by convective flow. The average diffusivity of Gd-DTPA through the cell mass was found to be (2.4 +/- 0.2) x 10(-10) m(2) sec(-) (mean +/- SEM). This technique will be useful in the characterization and development of high-cell-density bioreactor systems, in which solute transport plays a critical role in cell growth and physiology.     

Measurement of hemodynamics in human carotid artery using ultrasound and computational fluid dynamics.

The objective of the study was to investigate the feasibility of using computational fluid dynamic modeling (CFD) with noninvasive ultrasound measurements to determine time-variant three-dimensional (3D) carotid arterial hemodynamics in humans in vivo. The effects of hyperoxia and hypoxic hypercapnia on carotid artery local hemodynamics were examined by use of this approach. Six normotensive volunteers followed a double-blind randomized crossover design. Blood pressure, heart rate, and carotid blood flow were measured while subjects breathed normal air, a mixture of 5% CO(2) and 15% O(2) (hypoxic hypercapnia), and 100% O(2) (hyperoxia). Carotid artery geometry was reconstructed on the basis of B-mode ultrasound images by using purpose-built image processing software. Time-variant 3D carotid hemodynamics were estimated by using finite volume-based CFD. Systemic blood pressure was not significantly affected by hyperoxia or hypoxic hypercapnia, but heart rate decreased significantly with hyperoxia. There was an increase in diastolic flow velocity in the external carotid artery after hypoxic hypercapnia, but otherwise carotid blood flow velocities did not change significantly. Compared with normal air, hyperoxic conditions were associated with a decrease in the width of the region of flow separation in the external carotid artery. During hyperoxia, there was also an increase in the minimum and a decrease in maximum shear stress in the bifurcation and hence a reduction in cyclic variation in shear stress. Hypoxic hypercapnia was associated with a reduced duration of flow separation in the external carotid artery and an increase in the minimum shear stress without affecting the cyclic variation in shear stress. This study demonstrates the feasibility of using noninvasive ultrasound techniques in conjunction with CFD to describe time-variant 3D hemodynamics in the human carotid arterial bifurcation in vivo.     

Electrical impedance tomography imaging using a priori ultrasound data

Transverse propagation was previously found to occur in a two-dimensional model of cardiac muscle using the PSpice software program for electronic circuit design and analysis. Longitudinal propagation within each chain, and transverse propagation between parallel chains, occurred even when there were no gap-junction (g-j) channels inserted between the simulated myocardial cells either longitudinally or transversely. In those studies, there were pronounced edge (boundary) effects and end-effects even within single chains. Transverse velocity increased with increase in model size. The present study was performed to examine boundary effects on transverse propagation velocity when the length of the chains was held constant at 10 cells and the number of parallel chains was varied from 3 to 5, to 7, to 10, and to 20. The number of g-j channels was either zero, both longitudinally and transversely (0/0), or 100/100. Some experiments were also made at 100/0, 1/1, and 10/10. Transverse velocity and overall velocity (both longitudinal and transverse components) was calculated from the measured total propagation time (TPT), i.e., the elapsed time between when the first action potential (AP) and the last AP crossed the zero potential level. The transverse g-j channels were placed only at the ends of each chain, such that propagation would occur in a zigzag pattern. Electrical stimulation was applied intracellularly between cells A1 and A2. It was found that, with no g-j channels (0/0), overall velocity increased almost linearly when more and more chains were placed in parallel. In contrast, with many g-j channels (100/100), there was a much flatter relationship between overall velocity and number of parallel chains. The difference in velocities with 0/0 channels and 100/100 channels was reduced as the number of chains was increased. In conclusion, edges have important effects on propagation velocity (overall and transverse) in cardiac muscle simulations.     

In-vivo determination of 3D muscle architecture of human muscle using free hand ultrasound

Muscle architecture is an important parameter affecting the muscle function. Most of the previous studies on in-vivo muscle architecture have used in 2D ultrasound. The importance of the third dimension has not been much explored due to lack of appropriate methods. DT-MRI has been used to study muscle architecture in 3D, however, due to long scan times of about 15 min DT-MRI has not been suitable to study active muscle contractions. The purpose of this study was to develop and validate methods to determine in-vivo muscle fascicle orientations in 3D using ultrasound. We have used 2D ultrasound and a 3D position tracker system to find the 3D fascicle orientation in 3D space. 2D orientations were obtained by using automated methods developed in our previous studies and we have extended these in the current study to obtain the 3D muscle fascicle orientation in 3D space. The methods were validated using the physical phantom and we found that the mean error in the measurement was less than 0.5° in each of the three co-ordinate planes. These methods can be achieved with short scan times (less than 2 min for the gastrocnemii) and will thus enable future studies to quantify 3D muscle architecture during sub-maximal voluntary contractions.