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PubMed2006

Brachial plexus lesions after backpack carriage in young adults.

Carrying a heavy backpack exerts compression on shoulders, with the potential to cause brachial plexopathy. We evaluated the incidence and predisposing factors of compression plexopathy of the shoulder region in 152,095 military conscripts, hypothesizing that a low body mass index and poor physical fitness predispose to the plexus lesion. Reports of conscripts with neural lesions of the upper arm associated with load carriage were reviewed retrospectively for details associated with the condition onset, symptoms, signs, nerve conduction studies, and electromyographic examinations. Height, weight, and physical fitness scores were obtained from their military training data. The incidence of neural compression after shoulder load carriage in Finnish soldiers was 53.7 (95% confidence interval, 39.5-67.8) per 100,000 conscripts per year. The long thoracic nerve was affected in 19, the axillary nerve in 13, the suprascapular nerve in seven, and the musculocutaneous nerve in six patients. Four patients (7%) had hereditary neuropathy with susceptibility to pressure palsies (HNPP). Symptoms were induced by lighter loads in patients with HNPP. Vulnerability to brachial plexopathy was not predictable from body structure or physical fitness level. To prevent these lesions, awareness of the condition and its symptoms should be increased and backpack designs should be improved.

Adolescent↗
PubMed1988

Physiologic variations of the internal jugular vein surface, role of the omohyoid muscle, a preliminary echographic study.

The action of the omohyoid muscle on the hemodynamics of the internal jugular vein is controversial. For some authors, contraction of this muscle, by tightening the cervical fascia, promotes jugular venous return. For others, contraction of this muscle compresses the jugular vein in its cervical path. With this latter point in mind, the hemodynamics of the internal jugular vein have been studied in its cervical path by echography in 10 healthy volunteers. One hundred twenty measurements of the venous surface were made at rest, with the mouth open and during deep inspiration. In the last 2 situations, evidence of a significant increase in the venous surface was found above the omohyoid muscle. These data confirm the role of compression of the vein by the omohyoid muscle, leading to modifications in intracerebral venous hemodynamics, which can be affected in yawning.

Adult↗
PubMed1992

Information compression in dynamic radiological studies.

The large volumes of digital image data from radiological examinations demand further research and practical solutions in image compression before PACS solutions in large radiological departments are plausible. But another type of compression of image information is also possible, which has, in fact, been somewhat utilized already in analog form, but which has far better possibilities in the digital world. The number of essential images in dynamic X-ray, nuclear medicine, examinations etc. can be greatly reduced. These examinations producing image series are reviewed in terms of compression of information. 3-D displays are very useful in slice imaging, because they provide a means to see easier inside the human body than a number of slice images side by side. We also provide a new method, dynamic pulmonary imaging with digital fluoroscopy, as an example of the digital possibilities to compress a number of images into parametric images, numbers, histograms and curves. These processes also have other positive consequences information is transformed into a more easily perceptible form.

Diagnostic Imaging↗
PubMed2003

C5 palsy after decompression surgery for cervical myelopathy: review of the literature.

STUDY DESIGN: A literature review was conducted to integrate and compile available reports on postoperative C5 palsy. OBJECTIVES: To review the clinical features, possible pathogenesis, and procedures for treatment and prevention of postoperative C5 palsy as a complication of surgery for cervical compression myelopathy. SUMMARY OF BACKGROUND DATA: Although postoperative C5 palsy develops in approximately 5% of patients after decompression surgery of the cervical spine, its pathogenesis and the options for prevention and treatment remain unidentified and many controversies exist. METHOD: We reviewed and analyzed papers published from 1986 to 2002 regarding C5 palsy as a postoperative complication. Statistical comparisons were made when appropriate. RESULTS: Postoperative C5 palsy is reported to occur in an average of 4.6% of patients after surgery for cervical compression myelopathy. No significant differences were noted between patients undergoing anterior decompression and fusion and laminoplasty, nor were distinctions apparent between unilateral hinge laminoplasty and French-door laminoplasty, or between cervical spondylotic myelopathy and ossification of the posterior longitudinal ligament. Two theories were put forth to account for the pathogenesis of C5 palsy: nerve root injury and segmental spinal cord disorder. Neither of these hypotheses has been consistently supported and evidence to refute each hypothesis can be found in the literature. Recently, surgeons have advocated foraminotomy combined with laminoplasty to prevent or treat C5 palsy, but further studies into the efficacy of this procedure are needed. Although patients with C5 palsy generally have a good prognosis for neurologic and functional recovery, those with severe paralysis require significantly longer recovery times when compared to more mild cases. CONCLUSION: The incidence of postoperative C5 palsy has been reported at 4.6% after surgery for cervical compression myelopathy and this value has not varied with different surgical procedures or disease etiologies. The pathogenesis of postoperative C5 palsy remains unclear at the present time. Patients with postoperative C5 palsy generally have a good prognosis for functional recovery, but the severely paralyzed cases required significantly longer recovery times than the mild cases.

Cervical Vertebrae↗
PubMed2004

Analysis and design of watermarking algorithms for improved resistance to compression.

We study the performance of robust digital watermarking approaches in the presence of lossy compression by introducing practical analysis methodologies. Correlation expressions between the embedded watermark and the extracted watermark are derived to determine the optimal watermarking domain to maximize data hiding rates for spread spectrum and quantization watermarking. It is determined both theoretically and through simulations that the embedding strategy, in addition to the transform used for lossy compression, dictate the optimal transform for watermarking. Through analytic comparisons, we develop a novel hybrid watermarking algorithm that exploits the best of both approaches for greater resilience to JPEG compression.

Algorithms↗
PubMed2006

Radio-translucent 3-axis mechanical testing rig for the spine in micro-CT.

To date, no apparatus has yet been devised which would allow the study of bone microstructure of the whole vertebrae under mechanical loading. This paper outlines the design and development of a 3-axis radio-translucent mechanical testing rig for spinal research and testing. This rig is to be used in conjunction with a Shimadzu micro-CT scanner. Several tests were conducted to verify the feasibility of the rig design. First, the maximum range of deformation in compression, flexion\extension, and lateral bending that could be exerted on a goat lumbar functional spinal unit was evaluated using the noncontact digital markers method. Stepwise compression loading was also conducted on a single porcine vertebra and the loading data was compared to results obtained from an industrial grade compression testing machine. Finally, micro-CT scans of a porcine vertebra prior to and at a compression failure strain were obtained. The rig was confirmed to be able to exert pure moment loading in the above mentioned modes of deformation and the extent of deformation was comparable to previous documented results. The stepwise compression loading conducted in the rig was also found to effectively approximate a continuous loading of the same specimen in an industrial grade compression testing machine. Finally, resultant micro-CT images of isotropic resolution 32.80 mum of a porcine vertebra loaded in the rig were obtained. For the first time, trabecular microarchitecture detail of a whole vertebra buckling under 12.1% failure compression strain loading was studied using voxel-data visualization software. These initial series of tests verify the feasibility of the rig as an apparatus incorporating spinal testing and imaging.

Animals↗
PubMed1992

JPEG compression for PACS.

In the medical field, especially in diagnostic radiology, there still remains controversy over how and whether or not to compress X-ray images for storage and transmission. The joint Photographic Expert Group (JPEG) standard which has recently been agreed upon is the very attractive technique to archive and to transport images in medical fields. This technique is based on 'lossy' compression of images, which can handle not only X-ray images but also full-colored images, and is suitable for introduction into picture archiving and communicating systems (PACS). The images can be handled after compression as quite small clusters of data. For example, a single 2000 x 2000 x 12 bits chest X-ray image which is an 8 Mbyte image compressed at a 10:1 ratio could retain virtually all the visible quality of the original version, and would take 100 s to transmit at 64 kbits/s using the Integrated Services Digital Network (ISDN, 800 kbytes compressed file, 8 kbytes/s transmission theoretically). An important factor in the design of this technique is that this format relies on no specific hardware or software if using JFIF (JPEG File interchange Format). Soon this algorithm will be able to run on any workstation or on any PC in the world. Highly compressed images may be unsuitable for diagnostic purposes. However, they may be sufficient for reference images which will be needed in clinical fields.

Algorithms↗
PubMed2005

Process analytical technology case study part I: feasibility studies for quantitative near-infrared method development.

This article is the first of a series of articles detailing the development of near-infrared (NIR) methods for solid-dosage form analysis. Experiments were conducted at the Duquesne University Center for Pharmaceutical Technology to qualify the capabilities of instrumentation and sample handling systems, evaluate the potential effect of one source of a process signature on calibration development, and compare the utility of reflection and transmission data collection methods. A database of 572 production-scale sample spectra was used to evaluate the interbatch spectral variability of samples produced under routine manufacturing conditions. A second database of 540 spectra from samples produced under various compression conditions was analyzed to determine the feasibility of pooling spectral data acquired from samples produced at diverse scales. Instrument qualification tests were performed, and appropriate limits for instrument performance were established. To evaluate the repeatability of the sample positioning system, multiple measurements of a single tablet were collected. With the application of appropriate spectral preprocessing techniques, sample repositioning error was found to be insignificant with respect to NIR analyses of product quality attributes. Sample shielding was demonstrated to be unnecessary for transmission analyses. A process signature was identified in the reflection data. Additional tests demonstrated that the process signature was largely orthogonal to spectral variation because of hardness. Principal component analysis of the compression sample set data demonstrated the potential for quantitative model development. For the data sets studied, reflection analysis was demonstrated to be more robust than transmission analysis.

Feasibility Studies↗
PubMed2004

Simultaneous storage of patient information with medical images in the frequency domain.

Digital watermarking is a technique of hiding specific identification data for copyright authentication. Most of the medical images are compressed by joint photographic experts group (JPEG) standard for storage. The watermarking is adapted here for interleaving patient information with medical images during JPEG compression, to reduce storage and transmission overheads. The text data is encrypted before interleaving with images in the frequency domain to ensure greater security. The graphical signals are also interleaved with the image. The result of this work is tabulated for a specific example and also compared with the spatial domain interleaving.

Algorithms↗
PubMed1998

Factors affecting assessment of cerebral autoregulation using the transient hyperaemic response test.

The transient hyperaemic response in the middle cerebral artery blood flow velocity on the release of brief compression of the ipsilateral common carotid artery has been validated as an indicator of cerebral autoregulation. We evaluated, in three stages, the effect of experimental factors such as duration of compression of the common carotid artery and magnitude of the decrease in blood flow velocity during common carotid artery compression on the transient hyperaemic response. In stage 1, 13 healthy volunteers underwent six transient hyperaemic response tests each; two tests each for either 3, 6 or 10 s duration of compression of the common carotid artery. In stage 2, 10 volunteers underwent four transient hyperaemic response tests each; two tests each for either 10 or 15 s duration of compression of the common carotid artery. In stage 3, data from the transient hyperaemic response tests using 10 s compression from the 23 volunteers who participated in stages 1 and 2 were analysed to evaluate the relationship between magnitude of decrease in blood flow velocity at the onset of compression and the transient hyperaemic response. The transient hyperaemic response ratio (blood flow velocity after the release of compression/baseline blood flow velocity) increased significantly when the duration of common carotid artery compression increased from 3 to 6 s, or from 6 to 10 s (stage 1); increase in the duration from 10 to 15 s did not have any significant effect (stage 2). The transient hyperaemic response ratio correlated significantly with the magnitude of decrease in blood flow velocity after compression, up to the values of the compression ratio (percent decrease in blood flow velocity at the onset of compression) of 40% but not more (stage 3). We conclude that experimental factors such as duration of common carotid artery compression and magnitude of the decrease in blood flow velocity during common carotid artery compression can significantly influence the transient hyperaemic response. These factors should be controlled if the transient hyperaemic response test is used for a comparison between repeated measurements. A compression time of 10 s and a compression ratio of 40% or more, allow maximum expression of the hyperaemic response in healthy volunteers.

Adult↗
PubMed1998

Diagnostic informativeness of compressed digital epiluminescence microscopy images of pigmented skin lesions compared with photographs.

Epiluminescence microscopy (ELM) is a useful method for improved diagnostic accuracy in early cutaneous melanoma. Conventional photographs of ELM images are commonly used for clinical research and documentation. Electronic images have advantages compared with photographs and are essential for medical informatics, computerized learning and telemedicine. Compression of electronic images allows a reduction in volume of data, but significant image deterioration may occur at high compression rates. We sought to study the diagnostic informativeness of compressed digital ELM images compared with conventional photographs. Fifty photographs of pigmented skin lesions, including 23 melanomas, were presented to eight dermatologists as photographic slides and as digital images with 30:1 Joint Photographic Experts Group (JPEG) compression. The diagnostic performance of the media and the readers was described in terms of sensitivity, specificity and areas under receiver operating characteristic curves (AUC). Agreement between the readings of the two types of media regarding the presence or absence of ELM criteria was assessed using kappa (kappa) statistics. The mean AUC was 0.81 (95% confidence interval [CI] = 0.73-0.90) for slides and 0.81 (95% CI = 0.72-0.90; P = 0.89) for digital images. Agreement between the readings of the two types of media regarding the presence or absence of ELM criteria ranged from kappa = 0.55 (95% CI = 0.22-0.88) for grey-blue area to kappa = 0.89 (95% CI = 0.74-1.00) for radial streaming. In conclusion, digital ELM images with 30:1 JPEG compression appear to be as informative as photographic slides when used to differentiate between melanoma and non-melanoma.

Area Under Curve↗
PubMed1998

A three-dimensional mathematical model for predicting spinal joint force distribution during manual liftings.

OBJECTIVE: A three-dimensional dynamic mathematical model was developed to discover what loads are imposed on the lumbar structures by performance of asymmetric manual liftings. DESIGN: An external model was used to estimate the intersegmental resultant forces and moments at the L(5)/S(1) joint in this dynamic biomechanical model. Using an optimization algorithm, an internal model then distributed the intersegmental resultants to forces of muscle, disc, facet joints, and ligaments. BACKGROUND: To study the relation between large loads and low-back disorders, many biomechanical models have been developed. Most of the models were two-dimensional models discussed with symmetric activities. Some three-dimensional biomechanical models were static models or only included limited elements of the disc and muscles in the model. METHODS: A healthy young male subject was asked to perform asymmetric lift with bent knees. Dynamic data of body motion and ground reaction forces were monitored, and the EMG of six muscles were recorded simultaneously. A Newtonian equation was used to calculate the joint intersegmental resultant forces and moments. In the internal model, three components of the disc force, eight muscle forces, two ligament forces and two facet joint forces were computed. RESULTS: The correlation between the reaction moments from the upper and lower models of the external part were generally above 0.94, and the root mean square differences were below 19 Nm. In this internal model, the maximal disc compression was close to the data showed on the literature, and the estimation of muscle forces corresponded to the EMG activities. CONCLUSIONS: A three-dimensional biomechanical model has been developed and evaluated to estimate the spinal joint force distribution during asymmetric manual lifting activities.

Journal Article↗
PubMedDate not supplied

The relationship between primary care, income inequality, and mortality in US States, 1980-1995.

OBJECTIVES: This study tests the robustness of the relationships between primary care, income inequality, and population health by (1) assessing the relationship during 4 time periods-1980, 1985, 1990 and 1995; (2) examining the independent effect of components of the primary care physician supply; (3) using 2 different measures of income inequality (Robin Hood index and Gini coefficient); and (4) testing the robustness of the association by using 5-year time-lagged independent variables. DATA SOURCES/STUDY SETTING: Data are derived from the Compressed Mortality Files, the US Department of Commerce and the Census Bureau, the National Center for Health Statistics, the Centers for Disease Control and Prevention, and the American Medical Association Physician Master File. The unit of analysis was the 50 US states over a 15-year period. STUDY DESIGN: Ecological, cross-sectional design for 4 selected years (1980, 1985, 1990, 1995), and incorporating 5-year time-lagged independent variables. The main outcome measure is age-standardized, all-cause mortality per 100,000 population in all 50 US states in all 4 time periods. DATA COLLECTION/EXTRACTION METHODS: The study used secondary data from publicly available data sets. The CDC WONDER/PC software was used to obtain mortality data and directly standardize them for age to the 1980 US population. Data used to calculate the income inequality measure came from the US census population and housing summary tapes for the years 1980 to 1995. Counts of the number of households that fell into each income interval along with the total aggregate income and the median household income were obtained for each state. The Gini coefficient for each state was calculated using software developed for this purpose. RESULTS: In weighted multivariate regressions, both contemporaneous and time-lagged income inequality measures (Gini coefficient, Robin Hood Index) were significantly associated with all-cause mortality (P <.05 for both measures for all time periods). Contemporaneous and time-lagged primary care physician-to-population ratios were significantly associated with lower all-cause mortality (P <.05 for all 4 time periods), whereas specialty care measures were associated with higher mortality (P <.05 for all time periods, except 1990, where P <.1). Among primary care subspecialties, only family medicine was consistently associated with lower mortality (P <.01 for all time periods). CONCLUSIONS: Enhancing primary care, particularly family medicine, even in states with high levels of income inequality, could lead to lower all-cause mortality in those states.

Cross-Sectional Studies↗
PubMed1999

The use of an injectable, biodegradable calcium phosphate bone substitute for the prophylactic augmentation of osteoporotic vertebrae and the management of vertebral compression fractures.

STUDY DESIGN: A biomechanical study comparing two materials for augmentation of osteoporotic vertebral bodies and vertebral bodies after compression fracture. OBJECTIVES: To compare an injected, biodegradable calcium phosphate bone substitute with injected polymethylmethacrylate bone cement for strengthening osteoporotic vertebral bodies and improving the integrity of vertebral compression fractures. SUMMARY OF BACKGROUND DATA: Injection of polymethylmethacrylate bone cement into fractured vertebral bodies has been used clinically. However, there is concern about thermal damage to the neural elements during polymerization of the polymethylmethacrylate bone cement as well as its negative effects on bone remodeling. Biodegradable calcium phosphate bone substitutes have been studied for enhancement of fixation in fractured vertebrae. METHODS: Forty fresh osteoporotic thoracolumbar vertebrae were used for two separate parts of this study: 1) injection into osteoporotic vertebrae: intact control (n = 8), calcium phosphate (n = 8), and polymethylmethacrylate bone cement (n = 8) groups. Each specimen then was loaded in anterior compression until failure; 2) injection into postfractured vertebrae: calcium phosphate (n = 8) and polymethylmethacrylate bone cement (n = 8) groups. Before and after injection, the specimens were radiographed in the lateral projection to determine changes in vertebral body height and then loaded to failure in anterior bending. RESULTS: For intact osteoporotic vertebrae, the average fracture strength was 527 +/- 43 N (stiffness, 84 +/- 11 N/mm), 1063 +/- 127 N (stiffness, 157 +/- 21 N/mm) for the group injected with calcium phosphate, and 1036 +/- 100 N (stiffness, 156 +/- 8 N/mm) for the group injected with polymethylmethacrylate bone cement. The fracture strength and stiffness in the calcium phosphate bone substitute group and those in the polymethylmethacrylate bone cement group were similar and significantly stronger than those in intact control group (P < 0.05). For the compression fracture study, anterior vertebral height was increased 58.5 +/- 4.6% in the group injected with calcium phosphate and 58.0 +/- 6.5% in the group injected with polymethylmethacrylate bone cement as compared with preinjection fracture heights. No significant difference between the two groups was found in anterior vertebral height, fracture strength, or stiffness. CONCLUSION: This study demonstrated that the injection of a biodegradable calcium phosphate bone substitute to strengthen osteoporotic vertebral bodies or improve vertebral compression fractures might provide an alternative to the use of polymethylmethacrylate bone cement.

Absorbable Implants↗
PubMed2003

Improved venous return by elliptical, sequential and seamless air-cell compression.

AIM: The risk of deep vein thrombosis (DVT) in the peri-operative period is significant, but can be reduced with the use of mechanical intermittent pneumatic compression (IPC). These devices have reached widespread use in hospitals and have been found to be effective prophylactic measures against DVT. This study evaluates the latest design features of one particular IPC device in comparison to current models. METHODS: Duplex ultrasound scanning was performed on 40 lower extremities of 20 healthy volunteers before and during the application of the IPC device (VenaFlow System, Aircas, NJ, USA. Two hemodynamic parameters were measured, acceleration time from spontaneous baseline venous flow and peak vein velocity. All measurements were obtained by scanning proximal to the saphenofemoral junction in the common femoral vein in both extremities for each subject. Data were obtained from 3 compression cycles and averaged for each extremity. Results were compared with a recent prospective study form our center using a slow-filling and a rapid-filling sequential IPC devices. RESULTS: The medians for spontaneous average peak velocities at rest of the right and left lower extremities were 26 cm/s and 24.1 cm/s. The median augmented peak velocities during the compression cycle of the device in the right and left side were 79.6 cm/s and 79.0 cm/s. This represented a 306.2% increase in average peak velocity on the right side and a 327.8% increase on the left side. The median acceleration time was 305 ms +/- 40 in the left and 310 ms +/- 50 in the right limb. There was no statistically significant difference in the spontaneous and augmented velocities between the right and left lower extremities in each subject. In comparison to existing slow- and rapid-filling IPC devices the VenaFlow System had superior peak velocities and shorter acceleration times. CONCLUSION: The use of elliptical, sequential and rapid-filling compression of the leg with overlapping air-cells produces significant hemodynamic changes in the common femoral vein, which are superior to other sequential slow- or rapid-filling IPC devices. Randomized studies should be performed to determine the efficacy of this new device in DVT prevention.

Adult↗
PubMed1994

Modeling the additivity of nonsimultaneous masking.

Thresholds were measured for detecting a brief 6-kHz sinusoidal signal preceded by a broadband noise masker (forward masking), followed by the masker (backward masking), or both preceded by and followed by the masker (combined masking). The masker-signal interval was systematically varied. Consistent with the literature, thresholds in the combined-masking condition were higher than would be predicted by an energy-sum of the effects of the individual forward and backward maskers. This is often referred to as 'excess' masking. The data were modeled by subjecting the amplitude of the stimuli to a power-law nonlinearity followed by a sliding temporal integrator ('window'). It was assumed that threshold corresponds to a fixed signal-to-noise ratio at the output of the window. The best fits to the data were obtained using a power less than unity (0.5 to 0.7), i.e. by a compressive nonlinearity. Generally good fits to the data were achieved, indicating that the model is able to account for the decay of forward and backward masking as well as the effects of combining pairs of maskers (excess masking). The temporal windows derived from the data are also able to predict thresholds in decrement and increment detection tasks, and to account for the longer-term effects of masker duration in forward masking.

Acoustic Stimulation↗
PubMed2005

Comparing different estimates of cochlear compression in listeners with normal and impaired hearing.

A loss of cochlear compression may underlie many of the difficulties experienced by hearing-impaired listeners. Two behavioral forward-masking paradigms that have been used to estimate the magnitude of cochlear compression are growth of masking (GOM) and temporal masking (TM). The aim of this study was to determine whether these two measures produce within-subjects results that are consistent across a range of signal frequencies and, if so, to compare them in terms of reliability or efficiency. GOM and TM functions were measured in a group of five normal-hearing and five hearing-impaired listeners at signal frequencies of 1000, 2000, and 4000 Hz. Compression values were derived from the masking data and confidence intervals were constructed around these estimates. Both measures produced comparable estimates of compression, but both measures have distinct advantages and disadvantages, so that the more appropriate measure depends on factors such as the frequency region of interest and the degree of hearing loss. Because of the long testing times needed, neither measure is suitable for clinical use in its current form.

Adolescent↗
PubMed1985

Spinal cord contusion injury: experimental dissociation of hemorrhagic necrosis and subacute loss of axonal conduction.

Previously reported experimental models for spinal cord contusion injury do not allow the independent control of compression and contact velocity required for interpretation of experimental data relating kinematics of vertebral injury to spinal cord injury. Therefore, controlled dynamic compression of the spinal cord was used to study compression and contact velocity as independent variables. Cord conduction was assessed using the latency of somatosensory evoked potentials in response to hindlimb stimulation. The latency increase at 4 hours after contusion differed significantly between control and 50% compression results, and between 25% and 50% compression results. A small nonsignificant increase in latency was observed with increase in contact velocity. The extent of hemorrhagic necrosis correlated with contact velocity rather than with the amount of compression. This study demonstrates, for the first time, a dissociation between hemorrhagic necrosis and loss of neuronal conduction in the subacute phase. Although long-term effects of hemorrhagic necrosis on cord structure and conduction remain to be evaluated, the data suggest that delayed loss of neuronal conduction seen clinically may result from moderate levels of cord compression at high contact velocity. Such an injury is not reproducible by weight-drop techniques for cord injury.

Animals↗