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At least 307 records · Page 17Linked to original sources
PubMed2000

Intervertebral disc cell death is dependent on the magnitude and duration of spinal loading.

STUDY DESIGN: An in vivo study of the toxic consequences of static compressive stress on the intervertebral disc. OBJECTIVES: To determine whether disc cell death is correlated with the magnitude and duration of spinal compressive loading. SUMMARY OF BACKGROUND DATA: Static compression in vivo has been demonstrated to induce cell death. Cell death, in turn, has been associated with disc degeneration in humans. There are currently no tolerance criteria for the intervertebral disc that combine both biomechanical and biologic factors, although both have been implicated in cases of accelerated degeneration. METHODS: Mouse tail discs were loaded in vivo with an external compression device. Compressive stress was applied at one of two magnitudes (0.4 and 0.8 MPa) for 7 days, and at one additional magnitude (1.3 MPa) for 1, 3, and 7 days. Midsagittal sections of the discs were stained for apoptosis using the TdT-dUTP terminal nick-end labeling (TUNEL) reaction. Quantal analysis was used to correlate the extent of cell death to the magnitude and duration of loading. RESULTS: The probit transformation of the percentage of dying cells was proportional to the sum of the logarithmic transformations of the compressive stress and the time of loading. CONCLUSIONS: The results of this study demonstrate the feasibility of developing a quantitative correlation between spinal loading and disc degeneration. Such a correlation may be coupled in the future to existing engineering models that predict spinal loading in response to physical exposures and lead to improved definition of the bounds of healthy and unhealthy spinal loading, and ultimately, refined guidelines for low back safety.

Animals↗
PubMed1998

Quantitative analysis of edema in the dorsal nerve roots induced by acute mechanical compression.

STUDY DESIGN: Edema in the dorsal nerve roots caused by acute compression was assessed quantitatively in the lumbar spine of the adult dog. OBJECTIVE: To establish quantitative evaluation of edema in the dorsal nerve roots and to observe changes after acute compression with time. SUMMARY OF BACKGROUND DATA: Mechanical compression induces an increase in microvascular permeability of the endoneurial capillaries and results in intraneural edema. However, there are no quantitative studies on edema in the nerve roots. METHODS: The seventh lumbar nerve root was compressed with a 60-g force clip for 10 minutes. The nerve roots were removed immediately and at 24 hours, 1 week, and 3 weeks after compression. Nerve roots from the control and the sham groups were also obtained. Before removing the nerve roots, Evans blue albumin was injected intravenously. Changes in edema were examined using fluorescence microscopy. Evans blue albumin emits a bright red fluorescence. The relative red fluorescent area was calculated using computer image analysis, and the data were used to indicate the degree of edema. RESULTS: In the compressed segment, edema was most pronounced just after decompression and reduced in nerves removed at 24 hours. In nerves removed at 1 week, edema was pronounced but was reduced at 3 weeks. In the segments closest to the spinal cord, edema was seen after 1 week and was significant after 3 weeks. In the segments closest to the dorsal root ganglion, edema was not detected at any time. CONCLUSION: In the dorsal nerve roots the degree and the area of edema changed with time elapsed after acute compression. The degree of edema 24 hours after decompression was one third the degree immediately after decompression. These results show that edema induced by mechanical compression can recover after decompression.

Animals↗
PubMed1991

The effect of mechanical deformation on the movement of water in foods.

This study has shown the importance of relating NMR spectroscopic information on the water in model food structures to the mechanical properties of those structures. Analysis of the NMR relaxation data can be used to examine the distribution of water domain sizes, and this has been related to the mechanical properties of the samples. A novel NMR probe-head has been designed, which allows both the NMR and the mechanical data to be simultaneously measured during compression of the sample. This probe-head allows compressive stress/strain data to be obtained directly from the NMR sample, allowing changes in the distribution of the water to be directly correlated to changes in mechanical properties.

Chemical Phenomena↗
PubMed1989

Recurrent deep venous thrombosis: limitations of US.

Compression ultrasound (US) has become widely used to diagnose acute deep venous thrombosis (DVT). To determine the appearance of veins with previous DVT, 60 legs (58 patients) in which DVT had been diagnosed 6-31 months earlier (mean, 15.1 months) were reexamined with compression US. At reevaluation there was no indication of acute DVT. Thirty-two extremities had an appearance consistent with clot at the time of this study; 28 demonstrated normal findings. Variables that correlated with findings at follow-up US included age, location of clot, number of previous clots, pain, and augmentation of flow at compression. These preliminary data indicate that compression US may not be reliable as a follow-up study in patients in whom postphlebotic syndrome develops after an acute episode of DVT.

Follow-Up Studies↗
PubMed1997

Clinical and electrophysiologic characteristics of compressed lumbar nerve roots.

STUDY DESIGN: Clinical and electrophysiologic data of compressed nerve roots were evaluated in patients with lumbar disc herniation. OBJECTIVES: To elucidate the characteristics of the nerve root with respect to preoperative neural deficit and to analyze the predictive factors for recovery of leg paralysis after posterior discectomy. SUMMARY OF BACKGROUND DATA: Prolonged paralysis due to disc herniation is reported to be a poor prognostic factor for motor recovery. In addition, an intraoperative somatosensory evoked potential change has been reported to be correlated with clinical outcome. METHODS: Among 64 patients with a lumbar disc herniation, a variety of clinical data, such as age, gender, duration of leg paralysis or leg pain, the angle of the positive straight leg raising test, and time for recovery from paralysis, were investigated. In addition, threshold, amplitude of compound muscle action potentials, and latency for 85 nerve roots were monitored before and after discectomy. Data were analyzed according to the grade of preoperative neural deficits: Grade 1, severe motor and sensory loss; Grade 2, mild motor and sensory loss; Grade 3, sensory loss only; Grade 4, no deficit (leg pain only); and Grade 5, asymptomatic control. RESULTS: The nerve root threshold before discectomy showed an increase in accordance with the severity of neural deficit. Thresholds of Grade 1 and 2 nerve roots were significantly higher than those of normal control subjects. The average amplitudes of compound muscle action potentials before discectomy in Grade 1 and 2 nerve roots were significantly lower than those of asymptomatic control nerve roots. Elongation of latency also showed a correlation with preoperative neurologic abnormality. Patients who complained of leg pain only were significantly younger, and those who showed severe motor disturbance tended to be older and to show a straight leg raising test angle similar to that of control nerve roots. Severe motor weakness for more than 6 months, a negative straight leg raising test, and age were considered to be poor prognostic factors for motor recovery. CONCLUSIONS: Findings of increased threshold, low amplitude of compound muscle action potentials, and elongated latency correlated with degree of motor weakness. Early decompression for compressed nerve root is recommended, especially in older patients with severe motor weakness presenting a negative straight leg raising test.

Action Potentials↗
PubMed1992

An efficient algorithm for MR image reconstruction and compression.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Algorithms↗
PubMed1995

A model for acute, chronic, and delayed graded compression of the dog cauda equina. Neurophysiologic and histologic changes induced by acute, graded compression.

STUDY DESIGN: The results of acute compression on nerve function and morphology were analyzed in a recently developed model for graded cauda equina compression in the dog. OBJECTIVES: The model was developed to better mimic the clinical situation of cauda equina compression in association with spinal canal stenosis. SUMMARY OF BACKGROUND DATA: The compression of the cauda equina has been induced by metal clips, plastic bands, constrictors, and inflatable balloons. No model has used the intact spinal canal and induced compression by increasing the pressure per se in the canal. METHODS: An inflatable balloon with a diameter exceeding the diameter of the spinal canal was placed under the lamina of the L7 vertebra in the dog. The balloon was inflated to various pressures, and muscle action potential area and nerve conduction velocity were monitored during 2 hours of compression and 1.5 hours of recovery. Nerve root specimens were processed for light microscopic examination. RESULTS: There was a progressive reduction of muscle action potential area and nerve conduction velocity that was proportional to the applied pressure. Histologic evaluation revealed no nerve fiber damage but a slight intraneural edema after compression at 200 mg Hg. CONCLUSIONS: The presented model may provide reproducible results regarding neurophysiologic and morphologic effects after acute, graded compression of the dog cauda equina. Two additional conclusions can be made from this study. First, the area measurement of the MAP is probably well suited for recordings and analyses of changes in muscle action potentials. Second, the specific onset rate of this study, in relation to previous studies, indicates that there is a threshold for the compression onset rate for inducing additional nerve injury located in the interval 0.1-0.8 seconds. The results from the present study provides important baseline data for the continued studies on chronic and intermittent compression with the compression model.

Action Potentials↗
PubMed1990

Enhancement and compression of digital chest radiographs.

The application of digital technologies to chest radiography holds the promise of routine application of image processing techniques to effect image enhancement. Because of their inherent spatial resolution, however, digital chest images impose severe constraints on data storage devices. Compression of these images will relax such constraints and facilitate image transmission on a digital network. We evaluated an algorithm for enhancing digital chest images that has allowed significant data compression while improving the diagnostic quality of the image. This algorithm is based on the photographic technique of unsharp masking. Image quality was measured with respect to the task of tumor detection and compression ratios as high as 2:1 were achieved. This compression can be supplemented by irreversible methods.

Algorithms↗
PubMed1976

[The nasopharynx in jaw compression--craniometric and rhinologic data].

113 patients-7 to 29 years old-of the orthodontic department of the School of Dentistry, University of Minnesota, were studied. 51 patients had a high SN-MP angle (a long face) and 62 a low SN-MP angle (a broad face). As compared to the broad-faced group the probands with a long face showed, on the average, a narrower palatal arch, a more posteriorly postitioned hard palate, a smaller nasopharynx (measured in the sagittal plane), and more frequent nasopharyngeal problems. According to our statistical evaluation, a narrower maxillary dental arch and clinical apparent adenoid hypertrophy do not appear to be connected to each other in a cause-and-effect relationship. They rather seem to be two independent symptoms found frequently, though not necessarily in combination with each other, in persons with a long face.

Adolescent↗
PubMed1992

Compression and reconstruction of MRI images using 2D DCT.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be compressed using the discrete cosine transform (DCT). We present here a method of treating the data that combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Fourier Analysis↗
PubMed1987

On the use of statistics for representing the knowledge acquired from experts in a medical consulting system.

For making medical consulting systems, it is important and significant to select and devise the method for representing the knowledge acquired from professional experts. As quantities of data required for consultation are increasing according to the progress of medical science, we have to introduce some new kinds of statistics into a medical consultation system. From another point of view, since the process of diagnosis of experts is considered to be a kind of effective model for compressing (or condensing) data quantitatively and qualitatively, we discuss the use of statistics for representing the knowledge acquired from experts from the standpoint of data compression.

Adult↗
PubMed1998

The function of sensory nerve fibers in lumbar radiculopathy. Use of quantitative sensory testing in the exploration of different populations of nerve fibers and dermatomes.

STUDY DESIGN: The function of sensory nerve fibers in patients with lumbar radiculopathy and in control individuals was evaluated using quantitative sensory testing. OBJECTIVES: To investigate the effect of lumbar nerve root compression on different populations of nerve fibers and to explore the function of sensory nerve fibers in neighboring nerve roots not involved in the mechanical compression. BACKGROUND DATA: Results from experimental and clinical studies indicate that chronic compression of lumbar nerve roots affects the large myelinated nerve fibers. The majority of nerve fibers involved in the sensation of pain, however, are small afferent nerve fibers. It is therefore of interest to study the effect of compression on large and small sensory afferent channels. Several authors have elucidated the biochemical interaction between disc tissue and nerve roots. Chemical substances in the epidural space can reach the nerve fibers in nerve roots at the same or neighboring lumbar segments. In this way, fibers not involved in the mechanical compression may be affected. METHODS: The small nerve fibers were studied using tests for thermal thresholds (thermotest), and the large myelinated fibers were studied by vibrametry. Forty-two patients were investigated in the symptomatic and the asymptomatic leg, and the results were compared with those of 21 healthy individuals. RESULTS: The thresholds of cold, warmth, and vibration were significantly increased in the dermatome of the compressed nerve root, indicating that large and small sensory nerve fibers were affected. Further, the thresholds were significantly increased in the neighboring dermatomes in the symptomatic and the asymptomatic leg. CONCLUSION: Large and small sensory afferent nerve fibers are affected in lumbar radiculopathy. The increase in sensation thresholds in the ipsilateral neighboring dermatome and in the dermatomes in the asymptomatic leg indicates that adjacent nerve roots are involved in the pathophysiology of sciatica in patients with lumbar disc herniation.

Adult↗
PubMed1996

Factors affecting performance of PACS.

We experimentally constructed a personal-computer-based Picture Archiving and Communication System (PACS) for color images of dermatology clinics. This system should especially satisfy such a demand as to be able to retrieve an image within a few seconds from the database residing in a remote server. Our two objectives in the experiment were: To examine how much time was consumed in each part of PACS while it does a series of jobs, from the requesting of an image to its display on the screen of the workstation of the user. The other objective was to see if a personal-computer-based PACS could satisfy our criteria. Total retrieving time, data reading time, data transporting time and image displaying time were measured. Total retrieving time can be divided into three procedures: Data reading time, data transporting time, image displaying time. Data reading time was about 0.6 second for reading an image with the size of 1 mega bytes (MB). Data reading time and the size of data were linearly correlated. Data transporting time was about 11 seconds for transporting an image with the size of 1 MB through EtherTalk, and 66 seconds through LocalTalk. Data transporting time and the size of the data were also linearly correlated. Data reading time and data transporting time was able to be reduced largely by compression technique. However, smaller data give other important effects to the network system besides reducing the time of data reading, data transporting and data displaying. Most Local Area using image Network (LAN) systems, such as EtherTalk, adopt Carrier Sense Multiple Access with Collision Detection (CSMA/CD) for the way of accessing to other computer. In CSMA/CD, transporting performance suddenly declines if the congestion of signal in a network gets beyond a critical level. This situation fatally impairs the performance of a network. We concluded that data compression plays an important role to improve the performances of PACS, especially those of a server and the network system. A personal-computer-based PACS with EtherTalk and an image compression/decompression hardware, e.g., CL550A chip, satisfies our criteria.

Dermatology↗
PubMed1986

Compression of nucleic acid and protein sequence data.

This paper describes the application of text compression methods to machine-readable files of nucleic acid and protein sequence data. Two main methods are used to reduce the storage requirements of such files, these being n-gram coding and run-length coding. A Pascal program combining both of these techniques resulted in a compression figure of 74.6% for the GenBank data-base and a program that used only n-gram coding gave a compression figure of 42.8% for the Protein Identification Resource database.

Algorithms↗
PubMedDate not supplied

Effect of the Harrington compression system on the correction of the rib hump in spinal instrumentation for idiopathic scoliosis.

To analyze the effect of the Harrington compression system on the rib hump in thoracic idiopathic scoliosis, intraoperative measurements were made on 21 cases during correction with the distraction system and after addition of the compression system. The data show that the compression system makes a major contribution to the correction of total rib deformity in over two-thirds of the patients, and the correction of the rib valley is much more significant than correction of the rib hump. Analysis of postoperative spine roentgenograms seems to indicate that the extent of the rib correction does not correlate with spine derotation as measured by the system of Nash and Moe. The improvement in rib correction achieved by addition of the compression system appears to result from changes centered about the costovertebral joints.

Adolescent↗