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At least 559 records · Page 31Linked to original sources

PubMed2001

Effects of the glenoid labrum and glenohumeral abduction on stability of the shoulder joint through concavity-compression : an in vitro study.

BACKGROUND: Although the glenohumeral joint is the most mobile articulation of the human body, it is known to exhibit ball-and-socket kinematics. Compression into the glenoid labral concavity keeps the humeral head centered. The purpose of the present study was to determine the effects of joint position on glenohumeral stability through concavity-compression. METHODS: Ten cadaveric shoulders were tested. The glenoid was mounted horizontally onto a six-component load-cell while the humerus was clamped to a vertically unconstrained slide. An x-y stage translated the load-cell with the glenoid underneath the humeral head in eight different directions. Compressive loads of 20, 40, and 60 N were applied. The tests were repeated in 0 degrees, 30 degrees, 60 degrees, and 90 degrees of glenohumeral abduction with and without the labrum. Relative translations between the glenoid and the humeral head and the forces resisting translation were recorded. Then the stability ratio, defined as the peak translational force divided by the applied compressive force, was calculated. RESULTS: The average stability ratio was higher in the hanging-arm position than it was in glenohumeral abduction. The highest stability ratio was detected in the inferior direction (59.8% 7.7%) when the labrum was intact and in the superior direction (53.3% 7.9%) when the labrum had been resected. Under both conditions, the anterior direction was associated with the lowest stability ratio (32.0% 4.4% with the labrum and 30.4% 4.1% without the labrum). Resection of the glenoid labrum resulted in an average decrease in the stability ratio of 9.6% 1.7%. With increasing compressive load, the average stability ratio slightly decreased. CONCLUSIONS: Glenohumeral stability through concavity-compression was greater in the hanging-arm position than it was in glenohumeral abduction. The average contribution of the labrum to glenohumeral stability through concavity-compression was approximately 10%, about one-half of the value previously reported. With the labrum intact, the glenohumeral joint was most stable in the inferior direction. Without the labrum, it was most stable in the superior direction. Under both conditions, it was least stable in the anterior direction. Glenohumeral joint stability through concavity-compression decreases with higher compressive loads.

Aged↗

PubMed1996

Detection of subtle interstitial abnormalities of the lungs on digitized chest radiographs: acceptable data compression ratios.

OBJECTIVE: To determine acceptable compression ratios for digital radiography, we evaluated the effect of data compression on the detection of subtle interstitial lung abnormalities using digitized chest radiographs. MATERIALS AND METHODS: Screen-film chest radiographs of 38 patients with subtle interstitial lung abnormalities and 40 patients with normal lung parenchyma were digitized (spatial resolution, 0.175 mm; 2000 x 2000 pixels; 10 bits per pixel) and compressed with the discrete cosine transform method at ratios of 10:1, 20:1, and 30:1. Five chest radiologists and five radiology residents examined the uncompressed and compressed digital images and rates the presence of interstitial lung abnormalities with a five-level scale of confidence. Results were analyzed by receiver operating characteristic methods. RESULTS: Overall, the interpretation of images with a compression ratio of 30:1 was significantly less accurate than that of uncompressed images (p < .05). For the five chest radiologists, interpretation of images with a compression ratio of 20:1 or 30:1 was significantly less accurate than that of uncompressed images (p < .05). However, for the five residents, no significant difference between interpretations of compressed and uncompressed images was noted (p > or = .05). CONCLUSION: These results suggest that a 10:1 data compression ratio does not influence the detection of subtle interstitial lung abnormalities. However, information that is lost with a 20:1 data compression ratio might be essential for interpretation by experienced chest radiologists.

Adult↗

PubMed1999

Sonographically guided compression repair of pseudoaneurysms: further experience from a single institution.

OBJECTIVE: Our purpose was to perform a comprehensive review of our experience with compression of postcatheterization groin pseudoaneurysms. MATERIALS AND METHODS: Two hundred eighty-one patients underwent 306 sonographically guided compression procedures on 297 groin pseudoaneurysms after femoral artery catheterization. The medical records, cardiac catheterization reports, and sonographic images were reviewed to determine patient demographics, type of catheterization procedure performed, sheath size, access site, interval from sheath removal to compression, anticoagulation status, pseudoaneurysm dimensions, complications, and follow-up information. Statistical analysis was performed using Pearson's chi-square and Kendall tau tests. RESULTS: The success rate for the initial compression attempt was 72.1%. Of the 83 failed compression attempts, 12 patients underwent a second attempt, of which seven attempts were successful. Therefore, counting both first and second attempts, the success rate was 74.4%. A strong negative correlation existed between anticoagulation status and success, with a 70% failure rate in patients with anticoagulated blood. Smaller pseudoaneurysm size was strongly correlated with success. Of the 83 failed cases, 49 ultimately underwent surgical repair. Eleven complications (3.6%) occurred, including three patients with rupture during compression. No deaths occurred as a result of compression repair. CONCLUSION: We conclude that sonographically guided pseudoaneurysm compression repair is an effective alternative to surgical repair, though nearly one third of compression attempts will fail and most of those patients will ultimately require surgery. The procedure is less effective when the patient's blood is anticoagulated and when the pseudoaneurysm is large. The procedure carries an overall complication rate of 3.6% and a risk for rupture of 1%.

Aged↗

PubMed2004

Decreased venous contamination on 3D gadolinium-enhanced bolus chase peripheral mr angiography using thigh compression.

OBJECTIVE: We evaluated the potential for improving bolus chase peripheral MR angiography in patients with fast arterial flow using thigh compression to prevent venous contamination. SUBJECTS AND METHODS: We performed bolus chase peripheral MR angiography in 32 consecutive patients in whom the travel time for a contrast agent to reach the popliteal artery trifurcation was less than 25 sec. Thigh compression was applied by a tourniquet (n = 13) or blood pressure cuff inflated to 60 mm Hg (n = 19). We compared the results with those of 36 consecutive patients who underwent angiography without thigh compression. The effect of thigh compression on arterial flow and tissue enhancement was assessed in patients with symmetric travel time in both legs by applying compression to one leg during the time-resolved 2D-projection MR angiography with 6 mL of gadolinium. On 3D bolus chase MR angiography, thigh compression was applied bilaterally. Venous contamination on the 3D images of the calf was graded as 0, none; 1, trace; 2, mild; 3, moderate; and 4, severe. Signal-to-noise ratio was measured in the popliteal artery. RESULTS: Thigh compression slowed the arterial travel time by a mean +/- SD of 4.7 +/- 2 sec (p < 0.001) with a blood pressure cuff and 3.1 +/- 1 sec (p < 0.001) with a tourniquet. Blood pressure cuffs reduced the score of venous contamination on the calf station from 1.9 to 0.4 (p < 0.05) for intermediate flow (contrast travel time, 20-25 sec) and from 2.5 to 0.9 (p < 0.05) for fast flow (< 20 sec). Thigh compression increased the popliteal artery signal-to-noise ratio (81 vs 52, p < 0.001). CONCLUSION: Thigh compression with blood pressure cuffs inflated to 60 mm Hg slows down arterial flow, increases arterial signal-to-noise ratio, and reduces venous contamination on 3D gadolinium-enhanced bolus chase peripheral MR angiography.

Aged↗

PubMed1993

Skinfold compressibility in Japanese university students.

It is well known that caliper readings decline after the initial application of the caliper to the skinfold (dynamic compressibility). In addition to this compressibility, there is also a variability of skinfold compressibility at different body sites (static compressibility). To investigate this static variability, a comparison was made between skinfold thickness obtained from using caliper and thickness derived from an ultrasound image (B scan-mode) at sixteen skinfold sites of 96 non-athletic students in good health (45 men and 41 women). The skinfold compressibility is defined as: (uncompressed value-compressed value) x 100/uncompressed value. The patterns created by the plots of skinfold compressibility across the sixteen body sites were similar for both sexes although the inter-site variability is quite large (significant at 0.01 level on ANOVA). Women tend to have greater skinfold compression in the trunk area and less in the limbs as compared with men. This sex difference may be caused by the sex differences of skin thickness and skin tension (subcutaneous space pressure). The marked inter-site variability in skinfold compressibility suggests the need for caution in estimates of fat mass using skinfold calipers.

Adolescent↗

PubMed1986

A randomized controlled trial of variceal compression as an adjunct to endoscopic variceal sclerosis.

Endoscopic variceal sclerosis is effective at eradicating oesophageal varices and prolonging survival, but early rebleeding before varices have been obliterated remains a problem. A randomized controlled trial was therefore conducted to determine whether more rapid variceal obliteration and hence a lower morbidity and mortality in the first month could be achieved by compressing the varices after the first injection of sclerosant. Forty patients bleeding from previously untreated varices were studied. There was no demonstrable benefit from post-sclerosis variceal compression in terms of early death from rebleeding (compression, 3 of 19; no compression, 3 of 21 in the first month), total number of patients rebleeding (compression, 5 of 19; no compression, 6 of 21 in the first month), or speed of variceal obliteration (percentage of variceal columns obliterated at 1 month: compression, 13%; no compression, 26%). This study shows that post-sclerosis variceal compression by means of the Williams overtube and Sengstaken tamponade does not improve the efficacy of endoscopic variceal sclerosis.

Clinical Trials as Topic↗

PubMed1990

Autonomic and histopathological effects of percutaneous trigeminal ganglion compression in the rabbit.

The histopathological and autonomic effects of percutaneous trigeminal ganglion compression for trigeminal neuralgia were studied in New Zealand White rabbits. Drops in mean arterial blood pressure of 38% and in heart rate of 30% were observed during compression (p less than 0.0001). Corneal reflex, pinprick sensation, and mastication strength were intact in 13 of 14 rabbits after compression. These findings resembled the effects of percutaneous compression in humans and suggested that the New Zealand White rabbit is a useful model for the study of percutaneous compression. Trigeminal sensory roots and ganglia from 14 rabbits killed at intervals from 1 to 84 days after percutaneous compression were sectioned and stained using immunoperoxidase for neurofilaments, hematoxylin and eosin, luxol fast blue, and cresyl echt violet. Focal axonal damage and demyelination were present 7 days after compression. No difference could be detected in the perikaryonal distribution of neurofilaments between compressed and control trigeminal ganglia. Focal demyelination and Schwann cell proliferation preceding remyelination were present in the trigeminal sensory root at 84 days. Differential injury of axons compared to trigeminal ganglion cell bodies suggests that axonal regeneration is possible and may contribute to the recovery of motor and sensory function in patients after percutaneous compression.

Animals↗

PubMed2001

Systematic reviews of wound care management: (5) beds; (6) compression; (7) laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy.

BACKGROUND: Chronic wounds such as leg ulcers, diabetic foot ulcers and pressure sores are common in both acute and community healthcare settings. The prevention and treatment of these wounds involves many strategies: pressure-relieving beds, mattresses and cushions are universally used as measures for the prevention and treatment of pressure sores; compression therapy in a variety of forms is widely used for venous leg ulcer prevention and treatment; and a whole range of therapies involving laser, ultrasound and electricity is also applied to chronic wounds. This report covers the final three reviews from a series of seven. AIMS: To assess the clinical effectiveness and cost- effectiveness of: (1) pressure-relieving beds, mattresses and cushions for pressure sore prevention and treatment; (2) compression therapy for the prevention and treatment of leg ulcers; (3) low-level laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy for the treatment of chronic wounds. METHODS - DATA SOURCES: Nineteen electronic databases, including MEDLINE, CINAHL, EMBASE and the Cochrane Controlled Trials Register (CENTRAL), were searched. Relevant journals, conference proceedings and bibliographies of retrieved papers were handsearched. An expert panel was also consulted. METHODS - STUDY SELECTION: Randomised controlled trials (RCTs) which evaluated these interventions were eligible for inclusion in this review if they used objective measures of outcome such as wound incidence or healing rates. RESULTS - BEDS, MATTRESSES AND CUSHIONS FOR PRESSURE SORE PREVENTION AND TREATMENT: A total of 45 RCTs were identified, of which 40 compared different mattresses, mattress overlays and beds. Only two trials evaluated cushions, one evaluated the use of sheepskins, and two looked at turning beds/kinetic therapy. RESULTS - COMPRESSION FOR LEG ULCERS: A total of 24 trials reporting 26 comparisons were included (two of prevention and 24 of treatment strategies). RESULTS - LOW-LEVEL LASER THERAPY, THERAPEUTIC ULTRASOUND, ELECTROTHERAPY AND ELECTROMAGNETIC THERAPY: Four RCTs of laser (for venous leg ulcers), 10 of therapeutic ultrasound (for pressure sores and venous leg ulcers), 12 of electrotherapy (for ischaemic and diabetic ulcers, and chronic wounds generally) and five of electromagnetic therapy (for venous leg ulcers and pressure sores) were included. Studies were generally small, and of poor methodological quality. CONCLUSIONS (1) Foam alternatives to the standard hospital foam mattress can reduce the incidence of pressure sores in people at risk, as can pressure-relieving overlays on the operating table. One study suggests that air-fluidised therapy may increase pressure sore healing rates. (2) Compression is more effective in healing venous leg ulcers than is no compression, and multi-layered high compression is more effective than single-layer compression. High-compression hosiery was more effective than moderate compression in preventing ulcer recurrence. (3) There is generally insufficient reliable evidence to draw conclusions about the contribution of laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy to chronic wound healing.

Bandages↗

PubMed1992

[Local compressibility of denture foundation--evaluation of denture foundation in relation to impression pressure].

The viscoelastic character of the denture foundation is different in each individual or site. The character of the mucosa and the appropriate impression procedure should be examined. However, few investigations concerning the relation between the compressibility of the denture foundation and the impression pressure have been reported. The purpose of this study was to discuss the objective evaluation of the denture foundation in relation to the impression pressure. In this report, the local compressibility of the denture foundation of 20 upper edentulous patients was measured with the 20 MHz B-Mode ultrasonic diagnostic equipment. The Compressible Index was defined to analyze the compressibility of the denture foundation quantitatively as against the impression pressure. The main results were as follows: 1. The compressible amount of the denture foundation against 100 gw/cm2 pressurization was an average of 0.32-0.61 mm. 2. The compressible rate of the denture foundation against 100 gw/cm2 pressurization was an average of 13.5-20.7%. 3. The Compressible Index was confirmed to represent the compressibility of the denture foundation accurately as against the impression pressure. 4. It was suggested that the Compressible Index was useful for the clinical simple evaluation of the denture foundation.

Aged↗

PubMed2000

Grading, image analysis, and stereopsis of digitally compressed fundus images.

PURPOSE: To investigate the effects of image digitization and compression on the ability to identify and quantify features in color fundus photographs. METHODS: Color fundus photographs were digitized as tagged image file format (TIFF) and high-compression (80:1) and low-compression (30:1) joint photographic experts group (JPEG) images. Rerendered images were subjected to standard grading protocols developed for a clinical trial, and digitized images were subjected to image analysis software for drusen identification and quantitation. Re-created stereoscopic images were compared subjectively with originals. RESULTS: Original, TIFF, and low-compression (30:1) JPEG images were virtually indistinguishable when subjected to close scrutiny with magnification. The overall quality of high-compression (80:1) JPEG images and images digitized at 500 dots per inch was markedly reduced. Protocol grading of original and digitized images was highly concordant within the repeatability of multiple grading of original images. The area subtended by drusen differed by less than 1.0% for all uncompressed and compressed image pairs quantified. Stereoscopic information was accurately preserved when compared with originals for TIFF and low-compression JPEG images. CONCLUSIONS: Fundus images can be digitized and stored with significant compression while preserving stereopsis and image quality suitable for quantitative image analysis and semiquantitative grading. Low-compression (30:1) JPEG images may be suitable for archiving and telemedical applications.

Depth Perception↗

PubMed2000

Biological sequence compression algorithms.

Today, more and more DNA sequences are becoming available. The information about DNA sequences are stored in molecular biology databases. The size and importance of these databases will be bigger and bigger in the future, therefore this information must be stored or communicated efficiently. Furthermore, sequence compression can be used to define similarities between biological sequences. The standard compression algorithms such as gzip or compress cannot compress DNA sequences, but only expand them in size. On the other hand, CTW (Context Tree Weighting Method) can compress DNA sequences less than two bits per symbol. These algorithms do not use special structures of biological sequences. Two characteristic structures of DNA sequences are known. One is called palindromes or reverse complements and the other structure is approximate repeats. Several specific algorithms for DNA sequences that use these structures can compress them less than two bits per symbol. In this paper, we improve the CTW so that characteristic structures of DNA sequences are available. Before encoding the next symbol, the algorithm searches an approximate repeat and palindrome using hash and dynamic programming. If there is a palindrome or an approximate repeat with enough length then our algorithm represents it with length and distance. By using this preprocessing, a new program achieves a little higher compression ratio than that of existing DNA-oriented compression algorithms. We also describe new compression algorithm for protein sequences.

Algorithms↗

PubMed2003

Leg compression and ambulation is better than bed rest for the treatment of acute deep venous thrombosis.

AIM: Treatment of acute deep venous thrombosis (DVT) with low-molecular-weight heparin and vitamin K-antagonists reduces the risk of thrombus progression and pulmonary embolism but has no immediate effect on signs and symptoms. We addressed the question whether adding compression and walking would lead to a more rapid clinical improvement than bed rest. METHODS: Fifty-three symptomatic outpatients with proximal DVT were randomly treated, in addition to dalteparin and phenprocoumon, with either firm inelastic bandages (n=18), elastic compression stockings (n=18), both combined with immediate deliberate ambulation, or bed rest without any compression (n=17). We assessed daily walking distance, well-being, quality of life, pain, swelling and clinical scores over a period of 9 days. Lung scans and ultrasound of the leg were performed on days 0 and 9. RESULTS: In the compression groups the walking distance increased with time to 4 km/day on average. Improvement of well-being and DVT-related quality of life was significantly faster and more pronounced with compression than with bed rest (p<0.05 for stockings, p<0.001 for bandages). Pain monitored by visual analogue scale decreased with time in a linear pattern in all groups (p<0.001). There was a significant difference between the groups (p<0.01), the best effect being achieved with bandages. Pain assessed by a provocation test was reduced by half on day 3 with bed rest but remained constantly present over the subsequent 6 days. With compression it was reduced to near baseline on day 3. Swelling was almost completely removed with compression and clinical scores also improved more than with bed rest (p<0.001). Thrombus progression, as studied with ultrasound, was less frequent and less pronounced in the compression groups than with bed rest. There was no difference of new pulmonary embolism on repeat lung scans. CONCLUSION: Leg compression combined with walking is the better alternative to bed rest for the treatment of symptomatic outpatients with proximal DVT.

Acute Disease↗

PubMedDate not supplied

Data compression for storage of resting ECGs digitized at 500 samples/second.

Data compression of resting electrocardiograms (ECGs) digitized at 500 samples per second (sps) is presented. Tradeoffs between the fidelity of reconstructed data and the overall compression are examined. Data of the median (average) complexes are retained at 500 sps and full resolution and encoded only to reduce redundancy. The raw data for rhythm analysis are evaluated for lowpass filtering and down-sampling (decimation) and requantization. After subtracting the medians from the raw data, the resulting residue signal is examined in detail for data reduction and encoding. Various options for compression of the residue signal are presented. Specific issues examined are the acceptable decimation and requantization of the residue signal. Another important aspect evaluated is the bimodal decimation of the QRS and the rest of the cardiac complex. Here, the QRS complexes are kept at 500 sps and the rest of the data decimated to lower sampling rates. This novel approach reduces data distortion while achieving significant compression. Details of the compression scheme and its evaluation on uncompressed 500-sps ECGs from the European Common Standards for Electrocardiography (CSE) database (128 ECGs with normal sinus rhythm, atrioventricular blocks, atrial fibrillation and flutter, ventricular arrhythmias, and excessive noise) are elucidated. Performance indexes [root mean square (RMS) error, percent RMS difference, normalized RMS difference, maximum peak error, and compression ratio] are computed. To validate the compression method, qualitative evaluation was performed by two physicians overreading the ECGs by comparing the reconstructed waveforms with the original uncompressed data. The median data are retained at 500 sps and full precision. For rhythm data, the bimodal decimation of the residue signal to 125 sps at 10 microvolts resolution preserved the fidelity of the ECG signals well, while giving good data compression. Abnormal atrial activity was well preserved and the QRS was retained without distortion. The average size of a 10-sec compressed ECG with the medians is around 4.5 kilobytes.

Diagnosis, Computer-Assisted↗

PubMed2005

[Utilization of compressed Chinese fir thinning wood].

With Chinese fir thinnings as raw material, and through measuring the physical-mechanical indices of its compressed wood, observing the variation of its microstructure and using IR analysis, an optimized technique of compressing Chinese fir thinnings was established. The technique was: compression ratio 50%-60%, thickness after compression 20 mm, moisture content before compression 50%, compressing time 20-30 minutes, and hot compressing temperature 180-200 degrees C. CH, an environmentally friendly cooking additive, had positive effects on softening the wood. During compressing, only the cells of fast-growing Chinese fir were extruded, their cavity became smaller, while the cell wall was not destroyed. The thickness reversion ratio of compressed wood was 2.68%, and its size stability and mechanical quality were as good as hardwoods (Betula lumninifera).

Cunninghamia↗

PubMed1975

Hypertension from compression and/or enucleation of the adrenal glands in the rat.

Previos studies have shown that compression of the adrenal glands is as effective as adrenal enucleation in causing hypertension in rats. Unilateral adrenal enucleation is ineffective, however, if a normal contralateral adrenal gland is present. The studies reported herein demonstrate that unilateral compression also fails to cause hypertension in the presence of a normal contralateral gland. When present singly, either enucleate or compressed adrenals cause hypertension; when either is present with a normal contralateral gland, the blood pressure is unaffected. When compressed or enucleate glands constitute the pair, in any combination, hypertension ensues. However, whereas an enucleate gland remains extremely atrophic in the presence of a normal gland, compressed glands attain a much larger size under this circumstance. Furthermore, a compressed gland is less inhibitory to the regeneration of a contralateral enucleate gland than is a normal adrenal. Whereas enucleate glands, whether bilateral or unilateral, are always smaller than normal glands, compressed adrenals may be enlarged. The hypertensogenic function of compressed adrenals is, like that of enucleate glands, suppressed by the presence of a normal gland. The growth response of compressed or enucleate glands, whether bilateral or single, appears to depend upon the degree of injury inflicted upon them. There is a considerable discrepancy in the size of individual members of a pair when one or both have been injured, that members of a normal pair do not exhibit.

Adrenal Glands↗

PubMedDate not supplied

Vascular compression in the thoracic outlet. Age dependent normative values in noninvasive testing.

Thoracic outlet syndromes are the result of vascular and/or nerve compression. In order to diagnose these syndromes careful clinical examination and objective testing are required. Vascular compression can be provoked by three well-defined thoracic outlet compression manoeuvres. Changes in vascular pulsation during these manoeuvres can be registered by means of plethysmography of the fingers. For an adequate interpretation of the clinical value of the various techniques of provoking vascular compression, a knowledge is required of the frequency with which vascular compression can be provoked in normal subjects of different age groups. We measured the changes in pulse in normal volunteers in 5-year age groups ranging from 15 to 85. This study showed that vascular compression until zero flow during 120 degrees arm abduction seems to be normal rather than abnormal. Zero flow during Adson manoeuvre and military attitude did not occur frequently in the supine position in normal subjects. Neither the different age groups nor the sexes showed any real differences in the quality of the findings. Therefore, establishing zero flow by means of a costoclavicular compression or scalenic compression is a clinically significant finding, while zero flow during 120 degrees abduction (pectoralis minor compression) is within normal limits.

Adolescent↗

PubMed1980

[Long bone healing after transverse osteotomy under constant interfragmentary compression. Animal experiments (author's transl)].

The reaction of cortical contact areas, after osteotomy of a tubular bone, to a constant interfragmentary pressure has not been studied in exact terms so far because of lack of an adequate testing system. The present experimental study therefore examines the influence of various, but during the experiment constant, static pressures on the healing process of the cortical bone. Departing from the basic interrelation between fixation and interfragmentary compression (in the following briefly called: pressure) and from the resulting more or less limited mobility of the bone parts, following osteotomy, it appeared necessary to concentrate observation on either of the two parameters "fixation" or "pressure" alone. For this animal experiment a suitable external compression apparatus was developed so as to secure the application of a constant pressure. The present study contains construction drawings and data on the constructional assembly and integration of these newly developed compression apparatuses and pressure measuring devices. The compression apparatuses permit by variable spring configurations to produce pressures up to a maximum force of 1000 newton. To control the pressure exerted over a period of many weeks, a special measuring system had to be used to provide for a correction of the losses of pressure as occurring, for different reasons, during the progress of the experiment. One chapter is devoted to the various possible methods of pressure measuring. From among the available methods a pressure measuring system, operating on the principle of induction, was selected for practical realization of a model, and produced in a small series. The experiments pressure ranges of 100, 400 and 800 newton as criteria of interfragmentary compression, were carried out on 20 sheep's metacarpal bones, following osteotomy. During the six weeks experiment, current pressure corrections within a maximum of 10 pc of the nominal pressure were necessary, particularly during the first two weeks. X-ray examination showed with the increase of interfragmentary pressure an ever later beginning and ever less substantial formation of callus, regularily in a process of periosteal formation of callus. The lower the interfragmentary compression became, the earlier and the more frequently resorptive changes in the cortical bone occurred. Findings in the cortical contact areas, obtained microscopically from fluoro-chrome-labelled ground-sections and from corresponding microradiographs, in about half of the cases showed a formation of resorption cavities whose extent increased with the decrease of interfragmentary compression. An effect, observed parallel with this finding and with decreasing interfragmentary compression, was an intensified and earlier bone fill-up reaction. Also Havers' remodelling of the corticalis showed a tendency of increasing with the decrease of interfragmentary compression...

Animals↗

PubMed1995

Detection of discrete white matter lesions after irreversible compression of MR images.

PURPOSE: To validate the use of techniques of irreversible compression of images, which can be performed using a block-based discrete cosine transform technique as defined by the Joint Photographic Experts Group, before they can be used in clinical applications, by evaluating the effect of compression on the ability of observers to detect discrete white matter lesions on MR images of the brain. METHODS: Sixty T2- and intermediate-weighted spin-echo images were compressed with varying degrees of coefficient quantization with compression ratios from 1:1 to more than 40:1, randomized, and evaluated by three observers blinded to the degree of compression. RESULTS: No significant difference in the number of lesions detected was apparent until compression ratios reached 40:1, despite a significant subjective loss in perceived image quality at 20:1. Only small (< or = 5 mm) lesions were missed at the highest degree of compression. No significant differences were observed in the detection of confluent periventricular white matter disease at any degree of compression tested. CONCLUSIONS: The use of high degrees of irreversible compression of MR images may be acceptable for diagnostic tasks.

Brain↗