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At least 1,549 records · Page 86Linked to original sources
PubMed2001

The effects of different image file formats and image-analysis software programs on dental radiometric digital evaluations.

OBJECTIVES: To determine if variations in radiodensity data are introduced by lossy Joint Photographic Experts Group (JPEG) compression and/or the use of three software programs. METHODS: An occlusal film with an aluminium step wedge was exposed, processed and digitized under standard conditions. Before the image was saved, the coordinates and the gray-scale value for each pixel in a 20 x 20 pixel area near the middle of the thickest step were recorded. These pixel coordinates and gray-scale values served as Truth 1. In addition, a digital simulated-radiographic image with assigned gray-scale values for each pixel was created and served as Truth 2. The digital data for the scanned radiograph and the simulated radiograph were saved as Tagged Image File Format (TIFF) and lossy JPEG files. Each file was opened with three software programs and the gray-scale values of homologous pixels were recorded. For these pixels in each image type, the mean gray-scale values and standard deviations were calculated. The pixel gray-scale values for each homologous pixel were also individually compared. RESULTS: When the TIFF images were opened with the three software programs, one program resulted in gray-scale values that were not concordant with truth. All JPEG images resulted in gray-scale values that were not concordant with truth. CONCLUSIONS: One software program added a column of 0s to data files. Lossy JPEG compression introduced potentially deleterious variations to radiodensity data, and at least two of the software programs performed JPEG image decompression differently.

Absorptiometry, Photon↗
PubMed2004

Influence of the punch diameter and curvature on the yield pressure of MCC-compacts during Heckel analysis.

The volume reduction behaviour of powders has been quantified by means of the 'in-die' yield pressure (YP) using Heckel analysis. However, because different YPs are reported for the same material, the experimental conditions influencing this material-constant were investigated. Silicified microcrystalline cellulose was compressed into flat-faced and convex tablets using a compaction simulator instrumented with load and displacement transducers. During compression, upper and lower punch force and displacement data were recorded and corrected for punch deformation. A symmetrical triangle wave compression profile was used and the instantaneous punch velocity was kept constant (5mm/s). Individual tablet height and weight were used for Heckel analysis. The influence of the 'effective compression pressure' (P(EFF)) (ranging from 10 to 350 MPa), punch diameter (PD) (4, 9.5 and 12 mm) and filling depth (FD) (4.5, 7.5 and 10.5mm) on YP was statistically evaluated using Response Surface Modelling software. A quadratic surface response equation, describing the relationship between P(EFF), PD, FD and YP, was proposed for concave (Adj R(2): 0.8424; S.D.: 14.60 MPa) and flat-faced (Adj R(2): 0.8409; S.D.: 4.49 MPa) punches. YP and tensile strength were mainly determined by P(EFF), irrespective of punch curvature. FD and PD had only a minor influence on the YP, although more pronounced for the concave punches. The method used resulted in reproducible P(EFF) and tensile strength values and the flat-faced tablets showed less weight variation. Flat-faced punches are preferred over punches with a concave surface when investigating the volume reduction behaviour of a powder by means of Heckel analysis and the experimental parameters should be reported.

Cellulose↗
PubMed2004

Frequency Finder: a multi-source web application for collection of public allele frequencies of SNP markers.

Publicly available single nucleotide polymorphism (SNP) allele frequencies are an important resource for the selection of genetic markers that may be most useful for gene mapping and association studies. Data mining these allele frequencies through disparate public databases and Websites is time consuming and can result in inconsistent findings. We have developed a web-based software tool, Frequency Finder, to acquire SNP allele frequencies from multiple public data sources and return a summarized result to the user. Our software optimizes and automates the search of candidate markers, decreasing the amount of time it would take to extract pertinent data manually. We have included several methods to output the data, including on-screen and as a compressed text file. We show that Frequency Finder accurately retrieves available frequency data from the available sources. Using this tool, we detect significant differences between Asian, African and Caucasian populations in the allele frequency spectra of 246 097 SNPs. While limited to public databases that provide web-based access to allele frequencies, Frequency Finder provides a single, user-friendly interface for retrieving allele frequencies for large batches of SNPs from multiple data sources.

Algorithms↗
PubMed1992

The compression of morbidity hypothesis: promise and pitfalls of using record-linked data bases to assess secular trends in morbidity and mortality.

Individuals who are 65 years of age and older have exhibited unprecedented declines in mortality over the past few decades in the United States. Whether this increased survival has been accompanied by delays in the onset of disease or greater age-specific morbidity remains unanswered because of a paucity of reliable information on secular trends in age-specific disease incidence and survival. The Rochester Epidemiology Project (REP) is one of a few existing medical record linkage systems that offer promise of providing some of the necessary information. Several examples are presented that illustrate the potential of medical record-linked data bases for examining secular trends in the association between age at onset of disease and age at death.

Age Factors↗
PubMed2003

Hypertransfusion: a successful method of treatment in thalassemia intermedia patients with spinal cord compression secondary to extramedullary hematopoiesis.

SUMMARY OF BACKGROUND DATA: Extramedullary hematopoiesis is a common compensatory phenomenon to chronic hemolytic anemias including thalassemia. Several sites can be involved including the liver, the spleen, the lymph nodes, and other less common locations. Spinal cord compression may result in the rare cases wherein the hematopoietic develops intraspinally. Treatment of such conditions still is controversial. OBJECTIVE: This article reviews the literature and reports two cases of thalassemia intermedia involving patients who presented with neurologic symptoms after acute spinal cord compression secondary to extramedullary hematopoiesis. METHODS: The diagnosis was established by magnetic resonance imaging. Hypertransfusion therapy was used as our first-line treatment method. RESULTS: Complete neurologic recovery was achieved. Improvement in the neurologic status started as soon as the first week of treatment. CONCLUSIONS: Clinical awareness is important for early diagnosis and prevention of irreversible neurologic complications in such cases. Magnetic resonance imaging is the radiologic method of choice for diagnosing extramedullary hematopoietic masses and for delineating the extent of spinal cord involvement. Hypertransfusion seems to be a promising treatment method that should be recommended as a first-line approach or as an adjuvant therapy to other methods.

Adult↗
PubMed2006

Structure-function relationships in the human visual system using DTI, fMRI and visual field testing: pre- and post-operative assessments in patients with anterior visual pathway compression.

The focus of this project is to improve our understanding of the relationships between brain structure and function in patients presenting with anterior visual pathway compression using functional MRI (fMRI), visual field(VF) maps and diffusion tensor imaging (DTI). Significant visual loss can occur when large pituitary lesions compress the optic chiasm. Surgical resection of these lesions decompresses the chiasm and can lead to visual recovery. In this preliminary study, we selected patients presenting with slowly progressive visual loss secondary to a compressive pituitary region mass. Using preoperative DTI data, we reconstructed white matter projections of the optic radiations and demonstrated a structural correlation with functional vision as quantified by formal visual field mapping and fMRI. The structural data generated through a fiber tracking algorithm may represent a potentially powerful tool to better understand functional visual deficits in patients with anterior visual pathway compression. Furthermore, we believe that specific patterns in preoperative DTI data may predict the likelihood of postoperative visual recovery in a select group of patients.

Brain↗
PubMed1998

The effects of abdominal muscle coactivation on lumbar spine stability.

STUDY DESIGN: A biomechanical model of the lumbar spine was used to calculate the effects of abdominal muscle coactivation on spinal stability. OBJECTIVES: To estimate the effects of abdominal muscle coactivation on lumbar spine stability, muscle fatigue rate, and lumbar spine compression forces. SUMMARY OF BACKGROUND DATA: The activation of human trunk muscles has been found to involve coactivation of antagonistic muscles, which has not been adequately predicted by biomechanical models. Antagonistic activation of abdominal muscles might produce flexion moments resulting from abdominal pressurization. Qualitatively, antagonistic activity also has been attributed to the need to stabilize the spine. METHODS: Spinal loads and spinal stability were calculated for maximum and submaximum (40%, 60% and 80%) efforts in extension and lateral bending using a previously published, anatomically realistic biomechanical model of the lumbar spine and its musculature. Three different antagonistic abdominal muscle coactivation patterns were imposed, and results were compared with those found in a model with no imposed coactivation. RESULTS: Results were quantified in terms of the sum of cubed muscle stresses (sigma sigma m3, which is related to the muscle fatigue rate), the maximum compressive loading on the lumbar spine, and the critical value of the muscle stiffness parameter (q) required for the spine to be stable. Forcing antagonistic coactivation increased stability, but at the cost of an increase in sigma sigma m3 and a small increase in maximum spinal compression. CONCLUSIONS: These analyses provide estimates of the effects of antagonistic abdominal muscle coactivation, indicating that its probable role is to stabilize the spine.

Abdominal Muscles↗
PubMed2004

Review of technology: planning for the development of telesonography.

Teleradiology allows contemporaneous interpretation of imaging exams performed at some distance from the interpreting radiologist. The transmitted images are usually static. However, there is benefit to real-time review of full-motion ultrasound (US) exams as they are performed. Telesonography is transmission of full-motion sonographic data to a remote site. We hypothesize that US exams, read after having been compressed utilizing Motion Picture Experts Group version 4 (MPEG-4) compression scheme, transmitted over the Internet as streaming multimedia, decompressed, and displayed, are equivalent in diagnostic accuracy to reading the examinations locally. MPEG-4 uses variable compression on each image frame to achieve a constant output bit rate. With less compression, the bit rate rises, and the only way the encoder can contain bit rate within the set bandwidth is by lowering frame rate or reducing image quality. We review the relevant technologies and industry standard components that will enable low-cost telesonography.

Biomedical Technology↗
PubMed2004

[The evaluation of balloonkyphoplasty for osteoporotic vertebral fractures. An interdisciplinary concept].

BACKGROUND DATA: Patients with osteoporotic vertebral compression fractures frequently complain of pain and a loss of function and mobility. Such fractures are associated with an increased mortality. The common treatment with bed rest, bracing or osteosynthesis does not lead to satisfying results. With two new surgical techniques, vertebroplasty and kyphoplasty, an internal stabilisation of osteoporotic vertebral fractures is possible. METHODS: All patients were treated by kyphoplasty. With a minimal invasive dorsal approach, an inflatable bone tamp is placed in the fractured vertebral body. This tamp can restore the vertebral body height and create a cavity, which is filled with bone cement under low pressure. The advantage of kyphoplasty compared to vertebroplasty is the restoration of the vertebral height and a decreased cement leakage rate. We performed a prospective, interdisciplinary study with a follow-up of 12 months. We treated 192 vertebral fractures in 102 patients. Augmentation was performed with polymethylmethacrylate in 138 cases and with a new injectable calcium phosphate-cement in 54 vertebral bodies. Outcome data were obtained with two different spine-scores and by the radiomorphometric evaluation of x-rays before and after treatment. RESULTS: We noticed a significant improvement in pain and function in 89% of the patients. All patients showed a regain of vertebral height of on average 17%. In 7% of all treated vertebral bodies, we noticed cement leakage, which was, however, far below the rates published for vertebroplasty (20-70%). There were two complications, bleeding due to an unknown coagulopathy and a violation of the myelon by malpunction. CONCLUSION: Kyphoplasty is a reliable and minimally invasive method for stabilizing fractured osteoporotic vertebral bodies. Improvement of pain and function and a regain in height of the treated vertebral body can be accomplished.

Aged↗
PubMed2006

MR angiography of the hand with subsystolic cuff-compression optimization of injection parameters.

OBJECTIVE: The purpose of our study was to assess the impact of various injection rates on contrast-enhanced high-resolution 3D MR angiography of the hand. MATERIALS AND METHODS: Ten healthy individuals (mean age, 24.4 years; range, 20-27 years) underwent 3D contrast-enhanced MR angiography of both hands. Starting 3 minutes before data acquisition, subsystolic upper arm cuff compression was applied unilaterally. A 1.5-T whole-body scanner with 3D gradient-echo sequence was used. Seven data sets (20 seconds) were obtained consecutively. I.v. contrast material of 0.1 mg/kg of body weight of gadobutrol was injected at rates of 0.5, 1.0, and 1.5 mL/s. For both hands, quantitative data evaluation was performed with contrast-to-noise ratio (CNR) in the radial, ulnar, palmar, and digital arteries and veins. Qualitative assessment of the arterial visualization score and venous contamination score was rated by two experienced radiologists using a 4-point scale. RESULTS: The lowest venous contamination score (CNR and reviewers' assessment) was observed with an injection rate of 0.5 mL/s (p < 0.05). For the arterial signal, the reviewers' assessment was that an injection rate of 0.5 mL/s was best (p = 0.08). Compression yielded a significantly lower venous contamination score for the compressed side than for the noncompressed side for flow rates of 0.5 mL/s and 1.0 mL/s (p < 0.05). CONCLUSION: Image quality of hand MR angiography was better with cuff compression. A flow rate of 0.5 mL/s yielded a good CNR and a significantly lower venous contamination score than the other flow rates.

Adult↗
PubMed2006

Fracture resistance of weakened roots restored with a transilluminating post and adhesive restorative materials.

STATEMENT OF PROBLEM: The increase in wall thickness of weakened roots using composite resins may increase the root resistance to fracture. However, little is known about the recently developed methods for intraradicular reinforcement of weakened roots. PURPOSE: The purpose of this study was to determine the fracture resistance of experimentally weakened roots reinforced with composite resins, compared with conventional systems that use cast and prefabricated posts. MATERIAL AND METHODS: Forty-eight maxillary incisors were divided into 6 groups (n = 8). The control group (C) used a conventionally prepared root canal filled with cast CuAl posts. Experimental groups had the root canals overprepared to weaken them and were restored as follows: CP, cast CuAl posts; LT, light-transmitting polymerization post (Luminex) + Tetric Ceram resin + prefabricated titanium post (PTP); LF, Luminex posts + Filtek Supreme resin + PTP; LZ, Luminex posts + Z100 resin + PTP; and LR, Luminex posts + Renew resin + PTP. All posts were cemented with a resin luting agent (C & B Cement). Specimens were subjected to compressive load (N) until fracture. Data were submitted to 1-way analysis of variance and the Dunnett test (alpha = .05). RESULTS: There was significant difference (P < .01) between the conventionally prepared specimens and those filled with a cast post (C, 447.8 +/- 167.9) and the overprepared specimens and those filled with a cast post (CP, 212.8 +/- 62.4). No significant differences were found among the control specimens (447.8 +/- 167.9) and the weakened-roots filled with Luminex and composite resins LT (520.9 +/- 173.1), LF (479.9 +/- 214.9), LZ (391.6 +/- 173.6), and LR (333.0 +/- 112.2). CONCLUSION: The use of composite resins in root canals reinforced the weakened roots during fracture resistance testing.

Analysis of Variance↗
PubMed1998

[Percutaneous suture of femoral artery access sites after diagnostic heart catheterization and or coronary intervention. Safety and effectiveness of a new arterial suture technic].

UNLABELLED: The safety and efficacy of a suture-based closure device designed to achieve hemostasis at the femoral access site post catheterization procedures was compared to manual compression in a 600 patients randomized trial (data available for 590 patients). The patients were randomized to percutaneous vascular surgery (PVS) or manual compression after diagnostic (401 patients) and interventional (189 patients) procedures. Two types of PVS devices were used delivering 1 or 2 sutures at the arterial access site. The overall results as well as the results by procedure type demonstrated a significant reduction in time of hemostasis (7.8 +/- 4.8 min vs 19.6 +/- 13.2 min, p < 0.01) and time to ambulation (4.5 +/- 6.5 hours vs 17.8 +/- 5.0 hours, p < 0.01) with the use of the PVS device. The safety results showed no significant differences in the incidence of vascular complications (5.7% for PVS vs 11.3% for compression) in the overall population or in the interventional patients subset (8.4% for PVS vs 9.6% for compression). However, the PVS device demonstrated a significant reduction in the incidence of vascular complications post diagnostic catheterization procedures (4.4 for PVS vs 12.1% for compression, p < 0.05). The incidence of vascular complications and the time of hemostasis was similar in an American multicenter study (STAND II). CONCLUSION: Percutaneous vascular surgery is a safe and effective method to achieve hemostasis post catheterization procedure providing faster hemostasis and ambulation without increasing the rate of complication.

Cardiac Catheterization↗
PubMed1977

The performance of children with auditory perceptual disorders on a time-compressed speech discrimination measure.

A time-compressed version of the PB-K 50 speech discrimination measure was administered to 20 children diagnosed as displaying auditory perceptual disorders. Results indicated that these children performed equally well at both 0 and 30% time compression. Performance decreased significantly at 60% time compression. Comparison of the results with normative data indicated that performance of the two groups of children was similar at the 30% time compression condition but that children with auditory perceptual disorders performed poorer at both 0 and 60% time compression. The results were discussed relative to short-term memory abilities.

Auditory Perception↗
PubMed1995

[Trial of a small image network system in a radiology department of an university hospital].

This paper describes the construction of an image network system in Shinshu University Hospital, and some of its current issues and advantages. Our discussion is based on our experience with a PACS system. SAIPACS, which was installed in 1990 for use in clinical conferencing and pre- and post-graduate education, and with a new CT and MRI network, which was subsequently introduced in 1993. The SAIPACS interconnects eight digital imaging modalities, including CT, MRI, XTV-DR (including digital tomosynthesis), FCR, nuclear medicine (RI), DSA, US, and a film digitizer (FD), with a workstation. Transmission time from the magnetic disk of each imaging modality to the SAIPACS image disk is not rapid enough. Therefore, we need to select images for transfer that are pertinent to our specific purpose, to complete image transmission within a practically acceptable period of time. The new CT/MRI network is composed of two CT units, two MRI systems, an image processing unit and a Universal Gateway. It provides faster image transmission than the SAIPACS system, because there is no need to reform image data to send them in a reversible compressed form. A versatile network system connected to the SAIPACS and CT/MRI network enables digital image data to be processed and edited and images to be transferred back to SAIPACS for clinical or educational use.

Computer Communication Networks↗
PubMed2006

Multiresolution wavelet analysis for efficient analysis, compression and remote display of long-term physiological signals.

Increased inter-equipment connectivity coupled with advances in Web technology allows ever escalating amounts of physiological data to be produced, far too much to be displayed adequately on a single computer screen. The consequence is that large quantities of insignificant data will be transmitted and reviewed. This carries an increased risk of overlooking vitally important transients. This paper describes a technique to provide an integrated solution based on a single algorithm for the efficient analysis, compression and remote display of long-term physiological signals with infrequent short duration, yet vital events, to effect a reduction in data transmission and display cluttering and to facilitate reliable data interpretation. The algorithm analyses data at the server end and flags significant events. It produces a compressed version of the signal at a lower resolution that can be satisfactorily viewed in a single screen width. This reduced set of data is initially transmitted together with a set of 'flags' indicating where significant events occur. Subsequent transmissions need only involve transmission of flagged data segments of interest at the required resolution. Efficient processing and code protection with decomposition alone is novel. The fixed transmission length method ensures clutter-less display, irrespective of the data length. The flagging of annotated events in arterial oxygen saturation, electroencephalogram and electrocardiogram illustrates the generic property of the algorithm. Data reduction of 87% to 99% and improved displays are demonstrated.

Algorithms↗
PubMed2006

[The hardware design of a portable gastrointestinal wireless endoscope image receiver].

The portable gastrointestinal wireless endoscope image receiver is developed and based on TMS320C6211 DSP. It can receive and demodulate the modulated signal which is transmitted from the camera-capsule, and then output the video signal. The synchronizing signals offered by SAA7114H are made best of and are used to design the time logic circuit. The fitful video signal can be collected under the control of the time logic circuit. The circuit can automatically get rid of useless blank data and only collect effective and good-quality video signals, and storage them in CF card. In addition, the image signal can be processed and compressed by DSP, and thus the data storage space and the data- analyzing time can be saved.

Capsule Endoscopes↗
PubMed1998

The effect of neurointermediate lobe denervation on hypothalamic neuroendocrine dopaminergic neurons.

The contribution of tuberohypophyseal and periventricular-hypophyseal dopaminergic neurons to the regulation of the secretion of prolactin (PRL) has yet to be clarified. In this study, we used pituitary stalk compression to disrupt hypothalamic neural input to the neurointermediate lobe (NIL). Neurointermediate lobe denervation (NIL-D) selectively disrupts the axons of tuberohypophyseal and periventricular-hypophyseal dopaminergic neurons, while leaving tuberoinfundibular dopaminergic neurons and the vascular supply of the pituitary gland intact. NIL-D was performed in ovariectomized (OVX) rats. The concentration of DA and 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence (ME) and various regions of the pituitary gland of OVX and OVX+NIL-D rats were measured by HPLC-EC. The concentration of PRL, alpha-melanocyte stimulating hormone (alpha-MSH), and luteinizing hormone (LH) in serum were determined by radioimmunoassay. Successful NIL-D was confirmed by increased water intake. One week after NIL-D, serum PRL and alpha-MSH were elevated, but there was no change in the concentration of LH in serum. The concentration of DA was increased in the median eminence (ME), decreased in the outer zone of the anterior lobe (AL-OZ), as well as the intermediate (IL) and neural lobes (NL), and remained unchanged in the inner zone of the anterior lobe (AL-IZ). The concentration of DOPAC was increased in the ME and NL, decreased in the IL, and remained unchanged in both the AL-IZ and AL-OZ. These data confirm that pituitary stalk compression denervates the NIL. Moreover, decreases in the concentration of DA in the IL and AL-OZ, coupled with elevation of serum PRL and alpha-MSH indicate that DA from the NIL contributes to the increased inhibition of the secretion of PRL and alpha-MSH in OVX rats.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Cholesterol-induced variations in the volume and enthalpy fluctuations of lipid bilayers.

The sound velocity and density of suspensions of large unilamellar liposomes from dimyristoylphosphatidylcholine with admixed cholesterol have been measured as a function of temperature around the chain melting temperature of the phospholipid. The cholesterol-to-phospholipid molar ratio xc has been varied over a wide range (0 </= xc </= 0.5). The temperature dependence of the sound velocity number, of the apparent specific partial volume of the phospholipid, and of the apparent specific adiabatic compressibility have been derived from the measured data. These data are particularly discussed with respect to the volume fluctuations within the samples. A theoretical relation between the compressibility and the excess heat capacity of the bilayer system has been derived. Comparison of the compressibilities (and sound velocity numbers) with heat capacity traces display the close correlation between these quantities for bilayer systems. This correlation appears to be very useful as it allows some of the mechanical properties of membrane systems to be calculated from the specific heat capacity data and vice versa.

Biophysical Phenomena↗