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Biomedical subjects

M J Flynn

Publications and source records attributed to M J Flynn.

At least 19 recordsLinked to original sources
PubMed2002

Bacteriologic findings associated with chronic bacterial maxillary sinusitis in adults.

An open-label, multicenter study was performed to assess bacteriologic findings associated with chronic bacterial maxillary sinusitis in adults. Seventy aerobic (52.2%) and 64 anaerobic (47.8%) pathogens were recovered from clinically evaluable patients at baseline (before therapy). The most commonly isolated anaerobes were Prevotella species (31.1%), anaerobic streptococci (21.9%), and Fusobacterium species (15.6%). The aerobes most frequently recovered included Streptococcus species (21.4%), Haemophilus influenzae (15.7%), Pseudomonas aeruginosa (15.7%), and Staphylococcus aureus and Moraxella catarrhalis (10.0% each). Recurrences of signs or symptoms of bacterial maxillary sinusitis associated with anaerobes were twice as frequent as were those associated with aerobes when counts of anaerobes were > or =10(3) cfu/mL. A pathogenic role for Granulicatella species in cases of chronic sinusitis was documented for the first time.

Adult↗
PubMed2001

Performance evaluation of computed radiography systems.

Recommended methods to test the performance of computed radiography (CR) digital radiographic systems have been recently developed by the AAPM Task Group No. 10. Included are tests for dark noise, uniformity, exposure response, laser beam function, spatial resolution, low-contrast resolution, spatial accuracy, erasure thoroughness, and throughput. The recommendations may be used for acceptance testing of new CR devices as well as routine performance evaluation checks of devices in clinical use. The purpose of this short communication is to provide a tabular summary of the tests recommended by the AAPM Task Group, delineate the technical aspects of the tests, suggest quantitative measures of the performance results, and recommend uniform quantitative criteria for the satisfactory performance of CR devices. The applicability of the acceptance criteria is verified by tests performed on CR systems in clinical use at five different institutions. This paper further clarifies the recommendations with respect to the beam filtration to be used for exposure calibration of the system, and the calibration of automatic exposure control systems.

Calibration↗
PubMed2000

Importance of Dialister pneumosintes in human periodontitis.

Anaerobic bacteria play important roles in the pathogenesis of human periodontitis. This study examined the relationship between a potentially new periodontopathic bacterium Dialister pneumosintes and periodontal disease. A total of 73 women and 62 men aged 18 to 86 years participated in the study. Using a 16S rRNA polymerase chain reaction identification method, the presence of D. pneumosintes was determined in paper-point samples from periodontal pockets of 105 periodontitis and 30 gingivitis patients. D. pneumosintes was detected in 83% of patients having severe periodontitis and in 19% of patients having slight periodontitis. We suggest adding D. pneumosintes to the group of suspected periodontal pathogens.

Adolescent↗
PubMed1999

Image quality degradation by light scattering in display devices.

Veiling glare and ambient light reflection can significantly degrade the quality of an image on a display device. Veiling glare is primarily associated with the diffuse spread of image signal caused by multiple light scattering in the emissive structure of the device. The glare ratio associated with a test image with a 1-cm-diameter black spot is reported as 555 for film, 89 for a monochrome monitor, and 25 for a color monitor. Diffuse light reflection results from ambient light entering the display surface and returning at random emission angles. The diffuse reflection coefficient (luminance/illuminance, 1/sr) is reported as 0.026 for film, 0.058 for a monochrome monitor, and 0.025 for a color monitor with an antireflective surface coating. Both processes increase the luminance in black regions and cause contrast reduction. Specular reflections interfere with detail in the displayed scene. The specular reflection coefficient (luminance/luminance) is reported as 0.011 for film, 0.041 for a monochrome monitor, and 0.021 for a color monitor with an antireflective coating.

Computer Terminals↗
PubMed1999

Experimental comparison of noise and resolution for 2k and 4k storage phosphor radiography systems.

The purpose of this study was to compare the image quality for a digital storage phosphor system using 1760 x 2140 (2k) and 3520 x 4280 (4k) image arrays. Measurements were made on a chest radiography system (Fuji FCR-9501) with special provisions to be operated in both 2k (standard) and 4k (HQ) modes. Presampled modulation transfer functions (MTF) were measured using an edge method. Noise power spectra (NPS) were determined for different input exposures by two-dimensional Fourier analysis. These measures along with exposure measurements and an x-ray spectral model were used to determine the frequency-dependent detective quantum efficiency DQE (f) of the system for the 4k and the 2k modes. The magnitude of the NPS for the 4k mode was about 1/2 that of the 2k mode. A MTF value of 0.5 was found at 1.25 cycles/mm for the 4k system and 1.50 cycles/mm for the 2k system. The 4k images had an extended MTF of 0.1 at 4.5 cycles/mm in the plate-scan direction. Overall, the DQE (f) of the 4k mode was slightly better than that for the 2k mode by about 0.02 due primarily to its better noise characteristics.

Biophysical Phenomena↗
PubMed1999

Detection of subtle lung nodules: relative influence of quantum and anatomic noise on chest radiographs.

PURPOSE: To assess the relative influence of quantum mottle and structured lung patterns (anatomic noise) on the detection of subtle lung nodules on chest radiographs. MATERIALS AND METHODS: Sixty 8 x 8-cm lung pattern images were extracted from digital chest radiographs in healthy individuals. Sixty quantum mottle images of the same size and quantum noise level were extracted from uniformly exposed digital radiographs. Simulated nodules with various peak contrast-diameter products (CD) that emulated subtle tissue-equivalent lung nodules were numerically superimposed at the center on three-fourths of the images. Printouts were independently viewed and scored by five experienced radiologists. The area under the receiver operating characteristic curve (Az) was estimated as a measure of the detectability of the nodules. RESULTS: At a fixed observer performance level (e.g., Az = 0.8), much smaller and lower-contrast nodules were detected on quantum mottle images (1-mm diameter, CD = 0.01 mm), compared with those on anatomic images (4.5-mm diameter, CD = 0.20 mm). The findings generally agreed with the signal-to-noise ratio calculations based on statistical observer models. CONCLUSION: The detection of subtle lung nodules on chest radiographs is limited by anatomic noise.

Adult↗
PubMed1998

A method for measuring the presampled MTF of digital radiographic systems using an edge test device.

The modulation transfer function (MTF) of radiographic systems is frequently evaluated by measuring the system's line spread function (LSF) using narrow slits. The slit method requires precise fabrication and alignment of a slit and high radiation exposure. An alternative method for determining the MTF uses a sharp, attenuating edge device. We have constructed an edge device from a 250-microm-thick lead foil laminated between two thin slabs of acrylic. The device is placed near the detector and aligned with the aid of a laser beam and a holder such that a polished edge is parallel to the x-ray beam. A digital image of the edge is processed to obtain the presampled MTF. The image processing includes automated determination of the edge angle, reprojection, sub-binning, smoothing of the edge spread function (ESF), and spectral estimation. This edge method has been compared to the slit method using measurements on standard and high-resolution imaging plates of a digital storage phosphor (DSP) radiography system. The experimental results for both methods agree with a mean MTF difference of 0.008. The edge method provides a convenient measurement of the presampled MTF for digital radiographic systems with good response at low frequencies.

Computer Simulation↗
PubMed1997

Absence of Porphyromonas asaccharolytica, Bacteroides fragilis and Chlamydia pneumoniae in human subgingival plaque.

Little is known about the presence of common medical pathogens in the human oral cavity. Using a 16S rRNA-based PCR identification method, this study determined the occurrence of Porphyromonas asaccharolytica, Bacteroides fragilis and Chlamydia pneumoniae in subgingival plaque from 50 adults with advanced periodontitis. Each patient contributed samples from 3 deep periodontal pockets collected by paper points. The PCR primers were for P. asaccharolytica 5'-CTC TAG CTA GAG TGT ACT GG-3' and 5'-ATA GGG TTT ATA GAT TAG CTC TCT-3', for B. fragilis 5'-AAT GAT TCC GCA TGG TTT CAT TA-3' and 5'-GCG GTG ATT GCT CAC TGA CA-3', and for C. pneumoniae 5'- TGA CAA CTG TAG AAA TAC AGC-3' and 5'-CGC CTC TCT CCT ATA AAT-3'. The primers yielded a single amplicon with the respective reference strains and produced no amplicon with colonies of 25 groups of oral organisms. None of the three test species were detected in any of the 50 pooled subgingival samples tested. P. asaccharyolytica, B. fragilis and C. pneumoniae do not seem to be part of the periodontopathic microbiota in humans.

Adult↗
PubMed1997

Simulation of subtle lung nodules in projection chest radiography.

PURPOSE: To measure the radiologic characteristics of subtle lung nodules and develop nodule phantoms that simulate these characteristics. MATERIALS AND METHODS: From a database of chest radiographs, 16 radiographs that showed confirmed subtle lung nodules were selected. The optical density values surrounding each nodule were obtained, and the radiologic characteristic of the nodules were evaluated. A set of Teflon nodule phantoms with similar x-ray transmission and variability was designed and fabricated. The contrast characteristics of the images of the nodule phantoms were measured. RESULTS: Most of the subtle nodules appeared to have diffuse edges with Gaussian-like contrast profiles. The contrast and size characteristics of the nodule phantom images fulfilled the design criteria within a 4% deviation. CONCLUSION: The radiologic pattern of subtle lung nodules is poorly simulated by nodule phantoms with simple spherical or disk shapes. The nodule phantoms in this study produce realistic radiographic patterns with an energy-dependent attenuation equivalent to that of tissue. The nodule phantoms are intended for use in experiments involving human subjects.

Humans↗
PubMed1997

Oral food consumption and subgingival microorganisms: subgingival microbiota of gastrostomy tube-fed children and healthy controls.

This study examined the effect of oral food consumption on the prevalence and levels of subgingival bacteria and yeasts in 20 gastrostomy tube-fed children and 24 healthy controls. Microbial identification was carried out using anaerobic culture and 16S rRNA-based PCR identification methods. Streptococcal and Actinomyces species were recovered from 100% and 76% of all subjects and averaged 66% and 11% of total cultivable organisms, respectively. In decreasing order of prevalence, Fusobacterium, enteric rods, Prevotella intermedia/Prevotella nigrescens, Capnocytophaga, Propionibacterium, yeasts, Actinobacillus actinomycetemcomitans, coagulase-negative Staphylococcus, Campylobacter rectus, Bacteroides forsythus, and Porphyromonas gingivalis were detected in 48% to 2% of the study subjects. The cultivable levels of these species varied widely among subjects. PCR detection showed C. rectus and Eikenella corrodens both to occur in 93% of the study subjects and to be the most prevalent putative periodontal pathogens examined. In decreasing order of prevalence, PCR identified Treponema denticola, A. actinomycetemcomitans, P. nigrescens, P. intermedia, B. forsythus, and P. gingivalis in 38% to 21% of the subjects studied. Tube-fed children and healthy controls exhibited similar subgingival microbial compositions. It appears from this study that oral food consumption is not a major determinant for the establishment of subgingival microbiota in children.

Actinomyces↗
PubMed1997

Terbutaline pump tocolysis in high-order multiple gestation.

OBJECTIVE: To review terbutaline pump tocolytic therapy as part of the management of high-order multiple gestations (triplet and quadruplet pregnancies). STUDY DESIGN: We performed a retrospective review of the medical records of triplet and quadruplet pregnancies cared for by Phoenix Perinatal Associates from August 1988 to January 1992 in whom terbutaline pump tocolysis was administered. RESULTS: The study group consisted of 15 triplet pregnancies and 6 quadruplet pregnancies. The 15 patients with triplets delivered at a mean (+/- SD) gestational age of 33.0 +/- 1.9 weeks. The six patients with quadruplets delivered at 33.0 +/- 1.3 weeks. Only 2 of 15 (13%) of the triplets and 1 of 6 (17%) of the quadruplets were delivered for tocolytic failure. CONCLUSION: Terbutaline pump tocolysis provides safe and effective tocolytic therapy in a select group of high-order multifetal gestations.

Adult↗
PubMed1996

Tetracycline resistance in Prevotella isolates from periodontally diseased patients is due to the tet(Q) gene.

Tetracycline-resistance in gram-negative periodontal bacteria is often due to the presence of the tet(Q) gene. In the present study the polymerase chain reaction (PCR) was used to examine 54 isolates of gram-negative anaerobic rods (Prevotella intermedia, Prevotella nigrescens and related or Bacteroides-like species) for the presence of the tet(Q) gene. The isolates were recovered from 42 patients with periodontal disease living in northern Europe and North America. An 814 base-pair segment of the tet(Q) gene was amplified from all 41 isolates resistant to tetracycline with minimal inhibitory concentrations of 4 micrograms/ml and above. The presence of the tet(Q) gene was verified using hybridization with a specific oligonucleotide internal to the amplified region and restriction endonuclease digestion with DdeI. A PCR product of the same size was also amplified from one tetracycline susceptible isolate (minimal inhibitory concentration = 0.5 microgram/ml). However, this isolate and the one isolate that was resistant to tetracycline at 4 micrograms/ml showed a weaker signal than the remaining isolates when hybridized with the internal probe. Typing of the PCR products using restriction endonuclease digests with AluI and HpaII revealed two clusters of distinct electrophoresis patterns, indicating that two different subtypes of the tet(Q) gene were present in this material. A control strain containing the tet(Q) gene from Bacteroides thetaiotaomicron had a different electrophoresis pattern for AluI. This study indicated that subtypes of the tet(Q) gene in tetracycline-resistant gram-negative periodontal bacteria exist both within the same patient and within the same species.

Base Sequence↗
PubMed1995

Static and fatigue failure properties of thoracic and lumbar vertebral bodies and their relation to regional density.

This study investigated (1) whether a characterization of the macroscopic architecture within the vertebral centrum would improve predictions of vertebral strength, (2) if regions in the centrum where least bone loss with age occurs are more predictive of vertebral strength, and (3) whether different patterns of the macroscopic architecture are predictive of static as compared to fatigue strength. To characterize the vertebral macroscopic architecture, a regional bone mineral density (rBMD) technique was used that estimated the cancellous density distribution (in 18 specific regions of the vertebral centrum) for vertebrae T7-L4, from spines of 20 female cadavers. Static and fatigue failure properties of whole vertebrae were obtained, and predictive models of static and fatigue failure properties of whole vertebrae were examined. We found that (1) vertebral failure properties were better predicted by combinations of vertebral regional cancellous density (multiple linear regressions) rather than by any individual region of cancellous density alone (simple linear regressions); (2) models using regions of density that demonstrated minimum decline with age [from the data of Flynn and Cody (Calcif. Tissue Int. 53, S170-S175 (1993))] resulted in better correlations with ex vivo vertebral static failure properties than models using density regions that showed maximum decline with age, and (3) static and fatigue characteristics required different density regions to reach significance. (A comparison of models predictive of static and fatigue failure properties revealed that anterior density regions were most often included in predictive models of the static properties while posterior regions were more predictive of the fatigue properties).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Detection of putative periodontal pathogens in subgingival specimens by 16S ribosomal DNA amplification with the polymerase chain reaction.

The utility of the 16S ribosomal RNA-based polymerase chain reaction (PCR) for detection of Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, Prevotella intermedia, and Treponema denticola was examined and compared with that of anaerobic culture. Primer pairs consisting of 20-27 nucleotides amplified 404- to 688-bp regions of 16S ribosomal RNA genes of these organisms. This method had a lower detection limit of 50 target cells in a background of 10(7) cells. Its specificity for B. forsythus, P. gingivalis, and T. denticola seemed high. The primers for A. actinomycetemcomitans, C. rectus, and P. intermedia cross-reacted with some closely related species but did not reveal amplification products in tests with more distantly related organisms. The primers for E. corrodens did not seem to cross-react with oral organisms. This PCR technique was sensitive, reproducible, and easy to perform. PCR-based amplification may prove valuable for the detection of some periodontal pathogens in crude subgingival specimens.

Adult↗
PubMed1995

Molecular genetic detection of Bacteroides heparinolyticus in adult periodontitis.

Bacteroides heparinolyticus in subgingival plaque was identified using a digoxigenin-labeled whole genomic DNA probe and a polymerase chain reaction (PCR) assay based on 16S rRNA species-specific primers (5'-ATG GTG ATT CCG CAT GGT TTC TCC-3' (base position, 188-212) and 5'-CAA ACT TTC ACA GCT GAC TTA AGC-3' (592-615)). Subgingival specimens obtained by paper points from 3 deep periodontal pockets in each of 113 adults were examined. The DNA probe reacted with all pure isolates tested of B. heparinolyticus and did not react with other oral species tested; the probe showed positive reactions in 74.3% of the patient samples examined. The PCR primers produced the 428 bp species specific amplification product in all B. heparinolyticus test strains and did not reveal detectable amplicons with strains of other subgingival species. The PCR method detected 50 B. heparinolyticus cells dispersed in subgingival plaque. PCR only revealed B. heparinolyticus in 6.2% of the patient samples studied. The higher level of positive specimens with the DNA probe was probably due to false-positive reactions from cross-hybridization with unknown subgingival species. This study suggests that the PCR method amplifying specific 16S rRNA sequences represents an easy and valuable means to detect B. heparinolyticus in subgingival plaque. The low prevalence of subgingival B. heparinolyticus does not incriminate the organism in the etiology of adult periodontitis.

Adult↗