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At least 595 records · Page 33Linked to original sources

PubMed1993

Clinical furcation diagnoses and interradicular bone defects.

The purpose of the present study was to assess associations between clinical depth of involved furcations and their bony defect depth. Twelve patients with moderate to advanced periodontitis in molars were recruited for clinical evaluation of furcation involvement by 6 dentists. Two groups of 3 dentists were assigned to the right or left half of the dentition. All dentists assessed the clinical depth of involvement of the furcations using the Ramfjord index (2 mm) in patients 1 through 6, and using the Hamp index (3 mm) in patients 7 through 12. Diagnoses were made with calibrated and uncalibrated Nabers 2 probes. After the clinical assessments the patients received full mouth scaling and root planing. After reevaluation the molars were surgically exposed. During surgery the depth of the bony furcation defects was assessed using horizontal probing and impressions. Clinically assessed depth of furcation involvement was then compared with the surgical measurements. A total of 1,180 clinical furcation diagnoses were available, of which 426 could be surgically evaluated using both the straight probe and the impressions. These evaluations were done in a total of 72 furcations using probe and impressions. For the Ramfjord index, 5% of the clinical degree 1, 40% of the degree 2, and 43% of the degree 3 readings were overestimations. For the Hamp index, 7% of degree 1, 24% of degree 2, and 0% of degree 3 readings were overestimations. These clinical diagnoses were overestimations. Forty-three percent of surgical degree 3 involvements were not recognized when using the Ramfjord index, and 27% when using the Hamp Index. These results suggest that furcation diagnosis is of limited validity.

Adult↗

PubMed1989

Tissue air ratio in total body irradiation. An in vivo evaluation.

On the basis of dose readings in 102 patients treated with total body irradiation (TBI), a 'tissue air ratio (TAR) curve' has been produced. It could be useful to precalculate treatment time in TBI, for dose prescription to a specific point, provided the same source (60Co) and treatment setting (lateral irradiation; 3 m source-axis distance; reference point at thighs bifurcation, near the perineum) is used. The TAR curve produced, and the formula relating tissue depth to TAR value, are presented, and compared to preexisting data for 'magna fields' treatments. This curve is exponential, and in semilog representation becomes straight, as every classic TAR curve; it is lower than others, reflecting non full-scatter situation in patient irradiation.

Adolescent↗

PubMed2001

ACLS.

It must be emphasised that the published International Guidelines 2000 contain an in-depth presentation of the scientific evidence behind advanced life support. The exact interpretation of this evidence, and the algorithms adopted by a national resuscitation council will depend upon various factors such as local interpretation of the evidence, local practice and availability of drugs. The ERC is publishing its own summaries of the guideline changes and the sequences of action for both BLS and ALS and these papers are recommended for further reading.

Advanced Cardiac Life Support↗

PubMedDate not supplied

[Experimental-morphological studies on isolation properties of cyanacrylate composite inlays].

The biological tolerance and protective properties of inlays from cyanacrylate composites versus the toxic effect of the composition material have been studied in experiments on dogs. Three polymer compositions were tested in comparison with the widely used phosphate cement. For the purpose of the study, 60 cavities, class V, size 2:4:2.5 mm were treated. Dentin was covered with inlays from experimented materials and the cavities were obturated by evicrol. The histopathological reaction of the dental pulp to the tested materials was read on day 3, 1 and 3 months. They were established to have very good working properties and colour possibilities. No changes in the pulp characteristic for acute or chronic inflammatory reaction were established by the electron microscopic studies. The good immediate and remote results from the experiments carried out are good grounds to admit that the cyanacrylate composites studied are very adequate for application in dental defects with a medium depth and could successfully be applied in the clinical practice. Their suitable colour permits to be used under a thin layer of composition material, not affecting the final aesthetic effect of the obturations.

Animals↗

PubMed1981

Tomographic thyroid scintigraphy: comparison with standard pinhole imaging: concise communication.

Coded-aperture imaging (CAI) and multiple-view pinhole imaging (PI) of the thyroid were compared in a prospective study in 136 consecutive patients. Following 10 mCi of pertechnetate, 200K-count pinhole images were obtained in the anterior, RAO, and LAO projections, and CAI data were obtained in the anterior position. Four coronal tomographic sections were reconstructed by computer. Five observers read the studies separately, and ROC curves were constructed. Based on 109 pairs of studies, the ROC curves revealed similar performance for all observers for both techniques. When four observers compared the studies subjectively they rated the CAI more useful in 36% of cases, the PI in 6%, and the two equal in 58%. The advantages offered by the tomograms included improved contrast, accurate size representation of the gland at all depths, freedom frm pinhole-type distortion, and faster data acquisition. The major disadvantage to tomography was the 2-hr computer-processing time required. It this can be reduced, CAI offers sufficient advantages over conventional pinhole imaging to warrant its routine use.

Adult↗

PubMed1992

Three versus four radial keratotomy incisions.

Radial keratotomy (RK) is currently performed with four or eight semi-radial incisions. To evaluate the effect of a theoretically more stable three-incision RK pattern, centripetal incisions were made in 16 human donor eyes (eight pairs), using a double-edged diamond blade set to 90% of central pachymetry and a 3.5 mm optical clear zone. Intraocular pressure was maintained at 15 mm Hg during surgery and while keratometry readings were made. One randomly selected eye of each pair had three radial incisions made at 12, 4 and 8 o'clock; the other eye had four radial incisions at 12, 3, 6, and 9 o'clock. Corneal flattening was 6.08 diopters (D) with four incisions and 4.84 D with three incisions (P less than .05). Astigmatism increased 0.44 D and 0.69 D, respectively (P greater than .1). Histologically measured mean incision depth (77.4%) did not differ significantly between the groups (P greater than .1). This study shows that 80% of the effect of a four-incision RK pattern can be obtained with a theoretically more stable three-incision pattern.

Aged↗

PubMed2001

An electronic survey of physicians using online clinical discussion groups: a brief report.

INTRODUCTION: Online discussion groups are a relatively new form of informal communication among physicians. Physicians' Online, an Internet-based medical information and communication network with a current membership base that includes more than 200,000, United States physicians, contains extensive bulletin-board discussion areas with more than 47,000 topics posted to date. There are no published data available regarding the characteristics and behaviors of the individuals who participate in these discussions. METHODS: To better characterize the users of these groups, in March 1998, we posted an eight-question, multiple-choice electronic survey on Physicians' Online's home page inviting users of the clinical discussion groups to participate. RESULTS: We analyzed responses from 586 participants. The most common characteristics were: urban and Northeastern United States location, age less than 55 years, clinical practice of internal medicine or one of its subspecialties, private solo or single/multispecialty group practice, and reported weekly consultation with three or less colleagues. Most physicians were interested in specific clinical cases. Forty-one percent of the respondents chose to read discussion groups only but rarely or never initiated or responded. CONCLUSIONS: Younger age, urban setting, private practice, and infrequent consultation with colleagues were the most common characteristics found among users of Physicians' Online's online clinical discussion groups. That specific clinical cases were the most common interest speaks to the notion that discussion groups may represent an attractive resource for helping to manage clinical cases. Future research should explore in greater depth the demographics of users, specific motivations for physician use, ways to improve active participation, and the impact on clinical practice.

Adult↗

PubMed2005

K-band EPR dosimetry: small-field beam profile determination with miniature alanine dosimeter.

The use of small-size alanine dosimeters presents a challenge because the signal intensity is less than the spectrometer sensitivity. K-band (24 GHz) EPR spectrometer seems to be a good compromise between size and sensitivity of the sample. Miniature alanine pellets were evaluated for small-field radiation dosimetry. Dosimeters of DL-alanine/PVC with dimensions of 1.5 mm diameter and 2.5 mm length with 5 mg mass were developed. These dosimeters were irradiated with 10 MV X-rays in the dose range 0.05-60 Gy and the first harmonic (1h) spectra were recorded. Microwave power, frequency and amplitude of modulation were optimized to obtain the best signal-to-noise ratio (S/N). For beam profile determination, a group of 25 dosimeters were placed in an acrylic device with dimensions of (7.5 x 2.5 x 1)cm3 and irradiated with a (3 x 3)cm2 10 MV X-rays beam field size. The dose at the central region of the beam was 20 Gy at a depth of 2.2 cm (build up for acrylic). The acrylic device was oriented perpendicular to the beam axis and to the gantry rotation axis. For the purposes of comparison of the spatial resolution, the beam profile was also determined with a radiographic film and 2 mm aperture optical densitometer; in this case the dose was 1 cGy. The results showed a similar spatial resolution for both types of dosimeters. The dispersion in dose reading was larger for alanine in comparison with the film, but alanine dosimeters can be read faster and more directly than film over a wide dose range.

Alanine↗

PubMed2003

Ocular biometry in occludable angles and angle closure glaucoma: a population based survey.

AIM: To compare ocular biometric values in a population based sample of eyes with occludable angles, angle closure glaucoma, and normal subjects. METHOD: 2850 subjects from a population based glaucoma prevalence study underwent complete ocular examination including indentation gonioscopy. Ocular biometry was performed in all subjects classified to have occludable angles (n = 143); angle closure glaucoma (n = 22), and a random subgroup of 419 normal subjects. Ocular biometry readings between the groups were compared and statistically analysed using "t," "z," and Mann-Whitney U tests. RESULTS: The mean age among subjects with occludable angles (54.43 (SD 9.53) years) and angle closure glaucoma (57.45 (8.5) years) was significantly higher (p<0.001) than normal subjects (49.95 (9.95) years). Axial length was shorter (p<0.001) in the occludable angle group (22.07 (0.69) mm) compared to the normal group (22.76 (0.78) mm). Anterior chamber depth (ACD) was shallower (p<0.001) among subjects with occludable angles (2.53 (0.26) mm) than normal subjects (3.00 (0.30) mm). Lens thickness (LT) was greater (p<0.001) in people with occludable angles (4.40 (0.53) mm) compared to normal subjects (4.31 (0.31) mm). No significant difference was noted in axial length, ACD (p = 0.451), and LT (p = 0.302) between angle closure glaucoma and occludable eyes. CONCLUSION: South Indian eyes with angle closure glaucoma and occludable angles seem to have significantly shorter axial lengths, shallower anterior chambers and greater lens thickness compared to the normal group.

Adult↗

PubMed1981

Negative pion depth-dose profile examined by means of HeLa cell-survival curves.

HeLa cells were irradiated at liquid nitrogen temperature with negative pions from Nimrod at the Rutherford Laboratory and then assayed for survival of colony-forming ability. Complete dose-response curves were obtained from repeated determinations at 14 different positions along the depth-dose profile and survival curves were fitted to the data by computer programme. A depth-damage profile was thus established in terms of the final slopes of these survival curves. This confirmed the expected RBE value of 1.84 at the ionization peak. Although a value of unity was found in the main plateau region, the "entrance" positions showed significantly higher values.

Cell Survival↗

PubMed1998

Measurements of electron beam peak scatter factors.

We have measured the peak scatter factor (PSF) for electron beams which in analogy to photon beams is defined as the ratio of the absorbed dose to water at the depth of dose maximum in a water phantom to the absorbed dose in free air at the same location for a given incident beam. In this study we have measured the PSFs as a function of the incident electron beam energy and field size. We have used both an RK ionization chamber and a silicon diode as radiation detectors. After applying the water/air stopping power ratio and fluence correction factors to the ionization chamber readings, the values of measured PSFs by using two different detectors are in a good agreement. The results show that the value of PSF increases with the increase of the field size and decreases with the increase of the beam energy. The range of the variation with field size between 2 x 2 and 10 x 10 cm2 is 1.24-1.42, 1.15-1.30, 1.15-1.17 for 6, 11, and 20 MeV beams, respectively.

Algorithms↗

PubMed2004

Pelvic orientation and assessment of hip dysplasia in adults.

BACKGROUND: The study was performed to qualify the source material of 4151 pelvic radiographs for the research into the relationship between unrecognised childhood hip disorders and the development of hip osteoarthrosis, and to investigate the effect of varying degrees of pelvic tilt and rotation on the measurements of radiographic indices of hip dysplasia. MATERIAL AND METHODS: We investigated the effect of varying pelvic orientation on radiographic measurements of acetabular dysplasia using a cadaver model. Results from the cadaver study were used to validate the radiographic assessments of acetabular dysplasia in the longitudinal survey cohort of the Copenhagen City Heart Study (CCHS; Osteoarthrosis Sub-study). 1) Cadaver pelvises and proximal femurs from a male and a female donor were mounted anatomically in holding devices allowing independent inclination/reclination and rotation. An AP pelvic radiograph was recorded at each 3 degrees increment. The most widely used radiographic parameters of hip dysplasia were assessed. 2) Critical limits of acceptable rotation and inclination/reclination of pelvises were determined on 4151 standing, standardised pelvic radiographs of the CCHS cohort. RESULTS: Wiberg's CE angle, Sharp's angle, the x-coordinate of Goodman's Cartesian coordinate system, and the acetabular depth ratio were significantly affected by varying rotation and inclination/reclination of the cadaver pelvises. Femoral head extrusion index was not significantly affected within the applied rotation and inclination/reclination of the cadaver study. Application of the corresponding critical limits of Tönnis' foramen obturator index of 0.7-1.8 meant that 188 of 4151 (4.5%) of the CCHS-III pelvic radiographs had to be omitted from further studies. INTERPRETATION: To ensure a neutral starting point and reproducible readings, especially in epidemiological and clinical studies, and when performing preoperative planning and follow-up of patients undergoing redirectional pelvic osteotomies, it is important that all aspects of the radiographic examination are controlled and reproducible. Furthermore, we found that studies of acetabular dysplasia based on supine urograms or colon radiographs without information about pelvic orientation, centering of the X-ray beam and tube to film distance, run a serious risk of erroneous measurements.

Acetabulum↗

PubMed1997

Wavelength selection for low-saturation pulse oximetry.

Conventional pulse oximeters are accurate at high oxygen saturation under a variety of physiological conditions but show worsening accuracy at lower saturation (below 70%). Numerical modeling suggests that sensors fabricated with 735 and 890 nm emitters should read more accurately at low saturation under a variety of conditions than sensors made with conventionally used 660 and 900 nm band emitters. Recent animal testing confirms this expectation. It is postulated that the most repeatable and stable accuracy of the pulse oximeter occurs when the fractional change in photon path lengths due to perturbations in the tissue (relative to the conditions present during system calibration) is equivalent at the two wavelengths. Additionally, the penetration depth (and/or breadth) of the probing light needs to be well matched at the two wavelengths in order to minimize the effects of tissue heterogeneity. At high saturation these conditions are optimally met with 660 and 900 nm band emitters, while at low saturation 735 and 890 nm provide better performance.

Animals↗

PubMed1992

Miles Technicon H.2 automated hematology analyzer.

Automated hematology analyzers are used in all large hospitals and most commercial laboratories, as well as in most smaller hospitals and laboratories, to perform complete blood counts (including white blood cell, red blood cell, and platelet counts; hemoglobin concentration; and RBC indices) and white blood cell differential counts. Our objectives in this study are to provide user guidance for selecting, purchasing, and using an automated hematology analyzer, as well as to present an overview of the technology used in an automated five-part differential unit. Specifications for additional automated units are available in ECRI's Clinical Laboratory Product Comparison System. We evaluated the Miles Technicon H.2 unit and rated it Acceptable. The information in this Single Product Evaluation is also useful for purchasing other models; our criteria will guide users in assessing components, and our findings and discussions on some aspects of automated hematology testing are common to many available systems. We caution readers not to base purchasing decisions on our rating of the Miles unit alone, but on a thorough understanding of the issues surrounding automated hematology analyzers, which can be gained only by reading this report in its entirety. The willingness of manufacturers to cooperate in our studies and the knowledge they gain through participating lead to the development of better products. Readers should refer to the Guidance Section, "Selecting and Purchasing an Automated Hematology Analyzer," where we discuss factors such as standardization, training, human factors, manufacturer support, patient population, and special features that the laboratory must consider before obtaining any automated unit; we also provide an in-depth review of cost issues, including life-cycle cost analyses, acquisition methods and costs of hardware and supplies, and we describe the Hemacost and Hemexmpt cost worksheets for use with our PresValu and PSV Manager CAHDModel software. Readers should also review the Clinical and Technical Overview and the articles "Miles Technicon H.2 Reports" and "Developing the Evaluation Reference Method."

Blood Cell Count↗

PubMed1992

Probe tine diameter and probing depth.

The aim of this study was to assess the effect of difference in tine diameter on probing pocket depth measurement. 2 sets of tines with Williams markings at 1, 2, 3, 5, 7, 8, 9 and 10 mm, and with a "round" tip, diameter 0.5 mm, were compared. One set was described as parallel-sided, the other as tapered. The parallel-sided tine was almost parallel from the 10 mm marking to the tip (tip diameter mean = 0.46 mm, 95% C.I. 0.456-0.464), while the corresponding diameter for the tapered tine varied (tip diameter mean = 0.48 mm, 95% C.I. 0.473-0.489). Calibration markings appeared highly consistent with the expected value to within 0.01 mm. The tines were mounted in Brodontic handles at 0.25 N. Examiner probing repeatability yielded kappa 0.86 for "parallel-sided" and 0.81 for "tapered" tines in vivo. 412 approximal pockets were assessed in 53 patients with routine chronic adult periodontitis, mean age 42.1 years. Each site had a probing depth of greater than or equal to 5 mm, PlI less than or equal to 1, GI less than or equal to 1, PBI less than or equal to 1. Each site was probed 2x with a 15-min interval. At the first 251 sites, the parallel-sided tine was used initially, and the tapered at the remaining 161 sites. Results indicated a highly significant tendency for the parallel-sided tine to yield a deeper reading when a difference occurred. These findings indicate that with adequate training providing high examiner repeatability, one source of error in probing data can be minimised.

Adult↗

PubMedDate not supplied

Ablation design in relation to spatial frequency, depth-of-focus, and age.

PURPOSE: To consider factors relevant to the design of wavefront-aberration-based customized ablations. METHODS: Review. RESULTS: Ablations that seek to eliminate all wavefront aberrations, both second- and higher-order, may not be optimal for all patients. This is particularly the case for presbyopes. Their main requirement will normally be for extended binocular depth-of-focus to yield adequate distance and near vision with good retinal contrast at lower spatial frequencies, rather than the highest levels of acuity and modulation transfer function at a single distance. For many presbyopes, this can be achieved by aiming for monovision correction or low myopic astigmatism, with reasonable but not necessarily complete correction of higher-order aberrations. This compromise allows a range of everyday tasks to be carried out, including face recognition and reading. CONCLUSION: The targeted correction of wavefront aberration should take into account the visual needs and preferences of the individual patient.

Accommodation, Ocular↗

PubMed2006

Heat production by 3 implant drill systems after repeated drilling and sterilization.

PURPOSE: The goal was to measure heat generated in bone by 3 implant drill systems after repeated drilling and sterilization. MATERIALS AND METHODS: Temperature was measured with thermocouple technology in vitro using the bovine femoral cortical bone model. Intermittent drilling was accomplished at a constant 2.4-kg load and drill speed of 2,500 rpm. External irrigation at 40 mL/min with normal saline was used. Three implant drill systems-system A (triple twist drills with a relief angle), system B (triple twist drills without a relief angle), and system C (double twist drills with a relief angle)-were evaluated and heat was measured at the final drill in the drilling sequence (4.0 mm or 4.2 mm) at a depth of 15 mm. Thermocouples were placed 0.5 mm from the osteotomy at a depth of 15 mm. Heat measurements were recorded out to 25 uses. RESULTS: Results showed temperature increased with multiple uses. System A and C drills had temperature measurements that were below 47 degrees C, even after 25 uses. System B drills had temperatures that exceeded 47 degrees C from the initial use. Light microscopy showed little drill wear even after 25 uses. CONCLUSIONS: Drill geometry plays a major role in heat production and may explain the increased temperature readings seen in system B. These drills lack relief angles and have the smallest clearance angles of the 3 systems. It also has fewer drills in its drilling sequence compared with systems A and C. This study shows that temperatures increase when drills are used multiple times. Systems A and C had acceptable temperature measurements out to 25 uses. System B drills showed significantly higher heat production with little visual signs of wear.

Animals↗

PubMed1987

Comparison of dark-field microscopy and a flagella stain for monitoring the effect of a Water Pik on bacterial motility.

The purpose of this examiner-blind study was threefold: to compare the microbial counts obtained by two different techniques for assessing bacterial motility, to assess the inter-rater reliability of these two techniques and to evaluate the effect of a water irrigating device (Water Pik) on bacterial motility at 3- and 6-mm probing depths. Subgingival plaque samples were taken from 10 healthy patients having at least two sites that probed greater than 6 mm, (one control, one experimental). Half of the patients were sampled at 3 mm, the other half at 6 mm, both at baseline (Day 0) and at Day 21. Two slides were prepared from each plaque sample, one for dark-field evaluation and one stained with a simplified silver-plating technique for flagella. All slides were read simultaneously by 3 observers, and the per cent motility calculated for spirochetes, motiles and all others. Strong positive inter-rater reliability correlations ranging from r = 0.95 to r = 0.99 were found for both the dark-field and flagella staining techniques. Spirochete counts obtained by both techniques were highly correlated (r = 0.91), whereas counts for motiles resulted in negative correlations between the techniques. Dark-field counts were consistently higher than the flagella stain counts for motile rods. Spirochetes were reduced, but not significantly, after irrigation of both 3-mm and 6-mm sites. Bacterial motility can be evaluated by both dark-field and flagella-staining techniques with a high degree of inter-rater reliability.

Adult↗