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At least 667 records · Page 37Linked to original sources

PubMed2005

The English strain of rat cytomegalovirus (CMV) contains a novel captured CD200 (vOX2) gene and a spliced CC chemokine upstream from the major immediate-early region: further evidence for a separate evolutionary lineage from that of rat CMV Maastricht.

Sequence data for eight genes, together with time-course Northern blotting and 3'- and 5'-RACE (rapid amplification of cDNA ends) analysis for some mRNAs from a 12 kb region upstream from the major immediate-early (MIE) genes of the English isolate of rat cytomegalovirus (RCMV), are presented. The results identified important differences compared to both murine cytomegalovirus (MCMV) and the Maastricht isolate of RCMV. A striking finding is the presence of a highly conserved, rightwards-oriented homologue of the rat cellular CD200 (OX2) gene immediately to the right of the MIE region, which replaces either the leftwards-oriented AAV REP gene of RCMV (Maastricht) or the upstream spliced portions of the immediate-early 2 gene (ie2) in MCMV. From the presence of other homologues of MCMV- and RCMV-specific genes, such as the beta-chemokine MCK-2, SGG1 and an Fcgamma receptor gene, as reported here, the basic architecture of the MIE region (reported previously) and the level of IE2 and DNA polymerase (POL) protein conservation in phylogenetic analyses, it is clear that the English strain of RCMV is also a member of the genus Muromegalovirus, but is a beta-herpesvirus species that is very distinct from both MCMV and RCMV (Maastricht). Both the lack of a CD200 homologue in the other two rodent viruses and the depth of sequence divergence of the rodent CMV IE2 and POL proteins suggest that these three viruses have evolved as separate species in the genus Muromegalovirus since very early in the host rodent lineage.

Animals↗

PubMed1998

Therapeutic ultrasound for osteoradionecrosis: an in vitro comparison between 1 MHz and 45 kHz machines.

Mandibular osteoradionecrosis is a serious chronic complication which may follow radiotherapy. Therapeutic ultrasound is a highly effective, inexpensive and readily available means of promoting revascularisation and healing. 'Long wave' ultrasound increases penetration depth and, therefore, seems to be more appropriate than traditional high frequency ultrasound. The aim of this study was to compare a new treatment using 45 kHz with the current standard 1 MHz machine. A traditional 1 MHz machine, pulsed 1:4, at intensities of 0.1, 0.4, 0.7 and 1.0 W/cm2(SAPA) was compared with a long wave machine, 45 kHz, at intensities of 5, 15, 30 and 50 mW/cm2(SA). The ultrasound was applied to human gingival fibroblasts and mandibular osteoblasts in vitro. Cell proliferation (DNA synthesis) and collagen and non-collagenous protein synthesis assays were performed, using radiolabelled thymidine and proline, respectively. Controls were sham-insonated and all readings were given as a percentage of controls. Fibroblast proliferation increased by 47% at 0.7 W/cm2 (1 MHz) and by 43% at 50 mW/cm2 (45 kHz), and osteoblast proliferation increased by 52% at 1.0 W/cm2 (1 MHz), and by 35% at 30 mW/cm2 (45 kHz). Fibroblast collagen production increased by 48% at 0.1 W/cm2 (1 MHz), and by 44% at 15 mW/cm2 (45 kHz) and osteoblast collagen production increased by 55% at 0.1 W/cm2 (1 MHz) and by 112% at 30 mW/cm2 (45 kHz). Long wave ultrasound was, therefore, capable of inducing a comparable or even higher enhancement of bone formation compared with traditional ultrasound, which, with its greater penetration, may accelerate the healing effect of ultrasound on osteoradionecrosis. The suggested intensity for 45 kHz ultrasound is 30 mW/cm2.

Cell Division↗

PubMed1997

Freud-Ferenczi: controversy terminable and interminable.

Following Balint's view that the psychoanalytic community was traumatised by the Freud-Ferenczi controversy, the author considers whether the roots of the confrontation between drive-based and object-relations theories might lie in a failure to examine this disagreement in sufficient depth. Increasing interest, as reflected in the literature, is now focusing on Ferenczi's ideas after many years of neglect due in part to Jones's 'official' account of the 'mental deterioration' of his last years. Adducing late works by both Freud and Ferenczi, the author shows that the latter amplified Freud's ideas rather than breaking with them. To Freud, who had always been concerned to stress the role of the drives in psychopathology, Ferenczi's emphasis on external trauma smacked of his own, rejected, early seduction theory, but trauma does feature prominently in Freud's discussion of interminable analyses, as does Ferenczi himself. In the author's view, a careful reading of the two men's late works reveals a conception of trauma as lying in an intersubjective space as a consequence of the meeting of drive and object. Present-day conceptions of transgenerational trauma are shown to be already present in Ferenczi. The problems in the relationship between Freud and Ferenczi and their theoretical disagreements are also considered in the light of the latter's inadequate analysis with Freud.

Austria↗

PubMed1993

Vertical fixation disparity in learning disabled.

In this correlation study of visual parameters as related to learning disabilities, we considered several deficits: uncorrected refractive error, accommodative infacility, inaccurate pursuits, and vertical fixation disparity. Because vision is the primary sensory input involved in reading, it is nothing new to find a correlation between visual deficits and learning problems; however, vertical fixation disparity, unique in its relation to other sensory systems, deserves a great deal of attention. The high incidence of vertical fixation disparity measured in 5th and 6th graders with learning disabilities suggests that there is a plausible causal relation. Vertical oculomotor imbalance, vestibular problems, and learning disability are discussed.

Accommodation, Ocular↗

PubMed2004

Annotation of parasite genomes.

Genome annotation is the application of useful biological descriptions to sequence data. Different levels of time and effort can be invested to produce correspondingly different depths of annotation depending on what methods are employed. Researchers using genome data should, therefore, understand how annotations are generated to assess their validity correctly and to determine what level of inferences can be made accordingly. Thorough annotation requires a large range of procedures, most of which involve manual reviews of all available evidence. First, gene structures often are computed algorithmically and edited based on in-depth analyses of the underlying sequence data. Second, functional predictions draw on data from various sources. Finally, the use of structured and controlled descriptions, such as those provided by gene ontology, can be used so that final descriptions are not only consistent and unambiguous, but capable of being used in further downstream analyses such as cross-species comparisons.

Algorithms↗

PubMed2003

Associations between periodontal disease and risk for nosocomial bacterial pneumonia and chronic obstructive pulmonary disease. A systematic review.

BACKGROUND: Several recent studies provide evidence that the oral cavity may influence the initiation and/or the progression of lung diseases such as pneumonia and chronic obstructive pulmonary disease (COPD). RATIONALE: Studies have shown that poor oral hygiene and periodontal disease may foster colonization of the oropharyngeal region by respiratory pathogens, particularly in hospital or nursing home patients. If aspirated, these pathogens can cause pneumonia, one of the most common respiratory infections, especially in institutionalized subjects. Other cross-sectional epidemiologic studies point to an association between periodontal disease and COPD. This systematic review examines the literature to determine if interventions that improve oral hygiene reduce the rate of pneumonia in high-risk populations. FOCUSED QUESTION: Do periodontal diseases or other indicators of poor oral health influence the initiation/progression of pneumonia or other lung diseases? SEARCH PROTOCOL: MEDLINE, pre-MEDLINE, MEDLINE Daily Update, and the Cochrane Controlled Trials Register were searched to identify published studies that related variables associated with pneumonia and other lung disease to periodontal disease. Searches were performed for articles published in English from 1966 through March 2002. INCLUSION CRITERIA: Randomized controlled clinical trials (RCTs), longitudinal, cohort, and case-control studies were included. Study populations included patients with any form of pneumonia or chronic obstructive pulmonary disease (COPD) and periodontal disease, as measured by assessments of gingival inflammation, probing depth, clinical attachment level, and/or radiographic bone loss, or oral hygiene indices. EXCLUSION CRITERIA: Limited to studies of humans. DATA COLLECTION AND ANALYSIS: The summary statistics used to analyze the RCTs included weighted mean differences in rates of disease between control and intervention groups. For cohort studies that measured differences in rates of disease between groups with and without oral disease, weighted mean differences, relative risks, or odds ratios were compared. A meta-analysis was performed on the 5 intervention studies to determine the relationship between oral hygiene intervention and rate of pneumonia in institutionalized patients. MAIN RESULTS: Of the initial 1,688 studies identified, 36 satisfied all inclusion criteria and were read. Of these, 21 (11 case-control and cohort studies [study population 1,413] and 9 RCTs [study population 1,759]) were included in the analysis. 1. A variety of oral interventions improving oral hygiene through mechanical and/or topical chemical disinfection or antibiotics reduced the incidence of nosocomial pneumonia by an average of 40%. 2. Several studies demonstrated a potential association between periodontal disease and COPD. REVIEWERS' CONCLUSIONS: 1. Oral colonization by respiratory pathogens, fostered by poor oral hygiene and periodontal diseases, appears to be associated with nosocomial pneumonia. 2. Additional large-scale RCTs are warranted to provide the medical community with further evidence to institute effective oral hygiene procedures in high-risk patients to prevent nosocomial pneumonia. 3. The results associating periodontal disease and COPD are preliminary and large-scale longitudinal and epidemiologic and RCTs are needed.

Consensus↗

PubMed2002

Assessment of applanation tonometry after hyperopic laser in situ keratomileusis.

PURPOSE: To determine the reliability and identify pitfalls in intraocular pressure measurement by Goldmann applanation tonometry after hyperopic laser in situ keratomileusis (LASIK). METHODS: Prospective non-masked case series at University of Valencia, Faculty of Medicine and Rahhal Ophthalmology Clinic, Valencia, Spain. One hundred three patients (103 eyes) treated with hyperopic LASIK were evaluated. The main treatment was hyperopic LASIK using a microkeratome Chiron Hansatome (Chiron Vision Corp, Claremont, CA) and the excimer laser Chiron Technolas 217-C LASIK (Chiron Technolas GmbH, Dornack; Germany). Central Goldmann applanation tonometric readings before surgery and 1, 3, and 6 months after surgery were analyzed. RESULTS: After hyperopic LASIK, a significant decrease in intraocular pressure was observed in the postoperative controls. In the low hyperopia patients (range: 1.00-3.00 D) a decrease of 2.43 mmHg was observed at the 6-month follow-up (p < 0.001). In the moderate hyperopia group (range: 3.25-6.00 D) a decrease of 2.05 mmHg was observed at the 6-month follow-up (p < 0.001). There were no significant differences between low and moderate hyperopia (p = 0.812). There was no statistically significant correlation between the magnitude of decrease in tonometry and gender, age, treated spherical equivalent, pachymetry, and anterior chamber depth (ACD). CONCLUSIONS: This clinical study displays that postoperative tonometry after hyperopic LASIK was significantly lower than the preoperative, hence modifying the reliability of Goldmann tonometry, and causing an intraocular pressure underestimation. A correcting factor should be applied when using applanation tonometry to measure postoperative intraocular pressure in patients who have undergone hyperopic LASIK.

Adult↗

PubMed2026

An alignment-free strategy for circulating tumor DNA detection and tumor fraction estimation from whole-genome sequencing data.

Circulating tumor DNA (ctDNA) is emerging as a promising biomarker for postoperative monitoring of cancer patients. Precise estimation of circulating tumor fraction is crucial for evaluating treatment effects and timely detection of disease recurrence. All current ctDNA detection methods that utilize whole-genome sequencing (WGS) data rely on the reference genome alignment of sequencing reads and often apply separate tools for detecting different variant types. However, various bioinformatic analysis confounders and the application of external variant calling tools could be avoided by analyzing k-mers from unaligned sequencing reads. While k-mer-based methods have successfully been applied for somatic variant validation and detection, the potential of k-mer-based ctDNA detection is unexplored. We have developed a tumor-informed alignment-free ctDNA detection tool called ctDNAmer that detects tumor-specific somatic variation directly from unaligned sequencing data by identifying k-mers unique to the tumor DNA. ctDNAmer detects variant information across the genome by comparing the primary tumor and germline WGS data and accounts for sample-specific germline variability and technical noise in the same framework. We tested the utility of ctDNAmer for tumor fraction estimation on postoperative plasma cfDNA WGS data (mean sequencing depth ~ 28x) from 90 stage III colorectal cancer patients with three years of follow-up. The tumor fraction (TF) estimates agreed with the available clinical information and ctDNA was detected in 77% (17/22) of recurring patients with a median lead time of 8 months compared to radiological imaging. We further validated ctDNAmer's tumor fraction estimates based on a comparison with the mean cfDNA allele frequencies of somatic clonal SNVs identified from aligned primary tumor sequencing data. The TF estimates showed a strong Pearson correlation of 0.897 with the mean allele frequencies and improved ctDNA detection results across samples with an AUC of 0.79 compared to 0.75 if the mean allele frequency of clonal mutations is used.

Circulating Tumor DNA↗

PubMed2002

Coiling of lumbar epidural catheters.

BACKGROUND: The difficulties in threading an epidural catheter to vertebral levels remote to the puncture level have been well documented. This study was undertaken to determine the length that a single orifice epidural catheter can be threaded into the lumbar space without coiling (coiling length), and whether this is affected by the direction of the epidural needle bevel. METHODS: Forty-five young male patients scheduled for surgery under epidural analgesia were enrolled. The epidural space was identified using a midline approach at the L(2-3) or L(3-4) interspace with the loss of resistance to air technique. A 19-G single-orifice epidural catheter (Flextip Plus, Arrow International, Inc, Reading, PA, USA) was inserted through a Tuohy needle oriented either cephalad (n=20) or caudad (n=25). During insertion, the path and the position of the catheter tip was determined by fluoroscopy using iohexol dye. RESULTS: The median coiling length was 2.8 cm, ranging from 1.0 to 8.0 cm. Only 13% of epidural catheters could be threaded 4 cm beyond the tip of the needle without coiling. No significant difference was found in coiling length between the cephalad group (2.9 cm) and the caudad group (2.5 cm). CONCLUSION: This study demonstrates that coiling length is independent of whether the bevel of the Tuohy needle is directed cephalad or caudad. We recommend that an optimal insertion depth of an end-hole single orifice catheter is 3 cm.

Adult↗

PubMedDate not supplied

[Mensurement of airflow resistance in neonatal prongs of nasal CPAP]

OBJECTIVE: To measure airflow resistance in prongs of nasal CPAP, making use of different gas admission flow (GAF) in the ventilation circuit, in different internal diameters of the nasal prongs, besides verifying whether a GAF responding only to the demand of three times the minute-volume(MV) is enough to the circuit not to be cause of CO(2) retention. METHODOLOGY: Nasal prongs, assembled in the original circuits, were used, having their prongs kept open to the atmosphere. Pressure was read at a pressure monitor, in water centimeters, connected to the appropriate entrance of the circuit. A flowmeter balanced to the pressure was used, gauged at 50 psi, installed to the oxygen net of the Hospital, connected to the assessing set of the CPAP circuit. Initially, making use of the 8 l/min flow and keeping the exhaling set of the circuit closed, it was possible to eliminate the nasal prongs larger than two once the measured resistance was equal to zero. Having nasal parts number zero, 1 and 2 selected for this study, the system was then assembled as for the neonate: the inhaling set to the gas source and the exhaling set sunk into different depths in the water seal (2, 4, 6 and 8 centimeters). At the level of patient analysis, in order to assess the CO(2) retention, a mechanical pulmonary ventilation device was used as gas source and a nasal CPAP circuit was assembled to the device in adequate places. GAF values and FiO(2) were determined in the commands of the mechanical ventilation device. The assessment of gas concentration in the ventilation circuit was made while assisting two newborns. Gas samples were obtained within the ventilation circuit in the system assessing set (samples A), and right after the distal prong to the gas entrance (samples B). To determine MV the Tidal Volume (considered 10ml/kg) was multiplied by the respiratory frequency of the patient; GAF was three times MV. RESULTS: To a maximum GAF of 8 litres/min, only prongs sized zero, 1 and 2 showed resistance to the flow, measurable by the method used. There was an increase in resistance in proportion to the raise of GAF and proportionally opposite to the internal diameter of some prongs. Maximum difference in CO(2) partial pressure obtained from the gas given to the ventilation circuit and the one obtained from the nasal prongs was, in average, 0.43mmHg (p <0.5). CONCLUSIONS: Taking into account that during ventilation assistance through nasal CPAP there is the possibility of GAF incurring in the increase in resistance, what would involve a greater effort from the newborn to overcome such resistance during exhaling into the system (generating possibly an unexpected CPAP), and minimum GAF determined is that sufficient to meet no more than three times the MV, the conclusion is that prongs with the largest internal diameter possible and GAF only the necessary to meet, at least, the needs of the demand three times the MV should be used during this therapeutic procedure.

Journal Article↗

PubMedDate not supplied

Curing of pit & fissure sealants using Light Emitting Diode curing units.

Light Emitting Diode (LED) curing units are attractive to clinicians, because most are cordless and should create less heat within tooth structure. However, questions about polymerization efficacy have surrounded this technology. This research evaluated the adequacy of the depth of cure of pit & fissure sealants provided by LED curing units. Optilux (OP) and Elipar Highlight (HL) high intensity halogen and Astralis 5 (A5) conventional halogen lights were used for comparison. The Light Emitting Diode (LED) curing units were Allegro (AL), LE Demetron I (DM), FreeLight (FL), UltraLume 2(UL), UltraLume 5 (UL5) and VersaLux (VX). Sealants used in the study were UltraSeal XT plus Clear (Uclr), Opaque (Uopq) and Teethmate F-1 Natural (Kclr) and Opaque (Kopq). Specimens were fabricated in a brass mold (2 mm thick x 6 mm diameter) and placed between two glass slides (n=5). Each specimen was cured from the top surface only. One hour after curing, four Knoop Hardness readings were made for each top and bottom surface at least 1 mm from the edge. The bottom to top (B/T) KHN ratio was calculated. Groups were fabricated with 20 and 40-second exposure times. In addition, a group using a 1 mm-thick mold was fabricated using an exposure time of 20 seconds. Differences between lights for each material at each testing condition were determined using one-way ANOVA and Student-Newman-Keuls Post-hoc test (alpha=0.05). There was no statistical difference between light curing units for Uclr cured in a 1-mm thickness for 20 seconds or cured in a 2 mm-thickness for 40 seconds. All other materials and conditions showed differences between light curing units. Both opaque materials showed significant variations in B/T KHN ratios dependent upon the light-curing unit.

Dental Restoration, Permanent↗

PubMed2005

An analysis of an implantable dosimeter system for external beam therapy.

BACKGROUND AND PURPOSE: To review the data from an implantable radiation dosimetry system used in a clinical setting and to examine correlations between dosimeter readings and potential causative error sources. MATERIALS AND METHODS: MOSFET (metal oxide semiconductor field effect transistor) based encapsulated dosimeters were evaluated in a phantom (in vitro) and in a study with 18 patients. The dosimeters were placed in the gross tumor volume or in collateral normal tissue. Predicted dose values were established by imaging the dosimeters in the planning CTs. RESULTS: The in vitro study confirmed that bounding cumulative errors due to setup, planning, and machine output within a +/-5% level is achievable. In patients, it was found that deviations from the targeted dose often exceeded the 5% level. CONCLUSIONS: The use of an implantable dosimeter system could provide an effective empiric check on the dose delivered at depth. Such a tool may have value for institutional quality assurance, as well as for therapy delivered to individual patients.

Dose-Response Relationship, Radiation↗

PubMed2002

Dis/integrated care: family caregivers and in-hospital respite care.

AIM: The aim of this study was to explore family caregivers' experiences of in-hospital respite care for people with dementia and the factors that influenced their perceptions of the service. BACKGROUND: The provision of respite care is based on the assumption that temporary relief from caregiving will relieve caregiver stress and may possibly extend the duration of home care. Research evidence suggests that this is a simplistic perspective which fails to account for families' concerns about the quality of institutional care and the impact of relocation on the person being cared for. DESIGN: Nine family caregivers, using four different hospitals sites were interviewed during a period of 3 years from 1994 to 1997. The research texts were analysed using a critical discourse analysis approach drawing on the work of Foucault. FINDINGS: Family caregiver texts were distinguished by difference rather than by homogeneity. Caregivers occupied a range of positions in terms of their ability to take advantage of the respite time intermittent care offered. My reading of these texts has highlighted the aspects of nurse-family relationships that ameliorated, or alternately exacerbated, the tensions felt by caregivers, as they were torn between the necessity to have a break and their anxieties about the impact of in-hospital respite care on the person with dementia. CONCLUSION: Nurses' practices in this study were a critical element in facilitating, or alternately constraining, family caregivers' ability to relinquish care and to take full advantage of the respite time. The research findings highlight the need for nurses and other formal caregivers to locate themselves in a secondary and supporting caregiving role, to acknowledge the family caregivers as the primary caregiver, and use family caregivers in-depth and intimate knowledge of the needs of their relative to inform care within the institutional setting.

Adult↗

PubMed1994

Electrical impedance compared with other non-invasive bioengineering techniques and visual scoring for detection of irritation in human skin.

A new, non-invasive device, which enables local measurements of electrical impedance to a controlled depth, has been used to evaluate the degree of irritation in human skin. The results have been compared with those obtained using other non-invasive techniques, i.e. with transepidermal water loss (TEWL), electrical capacitance moist measurement (ECM), laser-Doppler flowmetry (LDF), and visual scoring. Sodium lauryl sulphate solutions (0.1-5.0%), and a blank, were applied in Finn Chambers for 24 h on the volar forearm of 10 healthy volunteers. Values were recorded before application of the test chambers, and at 1 h, 24 h, 1 week and 2 weeks after removal. Thus, both the degree of initial damage and the healing process were monitored. There was close agreement among values obtained using electrical impedance, TEWL and visual readings. Results obtained using ECM and LDF were not consistent with the other three methods. In evaluating irritation of the skin, the practical situation may influence the choice of bioengineering tools. In most circumstances, a combination of methods would be preferable.

Adult↗

PubMed1992

Evaluation of alternative techniques to determine pork carcass value.

Three techniques for estimating the value of pork carcasses were evaluated: an optical probe, a real-time ultrasound scanner, and an electromagnetic scanner (EMSCAN). The ability of these techniques to predict carcass value was compared to the predictive ability of actual measures of backfat depth and longissimus muscle area taken with a ruler and a dot grid. Results indicated the EMSCAN model was the best predictor of carcass value. However, the optical probe, ultrasound, and the ruler/dot grid all provided information not contained in the EMSCAN model. The choice among ultrasound, the optical probe, and the ruler/dot grid depends on how the carcass will be used. There is no significant difference between ultrasound and the ruler/dot grid or the optical probe and the ruler/dot grid if the carcass is to be marketed in wholesale primal form, but the ruler/dot grid is superior if the ham and loin are to be sold as lean, boneless products. A model combining the EMSCAN and optical probe readings provided more accurate value predictions than either technique alone. A carcass value matrix for use in pricing pork carcasses was developed using readings from the optical probe. Carcass use has a substantial impact on value differences between fat and lean pigs.

Adipose Tissue↗

PubMed2001

Design, construction, and performance of an asymmetrical collimator for a cobalt unit.

PURPOSE: Besides four linear accelerators, our institute has a 100-cm SAD cobalt unit which has some specific and useful features for radiotherapy. The unit is equipped with a electronic portal imaging device (EPID) and an asymmetrical collimator to perform similar treatment techniques as on the linear accelerators, using the same shielding and half-beam techniques. The design, construction, and performance of the asymmetrical collimator are described. METHODS AND MATERIALS: The new design includes the doubling of the drive and read-outs for both X and Y jaws. Spare parts of the standard collimator provided by the manufacturer were used as much as possible. Special trimmers were designed to allow asymmetry to the center of the field. The trimmers are removable, but the design allows the use of trimmers, wedges, and shadow tray simultaneously. RESULTS: Transmission through the trimmers is less than 5% of the dose at d(max). The use of the trimmers extends the source to diaphragm distance to 53 cm, resulting in a smaller penumbra as compared to the standard collimator. Without the trimmers, the maximum field size remains unchanged, i.e., 40 x 40 cm(2); with the trimmers, it is 38 x 36 cm(2). Percentage depth doses and output factors were similar to the standard collimator. CONCLUSION: The modified collimator is compact and allows use of the same shielding blocks as the linear accelerators, providing the same treatment techniques and capabilities. This simplifies an exchange of patients between our treatment machines.

Cobalt Radioisotopes↗

PubMed1992

Effects of age-related reductions in processing resources on text recall.

Available processing resources are presumed to determine the amount of deep, elaborative processing people can carry out, with reduced resources resulting in poor integration of details from texts, but preserved selection of main points. Two experiments examined whether experimentally reducing resources and levels of processing eventually results in a failure of selection and also whether it produces in younger people the pattern of recall normally observed in elderly people. Experiment 1 examined the effect of the added demand of selecting for preferential recall of a primary theme from a two-theme text. Subjects who putatively had greater processing resources ("younger" elderly in their 60s and those with high intelligence test scores) began to behave like older and lower intelligence test score individuals in that they recalled well main points from both themes but showed reduced recall of details from the secondary theme. In a sentence recognition task, subjects in their 70s more often accepted distractor sentences that did not preserve the meaning of the original text. In Experiment 2, encouraging subjects to process text more elaborately improved recall, especially the recall of the elderly, who began to produce recall protocols resembling those of younger and higher intelligence test score individuals. However, discouraging depth of processing did not have the converse effect of reducing quality of recall by younger and high intelligence test score individuals to resemble that of the old and less able. Instead, recall was generally depressed, with recall of main points being especially affected, suggesting that the oldest, lowest ability subjects were beginning to show a failure of selection here.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed2006

Analysis of the kinestatic charge detection system as a high detective quantum efficiency electronic portal imaging device.

Megavoltage x-ray imaging suffers from reduced image quality due to low differential x-ray attenuation and large Compton scatter compared with kilovoltage imaging. Notwithstanding this, electronic portal imaging devices (EPIDs) are now widely used in portal verification in radiotherapy as they offer significant advantages over film, including immediate digital imaging and superior contrast range. However video-camera-based EPIDs (VEPIDs) are limited by problems of low light collection efficiency and significant light scatter, leading to reduced contrast and spatial resolution. Indirect and direct detection-based flat-panel EPIDs have been developed to overcome these limitations. While flat-panel image quality has been reported to exceed that achieved with portal film, these systems have detective quantum efficiency (DQE) limited by the thin detection medium and are sensitive to radiation damage to peripheral read-out electronics. An alternative technology for high-quality portal imaging is presented here: kinesatic charge detection (KCD). The KCD is a scanning tri-electrode ion-chamber containing high-pressure noble gas (xenon at 100 atm) used in conjunction with a strip-collimated photon beam. The chamber is scanned across the patient, and an external electric field is used to regulate the cation drift velocity. By matching the scanning velocity with that of the cation (i.e., ion) drift velocity, the cations remain static in the object frame of reference, allowing temporal integration of the signal. The KCD offers several advantages as a portal imaging system. It has a thick detector geometry with an active detection depth of 6.1 cm, compared to the sub-millimeter thickness of the phosphor layer in conventional phosphor screens, leading to an order of magnitude advantage in quantum efficiency (>0.3). The unique principle of and the use of the scanning strip-collimated x-ray beam provide further integration of charges in time, reduced scatter, and a significantly reduced imaging dose, enhancing the imaging signal-to-noise ratio (SNR) and leading to high DQE. While thick detectors usually suffer from reduced spatial resolution, the KCD provides good spatial resolution due to high gas pressure that limits the spread of scattered electrons, and a strip-collimated beam that significantly reduces the inclusion of scatter in the imaging signal. A 10 cm wide small-field-of-view (SFOV) prototype of the KCD is presented with a complete analysis of its imaging performance. Measurements of modulation transfer function (MTF), noise power spectrum (NPS), and DQE were in good agreement with Monte Carlo simulations. Imaging signal loss from recombination within the KCD chamber was measured at different gas pressures, ion drift velocities, and strip-collimation widths. Image quality for the prototype KCD was also observed with anthropomorphic phantom imaging in comparison with various commercial and research portal imaging systems, including VEPID, flat-panel imager, and conventional and high contrast film systems. KCD-based imaging provided very good contrast and good spatial resolution at very low imaging dose (0.1 cGy per image). For the prototype KCD, measurements yielded DQE(0)=0.19 and DQE(1 cy/mm)=0.004.

Computer-Aided Design↗