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PubMed1994

Two-dimensional random arrays for real time volumetric imaging.

Two-dimensional arrays are necessary for a variety of ultrasonic imaging techniques, including elevation focusing, 2-D phase aberration correction, and real time volumetric imaging. In order to reduce system cost and complexity, sparse 2-D arrays have been considered with element geometries selected ad hoc, by algorithm, or by random process. Two random sparse array geometries and a sparse array with a Mills cross receive pattern were simulated and compared to a fully sampled aperture with the same overall dimensions. The sparse arrays were designed to the constraints of the Duke University real time volumetric imaging system, which employs a wide transmit beam and receive mode parallel processing to increase image frame rate. Depth-of-field comparisons were made from simulated on-axis and off-axis beamplots at ranges from 30 to 160 mm for both coaxial and offset transmit and receive beams. A random array with Gaussian distribution of transmitters and uniform distribution of receivers was found to have better resolution and depth-of-field than both a Mills cross array and a random array with uniform distribution of both transmit and receive elements. The Gaussian random array was constructed and experimental system response measurements were made at several ranges. Comparisons of B-scan images of a tissue mimicking phantom show improvement in resolution and depth-of-field consistent with simulation results.

Ultrasonography↗
PubMed1987

Health care technology and quality of care.

The increasing costs and complexity of technologic advances in diagnosis and treatment have been accompanied by other important issues. They are often moral or ethical in nature; they include the public's desire and determination to have access to these "high-tech" advances; and the quality and equity with which those advances are apportioned and applied must be addressed. Seven criteria that can be applied to technology assessment are identified as is a process for that assessment. Together, these procedures can provide valuable information and assistance to those who make decisions about health benefits coverage--both in the public and the private sectors.

Blue Cross Blue Shield Insurance Plans↗
PubMed1993

Application of the FOCUS-PDCA model to home care equipment management.

Issuing durable medical equipment to patients for use at home is a costly and complex process. Selection, delivery, setup, and maintenance of home care equipment and the education of patients in its use are currently included in Joint Commission on the Accreditation of Healthcare Organizations (JCAHO) accreditation surveys for those health care organizations that issue equipment. In this Department of Veterans Affairs teaching hospital, the process was complicated by eligibility regulations and frequently rotating housestaff. We organized a team who studied the process and identified opportunities for improvement in three areas: the selection of equipment items ordered, management of equipment-related data, and standardization of equipment delivery contracts. We produced a reference manual for staff, developed a simple database, and incorporated JCAHO home care equipment management standards into equipment delivery vendor contracts. The results of the team's efforts were an increase in efficiency, a decrease in discharge delays, and improved continuity of care. We chose to use the FOCUS-PDCA model to illustrate our approach to improving these processes.

Durable Medical Equipment↗
PubMed1992

Monitoring of waters intended for abstraction.

The National Rivers Authority (NRA) monitors rivers for many different purposes. Routine monitoring for specified national and international purposes only serves to categorize the water in the general sense and is unlikely to detect short term quality aberrations. Where rivers support potable abstractions additional monitoring may be required to supplement the more routine data collection. Experience on the River Dee which straddles the North Wales and English border indicates that it is possible to construct a monitoring system that offers a high degree of protection against adverse quality changes but that such protection is both costly and complex and cannot guarantee absolute protection against all foreseeable events. Improved pollution control, the establishment of catchment inventories and protection zone status for sensitive areas may be effective in reducing the risk further. Cooperative investment in monitoring by the NRA and the Water Companies is very effective although differing expectations and standards can produce problems.

England↗
PubMed2006

A review of methods to detect cases of severely malnourished children in the community for their admission into community-based therapeutic care programs.

BACKGROUND: The complexity and cost of measuring weight-for-height make it unsuitable for use by community-based volunteers. This has led community therapeutic care programs to adopt a two-stage screening and admission procedure in which mid-upper-arm circumference (MUAC) is used for referral and weight-for-height is used for admission. Such a procedure results in many individuals being referred for care on the basis of MUAC but subsequently being refused treatment because they do not meet the weight-for-height admission criterion. This "problem of rejected referrals" has proved to be a major barrier to program uptake. OBJECTIVE: To systematically review methods to detect cases of severely malnourished children in the community for their admission into community-based therapeutic care programs. METHODS: Clinical and anthropometric methods for case detection of severely malnourished children in the community were reviewed with regard to their ability to reflect both mortality risk and nutritional status. RESULTS: MUAC, with the addition of the presence of bipedal edema, was found to be the indicator best suited to screening and case detection of malnutrition in the community. The case definition "MUAC < 110 mm OR the presence of bipedal edema," with MUAC measured by a color-banded strap, is suitable for screening and case detection of malnutrition in the community for children aged between 6 and 59 months. Monitoring and discharge criteria were also reviewed. CONCLUSIONS: There is no compelling evidence to support a move away from using weight in combination with clinical criteria for monitoring and discharge.

Anthropometry↗
PubMed2006

Craniotomy using image-guided oscillating saw: technical note.

OBJECTIVE: To describe a new craniotomic technique that eliminates burr holes and minimizes bone loss along the craniotomic line. PATIENTS AND METHODS: Fifty burr hole free craniotomies were performed in varied locations using an image-guided micro-oscillating saw. Care was taken to avoid cutting the inner cortical layer. Upon completing the micro-oscillating saw cut the inner table could then be gently fractured along the craniotomic line with a thin bladed osteotome. Simple silk sutures were used to resecure the bone flap. RESULTS: The craniotomic time required for this procedure ranged from 7 to 24 minutes (mean: 13 minutes). We observed no dural lacerations or signs of brain damage in any of these procedures. The use of image guidance allows a continuous measure of bone thickness along the craniotomic line. In all of the cases we report the cosmetic result was excellent. CONCLUSION: This alternative technique of craniotomy can be used in selected cases to achieve excellent cosmetic results which avoid the time and cost of complex reconstruction techniques.

Adolescent↗
PubMed2006

The science behind 25 years of ovarian stimulation for in vitro fertilization.

To allow selection of embryos for transfer after in vitro fertilization, ovarian stimulation is usually carried out with exogenous gonadotropins. To compensate for changes induced by stimulation, GnRH analog cotreatment, oral contraceptive pretreatment, late follicular phase human chorionic gonadotropin, and luteal phase progesterone supplementation are usually added. These approaches render ovarian stimulation complex and costly. The stimulation of multiple follicular development disrupts the physiology of follicular development, with consequences for the oocyte, embryo, and endometrium. In recent years, recombinant gonadotropin preparations have become available, and novel stimulation protocols with less detrimental effects have been developed. In this article, the scientific background to current approaches to ovarian stimulation for in vitro fertilization is reviewed. After a brief discussion of the relevant aspect of ovarian physiology, the development, application, and consequences of ovarian stimulation strategies are reviewed in detail.

Aging↗
PubMed2003

Radioiodine treatment with 30 mCi after recombinant human thyrotropin stimulation in thyroid cancer: effectiveness for postsurgical remnants ablation and possible role of iodine content in L-thyroxine in the outcome of ablation.

The main steps in the management of differentiated thyroid cancer are thyroidectomy, treatment with iodine-131 ((131)I), and follow-up with whole-body scanning (WBS) and serum thyroglobulin (Tg) determination. Both (131)I treatment and follow-up require maximum stimulation of normal or pathological thyroid remnants by TSH. The use of recombinant human TSH (rhTSH) has been shown to be useful for follow-up, whereas previous reports are not univocal regarding the use of (131)I postsurgical ablation of thyroid remnants, at least when low doses (30 mCi) of (131)I are administered. A possible explanation for the diminished effectiveness of (131)I treatment after rhTSH may be the interference of iodine content of L-thyroxine (L-T4) therapy during the protocol of administration of rhTSH. We have evaluated the effectiveness of stimulation by rhTSH for radioiodine ablation of postsurgical remnants, stopping L-T4 the day before the first injection of rhTSH and restarting L-T4 the day after (131)I. The study included two groups of patients: group 1 included 16 patients with differentiated thyroid cancer (15 papillary cancers and 1 follicular cancer, stages I and II), who were treated with 30 mCi (131)I with the aid of rhTSH, using the standard protocol but stopping L-T4 as stated previously; and group 2 included 24 patients with the same features (histology and stage) of disease treated with 30 mCi in the hypothyroid state after L-T4 withdrawal. In both groups, serum TSH reached a very good stimulation level [76-210 U/liter (mean, 112 +/- 11 SE) and 38-82 U/liter (mean, 51 +/- 3 SE), respectively]. At the first WBS (after (131)I treatment), all patients showed thyroid remnants. Furthermore, two patients of the first group and three patients of the second group showed lymph node metastases. After 1 yr, all patients were studied again and underwent WBS with a tracer dose of (131)I and serum Tg measurement using rhTSH with the same protocol in both groups. The percentage of ablation (undetectable Tg and a negative WBS) was higher, although not reaching statistical significance, in patients treated with rhTSH: 81.2% in patients treated by rhTSH withdrawal and 75.0% in patients treated by L-T4 withdrawal, respectively. No patient experienced symptoms of hypothyroidism during the 4 d of L-T4 interruption, and serum T4 remained in the normal range. Urinary iodine was analyzed in both groups and compared with a control group of patients who received, for diagnostic purposes, rhTSH without stopping L-T4. In the first group, urinary iodine was 47.2 +/- 4.0 microg/liter (mean +/- SE; P = 0.21 vs. the second group, P = 0.019 vs. control group). In the second group, urinary iodine was 38.6 +/- 4.0 microg/liter (mean +/- SE; P < 0.001 vs. control group); urinary iodine in the control group was 76.4 +/- 9.3 microg/liter (mean +/- SE). Our data show that rhTSH, as administered in the protocol stated previously, allows at least the same rate of ablation of thyroid remnants when low doses (30 mCi) of (131)I are used. The possible role of interference of iodine content in L-T4 is not surprising if we consider that the amount of iodine in 30 mCi is negligible (5 microg) compared with the amount of iodine content in a daily dose of T(4) ( approximately 50 microg). The cost of rhTSH seems modest compared with the high cost of complex therapeutic regimens in other areas of oncology and in consideration of the well-being of patients and of the high level of effectiveness of the treatment.

Adult↗
PubMed2001

Neurological teleconsultation for general practitioners.

A neurology teleconsulting network was implemented between a university hospital in Lisbon and five nearby health centres. PCs equipped for videoconferencing were installed, connected by ISDN lines at 128 kbit/s. Fifty-three general practitioners (GPs) were surveyed. The survey showed that the GPs had difficulties in using computers, but they had definite intentions to use teleconsultation for neurology cases and 83% of the respondents stated that they would probably use the technique. During the study, 90 neurology teleconsultations took place over 55 weeks. The average consultation rate was 1.6 teleconsultations per week (SD 1.3, range 0-6). The conferences lasted 10-45 min. Longer teleconsultations were mainly due to technical difficulties in using computers on the part of users with a low level of computer literacy. The patients were 42 males and 46 females, with a mean age of 38 years (SD 20, range 1-84); two patients were discussed twice. The benefits consisted mainly of advice on patient medication, diagnosis and the prevention of unnecessary specialist consultations or laboratory examinations. Doctor-doctor teleconsultation allows the rapid resolution of queries which otherwise cause stress to patients and increase the cost and complexity of care.

Adolescent↗
PubMed1996

Prospective, longitudinal assessment of developmental neurotoxicity.

Methodological issues in the design of prospective, longitudinal studies of developmental neurotoxicity in humans are reviewed. A comprehensive assessment of potential confounding influences is important in these studies because inadequate assessment of confounders can threaten the validity of causal inferences drawn from the data. Potential confounders typically include demographic background variables, alcohol and smoking during pregnancy, the quality of parental stimulation, the child's age at test, and the examiner. Exposure to other substances is assessed where significant exposure is expected in the target population. In most studies, control variables even weakly related to outcome are included in all multivariate statistical analyses, and a toxic effect is inferred only if the effect of exposure is significant after controlling for the potential confounders. Once a neurotoxic effect has been identified, suspected mediating variables may be added to the analysis to examine underlying processes or mechanisms through which the exposure may impact on developmental outcome. Individual differences in vulnerability may be examined in terms of either an additive compensatory model or a synergistic "risk and resilience" approach. Failure to detect real effects (Type II error) is of particular concern in these studies because public policy considerations make it likely that negative findings will be interpreted to mean that the exposure is safe. Important sources of Type II error include inadequate representation of highly exposed individuals, overcontrol for confounders, and inappropriate correction for multiple comparisons. Given the high cost and complexity of prospective, longitudinal investigations, cross-sectional pilot studies focusing on highly exposed individuals can be valuable for the initial identification of salient domains of impairment.

Animals↗
PubMed2002

Signed-negabinary-arithmetic-based optical computing by use of a single liquid-crystal-display panel.

Based on the negabinary number representation, parallel one-step arithmetic operations (that is, addition and subtraction), logical operations, and matrix-vector multiplication on data have been optically implemented, by use of a two-dimensional spatial-encoding technique. For addition and subtraction, one of the operands in decimal form is converted into the unsigned negabinary form, whereas the other decimal number is represented in the signed negabinary form. The result of operation is obtained in the mixed negabinary form and is converted back into decimal. Matrix-vector multiplication for unsigned negabinary numbers is achieved through the convolution technique. Both of the operands for logical operation are converted to their signed negabinary forms. All operations are implemented by use of a unique optical architecture. The use of a single liquid-crystal-display panel to spatially encode the input data, operational kernels, and decoding masks have simplified the architecture as well as reduced the cost and complexity.

Journal Article↗
PubMed2003

Performance of an optical wireless communication system as a function of wavelength.

Optical wireless communication (OWC) is gaining acceptance in an increasing number of sectors of science and industry, owing to its unique combination of features: extremely high bandwidth, rapid deployment time, license- and tariff-free bandwidth allocation, and low power consumption, weight, and size. However, the major drawback of OWC in terrestrial applications is the threat of downtime caused by adverse weather conditions, such as fog and haze. Several researchers have proposed and developed communication systems that use far-IR radiation to mitigate weather effects. In this study we analyze the performance of a short-distance terrestrial OWC system as a function of wavelength. A mathematical model for OWC link performance is derived. Using this model, we perform a simulation of our system under different weather conditions. From the results of our calculations, the improvement of link availability for 10 microm compared with 0.785-1.55 microm for a distance of 1-km propagation is 0.2% (99.6-99.8%). This modest improvement should be considered relative to the complexity and cost of quantum cascade laser transmitters and far-IR receivers.

Journal Article↗
PubMed2005

Microholographic multilayer optical disk data storage.

Micrometer-sized reflection holograms can be written into a rapidly rotating homogeneous photopolymer disk at the focus of a high-numerical-aperture beam and its retroreflection to implement high-capacity multilayer digital data storage. This retroreflection is generated by an optical system with positive unity magnification to ensure passive alignment of the counterpropagating beam. Analysis reveals that the storage capacity and transfer rate of this bit-based holographic storage system compare favorably with traditional page-based systems but at a fraction of the system complexity and cost. The analysis is experimentally validated at 532 nm by writing and reading 12 layers of microholograms in a 125-microm photopolymer disk continuously rotating at 3600 rpm. The experimental results predict a capacity limit of 140 Gbytes in a millimeter-thick disk or over 1 Tbyte with the wavelength and numerical aperture of Blu-Ray.

Journal Article↗
PubMed2006

Defect-free switchable phase grating.

Liquid-crystal-filled polymer structure devices offer a very low cost switchable spatial phase modulator. The phase profile set by the polymer structure may be varied or switched on/off with an applied field. Defects have been observed in some devices giving rise to spurious diffraction peaks. Computational modeling of the liquid-crystal director profile suggests that these defects might be suppressed if the dimensions of the liquid-crystal region are small. Experimental measurements confirm that this approach is effective in controlling the defects. This provides a route to fabrication of low-cost switchable complex diffractive devices.

Journal Article↗
PubMed2001

Number of phase levels in a two-dimensional separable Talbot array illuminator.

The number of phase levels in a Talbot array illuminator (TAIL) is an important factor for estimation of practical fabrication complexity and cost. We show that the number of phase levels in a two-dimensional TAIL (2D-TAIL) has a simple relation to the prime number. When the output array is alternatively pi phase modulated, there are similar simple relations. These simple relations should be highly interesting for practical use. An experiment with the 2D-TAIL based on the joint-Talbot effect is given as well.

Journal Article↗
PubMed2007

4Pi microscopy with linear fluorescence excitation.

Practical 4Pi microscopy has so far exclusively relied on multiphoton excitation of fluorescence, because the nonlinear suppression of contributions from higher-order sidelobes was mandatory for unambiguous axial superresolution. We show that novel lenses of 74 degrees semiaperture angle enable biological 4Pi microscopy with regular one-photon fluorescence excitation, thus increasing the signal and reducing system complexity and cost. An axial resolution of 95 nm, corresponding to a more than fourfold improvement over confocal microscopy, is verified in the imaging of microtubules in mammalian cells.

Computer Simulation↗
PubMed2003

Remote detection of heated ethanol plumes by airborne passive Fourier transform infrared spectrometry.

Methodology is developed for the automated detection of heated plumes of ethanol vapor with airborne passive Fourier transform infrared spectrometry. Positioned in a fixed-wing aircraft in a downward-looking mode, the spectrometer is used to detect ground sources of ethanol vapor from an altitude of 2000-3000 ft. Challenges to the use of this approach for the routine detection of chemical plumes include (1) the presence of a constantly changing background radiance as the aircraft flies, (2) the cost and complexity of collecting the data needed to train the classification algorithms used in implementing the plume detection, and (3) the need for rapid interferogram scans to minimize the ground area viewed per scan. To address these challenges, this work couples a novel ground-based data collection and training protocol with the use of signal processing and pattern recognition methods based on short sections of the interferogram data collected by the spectrometer. In the data collection, heated plumes of ethanol vapor are released from a portable emission stack and viewed by the spectrometer from ground level against a synthetic background designed to simulate a terrestrial radiance source. Classifiers trained with these data are subsequently tested with airborne data collected over a period of 2.5 years. Two classifier architectures are compared in this work: support vector machines (SVM) and piecewise linear discriminant analysis (PLDA). When applied to the airborne test data, the SVM classifiers perform best, failing to detect ethanol in only 8% of the cases in which it is present. False detections occur at a rate of less than 0.5%. The classifier performs well in spite of differences between the backgrounds associated with the ground-based and airborne data collections and the instrumental drift arising from the long time span of the data collection. Further improvements in classification performance are judged to require increased sophistication in the ground-based data collection in order to provide a better match to the infrared backgrounds observed from the air.

Air Pollutants↗
PubMed2004

Multiplexed genetic analysis using an expanded genetic alphabet.

BACKGROUND: All states require some kind of testing for newborns, but the policies are far from standardized. In some states, newborn screening may include genetic tests for a wide range of targets, but the costs and complexities of the newer genetic tests inhibit expansion of newborn screening. We describe the development and technical evaluation of a multiplex platform that may foster increased newborn genetic screening. METHODS: MultiCode PLx involves three major steps: PCR, target-specific extension, and liquid chip decoding. Each step is performed in the same reaction vessel, and the test is completed in approximately 3 h. For site-specific labeling and room-temperature decoding, we use an additional base pair constructed from isoguanosine and isocytidine. We used the method to test for mutations within the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The developed test was performed manually and by automated liquid handling. Initially, 225 samples with a range of genotypes were tested retrospectively with the method. A prospective study used samples from >400 newborns. RESULTS: In the retrospective study, 99.1% of samples were correctly genotyped with no incorrect calls made. In the perspective study, 95% of the samples were correctly genotyped for all targets, and there were no incorrect calls. CONCLUSIONS: The unique genetic multiplexing platform was successfully able to test for 31 targets within the CFTR gene and provides accurate genotype assignments in a clinical setting.

Autoanalysis↗