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At least 199 records · Page 11Linked to original sources
PubMed2002

A DICOM-RT-based toolbox for the evaluation and verification of radiotherapy plans.

The verification of radiotherapy plans is an essential step in the treatment planning process. This is especially important for highly conformal and IMRT plans which produce non-intuitive fluence maps and complex 3D dose distributions. In this work we present a DICOM (Digital Imaging and Communication in Medicine) based toolbox, developed for the evaluation and the verification of radiotherapy treatment plans. The toolbox offers the possibility of importing treatment plans generated with different calculation algorithms and/or different optimization engines and evaluating dose distributions on an independent platform. Furthermore the radiotherapy set-up can be exported to the BEAM Monte Carlo code system for dose verification. This can be done by simulating the irradiation of the patient CT dataset or the irradiation of a software-generated water phantom. We show the application of some of the functions implemented in this toolbox for the evaluation and verification of an IMRT treatment of the head and neck region.

Algorithms↗
PubMed2006

Mitochondrial function and toxicity: role of B vitamins on the one-carbon transfer pathways.

The B vitamins are water-soluble vitamins that are required as coenzymes for reactions essential for cellular function. This review focuses on the essential role of vitamins in maintaining the one-carbon transfer cycles. Folate and choline are believed to be central methyl donors required for mitochondrial protein and nucleic acid synthesis through their active forms, 5-methyltetrahydrofolate and betaine, respectively. Cobalamin (B12) may assist methyltetrahydrofolate in the synthesis of methionine, a cysteine source for glutathione biosynthesis. Pyridoxal, pyridoxine and pyridoxamine (B6) seem to be involved in the regeneration of tetrahydrofolate into the active methyl-bearing form and in glutathione biosynthesis from homocysteine. Other roles of these vitamins that are relevant to mitochondrial functions will also be discussed. However these roles for B vitamins in cell function are mostly theoretically based and still require verification at the cellular level. For instance it is still not known what B vitamins are depleted by xenobiotic toxins or which cellular targets, metabolic pathways or molecular toxic mechanisms are prevented by B vitamins. This review covers the current state of knowledge and suggests where this research field is heading so as to better understand the role vitamin Bs play in cellular function and intermediary metabolism as well as molecular, cellular and clinical consequences of vitamin deficiency. The current experimental and clinical evidence that supplementation alleviates deficiency symptoms as well as the effectiveness of vitamins as antioxidants will also be reviewed.

Animals↗
PubMed1983

Misclassification probability of dental discrimination functions for sex determination.

Misclassification probability of dental discriminant functions for sexing American whites was evaluated using three verification procedures. These validation techniques involved sample resubstitution, jackknife classification, and use of a holdout sample. Resulting discriminant score distributions yielded correct classifications ranging between 65 and 81% depending upon the particular tooth combinations selected. Dental discriminant functions are applicable to forensic science cases if used with caution.

Dentition↗
PubMedDate not supplied

[Recommendations for the installation in the laboratory of metrological functions and corresponding documentation (Document B)].

In order to ensure the quality of analytical results, clinical laboratories shall have a perfect control of process and equipments of measurement. Therefore is recommended individualisation of metrological function, generally entrusted the quality manager. This quality manager will draw up a metrological traceability, verifications and confirmations, control of non conformities, follow-up and evaluation of metrological function.

Clinical Chemistry Tests↗
PubMed2001

Verifying loudness perception after hearing aid fitting.

During the verification phase of a hearing aid fitting, clinicians often want to assess the extent to which loudness perceptions for amplified sounds are similar to those typical of normal hearers. This type of verification calls for a criterion for "normal" loudness perception of sounds presented in a sound field. This research sought to answer several questions about the parameters of a valid "normal" criterion for a verification procedure using the Contour test of loudness perception. Loudness data were obtained from 30 listeners with normal hearing. Results indicated that a loudness growth function obtained with earphone listening is not an appropriate normative reference for hearing aid fitting verification. Instead, the normative data should be based on sound field listening. Results also indicated that the same normative function could be used to assess both unilateral and bilateral fittings. Further, it is likely that the same normative function can be used for most frequency responses that are likely to be used in feasible fittings. Finally, it was found that a previously published normative function obtained using an automated test procedure was not faithfully replicated using a carefully executed fully manual test procedure. We concluded that, until a replicable normative function is established, practitioners will need to generate their own local norms to perform postfitting verification of loudness normalization.

Adult↗
PubMed2006

Comparison of two-dimensional transmitted dose maps: evaluation of existing algorithms.

Composite analysis and the gamma function are often used to assess the agreement between a reference and an evaluated two-dimensional dose maps. The intent of the study is to compare advantages, disadvantages and limitations of dose evaluation tools reported in the literature. In addition, in order to improve the gamma function output, a "Signed Matrix" was introduced using the ratio of relative dose difference maps. Transmitted dose maps were acquired for a range of homogeneous phantoms using Extended Dose Range (EDR2) films and a Scanning Liquid Ionization Chamber Electronic Portal Imaging Device (SLIC-EPID). For inhomogeneous case, the transmitted dose maps were obtained from EDR2 films measurement and a Treatment Planning System (TPS). The corresponding dose maps were compared based on composite and gamma function algorithms. The results showed that the agreement between reference and evaluated dose maps for the composite analysis were generally greater than those obtained using the gamma function. For homogeneous phantom comparison, the difference between the agreeing fractions calculated using composite analysis and gamma function increases with the increase of phantom thickness for deltaD = 0.5% and 1%. For inhomogeneous cases, a significant difference (approximately 5% for deltaD = 1.5%) was observed between the percentage agreement as calculated by composite and gamma function techniques. The concept of the composite model is closer than gamma function to the idea of the two-dimensional dose verification protocol proposed originally by van Dyk. However, the composite model results only display the passed or failed regions in the dose maps. On the other hand, the gamma function provides continuos information by distinguishing the points within each region. The overdosed/underdosed regions (the ratio of reference and evaluated doses at a given point) and the direction of the misalignment can be recognized with the enhanced gamma map convolved with a "Signed Matrix".

Algorithms↗
PubMed1979

Energy cost of proofreading to increase fidelity of transfer ribonucleic acid aminoacylation.

The paradox of relatively error free function in biological systems composed of relatively error prone components has recently come under intensive investigation. In the case of tRNA aminoacylation, aminoacyl-tRNA synthetases were discovered to have a separate function that allows misacylated molecules to be hydrolyzed more rapidly than correctly acylated molecules. This additional function of the synthetases provides a proofreading or verification mechanism that is believed to improve significantly the overall accuracy of tRNA aminoacylation. In this paper we provide an explicit relationship between the accuracy achieved by proofreading and the energy cost. Experimental data available in the literature are examined in light of this relationship. The following are the principal conclusions from our study: (1) high-accuracy proofreading of tRNA aminoacylation has a high energy cost, as much as 100 times greater than indications from early experimental work; (2) the minimum net error derived in previous theoretical studies is never actually reached; (3) mechanisms in which misacylation and subsequent proofreading occur on the surface of the same synthetase molecule achieve a much higher accuracy than mechanisms in which these functions occur on the surface of different synthetase molecules.

Amino Acids↗
PubMed2005

Detection of the third heart sound using a tailored wavelet approach: method verification.

Heart sounds can be considered as mechanical fingerprints of myocardial function. The third heart sound normally occurs in children but disappears with maturation. The sound can also appear in patients with heart failure. The sound is characterised by its low-amplitude and low-frequency content, which makes it difficult to identify by the traditional use of the stethoscope. A wavelet-based method has recently been developed for detection of the third heart sound. This study investigated if the third heart sound could be identified in patients with heart failure using this detection method. The method was also compared with auscultation using conventional phonocardiography and with characterisation of the patients with echocardiography. In the first study, 87% of the third heart sounds were detected using the wavelet method, 12% were missed, and 6% were false positive. In study 2, the wavelet-detection method identified 87% of the patients using the third heart sound, and regular phonocardiography identified two (25%) of the subjects.

Adult↗
PubMed1988

[The Ammann test, attempt at electrophysiologic verification].

The Ammann filter test is a subjective method of differentiating functional amblyopia from the organic type. An attempt was made to verify this subjective method by means of visual evoked responses. Good correlation was found with the results described in the literature, obtained by psychophysical examination.

Amblyopia↗
PubMed1987

Regeneration of the eighth cranial nerve. II. Physiologic verification in the bullfrog.

Two experiments were performed to document the functional capacity of the regenerated eighth cranial nerve. In experiment 1, the eighth cranial nerve was sectioned preganglionically and allowed to regenerate in a group of bullfrogs with normal contralateral eighth nerve and labyrinth. Posture and reflex to lateral tilt were measured preoperatively and postoperatively for a minimum of 3 months. Similar measures were performed in a second group of bullfrogs in which the eighth nerve had been destroyed by ganglionectomy and in a third with peripheral labyrinthectomies. In experiment 2, the eighth nerve was sectioned and allowed to regenerate in bullfrogs in which the contralateral nerve had previously been destroyed. Posture and reflex to lateral tilt were measured as in experiment 1. Similar measures were performed in a group of bullfrogs that had undergone bilateral nerve destruction. Regeneration of the eighth cranial nerve in bullfrogs in both experiments was documented histologically by labeling the regenerated fibers with horseradish peroxidase (HRP). In both experiments, posture recovered completely only in the bullfrogs in which the eighth cranial nerve was allowed to regenerate. Reflex to lateral tilt recovered more rapidly in the bullfrogs with regenerated nerves than in any of the other bullfrogs.

Animals↗
PubMed1989

Methodologic approach for a large functional trauma registry.

The utility of a clinical trauma registry (TR) is directly related to the constituents of the data base and to the accuracy of the data, which is contingent on a carefully constructed data collection system. A TR was developed by traumatologists at a busy Level I trauma facility that predominantly receives patients having incurred blunt injury. Four dedicated data collectors gather the AP information within 24 to 48 hours after admission, with prompt Attending Surgical review for verification. Examples of data output prove this is a functional system. Using a careful methodologic approach for design and implementation, clinicians can create a large, functional trauma registry with many potential applications.

Data Collection↗
PubMed1986

A general model for the absorption of ultrasound by biological tissues and experimental verification.

In this paper, a closed-form expression is derived for the absorption of ultrasound by biological tissues. In this expression, the viscothermal and viscoelastic theories of relaxation processes are combined. Three relaxation time distribution functions are introduced, and it is assumed that each of these distributions can be described by an identical and simple hyperbolic function. Several simplifying assumptions had to be made to enable the experimental verification of the derived closed-form expression of the absorption coefficient. The simplified expression leaves two degrees of freedom and it was fitted to the experimental data obtained from homogenized beef liver. The model produced a considerably better fit to the data than other, more pragmatic models for the absorption coefficient as a function of frequency that could be found in the literature. Scattering in beef liver was estimated indirectly from the difference between attenuation in in vitro liver tissue as compared to absorption in a homogenate. The frequency dependence of the scattering coefficient could be described by a power law with a power of the order of 2. A comparable figure was found in direct backscattering measurements, performed at our laboratory with the same liver samples [Van den Aarssen et al., J. Acoust. Soc. Am. (to be published)]. A model for scattering recently proposed by Sehgal and Greenleaf [Ultrason. Imag. 6, 60-80 (1984)] was fitted to the scattering data as well. This latter model enabled the estimation of a maximum scatterer distance, which appeared to be of the order of 25 micron.

Animals↗
PubMed2004

Biometric verification with correlation filters.

Using biometrics for subject verification can significantly improve security over that of approaches based on passwords and personal identification numbers, both of which people tend to lose or forget. In biometric verification the system tries to match an input biometric (such as a fingerprint, face image, or iris image) to a stored biometric template. Thus correlation filter techniques are attractive candidates for the matching precision needed in biometric verification. In particular, advanced correlation filters, such as synthetic discriminant function filters, can offer very good matching performance in the presence of variability in these biometric images (e.g., facial expressions, illumination changes, etc.). We investigate the performance of advanced correlation filters for face, fingerprint, and iris biometric verification.

Journal Article↗
PubMed2002

rSNP_Guide: an integrated database-tools system for studying SNPs and site-directed mutations in transcription factor binding sites.

Since the human genome was sequenced in draft, single nucleotide polymorphism (SNP) analysis has become one of the keynote fields of bioinformatics. We have developed an integrated database-tools system, rSNP_Guide (http://wwwmgs.bionet.nsc.ru/mgs/systems/rsnp/), devoted to prediction of transcription factor (TF) binding sites, alterations of which could be associated with disease phenotype. By inputting data on alterations in DNA sequence and in DNA binding pattern of an unknown TF, rSNP_Guide searches for a known TF with alterations in the recognition score calculated on the basis of TF site's sequence and consistent with the input alterations in DNA binding to the unknown TF. Our system has been tested on many relationships between known TF sites and diseases, as well as on site-directed mutagenesis data. Experimental verification of rSNP_Guide system was made on functionally important SNPs in human TDO2and mouse K-ras genes. Additional examples of analysis are reported involving variants in the human gammaA-globin (HBG1), hsp70(HSPA1A), and Factor IX (F9) gene promoters.

Animals↗
PubMed1994

Recognition of regulatory regions in genomic sequences.

For the functional interpretation of genomic sequences, effective algorithms have to be developed that will recognize regions of specific function and thus will suggest experiments for their verification. As a first step, relevant data have to be collected in an appropriate database from which suitable training sets can be extracted. In this paper, I discuss the requirements for a database that collects information about regulatory DNA sequences and describe the structure and contents of such a database (TRANSFAC). This compiled information will serve as a basis for comprehensive analysis of sites that regulate transcription, e.g., by statistical methods. It will thus facilitate the recognition of regulatory genomic sequence information and the assignment of the corresponding regulators. Moreover, it will provide all relevant data about the regulating proteins which will allow to trace back transcriptional control cascades to their origin.

Algorithms↗
PubMed1998

Validation of computer systems: practical testing of a standard LIMS.

In recent years the introduction of computer systems for data handling in the pharmaceutical industry has increased. A standard LIMS (laboratory information management system) is software commercially available from different suppliers not only to facilitate data handling in laboratories but also to cover GMP-requirements. Computer systems introduced in GMP-areas of pharmaceutical companies have to be validated. For a standard LIMS, the general validation of the program is performed by the supplier. Nevertheless, the user is always required to cover all phases of a validation. The objective of this paper is to discuss suitable test procedures for the most critical functions of a standard LIMS needed during the verification step of the validation process.

Clinical Laboratory Information Systems↗
PubMed2003

Antibradycardia pacing in patients with congenital heart disease: experience with automatic threshold determination and output regulation (Autocapture).

AIMS: The purpose of this study was to reevaluate whether St Jude Medical's Autocapture algorithm (AC) with beat-to-beat capture confirmation, automatic pacing threshold determination and output adjustment can be applied to paced patients with congenital heart disease (CHD). METHODS AND RESULTS: 30 patients with CHD received a transvenous (group A: n=22) or epicardial (group B: n=8) single (n=7) or dual chamber (n=23) AC pacemaker for antibradycardia pacing. As a safe AC function is ensured only if a sufficient evoked response (ER) and a low lead polarization amplitude (LPA) are present, these parameters were reevaluated from 112 follow-up studies with respect to AC-function. In all but one transvenous system AC correctly functioned. AC was recommended in 5/8 patients with epicardial leads but correct AC function was preserved in only 3 patients. CONCLUSION: These data suggest that the application of the AC algorithm is safe in patients with CHD when transvenous leads are used. Whether appropriate AC function is possible with epicardial leads needs individual verification.

Adolescent↗
PubMed2001

Interaction of array of finite electrodes with layered biological tissue: effect of electrode size and configuration.

A hybrid scheme, combining image series and moment method has been utilized for the calculation of the intramuscular three-dimensional (3-D) current density (CD) distribution and potential field transcutaneously excited by an electrode array. The model permits one to study the effect of tissue electrical properties and electrode placement on the CD distribution. The isometric recruitment curve (IRC) of the muscle was used for parameter estimation and model verification, by comparison with experimentally obtained IRCs of functional electrical stimulation (FES)-activated quadriceps muscle of paraplegic subjects. Sensitivity of the calculated IRC to parameters such as tissue conductivity, electrode size, and configuration was verified. The resulting model demonstrated characteristic features that were similar to those of experimentally obtained data. The model IRCs were insensitive to the electrode size; however, the inclusion of the bone-fascia layer significantly increased the intramuscular CD and, consequently, increased the IRC slope. Of the different configurations studied, a four-electrode array proved advantageous because, in this case, the CD between the electrodes was more evenly distributed, providing better resistance to fatigue. However, due to the steeper linear portion of the IRC, this configuration suffered from a somewhat reduced controllability of the muscle.

Electric Conductivity↗