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At least 865 records · Page 48Linked to original sources
PubMed2004

Wide-viewing projection-type integral imaging system with an embossed screen.

A projection-type integral imaging system with an embossed screen is proposed to realize a wide viewing angle for the reconstructed image. The embossed screen is designed for virtual integral imaging in a projection-type system. It can enhance the viewing angle by increasing the effective region for each elemental image. The experimental result that verifies the merit of the proposed method is presented.

Journal Article↗
PubMed2001

Pharmacophore modeling and three-dimensional database searching for drug design using catalyst.

Perceiving a pharmacophore is the first essential step towards understanding the interaction between a receptor and a ligand. Once a pharmacophore is established, a beneficial use of it is 3D database searching to retrieve novel compounds that would match the pharmacophore, without necessarily duplicating the topological features of known active compounds (hence remain independent of existing patents). As the 3D searching technology has evolved over the years, it has been effectively used for lead optimization, combinatorial library focusing, as well as virtual high-throughput screening. Clearly established as one of the successful computational tools in rational drug design, we present in this review article a brief history of the evolution of this technology and detailed algorithms of Catalyst, the latest 3D searching software to be released. We also provide brief summary of published successes with this technology, including two recent patent applications.

Animals↗
PubMed2004

Pharmacophore modeling and three dimensional database searching for drug design using catalyst: recent advances.

Perceiving a pharmacophore is the first essential step towards understanding the interaction between a receptor and a ligand. Once a pharmacophore is established, a beneficial use of it is 3D database searching to retrieve novel compounds that would match the pharmacophore. As the 3D searching technology has evolved over the years, it has been effectively used for lead optimization, combinatorial library focusing, as well as virtual high-throughput screening. This paper is an update to the original paper published in this journal earlier: Kurogi, Y, and Guner, O. F. "Pharmacophore Modeling and Three-Dimensional Database Searching for Drug Design Using Catalyst," in Current Medicinal Chemistry, 2001, 8(9), 1035-1055.

Animals↗
PubMed2005

Discovery of HIV-1 integrase inhibitors through a novel combination of ligand and structure-based drug design.

Over the past 10 years, classical computer-aided molecular design methods have not been frequently applied for the discovery of novel HIV-1 integrase (IN) inhibitors, due to the intrinsic challenges that this enzyme presents. Therefore, a novel approach that combines the chemical information of known integrase inhibitors with the enzyme's detailed 3D structure in a stepwise fashion is proposed: (I) use of a pharmacophore model (PM), which takes into account in a weighted fashion the chemical features of known ligands, in analogous manner to the to search the Maybridge and the NCI 3D databases; (II) drug-likeness optimization; (III) virtual high-throughput screening of the hits matching the PM query against 1QS4 wild-type IN structure using different Docking/Scoring combinations; (IV) visual inspection and selection of the hits in function of: binding free energies; binding mode type within the active site; retrieval among the best 20% hits in more than 6 Docking/Scoring protocols at the same time. This approach aims at a rational selection of new potential HIV-1 integrase inhibitors.

Computer Simulation↗
PubMed2005

Interaction field based and hologram based QSAR analysis of propafenone-type modulators of multidrug resistance.

Overexpression of membrane bound, ATP-dependent transport proteins is one of the predominant mechanisms leading to multiple drug resistance in tumor therapy as well as in the treatment of bacterial and fungal infections. In tumor therapy, P-glycoprotein (P-gp, ABCB1) is responsible for transport of a wide variety of natural product toxins out of tumor cells leading to decreased accumulation of cytotoxic drugs within the cells. Inhibition of P-gp thus gives rise to a resensitization of multidrug resistant tumor cells and represents a versatile approach for modulation of multidrug resistance. Within this paper, a set of propafenone-type inhibitors of P-gp were analyzed using both interaction field based methods such as CoMFA and CoMSIA and Hologram QSAR. With both methods, highly predictive models with q2-values>0.65 were obtained. Models using logP as additional descriptor generally yielded higher predictive power. On basis of unfavorable steric and favorable electrostatic and hydrophobic interaction fields, these models were able to explain all outlayers identified in previous Hansch-analyses. For HQSAR analysis, models with q2-values up to 0.72 were obtained. Positive influences were found for electron donating groups on the aromatic systems. Highly negative influences were found for diphenylalkylamine substituents, which is a further hint for steric hindrance. The models with highest predictive power were used for screening of a small virtual library. Synthesis and pharmacological testing of a sub set of this library showed that the external predictivity of the HQSAR models generally is lower than the internal one.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Actual colonoscopy: what are the risks of perforation?

Recent studies have suggested that virtual colonoscopy (VC) and actual colonoscopy (AC) have similar efficacy for detection of polyps >6 mm. However, procedural risks with emerging technology such as VC need to be assessed before widespread implementation. We propose to demonstrate complication rates after AC that can be used for a comparative benchmark in VC. From 1994 to 1999 all patients undergoing AC who sustained perforation that required operation were analyzed for the mortality and complications. There were 26,162 consecutive colonoscopies that required 21 operations for perforation. Of these 16,948 (65%) colonoscopies were diagnostic and 9,214 (35%) were therapeutic with 11 (0.06%) and 10 (0.11%) operations respectively. Overall risk for colonoscopic perforation that requires operation was one in 1,246 (one in 1,541 for diagnostic and one in 921 for therapeutic). Five perforations were oversewn, 15 were resected (five with stoma), and one was drained. One patient died. There were two reoperations. Mortality was 0.006 per cent (one in 16,948) for diagnostic and zero for therapeutic colonoscopy. Overall risk for perforation that requires operation or mortality after AC is low. Virtual colonoscopists who propose screening and subsequent therapeutic interventions need to report high volume without complications as the perforation rate requiring operation was one in 1,246.

Colon↗
PubMed2004

Generation of functional Cerec 3D occlusal surfaces: a comparison of two production methods relevant in practice.

The introduction of the Cerec 3D software (R 1500) promised the generation of functional occlusion points and proximal contacts on the basis of a 3-dimensional virtual model on the screen. The objective of this in vitro study was to check this claim in the simulated chairside production of a single tooth restoration. Furthermore, the differences both in conventional finishing and in ceramic glazing were to be determined. For the operator, the latter should simplify or shorten the intraoral finishing and polishing of the occlusal surface, or make it superfluous. To check the suitability of the two methods, these were compared with regard to their quality and the time required to perform them. Ten cavities on articulated models, representing real clinical cases, were each provided with two restorations. One was produced with the glazing method (group A), the other conventionally (group B). The Cerec 3D software, version R 1500, was used for designing the restoration. The restorations made from Vita Mark II ceramic blocks were finished with fine diamond instruments and polished with Sof-Lex disks when using the conventional method. In the alternative method, finishing was practically replaced by glazing the surface. The restorations were evaluated in the articulator, considering both the vertical relation at the incisal pin as well as the accurate position of the contact points. The study showed that functional rehabilitation was possible and no significant qualitative differences occurred in the methods. In this in vitro study, it was found that the glazing method reduced the time required by the operator by around 20% and indicates an improvement in quality. The results of this study promise simplification when the glazing method is used clinically.

Computer Simulation↗
PubMed2002

Virtual colonoscopy.

Computed axial colonography, usually called virtual colonoscopy, is a new diagnostic method potentially useful for investigating polyps and tumors of the colon and rectum. It uses spiral axial tomography data to build up images similar to those given by conventional colonoscopy, offering advantages in that it causes no adverse reactions, and is accepted well by patients, who do not need to be sedated. Reports to date show its sensitivity and specificity vary in identifying polyps in the colon, and there are still many problems with the new method, such as its cost, its learning curve, the identification of flat lesions, and detection of extracolonic abnormalities. There is a pressing need to establish the accuracy and cost-effectiveness of virtual colonoscopy as a screening method for colorectal tumors, and for post-polypectomy surveillance.

Journal Article↗
PubMedDate not supplied

[CT and MR virtual colonscopy: indications, limits and comparison with conventional colonscopy].

Virtual endoscopy is a new method for studying the colon; it consists in acquisition of CT and MR images and to elaborate them with a workstation, to create endoluminal vision as like as traditional colonscopy, permitting the complete exploration of colonic lumen, also with stenotic tumors. The analysis of the differences between CT and MR colography shows like these two techniques present both advantages and disadvantages, such as the impossibility to perform MR in patients with pace-maker or in claustrophobic patients and the impossibility to perform CT with iodated agents in patients with renal failure or with a story of adverse reactions. The increased use of these techniques is due to the high sensitivity of last-generation CT and MR machine, to the increased spatial resolution, to specific softwares for digital cleaning of colon, to the introduction of high-end workstations and to the possibility of computed assisted diagnosis (CAD). So, it is desiderable that the increasing spread of multidetector CT devices and the future technical innovations, should have the effect to increase culture and experience in various diagnostic centers about CT-colography, making possible the spreading of virtual endoscopy as a screening tool.

Colonography, Computed Tomographic↗
PubMed1998

Alternative methods of maternal weight adjustment in maternal serum screening for Down syndrome and neural tube defects.

Serum markers used in screening for Down syndrome and neural tube defects are often adjusted to take account of the effect of maternal weight on the marker levels. The standard adjustment procedure is based on a linear relationship between the marker concentration, expressed as the log of the multiple of the median (MOM), and maternal weight on a linear scale. It has been proposed that maternal weight adjustment may be better performed using a linear relationship between marker concentration expressed in MOM and the reciprocal of maternal weight. In a dataset of 8905 singleton pregnancies in white women without Down syndrome or neural tube defects we compared the two methods of weight adjustment and found that both were satisfactory and neither had an obvious advantage over the other. In the analysis it was noticed that hCG levels in very heavy women (> 120 kg) were higher than expected from the decreasing linear trend with maternal weight--a result that was statistically highly significant (p < 0.01) but for which we have no explanation. In screening it will have virtually no effect because the finding was restricted to only the 0.3 per cent of the heaviest women.

Biomarkers↗
PubMed2007

Critical illness VR rehabilitation device (X-VR-D): evaluation of the potential use for early clinical rehabilitation.

We present a new critical illness VR rehabilitation device (X-VR-D) that enables diversified self-training and is applicable early in the rehabilitation of severely injured or ill patients. The X-VR-D consists of a VR program delivering a virtual scene on a flat screen and simultaneously processing commands to a moving chair mounted on a motion system. Sitting in the moving chair and exposed to a virtual reality environment the device evokes anticipatory and reactive muscle contractions in trunk and extremities for postural control. In this study we tested the device in 10 healthy subjects to evaluate whether the enforced perturbations indeed evoke sufficient and reproducible EMG muscle activations. We found that particular fast roll and pitch movements evoke adequate trunk and leg muscle activity. Higher angular velocities and higher angles of inclination elicited broader EMG bursts and larger amplitudes. The muscle activation pattern was highly consistent between different subjects and although we found some habituation of EMG responses in consecutive training sessions, the general pattern was maintained and was predictable for specific movements. The habituation was characterized by more efficient muscle contractions and better muscle relaxation during the rest positions of the device. Furthermore we found that the addition of a virtual environment to the training session evoked more preparatory and anticipatory muscle activation than sessions without a virtual environment. We conclude that the X-VR-D is safe and effective to elicit consistent and reproducible muscle activity in trunk and leg muscles in healthy subjects and thus can be used as a training method.

Abdominal Muscles↗
PubMed2005

A retrospective evaluation of patient acceptance of computed tomography colonography ("virtual colonoscopy") in comparison with conventional colonoscopy in an average risk screening population.

PURPOSE: To evaluate patient acceptance of computed tomography (CT) colonography compared with conventional colonoscopy by means of a self-assessed questionnaire. MATERIAL AND METHODS: Four-hundred-and-one patients with valid address information from our patient collective were preselected. Patient acceptance was evaluated retrospectively using a self-assessed questionnaire. The patients underwent CT colonography in our institution using 4x or 16x multi-detector row (MDR) CT. Two-hundred-and-forty-six patients returned a completed questionnaire, 157 of these indicating that they had undergone both virtual and conventional colonoscopy. RESULTS: One-hundred-and-twenty (76.4%) of the 157 patients would undergo another CT colonography if necessary, while only 14 patients would not. One-hundred-and-sixteen (73.9%) patients favored the actual examination procedure of CT colonography (P<0.0001), while only 6.4% preferred the conventional method. Preparation prior to CT colonography was experienced as more convenient than preparation prior to conventional colonoscopy (52.2% versus 14%). CONCLUSION: CT colonography was preferred in terms of both preparation and the actual procedure itself.

Adult↗
PubMedDate not supplied

Percutaneous computer-assisted translaminar facet screw: an initial human cadaveric study.

BACKGROUND CONTEXT: Translaminar facet screws are a minimally invasive technique for posterior lumbar fixation with good success rates. Computer-assisted image navigation using virtual fluoroscopy allows multiple simultaneous screens in various planes to plan and drive spinal instrumentation. PURPOSE: This study evaluates the percutaneous placement of translaminar facet screws with the use of virtual fluoroscopy as an image guidance technique. STUDY DESIGN/SETTING: A human cadaveric study was performed with a percutaneous reference frame applied to the iliac crest. Ten translaminar facet screws were placed bilaterally at five levels. Anteroposterior and lateral images were used to navigate 4.0-mm screws through a percutaneous portal under virtual fluoroscopy. METHODS: An axial computed tomographic scan through the instrumented levels was obtained after the screws were placed. Screws were graded on entry, course through the lamina, and terminus. A grading system was devised to grade the course through the lamina. RESULTS: All 10 screw-entry points were judged optimal at the spinous process laminar junction. There were five Grade I breeches with less than 1/2 the screw through the lamina, and five Grade 0 screw placements with the screw contained completely within the lamina. The termination point was acceptable in five screws. The screws that began on the right and terminated on the left were all found to have grade II breakouts. No screws placed the spinal canal or exiting nerve root at risk. CONCLUSIONS: Virtual fluoroscopy provides significant assistance in percutaneous placement of translaminar facet screws and results in safe position of entry, lamina course, and terminus.

Bone Screws↗
PubMed2003

Virtual magnetic resonance colonography.

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques.

Colorectal Neoplasms↗
PubMed2000

Arbor 3D: an interactive environment for examining phylogenetic and taxonomic trees in multiple dimensions.

UNLABELLED: This paper examines a new technique for the visualization of and the interaction with trees, objects frequently used to convey hierarchical relationships in biological data. Motivated by the quality of 2D tree interaction, we adapt the planar tree-of-life metaphor to a virtual, semi-immersive 3D environment. A 3D environment extends the utility of this metaphor by allowing the user to view an entire data set in a single screen. Interrogation of the tree is implemented using 3D input devices. This real-time interrogation of the tree itself provides a quick means by which to qualitatively analyse the hierarchical data. In this paper, we describe the techniques underlying the implementation of such an environment. We conclude by considering the utility of tree metaphors as a basis for the representation of highly dimensional data sets. AVAILABILITY: Arbor3D (source code, a binary executable for SGI IRIX 6.4, Perl parsers, and sample Newick data files) are available via the Internet (http://xian.tamu.edu/Arbor3D/). Arbor3D can be displayed in "CAVE simulator" mode on an SGI workstation screen, or as an interactive virtual environment on a projection workbench. CONTACT: druths@rice.edu; echen@cs.rice.edu; leland@xian.tamu.edu

Classification↗
PubMed2003

Screening for lung cancer: the guidelines.

Although virtually all individuals with advanced lung cancer succumb to the disease, a substantial portion of individuals diagnosed at an earlier stage can be cured. This dichotomy has provoked interest in lung cancer screening. To date, randomized controlled trials of chest x-ray and sputum cytology have failed to demonstrate that screening with either modality decreases lung cancer mortality; neither of these technologies can be recommended. Early studies of lung cancer screening with low-dose CT (LDCT) appear promising; however, only data from observational studies are available. We recommend that individuals should only be screened with LDCT in the context of well-designed clinical trials.

Evidence-Based Medicine↗