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PubMed1999

Computer copings for partial coverage.

Partial coverage posterior tooth preparations are very complex surfaces for computer surface digitization, computer design, and manufacture of ceramic copings. The aim of this study was therefore to determine whether the Computer Integrated Crown Reconstruction (Cicero) system was compatible with a proposed partial coverage preparation design and capable of producing ceramic copings. Posterior teeth were prepared for partial coverage copings with deep gingival chamfers in the proximal boxes and around the functional cusps (buccal of mandibular and lingual of maxillary posterior teeth). The nonfunctional cusps (lingual of mandibular and buccal of maxillary posterior teeth) were prepared with broad bevels following the inclined occlusal plane pattern. Optical impressions were taken of stone dies by means of a fast laser-line scanning method that measured the three-dimensional geometry of the partial coverage preparation. Computers digitized the images, and designed and produced the ceramic copings. The Cicero system digitized the partial coverage preparation surfaces precisely with a minor coefficient of variance of 0.2%. The accuracy of the surface digitization, the design, and the computer aided milling showed that the system was capable of producing partial coverage copings with a mean marginal gap of 74 microns. This value was obtained before optimizing the marginal fit by means of porcelain veneering. In summary, Cicero computer technology, i.e., surface digitization, coping design, and manufacture, was compatible with the described partial coverage preparations for posterior teeth.

Bicuspid↗
PubMed1998

Analog versus digital: extrapolating from electronics to neurobiology.

We review the pros and cons of analog and digital computation. We propose that computation that is most efficient in its use of resources is neither analog computation nor digital computation but, rather, a mixture of the two forms. For maximum efficiency, the information and information-processing resources of the hybrid form must be distributed over many wires, with an optimal signal-to-noise ratio per wire. Our results suggest that it is likely that the brain computes in a hybrid fashion and that an underappreciated and important reason for the efficiency of the human brain, which consumes only 12 W, is the hybrid and distributed nature of its architecture.

Artifacts↗
PubMed1982

Computer enhanced digital angiography.

A new computer image enhancement technique was employed on cardiac images of 10 dogs and 7 patients to demonstrate the feasibility of an on-line automatic delineation of the left ventricular endocardial silhouette with a peripheral venous injection of contrast material while simultaneously reducing the x-ray dosage. This technique employs a very fast analog-to-digital conversion system capable of digitizing on-line video frames. By storing and continuously updating the first 30 video frames and then subtracting each incoming frame from this memory, most of the background is eliminated leaving only the contrast filled ventricle. Using calibrated densitometric measurements, we found that iodine concentrations in the human left ventricle following venous injection of 40 ml Renografin-76 (25 ml/s), peaked at 4.3 +/- 0.3 mg/ml (mean +/- SD) compared to 14.8 +/- 0.8 mg/ml following direct injection of 40 ml at 13 ml/s (p less than 0.001). The computer enhanced venous-injected images had an optical contrast 14 times greater than that of the unenhanced direct left ventriculogram. This increase in optical contrast provided unambiguous subjective definition of the endocardial borders. This technique is applicable to both central and peripheral contrast injection whereby high quality images can be obtained at approximately 98% reduction in radiation (5 mA, 65-85 kV), allowing performance of serial studies.

Angiocardiography↗
PubMed2004

Enhanced speed and precision of measurement in a computer-assisted digital cephalometric analysis system.

The computer-assisted digital cephalometric analysis system (CADCAS) may reduce the time required for cephalometric analysis, especially for taking measurements. Aimed at estimating the time saved by using CADCAS, we measured the time needed by a clinician to perform the analysis in a traditional manner. We also sought to verify the accuracy achieved by traditional cephalometric analysis by exploring the disagreement between manual measurements and those generated by CADCAS. Our results revealed that, on average, even an experienced clinician needed more than 25 minutes to perform an entire cephalometric analysis using a traditional method, with more than 15 minutes of this needed just for taking measurements. Disagreements between measurements by traditional method and those by CADCAS were most frequently noted in the measurement value of cephalometric items reflecting the severity of a jaw discrepancy by the "sign" reflecting the anteroposterior relationship. After excluding the measurements with obvious error, the measurement differences between traditional method and CADCAS were not statistically significant in 23 of a total of 26 cephalometric items. In conclusion, the CADCAS can reduce the time needed for cephalometric analysis and can help reduce the human errors introduced during the manual-measuring procedure in the traditional cephalometric analysis.

Cephalometry↗
PubMed2006

Immunohistochemistry quantification by a digital computer-assisted method compared to semiquantitative analysis.

PURPOSE: To compare immunostaining quantification obtained by a digital computer-assisted method with the well-established semiquantitative analysis. METHODS: Cytoplasmic staining of galectin-3 was obtained by standard immunohistochemical reactions in 25 cases of well-differentiated thyroid carcinoma. The expression index that associates the conventional area fraction of labeled cells with the immunostaining intensity score based on visual qualitative observation was used as the semiquantitative analysis. A digital computer-assisted method is described based on the use of an image processing program (ImageLab). Three parameters were obtained: (1) percentage of labeled cells; (2) digital immunostaining intensity, and (3) digital expression index. The proposed method allows numerical analysis of the immunostaining intensity. RESULTS: There was a strong correlation between the immunostaining intensity obtained by the two methods (Pearson correlation coefficient, r = 0.71, P = 0.0001). The same was observed between expression indexes (Pearson correlation coefficient, r = 0.66, P = 0.0001). CONCLUSION: Results obtained with our proposed digital computer-assisted method for immunoexpression analysis were concordant with the semiquantitative analysis. In addition, digital values can also resolve disagreement among different observers about the quality of staining intensity because the digital method does not classify the results into groups, but rather provides a numerical value for each individual case; thus, it increases the diagnostic and, more importantly, the prognostic sensitivity of the immunohistochemical analysis.

Analysis of Variance↗
PubMed1991

Doppler detection of decompression bubbles with computer assisted digitization of ultrasonic signals.

Precordial Doppler ultrasonic monitoring is routinely used for detection of venous gas bubbles resulting from decompression in hypobaric or hyperbaric applications. Bubble scoring codes have been devised in an attempt to quantify the number of audible bubble signals heard over the background sounds of the cardiac cycle. The audio interpretation of these ultrasonic backscatter signals remains the most common method for decompression evaluation. We report on the use of an inexpensive, commercially available audio digitizer in conjunction with a personal computer to digitize Doppler bubble signals for visual and electronic evaluation. This device can be operated simultaneously with Doppler audio monitoring. Precordial and arterial Doppler recordings of gas bubbles were obtained from anesthetized dogs after intravascular infusion or following decompression. Additional evaluations were conducted on Doppler bubble recordings obtained from human decompression studies. The device can be used in real-time or for later signal analysis. Accompanying menu-driven software provides for numerous signal modification options and visual displays. This device can provide a simultaneous visual display of Doppler signals normally only available for audio evaluation.

Animals↗
PubMed1986

Diagnostic accuracy of coronary angiography utilizing computer-based digital subtraction methods. Comparison to conventional cineangiography.

To evaluate the efficacy of mask-mode digital subtraction angiography in selective coronary arteriography, we compared computer-based digital subtraction angiograms to standard film-based angiograms in 77 patients. Digital angiography was performed utilizing a 512(2) matrix and a framing rate of 30 frames/second. Radiation parameters were selected after a pilot dose-ranging trial, and were 70-120 KVP, 10-30mA and 0.8 to 5msec pulse width. Single view digital angiograms were compared to single view conventional angiograms in 27 patient; the two angiograms agreed within one grade of severity in 84 percent of the lesions or normal arteries seen. Multiple view digital angiograms were compared to multiple view conventional angiograms in 50 patients. Agreement within one grade of severity was found for 90 percent of lesions or normal arteries. Digital angiography detected 95 percent of collateral vessels seen on conventional angiography. We conclude that computer-based mask-mode digital subtraction angiography can be utilized in selective coronary angiography to obtain results comparable to those using conventional film-based cineangiography.

Adult↗
PubMed1976

Medical applications of analogue and digital telephone data links.

The increasing use of digital computer techniques for the analysis of signals such as the EEG, ECG, plethysmograms and cardiac output curves has led to the use of multichannel analogue frequency modulation telephone data links in the forward direction from the patient to the computer and digital links in the return direction. Single-channel analogue links are also being used for the surveillance of cardiac pacemaker patients and the television Viewphone offers the possibility of a visual contact between two centers. Examples will be given of the use of these various forms of telephone link.

Computers↗
PubMed2001

Chemical reaction-diffusion implementation of finding the shortest paths in a labyrinth.

An experimental technique for finding the shortest paths in a labyrinth is elaborated on based on chemical reaction-diffusion media. The system designed has hybrid architecture that combines an information-processing reaction-diffusion medium performing operations of high computational complexity with a digital computer carrying out supplementary operations. Two principal points are assumed as a basis for this design. They are the following: a light-sensitive Belousov-Zhabotinsky-type reagent chosen as a reaction-diffusion medium that offers the opportunity to simulate a labyrinth and spread wave evolution by its images stored in the medium; fast light-induced phase wave processes that spread through the labyrinth in seconds instead of the dozens of minutes typical of trigger waves inherent in reaction-diffusion media. Images of consecutive wave-spreading steps are stored in the memory of a digital computer. These images are used to determine the shortest paths based on the additional procedure of testing for the connectedness of labyrinth fragments.

Journal Article↗
PubMed2000

Three-dimensional matching by use of phase-only holographic information and the Wigner distribution.

Matching of three-dimensional (3-D) objects is achieved by Wigner analysis of the correlation pattern between the phase-only holographic information of a reference object and that of a target object. First, holographic information on the reference object and on the target object is extracted by use of optical scanning holography as a form of electrical signal. This electrical information is then stored in a computer for digital processing. In the digital computer, the correlation between the phase-only information of the hologram of the reference object and that of the target object is calculated and analyzed by use of a Wigner distribution. The Wigner distribution yields a space-frequency map of the correlation pattern that indicates whether the 3-D image of the target object matches that of the reference object. When the 3-D image of the target object matches that of the reference object, the Wigner distribution gives a well-defined line that directly indicates the 3-D location of the matched target object. Optical experiments with digital processing are described to demonstrate the proposed matching technique.

Journal Article↗
PubMed1976

On-line computation of cardiac output with the thermodilution method, using a digital minicomputer.

In the present study, several techniques for calculating cardiac output were evaluated in order to find an accurate technique suitable for on-line digital computation. The thermodilution method was evaluated by different calculation techniques and by comparing these techniques with electromagnetic flowmeter values. Comparison of thermal dilution curves, manually calculated by the log-normal and the exponential assumption, showed a correlation coefficient of 0.978 between the two methods, the former values being 11% higher. The exponential method correlated very well with the technique, using a correction factor for injection errors (r = 0.999). Since the exponential technique correlated well with the electromagnetic values (r = 0.84) and since it was less complicated than the technique, using correction factors, this technique was chosen for automation. Comparison of exponential calculated thermodilution values with a digital computer and manually, showed a correlation coefficient of 0.991. Therefore, it was concluded that on-line computation of thermodilution curves improves the applicability of the termodilution techniques as a means of measuring cardiac output.

Animals↗
PubMed1982

Direct measurement of sarcomere length from isolated cardiac cells.

Isolated cardiac muscle cells enzymatically digested with collagenase and hyaluronidase from whole rat myocardium demonstrate the characteristics of an intact membrane in that they tolerate millimolar concentrations of free Ca2+ and exhibit phasic contractions with electrical excitation. These isolated cells maintain their characteristic A-I band striation patterns when at rest or during contraction. An apparatus has been developed to directly image these cells with phase-contrast micrography onto a 1,728-element charge-coupled device photodiode array for rapid data storage in a digital computer. The digitized striation pattern profile was analyzed for individual and average sarcomere spacing. In isotonic media the average resting sarcomere length ranged from 1.77 to 1.91 micrometers in 13 cells, with a mean length of 1.83 +/- 0.12 micrometers. Electrically stimulated phasic contractions in three cells demonstrated a synchronous 20% decrease in sarcomere spacing to a mean of 1.51 micrometers. Striation spacing decreased under hypertonic stress but elongated only up to 1.93 micrometers in hypotonic solutions, suggesting that some internal elastic constraint exists that limits elongation of the cell.

Animals↗
PubMed2000

An assessment of digital image analysis to measure fibrosis in liver biopsy specimens of patients with chronic hepatitis C.

The aim was to assess the validity of a digitally computed fibrosis ratio as a measure of fibrosis stage in liver biopsy specimens. We scored 230 liver biopsy specimens from patients with chronic hepatitis C for fibrosis using modified Knodell criteria; fibrosis ratios were computed from digital images that encompassed the complete trichrome-stained section of each case. Although an overall correlation between fibrosis ratio and ordinal score was present, subset analysis showed that this correlation existed only among biopsy specimens with high scores (3-6, early bridging fibrosis to established cirrhosis). There was no correlation or difference between category means found among biopsy specimens with low scores (0-3, normal to early bridging fibrosis). Furthermore, concordance by both estimates in direction of fibrosis change among serial liver biopsy specimens was found in only 11 (30%) of 37 pairs compared. The findings suggest that a qualitative assessment of the computerized fibrosis pattern is necessary for the interpretation of computerized fibrosis ratio measurements, particularly in patients with early stage fibrosis.

Biopsy↗
PubMed2004

Cluster computing for digital microscopy.

Microscopy is becoming increasingly digital and dependent on computation. Some of the computational tasks in microscopy are computationally intense, such as image restoration (deconvolution), some optical calculations, image segmentation, and image analysis. Several modern microscope technologies enable the acquisition of very large data sets. 3D imaging of live cells over time, multispectral imaging, very large tiled 3D images of thick samples, or images from high throughput biology all can produce extremely large images. These large data sets place a very large burden on laboratory computer resources. This combination of computationally intensive tasks and larger data sizes can easily exceed the capability of single personal computers. The large multiprocessor computers that are the traditional technology for larger tasks are too expensive for most laboratories. An alternative approach is to use a number of inexpensive personal computers as a cluster; that is, use multiple networked computers programmed to run the problem in parallel on all the computers in the cluster. By the use of relatively inexpensive over-the-counter hardware and open source software, this approach can be much more cost effective for many tasks. We discuss the different computer architectures available, and their advantages and disadvantages.

Cells↗
PubMed2002

Workflow assessment of digital versus computed radiography and screen-film in the outpatient environment.

An objective assessment and comparison of computed radiography (CR) versus digital radiography (DR) and screen-film in terms of workflow, productivity, speed-of-service, and potential cost justification for imaging ambulatory patients is presented. Perceived ease-of-use and workflow of each device is collected via a technologist opinion survey. Productivity is measured as the rate of patient throughput from normalized timing studies. The overall speed-of-service is calculated from the time of examination ordering as stamped in the radiology information system (RIS), to the time of image availability on the picture archiving and communication system (PACS), to the time of interpretation rendered (from the RIS). Comparative results of screen-film (analog) versus a CR reader and a DR dedicated chest unit show a higher patient throughput for the digital systems. A mean of 10.7 patients were moved through the DR chest room per hour, and 9.2 patients per hour using CR, versus 8.2 patients per hour for the analog device. Measured time to image availability for interpretation is much faster for both DR and CR versus screen-film, with the mean minutes to image availability calculated as 5.7 +/- 2.5 minutes for DR, 6.7 +/- 1.5 minutes for CR, and 29.2 +/- 14.3 minutes for screen film. DR and CR can improve workflow and productivity over analog screen-film in a PACS for delivery of projection radiography services in an outpatient environment, but DR requires high volume to be cost effective over CR.

Efficiency, Organizational↗
PubMed1986

Tumor size dependent changes in a murine fibrosarcoma: use of in vivo 31P NMR for non-invasive evaluation of tumor metabolic status.

Tumor tissue contains viable hypoxic regions that are radioresistant and often chemoresistant and may therefore be responsible for some treatment failures. A subject of general interest has been the development of non-invasive means of monitoring tissue oxygen. Pulse Fourier transform 31P NMR spectroscopy can be used to estimate intracellular nucleotide triphosphates (NTP), phosphocreatinine (PCr), inorganic phosphate (Pi) and pH. We have obtained 31P NMR spectra as an indirect estimate of tissue oxygen and metabolic status in a C3H mouse fibrosarcoma FSaII. Sequential spectra were studied during tumor growth in a cohort of animals and peak area ratios for several metabolites were computed digitally by computer. During growth, tumors showed a progressive loss of PCr with increasing Pi, and most tumors greater than 250 mm3 in volume had little or no measurable PCr. The smallest tumors (38 mm3 average volume) had PCr/Pi ratios of 1.03 +/- .24, whereas tumors 250 mm3 or more had an average PCr/Pi ratio of 0.15 +/- .04. Similarly derived NTP/Pi ratios decreased with tumor size, but this change was not significant (p = .17). Radiobiologic hypoxic cell fractions were estimated using the radiation dose required to control tumor in 50% of animals (TCD50) or by the lung colony technique. Tumors less than 100 mm3 had a hypoxic cell fraction of 4% (TCD50) while tumors 250 mm3 had a 40% hypoxic cell fraction (lung colony assay). These hypoxic fraction determinations correlated well with the depletion of PCr and decline in NTP/Pi ratios seen at 250 mm3 tumor volumes. Tumor spectral changes with acute ischemia were studied after ligation of the tumor bearing limb and were similar to changes seen with tumor growth. PCr was lost within 7 minutes, with concurrent increase in Pi and loss of NTP. Complete loss of all high energy phosphates occurred by 40 minutes of occlusion. In vivo tumor 31P NMR spectroscopy can be used to estimate tissue metabolic status and may be useful in non-invasive prediction of hypoxic cell fraction, reoxygenation, and radiation treatment response.

Animals↗
PubMed1965

A MATHEMATICAL MODEL OF THE HUMAN RESPIRATORY CONTROL SYSTEM.

The respiratory system exhibits the properties of a control system of the regulator type. Equations describing this biological control system have been derived. Transient and steady-state solutions for various CO(2) and O(2) step input disturbances were obtained utilizing a digital computer and are compared with experimental results. The effectiveness of the respiratory system as a regulator is investigated. Further extensions of the model are suggested.

Carbon Dioxide↗