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PubMedDate not supplied

Measuring human age by estimating lifetime caloric consumption.

BACKGROUND: This study was prompted by a desire to measure human age by a means other than chronological or biological age. The purpose of the study was to use the total lifetime caloric intake in men as an index of aging. METHOD: The study was carried out by developing an algorithm to approximate the lifetime caloric intake. The total caloric intake is expressed such that one calorie-age year is defined as the total calories expended by an individual during his/her 20th year. RESULTS: The results indicated that (1) the caloric intake of men progressively decreases with advancing age, that (2) the caloric-age is usually less than chronological age, and that (3) the caloric-age algorithm is a simple although crude method to assess lifetime caloric intake. CONCLUSION: The most important conclusion is that a person can get a better appreciation of the importance of avoiding excess caloric intake if human age is measured in terms of lifetime caloric intake.

Age Determination by Teeth↗
PubMed2005

Macular segmentation with optical coherence tomography.

PURPOSE: To develop a software algorithm to perform automated segmentation of retinal layer structures on linear macular optical coherence tomography (StratusOCT; Carl Zeiss Meditec, Inc., Dublin, CA) scan images and to test its performance in discriminating normal from glaucomatous eyes in comparison with conventional circumpapillary nerve fiber layer (cpNFL) thickness measurement. METHODS: Four layer structures within the retina were defined: the macular nerve fiber layer (mNFL), the inner retinal complex (IRC; retinal ganglion cell [RGC] layer + inner plexiform and nuclear layers), outer plexiform layer (OPL), and outer retinal complex (ORC; outer nuclear layer + photoreceptor layer). Normal and glaucomatous eyes underwent fast macular map and fast NFL OCT scans. Linear macular images were analyzed using the developed algorithm, and the results were compared with the cpNFL thickness measurement. RESULTS: Forty-seven subjects (23 normal and 24 with glaucoma) were analyzed. mNFL, cpNFL, IRC, and the total retinal thicknesses were significantly greater in normal than in glaucomatous eyes (P < or = 0.0002; Wilcoxon), whereas OPL thickness did not show a significant difference (P = 0.46). ORC thickness was significantly greater in glaucomatous than normal eyes (P = 0.035). Areas under the receiver operator characteristic curve (AROCs) for discriminating normal from glaucomatous eyes were highest with mNFL + IRC (0.97) and lowest with OPL (0.56). AROCs for OPL and ORC were significantly smaller than those for mNFL, IRC, mNFL+IRC, and cpNFL (P < or = 0.01). AROCs for IRC, mNFL + IRC, and cpNFL were significantly larger than for retinal thickness (P < or = 0.049). Among the best-performing parameters (mNFL, IRC, mNFL + IRC, and cpNFL) there was no significant difference in AROCs (P > or = 0.15). CONCLUSIONS: The newly developed macular segmentation algorithm described herein demonstrated its ability to quantify objectively the glaucomatous damage to RGCs and NFL and to discriminate between glaucomatous and normal eyes. Further algorithm refinement and improvements in resolution and image quality may yield a more powerful methodology for clinical glaucoma evaluation.

Algorithms↗
PubMed2006

Improving the repeatability of topographic height measurements in confocal scanning laser imaging using maximum-likelihood deconvolution.

PURPOSE: To evaluate maximum likelihood (ML) blind deconvolution as a technique for improving the repeatability of topographic height measurements obtained from scanning laser tomography (Heidelberg Retinal Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany). METHODS: ML blind deconvolution is an image-processing technique that estimates the original scene from a degraded image. This technique has been used in confocal scanning laser microscopy to remove "out-of-focus" haze in three-dimensional confocal image stacks. ML blind deconvolution requires no prior estimation of the point-spread function (PSF), as opposed to classic linear deconvolution methods. Instead, the algorithm estimates an initial PSF based on the optical setup of the confocal scanning device and optics of the eye and iteratively proceeds to a solution. The improvement in repeatability of height measurements from mean topography images within scan (intrascan) and between scans (interscan) afforded by ML deconvolution was evaluated in a test-retest series of HRT images from 40 ocular hypertensive and glaucomatous patients with varying degrees of media opacity. RESULTS: There was an improvement in intrascan repeatability in 38 out of the 40 mean topography images (median improvement 2.5 microm, inter-quartile range 2.19, P < 0.001), and an improvement in interscan repeatability in 33 of the 40 mean topographies (median improvement, 1.0 microm, interquartile range 3.49, P < 0.001). There was a positive association between the magnitude of the improvement in repeatability and the level of mean pixel height standard deviation (MPHSD), intrascan (P = 0.004) and interscan (P = 0.002). CONCLUSIONS: ML blind deconvolution algorithm improves the repeatability of topographic height measurements from the HRT. This improvement was greater in patients with poorer quality images.

Algorithms↗
PubMedDate not supplied

Urinary cytology screening: the decision facing the asymptomatic patient.

Voided-urine cytology as a screen for the early detection of urinary bladder cancer is analyzed to determine its potential in an asymptomatic population. Previous cost-effectiveness assessments predict that screening will extend life-span at a cost-per-detected-case that is comparable to those of other cancer screening efforts. The focus here is on investigating screening from the perspective of the individual contemplating the screening decision. The analysis is based on a computerized model of bladder cancer which integrates a Markov representation of the induction and progression of the disease with algorithms representing diagnostic and therapeutic intervention strategies, intervention effectiveness, and cost. It is shown that the utilities, as well as the probabilities, of true-positive, false-positive, and false-negative screening outcomes are affected by the particular testing regimen employed and the age at which screening takes place. Screening at age 55 or age 65 was analyzed for individuals of normal risk. Analyses predict that the predisposition of cytology screening to identify the high-grade, aggressive form of the disease will result in gains in life expectancy of more than three years for the asymptomatic true-positive case. Results support the decision to screen, and by requiring a repeatedly positive test result, the probability of a false-positive outcome will not exceed that of a true-positive outcome at age 65. Except for the risk of a false-positive outcome, cytology screening compares favorably with what could theoretically be obtained if a 100% accurate screening test were available.

Adult↗
PubMed1997

The registration of multiple medical images acquired from a single subject: why, how, what next?

This paper reviews some of the recent techniques which have been used to register multiple images of the same patient. Image registration is a problem which has been receiving significant attention from the medical image processing community in recent years. A successful image registration can aid in patient diagnosis, treatment assessment, image guided interventions, surgery planning and surgery. At present the majority of work has focused on rigid body transformations of images. We shall discuss some of the approaches used and outline a key automatic method in detail. In order to allow image registration of parts of the body which do not remain rigid, either due to patient movement or a change in pathology, nonlinear deformation techniques are being developed. We shall talk of the history of these methods before explaining deformations using landmarks and a recent extension to allow the definition of rigid structures in such warps in more detail. Validation of these methods is of great importance and we shall discuss work which has already been carried out on this topic for rigid body registrations as well as ideas for the validation of deformation algorithms.

Algorithms↗
PubMed2007

Single trial somatosensory evoked potential extraction with ARX filtering for a combined spinal cord intraoperative neuromonitoring technique.

BACKGROUND: When spinal cord functional integrity is at risk during surgery, intraoperative neuromonitoring is recommended. Tibial Single Trial Somatosensory Evoked Potentials (SEPs) and H-reflex are here used in a combined neuromonitoring method: both signals monitor the spinal cord status, though involving different nervous pathways. However, SEPs express a trial-to-trial variability that is difficult to track because of the intrinsic low signal-to-noise ratio. For this reason single trial techniques are needed to extract SEPs from the background EEG. METHODS: The analysis is performed off line on data recorded in eight scoliosis surgery sessions during which the spinal cord was simultaneously monitored through classical SEPs and H-reflex responses elicited by the same tibial nerve electrical stimulation. The single trial extraction of SEPs from the background EEG is here performed through AutoRegressive filter with eXogenous input (ARX). The electroencephalographic recording can be modeled as the sum of the background EEG, which can be described as an autoregressive process not related to the stimulus, and the evoked potential (EP), which can be viewed as a filtered version of a reference signal related to the stimulus. The choice of the filter optimal orders is based on the Akaike Information Criterion (AIC). The reference signal used as exogenous input in the ARX model is a weighted average of the previous SEPs trials with exponential forgetting behavior. RESULTS: The moving average exponentially weighted, used as reference signal for the ARX model, shows a better sensibility than the standard moving average in tracking SEPs fast inter-trial changes. The ability to promptly detect changes allows highlighting relations between waveform changes and surgical maneuvers. It also allows a comparative study with H-reflex trends: in particular, the two signals show different fall and recovery dynamics following stressful conditions for the spinal cord. CONCLUSION: The ARX filter showed good performances in single trial SEP extraction, enhancing the available information concerning the current spinal cord status. Moreover, the comparison between SEPs and H-reflex showed that the two signals are affected by the same surgical maneuvers, even if they monitor the spinal cord through anatomically different pathways.

Algorithms↗
PubMed2004

Non-rigid image registration: theory and practice.

Image registration is an important enabling technology in medical image analysis. The current emphasis is on development and validation of application-specific non-rigid techniques, but there is already a plethora of techniques and terminology in use. In this paper we discuss the current state of the art of non-rigid registration to put on-going research in context and to highlight current and future clinical applications that might benefit from this technology. The philosophy and motivation underlying non-rigid registration is discussed and a guide to common terminology is presented. The core components of registration systems are described and outstanding issues of validity and validation are confronted.

Algorithms↗
PubMed2003

Convergent validity of the ASAM Patient Placement Criteria using a standardized computer algorithm.

The study examined the convergent validity of the ASAM Patient Placement Criteria (PPC) by comparing Level of Care (LOC) recommendations produced by two alternative methods: a computerdriven algorithm and a "standard" clinical assessment. A cohort of 248 applicants for alcoholism treatment were evaluated at a multi-modality treatment center. The two methods disagreed (58% of cases) more often than they agreed (42%). The algorithm recommended a more intense LOC than the clinician protocol in 81% of the discrepant cases. Four categories of disagreement accounted for 97% of the discrepant cases. Several major sources of disagreement were identified and examined in detail: clinicians' reasoned departures from the PPC rules, conservatism in algorithm LOC recommendations, and measurement overlap between two specific dimensions. In order for the ASAM PPC and its associated algorithm to be embraced by treatment programs, the observed differences in LOC recommendations between the algorithm and "standard" clinical assessment should be resolved.

Algorithms↗
PubMedDate not supplied

Non-invasive thermal assessment of tissue phantoms using an active near field microwave imaging technique.

An active microwave imaging system for non-invasive temperature sensing has been developed and evaluated. The system is designed to assess biological tissues undergoing thermal therapy. This paper presents results that demonstrate the imaging capabilities of the microwave method using simulated and experimental phantom materials. Results from both numerical studies and laboratory experiments have been analysed and are presented. The imaging system uses a 16 channel fixed monopole array transceiver unit operating over a bandwidth of 300-900 MHz. The annular array diameter is 14.75 cm and is immersed in a 0.9% saline solution. Standard heterodyning principles are used for signal detection leading to a dynamic range of the system of better than 115dB. Image formation is accomplished with a 2-D finite element based, near-field iterative technique. This allows the simultaneous reconstruction of both the real and imaginary components of the dielectric property distribution in tissue equivalent phantoms. Data acquisition currently captures 144 complex field measurements per image. Image reconstruction requires approximately 2 min per iteration with a typical convergence in less than 10 steps. Experiments performed to evaluate the temperature dependence of biological phantoms (saline with variable salt concentrations) are described. The numerical accuracy and precision of the reconstruction algorithm based upon these phantom studies are presented. Simple laboratory models of localized hyperthermia have been used to evaluate the experimental accuracy and precision of the imaging system. A numerical precision of 0.02 degrees C and an accuracy of 0.37 degrees C have been observed with the current algorithm. In laboratory experiments, images have been reconstructed at different target temperatures and target saline concentrations. The effect of placing high contrast biological phantoms (i.e. bone/fat simulants) along with the heated objects have also been studied. Localized heating of the biological phantom is achieved by pumping a saline solution of pre-selected concentration through enclosed ends of hollow dielectric cylinders having approximately 5cm inner diameter and 4 mm wall thickness. The temperature of the heated zone is preset and maintained to +/-0.2 degrees C by an external heater and circulator. The results currently show that a maximum temperature precision of 0.98 degrees C and maximum relative accuracy of 0.56 degrees C has been achieved in the laboratory using the current generation of the prototype system.

Algorithms↗
PubMed2002

Early intervention in massive pulmonary embolism. A guide to diagnosis and triage for the critical first hour.

The diagnosis of massive pulmonary embolism should be considered expeditiously in all patients with unexplained hypotension, syncope, cardiac arrest, or hypoxemic respiratory failure. The presence of right ventricular overload on physical examination or electrocardiogram is an especially important clue. Depending on local expertise and the patient's stability, V/Q scanning, CT angiography, echocardiography, and right heart catheterization can be useful in establishing a diagnosis of pulmonary embolism. Supportive treatment includes oxygen, vasoactive medicines, and sometimes fluids. Although heparin is important in nearly all patients, 70% to 80% of patients also require an IVC filter, thrombolysis, or embolectomy.

Algorithms↗
PubMed1998

Bronchopulmonary sequestration and dextrocardia.

Bronchopulmonary sequestration (BPS) is usually a rare congenital anomaly, which is most frequently extralobar or intralobar. The case of a patient with positional congenital anomaly--dextrocardia (situs thoracalis inversus) and intrapulmonary sequestration (IPS) is presented. Clinical and radiological characteristics of EPS and IPS are discussed, and new combinations of congenital anomalies with bronchopulmonary sequestration are described, dextrocardia and intrapulmonary sequestration. The importance of the algorithm of diagnostic examinations is emphasized, from detection of bronchopulmonary sequestration on the chest roentgenogram to establishing a definite diagnosis by means of angiography.

Angiography↗
PubMed1997

Advice or diagnosis? A legal perspective.

Nurses cannot diagnose, but they can--and do--assess, inform and advise. A nurse-attorney offers advice on choosing a demand management service and on understanding the sometimes-subtle distinction.

Algorithms↗
PubMed2000

Optimal autoregressive model based medical image compression using genetic algorithm.

Image compression is the process of removal of redundant data in order to achieve savings in storage and communication costs. A new method for predictive coding of images is proposed using two-dimensional multiplicative autoregressive models. Genetic algorithm is implemented to compute autoregressive parameters. Comparison with other multiplicative autoregressive model based image compression method has also been reported here.

Algorithms↗
PubMedDate not supplied

Grayscale and proportion-corrected optical coherence tomography images.

BACKGROUND AND OBJECTIVE: The commercially available optical coherence tomography (OCT) scanner displays images in a pre-set window regardless of the projected scan length on the retinal surface. The aim of this study was to demonstrate the true dimensions of proportion-corrected OCT images and the additional information present in grayscale images. MATERIALS AND METHODS: OCT raw data were exported to an IBM-compatible PC and processed to show grayscale and proportion-corrected images using an automated software of our own design. RESULTS: Eyes with cystoid macular edema and retinal pigment detachment were analyzed. Grayscale images showed a finer gradation of signal reflectance. Scan lengths of 2, 4, 6, and 8 mm on the retinal surface showed different qualitative appearances using proportion-corrected software from the printed or on-screen images. CONCLUSIONS: Grayscale OCT images can be used to demonstrate additional information not present in false-color images. The disparity between the standard OCT image format and proportion-corrected images emphasizes the need for quantitative rather than qualitative evaluation of retinal dimensions and internal reflectance.

Algorithms↗
PubMed2001

Three-dimensional Hess screen test with binocular dual search coils in a three-field magnetic system.

PURPOSE: To establish an objective Hess screen test that allows a simultaneous and binocular analysis of all three axes of eye rotation. METHODS: In orthotropic and strabismic human subjects, both eyes were recorded with dual scleral search coils in a three-field magnetic system. Before mounting the search coil annuli on the eyes, the voltage offsets of each channel and the relative magnitudes of the three magnetic fields were determined. For calibration, subjects were only required to fix monocularly on a single reference target. During fixation of targets on the Hess screen by the uncovered eye, the three-dimensional eye position of both the occluded and the viewing eye was simultaneously measured. RESULTS: For clinical interpretation, an easy to understand graphical description of the three-dimensional Hess screen test was developed. Positions of orthotropic and strabismic eyes tended to follow Listing's law, which in both eyes allowed the determination of the primary position, that is, the position of gaze from which pure horizontal and pure vertical movements do not lead to an ocular rotation about the line-of-sight. To a first approximation, the location of primary position is a result of the summation of the individual rotation axes of the six extraocular muscles and thus can be used to infer which muscle is paretic. CONCLUSIONS: The three-dimensional Hess screen test with binocular dual search coils in a three-field magnetic system is an objective method to assess the ocular alignment in three dimensions with high precision. From these recordings, the clinician can relate deviations of primary position to specific eye muscle palsies.

Algorithms↗
PubMed2001

Asymptomatic microscopic hematuria in adults: summary of the AUA best practice policy recommendations.

The American Urological Association (AUA) convened the Best Practice Policy Panel on Asymptomatic Microscopic Hematuria to formulate policy statements and recommendations for the evaluation of asymptomatic microhematuria in adults. The recommended definition of microscopic hematuria is three or more red blood cells per high-power microscopic field in urinary sediment from two of three properly collected urinalysis specimens. This definition accounts for some degree of hematuria in normal patients, as well as the intermittent nature of hematuria in patients with urologic malignancies. Asymptomatic microscopic hematuria has causes ranging from minor findings that do not require treatment to highly significant, life-threatening lesions. Therefore, the AUA recommends that an appropriate renal or urologic evaluation be performed in all patients with asymptomatic microscopic hematuria who are at risk for urologic disease or primary renal disease. At this time, there is no consensus on when to test for microscopic hematuria in the primary care setting, and screening is not addressed in this report. However, the AUA report suggests that the patient's history and physical examination should help the physician decide whether testing is appropriate.

Algorithms↗
PubMedDate not supplied

[Use of an automated classifying system for the dispensary system of the population].

While processing blood values by an automatic classifying system, human beings can be divided into healthy (normal) and unhealthy (ill) persons. In so doing, one can evaluate the status of the body's individual systems (gastrointestinal tract, respiratory organs, locomotor apparatus, heart and vessels, urinary, endocrine, hemopoietic, and female genital organs, the central nervous system), which allows a physician to find a source of poor health from the very onset of disease.

Adult↗