Biomedical subjects

G Puentes

Publications and source records attributed to G Puentes.

6 recordsLinked to original sources

PubMed2006

Maximum-likelihood estimation of Mueller matrices.

We show that the method of maximum-likelihood estimation, recently introduced in the context of quantum process tomography, can be applied to the determination of Mueller matrices characterizing the polarization properties of classical optical systems. Contrary to linear reconstruction algorithms, the proposed method yields physically acceptable Mueller matrices even in the presence of uncontrolled experimental errors. We illustrate our method with the case of an unphysical measured Mueller matrix taken from the literature.

Journal Article↗

PubMed2004

Ray splitting in paraxial optical cavities.

We present a numerical investigation of the ray dynamics in a paraxial optical cavity when a ray-splitting mechanism is present. The cavity is a conventional two-mirror stable resonator and the ray splitting is achieved by inserting an optical beam splitter perpendicular to the cavity axis. We show that depending on the position of the beam splitter the optical resonator can become unstable and the ray dynamics displays a positive Lyapunov exponent.

Journal Article↗

PubMed2000

Neurobehavioural outcomes of penetrating and tangential gunshot wounds to the head.

OBJECTIVE: The objective of this study was to compare penetrating and tangential gunshot wounds to the head with regards to demographic, neurobehavioural and clinical outcome measures. METHODS: Twenty-nine patients with penetrating gunshot wounds (P-GSW) and 11 patients with tangential gunshot wound (T-GSW) to the head admitted to an acute neurotrauma service were compared using standardized neurobehavioural and clinical outcome measures. RESULTS: The mean GCS was 10.5 +/- 0.79 for the P-GSW group and 13.4 +/- 0.72 for the T-GSW group. The mean AIS-CNS for the P-GSW group was 5.00 +/- 0 and for the T-GSW group was 3.7 +/- 0.27. Significance was found on Digit Span (p < 0.05) and Block Design (p < 0.009) subtests. Outcomes between the two groups were similar, except for significant differences were found for acute length of stay (LOS) (P-GSW was 47.72 +/- 13.2 and T-GSW group was 13.0 +/- 1.3, p = 0.005) and for acute care charges (P-GSW group was $150,533 +/- 23,834 and T-GSW group was $70,712 +/- 16,587, p = 0.05). CONCLUSIONS: Initially, a penetrating gunshot wound is a more severe and costly injury than a tangential gunshot wound to the head, however T-GSW possess significant deficits and, if the patient survives past the acute phase of recovery, the two groups have similar functional outcomes. Future standard classification, neuropsychological, and clinical outcome measures.

Adult↗

PubMed1996

Does coronary artery screening by electron beam computed tomography motivate potentially beneficial lifestyle behaviors?

We evaluated the extent to which cardiovascular risk-reducing behaviors are initiated as a result of knowledge of newly detected coronary artery disease, based on test results from noninvasive electron beam computed tomography (EBCT). A total of 703 men and women, aged 28 to 84 years, asymptomatic and without prior coronary disease, who had a baseline EBCT coronary artery scan and basic medical history and risk factor information completed a follow-up survey questioning them about health behaviors undertaken since their scan. Baseline calcium scores were significantly higher in those who subsequently reported consulting with a physician, or reported new hospitalization, coronary revascularization, beginning aspirin usage, blood pressure medications, cholesterol-lowering therapy, decreasing dietary fat, losing weight, beginning vitamin E, and under more worry (all p <0.01). Other factors, including reducing time worked, obtaining life insurance, losing employment, increased work absenteeism, increasing exercise, or stopping smoking were not associated with coronary calcium. In logistic regression, after adjusting for age, gender, pre-existing high cholesterol, high blood pressure, cigarette smoking, and a positive family history of coronary disease, the natural log of total calcium score remained associated with new aspirin usage, new cholesterol medication, consulting with a physician, losing weight, decreasing dietary fat, new coronary revascularization (all p <0.01), but also new hospitalization (p <0.05) and increased worry (p <0.001). The results suggest that potentially important risk-reducing behaviors may be reinforced by the knowledge of a positive coronary artery scan, independent of preexisting coronary risk factor status.

Adult↗

PubMed1996

Prognostic value of coronary calcification and angiographic stenoses in patients undergoing coronary angiography.

OBJECTIVES: This investigation sought to determine the relative prognostic value of coronary calcific deposits and coronary angiographic findings for predicting coronary heart disease-related events in patients referred for angiography. BACKGROUND: The relation among coronary calcification, coronary stenoses and coronary heart disease-related events is of interest on a clinical as well as a pathophysiologic basis. METHODS: Four hundred ninety-one symptomatic patients underwent coronary angiography and electron beam computed tomography at five different centers between April 1989 and December 1993. The electron beam computed tomograms were interpreted by a cardiologist with no knowledge of the coronary angiographic and clinical data. Receiver operating characteristic (ROC) curves were constructed to determine the relation between electron beam computed tomographic and coronary angiographic findings. A follow-up telephone survey was completed in 86% of patients. The records for all patients who died or were admitted to the hospital for chest pain or suspected myocardial infarction were reviewed by three other cardiologists with no knowledge of the coronary angiographic and electron beam computed tomographic study results. RESULTS: The mean (+/- SE) area under the ROC curve was 0.75 +/- 0.02 for the coronary calcium score, indicating moderate discriminatory power for this score for predicting angiographic findings. Thirteen coronary heart disease-related deaths and eight nonfatal acute infarctions occurred over 30 +/- 13 months. Scores were sorted in ascending order and divided into quartiles of equal size. One patient in the first quartile had a fatal myocardial infarction (coronary calcium score range 0 to 2.1); 2 in the second quartile (range 2.1 to 75.3), 8 in the third quartile (range 75.3 to 397.1) and 10 in the fourth quartile (> 397.1) had a coronary heart disease-related event. Application of bivariate logistic regression showed that log score but not number of angiographically diseased vessels significantly predicted the probability of a coronary heart disease-related event occurring during follow-up. CONCLUSIONS: Electron beam computed tomographic calcium scores correlate moderately well with angiographic findings. These scores predict coronary heart disease-related events in patients undergoing angiography as well as do the number of angiographically affected arteries.

Calcinosis↗

PubMed1996

Detection of coronary calcification with electron-beam computed tomography: evaluation of interexamination reproducibility and comparison of three image-acquisition protocols.

The purpose of this investigation was to determine the variability of electron-beam computed tomography (EBCT) measurement of coronary calcification by using two commonly employed image-acquisition protocols and to compare this variability with that of a new image-acquisition protocol. We performed three EBCT scans within 15 minutes on each of 324 consecutive high-risk, asymptomatic subjects participating in an ongoing epidemiologic research investigation. Subjects were divided into three groups: group 1 (n = 175) received two scans with a standard 20-slice, 3 mm slice thickness image-acquisition protocol and a third scan with the new 20-slice, 6 mm slice thickness protocol; group 2 (n = 77) received two scans with a new 6 mm slice thickness image-acquisition protocol and a third scan with a standard 20-slice, 3 mm slice thickness protocol; group 3 (n = 72) received two scans with a 30-slice, 3 mm slice thickness image-acquisition protocol and a third scan with a 20-slice, 6 mm slice thickness protocol. Calcium score, calcium mass estimate, and calcium volume estimate were determined for each scan. We compared retest variability of calcium measurements for each of the three image-acquisition protocols. The variability of the new 6 mm slice thickness protocol was significantly lower than that of either the 20-slice 3 mm slice thickness protocol (p = 0.009) or the 30-slice 3 mm slice thickness protocol (p = 0.02) for measurement of calcium score, mass, or volume. Retest reproducibility for all three image-acquisition protocols was low; however, the 20-slice 6 mm slice thickness protocol gave reproducibility superior to either of the 3 mm slice thickness protocols. Variability of absolute indices increased, and variability of relative indices decreased as the value of these indices increased. EBCT is not sufficiently reproducible to allow serial quantitation of coronary calcium in individual patients over relatively short periods (< 2 years).

Aged↗