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Biomedical subjects

John Eng

Publications and source records attributed to John Eng.

18 recordsLinked to original sources
PubMed2005

Human peripheral arteries: feasibility of transvenous intravascular MR imaging of the arterial wall.

Feasibility of in vivo transvenous intravascular magnetic resonance (MR) imaging of the human arterial wall was determined. All subjects provided written informed consent, and institutional review board approved the study. Six arteries in six patients were imaged with a guidewire placed in the iliac vein (n = 5) or left renal vein (n = 1). Pre- and postcontrast T1-weighted and T2-weighted transvenous MR imaging were performed. An atherosclerotic plaque with a fibrous cap was identified on 27 (42%) of 64 images of veins without stents; intimal hyperplasia in a renal artery with a stent was identified on 12 images. Contrast-to-noise ratios (CNRs) on arterial wall postcontrast T1-weighted images were superior to those on images obtained with other sequences (P < .001), and the postcontrast images demonstrated the greatest number of plaques with a low-signal intensity core and fibrous cap. Preliminary results show that transvenous MR imaging is feasible for high-spatial-resolution imaging of the arterial wall and atherosclerotic plaque. Postcontrast T1-weighted imaging affords greatest CNR for the arterial wall.

Aged↗
PubMed2005

Internet-based radiology order-entry, reporting, and workflow management system for coordinating urgent study requests during off-hours.

OBJECTIVE: Our aim was to develop a simple, low-cost, Internet-based application for radiology order-entry, reporting, and workflow management during off-hours. CONCLUSION: The system was quickly accepted by users both within and outside the radiology department, and it required very modest resources to develop, deploy, and support. In a busy on-call setting at a high-volume academic institution, the system described was effective in obtaining more thorough patient histories from referring physicians, reducing the number of telephone calls required, and documenting more rigorously the communication between radiologists and clinical services. These benefits allow the generation of more informative and timely radiology reports.

Emergencies↗
PubMed2004

Usefulness of clinical prediction rules for the diagnosis of venous thromboembolism: a systematic review.

PURPOSE: To summarize the evidence on the predictive value of clinical prediction rules for the diagnosis of venous thromboembolism. METHODS: We selected all studies in the English literature in which a clinical prediction rule was prospectively validated against a reference standard, and calculated likelihood ratios, predictive values, and the area under the receiver operating characteristic (ROC) curve for each prediction rule. RESULTS: Twenty-three studies met our eligibility criteria: 17 evaluated prediction rules for the diagnosis of deep venous thrombosis and six evaluated rules for pulmonary embolism. The most frequently evaluated prediction rule for deep vein thrombosis was the Wells rule, which had median positive likelihood ratios of 6.62 for patients with a high pretest probability, 1 for moderate pretest probability, and 0.22 for low pretest probability. The median area under the ROC curve was 0.82. Addition of the D-dimer test to the prediction rule increased the median area under the curve to 0.90. The Wells prediction rule was the most commonly studied for pulmonary embolus and had median positive likelihood ratios of 6.75 for those with high pretest probability, 1.82 for moderate pretest probability, and 0.13 for low pretest probability. The median area under the ROC curve was 0.82. CONCLUSION: The Wells prediction rule is useful in identifying patients at low risk of being diagnosed with venous thromboembolism. The addition of a rapid latex D-dimer assay improved the overall performance of the prediction rule.

Clinical Trials as Topic↗
PubMed2004

Getting started in radiology research: asking the right question and identifying an appropriate study population.

Establishing a solid research question and appropriate methodology for selecting study participants forms the basis for good study design. For example, the diminished reputation of retrospective studies can be traced to problems with defining the research question and study population. In retrospective studies, one sets out to use data collected in the past, usually for a purpose other than the research study being executed. Therefore, the investigator does not have the opportunity to tailor the data collection to the research question or control the selection of study participants. The potential mismatch between the collected data, the intended research question, and the intended study population is a major cause, if not the main cause of bias in retrospective studies. Prospective studies offer an investigator the opportunity to collect all data relevant to the research question and to control the selection of study participants to minimize selection bias. It is up to the investigator to take full advantage of this opportunity through adequate planning of the study. Retrospective studies are not without merit, however, because they may be the only practical way to study rare diseases or patient outcomes. Whatever the study design, problems in defining the study population should either be addressed in the study or stated as a limitation of the study. In this article, I have discussed the importance of considering the research question and selection of study participants and have provided some basic related advice (Table). These two aspects of clinical research have a substantial effect on whether a study's results are scientifically worthwhile and ultimately useful to others. Attention to these issues should be helpful to the various roles involved in the life of a study: the investigator planning the study, the reviewer of the resulting manuscript, and the reader of the published research article.

Humans↗
PubMed2004

Sample size estimation: a glimpse beyond simple formulas.

Small increments in the complexity of clinical studies can readily take sample size estimation and statistical power analysis beyond the capabilities of simple mathematic formulas. In this article, the method of simulation is presented as a general technique with which sample size may be calculated for complex study designs. Applications of simulation for determining sample size requirements in studies involving correlated data and comparisons of receiver operating characteristic curves are discussed.

Clinical Trials as Topic↗
PubMed2004

Safety and hemodynamic effects of pulmonary angiography in patients with pulmonary hypertension: 10-year single-center experience.

OBJECTIVE: We sought to examine the incidence of complications and change in pulmonary artery pressure in patients with pulmonary hypertension who were undergoing pulmonary angiography. MATERIALS AND METHODS: A retrospective review was performed for all patients who underwent pulmonary angiography over a 10-year period at a single institution. Patients with moderate pulmonary hypertension (pulmonary artery pressure, 30-59 mm Hg) and severe pulmonary hypertension (pulmonary artery pressure, >/= 60 mm Hg) served as the study population. Demographic data, clinical indication, pre- and postcontrast pulmonary artery pressure measurements, type of pulmonary hypertension, contrast agent volume, complications, and American Society of Anesthesiologists (ASA) classification were recorded for all patients and compared. RESULTS: Two hundred two of 612 patients who underwent pulmonary angiography had pulmonary hypertension. Moderate pulmonary hypertension was present in 155 patients (77%) and severe pulmonary hypertension, in 47 patients (23%). Three (2.0%) of four complications were fatal. The complication rate was higher in patients with severe pulmonary hypertension compared with patients with moderate pulmonary hypertension but not statistically significant (6.3% vs 0.6%, p = 0.63). Patients with complications had a higher mean ASA score than those without complications (4.0 vs 3.0, p = 0.03). Patients with lung transplants had the greatest increase in pulmonary artery pressure after pulmonary angiography compared with all other clinical indications (16.75 +/- 12.97 mm Hg vs 5.46 +/- 6.86 mm Hg, p = 0.003). CONCLUSION: The complication rate of pulmonary angiography in patients with pulmonary hypertension is low. However, in severely ill patients with acute pulmonary hypertension, pulmonary angiography should be undertaken with extreme caution.

Angiography↗
PubMed2004

Accuracy of CT in the diagnosis of pulmonary embolism: a systematic literature review.

OBJECTIVE: We sought to summarize systematically the published evidence describing the accuracy of contrast-enhanced helical CT for diagnosing pulmonary embolism. MATERIALS AND METHODS: We selected all systematic reviews published before December 2003 that evaluated the accuracy of CT angiography for the diagnosis of pulmonary embolism. We also selected all prospective studies from the same time period in the primary literature in which all subjects underwent both CT and conventional angiography, the latter being considered the reference standard. Articles were identified through a computerized MEDLINE search and by other means. The quality and content of each article were evaluated independently by pairs of researchers. RESULTS: Six systematic reviews and eight primary studies were selected. The combined sensitivities of CT for detecting pulmonary embolism ranged from 66% to 93% across the systematic reviews and the combined specificities ranged from 89% to 97%. Only one of the reviews reported a combined sensitivity of greater than 90%. Among the eight primary studies, the sensitivities ranged from 45% to 100% and specificities ranged from 78% to 100%. Only three of the eight primary studies reported a sensitivity greater than 90%. None of the primary studies used scanners with four or more detectors. CONCLUSION: A systematic literature review revealed a wide range of reported sensitivities, only a minority of which exceeded 90%. Pooled estimates of sensitivity and specificity reported by systematic literature reviews should be interpreted with caution because of potential selection bias and heterogeneity in the reviewed studies. Accuracy studies of recent generations of MDCT scanners are not yet available despite the current dissemination of this technology.

Humans↗
PubMed2003

Lung cancer screening with helical computed tomography in older adult smokers: a decision and cost-effectiveness analysis.

CONTEXT: Encouraged by direct-to-consumer marketing, smokers and their physicians are contemplating lung cancer screening with a promising but unproven imaging procedure, helical computed tomography (CT). OBJECTIVE: To estimate the potential benefits, harms, and cost-effectiveness of lung cancer screening with helical CT in various efficacy scenarios. DESIGN, SETTING, AND POPULATION: Using a computer-simulated model, we compared annual helical CT screening to no screening for hypothetical cohorts of 100 000 current, quitting, and former heavy smokers, aged 60 years, of whom 55% were men. We simulated efficacy by changing the clinical stage distribution of lung cancers so that the screened group would have fewer advanced-stage cancers and more localized-stage cancers than the nonscreened group (ie, a stage shift). Our model incorporated known biases in screening programs such as lead time, length, and overdiagnosis bias. MAIN OUTCOME MEASURES: We measured the benefits of screening by comparing the absolute and relative difference in lung cancer-specific deaths. We measured harms by the number of false-positive invasive tests or surgeries per 100 000 and incremental cost-effectiveness in US dollars per quality-adjusted life-year (QALY) gained. RESULTS: Over a 20-year period, assuming a 50% stage shift, the current heavy smoker cohort had 553 fewer lung cancer deaths (13% lung cancer-specific mortality reduction) and 1186 false-positive invasive procedures per 100 000 persons. The incremental cost-effectiveness for current smokers was $116 300 per QALY gained. For quitting and former smokers, the incremental cost-effectiveness was $558 600 and $2 322 700 per QALY gained, respectively. Other than the degree of stage shift, the most influential parameters were adherence to screening, degree of length or overdiagnosis bias in the first year of screening, quality of life of persons with screen-detected localized lung cancers, cost of helical CT, and anxiety about indeterminate nodule diagnoses. In 1-way sensitivity analyses, none of these parameters was sufficient to make screening highly cost-effective for any of the cohorts. In multiway sensitivity analyses, a program screening current smokers was $42 500 per QALY gained if extremely favorable estimates were used for all of the influential parameters simultaneously. CONCLUSION: Even if efficacy is eventually proven, screening must overcome multiple additional barriers to be highly cost-effective. Given the current uncertainty of benefits, the harms from invasive testing, and the high costs associated with screening, direct-to-consumer marketing of helical CT is not advisable.

Aged↗
PubMed2003

Outpatient therapy with low molecular weight heparin for the treatment of venous thromboembolism: a review of efficacy, safety, and costs.

PURPOSE: To summarize the evidence comparing the efficacy, safety, and costs of outpatient and inpatient treatment of venous thromboembolism. METHODS: We searched the literature through March 2002 for studies comparing outpatient and inpatient treatment of venous thromboembolism with low molecular weight heparin or unfractionated heparin, and for studies addressing the costs of low molecular weight heparin use in any setting. We included studies with comparison groups or decision analyses. RESULTS: Eight studies (three randomized trials and five cohort studies) compared outpatient use of low molecular weight heparin with inpatient use of unfractionated heparin in 3762 patients. The incidence of recurrent deep venous thrombosis was similar in the two groups (median, 4% [range, 0% to 7%] vs. 6% [range, 0% to 9%]), as was major bleeding (median, 0.5% [range, 0% to 2%] vs. 1% [range, 0% to 2%]). Use of low molecular weight heparin was associated with shorter hospitalization (median, 2.7 days [range, 0.03 to 5.1 days] vs. 6.5 days [range, 4 to 9.6 days]) and lower costs (median difference, 1600 dollars). Comparisons of outpatient and in-hospital use of low molecular weight heparin reported no difference in outcomes, but there were savings in hospitalization costs. Low molecular weight heparin was also found to be more cost saving and cost-effective than unfractionated heparin, with savings of 0% to 64% (median, 57%). CONCLUSION: The evidence indicates that outpatient treatment of deep venous thrombosis with low molecular weight heparin is likely to be efficacious, safe, and cost-effective.

Ambulatory Care↗
PubMed2003

Examining the role of cranial CT in the evaluation of patients with minor head injury: a systematic review.

This systematic review demonstrates that, in patients sustaining minor head injury with a history of loss of consciousness or amnesia, the proportion who subsequently have positive CT scans is not negligible. Published clinical prediction rules for selecting patients for subsequent CT examination are associated with a trade-off between sensitivity and specificity; therefore, a prediction rule with high sensitivity is expected to have relatively low specificity. Separate evaluation of the literature is required to determine the significance of positive and negative CT scans with respect to patient outcome.

Brain↗
PubMed2003

Arteriographic and pathologic evaluation of two suture-mediated arterial closure devices in a porcine model.

PURPOSE: To determine the acute and short-term effects the Sutura 8-F SuperStitch and Perclose 6-F Closer devices have on the femoral artery, as determined by angiography and pathologic examination. MATERIALS AND METHODS: From a common carotid artery cutdown, eight pigs underwent pelvic angiography (i) before placement of bilateral common femoral artery vascular sheaths, (ii) after sheath insertion, and (iii) after device deployment. Two pigs were immediately killed; six survived 4 weeks for repeat angiography and vessel harvest. RESULTS: Average vessel diameter before sheath insertion was 5.9 mm +/- 0.6 and 5.8 mm +/- 0.6 for vessels with Perclose and Sutura devices, respectively. After deployment of the Sutura device, there was a 44.7% (P =.001) mean diameter reduction from preprocedural diameters, compared to a 59.3% reduction (P <.001) with the Perclose device. After deployment of the Sutura device, there was a mean vessel diameter reduction of 14.1% (P =.53) versus the diameter immediately after sheath placement. After deployment of the Perclose device, there was a mean vessel diameter reduction of 43.8% (P =.05) versus the diameter immediately after sheath placement. At 4-week angiography, all vessels returned to their original diameters before sheath insertion. Pathologic examination showed mild adventitial fibrosis creating a "fibrous hood" surrounding the suture and vessel. CONCLUSIONS: Despite significant luminal compromise after device deployment, all vessels appeared normal on angiography at 4 weeks. Contrary to the normal angiographic findings, both devices incited periadventitial fibrosis, which created a fibrous hood around the suture and vessel.

Angiography↗
PubMed2003

Sample size estimation: how many individuals should be studied?

The number of individuals to include in a research study, the sample size of the study, is an important consideration in the design of many clinical studies. This article reviews the basic factors that determine an appropriate sample size and provides methods for its calculation in some simple, yet common, cases. Sample size is closely tied to statistical power, which is the ability of a study to enable detection of a statistically significant difference when there truly is one. A trade-off exists between a feasible sample size and adequate statistical power. Strategies for reducing the necessary sample size while maintaining a reasonable power will also be discussed.

Humans↗
PubMed2002

Predicting the presence of acute pulmonary embolism: a comparative analysis of the artificial neural network, logistic regression, and threshold models.

OBJECTIVE: The objective of this study was to determine whether an artificial neural network, a new data analysis method, offers increased performance over conventional logistic regression in predicting the presence of a pulmonary embolism for patients in a well-known data set. MATERIALS AND METHODS: Data from the 1064 patients who received an angiographically based diagnosis of pulmonary embolism in the Prospective Investigation of Pulmonary Embolism Diagnosis study were encoded using a previously described method. The 21 input variables represented abnormalities identified on each patient's ventilation-perfusion scan and chest radiograph. Two methods-an artificial neural network with one hidden layer and a multivariate logistic regression-were compared for accuracy in predicting the presence or absence of pulmonary embolism on subsequent pulmonary arteriography. RESULTS: No significant difference was observed between the two methods. Areas under the receiver operating characteristic curves +/- standard deviation were 0.78 +/- 0.02 for the artificial neural network model and 0.79 +/- 0.02 for the logistic regression model. Furthermore, use of these two methods resulted in no more diagnostic accuracy than did the use of a simple threshold model based only on the number of subsegmental perfusion defects, which was the dominant input variable. CONCLUSION: In the study population, the usefulness of data from ventilation-perfusion scans as predictors of the presence of a pulmonary embolism was similar for the three analytic methods, a finding that reinforces the importance of making comparisons to simpler or more established methods when performing studies involving complex analytic models, such as artificial neural networks.

Acute Disease↗
PubMedDate not supplied

Accuracy of breath-hold magnetic resonance imaging in preoperative staging of organ-confined renal cell carcinoma.

PURPOSE: To determine the accuracy of breath-hold magnetic resonance (MR) imaging for preoperative staging of patients with organ-confined (stage I) renal cell carcinoma. MATERIALS AND METHODS: Preoperative MR examinations of 43 patients (50 lesions) who underwent nephrectomy were reviewed. The MR examination consisted entirely of breath-hold sequences, and images were retrospectively evaluated by 2 blinded radiologists. Reviewers independently evaluated each case for findings that could affect the radiologic staging, particularly those that distinguish between organ-confined (stage I) and non-organ-confined (>stage II) disease. Each reviewer assigned a stage, and results were correlated with findings at surgery and pathologic examination. RESULTS: The difference between both reviewers and pathologic findings in evaluating an intact renal capsule (stage I) was statistically significant (P < 0.05) and resulted in a statistically significant difference between radiologic and pathologic staging (Wilcoxon test, P < 0.05). The kappa test demonstrated moderate agreement between radiologic and pathologic staging (82% and 80% for reviewers 1 and 2, kappa = 0.54 and 0.80, respectively) and substantial agreement (90%, kappa = 0.80) between the 2 reviewers in assigning a radiologic stage. CONCLUSION: Breath-hold MR imaging has an accuracy ranging between 80% and 82% in staging patients with organ-confined renal cell carcinoma, with substantial (90%) agreement between readers.

Adult↗
PubMedDate not supplied

Informatics in Radiology (infoRAD): radiology report entry with automatic phrase completion driven by language modeling.

Keyboard entry or correction of radiology reports by radiologists and transcriptionists remains necessary in many settings despite advances in computerized speech recognition. A report entry system that implements an automated phrase completion feature based on language modeling was developed and tested. The special text editor uses context to predict the full word or phrase being typed, updating the displayed prediction after each keystroke. At any point, pressing the tab key inserts the predicted phrase without having to type the remaining characters of the phrase. Successive words of the phrase are predicted by a trigram language model. Phrase lengths are chosen to minimize the expected number of keystrokes as predicted by the language model. Operation is highly and automatically customized to each user. The language model was trained on 36,843 general radiography reports, which were consecutively generated and contained 1.48 million words. Performance was tested on 200 randomly selected reports outside of the training set. The phrase completion technique reduced the average number of keystrokes per report from 194 to 58; the average reduction factor was 3.3 (geometric mean) (95% confidence interval, 3.2-3.5). The algorithm significantly reduced the number of keystrokes required to generate a radiography report (P <.00005).

Algorithms↗
PubMedDate not supplied

Collaboration system for radiology workstations.

Consultation between radiologists and referring physicians is part of routine medical practice. Nevertheless, a typical picture archiving and communication system contains no provision that will allow this critical interaction to occur on-line. The authors describe an image viewing system designed for real-time interactive consultation over the Internet. The system has two main components: an image viewer and a collaboration server. The image viewer connects to the collaboration server over an Internet-compatible network. Once the image viewer is connected, its display can be synchronized with that of another connected image viewer, so that radiologists can point out image findings and diagnoses in real time to remotely located physicians. The image viewer can retrieve images from any DICOM-compatible archive. In addition to standard image manipulation functions, the image viewer contains a new user interface for image annotation. Developed specifically for medical imaging, this user interface is activated by mouse actions instead of conventional on-screen controls, greatly improving the ease with which annotations can be created. The collaboration system is based on a simple yet flexible programming interface that can be readily generalized to other types of collaborative applications. The system was developed with the Java programming language because of Java's integrated support of Internet-compatible networking capabilities.

Humans↗