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D L Levin

Publications and source records attributed to D L Levin.

At least 19 recordsLinked to original sources
PubMed2006

Quantification of regional pulmonary blood flow using ASL-FAIRER.

Pulsed arterial spin labeling (ASL) techniques have been theoretically and experimentally validated for cerebral blood flow (CBF) quantification. In this study ASL-FAIRER was used to measure regional pulmonary blood flow (rPBF) in seven healthy subjects. Two general ASL strategies were investigated: 1) a single-subtraction approach using one tag-control pair acquisition at an inversion time (TI) matched to the RR-interval, and 2) a multiple-subtraction approach using tag-control pairs acquired at various TIs. The mean rPBF averaged 1.70 +/- 0.38 ml/min/ml when measured with the multiple-subtraction approach, and was approximately 2% less when measured with the single-subtraction method (1.66 +/- 0.24 ml/min/ml). Assuming an average lung density of 0.33 g/ml, this translates into a regional perfusion of approximately 5.5 ml/g/min, which is comparable to other measures of pulmonary perfusion. As with other ASL applications, a key problem with quantitative interpretation of the results is the physical gap between the tagging region and imaged slice. Because of the high pulsatility of PBF, ASL acquisition and data analysis differ significantly between the lung and the brain. The advantages and drawbacks of the single- vs. multiple-subtraction approaches are considered within a theoretical framework tailored to PBF.

Adult↗
PubMed2001

Evaluation of regional pulmonary perfusion using ultrafast magnetic resonance imaging.

An ultrafast MR sequence was used to measure changes in signal intensity during the first pass of intravascular contrast through the pulmonary circulation. From this, mean transit time, relative blood volume, and relative blood flow were calculated. Data were collected in an isogravitational plane in six healthy subjects. A slight but significant gradient in transit time was present, with faster times at the lung apex. A significant decrease in blood volume, compared with the lung base, was also seen in the apex. Significant decreases in blood volume and blood flow, compared with central portions of the lung, were seen in the lung periphery. Six additional subjects were imaged along a gravitational plane. A significant gradient in transit time was seen, with faster transit in dependent regions of the lung. MRI is able to evaluate regional differences in pulmonary perfusion with high spatial and temporal resolution. Magn Reson Med 46:166-171, 2001.

Blood Volume↗
PubMed2001

Relationship of demographic and clinical factors to free and total prostate-specific antigen.

OBJECTIVES: To characterize the role of demographic and clinical parameters in the measurements of prostate-specific antigen (PSA), free PSA (fPSA), and percent free PSA (%fPSA). METHODS: This was a cohort study of volunteers to a randomized screening trial. A central laboratory determined PSA and fPSA for the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. A baseline evaluation of free and total PSA was done for 7183 white, black, Asian, Hispanic, and other male volunteers, aged 55 to 74 years. Comparisons were made across racial and ethnic groups and across a set of clinical parameters from a baseline questionnaire. RESULTS: The median levels of serum PSA were less than 2.1 ng/mL in each age-race grouping of the study participants. The levels of free and total PSA were higher in black (n = 868, 12%) participants than in white (n = 4995, 70%) and Asian (n = 849, 11.8%) participants. Individuals who identified themselves as ethnically Hispanic (n = 339, 4.7%) had median PSA levels higher than whites who were not Hispanic. The free and total PSA levels increased with age, particularly among men 70 to 74 years old. However, the %fPSA levels showed less variation among the four racial groups or by age. The free and total PSA levels were higher among those who had a history of benign prostatic disease. CONCLUSIONS: Demographic (age and race/ethnicity) and clinical (history of benign prostatic disease) variables had a moderate effect on the measures of PSA and fPSA and very little effect on %fPSA.

Aged↗
PubMed2001

Quantification of pulmonary perfusion with MR imaging: recent advances.

Recent advances in magnetic resonance pulmonary perfusion imaging are reviewed, focusing on magnetic resonance perfusion imaging using gadolinium contrasts agents or spin labeling of blood using naturally flowing spins as the source of intravascular signal. These recent developments in magnetic resonance imaging have made it possible to analyze data quantitatively which holds significant potential for clinical imaging of lung perfusion and opens windows to functional MR imaging of the lung. We believe that fast magnetic resonance functional imaging will play an important role in the assessment of pulmonary function and the pulmonary disease process.

Contrast Media↗
PubMed2001

Impact of screening on incidence and mortality of prostate cancer in the United States.

The potential confounding influence of changing treatment patterns and misattribution bias make a definitive conclusion about the link between PSA screening and mortality rates tentative at best. At least some of the mortality decline since 1991 appears likely to be due to screening, but the precise magnitude of the screening effect is difficult to estimate. The possible reduction in mortality due to screening, while uncertain, must be weighed against the substantial decrements in treatment-specific health outcomes (32-34) among men treated for clinically localized tumors typically detected by screening. Population data and ongoing screening trials in the United States and Europe (24, 35) will be complementary in the final determination of the relative contribution of the impact of screening versus other causes on recent mortality trends.

Aged↗
PubMed2000

Magnetic resonance imaging of the thorax. Past, present, and future.

Magnetic resonance imaging is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

Humans↗
PubMed2000

Coordination and management of a large multicenter screening trial: the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial.

The Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial is a large and complex multi-institutional, multifaceted organization with a 20-year horizon. The implementation of the trial began with the creation of an organizational structure that supports strong leadership, cooperation, and effective communication among the trial collaborators including an operational framework for the development, review, and pretest of instruments, data collection, and management procedures; the setting of high-quality standards for training of trial staff; and the development of a comprehensive assessment plan for evaluation of all trial activities. This paper describes the process and methods used in the coordination and management of the PLCO trial. These include the role of the steering committee and its subcommittees and working groups, the establishment of regular and ad hoc communications among collaborators, the training of screening center coordinators and examiners, the PLCO manual of operations and procedures, and the development and implementation of a comprehensive quality assurance plan.

Colorectal Neoplasms↗
PubMed1999

Quantitative assessment of pulmonary perfusion with dynamic contrast-enhanced MRI.

The feasibility of qualitative assessment of pulmonary perfusion using dynamic contrast enhanced MRI with ultra-short TE has recently been demonstrated. In the current study, quantitative analysis was attempted based on the indicator dilution principle using a pig model of pulmonary embolism. The results were compared with the absolute pulmonary perfusion obtained with colored microspheres. The inverse of apparent mean transit time (1/tau(app)), distribution volume (V), and V/tau(app) were correlated well with the absolute lung perfusion. This study demonstrates that MR has the potential to evaluate pulmonary perfusion quantitatively. Magn Reson Med 42:1033-1038, 1999.

Adult↗
PubMed1999

Magnetic resonance imaging of the thorax. Past, present, and future.

Magnetic resonance is a valuable modality of extreme flexibility for specific problem-solving capability in the thorax. This article reviews MR applications in the imaging of great vessels, which are currently the most important applications in the thorax; other established applications in the thorax; and pulmonary functional MR imaging.

Aortic Diseases↗
PubMed1999

Distribution of thoracic lymphadenopathy in sarcoidosis using computed tomography.

The authors used chest computed tomography to determine the distribution of pulmonary lymphadenopathy in 40 patients with sarcoidosis. Using the American Thoracic Society lymph node map, the number and distribution of significant lymph nodes was calculated. Overall, lymphadenopathy was identified in 39 of the 40 patients. Mediastinal adenopathy was present in 38 patients, and hilar adenopathy was present in 27. Commonly involved nodal stations were 4R, 5, 7, 10R, 11R, and 11L, and little involvement was seen in stations 1, 6, and 14. An understanding of the common sites of adenopathy in sarcoidosis is useful when assessing adenopathy in patients without a known diagnosis.

Female↗
PubMed1999

Pulmonary disorders: ventilation-perfusion MR imaging with animal models.

PURPOSE: To demonstrate the capability of magnetic resonance (MR) imaging to assess alteration in regional pulmonary ventilation and perfusion with animal models of airway obstruction and pulmonary embolism. MATERIALS AND METHODS: Airway obstruction was created by inflating a 5-F balloon catheter into a secondary bronchus. Pulmonary emboli were created by injecting thrombi into the inferior vena cava. Regional pulmonary ventilation was assessed with 100% oxygen as a T1 contrast agent. Regional pulmonary perfusion was assessed with a two-dimensional fast low-angle shot, or FLASH, sequence with short repetition and echo times after intravenous administration of gadopentetate dimeglumine. RESULTS: Matched ventilation and perfusion abnormalities were identified in all animals with airway obstruction. MR perfusion defects without ventilation abnormalities were seen in all animals with pulmonary emboli. CONCLUSION: Ventilation and perfusion MR imaging are able to provide regional pulmonary functional information with high spatial and temporal resolution. The ability of MR imaging to assess both the magnitude and regional distribution of pulmonary functional impairment could have an important effect on the evaluation of lung disease.

Airway Obstruction↗
PubMed1999

Imaging techniques for pleural space infections.

Radiology plays a central role in the evaluation and management of pleural space infections. Conventional radiographs, including decubitus films, remain the primary radiological study in the detection of parapneumonic pleural effusions. Loculated collections develop as a result of visceral-to-parietal pleural adhesions and appear radiographically as longitudinally oriented, lenticular-shaped opacities. Contrast-enhanced computed tomography scans accurately distinguish lung abscess from loculated empyema and provide a global view of the extent and complexity of the pleural collection. Sonography allows portable bedside examination of critically ill patients and is useful in the detection and sampling of small effusions. Real-time ultrasound evaluation of pleural collections accurately determines the size and nature of the effusion and may be useful in predicting the success of thoracentesis. As cross-sectional studies are obtained in the majority of patients with complex pleural space infection and provide valuable information, the precise clinical utility of computed tomography scans and ultrasound in these patients remains undetermined.

Humans↗
PubMed1999

Ventilation-perfusion MR imaging of the lung.

The assessment of regional ventilation in human lungs is important for the diagnosis and evaluation of a variety of pulmonary disorders, including pulmonary emphysema, diffuse lung disease (e.g., sarcoidosis, and pulmonary fibrosis), lung cancer, and pulmonary embolism. This article introduces new MR imaging techniques of pulmonary ventilation and perfusion that will provide a framework for assessing regional pulmonary functions of the lung.

Adult↗
PubMed1998

Oxygen enhanced MR ventilation imaging of the lung.

The current work is a continuation of a new MRI technique that was proposed for the non-invasive assessment of regional lung ventilation using inhaled molecular oxygen as a T1 contrast agent. Several improvements of this technique are described in this work. The signal-to-noise ratio in the ventilation-scan images was optimized using a centrically reordered single-shot RARE sequence with a short effective echo time and short inter-echo spacing. The contrast-to-noise ratio was improved using an optimized inversion delay time. The optimized MR-ventilation-scan was successfully performed in healthy volunteers and in an animal model with airway obstruction. The experimental results demonstrate the feasibility and clinical potential of the MR ventilation imaging technique for assessment of regional pulmonary function.

Airway Obstruction↗
PubMed1998

A national HIV community cohort: design, baseline, and follow-up of the AmFAR Observational Database. American Foundation for AIDS Research Community-Based Clinical Trials Network.

This article describes the design, methodology, baseline distributions, and general follow-up characteristics of the American Foundation for AIDS Research (AmFAR) National Observational Database (ODB) Project including the benefits and limitations of collecting information on a large simple cohort in the HIV community setting. The study prospectively followed 15,611 HIV-positive men and women and collected longitudinal and cross-sectional data on demographics, medical conditions, drug therapies, laboratory parameters, and survival. Participants were followed between October 1990 and December 1993 by 252 community-based sites coordinated by 22 centers in the Community-Based Clinical Trials Network (CBCT Network) throughout the United States (including Puerto Rico) and Toronto, Canada. The ODB provided quantitative information on a national level needed to track the HIV epidemic and plan clinical trials conducted through the Network, and to provide sites with local databases to monitor patients and facilitate access to therapies in clinical trials. Overall, the ODB contains information on 1,925 women (12%) and 13,686 men (88%), 60% white, 20% African American, 17% Latino/Hispanic, with 56,254 baseline and follow-up forms, a median follow-up of about 12 months, a 16% loss-to-follow-up, and an 11% mortality rate. AmFAR plans to place the ODB in the public domain.

Adolescent↗