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Biomedical subjects

E J Potchen

Publications and source records attributed to E J Potchen.

At least 37 records · Page 2Linked to original sources
PubMed1992

Physical principles and application of magnetic resonance angiography.

This paper reviews the physical principles of magnetic resonance angiography (MRA) acquisition methods, explains image presentation strategies for MRA, and discusses the advantages and disadvantages of various MRA methods. These methods include the time-of-flight, phase contrast, and black blood techniques. The essential goal of each of these flow imaging methods is to maximize signal differences between flowing and stationary tissues in order to provide morphological and physiological information.

Blood Vessels↗
PubMed1992

Magnetic resonance angiography in intracranial vascular disease.

Magnetic resonance angiography (MRA) offers a noninvasive alternative for studying normal and pathological blood vessels within the brain. Insights from important clinical aspects of intracranial vascular disease enable the effective application of MRA. Several MRA techniques have demonstrated clinical utility for the detection and characterization of intracranial vascular pathology. Clinical protocols should comprise combinations of time-of-flight and phase-contrast acquisitions to achieve diagnostic sensitivity.

Brain Neoplasms↗
PubMed1991

Intra- and extracellular pH of the brain in vivo studied by 31P-NMR during hyper- and hypocapnia.

Studies were performed to determine the pH relationships among the extracellular, intracellular, and arterial blood compartments in the brain in vivo. Resolution of the extracellular monophosphate resonance peak from the intracellular peak in 31P nuclear magnetic resonance (NMR) spectra of sheep brain with the calvarium intact enabled pH measurement in these respective compartments. Sheep were then subjected to both hyper- and hypoventilation, which resulted in a wide range of arterial PCO2 and pH values. Linear regression analysis of pH in these compartments yielded slopes of 0.56 +/- 0.05 for extracellular pH (pHe) vs. arterial pH, 0.43 +/- 0.078 for intracellular pH (pHi) vs. pHe, and 0.23 +/- 0.056 for pHi vs. arterial pH. These data indicate that CO2 buffering capacity is different and decreases from the intracellular to extracellular to arterial blood compartments. Separation of the extracellular space from the vascular space may be a function of the blood-brain barrier, which contributes to the buffering capability of the extracellular compartment. A marked decrease in the pH gradient between the extracellular and intracellular space occurs during hypercarbia and may influence mechanisms of central respiratory control.

Animals↗
PubMed1990

Direct relationship between proton T2 and exercise intensity in skeletal muscle MR images.

Exercise selectively increases the signal intensities (SI) of active muscles in T2-weighted magnetic resonance (MR) images. If these SI increases are graded with exercise intensity, the identification of muscle recruitment patterns may be possible using MR imaging. The purpose of this study was to determine the effect of force generation during exercise on muscle T2 values. Also, we examined the effects of extracellular fluid volume (ECV) expansion on muscle T2 values. Transaxial midcalf images were collected before and after exercise on eight volunteers in a 1.5T GE magnet using a standard spin echo sequence. Exercise consisted of three consecutive bouts of ankle dorsiflexion against graded loads. Three subjects also underwent brief bouts of lower leg venous occlusion (ECV expansion) during and in addition to the exercise protocol. T2 values for the dorsiflexors significantly increased after exercise. Greater mean force produced during exercise caused greater increases in T2 after exercise (T2 = 29.6 +/- 0.9 X Force). Exercise and venous occlusion caused equivalent increases in muscle cross-sectional area. These equivalent increases in ECV were not accompanied by equivalent increases in muscle T2; venous occlusion alone caused less than a 5% increase in T2 while exercise caused a 14% to 25% increase. Consequently, a direct relationship between increases in T2 and in ECV after exercise was not established. Venous occlusion during exercise, however, did significantly augment the increase in T2 and ECV of the anterior compartment muscles. Contrast enhancement among muscles after exercise in T2-weighted MR images is dependent on generated force during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report.

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.

Adolescent↗
PubMed1990

Use of mammography in screening for breast cancer.

Recognizing the enormous impact that quality breast screening mammography can have on reducing breast cancer deaths, we need to determine when women's and physician's perceived restrictions for mammography examination impede the progress of its use for early cancer detection. A uniform system should emphasize valid communication and education between women and their physicians. Women seek to have a voice in their medical treatment. Yet that responsibility has an emotional price. Physicians and patients must decide together on the most appropriate strategies to enhance communication and adopt specific guidelines they will adhere to, to detect and cure early breast cancer. Women must be educated about breast screening mammography, and physicians must increase their efforts to proclaim its importance. Women need be assured the trend is toward using the most modern mammographic techniques. Quality medical care is medicine's purpose and in women's best interest. At present, no other diagnostic method is equivalent to mammography and capable of providing an equivalent impact on improving the detection and cure rate of breast cancer. Despite medical activities designed to reduce uncertainty in medicine, scientific evidence has not provided systematic answers as to the "best" way to approach issues of quality, cost, accessibility, or communication for breast screening mammography. No particular expert opinion or preference prevails for breast screening protocols. What is needed is adoption of a multidisciplinary approach, educating and motivating women and physicians to participate in breast screening activities. With trends directed toward high-volume breast screening operations, low-cost, quality mammography must be available and be impeccably performed. Some activities are natural subjects for financial quantification. It is objectionable to assume, however, that we can accurately place and agree on dollar amounts alone to represent the costs and benefits of screening mammography. The gaps between practices and attitudes about the benefits, risks, and costs of screening mammography suggest that people are not satisfied with the way physicians, women, influential groups, or regulatory agencies are balancing all of the elements. Better communication must exist between physicians and their peer groups involved in performing responsible mammography. Better communication must be achieved between physicians and women to take advantage of the usefulness of quality breast screening mammography. High-quality screening programs must be linked to third-party reimbursement and to legislation, if we are to make a difference. Screening mammography deserves our medical, economic, social, and political attention and action.

Adult↗
PubMed1990

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report.

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.

Adolescent↗
PubMed1987

Utilization of screening mammography: comparison of different physician specialties.

Data obtained on 426 consecutive patients referred to a breast center by 122 physicians, including family practitioners, general surgeons, and other specialists, showed that the obstetricians-gynecologists referred the greatest average number of patients per physician, with more than 50% of these referrals for screening mammography. Internists referred fewer patients by nearly a factor of ten, with only one-third of these patients referred for screening mammography. Internists may be the weakest link in the utilization of screening mammography.

Adolescent↗
PubMed1987

The detection and cure of breast cancer.

The appropriate use of screening mammography can significantly decrease deaths from breast cancer. Physicians and patients must become more vigilant in using available diagnostic modalities if we are to improve upon the survival of patients with breast cancer.

Biopsy↗