Accelerated coronary MRA by simultaneous acquisition of multiple 3D stacks.

The implementation and first in vivo results of a novel coronary magnetic resonance angiography (MRA) protocol allowing simultaneous acquisition of multiple geometrically independent 3D imaging stacks are presented. Each imaging stack is acquired in a separate cardiac phase using an individual magnetization preparation and navigator-based gating and prospective motion correction. Each stack covers one of the main coronary vessels. Thus, an improvement of scan efficiency was achieved, which was used in this study to reduce total scan time at standard image quality. Experiments performed in healthy volunteers and in patients using a two-stack approach yielded a total scan time reduction of 50% with an image quality equivalent to standard single-stack coronary MRA.

Free-breathing cardiac MR imaging: study of implications of respiratory motion--initial results.

The respiratory motion of several anatomic regions (right hemidiaphragm, left ventricle of the heart, chest wall, abdominal wall) was investigated during free breathing in 10 healthy volunteers by using multinavigator technology and real-time magnetic resonance (MR) imaging. The respiratory motion shows hysteretic effects, which are strongly subject dependent and might have some effect on the quality of cardiac MR images.

Toe blood pressure. A valuable adjunct to ankle pressure measurement for assessing peripheral arterial disease.

Ankle pressure measurements fail to reflect the severity of peripheral ischemia when the underlying vessels are calcified or when there is extensive pedal or digital arterial disease. These problems may be obviated by measuring pressures at toe level. In this study, toe pressures were correlated with ankle pressures, clinical symptoms, and the presence or absence of diabetes in 294 limbs. The relationship of toe pressures to healing of ulcers or amputations of the foot was investigated in 58 limbs. Measurements were made with a digital pneumatic cuff and a photoplethysmograph. The ability of absolute toe pressure, ankle/brachial index, toe/brachial index, toe/ankle index, and the brachial pressure minus the toe pressure to differentiate between asymptomatic, claudicating, and ischemic limbs was determined. The toe/brachial index, arm minus toe pressure, and the absolute toe pressure had an average sensitivity and specificity of 85% and 88% for asymptomatic limbs and 89% and 86% for ischemic limbs. A toe pressure greater than 30 mmHg was indicative of a good healing potential, and ankle pressure less than 80 mmHg was associated with poor healing. The correlation between ankle and toe pressures was essentially the same in both diabetic (r = 0.60) and non-diabetic limbs (r = 0.62).

Hemodynamic studies of digital and extremity replants and revascularizations.

Blood pressure, blood flow, skin temperature, pulse contour, and sympathetic nerve activity were investigated by noninvasive methods in 33 fingers, five arms, and one foot that had been replanted or revascularized 2 to 30 months previously. Results from the operated parts were contrasted with those from the same part on the contralateral normal extremity and with those obtained from normal controls. Mean blood pressure in operated fingers (97 +/- 18 mm Hg) was significantly lower than that in nonoperated (114 +/- 16 mm Hg) and control (115 +/- 17 mm Hg) fingers. Mean blood flow in operated fingers (16 +/- 100 ml/100 ml/min) was significantly less than that in nonoperated (23 +/- 11 ml/100 ml/min) and control (28 +/- 20 ml/100 ml/min) fingers. In 80% of the studies, blood pressure and blood flow were less on the operated side than on the nonoperated side; however, 75% of the blood pressure determinations and all of the blood flows fell within the 95% confidence limits of the control values. Skin temperatures were not decreased and sympathetic activity had returned in 91% of the fingers. It is concluded that the perfusion of tissues surviving replantation or revascularization usually is within normal limits but often is reduced when compared to that of normal tissues of the same individual.

Secretory and ultrastructural responses of hyperfunctioning human parathyroid tissues to varying calcium concentration and vinblastine.

Parathyroid hormone (PTH) secretion from abnormal hyperfunctioning human parathyroid tissues was studied in vitro to determine whether abnormal tissues were responsive to changes in calcium concentration and what role their subcellular organelles played in secretion. Hyperfunctioning tissues from one patient with secondary parathyroid hyperplasia, four patients with parathyroid adenomas, and one patient with parathyroid carcinoma were incubated in media containing low calcium (0.75 mM), normal calcium (1.5 mM), high calcium (3.0 mM), or vinblastine (0.01 mM), a microtubular disrupter. Also, in order to correlate ultrastructural responses with PTH secretion, after incubation tissues of one adenoma were objectively quantitated by stereologic techniques. Low calcium consistently stimulated mean PTH secretion from hyperplastic and adenomatous tissue, but only during the 1st hour of secretion. Low calcium inconsistently stimulated carcinomatous tissue. High calcium suppressed mean PTH release from all tissues. Vinblastine did not consistently inhibit secretion from adenomatous or hyperplastic tissue. Ultrastructural analysis of adenomatous tissue showed a sparsity of granules (0.87 per cent of cellular volume) compared to previously studied bovine tissues. Low calcium significantly increased the volume fraction of pinocytotic vesicles to 300 per cent (p less than 0.01) and reduced the surface area of straight (inactive) membrane to 60 per cent (p less than 0.01) of the normal calcium control. Secretion granules, when present, were adjacent to submembrane vesicles. The number and structure of microtubules were not changed by low or high calcium or vinblastine. Our findings indicate that parathyroid adenomas and hyperplastic tissues can respond acutely to low calcium stimulation and high calcium suppression. However, the acute response to low calcium stimulation may not be sustained in some cases because of limited storage of hormone. The increase in pinocytosis in low calcium-stimulated tissue suggests a coupling of exocytosis with membrane endocytosis, possibly related to membrane recycling. Our findings with vinblastine suggest that microtubular integrity is not a prerequisite for basal PTH secretion in adenomatous tissue.