The distribution of iron in the brain was analyzed using high field strength (1.5 T) magnetic resonance (MR) imaging in 14 healthy control individuals and six patients with Parkinson plus syndromes (multisystem atrophy and progressive supranuclear palsy) who were unresponsive to antiparkinsonian therapy. The normal topographic distribution of iron in the brain as indicated by high field MR images coincided precisely with the distribution of iron in the brain as determined by Perls staining for ferric iron. In Parkinson plus syndromes, there were abnormally increased concentrations of iron (decreased T2 relaxation times) in the putamen, and less prominent increases in the caudate nucleus and lateral pars compacta of the substantia nigra. In high field strength MR images of normal patients, the decreased signal intensity in the globus pallidus is more prominent than that of the putamen. In MR images of patients with Parkinson plus syndromes, the decreased signal intensity of the putamen is more prominent than that of the globus pallidus.
The ability of MRI to detect parathyroid gland enlargement was assessed using 1.5-T systems and surface coil reception. Nine patients with primary hyperparathyroidism were studied before surgical neck exploration. Five-millimeter-thick axial images were obtained from the thyroid cartilage to the sternal notch. Both T1 and T2 contrast-weighted spin-echo sequences were performed in most cases. MRI correctly identified six out of seven parathyroid adenomas. In the false-negative case, T2 contrast-weighted sequences were not performed for technical reasons. In the one case of surgically proven parathyroid hyperplasia, a lesion identified by MRI as a parathyroid adenoma coincided at surgery with the largest of three hyperplastic parathyroid glands. A single case demonstrated a potential pitfall in the search for ectopic parathyroid glands: A large colloid cyst in the posterior portion of the thyroid gland showed signal characteristics indistinguishable from a parathyroid adenoma. The enlarged parathyroid glands were best visualized on T2 contrast-weighted sequences, with the lesions demonstrating greater signal than surrounding tissues.
Results The average age of the older subjects was 57.1+/-3.4 years. Resting heart rate of 63+/-8 bpm increased to 95+/-12 bpm during exercise for a percent increase of 51+/- 3%. Quantitative comparisons of flow rate, WSS, and oscillations in flow and WSS are shown in Figure 2. While there were no statistical differences in flow and flow oscillations between the age groups, WSS was lower in the supraceliac aorta of the older subjects at rest as compared to the younger subjects (Young=3.5+/-0.8, Old=2.0+/-0.7 dynes/cm 2 , p<0.001). The older population also had significantly higher shear oscillations (OSI) at the supraceliac (Young=0.01+/-0.01, Old=0.07+/- 0.05, p<0.001) and infrarenal (Young=0.13+/-0.09, Old=0.25+/-0.12, p<0.05) levels at rest. During exercise, the older subjects experienced greater WSS in the infrarenal aorta as compared the younger subjects (Young=5.2+/-1.3, Old=16.5+/-5.1 dynes/cm 2 , p<0.05), and also experienced elimination of all oscillations. Discussion The increases in flow and WSS and elimination of flow and shear oscillations in the abdominal aorta as a result of cycling exercise, as measured in this study, support the hypothesis that lower limb exercise moderates the unfavorable hemodynamic conditions that correlate with the localization of atherosclerotic disease. Even at the relatively low level of exercise corresponding to a 50% increase in heart rate, a 6-fold increase of flow into the lower extremities was observed for both young and older subject groups. Dilation of the aortic lumen with increasing age may cause the region of low mean WSS, observed only in the infrarenal region of the younger subjects, to extend superiorly in the aorta at rest for the older subjects. Although oscillations in WSS were found to be greater in the older subjects as compared to the younger subjects at the supraceliac and infrarenal levels of the aorta at rest, exercise served to eliminate these oscillations just as in the younger subjects, and the mean WSS was increased more dramatically in the older subjects. These findings support the hypothesis that even low levels of exercise are hemodynamically athero-protective for the abdominal aortas of healthy subjects aged 50 to 70, and that these benefits may be more important for older subjects than for younger subjects due to their more adverse baseline conditions at rest.
To determine the relationship of phase changes and abnormalities of ventricular contraction and conduction, we performed phase image analysis of blood pool scintigrams in 29 patients. Eleven patients had no evidence of blood pool contraction or ECG conduction abnormalities, four had contraction abnormalities, seven had abnormal conduction and seven had abnormalities of both variables. The phase delay generally related to the degree of contraction abnormality. The mean phase delay in hypokinetic segments differed from that in normokinetic segments in the same patient (p less than 0.025), the phase delay of akinetic and dyskinetic segments differed from that in normokinetic segments (p less than 0.001) and the phase delay in dyskinetic segments differed from that in akinetic segments (p less than 0.005), but there was a significant overlap in the phase delay in normal and hypokinetic segments. Also, in patients with conduction abnormalities, the minimal associated regional phase delay presented a phase dispersion and a pattern of contraction consistent with the pattern of conduction and different from normal. A single study performed both at rest and with stress demonstrated the effect of heart rate on phase assessment and confirmed the independent effects of contraction and conduction on phase delay. Acquisition and analytic methods should add significantly to the resolution of the phase method.
