Asymmetric appearance of intracranial vessels on routine spin-echo MR images: a pulse sequence-dependent phenomenon.

PURPOSE: To determine the cause of right to left signal intensity differences arising from intracranial vessels during routine spin-echo axial MR imaging of the head. METHODS AND RESULTS: Using a normal imaging sequence in which the default directions of the frequency and phase axes were horizontal and vertical, respectively, differences in signal intensity arising from the vertebral arteries were observed in a healthy subject. With the exchange of the frequency and phase axes relative to the normal sequence, no signal intensity differences between the vertebral arteries were recognized. Other pulse sequence modifications, ie, the use of motion-compensating gradients and the reversed polarity of the frequency-encoding gradient, also resulted in variable appearances of the vertebral arteries, indicating that the right-to-left signal asymmetry of the vertebral arteries observed on the normal spin-echo image results from a pulse sequence dependent phenomenon. CONCLUSIONS: Frequency-encoding and slice-selection gradients both produce motion-induced phase shifts. These phase shifts depend on the angle between the direction of flow and that of the effective vector sum of these gradients. The asymmetric appearance of the vertebral arteries during normal spin-echo imaging was found to result from the angle dependence of motion-induced phase shifts. Awareness of this artifactual phenomenon is important to avoid confusing it with conditions such as stenosis/occlusion, dissection, or slow flow.     

Interaction of zinc with cadmium and copper on ossification of embryonic chick bone in tissue culture

Histological changes are shown of ossification induced by a simultaneous exposure to zinc and cadmium or to zinc and copper using embryonic chick femur in a culture system. Cadmium caused an atrophic change of the osseous tissue in the absence of zinc but caused an osteomalacic change with a partial degenerative change in the presence of zinc after a 6-day culture. Copper caused an atrophic change in the absence or presence of zinc. These observations were partly supported by the fact that the diaphysial calcium content was significantly decreased by zinc alone, and the decrease was unaffected by cadmium or copper. Zinc significantly decreased cadmium accumulation but not copper accumulation in the diaphysis. Thus, in spite of the inhibitory effect on calcification, zinc prevented a decrease in bone matrix formation caused by cadmium but not that by copper. Exposure of chick femur culture to zinc and cadmium induced changes consistent with osteomalacia, i.e., decreased mineralization of bone, with or without suppression of matrix formation. Exposure to zinc and copper, however, induced changes consistent with osteoporosis, i.e., decreased mineralization and matrix formation.     

Refractory gradient is responsible for the increase in ventricular vulnerability under sodium channel blockade.

BACKGROUND: Previous studies have shown that sodium channel (I(Na)) blockade increases ventricular vulnerability; however, there were differences in the degree of the increase. Because the vulnerable window (VW) is altered by the type of preshock refractory gradient (RG), the hypothesis was that the differences in the arrhythmogenesis of I(Na) blockade result from the different types of preshock RG employed. METHODS AND RESULTS: Simulations of regio(Na)l electric shock following constant pacing stimuli in 2-dimensional bidomain myocardial sheets under I(Na) blockade were conducted using 3 types of preshock RG: longitudinally tilted (LRG), transversely tilted (TRG), and non-tilted RG (NRG). The increase in the degree of I(Na) blockade almost linearly decreased the conduction velocity. The action potential duration in the LRG and TRG cases was non-linearly shortened with the increase in INa blockade because of electrotonic influences, whereas in the case of NRG it was slightly prolonged. In both LRG and TRG cases, the VW for reentry induction by electric shock was considerably widened by the INa blockade; however, this was not the case for NRG in which the VW was rather narrowed by the INa blockade. CONCLUSION: The type of preshock RG alters the degree of the increase in ventricular vulnerability under INa blockade.     

MRI evaluation of the patellar articular cartilage in patients with subluxation of the patella

In patients with subluxation of the patella, injury of the patellar articular cartilage is frequently observed and correct evaluation is important to manage these patients. We examined 11 patients with subluxation of the patella and five normal volunteers. In 12 patellofemoral joints of seven patients with subluxation of the patella, the abnormalities observed on MRI were compared with those on arthroscopy and/or at operation. MRI was performed with a Magnetom 1.5 T (Siemens) using the round surface coil. Pulse sequences were SE (TR 400 ms/TE 19 ms), FLASH (TR 320 ms/TE 15 ms FA 90 degrees and 40 degrees), and SE (TR 2000 ms/TE 26, 70 ms). We analysed MR findings of the 12 abnormal joints and 10 normal joints according to the following classification of abnormalities observed on arthroscopy. (1) normal appearance (n = 3 joints), (2) softening and fibrillation (n = 6), (3) fragmentation (n = 3), and (4) erosion to bone (n = 0). In only one of the six cases with softening and fibrillation observed on arthroscopy, MRI could visualize the thickening of patellar articular cartilage, but in all three cases with fragmentation observed on arthroscopy, MRI could visualize the thin inhomogenous cartilage with irregular surface. The combination of SE (TR 400 ms/TE 19 ms) and FLASH (TR 320 ms/TE 15 ms FA 90 degrees) are extremely effective pulse sequence to detect the abnormalities of patellar articular cartilage. We conclude that MRI is a useful noninvasive method of detecting advanced changes in patellar articular cartilage.     

Portal vein aneurysm demonstrated by blood pool SPECT.

Portal vein aneurysms are rare and are occasionally suggested by ultrasound and usually confirmed by invasive angiography. Such a case was diagnosed by scintigraphic studies, most importantly blood pool SPECT, which clearly separates it from hepatic cysts.     

Thallium perfusion and cardiac enzyme abnormalities in patients with familial hypertrophic cardiomyopathy

Twelve patients of five families with familial hypertrophic cardiomyopathy were examined. Within each family, the older patients showed dilation or diminished contraction of the left ventricle by echocardiography or angiocardiography more frequently than did younger patients. LDH1 fraction (lactic dehydrogenase isoenzyme) and MB-CPK (creatinine phosphokinase isoenzyme) were increased in 7 of 10 patients. Thallium-201 myocardial scintigraphy showed perfusion defect or hypoperfusion in 9 of 10 patient. Eleven cases demonstrated remarkable hypertrophy at the macroscopic level. Marked fibrosis was observed in all 5 of the 11 patients whose histologic findings were obtained. In two necropsy cases, disarray was found throughout the right and left ventricles and the pattern of fibrosis was massive. These findings were different from those of ordinary hypertrophic cardiomyopathy. It is possible that each patient with familial hypertrophic cardiomyopathy may develop more prominent thallium and enzyme abnormalities as he becomes older, regardless of whether he develops a dilated cardiomyopathy picture.