In quantitative measurements of the attenuation of ultrasound in 18 samples of variously normal, benign, and malignant breast tissue, we found significantly different ranges of attenuation. As observed in previous in vivo studies, with the exception of medullary carcinoma, malignant tissue produces the most attentuation of ultrasound in the frequency range of 1.5 to 3.0 MHz we employed. The apparatus, measurement method, results, and the possible causes of the differences in attenuation are presented.

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Three cases of left atrial myxoma were studied by echocardiography. In one case the atrial tumour was prolapsing through the mitral orifice into the left ventricular cavity; in the other two cases it was not. The angiocardiographic and operative findings correlated well with those from echocardiography. A systematic echocardiographic study is important; the suprasternal approach is useful in the echocardiographic exploration of the left atriu, especially for nonprolapsing tumours.

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