PubMed · 824506
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R Gorlin. 1976. Investigative methods.. https://pubmed.ncbi.nlm.nih.gov/824506/
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Laser-polarized gases (3He and 129Xe) are currently being used in magnetic resonance imaging as strong signal sources that can be safely introduced into the lung. Recently, researchers have been investigating other tissues using 129Xe. These studies use xenon dissolved in a carrier such as lipid vesicles or blood. Since helium is much less soluble than xenon in these materials, 3He has been used exclusively for imaging air spaces. However, considering that the signal of 3He is more than 10 times greater than that of 129Xe for presently attainable polarization levels, this work has focused on generating a method to introduce 3He into the vascular system. We addressed the low solubility issue by producing suspensions of 3He microbubbles. Here, we provide the first vascular images obtained with laser-polarized 3He. The potential increase in signal and absence of background should allow this technique to produce high-resolution angiographic images. In addition, quantitative measurements of blood flow velocity and tissue perfusion will be feasible.
The purpose of the present work is to establish a basic knowledge about the scaling properties of the placenta's arterial tree. For this end we have analysed X-ray angiograms of 22 normal arterial trees by box counting. All the investigated arterial trees scale closely according to a power-law over a one decade wide range of scales. Perfectly self-similar fractals, of the same resolution as our representation of the arterial tree, do not follow a power-law more closely. The results support the hypothesis that a mechanism or rule--as regular as those which dictate the structure of perfectly self-similar fractals--also determines fundamental aspects of the arterial tree's morphology.
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