Although cross-sectional magnetic resonance examination of the head and body is useful for screening large regions of tissue, subsectional regions of the head and body often need to be examined. Orthogonally directed, selectively irradiated planes with different flip angles produce a spatially limited signal region from which two- or three-dimensional volume images can be reconstructed. Images with limited fields-of-view can be acquired in reduced imaging time. We present a general description of this technique. These subsectional or "inner volume" images eliminate respiratory motion artifacts by excluding moving tissues from the imaged volume. A result of this technique is a high signal from rapid pulsatile blood flow, produced without cardiac gating the pulse sequence.

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This paper represents a preliminary study of the effects of regional temperature distribution in two-dimensional nuclear magnetic resonance (NMR) T1 imaging. It is found, as expected, that variations in local temperature appear as variations in the corresponding T1 image. The potential use of NMR T1 imaging in temperature measurements is evaluated in the case of water and blood samples. Using containers where the temperature could be either known or directly controlled with reasonable accuracy, images are obtained with samples having at least two regions at different temperatures. As expected, T1 is found to vary linearly with 1/T over the range of 0 degrees C to about 40 degrees C for blood. The potential use of T1 imaging in hyperthermia applications is also discussed.

Albumin is a macromolecule that remains largely confined to the vascular space after intravenous administration. Human serum albumin was paramagnetically labeled by covalently binding from nine to 18 gadolinium-DTPA (diethylenetriaminepentaacetic acid) chelates per protein molecule. This conjugate was tested in varying doses for in vivo biodistribution and effectiveness in tissue relaxation. After intravenous injection of the agent in rats, T1 relaxation times were significantly reduced in samples of the blood and in lung, heart, spleen, kidney, and brain tissue. These effects persisted at a relatively constant level for the next 30 minutes. In vivo magnetic resonance imaging of the heart and lungs of rats and rabbits confirmed the prolonged contrast-enhancing effect of the labeled albumin. These preliminary studies indicate that paramagnetically labeled macromolecules that distribute in the intravascular space may be effective for MR imaging evaluation of tissue blood volume.