Gadolinium-DTPA complex (Gd-DTPA) is a potential clinical magnetic resonance (MR) contrast agent that enhances images primarily by decreasing spin-lattice relaxation time (T1) in tissues in which it localizes. This study was designed to determine the immediate tissue distribution of intravenously administered Gd-DTPA in selected organs of interest as a function of administered dose and tissue Gd-DTPA concentration. An intravenous bolus of Gd-DTPA with a tracer quantity of Gd-153 was administered to three groups of rabbits at the following doses: 0.01 mM/kg (n = 6); 0.05 mM/kg (n = 6); 0.10 mM/kg (n = 6). A control group received sham injections. Five minutes after Gd-DTPA was administered, all animals were killed; samples of serum, lung, heart, kidney, liver, and spleen were analyzed in a 0.25 T MR spectrometer to measure T1, and then in a gamma well counter to determine tissue concentration of Gd-DTPA. Tissue distribution (per cent dose/tissue weight in g) at five minutes after injection was proportionally constant over the range of doses given. Tissue concentration varied linearly with injected dose (r greater than 0.98 for all tissues). Relaxation rate (1/T1) varied linearly with injected dose and with tissue Gd-DTPA concentration (r greater than 0.97 for all tissues). The order of tissue relaxation rate response to a given dose was: kidney greater than serum greater than lung greater than heart greater than liver greater than spleen. We conclude that because of its extracellular distribution and linear relaxation rate versus concentration relationship, Gd-DTPA enhancement in MR images may be a good marker of relative organ perfusion.

Seventy-three fluid samples obtained via percutaneous aspiration and drainage were analyzed by proton magnetic resonance spectroscopy. The fluids included abscess contents, bile, ascitic fluid, cyst and pseudocyst fluid, urine, hematomas, pleural fluid, lymphoceles, seromas, cerebrospinal fluid, pancreatic ductal fluid, and necrotic tumor. They were grouped by their clinical etiology and analyzed with respect to their inherent magnetic relaxation properties. In addition, some of the samples were tested for the following chemical parameters which were correlated with T1 and T2 values: total protein content (n = 36), osmolality (n = 24), specific gravity (n = 11), and amylase levels (n = 23). A large overlap was found in the T1 (spin-lattice) and T2 (spin-spin) relaxation times of the fluids; however, the mean T1 values of abscesses and hematomas were significantly lower than those of other fluids. Similar variability was seen in T2 values, though hematomas and abscesses again could be distinguished by shorter relaxation times. The spin-lattice (1/T1) and spin-spin relaxation rates (1/T2) showed a moderate correlation with total protein content, osmolality, and specific gravity. It is concluded that there is some predictability to MR analysis of body fluids, though the overlap in magnetic relaxation times limits specificity.

Hemodynamic effects of pulmonary arterial injections of ionic (sodium methylglucamine diatrizoate) and non-ionic contrast media (iohexol) were compared in 9 anesthetized dogs which were maintained with an open thorax in a resting control state. Both were found to increase pulmonary arterial pressure and cardiac output. In addition, both resulted in decreased systemic vascular resistance, though the effect was significantly less with the non-ionic agent. Aortic pressure did not change with the non-ionic agent but fell drastically with the ionic agent. Contrary to prevailing beliefs, the predominant response of the pulmonary circulation to contrast media was a fall rather than a rise in pulmonary vascular resistance.

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The acute hemodynamic effects of two paramagnetic contrast materials, manganese chloride and gadolinium-DTPA, were examined in dogs using ultrasonic dimension gauge crystals. Slow infusions (more than 15 minutes) of MnCl2 (0.1 mm/kg) or Gd-DTPA (0.1 mm/kg) via an infusion pump had no significant hemodynamic effects. When given in just over 1 minute, Gd-DTPA produced elevated left ventricular (LV) end diastolic pressure and minor dilation of the ventricle and slowed diastolic filling. MnCl2, given rapidly, reduced systemic vascular resistance, resulting in hypotension. It also reduced LV volume and had less marked diastolic effects (probably secondary to the amount of hypotension created). With both agents, these side effects waned after 5-10 minutes. It is concluded that both Gd-DTPA and MnCl2 can be given safely in 0.1-mm/kg doses when administered as a slow, continuous infusion. The acute hemodynamic effects of Gd-DTPA are consistent although minor. While the acute effects of Gd-DTPA are small, neither agent is sufficiently innocuous to be given as a rapid injection in clinically unstable patients. Slow, intravenous infusion of Gd-DTPA or MnCl2 is likely to be tolerated well by even severely ill individuals.