No abstract

Acute myocardial infarctions were produced in 11 dogs by ligation of the left anterior descending coronary artery. Twenty-four hours after ligation, 0.35 millimoles per kilogram of Gd-DTPA was injected intravenously, followed by cardiectomy either 90 seconds (3 dogs) or 5 minutes (5 dogs) later. The remaining 3 dogs had cardiectomy without injection of Gd-DTPA at 24 hours after coronary occlusion. The 3 dogs that did not receive Gd-DTPA had longer T1 and T2 relaxation times in infarcted myocardium than in normal myocardium, as measured by a 10.7-MHz magnetic resonance (MR) spectrometer. The T1 and T2 relaxation times of normal myocardium at 90 seconds postinjection of Gd-DTPA were significantly shorter (p less than 0.05) than those of the normal myocardium of animals that did not receive Gd-DTPA. At five minutes postinjection, significantly (p less than 0.01) greater T1 shortening was exhibited in the infarcted myocardium compared with adjacent normal myocardium in the dogs injected with Gd-DTPA. Thus, Gd-DTPA has differential and time-varying effects on relaxation times of normal and infarcted myocardium.

No abstract

Gadolinium-DTPA (Gd-DTPA) enhancement of magnetic resonance (MR) imaging was tested for diagnostic utility in evaluating carcinoma. Human breast carcinoma implanted in ten nude mice was studied before and after injection of Gd-DTPA at two different doses (0.2 and 0.5 mmol/kg body weight). Before injection, all tumors appeared homogeneous in intensity on spin-echo images; after injection, it was possible to distinguish areas of strong enhancement from areas of weak enhancement. Histologic correlations showed that the strongly enhanced areas corresponded to richly vascularized connective tissue and apparently viable tumoral tissues, while the weakly enhanced areas corresponded to nonvascularized necrotic tissue. The results indicate that intravenously administered paramagnetic agents such as Gd-DTPA may improve the specificity and diagnostic accuracy of MR imaging by permitting better differentiation of tumor elements.

The effect of periportal collagen deposition on magnetic resonance images and T1 and T2 relaxation times was studied in the rat. Hepatic cirrhosis was induced in 29 rats by chronic intraperitoneal thioacetamide injections. Another 14 rats in which liver abnormalities did not develop were used as controls. The rats were imaged using a small-bore resistive magnet. Histologic correlations and hydroxyproline measurements were performed to document the changes in periportal collagen deposition. The T1 and T2 relaxation times, determined both in vivo and in vitro with spectroscopy, were compared between the normal group and the group with moderate to severe histologic evidence of cirrhosis. The deposition of two to four times the normal amount of collagen in the liver did not affect the T1 or T2 relaxation time. Relatively pure periportal collagen fibrosis does not appear to affect the magnetic resonance image or T1 or T2 relaxation times of the rat liver.