ABSTRACT
The purpose of this study was to evaluate changes in the proton nuclear magnetic resonance relaxation times (T1 and T2) after chronic infarction in the rat. Ligation of the left coronary artery was followed by various degrees of reduction in myocardial blood flow. The ligation induced infarction in the left ventricle and compensatory hypertrophy in the right ventricle, as evaluated by the ratio of right ventricle to body weight. The interventricular septum and the right ventricle did not become ischemic in this model and served as control areas. In the infarcted left ventricle our results showed an increase in the T1 and T2 relaxation times after 15 and 30 days of ligation and a slight decrease after 60 days. A similar change in the T1 values was observed in the right ventricle. In contrast, a persistent increase in the T2 relaxation times was observed in the right ventricle and correlated with the ratio of right ventricle to body weight (r = 0.54, p < 0.01). The observation that the magnetic resonance relaxation times in vitro are modified in the hypertrophic right ventricle after myocardial infarction could be important in interpreting magnetic resonance imaging in vivo. There was no relation between the changes in the relaxation times and the degree of myocardial ischemia.
Subject(s)
Hypertrophy, Left Ventricular/physiopathology , Magnetic Resonance Spectroscopy , Myocardial Infarction/physiopathology , Animals , Blood Flow Velocity , Disease Models, Animal , Hypertrophy, Left Ventricular/etiology , Male , Myocardial Infarction/complications , Rats , Rats, WistarSubject(s)
Kidney Transplantation/diagnostic imaging , Technetium Tc 99m Mertiatide , Adolescent , Adult , Creatinine/blood , Evaluation Studies as Topic , Female , Humans , Kidney Function Tests/methods , Kidney Transplantation/physiology , Male , Middle Aged , Radionuclide Imaging , Reference ValuesABSTRACT
An ECG-triggered, two-sequence MRI technique is proposed for the precise measurement of proton T1 relaxation times of the human myocardium at a field strength of 0.5 T. The combination of an inversion recovery (IR) sequence and a spin echo (SE) sequence is not new. It is, however, rarely used in quantitative in vivo cardiac studies. Our approach employs a synchronization of the 90 degrees read pulse to the systolic period. In a study of 22 healthy volunteers, the globally measured T1 value was estimated to be 714 +/- 23 ms. Four of the volunteers also underwent additional imaging scans for the purposes of reproducibility assessment. The T1 precision was found to be 3.9 +/- 1.1% for the IR/SE combination and 16.9 +/- 5.3% for a combination of SE sequences. Total imaging time for the IR and SE sequences was 19.2 +/- 3.0 mins. The relative rapidity of this classic technique and the T1 precision obtained give this technique an obvious application in the discrimination of normal and diseased myocardium. In the same study, valuable supplementary tissue characterization is provided by T2, calculated from the SE sequence. T2 was evaluated to be 50 +/- 3 ms.
Subject(s)
Heart/anatomy & histology , Heart/physiology , Magnetic Resonance Imaging/methods , Adult , Electron Spin Resonance Spectroscopy , Female , Humans , Male , Middle Aged , Pilot ProjectsABSTRACT
Ultrasound examination of the abdomen permits us to diagnose in childhood much more bile duct calculi than before. Surgery is not necessary in all cases but a follow-up with ultrasound is usefull.