Detection of experimental hepatic tumors using long circulating superparamagnetic particles.

RATIONALE AND OBJECTIVES: To evaluate the potential of an iron oxide-based MR contrast agent for the detection and delineation of experimental liver tumors during the early vascular phase of the compound. METHODS: Superparamagnetic blood pool agent (SBPA) was administered intravenously to rabbits bearing VX2 tumors. Images were acquired before the injection, immediately after, and 1 or 3 weeks later. The variations of signal intensity were measured in the tumors and in several tissues for various T1-weighted spin-echo, T2-weighted fast spin-echo, and T2-weighted gradient-recalled-echo sequences. RESULTS: Fourteen and 12 of the 16 tumors were detected immediately after SBPA injection using, respectively, the T2-weighted fast spin-echo and T2-weighted gradient-recalled-echo sequences. A significant decrease in signal intensity was observed in well-perfused organs, and blood signal was abolished even at the lowest injected dose and using a T1-weighted sequence. In the late phase, the loss in signal intensity of the liver was even more pronounced. CONCLUSION: The dominant T2 effect of SBPA induces an increase in the tumor-to-liver and tumor-to-blood contrast during the vascular phase, improving the detection of the tumors and allowing the distinction between small lesions and vessels through plane. This effect on the liver signal persists for several days because of the incorporation of SBPA in the reticuloendothelial system.

Human gastrocnemius medialis pennation angle as a function of age: from newborn to the elderly.

The aim of the present study was to quantify changes in human skeletal muscle pennation angle (F theta) values during growth and adult life. The human gastrocnemius medialis muscle of 162 subjects (96 males and 66 females) in the age range 0-70 years was scanned with ultrasonography. The subjects were laying prone, at rest, with the ankle maintained at 90 degrees with all muscles relaxed. F theta increased monotonically starting from birth (0 years) and reached a stable value after the adolescent growth spurt. There was a significant (p < 0.05) linear relationship between F theta and muscle thickness (TK). F theta = 0.84 (+/- 0.09) * TK + 3.15 (+/- 1.13). Human gastrocnemius medialis F theta and TK data found in the literature seem to fit the F theta-TK plot in a coherent manner, independent of the physiological or anatomical characteristics of the subject. The present findings indicate that F theta is not a constant parameter but evolves, as is the case for bone length and height, as a function of age.

Risk stratification after myocardial infarction. A reappraisal in the era of thrombolysis. The Groupe d'Etude du Pronostic de l'Infarctus du Myocarde (GREPI)

OBJECTIVES: The present study was performed to evaluate whether the modalities of risk stratification after myocardial infarction were still operative in the thrombolytic era. BACKGROUND: Prediction of fatal events in the aftermath of myocardial infarction relies on tests which aim to assess myocardial function, residual ischaemia and propensity for ventricular arrhythmias. Recent data on improved myocardial infarction prognosis have led to the view that risk stratification needs to be updated. METHODS: In this multicentre, prospective study, 471 acute myocardial infarction patients, 45% of whom were given thrombolytic therapy, were enrolled from the 10th day and underwent all or part of the following tests exercise test, radionuclide ventriculography (resting and exertional ejection fraction). Holter monitoring, signal-averaged electrocardiography and programmed electrical stimulation. Univariate and multivariate analyses were performed to identify predictors of mortality. RESULTS: One year and long-term (mean follow-up 31.4 months) mortality rates were 5.5% and 8.4%, respectively. Prediction of mortality was assessed and the role of the following variables was thus determined: age over 56 years (P = 0.01), previous coronary attacks (P < 0.001), history of heart failure (P < 0.001), early heart failure after myocardial infarction (P = 0.017), maximum workload of lest than 120 W at exercise test (P = 0.014), ineligibility to perform exercise (P = 0.002), depressed left ventricular ejection fraction (P = 0.013), late potentials as identified using 50 Hz high pass filtering (P = 0.012), mean night-time cycle length of less than 750 ms (P < 0.001), standard deviation of day time RR intervals of less than 100 ms (P = 0.04), the last two measures reflecting heart rate variability. In this population, neither ventricular ectopic activity nor inducibility of sustained monomorphic ventricular tachycardia at electrophysiological study carried any prognostic significance. Multivariate analyses showed that decreased heart rate variability, presence of late potentials and low ejection fraction (< 30%) made an independent contribution to the survival models. CONCLUSION: In the current context of management of acute coronary patients, the basis for risk stratification after myocardial infarction remain roughly unchanged.

Clinical experience with technetium-99m teboroxime scintigraphy in patients referred for myocardial perfusion evaluation.

A series of 30 patients (25 males, 5 females, age = 28-73 years) with a clinical indication of thallium-201 stress/4 hours redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium-99m teboroxime (CARDIOTEC, Squibb Diagnostics) in order to assess the clinical usefulness of this new molecule and to compare it to thallium. In all cases coronary artery disease was known or highly suspected, with a history of myocardial infarction in 18 cases (subacute n = 6, remote n = 12) and/or previous by-pass surgery or PTCA in 5 cases. Medical treatment was not discontinued at the time of stress testing. Coronary angiography was available for 27 patients. Exercise tests for both tracers were carried out on an ergometric bicycle during the same day and the levels of exercise achieved for the thallium studies were very similar to those achieved for teboroxime. Imaging was performed in three planar projections and sudies were evaluated using a model with 4 territories: septal and anterior assumed to correspond to the LAD artery, lateral and latero-posterior (= LCX), inferior and posterior (= RCA) and apex. Classification of results was: normal, ischemic, infarcted and infarcted with ischemia. With reference to the thallium-201 results, agreement was found in 86% (37/43) of normal regions and in 82% (63/77) of abnormal regions. Relative to documented coronary artery lesions (27 patients) sensitivity and specificity of thallium and teboroxime for exact correspondence between arteries and territories were, respectively: thallium, se = 71%, sp = 64%, teboroxime, se = 67%, sp = 75%.(ABSTRACT TRUNCATED AT 250 WORDS)

Technetium-99m teboroxime scintigraphy. Clinical experience in patients referred for myocardial perfusion evaluation.

In order to evaluate the clinical value of a new myocardial perfusion tracer, a series of 30 patients (25 male, 5 female, mean age 56 years) referred for thallium 201 stress/redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium 99m teboroxime (Cardiotec SQUIBB). In all cases coronary artery disease was known or highly probable, with a history of myocardial infarction in 18 cases. Medical treatment was not discontinued at the time of stress testing, and coronary angiography was available in 27 patients. Exercise tests for both tracers were carried out on a bicycle ergometer during the same day, and the levels of exercise achieved for the 201Tl study were very similar to those achieved for 99mTc-teboroxime. Studies performed in three planar projections were evaluated using a model with four territories: septal and anterior assumed to correspond to the left anterior descending artery, lateral and latero-posterior (left circonflex), inferior and posterior (right coronary artery) and apex. Classification of results was: normal, ischaemic, infarcted and infarcted with ischaemia. On comparison with the 201Tl results, agreement was found in 86% (37/43) of normal regions and in 82% (63/77) of abnormal regions. Relative to documented coronary artery lesions (27 patients), sensitivity and specificity of 201Tl and 99mTc-teboroxime for exact correspondence between arteries and territories were respectively: 201Tl: sensitivity 64%, specificity 60%; 99mTc-teboroxime: sensitivity 62%, specificity 77%.(ABSTRACT TRUNCATED AT 250 WORDS)