Differentiation of healthy from cirrhotic livers. Evaluation of parametric images after contrast administration in magnetic resonance imaging.

RATIONALE AND OBJECTIVES: The authors describe a method to differentiate healthy from cirrhotic livers by the analysis of their behavior after paramagnetic contrast administration on magnetic resonance imaging. METHODS: A dynamic single-slice spoiled-gradient recalled echo magnetic resonance imaging after contrast administration was performed on 67 patients (36 healthy livers and 31 cirrhotic livers). Three parametric images (averaged-enhancement, maximum-enhancement, and maximum-velocity) were reconstructed from the temporal dynamic images. Liver values were quantified by means of a region-of-interest procedure. RESULTS: Relative averaged-enhancement and maximum-enhancement values were significantly different ( P < 0.05) between cirrhotic and normal livers. There was a significant correlation between the parametric values and the Child-Turcotte index of hepatic chronic insufficiency (P < 0.05). CONCLUSIONS: Parametric images allow characterization of the signal-versus-time pixel-by-pixel variations in dynamic magnetic resonance imaging. The averaged-enhancement and maximum-enhancement values can be used to differentiate healthy from cirrhotic livers with accuracy. The higher values found in cirrhotic patients may reflect an overall increase in the amount of extracellular contrast present with respect to healthy livers. The degree of liver brightness in cirrhotic patients probably is related to an increased amount of interstitial space, an indirect measurement of hepatic necrosis.

Randomised double-blind clinical trial of intermediate- versus high-dose chloral hydrate for neuroimaging of children.

Orally administered chloral hydrate is the most widely used sedative in children undergoing MRI. We compared intermediate- and high-dose oral chloral hydrate in 97 consecutive children undergoing MRI in a prospective, controlled, double-blind, randomised clinical trial. There were 50 girls and 47 boys, mean weight (+/- SD) 14.7 +/- 6.4 kg, and mean age 38 +/- 31. The children were randomly allocated to receive chloral hydrate syrup either 70 mg/kg (group A, n = 50) or 100 mg/kg (group B, n = 47). These two groups were not significantly different in sex, weight, age, diagnosis or ambulatory medication. The mean initial dose (+/- SEM) was 64 +/- 2 mg/kg for group A and 93 +/- 2 mg/kg for group B. Because adequate sedation was not achieved, 14 patients in group A and 6 in group B required a second dose, giving a mean total dose of 70 +/- 2 mg/kg for group A and 96 +/- 2 mg/kg for group B. The percentage of successful examinations after the initial dose (A: 64%, B: 87%; p < 0.05) and the total dose (A: 92%, B:100%; p = 0.14) was higher in group B. Significant differences were found for the time of onset of sedation (A:28 +/- 2 min, B: 21 +/- 1 min; p < 0.05), but not for the time to spontaneous awakening after the completion of the examination. The rate of adverse reactions was similar (A: 20%, B: 21%; p = 1.00). We conclude that high-dose oral chloral hydrate improves the management of children undergoing MRI.

[Extracorporeal lithotripsy: comparative study with magnetic resonance, ultrasonography, and nuclear medicine of short-term renal changes produced by piezoelectric and electrohydraulic equipment]. / Litotricia extracorpórea: estudio comparativo con resonancia magnética, ecografía y medicina nuclear de las alteraciones renales a corto plazo provocadas por equipos piezoeléctrico y electrohidráulico.

Ultrasound, Nuclear Magnetic Resonance (NMR) and Nuclear Medicine (NM) were used to evaluate short-term changes and renal complications (within the first 10 days) induced by extracorporeal lithotrity (ESWL) from two separate lithotripters. To this end, a consecutive prospective study with 18 randomly selected patients, all candidates to ESWL, was conducted. ESWL was performed using a piezoelectric lithotripter in 10 patients and an electrohydraulic equipment in 8 patients. Qualitative evaluation of images was done with ultrasound and NMR (changes in renal morphology: shape, cortico-medullary definition, size, changes in perirenal space), and with isotopic renogram (global renal function); while quantitative evaluation was done with NMR (measurement of signal intensity on cortex, marrow and muscle), and with isotopic renogram (semiquantitative assessment of unilateral renal function and renal excretory function). ESWL with piezoelectric and electrohydraulic lithotripter shows a low short-term complication rate: changes of cortico-medullary differentiation (ultrasound in 27.8% cases, NMR in 5.6%) and perirenal striations (NMR in 11%). No renal function changes were found. These observations have not been quantitatively corroborated; we have not found statistically significant differences between changes produced after ESWL either with piezoelectric or electrohydraulic lithotripters.

Dynamic MR imaging of liver tumors: analysis with temporal reconstruction images.

PURPOSE: To graphically display the time dependency of contrast enhancement of liver tumors at examination with dynamic magnetic resonance (MR) imaging. MATERIALS AND METHODS: A temporal reconstruction image was generated by obtaining a line of interest drawn on a single image through the liver and the tumor and reformatted over a sequence of temporal images. This calculated image expressed the temporal evolution of the line, including nontumoral liver and tumor, with regard to three variables: signal intensity, enhancement, and velocity. This allowed a visually integrated analysis of 95 hepatic lesions studied with dynamic single-section MR imaging after contrast material administration. RESULTS: Temporal reconstruction images were obtained for all the dynamic studies. Five patterns of enhancement based on signal intensity and velocity variations coupled with morphologic information were found: wall, diffusion, moderate enhancement, marked progressive, and early intense patterns. CONCLUSION: Temporal reconstruction of liver tumors after contrast material administration can be used to analyze, describe, and report the dynamics of lesion enhancement with morphologic and temporal resolution.

Regional lymphadenopathies in patients with renal calculi: analysis with ultrasound and MRI.

Thirty-nine patients with renal calculi were retrospectively studied with magnetic resonance (MR) imaging and an ultrasound (US). All patients were examined as part of a research project for imaging evaluation of complications of extracorporeal shock wave lithotripsy. Twelve of the patients showed lymph node enlargement in the retroperitoneal perivascular space. Adenopathies were visualized by MR imaging but not with US: The presence of large lymph nodes was associated with urinary, renal parenchymal, or stone infection. When large lymph nodes are found in the retroperitoneal perivascular space in patients with lithiasis, urinary tract infection must be assumed as the cause of these adenopathies.

Lesion/fat intensity ratio in MR characterization of hepatic masses.

On T2-weighted spin echo images, lesion/liver intensity ratios can be used to accurately distinguish hepatic cavernous hemangioma from malignant lesions. However, since patients with focal liver lesions may present diffuse liver disease, this relationship can be inaccurate. We studied 91 hepatic lesions to compare the value of lesion/liver and lesion/fat ratios in the differential diagnosis of liver lesions. In doubtful cases the use of lesion/fat intensity ratio can be used to improve accuracy in the diagnosis of liver lesions. The combination of both ratios into a single diagnostic index gave a correct classification of malignant versus hemangioma in 92.3% of the cases.