Search results for "Contrast media"
showing 10 items of 323 documents
Controlling diffusion of 3He by buffer gases: a structural contrast agent in lung MRI.
2006
Purpose: To study the influence of admixing inert buffer gases to laser-polarized 3 He in terms of resulting diffusion coefficients and the consequences for image contrast and resolution. Materials and Methods: The diffusion coefficient of 3 He was altered by admixing buffer gases of various molecular weights ( 4 He, N2, and SF6). The influence of the pulse sequence and the diffusion coefficient on the appearance of MRI of (laserpolarized) gases was analyzed by comparison of basic theoretical concepts with demonstrative experiments. Results: Excellent agreement between theoretical description and observed signal in simple gradient echoes was observed. A maximum signal gain can be predicted …
Recycling of 3He from lung magnetic resonance imaging
2011
We have developed the means to recycle 3He exhaled by patients after imaging the lungs using magnetic resonance of hyperpolarized 3He. The exhaled gas is collected in a helium leak proof bag and further compressed into a steel bottle. The collected gas contains about 1–2% of 3He, depending on the amount administered and the number of breaths collected to wash out the 3He gas from the lungs. 3He is separated from the exhaled air using zeolite molecular sieve adsorbent at 77 K followed by a cold head at 8 K. Residual gaseous impurities are finally absorbed by a commercial nonevaporative getter. The recycled 3He gas features high purity, which is required for repolarization by metastability ex…
Hepatobiliary phase in cirrhotic patients with different Model for End-stage Liver Disease score: comparison of the performance of gadoxetic acid to …
2018
The purpose of this study was to compare the performance of gadobenate dimeglumine–enhanced MRI and gadoxetic acid–enhanced MRI in the hepatobiliary phase (HBP) in cirrhotic patients with different degrees of liver dysfunction. In this retrospective cross-sectional study, we analyzed the unenhanced phase and the HBP of 131 gadobenate dimeglumine–enhanced MRI examinations (gadobenate dimeglumine group) and 127 gadoxetic acid–enhanced MRI examinations (gadoxetic acid group) performed in 249 cirrhotic patients (181 men and 68 women; mean age, 64.8 years) from August 2011 to April 2017. For each MRI, the contrast enhancement index of the liver parenchyma was calculated and correlated to the Mod…
Contrast ultrasound LI-RADS LR-5 identifies hepatocellular carcinoma in cirrhosis in a multicenter restropective study of 1,006 nodules
2018
Background & Aims The use of contrast enhanced ultrasound (CEUS) for the diagnosis of hepatocellular carcinoma (HCC) in cirrhosis was questioned because of the risk of a false positive diagnosis in cases of cholangiocarcinoma. The American College of Radiology has recently released a scheme (CEUS Liver Imaging Reporting and Data System [LI-RADS®]) to classify lesions at risk of HCC investigated by CEUS. The aim of the present study was to validate this LI-RADS scheme for the diagnosis of HCC. Methods A total of 1,006 nodules from 848 patients with chronic liver disease at risk of HCC were collected in five Italian centers and retrospectively analyzed. Nodules were classified as LR-5, (HCC) …
Hepatocellular Carcinoma Presenting at Contrast-Enhanced Multi–Detector-Row Computed Tomography or Gadolinium-Enhanced Magnetic Resonance Imaging as …
2012
OBJECTIVE: The objective of the study was to measure growth rate and to determine the optimal interval time for imaging follow-up of hepatocellular carcinomas (HCCs) presenting at multi-detector-row computed tomography (MDCT) or magnetic resonance imaging (MRI) as small, indeterminate lesions. METHODS: We included patients with cirrhosis with HCC initially presenting as indeterminate lesion of 2 cm or less at MDCT or MRI August 2005 to August 2009 and with available imaging follow-up. Measures of tumor growth included tumor volume doubling time (TVDT), tumor percentual diameter increase, and tumor percentual volume increase. RESULTS: We examined 48 patients (mean age, 64 years) with 69 HCCs…
Liver stiffness measurement in patients with nodular regenerative hyperplasia undergoing magnetic resonance elastography
2020
Purpose Nodular regenerative hyperplasia (NRH) may mimic cirrhosis at imaging. We aim to investigate the effect of NRH on liver stiffness measurement (LSM) obtained with magnetic resonance elastography (MRE).Methods This retrospective, Institutional Review Board-approved study included 37 subjects with NRH (Group 1) and no or minimal fibrosis (F0-F1), a control group (Group 2) made of 30 subjects with non-advanced fibrosis (F0-F2), and a control group (Group 3) made of 30 subjects with advanced fibrosis (F3-F4), all with available MRE. LSM was measured in each subject along with assessment of hepatic morphological features of cirrhosis and signs of portal hypertension. The significance of t…
ATLAS OF CONTRAST-ENHANCED SONOGRAPHY OF FOCAL LIVER LESIONS
2015
This book offers an image-based, comprehensive quick reference guide that will assist in the interpretation of contrast-enhanced ultrasound (CEUS) examinations of the liver in daily practice. It describes and depicts typical and atypical behavior of both common and less frequently observed focal liver lesions. For each type of lesion, the findings on pre- and post-contrast images are presented and key characteristics are highlighted. Individual chapters also focus on the assessment of response to locoregional and systemic treatment and the impact of European guidelines on CEUS. The Atlas of Contrast-Enhanced Sonography of Focal Liver Lesions will serve as an invaluable hands-on tool for pra…
MRI of the pulmonary parenchyma.
1999
Imaging of the pulmonary parenchyma represents a unique challenge for MRI. Limited signal is caused by low proton density, susceptibility artifacts, and physiological motion (cardiac pulsation, respiration). Recently, further improvements in MRI techniques have widened the potential for investigations of pulmonary parenchymal disease. These include very short echo times, ultrafast turbo-spin-echo acquisitions, projection reconstruction technique, breathhold imaging, ECG triggering, contrast agents (perfusion imaging, aerosols), sodium imaging, hyperpolarized noble gas imaging, and oxygen enhancement. By using widely available techniques, MRI is helpful in the assessment of (a) acute alveoli…
Helium-3 imaging of pulmonary ventilation.
1998
In the first studies in humans, the 3He gas was Helium is an inert, non-radioactive, noble gas. directly inhaled from the glass cell or via a mouth 3He is a rare isotope with a nuclear spin c. As it tip or plastic bag [2, 3]. The estimated inhaled is derived from tritium decay, it is quite expensive. volume in our studies was 400–500 ml. Recently, Non-polarized 3He costs 100–150 US$. Advanwe developed a computer-assisted application tages for applications in humans are: negligible system which is compatible with spontaneous solubility in water or blood, no adverse effects — breathing, assisted or mechanical ventilation. The widely used in deep-sea diving (80% He, 20% lungs can be flushed wi…
Contrast-enhanced MRI of the lung
2000
The lung has long been neglected by MR imaging. This is due to unique intrinsic difficulties: (1) signal loss due to cardiac pulsation and respiration; (2) susceptibility artifacts caused by multiple air-tissue interfaces; (3) low proton density. There are many MR strategies to overcome these problems. They consist of breath-hold imaging, respiratory and cardiac gating procedures, use of short repetition and echo times, increase of the relaxivity of existing spins by administration of intravenous contrast agents, and enrichment of spin density by hyperpolarized noble gases or oxygen. Improvements in scanner performance and frequent use of contrast media have increased the interest in MR ima…