1.
2.
Leander, Peter
(författare)
A new liposomal contrast medium for CT of the liver. An imaging study in a rabbit tumour model
1996
Ingår i: Acta Radiologica. - 1600-0455. ; 37:1, s. 63-68
Tidskriftsartikel (refereegranskat) abstract
A new type of liposomal liver-specific contrast medium was studied in an experimental tumour model. Rabbits were inoculated with VX2-carcinoma directly in the liver of laparotomy. CT studies were carried out 14 days after inoculation. The liver-specific contrast medium consisted of a suspension of liposomes in a 100 mg I/ml iodixanol solution, with equal amounts of encapsulated and nonencapsulated iodixanol. It was administered at a dose of 200 mg I/kg. The contrast of normal liver tissue to tumorous tissue was significantly increased by contrast medium administration, the increase being largest 10 min after injection.
3.
Leander, Peter, et al.
(författare)
CT and MR imaging of the liver using liver-specific contrast media. A comparative study in a tumour model
1996
Ingår i: Acta Radiologica. - 1600-0455. ; 37:3 Pt 1, s. 242-249
Tidskriftsartikel (refereegranskat) abstract
PURPOSE: A new type of liposomal liver-specific contrast medium (CM) in CT was studied, and the results were compared with those obtained with Mn-DPDP, a paramagnetic hepatobiliary CM, in MR imaging. The contrasts of normal liver tissue to tumorous tissue and the importance of the CM for tumour detection in the 2 modalities were studied in a rabbit tumour model. CT and T1-weighted pre- and postcontrast and T2-weighted MR images precontrast were obtained. MATERIAL, METHODS AND RESULTS: Compared to precontrast images, significantly higher contrasts of normal liver tissue to tumorous tissue were obtained after CM administration in both CT and MR examinations. At radiologic evaluation, significantly more tumours were detected after CM administration in CT and in T1-weighted MR images than in precontrast images in CT and T1-weighted MR. There were no significant differences in tumour detection frequency in MR studies including a T2-weighted pulse sequence, postcontrast CT, or postcontrast T1-weighted MR imaging. CONCLUSION: The use of liver-specific CM improves visualization of liver tumours in CT and T1-weighted MR imaging.
4.
5.
Leander, Peter
(författare)
Liver-specific contrast media for MRI and CT experimental studies
1995
Ingår i: Acta Radiologica. Supplementum. - 0365-5954. ; 396, s. 1-36
Tidskriftsartikel (refereegranskat) abstract
MRI and CT are modalities appropriate for liver imaging. To obtain higher sensitivity in diagnoses of focal lesions in the liver, contrast media (CM) are used. Non-specific extracellular CM are not optimal as they rapidly diffuse into both normal tissue and tumorous tissue. By two different mechanisms, the hepatobiliary route and targeting to the reticuloendothelial system, agents may accumulate in normal liver tissue, thereby giving liver-specific CM. So far no such agents have been approved for clinical use. In the present studies, animal models were used to investigate the imaging efficacy of experimental liver-specific CM and answer the following questions: i) Do these new liver-specific CM result in enhancement of normal liver? ii) If enhancement in normal liver is present, does this result in higher contrast of normal liver to tumorous tissue? iii) If higher contrast of normal liver to tumorous tissue is present, does this result in higher tumour detection-rates? Relative to non-enhanced and contrast-enhanced CT, what tumour detection-rate is obtained using non-enhanced and contrast-enhanced MRI? All the liver-specific CM studies possessed the ability to significantly alter the signal in normal liver tissue. Compared to precontrast values, the liver-specific CM studied in MRI (Mn-DPDP) and CT (IEEC-particles and iodixanol-liposomes) were able to increase significantly the contrast of normal liver tissue to tumorous tissue and the tumour detection-frequency in VX2-carcinoma liver tumour-bearing rabbits. In CT using a non-specific extracellular CM, iohexol, no improvement in contrast or tumour detection-frequency was obtained. As reflected in the values of contrast-to-noise obtained, MRI and CT have the same potential for tumour detection in the liver model used in the present studies. Liver-specific CM have the property of improving the contrast of normal liver tissue to tumorous tissue in MRI and CT, giving higher tumour detection-rates. Permitting intravenous administration and the use of long imaging-windows, liver-specific CM are easy to use.
6.
7.
Svensson, Jonas, et al.
(författare)
Image artifacts due to a time-varying contrast medium concentration in 3D contrast-enhanced MRA
1999
Ingår i: Journal of Magnetic Resonance Imaging. - 1522-2586. ; 10:6, s. 919-928
Tidskriftsartikel (refereegranskat) abstract
The purpose of this work was to study image effects due to time-varying contrast medium concentration in contrast-enhanced three dimensional (3D) magnetic resonance angiography (MRA) images. Two different simulation models (1D and 3D) and two different contrast medium variation schemes were used. Phantom measurements were also performed. Experiments were performed for several different bolus timings. Similar sequence and image object parameters were used in both simulations and measurements (TE/TR 2. 1/7.8 mses, flip angle 30 degrees, T1/T2 1200-80/150-40 msec, flow velocity 100 cm/sec). A small variation in bolus timing yielded large variations in the appearance of the image effects, especially if the center of k-space was sampled in the vicinity of rapid contrast medium concentration variation. For a typical bolus injection in a patient, a severe signal loss but only minor ringing and edge artifacts appeared if the bolus injection was poorly timed. Effects of pulsatile flow were minor. The 3D model proved to be a useful tool in these studies.
