Contrast-enhanced magnetic resonance imaging with intracellular contrast agents--a new way of monitoring hepatic reperfusion injury?
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Animals↗
Biomedical subjects
P Reimer
Publications and source records attributed to P Reimer.
[New super-paramagnetic iron particles for MRI. Phase II study of malignant liver tumors].
The clinical tolerability and diagnostic value of Resovist as a new superparamagnetic iron oxide contrast medium was studied in 30 patients with malignant focal liver lesions (28 metastases, 2 HCC) within a phase II multicenter study. Magnetic resonance imaging (MRI) was performed at 1.0 Tesla with T1-weighted FLASH- and T2-weighted spin echo sequences before and following intravenous injection of Resovist at three different dose groups (4, 8 and 16 mumol Fe/kg). Liver signal intensity was significantly reduced on post-contrast images, while malignant focal liver lesions showed no signal changes. Resovist improved tumor liver contrast and lesion-conspicuity, especially for lesions smaller than 1 cm. The dose of 8 mumol Fe/kg was sufficient to achieve diagnostic tumor-liver contrast. Compared to images directly after injection, the number of detected lesions did not improve until 70 min later. There were no significant changes in vital signs (heart rate, blood pressure) or laboratory values until 72 h post-injection.
Adult↗
[Fast and ultra-fast MRI of the brain].
Fast spin-echo sequences, which are based on the RARE sequence, accelerate MRI significantly. The basic principle of fast- or turbo-spin-echo sequences (FSE, TSE), as well as of the gradient-and-spin-echo sequences (GRASE, TGSE), is the sampling of multiple independently phase-encoded echos after each excitation. The basic principles of these sequences and the potentials and limitations of their clinical application are discussed. Their main advantage is a significant reduction of the time for data acquisition, which allows either a reduction of imaging time or high-resolution images even with T2-weighting. The fast sequences provide all possibilities of contrast variation and of preparation pulses such as fat saturation or water suppression. Despite some restrictions, of which reduced susceptibility is clinically relevant, they can replace conventional spin-echo sequences in brain imaging.
Brain↗
[Rapid spin echo sequences for detection and characterization of focal liver lesions. Use of fast T2-weighted spin echo with fat suppression and fast spin echo with combined gradient echo (GRASE)].
The purpose of this study was to assess the value of fast-spin-echo (FSE) sequences without and with fat suppression as well as gradient-and-spin-echo (GRASE) sequences for the detection and subsequent characterization of focal liver lesions. A total of 51 consecutive patients with clinically suspected focal liver lesions were studied. FSE without fat suppression proved to be valuable for the detection (TE 90 ms) and characterization (TE 158 ms) of focal liver lesions. Fat suppression did not improve the performance of FSE. GRASE sequences with multiple excitations were clinically superior to the faster single-shot approach.
Carcinoma, Hepatocellular↗
[Echo-planar imaging (EPI) of the abdomen].
The time resolution of echoplanar imaging (EPI) allows the acquisition of images < or = 100 ms, thus eliminating motion-related artifacts of the abdomen. Physical limitations are restrictions in signal-to-noise ratio and spatial resolution. Breath-held acquisitions are recommended to avoid spatial misregistrations and to ensure a defined slice position. Clinical studies have demonstrated the usefulness of EPI for the detection and characterization of focal liver lesions. The development of clinical strategies of EPI for abdominal imaging requires the administration of gastrointestinal contrast agents as in computed tomography. Current clinically approved CT contrast agents appear to be applicable for abdominal EPI because of their long relaxation times.
Abdominal Neoplasms↗
[Detection of liver tumors].
Accurate detection of liver metastases in patients with known primary tumors is often essential for therapeutic decision making. Compared to conventional contrast media-enhanced CT unenhanced MRI seems to be slightly superior for the detection of small focal liver lesions. However, intraoperative US and CTAP show higher sensitivities for lesion detection but use of these techniques is limited because of their invasive character. The new superparamagnetic MR contrast medium ENDOREM improves the number of liver lesions detected significantly as compared to unenhanced MRI. Furthermore, as shown recently, ENDOREM-enhanced MRI may be as sensitive as CTAP. Thus, ENDOREM is useful for preoperative staging of liver tumors due to improvement in lesion detection and delineation of the hepatic vascular system.
Colorectal Neoplasms↗
Initial feasibility studies using single-shot EPI for the detection of focal liver lesions.
Echo planar MR imaging (EPI) has been developed to completely eliminate motion artifacts and is currently being prepared for implementation into clinical MR systems. Thus, the purpose of this study was to evaluate the clinical utility of EPI in the detection of focal liver lesions and to compare EPI with in the detection of focal liver lesions and to compare EPI with contrast-enhanced CT. EPI studies were performed on an experimental 1.0 Tesla whole body system using fat-suppressed single-shot spin echo (SE) and inversion recovery (IR) pulse sequences. A total of 26 liver tumors in 12 patients scheduled for liver resection were prospectively examined and correlated with intraoperative ultrasound, surgery, and pathology as the gold standard. Quantitative analysis of EPI was performed by means of liver signal-to-noise and tumor-liver contrast-to-noise calculations. Diagnostic performance compared with contrast-enhanced CT was assessed by means of ROC analysis. Lesion-liver contrast was highest with EPI SE at a TE-time of 70 ms and this technique showed best lesion detectability as measured by area under curve (AUC) values. Among EPI techniques, the IR sequence with an inversion time of 300 ms to null the liver signal showed high lesion-liver contrast but all four reviewers reported problems assessing liver anatomy. Improved EPI techniques may prove useful for screening of focal liver lesions.
Adult↗
Pancreatic receptors: initial feasibility studies with a targeted contrast agent for MR imaging.
PURPOSE: To evaluate cholecystokinin (CCK) as a target-specific vector for magnetic resonance (MR) receptor imaging of rat pancreas. MATERIALS AND METHODS: Monocrystalline iron oxide (MION) was labeled with CCK by noncovalent attachment. Receptor specificity of the conjugate was determined with competitive binding studies. Pharmacologic determinations were blood half-lives, biodistribution, time responses, dose responses, and limited toxicity. RESULTS: Specific cell binding of MION-20-CCK was saturable and inhibitable by a CCK antagonist. Blood half-life of MION-20-CCK was 20 minutes, which was shorter than that of unlabeled MION. Biodistribution studies showed a statistically significant decrease in relaxation times in pancreatic tissues from 42.7 msec +/- 2.0 to 33.8 msec +/- 1.4 (P < or = .05) but not in tumor after administration of MION-20-CCK. The half-life of MION-20-CCK in the pancreas was 3 weeks; no signs of toxicity were shown at the level tested. CONCLUSION: Target-specific MR imaging of pancreatic receptors is feasible. Additional studies are necessary to perfect binding strategies, optimize preparations, and scale up synthesis for imaging in other species.
Acute Disease↗
Echoplanar MR imaging of the liver in patients with focal hepatic lesions: quantitative analysis of images made with various pulse sequences.
OBJECTIVE: We undertook this study to evaluate pulse-sequence performance in terms of liver signal-to-noise ratio (SNR) and lesion-liver contrast-to-noise ratio (CNR) on T1- and T2-weighted echoplanar MR imaging. SUBJECTS AND METHODS: Forty-nine patients referred for MR imaging of the liver were examined at 1.5 T with echoplanar MR imaging using spin-echo, inversion-recovery, and gradient-echo pulse sequences. T2-weighted spin-echo (TE = 25, 50, 100, and 150 msec), T1-weighted inversion-recovery (T1 = 100, 380, 600, and 800 msec), and T2*-weighted gradient-echo (TE = 20 msec) images were acquired after one excitation (TR = infinite), using a 128 x 128 data matrix. T2-weighted spin-echo (TE = 20, 50, 100, and 150 msec) images were also obtained with two excitations (TR = 6 sec), resulting in a 128 x 256 data matrix. Signal intensity measurements were made to calculate liver SNR and lesion-liver CNR. RESULTS: Single-excitation, T2-weighted, spin-echo images at a minimum TE of 25 msec provided the highest liver SNR (p < .05). Single-excitation, T2-weighted, spin-echo images at TEs of 50 and 100 msec, and T1-weighted inversion-recovery images at Tls of 100 and 380 msec provided the highest lesion-liver CNR (p < .05). However, the latter two pulse sequences had considerably inferior liver SNR (p < .05). CONCLUSION: Single-excitation, T2-weighted, spin-echo images provide both superior liver SNR and superior lesion-liver CNR. These results can be used to guide technique selection when echoplanar MR imaging is used to examine the liver.
Echo-Planar Imaging↗
[Magnetic resonance angiography of supra-aortic arteries].
MR angiography of the carotid system was found to be readily applicable due to the laminar and fast flow conditions in the supra-aortic arteries. Time-of-flight methods are superior to phase-contrast measurements for the investigation of atherosclerotic lesions. Recent developments in sequence design enable improvement of the MR angiographic results with respect to correct staging of stenotic alterations. Two-dimensional acquisitions are preferred in slow flow conditions with the disadvantage of decreased resolution, in-plane saturation effects, and poststenotic signal voids. In 3D MR angiography, the major advantage is improved resolution, although the saturation effects within the measurement volume must be compensated for either by sequential acquisition of multiple thin volumes or by the application of asymmetric excitation pulses. In a prospective trial with 50 patients, the advantages of a new type of rf-pulse (TONE) are demonstrated.
Blood Flow Velocity↗
The Budd-Chiari syndrome: clinical presentation and diagnostic findings in 45 patients treated by surgery.
We report on the clinical presentation and diagnostic findings in 45 patients with Budd-Chiari syndrome. The diagnosis was confirmed by histology at the time of liver transplantation (n = 37) or shunt surgery (n = 8). An underlying disorder could be established only in half of the patients, oral contraceptives as predisposing factor were known in 18 cases. Clinically, abdominal pain and distension as well as hepatomegaly and ascites were most frequent findings, whereas changes in laboratory data were more or less unspecific. By use of repeated ultrasound, a definite diagnosis of a Budd-Chiari syndrome could be confirmed in all cases by obligatory demonstration of obstruction or thrombosis of at least one major liver vein. Hepatic venography revealed only one false-negative result. Celio-mesenteric arteriography plus portography, cavography and preoperative liver biopsy did not present additional diagnostic information. These techniques may contribute to treatment planning of portosystemic shunt surgery or hepatic transplantation. In conclusion, the presence of hepatosplenomegaly, ascites, abdominal pain and distension, especially in combination with a known hypercoagulable state, should alert to the possibility of a Budd-Chiari syndrome. Ultrasound is the diagnostic tool of choice. Hepatic venography should only be performed if even repeated ultrasound is not conclusive.
Adolescent↗
[Progress in magnetic resonance tomography of the liver: value of ultra-rapid imaging and liver-specific contrast media].
Ongoing technical improvements in magnetic resonance imaging (MRI) and the development of liver-specific contrast agents are likely to have an impact on the clinical assessment of liver disease. Technical progress towards methods of motion-free MRI and concepts of liver-specific contrast agents are presented. The potential impact of these developments on clinical medicine is discussed.
Animals↗
Concentrations of zinc and chromium in aquatic macrophytes from the sudbury and muskoka regions of Ontario, Canada.
Root and shoot samples of Eriocaulon septangulare, Nuphar variegatum, Nymphaea odorata and Pontederia cordata were collected from 15 lakes in central Ontario during the summer of 1988 to investigate possible relationships between zinc and chromium levels in aquatic macrophytes and water and sediment variables. Although concentrations of zinc and chromium differed greatly among the four species, both metals were consistently higher in Eriocaulon. Generally, root and rhizome tissue contained higher zinc and chromium than shoot tissues of the same species and site. Zinc concentrations (dry weight) ranged from 6.3 microg g(-1) in Nuphar shoots to 87.7 microg g(-1) in whole Eriocaulon. Chromium ranged from 0.23 microg g(-1) in Pontederia shoots to 23.9 microg g(-1) in whole Eriocaulon. No significant trends were detected throughout the growing season in macrophyte or sediment concentrations of either metal. Results of multiple linear regression analyses of several water quality and environmental variables on Eriocaulon indicated that sediment zinc was the best predictor of plant zinc, and sediment chromium and calcium were the best predictors of plant chromium.
Journal Article↗
[The clinical use of echoplanar MR tomography in the detection of focal liver lesions. The results of a quantitative study].
The purpose of the present study was to investigate the clinical application of echoplanar MR imaging compared to conventional MR imaging in the detection of focal liver lesions. A total of three conventional and 12 echoplanar pulse sequences were acquired in 35 patients with focal liver lesions. Motion artifacts were eliminated because of short acquisition times of 32 ms subsequently improving signal-to-noise. A single-shot spin-echo technique with a TE of 26 ms provided the highest liver signal-to-noise ratio (p < 0.05) of all sequences acquired. Contrast-to-noise ratios for a single-shot SE technique with echo times of 50-100 ms were as high as 10-40.
Cysts↗
Value of T1 and T2 relaxation times from echoplanar MR imaging in the characterization of focal hepatic lesions.
OBJECTIVE: The purpose of this study was to determine the value of echoplanar imaging in characterizing focal hepatic lesions on the basis of image-derived T1 and T2 relaxation times. SUBJECTS AND METHODS: Forty-six proven hepatic lesions were analyzed: 24 solid (21 metastases, three primary liver tumors) and 22 nonsolid (11 hemangiomas and 11 cysts). Mean lesion size (maximal length) was 4.0 (+/- 3.2) cm, and 16 of 46 lesions were less than 2.0 cm. A commercially available 1.5-T echoplanar-equipped MR scanner was used to obtain fat-suppressed, single-excitation (TR essentially infinite) axial images with a slice thickness of 10 mm. T1-weighted inversion recovery images (TE = 25 msec; TI = 100, 380, 600, or 800 msec) were acquired for 28 of 46 lesions, and T2-weighted spin-echo images (TE = 25, 50, 100, 75 or 150 msec) were acquired for 45 of 46 lesions. For each acquisition (i.e., each different TI or TE), the entire liver was imaged in a single breath-hold of 12 sec or less. RESULTS: The mean T1 was 1004 (+/- 234) msec for solid lesions, 1337 (+/- 216) msec for hemangiomas, and 3143 (+/- 1392) msec for cysts. Although the mean T1 of solid and nonsolid lesions differed (p < .004), overlap precluded the use of T1 as a discriminatory index. Mean T2 times were 80 (+/- 18) msec for solid lesions, 178 (+/- 40) msec for hemangiomas, and 517 (+/- 429) msec for cysts. The mean T2 for hemangiomas is the longest reported to date. A T2 cutoff of 116 msec was 100% accurate for classifying lesions as solid or nonsolid and 93% accurate for characterizing them as benign or malignant. CONCLUSION: Our study suggests that echoplanar-derived T2 times (but not T1 times) are useful for characterizing focal hepatic lesions. An important use may be to characterize small lesions measuring less than 2.0 cm. The main advantages of echoplanar imaging are the absence of motion-induced volume averaging and phase artifacts, the ability to acquire purely T2-weighted images, and the use of multiple data points to calculate relaxation times.
Cysts↗
[The possibilities of diagnosing the act of swallowing in contrast medium aspiration].
19 patients with contrast agent aspiration were examined prospectively utilizing a combined approach of an orally administered low-osmolal and non-ionic contrast agent and a digital X-ray system with a dynamic technique (8 images/s). This combined technique enabled a sufficient assessment of the aspiration mechanisms in all patients.
Contrast Media↗
An aqueous gastrointestinal contrast agent for use in echo-planar MR imaging.
Four volunteers were imaged with echo-planar imaging before and after ingesting a dilute barium preparation. The contrast material improved bowel visibility by increasing lumen signal intensity, without increasing noise. Long T2 gastrointestinal contrast material can be used in T2-weighted imaging when motion artifacts are suppressed by ultrashort acquisitions.
Administration, Oral↗
Animal models for magnetic resonance imaging research of the liver.
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Animals↗