How to organize animal research in radiology.
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Animal Rights↗
Biomedical subjects
M Taupitz
Publications and source records attributed to M Taupitz.
How to organize animal research in radiology.
Explore the source record for details and available documents.
Animal Husbandry↗
T2-weighted breath-hold MR imaging of the liver at 1.5 T: results with a three-dimensional steady-state free precession sequence in 87 patients.
PURPOSE: To evaluate a fast three-dimensional (3D) sequence that permits the acquisition of 16 T2-weighted images within a 29-second breath hold for magnetic resonance (MR) imaging of the liver. MATERIALS AND METHODS: Eighty-seven patients with focal liver lesions were examined at 1.5 T by using a 3D reversed fast imaging with steady-state precession (PSIF) sequence at flip angles of 15 degrees, 30 degrees, and 70 degrees and a T2-weighted spin-echo (SE) sequence. Quantitative and qualitative image analysis was performed. RESULTS: Contrast and signal difference-to-noise ratios were 56% and 33% (liver-spleen) and 76% and 68% (liver-tumor), respectively, with the 3D-PSIF sequence compared with the T2-weighted SE sequence. With 3D-PSIF, overall image quality was poorer than that of the T2-weighted SE sequence at flip angles of 15 degrees but was similar at 30 degrees and 70 degrees. At low flip angles (15 degrees and 30 degrees) all lesion types were hyperintense. At a flip angle of 70 degrees, it was predominantly cysts and hemangiomas that showed high signal intensity. With the 3D-PSIF sequence, intrahepatic vessels are void of signal and can be better distinguished from small liver lesions compared with the flow-compensated T2-weighted SE sequence. CONCLUSION: The fast 3D-PSIF sequence is a valuable addition to MR imaging of the liver.
Adult↗
Phase I clinical evaluation of Gd-EOB-DTPA as a hepatobiliary MR contrast agent: safety, pharmacokinetics, and MR imaging.
PURPOSE: To determine the safety, pharmacokinetics, and magnetic resonance (MR) imaging results of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) as a contrast agent for use in hepatobiliary MR imaging. MATERIALS AND METHODS: Gd-EOB-DTPA was tested at doses of 10, 25, 50, and 100 mumol per kilogram of body weight. Results of laboratory tests, clinical measurements, and pharmacokinetic data were obtained in 44 healthy volunteers in a double-blind, randomized, placebo-controlled design. MR images were obtained in another 16 healthy volunteers before and up to 6 hours after fast intravenous administration of Gd-EOB-DTPA. RESULTS: Gd-EOB-DTPA was well tolerated, with no important side effects or changes in laboratory parameters. Homogeneous enhancement of liver parenchyma was observed immediately after injection of the contrast agent. Peak liver signal intensity was noted 20 minutes after injection, followed by plateaulike enhancement over about 2 hours. The common bile duct was hyperintense within 10 minutes after injection in all volunteers. CONCLUSION: Gd-EOB-DTPA is safe and efficient for MR imaging of the liver.
Adult↗
[Value of MRI in diagnosis of focal liver lesions].
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Contrast Media↗
Focal liver lesions: characterization with nonenhanced and dynamic contrast material-enhanced MR imaging.
PURPOSE: To evaluate prospectively the diagnostic accuracy of non-enhanced and gadolinium-enhanced magnetic resonance (MR) imaging in characterization of hepatic lesions. MATERIALS AND METHODS: Fifty-five patients with benign and 52 patients with malignant focal liver lesions underwent examination at 1.5 T that comprised nonenhanced and dynamic contrast material-enhanced images. Four experienced radiologists independently read the different sets of images without and with knowledge of clinical history. RESULTS: Receiver operating characteristic analysis showed that dynamic contrast-enhanced MR imaging added information to nonenhanced MR studies and thereby improved distinction between benign and malignant lesions (P < .05). Knowledge of clinical data further improved lesion characterization with nonenhanced and combined nonenhanced and contrast-enhanced MR imaging (P < .05). CONCLUSION: Dynamic contrast-enhanced MR imaging is a useful adjunct for characterization of hepatic lesions. Knowledge of clinical history still has a decisive effect on interpretation of MR images of the liver.
Adult↗
SHU 555A. A new superparamagnetic iron oxide contrast agent for magnetic resonance imaging.
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Dextrans↗
[Superparamagnetic iron particles. The clinical results in the MR diagnosis of liver metastases].
The diagnostic value of superparamagnetic iron particles as a tissue-specific MR contrast medium of the reticulo-endothelial system was studied in 30 patients. All patients had liver metastases (maximally 5 known metastases on MR). The patients were examined on a 1.5 Tesla scanner before and after a slow intravenous injection of iron particles (AMI-25) at a dose of 15 mumol/kg. Contrast injection led to a significant reduction of signal strength in the liver parenchyma (p < or = 0.001) but not in the metastases. Contrast enhanced spin echo sequences (SE 2300/45) provided the most marked liver/tumour contrast, greater than the contrast values of T1- and T2-weighted images (p < or = 0.01). After the intravenous injection of iron particles, small metastases in particular are more easily demonstrated. A new, rapid T2-weighted pulse sequence (PSIF 10/15/15 degrees) results in the elimination of vascular signals and leads to better differentiation between lesions and intrahepatic vessels. The use of superparamagnetic iron particles as an MR contrast medium improves the demonstration of liver metastases.
Contrast Media↗
[A liver tumor model in the rat suitable for experimental MRT].
A malignant tumour was implanted in the livers of 205 rats in the context of an experimental MRT project. The implantation technique of the Novikoff hepatoma is described. Within 10 days of implantation a solitary one-centimetre intrahepatic tumour develops; it is a hypovascular tumour with an invasive periphery and central tumour necrosis. The tumour model is distinguished by a high success rate of 91.1% and is suitable for experimental MRT studies of liver tumours.
Animals↗
Hypervascular liver lesions: differentiation of focal nodular hyperplasia from malignant tumors with dynamic gadolinium-enhanced MR imaging.
The differentiating points between focal nodular hyperplasia (FNH) and malignant hypervascular liver lesions were studied at dynamic gadolinium-enhanced magnetic resonance (MR) imaging. Thirty-six patients with 50 hypervascular lesions (28 FNH, 12 hepatocellular carcinoma, nine metastases, and one cholangiocarcinoma) underwent unenhanced spin-echo (SE) T1- and T2-weighted imaging and T1-weighted gradient-recalled-echo imaging before and repeatedly for 10 minutes after intravenous bolus injection of gadopentetate dimeglumine. On unenhanced SE images, the signal intensity of 25 FNH lesions (89%) and 10 malignant tumors (45%) was homogeneous. A central scar was detected in 12 FNH lesions (43%) and in none of the malignant tumors. On dynamic gadolinium-enhanced images, all lesions had early vigorous enhancement that was homogeneous in 27 FNH lesions (96%) and in seven malignant tumors (32%) (P < .001). After administration of gadopentetate dimeglumine, central scars were seen in 22 FNH lesions (79%) and in one malignant tumor (4%) (P < .001). All FNH lesions (100%) and six malignant tumors (27%) had well-defined enhancement (P < .001). There was overlap in the enhancement pattern between hypervascular malignant lesions and FNH, but by using the combination of unenhanced and enhanced images, they could be distinguished.
Adult↗
Interstitial MR lymphography with iron oxide particles: results in tumor-free and VX2 tumor-bearing rabbits.
OBJECTIVE: MR lymphography with interstitial injection of superparamagnetic iron oxide particles was optimized in normal rabbits by investigating the pattern of signal reduction in lymph nodes as a function of dose and time after administration. The optimized examination procedure was then used in a rabbit tumor model to study the potential of superparamagnetic iron oxide--enhanced MR lymphography in the detection of metastatic lymph node involvement. MATERIALS AND METHODS: The popliteal and iliac lymph nodes of 18 normal rabbits were imaged to study the dose response and time course of the effect of the contrast agent. For the dose response study, six doses of 2-50 mumol of iron per extremity were administered to three animals per dose, and MR images were obtained before and 12 hr after administration. For the time course study, 20 mumol of iron per extremity was administered to four animals, and images were obtained before and 6 hr to 42 days after administration. VX2 tumor-bearing rabbits were examined 12 hr after administration of 20 mumol (10 animals) and 50 mumol (three animals) of iron per extremity. Superparamagnetic iron oxide was injected into the foot pad of the hind limb. T1-, T2-, and proton density-weighted MR images were obtained with a 1.5-T unit. RESULTS: In normal rabbits, a profound and homogeneous loss of signal intensity was found with doses of 2-5 mumol of iron per extremity in popliteal lymph nodes and with doses of 20-30 mumol in the iliac lymph nodes. Superparamagnetic iron oxide caused maximal loss of signal intensity in both popliteal and iliac lymph nodes 12 hr after administration. In tumor-bearing rabbits, different degrees of metastatic displacement of lymph nodes were discernible, and even small metastases (3 mm in diameter) could be visualized when using the optimized examination protocol and the proton density-weighted spin-echo sequence. CONCLUSION: We conclude that interstitial MR lymphography with superparamagnetic iron oxide enables the detection of lymph node metastases and therefore is a promising technique for improved diagnostic imaging of lymph nodes in the staging of tumors.
Animals↗
MR lymphography using iron oxide particles. Detection of lymph node metastases in the VX2 rabbit tumor model.
MR images of the iliac lymph nodes of 25 VX2 carcinoma-bearing rabbits and of 5 tumor-free rabbits were obtained at 1.5 T before and after endolymphatic administration of superparamagnetic iron oxide particles (SPIO) at a dose of 1 mumol Fe per extremity. Imaging results were correlated with histology. In unenhanced images intranodal metastases were not detectable with any of the pulse sequences used and the signal intensities of tumor-free and metastatic lymph nodes did not differ significantly. After administration of the contrast medium, a significant signal loss (p < or = 0.05) occurred in the healthy lymph node tissue, whereas the signal intensity of lymph node metastases remained unchanged. In SPIO enhanced images, the threshold size for detection of lymph node metastases was 2 mm. Metastatic involvement was detected in 28 of the 30 tumorous lymph nodes with the SE 2000/15 sequence but in a smaller number of lymph nodes with the sequences SE 500/22 (n = 27) and 2000/65 (n = 21).
Animals↗
Focal liver lesions: MR imaging with Mn-DPDP--initial clinical results in 40 patients.
Manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate) (DPDP) was evaluated as a contrast agent for magnetic resonance (MR) imaging (1.5 T) of focal liver lesions in 40 patients. Doses of 5 and 10 mumol/kg were administered intravenously. Mn-DPDP-enhanced T1-weighted images were compared quantitatively and subjectively with standard T1- and T2-weighted nonenhanced images. Use of Mn-DPDP resulted in a statistically significant increase in signal intensity of liver parenchyma in T1-weighted images at both doses. No enhancement was seen in metastases, cholangiocarcinomas, or lymphomas, while all hepatocellular carcinomas were enhanced. Enhancement was seen in focal nodular hyperplasia and in regenerative nodules. The lesion-to-liver contrast in Mn-DPDP-enhanced gradient-recalled-echo images was superior to that of all precontrast images (P less than .01). The number of nonenhancing malignant liver lesions detected in spin-echo (SE) images was increased (272 in T2-weighted SE images vs 390 in T1-weighted Mn-DPDP-enhanced SE images). Image interpretation (eg, visualization and demarcation of the lesions) was markedly better in Mn-DPDP-enhanced images than in all precontrast images (P less than .001).
Adult↗
Multisection FLASH: method for breath-hold MR imaging of the entire liver.
One hundred ten patients with various focal liver lesions were imaged with a multisection fast low-angle shot (FLASH) gradient-echo sequence with an echo time of 4.6 msec. This sequence enabled the acquisition of 19 T1-weighted magnetic resonance (MR) images of the liver within a single 26-second breath hold. Patients were also examined with standard T1- and T2-weighted spin-echo (SE) sequences. The multisection FLASH sequence provided significantly higher (P less than .01) liver-spleen contrast, liver-spleen signal-difference-to-noise ratio (SD/N), liver-tumor contrast, and liver-tumor SD/N than the T1-weighted SE sequence but lower values than the T2-weighted SE sequence. Motion artifacts were reduced with the multisection FLASH sequence compared with both SE sequences (P less than .01). The overall image quality of the multisection FLASH images was similar to that of the T1-weighted SE images and superior to that of T2-weighted SE images. The most important characteristics of the multisection FLASH technique in MR imaging of the liver are the high T1 contrast, the prevention of motion artifacts, and a dramatic reduction in imaging time.
Adult↗
MR lymphography with iron oxide particles: dose-response studies and pulse sequence optimization in rabbits.
Superparamagnetic iron oxide (SPIO) particles are a promising contrast agent for MR lymphography. The effect of SPIO on MR imaging of normal lymph nodes and the impact of the size of the dose have not yet been investigated in detail. Therefore, we performed dose-response and pulse sequence optimization studies. MR images of the iliac lymph nodes of 15 normal rabbits were obtained at 1.5 T with 12 different spin-echo (SE) and gradient-echo (GRE) sequences before and after SPIO administration. The contrast agent was injected into a femoral lymph vessel at five different doses (0.02-2.0 mumol Fe/animal). The dose that reduced signal intensity by half (ED50) was determined for each sequence, and images were evaluated qualitatively. Doses of 0.2 and 1.0 mumol Fe caused a complete signal loss throughout the lymph node. In this dose range, proton density-weighted SE sequences showed a profound signal loss (ED50, 0.132 mumol Fe), and lymph nodes were sharply demarcated. The GRE sequences (ED50, 0.027-0.070 mumol Fe) and the T2-weighted SE sequence (ED50, 0.014 mumol Fe) showed an even more pronounced signal loss but insufficient anatomic resolution. Underdosing (less than or equal to 0.1 mumol Fe) caused only a focal signal loss in the lymph nodes. Oversaturation (2.0 mumol Fe for SE sequences, greater than or equal to 1.0 mumol Fe for GRE sequences) led to image distortion and did not allow assessment of lymph node morphology. Our results show that optimal contrast enhancement of normal lymph nodes with SPIO can be achieved in the dose range of 0.2-1.0 mumol Fe on proton density-weighted SE sequences. Our results may serve as a basis for further development of noninvasive MR lymphography.
Animals↗
Dynamic MR imaging of the abdomen with gadopentetate dimeglumine: normal enhancement patterns of the liver, spleen, stomach, and pancreas.
To show the normal contrast enhancement patterns of the upper abdominal organs, dynamic gadopentetate dimeglumine-enhanced MR imaging of the upper abdomen was performed in 48 patients. Although all patients were originally examined for focal hepatic lesions, none of them had diffuse parenchymal disease of any of the examined organs. Dynamic gadopentetate dimeglumine-enhanced MR imaging was done by using a heavily T1-weighted gradient-echo sequence (100/5 [TR/TE], 80 degrees flip angle) performed before, and repeatedly for a period of 10 min after, an IV bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Signal enhancement in each of the organs was calculated by measuring the signal intensity before and after administration of contrast medium. All organs showed signal enhancement within the first 2 min (p less than .001) and a continuous decline thereafter. The enhancement of the pancreas, liver, stomach wall, spleen, and renal cortex reached peaks of 75%, 78%, 96%, 144%, and 216%, respectively, 45 sec after administration of contrast medium. Liver and pancreas showed a homogeneous enhancement pattern throughout the examination. The spleen appeared heterogeneous during the first 60 sec and homogeneous thereafter. Two zones could be distinguished on the contrast-enhanced images of the stomach wall: an enhanced inner zone and an unenhanced outer zone. We conclude that homogeneous enhancement of the liver and pancreas, early heterogeneous enhancement of the spleen, and enhancement of the inner gastric wall are normal patterns on dynamic gadopentetate dimeglumine-enhanced MR images.
Contrast Media↗
[Diagnosis of focal liver lesions. The value of imaging systems].
Selection of the suitable modality for the detection or differential diagnosis of focal liver lesions must consider, in addition to its accuracy, such factors as on-site availability, the costs involved, and the stress to the patient. The preferred screening technique is ultrasonography which, however, has a high failure rate, in particular in the case of small lesions. In many cases computed tomography (CT) permits the correct diagnosis to be established. Both CT and ultrasonography make possible selective percutaneous biopsy. Magnetic resonance imaging is one of the most sensitive procedures, but is often not available - even in specialized centers. With this technique or blood pool scanning, hepatic hemangiomas found incidentally can be diagnosed in 90% of the cases. The diagnosis of focal modular hyperplasia continues to be difficult.
Diagnosis, Differential↗
[MR tomography of the liver at 1.5 tesla. The value of T1-weighted imaging with a fast multislice gradient-echo sequence during respiratory standstill].
The diagnostic value of a fast multislice gradient-echo sequence was compared with that of conventional spin-echo sequences in a prospective study of 76 patients. With the multislice gradient-echo sequence, the entire liver can be examined in less than 3 minutes since five sections can be imaged during one breath-holding period. The strongly T1-weighted gradient-echo sequence (GRE 100/5/80 degrees) yields a significantly better T1-contrast than the T1-weighted spin-echo sequence (SE 500/15) (p less than 0.01) and thus improves the visualization of liver lesions. Another major advantage of the fast gradient-echo sequence is the pronounced reduction of motion artefacts.
Chi-Square Distribution↗