[Magnetic resonance imaging of the pancreas].
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Female↗
Biomedical subjects
A Tanimoto
Publications and source records attributed to A Tanimoto.
[Percutaneous transluminal angioplasty in renovascular hypertension--long-term follow-up].
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Adolescent↗
Amplification of the amyE-tmrB region on the chromosome in tunicamycin-resistant cells of Bacillus subtilis.
In a class of tunicamycin-resistant mutants (tmrA7) of Bacillus subtilis, the production of extracellular alpha-amylase is increased by about five fold. The tmrA7 characteristics (tunicamycin resistance and hyperproduction of extracellular alpha-amylase) can be transferred to recipient cells by transformation. In the transformants and the original tmrA7 mutant, typical amplification of the region from 4 kb upstream of the amyE gene to the tmrB gene on the chromosome was detected. The repeating unit, 16 kb in size, repeats tandemly about five and ten times in the mutant and transformants, respectively, and the alpha-amylase production is proportional to the copy number of the amyE gene. Simultaneous amplification of the tmrB gene, which is responsible for tunicamycin resistance in the multicopy state, and the alpha-amylase structural gene (amyE) seems to be the cause of the pleiotropy of the tmrA7 mutation.
Bacillus subtilis↗
Amplification and deletion of the amyE+-tmrB+ gene region in a Bacillus subtilis recombinant-phage genome by the tmrA7 mutation.
A 22.4-kilobase DNA fragment containing the tmrA7-amyR2-amyE+-tmrB+-aroI+ region of the Bacillus subtilis N7 chromosomal DNA was cloned into a recombinant B. subtilis bacteriophage, p11-AA248. The amyE+-tmrB+ gene region, approximately 12.6 kilobases, in the phage genome was amplified in a tunicamycin-resistant (Tmr) Amy+ AroI+ transductant of B. subtilis by p11-AA248. On the other hand, the amyE+-tmrB+ region in the genomes of 80 to 90% of the phage particles was deleted when the phages were induced from the Tmr Amy+ AroI+ transductants by treatment with 1.0 micrograms of mitomycin C per ml. From analyses of the physical maps and DNA nucleotide sequences in the junction region of the deleted phage genome and the parental DNA fragments, it is suggested that the deletion occurred within a direct repeat sequence composed of 18 base pairs. The endpoints of the amplified gene region seemed to be closely related to both terminal regions of the deleted DNA.
Bacillus subtilis↗
Essential structure in the cloned transforming DNA that induces gene amplification of the Bacillus subtilis amyE-tmrB region.
Bacillus subtilis B7, a mutant which acquired gene amplification of the amyE-tmrB region, showed, as a result, hyperproductivity (about a 5- to 10-fold increase) of alpha-amylase and tunicamycin resistance. The mutational character was transferred to recipient cells by competence transformation. A 14-kilobase (kb) EcoRI chromosomal DNA fragment of strain B7 was found to have the transforming activity. We cloned a 6.4-kb EcoRI fragment on a phage vector lambda Charon 4A through a spontaneous deletion of 7.6 kb from the 14-kb fragment and subcloned a 1.6-kb HindIII fragment on pGR71. The cloned 6.4-kb EcoRI and 1.6-kb HindIII fragments retained the transforming activity of inducing gene amplification of the amyE-tmrB region. At the junction point (J) of the repeating units (16 kb), the tmrB gene was linked to a DNA region (M) located 4 kb upstream of amyE. The essential structure of the cloned, transforming (gene amplification-inducing) DNA was deduced to be that around J. The subcloned 1.6-kb HindIII fragment that retained the transforming activity was shown to be almost solely composed of the tmrB-J-M region. In addition, the DNA sequence around J was determined.
Bacillus subtilis↗
[Embolization of renal arteriovenous malformations].
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Adult↗
[Imaging of small renal cell carcinomas].
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Aged↗
[The value of epinephrine-enhanced renal arteriography in the diagnosis of small renal cell carcinomas].
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Aged↗
Diagnosis of fatty liver with MR imaging.
The diagnosis of fatty liver with magnetic resonance (MR) imaging was evaluated in experimental rat models of simple fatty infiltration and fatty liver with hepatocellular injury. T1 and T2 were measured ex vivo and correlated with the histologic degree of fatty infiltration. Enhancement of fatty liver with four different cells-specific contrast agents was studied with ex vivo relaxometry and in vivo MR imaging. Quantitative analysis of conventional and chemical shift MR images was correlated with biochemically determined fat content of the liver. Diet-induced simple fatty infiltration of the liver caused a decrease in T1 of 15%, whereas the T1 of L-ethionine-induced fatty liver with hepatocellular injury increased by 12%. T2 showed a positive correlation with the degree of fatty infiltration in both models. Cell-specific hepatobiliary contrast agents showed the same liver uptake and relaxation enhancement in fatty livers as in normal livers. Conventional T1-weighted images and chemical shift images showed good correlation (r = .83 and .80, respectively) between signal intensity and the degree of fatty infiltration. However, only chemical shift imaging was reliable in the diagnosis of fatty liver.
Acetates↗
Enhancement of tumor-liver contrast-to-noise ratio with gadobenate dimeglumine in MR imaging of rats.
The efficacy for tumor detection of the hepatocyte-specific contrast agent gadobenate dimeglumine (gadolinium-BOPTA/Dimeg) was evaluated in four different experimental tumor models in rats. Histologic findings were correlated with quantitative data derived from ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Noninfiltrating tumors showed maximal enhancement of liver parenchyma 5-10 minutes after contrast agent administration, with a plateau over the next 30 minutes. In contrast, infiltrating tumors, which caused hepatocellular injury and inflammatory changes, delayed maximal enhancement of tumor-free parenchyma by 15-20 minutes. Nonspecific tumor enhancement depended on tumor vascularity and occurred in the early phase after contrast agent administration. Despite differences in specific enhancement of tumor-free parenchyma and nonspecific tumor enhancement, tumor-liver contrast-to-noise ratios increased 96%-248% in all tumor models 30 minutes after intravenous administration of 75 mmol/kg Gd-BOPTA/Dimeg. Gd-BOPTA/Dimeg enhanced tumor conspicuity independently of the histologic characteristics of the tumor.
Animals↗
Evaluation of hepatocyte-specific paramagnetic contrast media for MR imaging of hepatitis.
The hepatocyte-specific paramagnetic magnetic resonance (MR) contrast agents manganese-DPDP [N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'bis-(phosphate)] and gadobenate dimeglumine were used for diagnosing chemically induced hepatitis in rats. Ex vivo liver tissue relaxation times and in vivo MR image signal-to-noise ratios were compared before and after contrast agent administration. Ex vivo relaxometry and in vivo MR imaging showed that Mn-DPDP enhanced normal and diseased livers to the same degree at all time points from 5 to 120 minutes. Gadobenate dimeglumine showed reduced T1 and T2 enhancements in hepatitis relative to those of normal liver, in the early phase (5-30 minutes). However, these effects are offsetting, and as a result, MR imaging failed to allow distinction of diseased from normal livers. This surprising result observed in vivo was in fact predicted by applying the Bloch equation to our ex vivo data. Our results show that detection and quantitation of hepatitis with MR imaging enhanced with paramagnetic cell-specific contrast agents will be more difficult than anticipated.
Acute Disease↗
Enhanced tumor detection in the presence of fatty liver disease: cell-specific contrast agents.
It is assumed that hepatobiliary, cell-specific contrast agents will be adversely affected by the presence of diffuse liver disease. The diagnostic efficacy for tumor detection in the presence of fatty liver disease was experimentally studied at contrast-enhanced magnetic resonance (MR) imaging with manganese-DPDP (N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis[phosphate]) and gadobenate dimeglumine (Gd-BOPTA/dimeg) and compared with conventional and chemical shift imaging. Carcinosarcoma was implanted into the liver of rats, and fatty liver was induced with L-ethionine. Without contrast agents, the tumor-fatty liver contrast-to-noise ratio (C/N) was increased on T1-weighted and decreased on T2-weighted MR images relative to tumor-bearing control rats without fatty liver. Chemical shift imaging (phase-contrast method) increased the tumor-fatty liver C/N from 2.3 +/- 1.0 to 6.1 +/- 1.7 (P < .001). Mn-DPDP and Gd-BOPTA/dimeg increased the tumor-fatty liver C/N from -5.4 +/- 1.6 to -11.0 +/- 1.9 and -9.8 +/- 3.4, respectively (P < .001). The hepatobiliary, cell-specific contrast agents were equally effective in both fatty and non-fatty liver and outperformed both chemical shift and conventional MR imaging in detecting liver tumors.
Animals↗
Contrast-enhanced MR imaging of diffuse and focal splenic disease with use of magnetic starch microspheres.
The diagnostic value of magnetic starch microspheres (MSM), a new superparamagnetic contrast agent, was studied in experimental models of diffuse and focal splenic disease in rats by means of ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Owing to small differences in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor-bearing animals from control animals by signal-to-noise ratios (SNRs) obtained with T1- and T2-weighted spin-echo sequences. One hour after injection of 20 mumol/kg MSM, lymphomatous spleen showed significantly (P < .001) reduced enhancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 +/- 1.7) could be easily differentiated from control animals (SNR: 5.5 +/- 0.6) on T2-weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enhancement of nontumorous splenic tissue, whereas relaxation times of tumors were not different before and after contrast agent injection. On T2-weighted images (2,000/45), the tumor-spleen contrast-to-noise ratio increased from 4.8 +/- 1.6 to 21.8 +/- 1.9 (+354%), improving conspicuity of splenic tumors. The results show that MSM-enhanced MR imaging improves the detection of diffuse and focal splenic disease.
Animals↗
Time after excision and temperature alter ex vivo tissue relaxation time measurements.
Previously unreported effects of tissue storage were recently observed in the authors' experimental magnetic resonance (MR) studies. To evaluate the effect of elapsed time after excision and storage temperature on tissue relaxation time measurements, tissue samples from the liver, pancreas, kidney, testis, spleen, and brain were obtained in rats. T1 and T2 were first measured within 5 minutes of excision, and between subsequent measurements, tubes were kept in a water bath at 40 degrees C, at room temperature (28 degrees C), or in an ice bath (4 degrees C). Cellular and organellar integrity was assessed with electron microscopy and correlated with the MR findings. At 40 degrees C (20-MHz spectrometer), the T1 of liver decreased from 280 msec +/- 8 to 212 msec +/- 10 during the first 60 minutes; the T1 of pancreas decreased from 276 msec +/- 3 to 208 msec +/- 2. Other tissues showed less than a 5% decrease in T1. T2 changes were smaller than T1 changes in all tissues. Electron microscopy of pancreatic acinar cells showed postmortem changes in mitochondria evolving over the first 60 minutes after death. Manganese loading experiments implicated mitochondrial manganese stores in the observed enhanced postmortem decrease in T1. This study calls into question reported relaxation time data for liver and pancreas. MR studies of excised tissues must account for time and temperature to prevent systematic experimental errors.
Animals↗
Effects of spatial distribution on proton relaxation enhancement by particulate iron oxide.
The proton relaxation effect of superparamagnetic iron oxide (SPIO) particles under varying conditions of spatial distribution was investigated with use of phantoms. Agar phantoms containing various concentrations of SPIO or gadopentetate dimeglumine, with and without Sephadex beads, were studied. Phantoms with Sephadex had a heterogeneous spatial distribution of iron oxide, comparable to liver tissue in vivo. Relaxometry at 0.47 T showed decreased T2 relaxivity of SPIO in Sephadex phantoms compared with that in agar phantoms without Sephadex. On T2-weighted images obtained at 1.5 T, the signal intensity of Sephadex phantoms showed less SPIO relaxation effect than that of plain agar phantoms. Unlike SPIO, gadopentetate dimeglumine showed the same relaxivities and signal intensity in plain agar and Sephadex phantoms. The results show that the T2 relaxation effect of iron oxide depends on its spatial distribution. A heterogeneous spatial distribution, as in intact liver tissue, diminishes the T2 relaxivity of iron oxide particles.
Agar↗
Performance of Gd-EOB-DTPA and superparamagnetic iron oxide particles in the detection of primary liver cancer: a comparative study by alternative free-response receiver operating characteristic analysis.
The performance of gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) and superparamagnetic iron oxide (SPIO) particles in detecting liver cancer was compared using alternative free-response receiver operating characteristic (AFROC) analysis, which allowed observers to indicate both the confidence level and the locations of all perceived abnormalities. Axial T1-weighted MR images (1.5 T) pre/post Gd-EOB-DTPA (25 mumol/kg) injection were obtained for 12 rats with chemically induced liver tumors (64 tumors). T2-weighted images (T2WI) were obtained pre/post SPIO (10 mumol/kg) injection for the same animal. Liver signal-to-noise ratio (SNR), tumor-liver contrast-to-noise ratio (CNR), and histopathologic sections corresponding to MR images were obtained. In AFROC, the location and the confidence level for each tumor were indicated independently on MR images by four radiologists. By plotting true-positive fraction and probability of false-positive per image, the area under the AFROC curve (A1) was estimated and statistically analyzed between each sequence. Either drug significantly improved tumor-liver CNR (P < .001) and tumor detection (diameter < or = 6 mm; P < .05). Gd-EOB-DTPA significantly (P < .05) improved the A1 in T1WI. There was no A1 difference between T2WI + SPIO and T1WI + Gd-EOB-DTPA. Gd-EOB-DTPA-enhanced T1WI showed the same performance as SPIO-enhanced T2WI in detecting liver tumors.
Animals↗
Enhancement of phase-contrast MR angiography with superparamagnetic iron oxide.
The effect of superparamagnetic iron oxide particles (AMI-227) was assessed in three-dimensional (3D) phase-contrast (PC) MR angiography (MRA), with various scanning parameters for rats at 1.5 T. The blood T1 and T2 before and after 20 micromol Fe/kg of AMI-227 injection were measured sequentially at .47 T. The visualization of abdominal aorta, renal artery, inferior vena cava, and portal vein was respectively evaluated before and after AMI-227 injection qualitatively by the four confidence levels and quantitatively by analysis of signal-to-noise ratio (SNR) of vessels. The blood T1 and T2 were sufficiently shortened for at least 1 hour after AMI-227 injection. The visualization of each vessel was improved by AMI-227 at various velocity encoding (VENC) value, suggesting the extended application of PC-MRA in various conditions. The optimal flip angle was increased from 20 degrees to 30 degrees in higher VENC after AMI-227 injection, resulting in higher signal from blood flow. Quantitative analyses showed that the optimal flip angle to achieve the maximum SNR seemed to be 20 degrees in unenhanced images, but the optimal flip angle of the high speed flow was increased by contrast enhancement. The postcontrast PC-MRA provides the increased sensitivity of slow flow components, even with a high VENC gradient. AMI-227 can significantly improve SNR to blood vessels during 3D-PC-MRA with various scanning parameters.
Animals↗
Small renal cell carcinoma: MRI with pathologic correlation.
The MRI features of small renal cell carcinomas (RCCs) were retrospectively reviewed and correlated with histology in 24 patients. MRI features on both T1- and T2-weighted images were classified into hypointensity, isointensity, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correlated with MR signal intensities. Alveolar tumors showed hypointensity to isointensity on T1-weighted image and isointensity to hyperintensity on T2-weighted image. In contrast, all papillary tumors showed hypointensity on T2-weighted image. Four of six tumors with hypointensity on T2-weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, there were two papillary RCCs that showed hypointensity on T2-weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papillary RCC is associated with T2-hypointense appearance as well as hemosiderin deposition, hemorrhage, and necrosis.
Adult↗