[MRI imaging in less than one second: Turbo flash].
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Humans↗
Biomedical subjects
A Rahmouni
Publications and source records attributed to A Rahmouni.
Normal age-related patterns of cellular and fatty bone marrow distribution in the axial skeleton: MR imaging study.
Knowledge of age-related distribution patterns of cellular and fatty marrow is critical to the interpretation of magnetic resonance (MR) imaging studies. To determine such patterns, the authors retrospectively evaluated 70 examinations each of the skull, cervical spine, thoracic spine, lumbar spine, pelvis, and proximal femur (420 examinations) in patients without known bone marrow abnormality who ranged in age from 6 months to older than 70 years. Two to four distinct patterns were identified in each anatomic area on spin-echo images obtained with a short repetition time and a short echo time. The relative frequency of the patterns for different age groups is consistent with the known physiologic conversion from cellular to fatty marrow with advancing age. Knowledge of these patterns should help in the interpretation of MR images of the axial skeleton.
Adult↗
Structure of the intrastrand cis-[Pt(NH3)2(d(GpCpG))] adduct in a dodecanucleotide duplex: I. A 1H and 31P n.m.r. study.
The structure of an intrastrand cis-[Pt(NH3)2(d(GpCpG))] adduct in a dodecanucleotide duplex has been investigated by using ultraviolet absorption, circular dichroism, 1H and 31P n.m.r. The binding of cis-DDP does not inhibit the formation of a duplex but it induces a lowering of congruent to 26 degrees C of its melting temperature. A broadening of the 1H spectrum prevents an accurate analysis of the platination site. Nevertheless, by considering its thermal behavior and the number of imino protons a model of structure of the platinated duplex is proposed in which the central C.G. pair is disrupted and a neighboring C.G pair is very accessible or distorted. The environment of two phosphate groups is disturbed by the cis-DDP binding.
Circular Dichroism↗
Structure of the intrastrand cis-[Pt(NH3)2(d(GpCpG))] adduct in a dodecanucleotide duplex: II. A molecular mechanics modeling study.
Molecular mechanics modeling has been carried out for the intrastrand cis-[Pt(NH3)2(d(pGpCpG))] adduct in a dodecanucleotide duplex. In a first step, an analysis of the conformation of a platinated trinucleotide shows the tendency of the two chelating guanines to take respectively anti-syn or syn-anti positions and the role of phosphate-platinum amino group interactions. In a second step, duplex structures are examined. The distortions induced by platination are especially analysed for kinked and unkinked forms of the dodecanucleotide. In all models the central C.G pair in the platination site is disrupted and the double helix is more disturbed on the 5' side of this site than on the 3' side. Most of the structural features arising from the modeling are in agreement with the conclusions of an n.m.r. study reported in the preceding paper.
Binding Sites↗
Reaction of nucleic acids with cis-diamminedichloroplatinum(II): interstrand cross-links.
In the reaction of cis-diamminedichloroplatinum(II) (cis-DDP) with double-helical (dC-dG)4.(dC-dG)4 or (dC-dG)5.(dC-dG)5, intrastrand and interstrand cross-links between two guanine residues are formed. This is shown by gel electrophoresis in denaturing conditions of the reaction products and by high-performance liquid chromatography (HPLC) analysis of the products digested with nuclease P1. In the reaction of cis-DDP and poly(dG-dC).poly(dG-dC), at relatively low levels of platination, it is mainly interstrand cross-links between two guanine residues that are formed. This is shown by HPLC analysis of the nuclease P1 digest and by gel electrophoresis in denaturing and nondenaturing conditions of the platinated polymer after cleavage with the restriction enzyme HhaI. Moreover, the antibodies to platinated poly(dG-dC).poly(dG-dC) cross-react with the interstrand cross-linked (dC-dG)4 or (dC-dG)5 but not with the intrastrand cross-linked (dC-dG)4 or (dC-dG)5. These antibodies cross-react with platinated natural DNA. The amount of interstrand cross-links deduced from radioimmunoassays (0.5% of the total bound platinum) is lower than that (2%) deduced by gel electrophoresis in denaturing conditions of a platinated DNA restriction fragment. By gel electrophoresis, it is also shown that in vitro the isomer trans-DDP is more efficient in forming interstrand cross-links than cis-DDP.
Antibodies↗
Comparison between poly(dG-dC).poly(dG-dC) and DNA modified by cis-diamminedichloroplatinum (II): immunological and spectroscopic studies.
The importance of the base composition and of the conformation of nucleic acids in the reaction with the drug cis-diamminedichloroplatinum(II) has been studied by competition experiments between the drug and several double-stranded polydeoxyribonucleotides. Binding to poly(dG).poly(dC) is larger than to poly (dG-dC).poly(dG-dC). There is no preferential binding in the competition between poly(dG-dC).poly(dG-dC), poly(dA-dC).poly(dG-dT) and poly(dA-dG).poly(dC-dT). In the competition between poly(dG-dC).poly (dG-dC) (B conformation) and poly(dG-br5dC).poly(dG-br5dC) (Z conformation), the drug binds equally well to both polynucleotides. In natural DNA, modification of guanine residues in (GC)n.(GC)n sequences by the drug has been revealed by the inhibition of cleavage of these sequences by the restriction enzyme BssHII. By means of antibodies to platinated poly(dG-dC), it is shown that some of the adducts formed in platinated poly(dG-dC) are also formed in platinated pBR322 DNA. The type of adducts recognized the antibodies is not known. Thin layer chromatography of the products after chemical and enzymatic hydrolysis of platinated poly(dG-dC) suggests that interstrand cross-links are formed. Finally, the conformations of poly(dG-dC) modified either by cis-diamminedichloroplatinum(II) or by trans-diamminedichloroplatinum (II) have been compared by circular dichroism. Both the cis-isomer and the trans-isomer stabilize the Z conformation when they bind to poly(dG-m5dC) in the Z conformation. When they bind to poly(dG-m5dC) in the B conformation, the conformations of poly(dG-m5dC) modified by the cis or the trans-isomer are different. Moreover, the cis-isomer facilitates the B form-Z form transition of the unplatinated regions while the trans-isomer makes it more difficult.
Binding, Competitive↗
Sclerosed liver hemangioma mimicking malignant tumor at MR imaging: pathologic correlation.
This case report illustrates atypical magnetic resonance (MR) imaging findings in a liver hemangioma mimicking a malignant lesion--lower signal intensity than cerebrospinal fluid on T2-weighted spin-echo images and lack of early enhancement on dynamic contrast material--enhanced gradient-echo images. Pathologic analysis demonstrated nearly total replacement of the vascular cavities by dense fibrous tissue. In this rare, sclerosed form, this lesion could not be defined as a hemangioma with MR imaging.
Adult↗
Chronic hepatic encephalopathy due to spontaneous splenorenal shunt: successful treatment by transhepatic shunt embolization.
A spontaneous splenorenal shunt, leading to chronic hepatic encephalopathy, was treated by transhepatic occlusion with coils and Enbucrylate. There were no complications. Hepatic encephalopathy subsided.
Chronic Disease↗
Orthotopic liver transplantation in the presence of partial or total portal vein thrombosis: problems in diagnosis and management.
From January 1989 to May 1992, 70 orthotopic liver transplantations (OLT) were performed in 69 patients, 53 of whom had cirrhosis (77%). Eleven patients (16%) had preoperative partial or total portal vein thrombosis (PVT). Ten of these patients had cirrhosis of various causes. PVT was total in three cases and partial in eight. Total PVT was detected preoperatively in all three cases. By contrast, partial PVT was diagnosed preoperatively in only three of the eight cases. In the five other cases of partial PVT, the obstruction was discovered intraoperatively during dissection of the portal vein. Surgical management of PVT consisted of phlebothrombectomy in ten cases followed by usual end-to-end portal anastomosis in nine cases and anastomosis of the graft's portal vein to the splenomesenteric confluence in one case. Atypical anastomosis of the graft's portal vein to a dilated choledocal vein was performed in one case of total PVT. There were no deaths or complications related to the presence of preoperative PVT or to its management. One patient died postoperatively of primary graft nonfunction at day 5. One patient had arterial thrombosis 3 months after OLT and was successfully retransplanted. Two patients died of recurrent carcinoma 3 and 7 months after OLT. Eight patients are alive 4 to 39 months after OLT. We conclude from this series that (1) the prevalence of preoperative PVT among patients transplanted for advanced cirrhosis may be high (19% of the cirrhotics in this series); (2) PVT is often partial and so difficult to diagnose preoperatively; (3) PVT, even when total, can be managed successfully during surgery and does not seem to affect survival.
Adult↗
Hyperintense benign liver lesions on spin-echo T1-weighted MR images: pathologic correlations.
BACKGROUND: To determine the incidence of hyperintensity on T1-weighted spin echo (SE) images in benign liver lesions, value of fat-suppressed magnetic resonance (MR) imaging for the detection of fat within these lesions, and the causes of hyperintensity by correlation to pathologic examinations. METHODS: Five hundred forty-nine patients with 805 benign liver lesions including 585 hemangiomas, 188 focal nodular hyperplasias (FNHs), 14 hepatic adenomas (HAs), 14 focal fatty infiltrations (FFIs), two biliary cystadenomas, and two hemorrhagic cysts were examined by T2-weighted and T1-weighted SE MR imaging. For hyperintense lesions on T1-weighted SE images, fat-suppressed images were obtained by selective presaturation of fat. RESULTS: Thirty-two lesions (four FNHs, 10 HAs, 14 FFIs, two biliary cystadenomas, and two hemorrhagic cysts) appeared hyperintense on T1-weighted SE images; 21 of these became hypointense on the fat-suppressed T1 weighted SE images (one FNH, six HAs, and 14 FFIs) and contained fat at pathological examination. The other 11 lesions remained hyperintense on fat-suppressed T1-weighted SE images and had no fat deposition. Causes of hyperintensity in these cases were sinusoidal dilatation, copper deposition, hemorrhage, and high protein content. CONCLUSION: Among benign liver lesions, hyperintensity on T1-weighted SE images is rare (3.9%). Causes of this hyperintensity are fat deposition, copper accumulation, sinusoidal dilatation, bemorrhage, and high protein content. Fat-suppressed imaging can distinguish fat deposition from other causes of hyperintensity.
Adenoma↗
Castleman disease mimicking liver tumor: CT and MR features.
We report the CT and MR features of two localized abdominal forms of Castleman disease mimicking hypervascular liver tumors due to their unusual location in the porta hepatis and the portacaval space. The MR appearance of Castleman lymph nodes is emphasized, including their characteristics on dynamic turbo-fast low angle shot (FLASH) sequences after Gd-DOTA bolus injection. Our report suggests that the CT and MR features of Castleman lymph nodes in these locations cannot enable their differentiation from other hypervascular masses such as benign liver tumors.
Adult↗
Accuracy of in-vivo assessment of prostatic volume by MRI and transrectal ultrasonography.
More accurate noninvasive estimation of prostate size is important in therapeutic trials for benign prostatic hyperplasia. The accuracy of MRI and transrectal ultrasound (TRUS) in assessing prostate weight was evaluated in 48 patients who underwent radical prostatectomy for stage A or B cancer. The volume derived from the wet weight of the freshly excised specimen was used as a reference. We compared that volume with volume estimates derived from the three-axis linear dimension measurement by MRI and TRUS using a tissue density of 1.05 g/cc and the standard formula for an ellipsoid object. Prostate and seminal vesicle volumes were also computed by contouring T2-weighted 5 mm thick contiguous MR images using a semiautomatic edge detection program and pixel summation. Three-axis volume MRI method versus volume from wet weight has slightly less scatter than TRUS three-axis method (r = 0.85 vs r = 0.81). Contoured MR volume method has the least scatter r = 0.93, statistically better than the linear axis method. Contoured MRI volumetric analysis appears superior to linear MRI or TRUS methods in estimating true prostate volume.
Adenocarcinoma↗
MRI of intralesional hemolysis in focal nodular hyperplasia of the liver.
A case of Kasabach-Merritt syndrome caused by focal nodular hyperplasia of the liver is presented with atypical magnetic resonance findings due to intratumoral hemosiderin deposition. The high sensitivity of magnetic resonance imaging for iron served to identify the site of hemolysis in this patient with Kasabach-Merritt syndrome.
Adult↗
Unusual complication of liver irradiation: acute thrombosis of a main hepatic vein: CT and MR imaging features.
The pathologic changes resulting from liver irradiation include congestion, fibrosis, and veno-occlusive disease. We report an unusual complication of radiation induced injury: acute thrombosis of a main hepatic vein within the radiation port. CT and MR features are described and the etiology of this unusual complication is discussed.
Acute Disease↗
[Imaging of the recurrence of colorectal cancer].
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Colonic Neoplasms↗