bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of gadolinium chelates in MR imaging of the spine
Authors: Bradley Wiliam G. 
Published: March 2007

AbstractSpinal disease can be divided into intramedullary, extramedullary‐intradural, and extradural compartments. In the cord (intramedullary compartment), gadolinium chelates are useful to diagnose primary and metastatic tumors, inflammation, and demyelination, and to evaluate syringomyelia when a Chiari I malformation is not present. In the extra‐medulullary‐intradural compartment, gadolinium chelates are useful for the diagnosis of drop metastases, meningiomas, and schwannomas. In the extradural compartment, gadolinium chelates are most useful to distinguish recurrent disc herniation from epidural fibrosis in the postoperative back and may be useful to diagnosis the soft tissue component of osseous metastases.
Contrast agents for MR imaging of the liver
Authors: Low Russell N. 
Published: March 2007

AbstractThe evolution of contrast agents for MR imaging of the liver has proceeded along several different paths with the common goal of improving liver‐lesion contrast. These contrast agents are used to accentuate the inherent differences in liver‐lesion signal intensity through differential enhancement of proton relaxation within adjacent tissues. Contrast agents used for hepatic MR imaging can be broadly categorized into those that target the extracellular space, the hepatobiliary system, and the reticuloendothelial system. Although only a small number of liver contrast agents are currently available, others are rapidly proceeding through clinical trials and may soon be added to our clinical armamentarium. This article will briefly review the current clinical experience with these agents, discussing their mechanism of contrast enhancement, pharmacokinetics, and efficacy in the evaluation of focal liver lesions.
Iron oxide‐enhanced MR lymphography: The evaluation of cervical lymph node metastases in head and neck cancer
Authors: Anzai Yoshimi , Prince Martin R. 
Published: March 2007

AbstractAccurate diagnosis of cervical lymph node metastasis is challenging, even with the latest computed tomography or MR equipment and technique. The lack of definitive criteria for distinguishing metastatic from benign nodes is a serious shortcoming of current imaging options. Dextran‐coated, ultrasmall superparamagnetic iron oxide is a new MR contrast agent, which accumulates in the reticuloendothelial system of lymph nodes. Small iron oxide particles are taken up by macrophages within normal functioning nodes, reducing their signal on postcontrast MR because of the magnetic susceptibility effects of iron oxide. Metastatic nodes, on the other hand, remain high in signal on postcontrast T2*‐weighted gradient echo images. Early clinical experience in cancer patients suggests that iron oxide‐enhanced MR lymphography is a valuable imaging technique that may improve diagnostic accuracy for nodal metastases. This article reviews development of superparamagnetic iron oxide compounds, their imaging characteristics, and clinical experience for evaluating head and neck cancer metastases.
Modeling tracer kinetics in dynamic Gd‐DTPA MR imaging
Authors: Tofts Paul S. 
Published: March 2007

AbstractThree major models (from Tofts, Larsson, and Brix) for collecting and analyzing dynamic MRI gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA) data are examined. All models use compartments representing the blood plasma and the abnormal extravascular extracellular space (EES), and they are intercompatible. All measure combinations of three parameters: (1) kpsρ is the influx volume transfer constant (min−1), or permeability surface area product per unit volume of tissue, between plasma and EES; (2) ve is the volume of EES space per unit volume of tissue (0 < ve < 1); and (3) kep, the efflux rate constant (min−1), is the ratio of the first two parameters (kep = kpsρ/ve). The ratio kep is the simplest to measure, requiring only signal linearity with Gd tracer concentration or, alternatively, a measurement of T1 before injection of Gd (T10). To measure the physiologic parameters kpsρ and ve separately requires knowledge of T10 and of the tissue relaxivity R1 (≈︁ in vitro value).
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
Authors: Tanimoto Akihiro , Satoh Yoshinori , Yuasa Yuji , Jinzaki Masahiro , Hiramatsu Kyoichi 
Published: March 2007

AbstractThe performance of gadolinium‐ethoxybenzyl‐dieth‐ylenetriaminepentaacetic 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 μmol/kg) injection were obtained for 12 rats with chemically induced liver tumors (64 tumors). T2‐weighted images (T2WI) were obtained pre/post SPIO (10 μmol/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 ≤ 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.
MR signal intensity changes in hepatic parenchyma with ductal dilation caused by intrahepatic cholangiocarcinoma
Authors: Yoshimitsu Kengo , Honda Hiroshi , Kaneko Kuniyuki , Kuroiwa Toshiro , Fukuya Tatsuro , Irie Hiroyuki , Kajiyama Kiyoshi , Takenaka Kenji , Masuda Kouji 
Published: March 2007

AbstractMR images of the liver in 13 patients with surgically proven intrahepatic cholangiocarcinoma were reviewed retrospectively and correlated to the histologic analysis of surgical specimens. We paid special attention to the peripheral liver tissue with ductal dilation but without tumorous involvement. High signal intensity was observed in the hepatic parenchyma with ductal dilation on T1‐weighted spin‐echo images (8 of 12) and spoiled gradient‐recalled echo images (seven of seven), as compared with the contralateral hepatic lobe without duct dilation. The high signal intensity was not suppressed with fat saturation and showed enhancement after administration of contrast (11 of 12). Concurrent portal venous obstruction did not have significant effect on these findings (P < .05). Correlation with pathologic specimens suggested that this enhancement was associated with periportal fibrosis. The etiology of the high signal intensity on unenhanced spin echo or gradient‐recalled T1‐weighted image remains unclear. Radiologists should recognize these findings and should distinguish these from tumor involvement or the arterial buffer response caused by portal venous obstruction.
Ampullary carcinoma: Demonstration by current MR techniques
Authors: Semelka Richard C. , Kelekis Nikolaos L. , John Gesine , Ascher Susan M. , Burdeny Derek , Siegelman Evan S. 
Published: March 2007

AbstractThe objective of this study was to demonstrate the appearance of ampullary carcinoma using current MR techniques, including fat suppression, gadolinium enhancement, and MR cholangiography. Nine patients with ampullary carcinoma were examined by MRI at 1.5 T. MR examinations included T1‐weighted spoiled gradient echo, T1‐weighted fat‐suppressed, and immediate postgadolinium spoiled gradient echo images for all patients and MR cholangiography for three patients. The imaging features of ampullary carcinomas, including tumor size and morphology, signal intensity, and enhancement characteristics, were determined. Ampullary carcinomas shown on MR images ranged in size from 1.5 to 5.5 cm. Tumors were low in signal intensity on precontrast T1‐weighted spoiled gradient echo and T1‐weighted fat‐suppressed images relative to normal pancreatic tissue and enhanced less than normal pancreas on immediate postgadolinium spoiled gradient echo images. Tumor conspicuity was greatest on immediate postgadolinium spoiled gradient echo images. MR cholangiography demonstrated high grade obstruction of the common bile duct and mild dilatation of the pancreatic duct at the level of the ampulla with abrupt termination of the ducts in two untreated patients and moderate dilatation of the common bile duct in one patient who had a biliary stent. Ampullary carcinomas can be demonstrated on MR images as small masses arising at the ampulla. Tumors are well defined on immediate postgadolinium spoiled gradient echo images.
MR imaging of pelvic lymph nodes in primary pelvic carcinoma with ultrasmall superparamagnetic iron oxide (combidex): Preliminary observations
Authors: Harisinghani Mukesh G. , Saini Sanjay , Slater Gregory J. , Schnall Mitchell D. , Rifkin Matthew D. 
Published: March 2007

AbstractThe potential of ultrasmall superparamagnetic iron oxide (Combidex)‐enhanced MRI of pelvic lymph nodes in patients with primary pelvic carcinoma is evaluated. Fifteen histologically classified lymph nodes in six patients with known primary pelvic cancer (four prostate; one rectum; one uterus) were evaluated with T2‐weighted fast spin‐echo (FSE) and T2*‐weighted gradient‐echo (GRE) MRI at 1.5T 12 to 48 hours after intravenous administration of Combidex at a dose of 1.7 mg Fe/kg. Quantitative image evaluation was performed by comparing signal intensity of individual nodes on pre‐ and postcontrast images. All patients proceeded to pelvic lymph‐node biopsy or surgical dissection, where six were found to be benign and nine were malignant. Of the 15 lymph nodes, four nodes showed a decrease in signal intensity. Of these, three, in which signal loss was homogenous were benign, and one, in which the signal‐intensity decrease was heterogeneous, was malignant (micrometastases). No signal change was noted in 11 of 15 lymph nodes of which three were benign (inflammatory) and eight were malignant. Combidex is a promising MR contrast agent for evaluating pelvic lymph nodes. Our preliminary observations suggest that the agent is most useful for classifying normal lymph nodes.
Gadolinium‐enhanced MR angiography of visceral arteries in patients with suspected chronic mesenteric ischemia
Authors: Meaney James F. M. , Prince Martin R. , Nostrant Timothy T. , Stanley James C. 
Published: March 2007

AbstractThe purpose of this study was to evaluate accuracy of dynamic gadolinium‐enhanced MR angiography (MRA) of the celiac, superior, and inferior mesenteric arteries in patients with suspected mesenteric ischemia compared with catheter angiography or surgery. Sixty‐five patients with suspected mesenteric ischemia underwent three‐dimensional spoiled gradient‐recalled acquisition in the steady state (GRASS) gadolinium‐enhanced MRA. Correlative studies were performed on 14 patients, catheter angiography alone was performed on 12 patients, and surgery alone was performed on two patients. Six patients had mesenteric ischemia. In all patients, the celiac artery (CA) and superior mesenteric artery (SMA) were seen well enough to evaluate; however, the inferior mesenteric artery (IMA) could be evaluated in only 9 of the 14 patients. MRA showed severe stenosis (>75%) or occlusion of the celiac axis in seven patients, of the SMA in six patients, and of the IMA in four patients. The overall sensitivity and specificity were 100% and 95%, respectively, compared with catheter angiography and surgery. The two errors were caused by overgrading the severity of IMA disease. Three‐dimensional gadolinium‐enhanced MRA can accurately demonstrate the origins of the CA and SMA and is useful in evaluation of patients with suspected mesenteric ischemia.
Contrast‐enhanced magnetic resonance angiography of carotid arterial wall in pigs
Authors: Lin Weili , Abendschein Dana R. , Haacke E. Mark 
Published: March 2007

AbstractThis study was designed to investigate the effects of contrast agents on MR images of balloon‐injured carotid arteries containing atherosclerotic‐like lesions. We have evaluated an intravascular contrast agent, MS‐325 (METASYN INC., Cambridge, MA) and an extra‐vascular contrast agent, Optimark, (Mallinckrodt Medical Inc., St. Louis, MO) on MR angiograms obtained 4 weeks after balloon hyperinflation‐induced injury of the left common carotid artery in 12 hypercholesterolemic minipigs. High in‐plane resolution (.8 × .4 mm2), thin slice (1 mm) time‐of‐flight gradient echo sequences were used to acquire the MR angiographic images. Vascular lumen definition was compared before and after a single bolus intravenous injection of a contrast agent. Digital subtraction angiograms were obtained from all pigs after MR imaging. High grade stenosis developed in 1 of the 12 pigs and five pigs had complete occlusion of the injured vessel. The remaining pigs exhibited essentially no visible stenoses as assessed either by MR angiography or digital subtraction angiography. The vessel walls of the stenosed and occluded vessels were visible after the injection of either intravascular or extravascular contrast agent. Histologic analyses showed well developed neovascularization in the neointima or occlusive thrombosis. We conclude that the observed contrast‐enhanced vessel wall is caused by an increased vascular supply associated with thrombosis and neointimal thickening that leads to an accumulation of contrast agent in the abnormal vessel walls after the injection of the T1‐shortening paramagnetic contrast agent.
Preliminary evaluation of a polyethyleneglycol‐stabilized manganese‐substituted hydroxylapatite as an intravascular contrast agent for MR angiography
Authors: Adzamli Kofi , Dorshow Richard B. , Hynes Michael R. , Li Debiao , Nosco Dennis L. , Adams Max D. 
Published: March 2007

AbstractA blood‐persistent particulate paramagnetic contrast agent has been formulated via size stabilization of manganese‐substituted hydroxylapatite by a polyethylene glycol (PEG) bearing a terminal diphosphonate. At high PEG surface densities (35–40 mol %), particles with mean diameter 8 ± 2 nm were obtained. Relaxivities of autoclaved samples (at 20 MHz proton Lamor frequency) were R1 = 18.7 ± .8 mM−1 sec−1 and R2 = 22.3 ± .7 mM−1 sec−1. The formulation persisted in rabbit blood with a biphasic clearance profile. Halflives (with amplitudes in parenthesis) were 4 ± 1 minutes (55%), and 49 ± 3 minutes (45%), respectively, for the two phases. A dose of 40 μmol Mn/kg body weight enhanced the signal from rabbit vasculature for more than 45 minutes on MR angiograms. Thus, PEG‐modified MnHA particles may find use as T1 agents for MR angiography.
MR angiography with an ultrasmall superparamagnetic iron oxide blood pool agent
Authors: Anzai Yoshimi , Prince Martin R. , Chenevert Thomas L. , Maki Jeffrey H. , London Frank Londy Manette , McLachlan Stuart J. 
Published: March 2007

AbstractThe purpose of the study was to investigate the use of a dextran‐coated ultrasmall superparamagnetic iron oxide (USPIO) as a blood pool contrast agent for thoracic and abdominal MR angiography. Abdominal and thoracic MR angiography was performed in six healthy volunteers using two‐dimensional and three‐dimensional spoiled gradient echo (SPGR) sequences before and after intravenous administration of USPIO. Doses ranged from 1.1 to 2.6 mg Fe/kg. Flip angle was varied from 20 to 60°. Subjective image quality, analysis of signal‐to‐noise ratio (SNR), and blood T1 relaxation times were measured. USPIO significantly lowered the T1 of blood (from 1,210 ms precontrast to 159 ms postcontrast at a dose of 2.6 mg Fe/kg) (P < .01). Image quality on coronal fast three‐dimensional breath‐hold SPGR images of the abdomen increased with increasing dose and was maximum at the highest dose, producing an aortic SNR of 9.6 compared to 1.8 precontrast. Axial two‐dimensional time‐of‐flight (TOF) aortic SNR was reduced significantly from 13 on precontrast to 6 on the postcontrast images at the highest dose (P < .05) due to T2* shortening effects. There was little flip angle dependence on image quality. Due to the T1 shortening effect and long intravascular half‐life, USPIO improved visualization of vascular anatomy using three‐dimensional fast SPGR imaging. The echo time must be minimized to minimize signal loss from T2* shortening effects. The blood pool distribution of USPIO is useful for equilibriumphase MR angiography.
Dynamic 3d‐mr mammography: Is there a benefit of sophisticated evaluation of enhancement curves for clinical routine?
Authors: Müller‐Schimpfle Markus , Ohmenhäuser Katja , Sand Jürgen , Stoll Peter , Claussen Claus D. 
Published: March 2007

AbstractThe purpose of the study was to compare standard analysis with pharmacokinetic analysis of time‐intensity curves in dynamic three‐dimensional (3D) MR mammography (MRM) for their capability of differentiating benign from malignant disease. Dynamic MRM of the whole breast was performed at 1.0 T using an axial fast low‐angle shot (FLASH) 3D sequence. For the standard evaluation, the enhancement of the first minute (E1) and the slope of enhancement from minute 2 to 10 (SE2–10) were calculated. For pharmacokinetic analysis, the amplitude of enhancement (A), distribution time (t21), and elimination time (tel) were computed. Sixty‐two histologically verified lesions were evaluated. The standard evaluation methods yielded a highly significant difference between benign and malignant disease for E1 (P = .0008) and SE2–10 (P = .0001). The pharmacokinetic parameters gained similarly significant P values (A, P = .0014; t21, P = .0024; tel, P = .0001). Both standard and pharmacokinetic analysis concordantly discriminated between benign and malignant lesions in discriminant analysis. Compared with standard analysis, a pharmacokinetic analysis of time‐intensity curves is not beneficial for routine clinical diagnosis.
Low molecular weight lanthanide contrast agents: In vitro studies of mechanisms of action
Authors: Fossheim Sigrid , Sæbø Karen Briley , Fahlvik Anne Kjersti , Rongved Pål , Klaveness Jo 
Published: March 2007

AbstractThe MR contrast properties of a series of structurally dissimilar low molecular weight (LMW) gadolinium (Gd) and dysprosium (Dy) chelates have been investigated under controlled experimental conditions in various in vitro test systems. Relaxation analysis (water, pH = 5.8, 37°C, .47 T) demonstrated the high dipolar relaxation efficacy of the tested Gd chelates. The T1 and T2 relaxivities of both metal chelate series decreased with decreasing hydration number, confirming the strong correlation between metal chelate structure and dipolar relaxivity. Susceptibility‐induced T2 relaxation, commonly known as the susceptibility effect, is modulated primarily by the magnetic susceptibility and compartmentalization of the contrast agent. The influence of these parameters on the susceptibility effect of Dy diethylenetriamine pentaacetic acid bis‐methylamide (DTPA‐BMA) and GdDTPA‐BMA was investigated in two‐compartment in vitro models. In red blood cell suspensions (45% hematocrit, 37°C, .47 T, 2 and 3 mM metal ion concentration), the T2 relaxation efficacy of DyDTPA‐BMA was markedly improved due to susceptibility effects that were shown to depend on compartmentalization. As the relaxation ability of GdDTPA‐BMA was modulated by the dipolar interactions, compartmentalization was not a prerequisite for its T2 relaxation efficacy. In a coaxial glass system with no intercompartmental water exchange, which eliminated the dipolar relaxation mechanism, DyDTPABMA was shown to be the most efficient susceptibility agent because of its higher magnetic susceptibility. The reported one‐ and two‐compartment model studies have demonstrated the different mechanism of action of LMW Gd‐ and Dy‐based contrast agents. Gd chelates are predominantly dipolar relaxation enhancers, whereas Dy chelates are efficient susceptibility agents only in compartmentalized systems.
Magnetically labeled cells can be detected by MR imaging
Authors: Weissleder Ralph , Cheng Hui‐Cheng , Bogdanova Anna , Bogdanov Alexei 
Published: March 2007

AbstractTo determine the feasibility of MR imaging of magnetically labeled cells, different cell lines were labeled with monocrystalline iron oxide (MION) particles. Phantoms containing MION labeled cells were then assembled and imaged by MR at 1.5 T using T1‐weighted and T2‐weighted pulse sequences. MION uptake ranged from 8.5 × 104 to 2.9 × 105 particles/cell for tumor cells (9L and LX1, respectively) to 1.5 × 106 to 4.8 × 108 particles/cell for “professional phagocytes” (J774 and peritoneal macrophages, respectively). On the T1‐weighted images, cell‐internalized MION appeared hyperintense relative to agar and similar to MION in aqueous solution. On T2‐weighted images, signal intensity varied according to concentration of MION within cells. Cell‐internalized MION caused similar MR signal changes of cells as did free MION; however, at a dose that was an order of magnitude lower, depending on the pulse sequence used. The detectability of MION within cells was approximately 2 ng Fe, which corresponded to 105 tumor cells/well or 5 × 103 macrophages/well. We conclude that a variety of cells can be efficiently labeled with MION by simple incubation. Intracellular labeling may be used for MR imaging of in vivo cell tracking.
Magnetization transfer contrast of hepatic lesions in breath‐hold gradient‐echo images of different T1 weighting
Authors: Schick Fritz , Stern Wolfgang , Forster Jürgen , Laniado Michael , Lutz Otto , Claussen Claus D. 
Published: March 2007

AbstractSeventeen patients with hepatic lesions [six metastases from colon, breast, and gallbladder carcinoma; one gallbladder carcinoma; five hepatocellular carcinoma; three focal nodular hyperplasia (FNH); one adenoma; and one cyst] were examined by MR breath‐hold two‐dimensional gradient‐echo imaging to assess the potential of magnetization transfer contrast (MTC) for improved conspicuity and classification. Imaging sequences were applied with and without irradiation of off‐resonant radiofrequency (RF) prepulses, but other parameters were unchanged. Therefore, quantitative assessment of MTC could be performed. In contrast to former examinations of other researchers, no significant difference of MTC was found between malignant liver lesions and benign lesions as FNH or adenoma. MTC might provide differentiation between hemangioma and cysts versus solid tumors, but MTC is not capable of distinguishing benign and malignant types of solid liver tumors. Effects of unchanged MTC prepulses on signal intensity of normal liver tissue and most lesions were more pronounced for nearly proton density‐weighted fast low‐angle shot (FLASH) images than for T1‐weighted FLASH images, obtained by using higher excitation flip angles. Liver‐to‐lesion contrast could not be improved clearly by MTC prepulses. The contrast between liver and lesions in the gradient‐echo breath‐hold images was compared with standard T1‐ and T2‐weighted spin‐echo images. Liver‐to‐lesion contrast in the breath‐hold images was found to be inferior to T2‐weighted spin‐echo images in 14 of 17 cases. Lesion conspicuity in regions near the diaphragm was better in breath‐hold images, because problems with marked breathing motion (as in standard imaging) could be avoided.