bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated myocardial edge detection on MR images: Accuracy in consecutive subjects
Authors: Fleagle Steven R. , Thedens Daniel R. , Stanford William , Thompson Brad H. , Weston John M. , Patel Pranav P. , Skorton David J.
Published: March 2007

The authors previously demonstrated the feasibility of graph‐searching‐based automated edge detection in cardiac magnetic resonance (MR) imaging. To further assess the clinical utility of this method, unselected images from 11 consecutive subjects undergoing clinically indicated (except for one healthy volunteer) short‐axis spin‐echo MR imaging were analyzed. A total of 142 images from the 11 subjects, encompassing the left ventricle from apex to outflow tract, were analyzed. The computer algorithm correctly identified complete endocardial and epicardial contours in 121 of 142 images (85%). Correlations between observerbraced and computer‐derived epicardial areas for all images were good (r = .71 for epicardium, r = .83 for endocardium); they improved for a subset of higherquality images (r = .82 for epicardium, r = .92 for endocardium). The authors conclude that the current data further support the usefulness of computer digital image processing in geometric analysis of cardiac MR image data.
Differentiation between hemangiomas and cysts of the liver with nonenhanced MR imaging: Efficacy of T2 values at 1.5 T
Authors: Li Wei , Nissenbaum Michael A. , Stehling Michael K. , Goldmann Alexander , Edelman Robert R.
Published: March 2007

The authors studied the utility of non‐contrast‐agent‐enhanced magnetic resonance (MR) imaging for differentiating cysts and cavernous hemangiomas of the liver. Nineteen patients with hemangiomas (51 lesions) and 16 with cysts (30 lesions) were studied with a 1.5‐T MR imager. T2 values were calculated with the two‐point method to evaluate the efficacy of T2 values in the differentiation between hemangiomas and cysts of the liver. For lesions larger than 1 cm, the mean T2 value of cysts (306 msec ± 156) was significantly longer than that of hemangiomas (113 msec ± 15) (P < .0001); there was no overlap of the ranges for T2 values of hemangiomas and cysts. All cysts larger than 1 cm could be differentiated from hemangiomas by using a threshold T2 value of 140 msec. This study suggests that calculated T2 values permit differentiation between hemangiomas and cysts larger than 1 cm at 1.5 T.
Gadolinium phosphonates as MR imaging contrast agents: Physiologic effects in rabbit hearts
Authors: Adzamli I. Kofi , Weinstein Howard , Leppo Jeffrey A.
Published: March 2007

The hemodynamic effects of the diphosphonate terminus of a new infarct‐avid magnetic resonance (MR) imaging agent, gadolinium‐DTPA (diethylenetriamine‐pentaacetic acid) HPDP (1‐hydroxo‐3‐aminopropane‐1,1‐diphosphonate), and HEDP (hydroxyethyl‐1,1‐diphosphonate) (a simple diphosphonate terminus model) have been evaluated at MR imaging doses in both isolated and intact rabbit hearts. Rapid injections of the sodium salt of the diphosphonates reversibly depressed left ventricular developed pressure and its first derivative (dP/df) but did not affect the in vivo heart rate. Hemodynamic depression was prevented by the co‐administration of two equivalents of calcium ion per diphosphonate terminus in the isolated heart and by either slow infusion or co‐administration of one equivalent of calcium ion per diphosphonate terminus in the in vivo heart. Therefore, if these agents are to be used in MR imaging of acute myocardial infarction, appropriate measures should be taken to prevent negative inotropic effects.
Dynamic gadolinium‐enhanced three‐dimensional abdominal MR arteriography
Authors: Prince Martin R. , Yucel E. Kent , Kaufman John A. , Harrison David C. , Geller Stuart C.
Published: March 2007

The abdominal aorta and renal, visceral, and iliac arteries were evaluated in 16 patients with three‐dimensional Fourier transform imaging enhanced with gadopentetate dimeglumine. By imaging dynamically during the arterial phase of a 5‐minute injection (0.2 mmol/kg), highly significant (P < .0001) preferential arterial enhancement (signal‐to‐noise ratio ± standard deviation, 10 ± 0.9), with minimal enhancement of the inferior vena cava (5.1 ± 1.4) or background tissues (fat, 4.3 ± 0.7; muscle, 2.4 ± 0.5), was achieved in every patient. In six patients with angiographic and/or surgical correlation, 10 of 10 stenoses and two of two occlusions were correctly identified. No inplane saturation or pulsatility artifact was identified in any of the 16 patients. In conclusion, dynamic imaging during the injection of gadopentetate dimeglumine is a promising technique for evaluation of the abdominal aorta and branch vessels.
Statistical description of microcirculatory flow as measured with an MR method
Authors: Su Min‐Ying , Nalcioglu Orhan
Published: March 2007

Quantification of microcirculatory flow is important for the functional assessment of biologic systems. The authors describe a method of analyzing the dependence of the magnetic resonance (MR) signal intensity on microcirculatory flow. A gel bead phantom was used to simulate the randomly oriented flow capillaries, and the MR signal intensity of the phantom was studied at different flow velocities by using velocity‐sensitized and ‐compensated spin‐echo pulse sequences. A theoretical model based on the spin‐phase phenomenon is proposed to elucidate the effect of flow on signal intensity. The velocity phase of a spin depends on its path and the corresponding velocity‐encoding gradients. A Monte Carlo simulation was used to generate the path of a spin on the basis of a statistical model for flow through a random capillary network. From the velocity‐phase distribution of a group of spins within a voxel, the signal attenuation due to flow can be calculated. The results of the statistical model and experimental measurements agreed well. Also, T1 and T2 effects in MR flow measurements were investigated. The current study provides a theoretical framework for understanding MR measurements of micro‐circulatory flow.
Magnetization transfer imaging with pulsed off‐resonance saturation: Variation in contrast with saturation duty cycle
Authors: McGowan, III Joseph C. , Schnall Mitchell D. , Leigh John S.
Published: March 2007

Magnetization transfer contrast (MTC) can be generated in magnetic resonance images of water‐containing macromolecular structures. Results obtained with the pulsed off‐resonance saturation technique for achieving MTC are presented, allowing comparison of this technique with others. The magnetization transfer effect is demonstrated in newborn piglet brain and bovine muscle tissue, as well as in human subjects. MTC increases nonlinearly with the duty cycle of the off‐resonance irradiation, approaching a maximum value corresponding to continuous irradiation. However, approximately half of the available contrast can be obtained at a given saturation offset frequency, with 16% irradiation duty cycle. Examples of MTC in various human tissues demonstrate the specificity of this technique at power levels within U.S. Food and Drug Administration guidelines. Plots of MTC versus the irradiation offset frequency demonstrate the effects of magnetization transfer and are compared with the curve generated by a control phantom that does not show magnetization transfer. Magnetization transfer imaging with pulsed off‐resonance saturation is effective and easily implemented and may be useful in the investigation of saturation transfer phenomena in tissue.
Improved T1‐weighted two‐dimensional MP‐GRE imaging of the liver with variable flip angles for shaping the signal evolution
Authors: Epstein Frederick H. , Mugler John P. , Brookeman James R.
Published: March 2007

The recently introduced method of shaping the transient signal evolution in magnetization‐prepared gradient‐echo (MP‐GRE) imaging with variable flip angles has been applied to two‐dimensional (2D) MP‐GRE imaging of the abdomen. The technique was analyzed by using theoretical models and was implemented on a standard 1.5‐T whole‐body imager with a segmented acquisition. Theoretical models predicted that the variable‐flip‐angle 2D MP‐GRE sequence would increase liver‐spleen signal difference–to‐noise ratios by 290%, 110%, and 160% compared with a 2D MP‐GRE sequence with a flip angle of 10° and sequential phase encoding, a 2D MP‐GRE sequence with a flip angle of 30° and centric phase encoding, and the fast low‐angle shot sequence, respectively. Experimental measurements supported the theoretical predictions.
Recurrent biliary cystadenoma: MR imaging appearance
Authors: Stoupis Christophoros , Ros Pablo R. , Dolson David J.
Published: March 2007

The authors report the case of a 37‐year‐old woman with a biliary cystadenoma that mimicked a liver cyst. The magnetic resonance (MR) imaging features of this rare lesion were correlated with the pathologic findings, showing the potential of MR imaging for depicting and aiding in the diagnosis of biliary cystadenoma and its recurrence.
Simpler locally focused tomography in MR imaging
Authors: Hu Xiaoping
Published: March 2007

The author describes a simple technique for performing locally focused tomography with magnetic resonance imaging. In contrast to a previous technique, which utilized wave functions to represent k‐space data, the one described here does not require complicated experimental design and reconstruction procedures and is easy to implement and understand. The technique is verified with an experimental study. Technical details and experimental results are presented.
Angle‐dependent utilization of gradient hardware for oblique MR imaging
Authors: Bernstein Matt A. , Licato Paul E.
Published: March 2007

A straightforward method for calculating maximum gradient amplitudes for the frequency‐encoding, phase‐encoding, and section‐select functions in oblique magnetic resonance (MR) imaging is presented. The calculated amplitude values depend on the prescribed angulation and on which of the three functions are simultaneously active. The derived expressions are optimal in most cases, and when not optimal, they still offer substantial improvement over calculations that do not incorporate angular information. Both matrix‐based and geometric interpretations are presented.
Measurement of skeletal muscle motion in vivo with phase‐contrast MR imaging
Authors: Drace John E. , Pelc Norbert J.
Published: March 2007

The ability to measure skeletal muscle motion with phase‐contrast magnetic resonance (MR) imaging was tested with a motion phantom that simulated muscle activity. Quantitative analytic data on unidimensional, bidirectional skeletal muscle motion measured in vivo was obtained in four healthy volunteers. MR images of the subjectss' forearms were obtained during flexion and extension of the fingers and of the anterior and posterior muscle compartments of the lower leg with various resistances to ankle dorsiflexion and plantar flexion. It was necessary to correct the data for the effects of eddy currents. In vitro evaluation of the technique was done by studying through‐plane sinusoidal motion of solid objects. The largest error was underestimation of the peak excursion of 11.5 mm by 0.09 mm (the root mean square error for the cycle was 0.04 mm) In vivo experiments demonstrated the contraction of muscles in relation to each other. Data acquisition and analysis techniques must be refined, but measuring skeletal muscle motion with phase‐contrast MR imaging should enhance the understanding of bioengineering fundamentals and muscular changes in disease and adaptation.
P‐31 MR spectroscopy of skeletal and cardiac muscle metabolism in patients with systemic sclerosis: A multiple case study
Authors: Doornbos Joost , Luyten Peter R. , Janssen Matthijs , Wasser Martin , De Roos Albert
Published: March 2007

Three‐dimensionally localized proton‐decoupled phosphorus‐31 magnetic resonance (MR) spectroscopy of skeletal and cardiac muscle was performed in six patients with systemic sclerosis. Cardiac (n = 9) and skeletal (n = 6) spectra were also obtained in healthy volunteers. Metabolite ratios and intracellular pH were determined from the spectra of skeletal and cardiac muscle. The phosphocreatine‐to‐adenosine triphosphate ratio was normal for both skeletal and cardiac muscle in patients with systemic sclerosis. The pH values of skeletal muscle were similar in patients and control subjects (7.13 ± 0.02 vs 7.12 ± 0.01, respectively). In skeletal muscle, the inorganic phosphate‐to‐phosphocreatine ratio in patients was increased relative to that of control subjects (0.106 ± 0.014 vs 0.086 ± 0.006, respectively; P =.02). P‐31 MR spectroscopy showed no abnormalities in the myocardium of patients with systemic sclerosis. Assessment of the inorganic phosphate‐to‐phosphocreatine ratio in peripheral skeletal muscle may be helpful for assessing disease activity.
Time‐resolved MR imaging by automatic data segmentation
Authors: Fredrickson Jill O. , Pelc Norbert J.
Published: March 2007

A method for time‐resolved imaging that provides a flexible trade‐off between imaging time and temporal resolution is presented. It is based on a view order selection technique that automatically segments the acquired raw data into appropriate temporal frames. When used with cardiac monitoring and phase‐contrast imaging, data similar to that obtained with a conventional gated phase‐contrast sequence are acquired rapidly. For many applications, the temporal resolution can be reduced enough to permit imaging within a breath‐hold interval, while still allowing accurate time‐averaged flow quantitation. This is a general technique that can be implemented within a variety of pulse sequences and can resolve other motion cycles, including the respiratory cycle.
Phase I clinical evaluation of a new iron oxide MR contrast agent
Authors: McLachlan Stuart J. , Morris Marie R. , Lucas Maria A. , Fisco Ricardo A. , Eakins Michael N. , Fowler Dennis R. , Scheetz R. Bradley , Olukotun Adeoye Y.
Published: March 2007

The safety and magnetic resonance (MR) imaging potential of BMS 180549, a new superparamagnetic iron oxide contrast agent, were evaluated in a phase I, open‐label, placebo‐controlled study involving 41 healthy subjects. No clinically significant postdose changes in physical examination findings, vital signs, or electrocardiogram results were reported for any of the subjects evaluated. No clinically significant changes in clinical laboratory values were noted by the investigators. Fourteen adverse events considered not serious and considered possibly or definitely related to the drug were reported, three of which required minor treatment. Relaxation time measurements in plasma samples showed a strong, dose‐dependent, and persistent decrease in T1 and T2 values. Significant changes in MR signal intensity of the blood pool and wellperfused organs (liver and spleen) were noted on both T1‐ and T2‐weighted images. Changes in signal intensity of cervical lymph nodes were also observed at the higher doses and late postdose imaging times.
Dynamic gadolinium‐enhanced echo‐planar MR imaging of the liver: Effect of pulse sequence and dose on enhancement
Authors: Reimer Peter , Saini Sanjay , Kwong Ken K. , Cohen Mark S. , Weissleder Ralph , Brady Thomas J.
Published: March 2007

To develop guidelines for clinical magnetic resonance imaging of the liver, the authors undertook an animal study to investigate the effect of dose and pulse sequence on liver signal intensity in gadopentetate dimeglumine—enhanced echo‐planar imaging. Serial imaging of the liver was performed in anesthetized rats after intravenous administration of five different doses (0.01, 0.05, 0.1, 0.2, and 0.5 mmol/kg) of contrast agent, with six different pulse sequences. The results show that gadopentetate dimeglumine—enhanced echo‐planar images obtained during the perfusion phase can yield either positive (due to increased T1 relaxation rates) or negative (due to susceptibility‐induced increased T2 relaxation rates) liver enhancement depending on choice of pulse sequence and dose. At the current clinically recommended dose of 0.1 mmol/kg, maximal liver signal enhancement was seen with a T1‐weighted inversion‐recovery sequence, while maximal liver signal diminution was seen with a T2*‐weighted gradient‐echo sequence. The authors conclude that gadopentetate dimeglumine—enhanced echo‐planar imaging can provide T1, T2, and T2* contrast that may be exploited for both lesion detection and lesion characterization.
Enhanced tumor detection in the presence of fatty liver disease: Cell‐specific contrast agents
Authors: Kreft Burkhard P. , Tanimoto Akihiro , Baba Yuji , Zhao Longhai , Finn J. Paul , Stark David D.
Published: March 2007

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 nonfatty liver and outperformed both chemical shift and conventional MR imaging in detecting liver tumors.
Gadoteridol dose dependence in MR imaging of a liver abscess model
Authors: Runge Val M. , Kirsch John E. , Woolfolk Cecil , Brack Mitchell A. , Garneau Robert A.
Published: March 2007

A necrotic liver abscess model was studied with magnetic resonance (MR) imaging at 1.5 T before and after intravenous administration of gadoteridol at doses of 0.1, 0.25, and 0.5 mmol/kg in 24 rabbits. Enhancement characteristics and lesion delineation were assessed with both breath‐hold and non‐breath‐hold imaging techniques. Lesion delineation, as assessed both by signal intensity measurements and evaluations by two image readers blinded to imaging technique, was greatest on high‐dose (0.5 mmol/kg) breath‐hold images. Lesion rim enhancement was seen consistently only on postcontrast images obtained at a dose of 0.5 mmol/kg and progressed with time after injection of contrast material.
Gd‐EOB‐DTPA enhancement pattern of hepatocellular carcinomas in rats: Comparison with Tc‐99m‐IDA uptake
Authors: van Beers Bernard E. , Grandin Cécile , Pauwels Stanislas , Mottet Isabelle , Goudemant Jean‐François , Delos Monique , Demeure Roger , Pringot Jacques
Published: March 2007

The enhancement pattern of chemically induced hepatocellular carcinomas (HCCs) after intravenous administration of the hepatobiliary magnetic resonance (MR) contrast agent gadolinium‐EOB‐DTPA (ethoxybenzyl‐diethylenetriaminepentaacetic acid) was compared with the uptake pattern of technetium‐99m‐labeled iminodiacetic acid (IDA), a hepatobiliary radioactive tracer. The hepatocyte uptake of both the contrast agent and the scintigraphic agent has been shown to be driven by the organic anion transporter. The tumors enhanced less than the liver after Gd‐EOB‐DTPA administration, whereas the Tc‐99m‐IDA uptake of differentiated HCCs exceeded that of the liver at 30 minutes and 3 hours after administration. The enhancement pattern of a differentiated HCC with Gd‐EOB‐DTPA does not mirror that seen with Tc‐99m‐IDA.
Effect of varying the molecular weight of the MR contrast agent Gd‐DTPA‐polylysine on blood pharmacokinetics and enhancement patterns
Authors: Vexler Vladimir S. , Clément Olivier , Schmitt‐Willich Heribert , Brasch Robert C.
Published: March 2007

The effects of varying the molecular weight of gadolinium‐DTPA (diethylenetriaminepentaacetic acid)—polylysine, a macromolecular magnetic resonance (MR) imaging contrast agent, on blood pharmacokinetics and dynamic tissue MR imaging signal enhancement characteristics were studied in normal rats. Blood elimination half‐life, total blood clearance, volume of the central compartment (Vcc) and the steady‐state distribution volume (Vssd) were calculated for four Gd‐DTPA‐polylysine polymers with average molecular weights of 36, 43.9, 139, and 480 kd and compared with corresponding values for Gd‐DTPA (0.57 kd) and Gd‐DTPA‐albumin (92 kd). Blood elimination half‐life increased sevenfold with an increase in molecular weight from 36 to 480 kd. The Vcc values for all polylysine polymers did not differ significantly from the Vcc value for Gd‐DTPA‐albumin but were significantly smaller than the Vcc value for Gd‐DTPA. The Vssd value for Gd‐DTPA did not differ significantly from the Vssd value for the 36‐ and 43.9‐kd polymers but was significantly larger than the Vssd values for the 139‐and 480‐kd polymers and for Gd‐DTPA‐albumin. On T1‐weighted coronal spin‐echo MR images, dynamic signal enhancement profiles in liver and kidney for the 36‐, 43.9‐, and 480‐kd Gd‐DTPA‐polylysine chelates corresponded to the blood pharma‐cokinetic data. Increasing molecular weight of Gd‐DTPA‐polylysine formulations substantially slows blood clearance and produces a prolonged, almost constant tissue signal enhancement for the 60‐minute observation period.
Gadolinium‐enhanced T1‐weighted versus T2‐weighted imaging of scrotal disorders: Is there an indication for MR imaging?
Authors: Müller‐Leisse Christof , Bohndorf Klaus , Stargardt Achim , Sohn Michael , Neuerburg Jörg , Adam Gerd , Wein Berthold , Urhahn Reinhard , Günther Rolf W.
Published: March 2007

To evaluate the use of gadopentetate dimeglumine in magnetic resonance (MR) imaging of scrotal disorders, the clinical, ultrasound, and MR imaging data of 29 patients (age range, 19–75 years) with various intra‐ and extratesticular disorders were retrospectively analyzed. T1‐ and T2‐weighted spin‐echo images (T1‐T2 group) were compared with T1‐weighted spin‐echo images before and after intravenous administration of gadopentetate dimeglumine (T1‐Gd group). A receiver operating characteristic (ROC) analysis of the findings was undertaken. Better contrast between tumor and parenchyma and a clearer demonstration of the tunica albuginea were noted in the T1‐T2 group (although not of diagnostic relevance). ROC analysis revealed no differences between the two imaging groups in the diagnosis of tumor, trauma, hydrocele, or hemorrhage; however, epididymitis was diagnosed more easily with contrast enhancement (0.8834 vs 0.7759, P = .04) and the diagnosis of orchitis was expressed more strongly (0.8221 vs 0.7184, P = .17). Four of the five observers were more confident in making the diagnosis with contrast enhancement. With MR imaging, the diagnosis was correctly suggested in three patients in whom clinical and ultrasound data were inconclusive. Gadolinium‐enhanced MR imaging gives additional information in scrotal disorders and facilitates diagnosis. It may be helpful when findings at physical examination and ultrasound differ and when plain T1‐ and T2‐weighted images are equivocal.
Use of superparamagnetic contrast media to suppress signal from flowing spins: Preliminary experience
Authors: Duerk Jeffrey L. , Hurst Gregory C.
Published: March 2007

The authors describe their preliminary experience with the use of superparamagnetic magnetic resonance (MR) imaging contrast media for suppression of signal from flowing blood. The goal of this work was to determine if a superparamagnetic contrast agent could successfully eliminate blood signal during cardiac‐gated MR imaging, thereby eliminating or reducing flow artifacts associated with the complex and variable hemodynamics within the heart chambers. Imaging and data analysis were performed in 17 dogs subjected to experimental myocardial infarction as part of a parallel project. Six doses (0.2, 1, 2, 3.5, 4, 5, and 10 mg/kg) of AMI‐25, an experimental contrast agent, were used in the study. Spin‐echo imaging was performed immediately before and every 5 minutes (for an average of 25 minutes) after bolus injection of the contrast agent. Variations in the image signal‐to‐noise ratio relative to a baseline (before injection of contrast agent) image were assessed as a function of dose and time. Preliminary results suggest that a considerable reduction in blood flow artifacts and, hence, increases in image signal‐tonoise ratio can be achieved at doses greater than or equal to 3.5 mg/kg, for approximately 20 minutes after injection. Doses equal to or less than 2 mg/kg and images obtained more than 20 minutes after injection (regardless of dose) did not reliably show hemodynamic artifact suppression.
In vivo quantification of the unidirectional influx constant for Gd‐DTPA diffusion across the myocardial capillaries with MR imaging
Authors: Larsson Henrik B. W. , Stubgaard Max , Søndergaard Lars , Henriksen Ole
Published: March 2007

The authors present an in vivo method for measuring the unidirectional influx constant (Ki) for gadolinium diethylenetriaminepentaacetic acid (DTPA) diffusion across the capillary membrane in the human myocardium with magnetic resonance imaging. Ki, is related to the extraction fraction (E) and the perfusion (F) by the equation Ki = E. F. Ki was obtained by using the longitudinal relaxation rate (R1) as a measure of the myocardial concentration of Gd‐DTPA in the mathematical model for transcapillary transport across capillary membranes. Myocardial enhancement after Gd‐DTPA injection was followed by using inversion‐recovery Turbo‐FLASH (fast low‐angle shot) images obtained in real time. The results were comparable to those obtained from studies with positron emission tomography in humans and invasive studies in animals. A method for obtaining the input function nonin‐vasively is also presented. Comparison with direct arterial blood sampling showed that the noninvasive input function may be even more accurate with regard to timing and curve shape than the invasive input function. The procedure may therefore prove useful in clinical studies.
Selective enhancement of experimental rat brain tumors with Gd‐TPPS
Authors: Bockhorst Kurt , Els Thomas , Hoehn‐Berlage Mathias
Published: March 2007

The synthetic metalloporphyrin gadolinium (III)‐tetraphenylporphine sulfonate (TPPS) was successfully used as a contrast agent for in vivo magnetic resonance (MR) imaging of rat brain glioma. After injection of Gd‐TPPS, the signal intensity of experimental rat brain glioma distinctly increased on T1‐weighted MR images, an effect similar to that produced by the clinically applied MR imaging contrast agent gadolinium diethylenetriaminepentaacetic acid (DTPA). In contrast to other contrast agents studied (Gd‐DTPA, manganese [III]‐TPPS), Gd‐TPPS produced hypointensity in glioma on T2‐weighted images. The tumor‐selective accumulation of paramagnetic Gd‐TPPS in glioma shortened T1 by 53%, from 1,315 msec ± 199 to 628 msec ± 106, and T2 by 34%, from 86 msec ± 4 to 57 msec ± 5 (2 days after injection of 0.25 mmol/kg Gd‐TPPS). The relaxation times of normal cortex, striaturn, corpus callosum, and temporal muscle were not significantly affected. As a result, gliomas appeared hyperintense on T1‐weighted images and hypointense on T2‐weighted images. Owing to the strong effect of Gd‐TPPS on the T2 of glioma, normal brain tissue, tumor, and peritumorous edema could be distinguished on T2‐weighted images alone.
Repeat cerebral blood volume assessment with first‐pass MR imaging
Authors: Runge Val M. , Kirsch John E. , Wells John W. , Dunworth John N. , Hilaire Luna , Woolfolk Cecil E.
Published: March 2007

The feasibility of performing multiple first‐pass studies with dynamic, contrast material‐enhanced magnetic resonance (MR) imaging was evaluated in a cat model of acute middle cerebral artery (MCA) ischemia. Two dynamic series of SSFP (steady‐state free precession) images were acquired in each animal (n = 5) with a conventional 1.5‐T imager. The initial first‐pass study was acquired at 60 minutes after MCA occlusion, and the second study at 70 minutes, with each performed during an intravenous bolus injection of a 0.5 mmol/kg dose of gadoteridol. In both first‐pass studies, differentiation of normal and ischemic gray and white matter was highly statistically significant. At a threshold of P<.01, no statistically significant difference in the peak signal intensity between the first and second studies was noted. A difference between the two studies in the recovery to baseline was seen, presumably due to T1 effects. First‐pass MR studies can be repeated within the time frame of a single clinical examination, expanding their utility.
Early identification of sites of embryo implantation in rats by means of gadolinium‐enhanced MR imaging
Authors: Hamilton G. Scot , Kennedy Thomas G. , Karlik Stephen J.
Published: March 2007

To determine if magnetic resonance (MR) imaging techniques can be used to examine sites of embryo implantation in intact rats, pregnant animals were imaged with gadopentetate dimeglumine‐enhanced MR imaging approximately 10 hours after initiation of implantation on day 5 of pregnancy. T1‐weighted, three‐dimensional SPGR (spoiled gradient‐recalled acquisition in the steady state) sequences were used to image the volume of abdomen containing the uterine horns before and after injection of gadopentetate dimeglumine into a femoral venous catheter. While unenhanced images provided little detail in uterine tissue, analysis of the gadolinium‐enhanced abdominal images with interactive vascular imaging allowed easy identification of sites of embryo implantation along both uterine horns in four of four pregnant rats. These punctate patterns of enhancement match those of macroscopic bluing after injection of Evans blue dye. Similar gadolinium‐enhanced MR imaging of nonpregnant rats produced only a slight, generalized enhancement of entire uterine horns. The authors conclude that local increases in extracellular fluid volume, vascular permeability, and blood flow in the uterus may all contribute to the gadolinium enhancement of the implantation sites. They propose that this approach can be used in experimental settings to provide information regarding embryo implantation unaccessible with traditional approaches. In clinical settings, gadolinium‐enhanced MR imaging may be used to examine potential causes of infertility, including luteal phase defects.
MR imaging of crohn disease: Use of perflubron as a gastrointestinal contrast agent
Authors: Anderson Clinton M. , Brown Jeffrey J. , Balfe Dennis M. , Heiken Jay P. , Borrello Joseph A. , Clouse Ray E. , Pilgram Thomas K.
Published: March 2007

This study was undertaken to evaluate the use of perflubron (perfluorooctylbromide) as an oral contrast agent for magnetic resonance (MR) imaging of patients with Crohn disease. MR examinations were performed before and after perflubron administration in 12 patients with documented Crohn disease. Glucagon was administered intramuscularly before the post‐perflubron examinations. Each patient also underwent abdominal computed tomography within 48 hours of MR imaging. The imaging studies were analyzed for effectiveness of bowel marking with oral contrast agent, clarity of bowel wall visualization, and presence of bowel wall thickening and extraluminal manifestations of Crohn disease such as abscess or fistula formation. Analysis of the imaging studies showed effective marking of the bowel with perflubron and improved bowel wall visualization on postcontrast MR images. Detection of bowel wall thickening and extraluminal complications of Crohn disease was not significantly improved on postcontrast MR images. The authors conclude that perflubron administration effectively marked the bowel and increased the clarity of bowel wall visualization but did not significantly increase the detection of abnormalities related to Crohn disease in the study population.
Dynamic contrast‐enhanced MR imaging of the pituitary gland with fast spin‐echo technique
Authors: Davis Wayne L. , Lee James N. , King Brian D. , Harnsberger H. Ric
Published: March 2007

Preliminary work has demonstrated that dynamic contrast material—enhanced magnetic resonance imaging improves the detection sensitivity for pituitary microadenomas. The authors present a new method of obtaining dynamic contrastenhanced pituitary images with a short TR/TE fast spin‐echo technique. This approach allows acquisition of contrast‐enhanced spin‐echo images with high temporal and spatial resolution. The new technique is applied in a small group of patients and control subjects.
Carotid plaque formation and its evaluation with angiography, ultrasound, and MR angiography
Authors: Wasserman Bruce A. , Haacke E. Mark , Li Debiao
Published: March 2007

The accurate assessment of carotid artery disease is an important challenge for magnetic resonance (MR) angiography. Studies indicate that the detection and grading of stenosis and the evaluation of plaque morphology are all important steps in the clinical assessment of atherosclerosis. The prevalence of significant carotid artery stenosis in the elderly population and even in patients with symptoms of carotid artery disease is low; clinical risk seems to correlate more closely with plaque morphology and surface characterization than with the degree of stenosis. This highlights the importance of MR angiography and ultrasound, which can help characterize plaque morphology in addition to showing the degree of stenosis. The authors review the present understanding of plaque formation, comparisons of plaque imaging with conventional angiography, ultrasound, and MR angiography, and recent progress in MR angiography techniques. Several studies, including the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial, are discussed regarding the current objectives of carotid artery imaging. The sensitivity and specificity of plaque detection and morphologic evaluation continue to improve.
Influence of in vivo copper on MR images of the liver in rats
Authors: Nakakoshi Tsunenori , Fujita Nobuyuki , Jong‐Hon Kan , Takeichi Noritoshi , Miyasaka Kazuo
Published: March 2007

To investigate the effects of in vivo copper on magnetic resonance (MR) images, the authors studied Long‐Evans cinnamon rats, which develop hepatitis and hepatocellular carcinoma as a result of abnormal copper metabolism. The livers of the rats were imaged before hepatitis developed; the absence of hepatic disease was confirmed histopathologically. The copper that accumulated in the liver of the rats was thought to exist in the form of divalent ions, which were suspected of reducing the T1 and T2 of neighboring protons. However, the signal intensities of the liver on T1‐ and T2*‐weighted images did not change, suggesting that in vivo copper, even when accumulated abnormally, does not influence the signal intensity of MR images.
MR gradient response modeling to ensure excitation coherence
Authors: Reese Timothy G. , Pearlman Justin D.
Published: March 2007

Gradient system response has a significant effect on the shape and dispersion of complex k‐space trajectories, as used in echo‐planar magnetic resonance imaging and designed excitation. The authors have developed a method that characterizes the gradient response directly by placing k‐space “landmarks” in the raw data. The method produces a clear delineation of the k‐space trajectory, while providing information about related factors such as magnetic field homogeneity and temporal coherence of the radio‐frequency (RF) and gradient waveforms. By using parameters derived from data collected under varying conditions, gradient response is modeled as a linear system consisting of a response delay function with a frequency‐dependent slope. The results allow corrections that can be applied to the RF waveform or to the k‐space trajectory. Application of this correction to designed excitation with the sinusoidal k‐space trajectory is demonstrated and discussed.
Motion artifacts in fast spin‐echo imaging
Authors: Madore Bruno , Henkelman R. Mark
Published: March 2007

The purpose of this work is to obtain a better understanding of motion artifacts in fast spin‐echo imaging, in order to eventually identify efficient ways of suppressing them. To do so, the point spread function of a moving point was calculated for fast spin‐echo imaging, and experimental data were acquired by imaging a moving liquid sphere with a diameter of 1.5 mm. The agreement of the experimental results with the calculated point spread function is shown to be excellent. It was found that motion artifacts in fast spin‐echo imaging arise from the convolution of two distinct band patterns. One of these patterns may dominate the convolution, giving its own spacing to the resulting image. For other acquisition parameters, the convolution results in an intricate pattern that may appear to lack overall structure.
Early detection of regional myocardial ischemia in ex vivo piglet hearts: MR imaging with magnetization transfer
Authors: Haraldseth Olav , Jones Richard A. , Schjøtt Jan , Rinck Peter A. , Jynge Per , Øksendal Audun N.
Published: March 2007

The effects of regional myocardial ischemia and reperfusion on magnetization transfer (MT) contrast were investigated in an ex vivo perfused piglet heart model. The extent of the ischemic area was defined with perfusion magnetic resonance (MR) studies performed with use of extracellular contrast agents. Relative MT contrast was calculated for a total of 106 regions of interest in nine hearts. In the areas defined as being severely ischemic in the perfusion studies, a small but significant increase in the MT contrast of 18% ± 9 (standard deviation) (n = 35) was found as early as 10 minutes after the start of ischemia. This contrast difference was reduced to 11% ± 10 after 2 hours of total occlusion. The contrast between normal and ischemic tissue can be explained in part by the effect of inflowing blood, which leads to changes in both equilibrium magnetization and the apparent T1 of the perfused tissue. However, theoretical estimation suggests that these flow‐related changes would produce a maximal relative change in MT contrast of approximately 4%. The most likely explanation for the rest of the observed changes is alteration in the distribution of cellular water related to the so‐called intracellular edema that is known to be associated with the acute phase of myocardial ischemia.
Silicone‐fat differentiation in the breast: Exploiting the bright‐fat phenomenon in fast spin‐echo MR imaging
Authors: Hiramatsu Hideko , Mulkern Robert V. , Oshio Koichi , Waitzkin Ellen , Williamson Daniel S. , O'Connor Nicholas , Adams Douglass F. , Jolesz Ferenc A.
Published: March 2007

Selective suppression of silicone or fat with chemical shift–selective (CHESS) pulses is difficult because of the small chemical shift difference between the primary lipid signal and the primary silicone signal at 1.5 T. Differentiation of these chemically distinct species is, however, an important clinical task in assessing implant rupture and silicone migration in breast tissue. A method uniquely suited for silicone‐fat differentiation with fast spin‐echo (FSE) sequences is reported. It is based on the dependence of fat signal on echo spacing in FSE imaging and results show that it may provide a clinically robust method for silicone‐fat differentiation in magnetic resonance imaging of the breast.
Unbiased and efficient estimation of bladder volume with MR imaging
Authors: Light Karen , Roberts Neil , Whitehouse Graham H. , Edwards Richard H. T.
Published: March 2007

Almost all methods of measuring residual volume of urine in the bladder of patients undergoing urologic assessment are biased to an unknown extent. The authors describe the application of an unbiased stereologic technique for estimating the volume of bladder urine known as the Cavalieri method. The method requires imaging of a series of systematic (ie, equally spaced) parallel sections through the bladder. Such data can be conveniently obtained with magnetic resonance (MR) imaging. If sampling begins at a position randomly chosen within the distance corresponding to the section interval. bladder volume is estimated without bias as the sum of the areas of the bladder sections on the images multiplied by the section interval. Computer‐aided point‐counting techniques represent an efficient means of obtaining the required section area estimates. Optimum sectioning and point counting densities for estimating bladder volume were established by analyzing detailed data sets obtained in five volunteers. It was shown that if an average of only 20 points were counted in each of only five systematic sections through the bladder, the volume of bladder urine was estimated with a coefficient of error of about 5%. By studying these five volunteers and an additional 13 with MR imaging and the Cavalieri method, the authors showed that the difference between the volume of urine in the bladder before and after micturition is unbiased (ie, shows no systematic difference) with respect to the volume of urine voided by the subjects.
Age‐related changes in proton T1 values of normal human brain
Authors: Steen R. Grant , Gronemeyer Suzanne A. , Taylor June S.
Published: March 2007

To determine whether there were age‐related changes In the brain tissue of 55 healthy adult volunteers (29 men, 26 women; 18‐72 years old) without known brain abnormalities, a standard inversion‐recovery technique was optimized for precise and accurate T1 measurement within the constraints of a 15‐minute examination. Measurements of water proton T1 were obtained in eight brain regions. T1 increased with age in the genu (P < 0.001) (analysis of variance), frontal white matter (P < 0.05), occipital white matter (P < 0.05), putamen (P < 0.001), and thalamus (P << 0.001). A significant decrease in T1 with age was found in cortical gray matter (P < 0.05). Thus, age‐related changes in T1 are present in a healthy population, even if extremes of age are excluded, suggesting that T1 values generally increase with age. However, increases in T1 were also observed in the genu, putamen, and thalamus of a substantial fraction of volunteers less than 35 years old. Aging healthy persons can show subtle, nonsymp‐ tomatic brain changes, suggesting that brain aging is associated with occult processes that can begin at a relatively early age.
Spiral K‐space MR imaging of cortical activation
Authors: Noll Douglas C. , Cohen Jonathan D. , Meyer Craig H. , Schneider Walter
Published: March 2007

Brain function can be mapped with magnetic resonance (MR) imaging sensitized to regional changes in blood oxygenation due to cortical activation. Several MR imaging methods, including conventional imaging and echo‐planar imaging, have been successfully used for this purpose. The authors investigated spiral k‐space MR imaging, implemented with an unmodified 1.5‐T clinical imager, for imaging of cortical activation. A gradient‐echo, spiral k‐space imaging method was used to measure activation in the primary visual cortex (number sequence task), primary motor cortex (fist‐clenching task), and prefrontal cortex (verbal fluency task). Comparison of conventional and spiral k‐space imaging in the visual and motor cortex, in which signal‐to‐noise ratio, voxel size, and imaging time were matched, showed that artifacts were reduced with the spiral k‐space method, while the area and degree of activation were similar. The number of sections that could be imaged in a fixed time interval was increased by a factor of four with this implementation of spiral k‐space imaging compared with conventional imaging.
Differentiation between hemangiomas and hepatocellular carcinomas with the apparent diffusion coefficient calculated from turboflash MR images
Authors: Moteki Takao , Ishizaka Hiroshi , Horikoshi Hiroyuki , Matsumoto Mitsuomi
Published: March 2007

Serial turboFLASH (fast low‐angle shot) images with and without diffusion‐perfusion (DP) gradients were used for the evaluation of and differentiation between hemangiomas and hepatocellular carcinomas (HCCs) of the liver. Twenty‐six patients with 27 hemangiomas, and 19 patients with 21 HCCs were studied. T1‐ and T2‐weighted spin‐echo images, serial turboFLASH images with and without DP gradients (b = 294.8 and 0 sec/mm2, respectively) were obtained, and the apparent diffusion coefficient (ADC) was calculated for all lesions. Hemangiomas were detected as well‐defined areas of decreased signal intensity on turboFLASH images obtained with DP gradients; HCCs showed slight or no obvious decrease in signal intensity on serial turboFLASH images obtained with DP gradients compared with turboFLASH images obtained without DP gradients, while a considerable percentage (76.5%) of nodular HCCs showed an obvious decrease in signal intensity at the margins. Hemangiomas had large ADC values compared with HCCs. Both ADC and T2 values were significantly different between hemangiomas and HCCs (P < 0.01). However, there was no obvious correlation between ADC and T2 values for either hemangiomas or HCCs (r = 0.18 and 0.48, respectively). On the basis of these results, the calculated ADC should be helpful for distinguishing hemangiomas from HCCs, and the ADC values may be useful even when T2 values are not helpful for making the distinction.
Phase‐contrast pulsatility measurements: Preliminary results in normal and arteriosclerotic iliofemoral arteries work in progress
Authors: Krug Barbara , Kugel Harald , Harnischmacher Urs , Heindel Walter , Schmidt Rainer , Krings Friedrich
Published: March 2007

Magnetic resonance (MR) flow measurements were obtained in six healthy volunteers and 30 patients with arteriosclerotic disease with a 1.5‐T imager and a pulse sequence for flow quantification based on flow‐induced phase shifts. The iliac arteries were investigated in eight and the femoral arteries in 28 subjects. A trigger pulse, followed by the acquisition of 30 evenly distributed data sets, was applied every second heartbeat, thus eliminating any acquisition gap in a full heart cycle. For quantitative analysis, flow velocity was plotted as a function of time. Systolic acceleration, postsystolic deceleration, and pulsatility of flow were calculated and compared with stenosis grades determined from recent intraarterial digital subtraction angiograms. The flattening of the temporal flow patterns correlated with local severity of vascular occlusive disease.
MR monitoring of focused ultrasonic surgery of renal cortex: Experimental and simulation studies
Authors: Hynynen Kullervo , Damianou Christakis A. , Colucci Vincent , Unger Evan , Cline Harvey H. , Jolesz Ferenc A.
Published: March 2007

The aim of the study was to test the hypothesis that magnetic resonance (MR) imaging‐guided and ‐monitored noninvasive ultrasonic surgery can be performed in highly perfused tissues from outside the body. A simulation study was performed to evaluate the optimal sonication parameters. An MR‐compatible positioning device was then used to manipulate a focused ultrasound transducer in an MR imager, which was used to sonicate kidneys of five rabbits at various power levels and different durations. Temperature elevation during sonication was monitored with a T1‐ weighted spoiled gradient‐echo sequence. The simulation study demonstrated that a sharply focused transducer and relatively short sonication times (30 seconds or less) are necessary to prevent damage to the overlying skin and muscle tissue, which have a much lower blood perfusion rate than kidney. The experiments showed that the imaging sequence was sensitive enough to show temperature elevation during sonication, thereby Indicating the location of the beam focus. Histologic evaluations showed that kidney necrosis could be consistently induced without damage to overlying skin and muscle. The study demonstrated that highly perfused tissues such as the renal cortex can be coagulated from outside the body with focused ultrasound and that MR imaging can be used to guide and monitor this surgery.