bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferumoxides and Tc‐99m sulfur colloid: Comparison of the tumor‐to‐liver uptake in focal nodular hyperplasia
Authors: Grandin Cécile B. , Van Beers Bernard E. , Pauwels Stanislas , Demeure Roger , Jamart Jacques , Pringot Jacques
Published: March 2007

The tumor‐to‐liver uptake of two reticuloendothelial agents, namely ferumoxides and technetium‐99m (Tc‐99m) sulfur colloid, was compared in focal nodular hyperplasia (FNH). Twelve patients with FNH who had undergone ferumoxides‐enhanced MR imaging and planar Tc‐99m sulfur colloid scintigraphy within 1 year were included from the study. Fourteen patients with FNH with a diameter larger than 3 cm were selected for the comparison. The tumor‐to‐liver ferumoxides uptake was calculated and the Tc‐99m sulfur colloid uptake was assessed visually. Ferumoxides uptake was observed in all but one patient with FNH (mean tumor‐to‐liver ratio = .36). The six tumors showing normal (n = 5) or increased (n = 1) radiocolloid uptake when compared to the liver accumulated more ferumoxides than the eight tumors showing decreased radiocolloid uptake (P < .01). However, in some tumors, no direct relation was observed between ferumoxides and Tc‐99m sulfur colloid uptake. Our observations suggest that ferumoxides uptake might not exactly mimic Tc‐99m sulfur colloid uptake in FNH.
Contrast‐enhanced MR imaging of the liver: Comparison between Gd‐BOPTA and mangafodipir
Authors: Schima Wolfgang , Petersein Jan , Hahn Peter F. , Harisinghani Mukesh , Halpern Elkan , Saini Sanjay
Published: March 2007

The purpose of the study was to evaluate the MR contrast agents gadolinium benzyloxypropionictetro‐acetate (Gd‐BOPTA) and Mangafodipir for liver enhancement and the lesion‐liver contrast on T1W spin‐echo (SE) and gradient‐recalled‐echo (GRE) images. Fifty‐one patients (three groups of 17 patients each) with known or suspected liver lesions were evaluated with T1W SE (300/12) and GRE (77‐80/2.3‐2.5/80°) images before and after intravenous (IV) Gd‐BOPTA (0.1 or 0.05 mmol/kg) or Mangafodipir (5 μmol/kg) in phase II to III clinical trials. Quantitative analysis by calculating liver signal‐to‐noise ratio (SNR), lesion‐liver contrast‐to‐noise ratio (CNR), and spleen‐liver CNR was performed. Liver SNR and spleen‐liver CNR were always significantly increased postcontrast. SNR was highest after application of 0.1 mmol/kg Gd‐BOPTA (51.3 ± 3.6, P < .05). CNR was highest after Mangafodipir (−22.6 ± 2.7), but this was not significantly different from others (P = .07). Overall, GRE images were superior to SE images for SNR and CNR. Mangafodipir and Gd‐BOPTA (0.1 mmol/kg) provide equal liver enhancement and lesion conspicuity postcontrast. By all criteria, contrast‐enhanced T1‐weighted GRE were comparable to SE images.
MR imaging of the liver: Effect of portal hypertension on hepatic parenchymal enhancement using a gadolinium chelate
Authors: Soyer Philippe , Dufresne Anne‐Charlotte , Somveille Edith , Scherrer Antoine
Published: March 2007

The purpose of this study was to prospectively investigate the extent to which reduced portal blood flow in patients with hepatic cirrhosis and portal hypertension affects hepatic parenchymal enhancement during gadolinium‐chelate‐enhanced dynamic MR imaging. Breath‐hold three‐dimensional (3D) spoiled gradientrecalled echo (GRE) MR imaging technique obtained after intravenous administration of a gadolinium chelate was used to measure hepatic parenchymal enhancement and time to peak enhancement in 20 patients with hepatic cirrhosis and clinical evidence of portal hypertension (group 1) and in 20 control subjects without portal hypertension (group 2) who were matched for age, sex, and body weight. Mean peak hepatic enhancement values ± SD and times to peak enhancement ± SD were determined for both groups of patients. Mean peak enhancement value (±SD) was 78.7% ± 36.2 in group 1 and 91.6% ± 46.2 in group 2 (not significant). However, in the nine patients in group 1 with splenomegaly, mean peak enhancement value was 61.3% ± 14.4, whereas it was 93.0% ± 42.7 in the 11 patients without splenomegaly (P < .05). Mean time to peak enhancement was 84 seconds ± 23 in group 1 and 54.0 sec ± 25.0 in group 2 (P < .01). Our results show that mean peak enhancement value of hepatic parenchyma after intravenous administration of a gadolinium chelate is significantly altered for patients with portal hypertension and splenomegaly. In addition, the time to peak enhancement is delayed significantly when portal hypertension is present. Thus, it is possible that the optimal time for imaging the liver during the portal phase must be tailored to the status of the portal system of the patient.
Evaluation of the hepatocyte‐specific contrast agent gadobenate dimeglumine for MR imaging of acute hepatitis in a rat model
Authors: Marzola Pasquina , Maggioni Fabio , Vicinanza Eleonora , Daprà Massimo , Cavagna Friedrich M.
Published: March 2007

This work was conducted to test the hypothesis that contrast‐enhanced MRI with hepatocyte‐specific contrast agents facilitates quantitation and mapping of diffuse liver diseases such as hepatitis and cirrhosis. Gadobenate dimeglumine (Gd‐BOPTA/Dimeg, Bracco SpA, Milano, Italy) is a new paramagnetic hepatocytespecific contrast agent currently undergoing clinical trials. We have assessed the usefulness of gadobenate dimeglumine for the diagnosis of diffuse liver diseases in a rat model of chemically induced hepatitis. The study was based on the measurements of in vivo liver relaxation times as well as on the acquisition of standard SE images. Acute hepatitis considerably reduced the degree of T1 shortening of liver parenchyma caused by intravenous injection of .25 mmol/kg of gadobenate dimeglumine. Analogously, the enhancement of the MRI signal intensity of the liver of rats with hepatitis observed in T1‐weighted spin‐echo (SE) images was inferior, in terms of both strength and duration, to that recorded in control rats at doses of .25 mmol/kg and .075 mmol/kg of gadobenate dimeglumine. Our results show that gadobenate dimeglumine enhanced MR imaging has the potential for visualization of hepatitis and for assessment of liver function. Our conclusions differ from those previously published on this subject by other authors. The reasons that led to differing conclusions are discussed.
Renal cell cancer: Incidence of hemorrhage on MR images in patients with chronic renal insufficiency
Authors: John Gesine , Semelka Richard C. , Burdeny Derek A. , Kelekis Nikolaos L. , Woosley John T. , Kettritz Ute , Freeman John A.
Published: March 2007

This study describes the occurrence of hemorrhage in renal cancer in patients with chronic renal insufficiency as shown on MR images. Thirteen consecutive patients with chronic renal insufficiency who had his tologically proven renal cancer and underwent MRI at 1.5 T were entered in the study. MR examinations included spoiled gradient echo (SGE) and T1‐weighted fat‐suppressed imaging pre‐ and postgadolinium administration. All renal cancers were well shown on MR images and were most clearly depicted on postgadolinium T1‐weighted fat‐suppressed images. Tumors in 12 of 13 patients had regions of high signal intensity on precontrast T1‐weighted images. Histology demonstrated intratumoral hemorrhage in all 12 of these patients. Four hemorrhagic tumors were largely cystic on imaging studies. One of these cancers altered in appearance from largely cystic with extensive hemorrhage to largely solid with substantial enhancement after a 2.5‐year interval. Renal cancers demonstrated minimal enhancement (11 patients) on early postgadolinium images and were minimally enhanced on delayed images in 10 of 13 tumors. Two renal cancers demonstrated intense enhancement. Renal cancers are well shown on MR images in patients with chronic renal insufficiency. Because of the common occurrence of hemorrhage into renal cancers in patients with renal insufficiency, caution should be exercised when evaluating hemorrhagic cystic lesions in these patients.
Contrast‐enhanced, ultrafast 3d pulmonary MR angiography in a single breath‐hold: Initial assessment of imaging performance
Authors: Steiner Paul , McKinnon Graeme C. , Romanowski Ben , Goehde Susanne C. , Hany Thomas , Debatin Jörg F.
Published: March 2007

An ultrafast three‐dimensional (3D) sequence was developed, enabling the acquisition of 44 contiguous 2.0‐to 2.2‐mm thin sections, during intravenous application of paramagnetic contrast, in a single breath‐hold. To estimate the potential clinical usefulness, images were assessed qualitatively and quantitatively with regard to visibility of main, lobar, segmental, and subsegmental pulmonary arteries. Five volunteers were examined using a 192 × 192 matrix with an imaging time of 23 seconds and five other volunteers with a 160 × 160 matrix (18 seconds). Each volunteer was imaged in apnea and during shallow respiration. The breath‐held 23‐second scans revealed excellent image quality and near complete visualization of central and segmental, as well as 81% of subsegmental, pulmonary arteries. Imaging time can be shortened to 18 seconds with only marginal loss in visualization performance (P < .05). Respiratory motion was found to cause significant worsening of image quality and vessel detectability. To maintain relevance in a clinical setting, imaging time can be minimized at the cost of a reduction in spatial resolution.
Evaluation of the iliac arteries: Comparison of two‐dimensional time of flight magnetic resonance angiography with cardiac compensated fast gradient recalled echo and contrast‐enhanced three‐dimensional time of flight magnetic resonance angiography
Authors: Quinn Stephen F. , Sheley Robert C. , Szumowski Jerzy , Shimakawa Ann
Published: March 2007

We compared dynamic contrast‐enhanced three‐dimensional time of flight (3DTOF) magnetic resonance angiography (MRA) with two‐dimensional time of flight (2DTOF) MRA with cardiac compensated fast gradient recalled echo (C‐MON) and conventional angiography (CA) when it was available. C‐MON re‐orders the normal data acquisition to minimize ghosting artifacts generated by pulsatile flow. The initial phase of the study involved optimization of parameters and comparison C‐MON with no C=MON in eight patients and volunteers. The final phase of the study involved 53 patients who were imaged with contrast‐enhanced 3DTOF MRA and 2DTOF MRA with C‐MON. Thirty of these patients also had CA. In the initial phase, 2DTOF MRA with C‐MON was found to be equal (n = 3) or superior (n = 5) to 2DTOF without C‐MON. In the final phase, the agreement among all imaging modalities varied from substantial to almost perfect (Cohen's K = .6‐.83). The lowest agreement was using 2DTOF to evaluate the external iliac segments. The among suggested treatments varied from substantial to almost perfect for all imaging modalities (Cohen's K = .73–93). The diagnostic efficacies of 2DTOF with C‐MON and contrast‐enhanced 3DTOF were high overall, with the lowest value being a specificity of 63% for one reader in the evaluation of an external iliac segment using 2DTOF. In summary, 2DTOF with C‐MON helped to eliminate artifacts due to pulsatility in the iliac arterial segments. In our experience, both dynamic constrast‐enhanced 3DTOF MRA and 2DTOF MRA with C‐MON performed well in the evaluation of the iliac arteries. Both studies have high interobserver agreement and high diagnostic efficacy. Contrast‐enhanced 3DTOF MRA should be reserved for situations in which the iliac vessels are extremely tortuous or occluded or the external iliac segments are poorly seen.
Regional cerebral blood volume measured by dynamic susceptibility contrast MR imaging in alzheimer's disease: A principal components analysis
Authors: Maas Luis C. , Harris Gordon J. , Satlin Andrew , English Camper D. , Lewis Robert F. , Renshaw Perry F.
Published: March 2007

Dynamic susceptibility contrast (DSC) MRI is an alternative to positron emission tomography (PET) and single photon emission computed tomography (SPECT) for the evaluation of cerebral hemodynamics in patients with Alzheimer's disease. DSC MRI allows the construction of high resolution images of cerebral blood volume (CBV) without the use of radionuclides or ionizing radiation. In this study, DSC MRI data were collected from 16 patients with probable Alzheimer's disease and 16 age‐matched control subjects. Characteristic patterns of regional CBV variation were found using principal component analysis. Three such patterns were identified: a global variation pattern, an anterior‐to‐posterior CBV gradient, and a temporoparietal pattern. Group differences in the principal component scores associated with the global and temporoparietal patterns (P = .08 and P = .007, respectively) suggest that these deficits reflect characteristic CBV abnormalities in Alzheimer's disease. Using only these two scores, the Alzheimer's disease group was classified with a sensitivity of 81% and a specificity of 88%. Additionally, disease severity, as measured by the Mini‐Mental State Examination (MMSE), was correlated significantly with the third principal component score (Pearson's r = .50, P = .05).
Effect of oxygen inhalation on relaxation times in various tissues
Authors: Tadamura Eiji , Hatabu Hiroto , Li Wei , Prasad Pottumarthi V. , Edelman Robert R.
Published: March 2007

The effect of the oxygen inhalation on relaxation times was evaluated in various tissues, including the myocardium, liver, spleen, skeletal muscle, subcutaneous fat, bone marrow, and arterial blood, with a [1H]MR system. Statistically significant decrease of T1 relaxation times was observed in the myocardium, spleen, and arterial blood after inhalation of 100% oxygen, whereas no significant change was observed in liver, skeletal muscle, subcutaneous fat, or bone marrow. The T2 relaxation time of these tissues did not differ significantly between before and after inhalation of the oxygen. These results indicate that [1H]MRI can be used to evaluate changes with oxygen inhalation and that the effect of the oxygen inhalation on T1 relaxation time is different among various tissues.
Preliminary experience with the application of Gadolinium‐DTPA before MR imaging‐guided laser‐induced interstitial thermotherapy of brain tumors
Authors: Kahn Thomas , Harth Thorsten , Bettag Martin , Ulrich Birgit Schwabe Frank , Schwarzmaier Hans‐Joachim , Modder Ulrich
Published: March 2007

The purpose of this study was to investigate the potential value of i.v. gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA) applied before MRI‐guided laser‐induced interstitial thermotherapy (LITT) of brain tumors without original enhancement, especially in defining total lesion size during therapy. MRI‐guided LITT was performed on two patients with astrocytoma WHO II. For both patients, Gd‐DTPA was administered intravenously after a first irradiation period and LITT was continued after pulling back the light guide to coagulate the upper parts of the tumor. In both patients, the whole irreversible damaged zone of the second irradiation period after Gd‐DTPA showed an intense increase of signal intensity. The spatial expansion correlated with the diameter of an enhancing rim after Gd‐DTPA on follow‐up studies. Our preliminary results indicate that the application of Gd‐DTPA before MRI‐guided LITT may be of value in defining exactly the size of the irreversible damaged zone during therapy in nonenhancing brain tumors.
Dual dynamic contrast‐enhanced MR imaging
Authors: Miyati Tosiaki , Banno Tatsuo , Mase Mitsuhito , Kasai Harumasa , Shundo Hideo , Imazawa Masayoshi , Ohba Satoru
Published: March 2007

A method was devised for obtaining dynamic contrast‐enhanced T1‐weighted and relaxation rate (ΔR2*) images simultaneously to evaluate regional hemodyn‐amics of the brain tumors. On a 1.5‐T MR system, dual dynamic contrast‐enhanced images were obtained using a gradient echo (dual echo fast field echo) pulse sequence with the keyhole technique to improve temporal and spatial resolution during a rapid bolus injection of gadopentetate dimeglumine. The dynamic T1 contrast images were obtained from the first echo; moreover.

∫ ΔR2*dt values were calculated from the first and the second echo images. The dynamic T1 contrast images provided information about characteristic enhancement pattern (vascularization and disruption of bloodbrain barrier), and the f ΔR2*dt values provided a map of regional blood pool in tumor site, peritumoral edema, and other surrounding regions of the brain. The ability to obtain dynamic contrast‐enhanced T1 contrast and ΔR2* imaging at the same time allows optimization of the advantages of each and thereby more information about the microvascular circulation of the brain lesions.
Initial experience with dynamic MR imaging in evaluation of normal bone marrow versus malignant bone marrow infiltrations in humans
Authors: Bollow Matthias , Knauf Wolfgang , Korfel Agnieszka , Taupitz Matthias , Schilling Andreas , Wolf Karl‐Jürgen , Hamm Bernd
Published: March 2007

The purpose of this study was (a) evaluation of dynamic contrast‐enhanced MR imaging of normal bone marrow versus malignant bone marrow infiltrations in patients with proven B‐cell‐type chronic lymphocytic leukemia (B‐CLL) and (b) correlation with the clinical stage according to Binet (stages A, B, C) and response to therapy. Bone marrow imaging of the lumbar spine, pelvis, and proximal femurs was performed at 1.5 T in 45 patients without known malignancy and in 30 patients with B‐CLL. The differences between opposed‐phase and in‐phase dynamic gradient‐echo sequences before and up to 10 minutes after intravenous application of .1 mmol/kg body weight of gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA) were evaluated in normal bone marrow. The contrast‐enhancement patterns of normal and malignant bone marrow were compared using the opposed‐phase dynamic gradient‐echo sequence. Ten of the patients with bone marrow infiltrations (Binet stage C) additionally underwent MR imaging follow‐up during therapy. Opposed‐phase gradient echo sequences demonstrated a signal decrease of normal bone marrow, and in‐phase gradient echo sequences demonstrated a signal increase of normal bone marrow after administration of Gd‐DTPA. The dynamic signal intensity time courses differed significantly (P < .05) between Binet stages B and C and controls as well as among the three Binet stages of B‐CLL. In the 10 patients followed during therapy, MR imaging sensitively demonstrated response (n = 6), nonresponse (n = 2), or relapse after initial response (n = 2). In out‐of‐phase imaging, both normal bone marrow and initial bone marrow infiltration in CLL stage Binet A show signal decrease after administration of contrast agent, whereas there is increase in signal intensity in higher‐grade bone marrow infiltration in Binet stage B or C disease. The signal loss of normal bone marrow in out‐of‐phase imaging is a phase effect rather than a T2* effect. The differentiation of initial from higher‐grade bone marrow infiltration on out‐of‐phase images relies solely on a shift in the fat/water ratio.
Phased array breath‐hold versus non‐breath‐hold MR imaging of focal liver lesions: A prospective comparative study
Authors: Yamashita Yasuyuki , Yamamoto Hiroaki , Namimoto Tomohiro , Abe Yasuko , Takahashi Mutsumasa
Published: March 2007

This study was undertaken to determine whether phased array breath‐hold T1‐ and T2‐weighted sequences can replace non‐breath‐hold spin echo (SE) sequences in the imaging of focal liver lesions by comparing overall image quality, liver‐lesion contrast, and artifact. Both breath‐hold and non‐breath‐hold T1‐weighted and T2‐weighted imagings of focal liver lesions were prospectively compared in 120 patients with suspected focal liver lesions imaged at 1.5 T with use of a body phased array multicoil. Breath‐hold images were acquired with T1‐weighted fast low‐angle shot (FLASH) and T2‐weighted turbo spin echo (TSE) sequences, and non‐breath‐hold images were made with conventional T1‐ and T2‐weighted SE sequences. Qualitative image analysis was done by three blinded readers, and quantitative analysis was done. The highest signal‐to‐noise ratios were obtained with breath‐hold T1‐weighted FLASH sequence. The signal‐to‐noise ratios of breath‐hold T2‐weighted TSE sequence were slightly inferior to those of non‐breath‐hold SE sequence. Both T1‐weighted and T2‐weighted breath‐hold sequences had less image artifact. Overall image quality of breath‐hold sequences was better than that of non‐breath‐hold sequences for both T1‐ and T2‐weighted sequences (P < .01). The tissue contrast of T1‐weighted FLASH sequence was superior to that of SE sequence (P < .01). On T2‐weighted imaging, tissue contrast of solid lesions was better on conventional SE sequence than that on breath‐hold TSE sequence (P < .01). Respiratory ghost artifact was less prominent on T1‐weighted FLASH sequence, although this artifact was occasionally seen on breath‐hold T2‐weighted TSE sequence. In a state‐of‐art MR unit with use of a phased array multicoil, conventional T1‐weighted can be replaced by breath‐hold sequences. On T2‐weighted imaging, because solid tumor‐liver contrast on breath‐hold TSE imaging is inferior to that on non‐breath‐hold SE image, breath‐hold imaging may not replace conventional non‐breath‐hold T2‐weighted SE sequence.
Motion artifact in T2‐weighted fast spin‐echo images of the liver: Effect on image contrast and reduction of artifact using respiratory triggering in normal volunteers
Authors: Choe Kyuran A. , Smith Robert C. , Wilkens Ken , Constable R. Todd
Published: March 2007

The purpose of our study was to evaluate the effect of respiratory motion on the image contrast of T2‐weighted fast spin‐echo (FSE) images of the liver as well as the reduction of motion artifact using respiratory triggering of the data acquisition. We imaged the livers of 10 healthy volunteers using a fast spin‐echo T2‐weighted sequence. Images were obtained both without and with patient triggering. Triggered images were acquired in a segmented fashion during multiple sequential breath‐holds using an echo train of 8 or 16, both with and without flow compensation (gradient moment nulling). Ratios of signal difference to noise (SD/N) of the liver and gallbladder as well as the liver and spleen were compared for all sequences. All of the triggered images showed statistically significant improvement of SD/N for the liver and gallbladder as well as for the liver and spleen when compared with the nontriggered images. Triggered images obtained with an echo train length of 8 and, with flow compensation, showed the highest SD/N ratios. In one volunteer whose liver contained multiple small cysts, the triggered images showed improved visualization of individual cysts and identified a larger number of cysts. Respiratory motion causes a significant loss of contrast on T2‐weighted fast spin‐echo images of the liver. This can be reduced by using a segmented data acquisition triggered by the respiratory cycle obtained during sequential breath‐holds.
Three‐dimensional coronary angiography of the perfused rat heart
Authors: Roder Fridtjof , Hiller Karl‐Heinz , Henz Peter , Kienlin Markus V. , Bauer Wolfgang R. , Ertl Georg , Haase Axel
Published: March 2007

The purpose of this work was to visualize the whole three‐dimensional coronary artery tree of the perfused beating rat heart using three‐dimensional MRI. The spatial resolution amounts to 140 μm. Also, vessels having smaller diameters could be detected. Different strategies for the visualization of the three‐dimensional coronary angiograms including maximum intensity projection, data thresholding, and segmentation, were shown. The coronary artery tree was best visualized by hysteresis threshold segmentation and subsequent surface reconstruction.
Phase‐derivative analysis in MR angiography: Reduced Venc dependency and improved vessel wall detection in laminar and disturbed flow
Authors: Hoogeveen Romhild M. , Bakker Chris J. G. , Viergever Max A.
Published: March 2007

A problem of current MRA techniques is the inability to accurately depict the vascular anatomy, particularly in areas of disturbed flow. Various reasons, such as intravoxel phase dispersion, saturation, temporal variations, and maximum intensity projection (MIP) nonlinearity, cause a wrong delineation of vessel boundaries. A phase contrast (PC)‐based postprocessing operation, the phase derivative (PhD), is introduced to detect phase fluctuations indicating flow. Two‐dimensional and three‐dimensional angiographic reconstruction algorithms are presented. Mathematical formulas are derived to predict the effect of sampling to flow profiles and the effect on the PhD of these profiles. Numerical, phantom, and preliminary in vivo experiments demonstrate that PhD images do not suffer from phase wraps and allow a velocity dynamic range extension only limited by a differential phase change. It is also shown that PhD MIPs produce higher signal‐to‐noise ratios than conventional PC angiograms and give a better impression of the anatomy of (stenotic) vessels and of their diameters for both laminar and disturbed flow.
Inadequacy of motion correction algorithms in functional MRI: Role of susceptibility‐induced artifacts
Authors: Wu Dee H. , Lewin Jonathan S. , Duerk Jeffrey L.
Published: March 2007

Functional MR (fMR) has been useful in providing insight into the localization and detection of neural cortical activity. However, patient head motion is inevitable over the course of most fMR experiments. Although methods to align the control and activation fMR images may correct for some of this motional error, they will be incomplete in correcting for those that depend on spatial orientation. MR signal amplitude of structures that lie along air‐tissue interfaces, for example, are sensitive to susceptibility errors introduced by their reorientation with respect to the main magnetic field. This analysis, using phantoms, cadaver brain, and volunteers, has shown that this reorientation between control and activation images can create regions of “false activation” that increase in area with rotation. Anatomic regions that are expected to be most affected by these susceptibility‐induced magnetic field homogeneity variations are those adjacent to bone or air, such as the mesial and inferior temporal lobes and the inferior and anterior frontal lobes. Interpretation of “activation” in these areas on fMR studies must be performed with careful consideration of this important source of error.
Localized echo‐volume imaging methods for functional MRI
Authors: Yang Yihong , Mattay Venkata S. , Weinberger Daniel R. , Frank Joseph A. , Duyn Jeff H.
Published: March 2007

To perform true three‐dimensional activation experiments in the human brain, dedicated localized echo‐volume imaging (L‐EVI) methods were developed. Three‐dimensional acquisition allows generation of activation maps with minimal vascular enhancement related to inflow effects. The rapid acquisition of the L‐EVI (∼100 msec) reduces signal instabilities caused by motion, facilitating the detection of the small intensity changes expected with brain activation. Single‐shot L‐EVI was performed on normal volunteers at 1.5 T, imaging a three‐dimensional predefined volume (240 × 45 × 45 mm3) in the superior portion of the brain with a spatial resolution of 3.75 × 5 × 5 mm3. Increased brain coverage was achieved with a multi‐volume imaging (three‐shot) version, which simultaneously achieved effective suppression of signals from cerebrospinal fluid. In addition, both asymmetric spin‐echo (ASE) and spin‐echo (SE) versions of the technique were used to detect blood oxygenation level dependent (BOLD) signal changes in the motor cortex with a finger‐tapping paradigm. Images obtained by the L‐EVI sequence were qualitatively comparable to standard multislice two‐dimensional echo‐planar images. Both ASE and SE functional MRI (fMRI) experiments showed consistent activation in the contralateral primary sensorimotor cortex. Furthermore, significant differences in location and magnitude of activation was observed between the two methods, confirming theoretical predictions.
Implementation of a reduced field‐of‐view method for dynamic MR imaging using navigator echoes
Authors: Kyriakos Walid E. , Panych Lawrence P. , Zientara Gary P. , Jolesz Ferenc A.
Published: March 2007

A new technique was designed and implemented that increases imaging speed in dynamic imaging in which change is restricted to a fraction of the full field of view (FOV). The technique is an enhancement of a reduced FOV method first reported by Hu and Parrish. This enhancement extends the use of the Hu and Parrish method to cases in which there is cyclic motion throughout the entire FOV that normally would be aliased into the reduced FOV. This method requires the initial acquisition of a number of baseline k‐space data sets to characterize the background physiological motion during imaging. Projection navigator echoes along both the phase‐ and the frequency‐encoded directions are acquired and used to correct for motion outside the reduced FOV. Automatic placement or repositioning of the updated fraction of the FOV using navigators also is investigated. With this method, when using a 32‐echo rapid acquisition with relaxation enhancement (RARE) sequence, single‐shot updates of T2‐weighted, 128 × 128 pixel images are obtained, yielding a fourfold increase in temporal resolution compared to full k‐space update methods.
In vivo comparison of MR phase distribution and 1/T2* with morphologic parameters in the distal radius
Authors: Allein Sophie , Majumdar Sharmila , De Bisschop Elke , Newitt David C. , Luypaert Rob , Eisendrath Henri
Published: March 2007

A new approach based on the calculation of the phase variance in a region of interest on the phase images of a simple gradient echo sequence, was used to assess the properties of trabecular bone in the distal radius. The phase variance reflects the distribution of field inhomogeneities due to the difference in magnetic susceptibility between bone and marrow in a way similar to T2*. However, the phase variance monitors the intervoxular differences, whereas T2* studies the intravoxular inhomogeneities. In this study of the radius of seven volunteers, both techniques were compared with parameters characterizing trabecular bone structure derived from high resolution MR images. Parameters such as the apparent bone area fraction, trabecular number, thickness and spacing, and box‐counting fractal dimension were determined.
Peripheral nerve stimulation in a whole‐body echo‐planar imaging system
Authors: Ehrhardt James C. , Lin Chin‐S , Magnotta Vincent A. , Fisher David J. , Yuh William T. C.
Published: March 2007

Echo‐planar techniques in MRI use a rapidly oscillating frequency‐encoding gradient with the potential to produce peripheral nerve stimulation. To evaluate the incidence, type, and location of stimulation in a commercial whole‐body scanner, we studied two groups: (a) 173 consecutive individuals scanned by echo‐planar imaging for other purposes and (b) seven subjects who were scanned with an extensive set of 36 echo‐planar sequences (with prompting after each scan to report any peripheral nerve stimulation) to test the effects of various parameters. Although only 5% of group A reported symptoms of peripheral nerve stimulation, all in group B experienced some type of stimulation, dependent primarily on direction of the oscillating gradient and location of the body within the gradient coil. Maximum stimulation typically occurred 30 to 40 cm from isocenter in the region of maximum dB/dt. Generally, y gradients produced truncal stimulation, and x gradients produced stimulation in the head. When hands were clasped over the abdomen, a tingling in the hands occasionally was felt. Patients should be instructed to keep their hands apart.
Multi‐echo 31P spectroscopic imaging of ATP: A scan time reduction strategy
Authors: Chao Hui , Bowers John L. , Holtzman David , Mulkern Robert V.
Published: March 2007

Spectroscopic imaging of 31P metabolites and adenosine triphosphate (ATP) in particular with multiple spin echoes may prove useful for reducing data acquisition times. The usual T2 decay processes that degrade multi‐echo spectroscopic imaging methods, however, are further compounded by J‐coupling modulations in the case of ATP. We determine how these modulations affect multi‐echo spectroscopic imaging k‐space data and produce systematic spatial misregistrations of the ATP resonances. The specific J‐coupling modulations of ATP are determined to identify echo‐spacing effects in multi‐echo spectroscopic imaging of ATP and to determine appropriate post‐processing correction schemes to address the spatial misregistration problem. An in vivo demonstration of the technique that offers a threefold reduction in scan time compared to conventional SI methods is provided and compared with the conventional SI approach.
A programmable eddy‐current compensation system for MRI and localized spectroscopy
Authors: Fry Martin E. , Pittard Simon , Summers Ian R. , Vennart William , Goldie Frederick T. D.
Published: March 2007

A programmable preemphasis system has been developed for eddy‐current compensation in gradient sets with or without active screening. Preemphasis parameters are nonvolatile but can be changed rapidly when working with interchangeable gradient sets. The design allows easy retrofit to existing systems. A method for setting the preemphasis is presented, together with specimen results.
Ovarian fibromas and cystadenofibromas: MRI features of the fibrous component
Authors: Outwater Eric K. , Siegelman Evan S. , Talerman Alexander , Dunton Charles
Published: March 2007

Ovarian fibromas and cystadenofibromas are neoplasms that share a similar distinctive tissue component of dense fibrous tissue. We sought to describe the MRI features of these neoplasms and to determine if the fibrous component shows distinctive characteristics. Fourteen patients in whom MR images performed with multicoil and fast‐spin‐echo images and who subsequently underwent surgery for resection of ovarian fibromas or cystadenofibromas were identified from two institutions. Five patients had ovarian fibromas, and nine patients had fourteen cystadenofibromas. 1.5‐T MR studies used T1‐weighted spin echo and multiplanar T2‐weighted fast‐spin‐echo images, with fat saturation gadoliniumenhanced fast multiplanar gradient‐echo images in seven patients. Studies were reviewed for findings of low (≈ skeletal muscle) signal intensity solid components on T2‐weighted images, characteristics of gadolinium enhancement, and associated endometrial findings. Images were obtained ex vivo from three adnexal surgical specimens with an 8‐cm field of view and correlated with histology. All five of the fibromas showed predominantly very low signal intensity, similar to skeletal muscle, on T2‐weighted images. Two of five fibromas were in patients with endometrial polyps and increased amounts of fluid in the pelvis. Thirteen cystadenofibromas were multicystic masses with bands of very low signal intensity ranging from 2 to 20 mm in the wall of the mass, and one was predominantly solid fibrous tissue. Pathologic correlation with specimen images showed that the low signal intensity material was the subepithelial fibrous component of the Cystadenofibromas. Fibrous components of ovarian fibromas and cystadenofibromas are demonstrable by MR as solid components representing fibrous tissue of very low signal intensity on T2‐weighted images.
Delineation of liver necrosis using double contrast‐enhanced MRI
Authors: Dupas Benoǐt , Bach‐Gansmo Tore , Nomballais Marie Françoise , Meflah Kahled
Published: March 2007

The purpose of this study was to demonstrate the potential usefulness of the combination of gadolinium and dysprosium to enhance the difference between normal and necrotic liver tissue. Small regions of acute necrosis were induced by injecting 200–300 μl of 95% alcohol into the liver of 26 rats. MRI was performed 24 hours after necrosis induction, before and immediately after injection of one or both contrast agents. Using a mixed T1/T2‐weighted sequence, the signal intensity (SI) of the normal liver was reduced by 70%, whereas the necrotic regions had more than a 50% increase in SI after double contrast. The region that was enhanced corresponded largely with the region of necrosis as observed postmortem. The lesion size, when identified, was largely underestimated using either of the agents alone, albeit using the common pulse sequences. The double contrast effect of simultaneous administration of gadolinium and dysprosium allows accurate delineation of liver necrosis.
Influence of copper on MRI of hepatocellular carcinoma
Authors: Matsuzaki Kenji , Sano Nobuya , Hashiguchi Norihisa , Yoshida Shusaku , Nishitani Hiromu
Published: March 2007

The purpose of this paper is to clarify whether copper accumulation in hepatocellular carcinoma (HCC) is a cause of high intensity signal pattern on T1‐weighted images (T1‐WI) by comparing the histologically proven copper accumulation with MR images. Forty‐five surgically resected HCCs were analyzed. Distribution patterns of divalent copper by a modified Timm's method on their maximum cut surfaces were compared with signal patterns on corresponding T1‐WI. The degree of copper accumulation in tumor compared with surrounding liver tissue was higher in 6 lesions, equal in 17 lesions, and lower in 22 lesions. High intensity pattern on T1‐WI were observed in 3 of 6 lesions (50%), 10 of 17 lesions (59%), and 10 of 22 lesions (45%). Distribution patterns of copper were not correlated with intensity patterns on T1‐WI. We conclude that the paramagnetic effect of divalent copper accumulation in HCC is insufficient to influence the MRI.
Effects of ami‐25 on liver vessels and tumors on T1‐weighted turbo‐field‐echo images: Implications for tumor characterization
Authors: Van Gansbeke Daniel , Metens Thierry M. , Matos Celso , Nicaise Nicole , Gay France , Raeymaekers Hubert , Struyven Julien
Published: March 2007

This study was devoted to tumor differentiation in liver MR T1‐weighted imaging with superparamagnetic iron oxide (SPIO). Twenty‐one patients with 40 liver lesions were studied at 1.5 T. Before and at least 45 minutes after SPIO administration, turbo‐field‐echo (TFE) T1‐weighted, TFE T1 × T2*‐weighted (MXT), and fat‐suppressed turbo‐spin‐echo T2‐weighted images were acquired. A quantitative analysis was performed blindly. On TFE T1‐weighted images, the signal enhancement was −33% ± 12 for the liver, −24% ± 2 for adenomas and focal nodular hyperplasia, +60% ± 33 for the hemangiomas; metastases and cyst enhancement were not significant. After SPIO on TFE T1‐weighted images, the hemangioma‐to‐liver signal ratio (149% ± 18) was definitely higher than the mean metastasis‐to‐liver signal ratio (90% ± 16). This T1‐related differentiation ability lacked dramatically on TFE MXT images and, in one case, was reduced on post‐SPIO TFE T1‐weighted images by a long imaging delay after SPIO administration (2 hours).
MR multispectral analysis of multiple sclerosis lesions
Authors: Mitchell J. Ross , Jones Craig , Karlik Stephen J. , Kennedy Karen , Lee Donald H. , Rutt Brian , Fenster Aaron
Published: March 2007

Although quantification of the lesion burden from serial MR examinations of patients with multiple sclerosis (MS) is a common technique to assess disease activity in clinical trials, pathologic change may occur within a lesion without a corresponding change in volume. Therefore, measures of lesion volume and composition may improve the sensitivity of detecting disease activity. A new technique has been developed that provides information about the intensity composition of MS lesions in standard spin‐echo MR examinations. The new technique is based on the multispectral “feature space” intensity distributions of the lesions and normal tissues. Analysis of MR examinations of materials with known T1 and T2 times showed that feature space position from spin‐echo examinations is largely determined from proton density (ρ), T2, and the interecho delay. Information about intensity composition was obtained by reducing the multidimensional intensity distribution to one dimension while minimizing the loss of information. This technique was used to analyze eight lesions in standard spin‐echo MR examinations of three patients with MS. Lesion distributions were compared between examinations by first calibrating the examinations based on the intensity distributions of cerebrospinal fluid (CSF), an internal reference tissue. Many of the lesion distributions had a distinctive peak at low intensity, corresponding to normal‐appearing white matter (WM). Within the lesion distributions, increases in high intensity peaks generally were accompanied by reductions in the WM peak. Serial analysis of the lesion distributions revealed some dramatic fluctuations, even when lesion volume remained constant.
Signal‐to‐noise analysis of cerebral blood volume maps from dynamic NMR imaging studies
Authors: Boxerman Jerrold L. , Rosen Bruce R. , Weisskoff Robert M.
Published: March 2007

The use of cerebral blood volume (CBV) maps generated from dynamic MRI studies tracking the bolus passage of paramagnetic contrast agents strongly depends on the signal‐to‐noise ratio (SNR) of the maps. The authors present a semianalytic model for the noise in CBV maps and introduce analytic and Monte Carlo techniques for determining the effect of experimental parameters and processing strategies upon CBV‐SNR. CBV‐SNR increases as more points are used to estimate the baseline signal level. For typical injections, maps made with 10 baseline points have 34% more noise than those made with 50 baseline points. For a given peak percentage signal drop, an optimum TE can be chosen that, in general, is less than the baseline T2. However, because CBV‐SNR is relatively insensitive to TE around this optimum value, choosing TE ≈ T2 does not sacrifice much SNR for typical doses of contrast agent. The TR that maximizes spin‐echo CBV‐SNR satisfies TR/T1 ≈ 1.26, whereas as short a TR as possible should be used to maximize gradient‐echo CBV‐SNR. In general, CBV‐SNR is maximized for a given dose of contrast agent by selecting as short an input bolus duration as possible. For image SNR exceeding 20–30, the Γ‐fitting procedure adds little extra noise compared with simple numeric integration. However, for noisier input images, as can be the case for high resolution echo‐planar images, the covarying parameters of the Γ‐variate fit broaden the distribution of the CBV estimate and thereby decrease CBV‐SNR. The authors compared the analytic noise predicted by their model with that of actual patient data and found that the analytic model accounts for roughly 70% of the measured variability of CBV within white matter regions of interest.
Relative quantification of pulmonary edema with noncontrast‐enhanced MRI
Authors: Caruthers Shelton D. , Paschal Cynthia B. , Pou N. Adrienne , Harris Thomas R.
Published: March 2007

Pulmonary edema is a debilitating effect of acute respiratory distress syndrome. The ability to measure it noninvasively with high sensitivity and in three dimensions could be useful in not only detection but also in assessment and guidance of treatment. To this end, a three‐dimensional MRI pulse sequence to measure the formation of edema was developed and tested. Another sequence was tested to measure blood flow in distal pulmonary arteries. Pulmonary edema was induced in nine dogs via venous injections of oleic acid. Edema was verified by wet‐to‐dry weight ratio (5.30 ± .38) and extravascular lung water at baseline (2.03 ± 1.12 ml/g dry lung weight) versus postinjury (3.00 ± 1.45 ml/g) (P < .005). The signal‐to‐noise ratio within the lungs increased from 5.47 ± 1.00 at baseline to 7.51 ± 1.96 (P < .005), and the time course of edema formation was resolved. Results from MR phase‐contrast blood flow measurements were variable. The authors conclude that the three‐dimensional scan provides a sensitive relative quantification of pulmonary edema formation without the use of contrast agents or ionizing radiation.
Measurement of collateral blood flow in a porcine model of aortic coarctation by velocity‐encoded cine MRI
Authors: Chernoff Daniel M. , Derugin Nikita , Rajasinghe Hiran A. , Hanley Frank L. , Higgins Charles B. , Gooding Charles A.
Published: March 2007

The purpose of this study was to investigate the time course of development of collateral blood flow in an animal model of aortic coarctation. A juxtaductal aortic stenosis (model coarctation) was surgically created in five juvenile pigs. MRI was performed preoperatively, 1 to 2 days postoperatively, and 2 to 10 weeks postoperatively. Aortic blood flow was measured by velocity‐encoded cine MR (VENC‐MR). The percent change in aortic blood flow (ΔBF) from proximal to distal descending thoracic aorta was calculated, and a multiple‐comparison paired t test used to assess changes in ΔBF over time. Invasive flow measurements were obtained in one animal before sacrifice using an ultrasonic probe. ΔBF preoperatively was −2 ± 8% (mean ± SE). ΔBF increased to 32 ± 7% (mean ± SE, P = .022) 2 days postoperatively and 55 ± 19% (P = .032) 2 to 8 weeks postoperatively. Invasive measurements were in qualitative agreement with the VENC‐MR data. VENC‐MR is an accurate noninvasive method of measuring collateral blood flow in aortic coarctation. Recruitment and development of collateral flow pathways occur rapidly in an animal model.
Probing tumor microvascularity by measurement, analysis and display of contrast agent uptake kinetics
Authors: Parker Geoffrey J. M. , Suckling John , Tanner Steven F. , Padhani Anwar R. , Revell Patrick B. , Husband Janet E. , Leach Martin O.
Published: March 2007

This paper describes a measurement protocol for acquiring quantitative dynamic MRI data and novel analysis and display software (Magnetic Resonance Imaging Workbench (MRIW)). Proton density‐weighted and T1‐weighted two‐dimensional gradient echo images are used to quantify tissue contrast agent concentration. The dynamic studies last approximately 7 minutes, with 10‐second temporal resolution. Analyses of signal and concentration changes with time are performed, allowing capillary permeability‐surface area product, tissue leakage space, enhancement onset time, mean enhancement gradient and maximum enhancement level to be mapped as false‐color parametric overlays registered with anatomic images. Quantification of permeability and leakage space provides a method for comparing physiology in patients between visits or for intersite comparisons.
Triangular fibrocartilage and intercarpal ligaments of the wrist: Does MR arthrography improve standard MRI?
Authors: Zanetti Marco , Bräm Jakob , Hodler Juerg
Published: March 2007

The objective of this study was to assess the value of adding MR arthrography to standard MRI for patients with chronic wrist disorders. Thirty consecutive patients (age range, 19–73 years; mean, 36.2 years) were included in the investigation. The images were evaluated blindly and separately by two radiologists with regard to lesions of the scapholunate (SL) and lunotriquetral (LT) ligaments and the triangular fibrocartilage (TFC). Conventional two‐ or three‐compartment arthrography was used as the standard of reference. For TFC lesions, standard MR images had a sensitivity of 92.3% (reader 1) and 84.6% (reader 2) and a specificity of 41.2% (reader 1) and 52.9% (reader 2). For MR arthrography, sensitivity was 84.6% (reader 1) and 84.6% (reader 2) and specificity was 88.2% (reader 1) and 100% (reader 2). For SL ligament tears, standard MRI had a sensitivity of 33.3% (reader 1) and 11.1% (reader 2) and a specificity of 47.6% (reader 1) and 57.1% (reader 2). For MR arthrography, sensitivity was 66.7% (reader 1) and 55.6% (reader 2) and specificity was 52.4% (reader 1) and 81.0% (reader 2). For LT ligament tears, standard MRI had a sensitivity of 28.6% (reader 1) and 35.7% (reader 2) and a specificity of 93.8% (reader 1) and 81.3% (reader 2). For MR arthrography, sensitivity was 35.7% (reader 1) and 23.1% (reader 2) and specificity was 93.8% (reader 1) and 94.1% (reader 2). In conclusion, the diagnostic performance of MRI in suspected lesions of the TFC and the SL and LT ligaments is improved by adding MR arthrography to the standard examination.