bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractTo 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

AbstractGradient 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

AbstractThe 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

AbstractThe 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

AbstractSelective 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

AbstractAlmost 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

AbstractTo 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

AbstractBrain 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

AbstractSerial 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

AbstractMagnetic 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

AbstractThe 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.
Proton MR spectroscopy in quantitative in vivo determination of fat content in human liver steatosis
Authors: Longo Renata , Pollesello Piero , Ricci Claudio , Masutti Flora , Kvam Bjarne J. , Bercich Luisa , Croce Lory S. , Grigolato Piergiovanni , Paoletti Sergio , De Bernard Benedetto , Tiribelli Claudio , Dalla Palma Ludovico 
Published: March 2007

AbstractTo demonstrate that the lipid volume fraction In liver steatosis can be accurately estimated with in vivo hydrogen‐1 magnetic resonance (MR) spectroscopy, the authors developed a calibration procedure based on in vitro MR spectroscopy of lipid extracts from steatotlc liver specimens. The lipid volume fractions determined with the calibration procedure were compared with the results of histomorphometry and with calibrated computed tomographic (CT) data. The volume fraction of fat determined with MR spectroscopy was in good agreement with the CT results, whereas histomorphometry underestimated the amount of hepatic fat. The results indicate that determination of the fat volume fraction in steatotic liver can be achieved noninvasively with MR spectroscopy.
T2‐weighted MR imaging of the chest: Comparison of electrocardiograph‐triggered conventional and turbo spin‐echo and nontriggered turbo spin‐echo sequences
Authors: Haddad John L. , Rofsky Neil M. , Ambrosino Michael M. , Naidich David P. , Weinreb Jeffrey C. 
Published: March 2007

AbstractIn 22 patients with a diverse range of thoracic abnormalities, T2‐weighted magnetic resonance (MR) images of the chest were obtained with electrocardiograph (ECG)‐triggered turbo spin‐echo (TSE), ECG‐triggered conventional spin‐echo (CSE), and nontriggered TSE sequences, and the images were compared. A 5‐point rating scale was used by three radiologists experienced in MR imaging of the chest to Independently evaluate the images for (a) freedom from ghosting, (b) clarity of heart wall and cardiac chambers, (c) clarity of mediastinal structures, (d) conspicuity of abnormalities, and (e) overall image quality. Evaluations were analyzed with statistical methods. For freedom from ghosting, clarity of heart wall and cardiac chambers, clarity of mediastinal structures, and overall image quality, the ECG‐triggered TSE images were rated higher than the TSE images, which. In turn, were rated higher than the ECG‐triggered CSE images at the P=.05 level of significance. No significant differences were seen between the pulse sequences in the conspicuity of abnormalities, although some differences were observed in individual cases. Our results suggest that ECG‐triggered TSE imaging provides improved, time‐efficient T2‐weighted images of the chest.
Oral superparamagnetic contrast agent (ferumoxsil): Tolerance and efficacy in MR imaging of gynecologic diseases
Authors: Haldemann Heusler Regina C. , Wight Edward , Marincek Borut 
Published: March 2007

AbstractThe purpose of this study was to determine the tolerance and the efficacy of the oral contrast agent ferumoxsil in the assessment of gynecologic diseases. Twenty patients underwent MR imaging at 1.5 T. T1‐weighted spin‐echo (SE) and T2‐weighted fast SE images were obtained before and after ingestion of 600900 mL of the Superparamagnetic negative contrast agent ferumoxsil. No side effects were observed. No statistically significant increase in artifact generation was present in the postcontrast images. The efficacy in bowel marking was significant for the small bowel (P = 0.0001) and the cecum (P < 0.01), but not significant in all sequences for the sigmoid. In the postcontrast images, delineation of the uterus, the right‐sided adnexa, the lymph nodes, and the pathologic lesions was significantly better (P < .01), but not all sequences showed an improvement in delineation of the other pelvic organs. After administration of ferumoxsil, the level of confidence in diagnosis was significantly higher (P = .0001), but no change in diagnosis was made from the preto the postcontrast images. We found the oral contrast agent ferumoxsil to be well tolerated and effective in marking the bowel and in delineating the normal organs as well as the pathologic lesions on pelvic MR images.
Selection of MR images for automated segmentation
Authors: McClain Kevin J. , Zhu Yunqiang , Hazle John D. 
Published: March 2007

AbstractMR images show a large range of contrast for various tissues in the body and are ideal for multispectral segmentation. Typically, only two MR images (dualecho series) are used for segmentation: however, other images are often available. We evaluated MR images from 40 patients to determine the optimal type and number of images required for segmentation of tissues associated with brain tumors (normal brain, edema, necrosis. and active tumor). Pattern recognition methods indicated that three MR images from the same slice location were adequate for segmentation. M defined by feature selection and feature extraction measures based on training fields. This result was also confirmed by visually examining segmented images for all 40 patients. The work demonstrates that by using existing imagelrtatistid analysis techniques (feature selection and feature extraction). one can systematically determine the optimal type and number of MR images for tissue segmentation.
First‐pass contrast‐enhanced inversion recovery and driven equilibrium fast gre imaging studies: Detection of acute myocardial ischemia
Authors: Saeed Maythern , Wendland Michael F. , Lauerrna Kirsi , Sakurna Hajirne , Chew Wil , Derugin Nikita , Higgins Charles B. 
Published: March 2007

AbstractThe purpose of this study was (1) to monitor the dynamic effects Of T1 ‐enhancing and magnetic SUSCCPtibility contrast material on normal canine myocardium using inversion recovery (IR)‐ and driven equilibrium @E)‐prepared fast gradient‐recalled echo (GRE) sequences and (2) to determine the relative value of T1‐enhancing and magnetic eusceptibflity contrast material in detecting regions of ischemia in the same animal. Normal dogs (n = 5) and dogs with acute occlusion of the left anterior descending (LAD] coronary artery [n = 11) were studied using a 1.5‐T NIR imager. ECG‐gated fast IR‐prepared GRE images were acquired using TI/TR/TE of 700/7.0/2.9 msec and a flip angle of 7°. Fast DE‐prepared GRE images were obtained using a flip angle of 12° and a DE delay /TR/TE of 60/10.2/4.2 msec. Sequential images were acquired to monitor transit of 0.06 mmol/kg gadodiamide injection and 0.2 and 0.4 mmol/kg sprodiamide injection. On slice‐nonselective IR fast GRE images. gadodiamide caused signiflcant enhancement of the normal myocardium and the left ventricular (LV) chamber blood. In dogs with LAD occlusion, the ischemic region was defined as an area of low signal intensity (SI). On DE‐prepared GRE sequences, administration of sprodiamide resulted in a substantial decrease in signal from normal myocardium and LV chamber blood in normal dogs. In animals subjected to LAD occlusion, this contrast medium produced a transient decrease in SI from normal myocardium [P <.06) and no signiflcant change in SI from ischemic myocardium. IR‐ and DE‐prepared taet GRE imaging can be used to monitor the transit of Tl‐enhancing and magnetic susceptibility contrast material in the heart. respectively. Cardiac image quality was much better when slice‐nonselective IR‐prepared fast GRE sequences were used rather than DE‐prepared fast GRE.
Unsupervised Measurement of Brain Tumor Volume on MR Images
Authors: Velthuizen Robert P. , Clarke Laurence P. , Phuphanich Surasak , Hall Lawrence O. , Bensaid Amine M. , Arrington John A. , Greenberg Harvey M. , Silbiger Martin L. 
Published: March 2007

AbstractWe examined unsupervised methods of segmentation of MR images of the brain for measuring tumor volume in response to treatment. Two clustering methods were used: fuzzy c‐means and a nonfuzzy clustering algorithm. Results were compared with volume segmentations by two supervised methods, k‐nearest neighbors and region growing, and all results were compared with manual labelings. Results of individual segmentations are presented as well as comparisons on the application of the different methods with 10 data sets of patients with brain tumors. Unsupervised segmentation is preferred for measuring tumor volumes in response to treatment, as it eliminates operator dependency and may be adequate for delineation of the target volume in radiation therapy. Some obstacles need to be overcome, in particular regard‐big the detection of anatomically relevant tissue classes. This study shows that these improvements are possible.
Measurement of regional aortic compliance by MR imaging: A study of reproducibility
Authors: Forbat Sandy M. , Mohiaddin Raad H. , Yang Guang Z. , Firmin David N. , Underwood S. Richard 
Published: March 2007

AbstractThe reproducibility of MR imaging for the measurement of aortic compliance was studied in 47 healthy volunteers. Long and short term reproducibility and iatraobserver variability were tested. The method was modified to improve image quality and short term reproducibility and intraobserver variability retested. For comparison, spin echo imaging was compared with cine gradient echo imaging. Initial long term reproducibility showed a mean difference (± SE) of 3% (± 7%) with 95% confidence interval (CI) for limits of agreement of ± 69%. Short term reproducibility (7% ± 6%, 95% CI ±46%) and intraobserver variability (1% ± 2%, 95% CI ± 31%) were better. After modification of the technique and optimization of image quality, both short term reproducibility and intraobserver variability improved (0% ± 3%. 95% CI ± 17% and 5% ± 2%, 95% CI ± 16% respectively). Aortic compliance can be measured using spin echo MR imaging with good reproducibility provided care is taken to obtain good quality Images with high spatial resolution.