bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of H relaxation times of water in human bone marrow by fat‐suppressed turbo spin echo in comparison to MR spectroscopic methods
Authors: Träber Frank , Block Wolfgang , Layer Günter , Bräucker Gitte , Gieseke Jürgen , Kretzer Sonja , Hasan Ibrahim , Schild Hans H. 
Published: March 2007

AbstractRelaxation times of water were measured in human vertebral bodies by a fat‐suppressed dual‐echo turbo spin echo/turbo inversion recovery MRI sequence. Comparison was made with T1 and T2 values obtained by localized 1H‐MR spectroscopy. The accuracy of the results and the diagnostic potential of the fast quantitative MRI technique were evaluated in 20 volunteers, 11 patients with osteoporosis, 6 patients with lymphoma, and 6 patients with bone marrow metastasis. No significant alterations of T1 and T2 relaxation times of water and fat were found in osteoporosis. With both methods, an increase in the T1 values of the water resonance by 16% was observed in lymphomas, which was highly significant (P < .001) in the MRS measurements, and an elevation by the same amount was obtained by the MRI sequence for the metastases (P = .040). A strong reduction of fat fraction was quantified by MRS in the tumorous cases. T2 of the water resonance increased by more than 30% (P < .003) in metastases. Water T2 values obtained by the MRI sequence showed systematic deviations from the MRS results, especially at short echo spacings.
Investigation of MR decay rates in microphantom models of trabecular bone
Authors: Selby Kathy , Majumdar Sharmila , Newitt David C. , Genant Harry K. 
Published: March 2007

AbstractMR measurements of transverse relaxation time, T2*, in trabecular bone may provide both structural and density‐related information for assessment of bone mineral status in osteoporosis. Using submillimeter scale glass phantoms as simplified models of trabecular bone, we have made a quantitative investigation of the dependence of T2* decay on modeled trabecular microstructure and MR image resolution. The experimental MR data are in excellent agreement with predictions from a computer simulation. Decreasing the modeled trabecular bone volume fraction, ζ, decreases the decay rate, as expected. However, if trabecular width and spacing are both increased without changing ζ, the decay rate is unchanged. The measured decay curves closely follow the predicted dependence on trabecular orientation. The decay rates are independent of image resolution, provided that the pixel dimensions are larger than the intertrabecular spacing. For smaller pixel sizes, the decay rate decreases with decreasing pixel size.
An infrared device for monitoring the respiration of small rodents during magnetic resonance imaging
Authors: Lemieux Susan K. , Glover Gary H. 
Published: March 2007

AbstractA device that uses infrared reflectometry for monitoring the respiratory waveform of small rodents during MRI was developed. This system uses a photoplethysmograph coupled to the animal by a light pipe to detect movements as small as 1.0 mm. This device can also be used for monitoring larger animals or for controlling respiratory‐compensated or respiratory‐triggered MRI.
Functional MRI in human somatosensory cortex activated by touching textured surfaces
Authors: Lin Weili , Kuppusamy Karthikeyan , Haacke E. Mark , Burton Harold 
Published: March 2007

AbstractMRI revealed activation foci in human somatosensory cortex during protocols involving stimulation of the fingertips with a textured surface. A 2D T2*‐weighted gradient echo sequence was used to acquire images. The imaging protocol included acquiring images while subjects performed specific tactile stimulation paradigms (activation scans) or rested. Three different paradigms were used to produce functional activation using a textured surface to rub the fingertips of one hand. First, motor sensory activation was produced by rubbing the textured surface held in one hand against the fingertips of the opposite hand only during the activation scans. Second, the hand holding the textured surface moved throughout the experiment but touched the fingertips of the opposite hand only during the activation scans. Third, subjects remained still in the magnet throughout the entire study while an investigator rubbed the textured surface against the subjects' fingertips during the activation scans. Images were postprocessed using a cross‐correlation scheme. The results revealed multiple foci of motor sensory activation near the central sulcus, postcentral sulcus, and prefrontal cortex.
Pancreatic masses with inconclusive findings on spiral CT: Is there a role for MRI?
Authors: Semelka Richard C. , Kelekis Nikolaos L. , Molina Paul L. , Sharp Tonya J. , Calvo Benjamin 
Published: March 2007

AbstractThis prospective study evaluates the ability of MRI using T1‐weighted fat‐suppressed spin‐echo (T1FS) and dynamic gadolinium chelate (Gd) enhanced spoiled‐gradient echo (SGE) to detect the presence of pancreatic tumor in patients in whom spiral CT findings are inconclusive.Sixteen consecutive patients who underwent spiral CT and had findings that were considered inconclusive for pancreatic tumor underwent MR within 2 weeks of CT. Spiral CT and MR images were interpreted in a prospective fashion by separate individual investigators blinded to the results of the other imaging modality. CT was performed on a spiral CT scanner. MRI was performed on a 1.5‐T MR machine. Imaging sequences included T1FS pre‐Gd and post‐Gd and SGE pre‐Gd and immediately post‐Gd. Data were analyzed using receiver operating characteristic (ROC) analysis. Confirmation was obtained by pancreatic biopsy (n = 4), surgical resection (n = 1), and clinical imaging (n = 4) or clinical follow‐up (n = 7).MRI was superior to spiral CT (P = .027) in this selected patient group at detecting or excluding pancreatic tumor by ROC analysis, with areas under the curve of .982 and .764, respectively, which was significant (P = .041). The greatest advantage of MRI was in patients in whom spiral CT demonstrated enlargement of the pancreatic head without clear definition of tumor, which was significant (P = .033). In 10 patients with this CT appearance, MRI demonstrated a high confidence for presence of tumor in four and a high confidence of absence in six. Association of imaging findings with patient diagnosis was significant for MRI (P = .001) but not significant for CT (P = .148).The results of our study suggest that MRI may add significant diagnostic information in patients in whom spiral CT is inconclusive for the presence of pancreatic tumor. The greatest advantage of MRI was in the evaluation of patients in whom spiral CT findings revealed an indeterminate enlarged pancreatic head.
MR of focal liver lesions: Comparison of breath‐hold and non‐breath‐hold hybrid rare and conventional spin‐echo T2‐weighted pulse sequences
Authors: Carpenter Kenneth D. , Macaulay Shane E. , Schulte Scott J. , Obregon Richard G. , Nelson Rendon C. , Simon Howard E. , Schmiedl Udo P. 
Published: March 2007

AbstractTo compare liver lesion detection rates, tissue signal and noise data, and qualitative parameters for breathhold (BH) and non‐breath‐hold (NBH) hybrid rapid acquisition with relaxation enhancement (RARE) and conventional spin‐echo (CSE) T2‐weighted (CSE‐T2) MR sequences, 20 patients were imaged using all three sequences. Lesion detection rates were 73.5% for the CSE‐T2 sequence and 81.1% and 88.6% for the BH‐RARE and NBH‐RARE sequences, respectively (P = .027). Mean lesion‐to‐liver signal‐difference‐to‐noise ratio for the NBH‐RARE sequence was 14.0 ± 11.5, significantly greater than 9.8 ± 7.8 obtained for the BH‐RARE sequence (P = .050) and 9.0 ± 6.2 obtained for the CSE‐T2 sequence (P = .015). The NBH‐RARE sequence demonstrated fewer artifacts and greater overall image quality compared to the CSE‐T2 sequence. The NBH‐RARE sequence is a useful alternative to the CSE‐T2 sequence providing a higher mean lesion‐to‐liver signal‐difference‐to‐noise ratio and lesion detection rate and better overall image quality.
Comparison of conventional single echo and multi‐echo sequences with a fast spin‐echo sequence for quantitative T2 mapping: Application to the prostate
Authors: Liney Gary P. , Knowles Adrian J. , Manton David J. , Turnbull Lindsay W. , Blackband Stephen J. , Horsman Anthony 
Published: March 2007

AbstractThe accuracy of water T2 maps generated from a fast spin‐echo (FSE) sequence was compared with data obtained by conventional single and multi‐echo spin‐echo pulse sequences using a commercial gel phantom. Spatially localized stimulated echo acquisition mode (STEAM) proton spectroscopy was also used to confirm the reported water T2 values of the gels contained in the phantom. The FSE sequence was shown to be superior in accuracy to both the single and multi‐echo spin echo sequences and comparable to STEAM, producing results that were within 10% of known values. The effectiveness of the FSE sequence was further demonstrated by generating T2 maps of the normal and diseased prostate in clinically acceptable imaging times, resulting in comparable T2 values to those obtained using STEAM. Accurate quantitative T2 maps can be produced with the FSE sequence.
Comparison of single‐breath‐hold fast spin‐echo sequences with routine non‐breath‐hold techniques: Application to MRI of renal masses
Authors: Melki Philippe S. , Argaud Christophe , Suminski Matt , Hélénon Olivier , Belin Xavier , Millet Patrick , Chrétien Yves , Zannoli Guillermo , Moreau Jean‐François 
Published: March 2007

AbstractIn 24 patients presenting with 55 renal lesions (mean size, 20.8 mm), single‐breath‐hold (SBH) fast spin‐echo (FSE) techniques allowing T1 and T2 images to be produced within 20 and 23 sec, respectively, were compared with routine non‐breath‐hold (NBH) spin‐echo (SE) T1 and NBH‐FSE T2 sequences. Contrast‐to‐noise ratios (CNRs) measured from SBH‐FSE T1 images were an average of 97% higher than their NBH counterparts (P = .0001) and allowed an improved lesion conspicuity in 80% of the cases (P = .0001). For T2 imaging, SBH‐FSE and NBH‐FSE sequences were not statistically different with respect to lesion conspicuity (P = .55) and CNR values (P = .19). This was observed despite a 35% average decrease in CNR of SBH‐FSE compared to NBH‐FSE images. By reducing respiratory motion artifacts while preserving SE‐like image contrast, SBH‐FSE techniques have the potential to replace routine NBH sequences for an optimal diagnosis of renal masses.
MR imaging characterization of postischemic myocardial dysfunction („stunned myocardium”︁): Relationship between functional and perfusion abnormalities
Authors: Szolar Dieter H. , Saeed Maythem , Wendland Michael F. , Sakuma Hajime , Roberts Timothy P. L. , Stiskal Michael A. , Derugin Nikita , Higgins Charles B. 
Published: March 2007

AbstractStunned myocardium has been detected in patients treated successfully with thrombolytic agents. The hypothesis of this study was that fast gradient echo (GRE) imaging could be used to characterize the regional functional and perfusion abnormalities that are indicative of myocardial stunning. This study was designed to monitor and correlate the extent of wall thickness and perfusion abnormalities as determined by fast (segmented k space) cine and contrast enhanced GRE imaging, respectively. Dogs were subjected to left circumflex (LCX) coronary artery occlusion (15 min) followed by 30‐minute reperfusion (n= 8). Perivascular flow probes were used to continuously measure flow in left anterior descending (LAD) and LCX coronary arteries. Short‐axis inversion recovery prepared fast GRE and cine images were acquired at baseline, at occlusion, and at 1, 10, and 30 minutes of reflow. Regional signal intensity and percent systolic wall thickening were determined at 26 equally spaced circumferential positions to compare the extent of functional and perfusion abnormalities. During occlusion and reperfusion, the ischemic region was demonstrated on contrast‐enhanced images as a hypointense and hyperintense region, respectively. During occlusion, the extent of the perfusion defect (32% ± 2% of the circumference of the equatorial slice) correlated closely (r= .74) with the extent of contractile dysfunction (35% ± 2%). After reperfusion, there was transient recovery in the percent wall thickening (26% ± 4% vs 36% ± 4% normal), coinciding with the reactive hyperemic response, but this was followed by a significant decline in wall thickening at 10 minutes (19% ± 4%) and 30 minutes (12% ± 2%). Fast MR imaging may be useful to monitor postischemic myocardial abnormalities after thrombolytic therapy and the response to pharmacologic interventions.
Determination of the optimal imaging parameters of the RODEO pulse sequence by computer simulation
Authors: Miller Ira , Gao Jia‐Hong , Fox Peter T. 
Published: March 2007

AbstractA computer program has been developed for evaluating the NMR signal response of various imaging parameters and its efficiency in fat suppression of the RODEO (ROtating Delivery of Excitation Off‐resonance) pulse sequence. Both spoiled and refocused RODEO pulse sequences have been considered. By numerically solving the Bloch equation modified for a three‐dimensional volume of spins, for realistic RF excitations and Lorentzian distribution of the frequency spectrum for both fat and water, the program permits the imaging contrast and fat suppression of the RODEO pulse sequences to be assessed quantitatively. We have found that excellent fat suppression can be achieved by choosing appropriate imaging parameters. Imaging contrast for different tissues can be enhanced by using longer repetition time (TR) in the spoiled scheme. The complex pattern of the NMR signal response and imaging contrast has been observed in the refocused scheme.
Adaptive blood pool segmentation in three‐dimensions: Application to MR cardiac evaluation
Authors: v. Kaushikkar Shantanu , Li Debiao , Haacke E. Mark , Dávila‐Román Victor G. 
Published: March 2007

AbstractMRI is an established method of imaging the cardiac blood pool in four dimensions and evaluating global cardiac function. However, segmentation of the cardiac blood pool from the myocardial wall continues to be a time‐consuming task and is operator dependent. This has hampered the widespread use of cardiac MRI in evaluating global cardiac function. We propose the use of an adaptive threshold‐based, three‐dimensional region‐growing technique to segment the cardiac blood pool from the myocardium and to compute left ventricular blood volumes. It uses a unique double segmentation approach incorporating information from the myocardium to help better detect the edges of the blood pool. The adaptive threshold segmentation technique was evaluated on four human subjects by comparing with manual segmentation. The automated segmentation technique is fast and agreed well with manual segmentation. Further, it requires minimal operator input and is robust and user friendly. The conclusion is that adaptive thresholds and a multidimensional region‐growing approach is an appropriate method to segment the left ventricular blood pool.
Reliability and exactness of MRI‐based volumetry: A phantom study
Authors: Luft Andreas R. , Skalej Martin , Welte Dorothea , Kolb Ruppert , Klose Uwe 
Published: March 2007

AbstractThis study investigated the influence of slice thickness. section orientation, contrast, shape, and sequence type on the exactness of MRI‐based volumetry. Ni‐doped agarose gel phantoms (4 to 46 ml) were scanned with a T1‐weighted three‐dimensional Fourier transform (FT) fast low‐angle shot (FLASH) and a multiecho two‐dimensional FT‐Turbo spin‐echo (SE) sequence. After segmentation with a three‐dimensional region‐growing algorithm, the geometric volume was measured considering the partial volume effect. The variability coefficient (Pearson) was .7%. The volumetric error increased with slice thickness, depending on the size and form of the object. Cross sections resulted in smaller error than longitudinal sections (finger‐shaped phantoms, nonisotropic image data). Three‐dimensional FT was superior to two‐dimensional FT imaging. Results of slice thickness and section orientation experiments can be explained by the partial volume effect. Higher errors in two‐dimensional FT imaging were caused by object movements between two interleaved acquisitions. The study shows a considerable influence of the imaging parameters on the exactness, which depends on size and form of the structure of interest.
Comparison of dysprosium DTPA BMA and superparamagnetic iron oxide particles as susceptibility contrast agents for perfusion imaging of regional cerebral ischemia in the rat
Authors: Haraldseth Olav , Jones Richard A. , Müller Tomm B. , Fahlvik Anne K. , Øksendal Audun N. 
Published: March 2007

AbstractThe aim of the study was to compare the first‐passage profiles of dysprosium diethylenetriamine penta‐acetic acid bis(methylamide) (DTPA BMA) and the superparamagnetic iron oxide particles NSR 0430 in regions with severe and moderate cerebral ischemia. In seven rats subjected to middle cerebral artery occlusion, two dynamic MR perfusion imaging series were acquired after intravenous bolus injections of .5 mmol/kg dysprosium DTPA BMA and .06 mmolFe/kg iron oxide particles, respectively. The doses were chosen to obtain similar maximum signal change in normally perfused brain. The first‐passage profiles were compared in a region of interest (ROI) in the core area with severe ischemia and in a ROI in the penumbra area of moderate ischemia. The results were compared both as the calculated mean signal intensity versus time curves for all seven rats and statistically for an estimated mean transit time (MTT) after gamma variate fitting of the calculated concentration versus time curves. The first‐passage profiles for the two contrast agents were similar, both in the core area of severe ischemia and in the penumbra area of moderate ischemia. In this rat stroke model, dysprosium DTPA BMA and the superparamagnetic iron oxide particles NSR 0430 were found to be equally efficacious for the diagnosis of the perfusion deficit, but if safe for human investigations, iron oxide particles would have an advantage as equal susceptibility effect may be achieved with smaller injection volumes.
Atherosclerosis of the carotid artery: Evaluation by magnetic resonance angiography
Authors: Wildy Kathryn S. , Yuan Chun , Tsuruda Jay S. , Ferguson Marina S. , Wen Nuan , Subramaniam Deepa S. , Strandness D. Eugene 
Published: March 2007

AbstractCarotid artery atherosclerotic plaques (APs) can lead to brain ischemia, an event shown to correlate with both the degree of stenosis and the composition of the AP. Currently, accurate estimates of stenosis can be obtained by either x‐ray angiography or three‐dimensional time of‐flight (TOF) magnetic resonance angiography (MRA). Our purpose was to determine whether three‐dimensional TOF MRA images could also provide information on plaque location, morphology, and composition. Seven pre‐endarterectomy patients underwent three‐dimensional TOF MRA. After endarterectomy, plaque histology was evaluated. Three‐dimensional TOF MRA images contained sufficient soft tissue contrast to differentiate the plaques from the surrounding tissues in all cases. Estimation of plaque morphology had 80% correlation with histology. Finally, intraplaque hemorrhage and calcification were depicted as regions of moderately high and very low intensity, respectively. These preliminary results suggest that three‐dimensional TOF MRA may be useful in studying the development and progression of carotid atherosclerosis.
Inversion recovery image reconstruction with multiseed region‐growing spin reversal
Authors: Xiang Qing‐San 
Published: March 2007

AbstractA new algorithm is introduced for inversion recovery (IR) image reconstruction. The original complex image is modeled as a product of three factors: magnitude, polarity, and a smoothly changing phase factor. The simple binary polarity factor is first unified by a region‐growing spin reversal (RGSR) operation, allowing the phase factor to be extracted. Multiplying the complex conjugate of the phase factor with the original complex data yields the desired IR contrast. The RGSR process is repeated with multiple seeds distributed in the field of view (FOV), and the results are added together, enabling disconnected tissues in the FOV to be handled. The extracted phase factor is filtered to reduce noise and artifacts, without losing useful information. The method is fully automatic and has been used practically in a large number of clinical examinations. The algorithm may also be useful for phase correction in simple proton spectroscopic imaging.
Application of reduced‐encoding imaging with generalized‐series reconstruction (RIGR) in dynamic MR imaging
Authors: Chandra Sudeep , Liang Zhi‐Pei , Webb Andrew , Lee Haakil , Morris H. Douglas , Lauterbur Paul C. 
Published: March 2007

AbstractDynamic MRI has proven to be an important tool in studies of transient physiologic changes in animals and humans. High sensitivity and temporal resolution in such measurements are critical for accurate estimation of dynamic information. Fast imaging, often involving expensive hardware, has evolved for use in such cases. We demonstrate herein the possibility of accelerated data acquisition schemes on conventional machines using standard pulse sequences for dynamic studies. This is achieved by combining reduced‐encoded dynamic data (typically 30 to 40 phase encodings) with a priori high‐resolution data via a novel constrained image reconstruction algorithm. Such an approach reduces image acquisition time significantly (by a factor of 3 to 4 in the examples described here) without loss in the accuracy of information.
Image technique optimization in MR imaging of a titanium alloy joint prosthesis
Authors: Törmänen Juhani , Tervonen Osmo , Koivula Antero , Junila Juhani , Suramo Ilkka 
Published: March 2007

AbstractThe purpose of this study was to explore systematically the effect of the imaging parameters changeable by the user in spin‐echo (SE) imaging sequences to minimize image distortion when imaging joint prostheses. A titanium alloy hip joint prosthesis was studied at 1.0 T. The SE imaging parameters were bandwidth/pixel (BW/p), TE, strength of encoding gradients (matrix size), echo train length (ETL), and direction of phase and frequency encoding. The effect of ETL in rapid acquisition relaxation enhanced (RARE) sequences was also evaluated with a turbo‐SE sequence using a different ETL with the same TR and an effective TE. It is concluded that an optimized image quality can be achieved in SE imaging by using a high bandwidth/pixel value (at least 130 Hz/pixel), a high resolution matrix (256–512), sequences with multiple refocusing, and a frequency‐encoding axis parallel to the long axis of the prosthesis. The degree of distortion is reduced with this optimized technique.
Recent technical advances in MR imaging of the abdomen
Authors: Riederer Stephen J. 
Published: March 2007

AbstractMRI of the abdomen has been under development for well over a decade. In the past, considerable work was directed toward identification and suppression of the artifacts caused by motion. However, within the last several years, image quality has further improved, particularly as various fastscan techniques have been adapted for abdominal imaging. The purpose of this work is to review these technical developments. Specific methods include adaptation of the acquisition time to breath‐holding, acquisition over multiple respiratory cycles, adjustment of the contrast of various sequences, and development of more sensitive receiver coils and faster gradient systems. Opportunities for future development are also identified, including improved slice sampling, increased in‐plane spatial resolution, real‐time means for monitoring respiration, and expanded applications. As these technical advances are implemented, it is expected that the overall sensitivity and specificity of abdominal MRI will further improve.