bluuebunny/crossref_metadata_2025_split huggingface dataset:
MR imaging of infradiaphragmatic lymphadenopathy in children and adolescents with Hodgkin disease: Comparison with lymphography and CT
Authors: Hanna Soheil L. , Fletcher Barry D. , Boulden Thomas F. , Hudson Melissa M. , Greenwald Carol A. , Kun Larry E. 
Published: March 2007

AbstractThe ability of short‐inversion‐time inversion recovery (STIR) magnetic resonance imaging to depict infradiaphragmatic lymphadenopathy was evaluated in 25 consecutive patients with newly diagnosed Hodgkin disease. All patients underwent computed tomography (CT) and multiplanar STIR imaging prior to lymphography (LAG). The STIR and CT images were evaluated for paraaortic and parailiac node enlargement. Findings were compared with LAG findings, which showed the architectural pattern of the opacified lymph nodes. In the upper paraaortic region, STIR imaging showed more abnormal nodes than did CT or LAG. In the lower paraaortic and parailiac regions, lymph node enlargement was shown equally well with STIR and LAG, whereas CT showed fewer enlarged lymph nodes. LAG showed paraaortic or parailiac focal tumor infiltration in three patients with normal‐size nodes, and hyperplasia in two patients with enlarged nodes. STIR imaging showed more abnormal infradiaphragmatic nodes than did CT because of improved lymph node conspicuity. STIR imaging may be a useful addition to CT for staging pediatric Hodgkin disease.
Echo‐planar MR imaging of human brain oxygenation changes
Authors: Stehling Michael K. , Schmitt Franz , Ladebeck Ralf 
Published: March 2007

AbstractEcho‐planar magnetic resonance (MR) imaging was used to observe signal intensity changes in the human brain during hypoxia. Increasing arterial blood levels of deoxyhemoglobin (0%–42%) during prolonged apnea were monitored with a pulse oximeter and correlated with gray matter and white matter signal attenuation of 13% and 20%, respectively. The results suggest the possibility of using deoxyhemoglobin boluses as a physiologic, intravascular susceptibility contrast agent for assessment of local cerebral oxygen utilization.
Rapid MR imaging of a vascular challenge to focal ischemia in cat brain
Authors: De Crespigny Alexander J. , Wendland Michael F. , Derugin Nikita , Vexler Zinaida S. , Moseley Michael E. 
Published: March 2007

AbstractDeoxygenated blood was effectively used as a magnetic resonance (MR) susceptibility contrast agent to distinguish perfused and nonperfused (ischemic) regions in a focal ischemia model in cat brain at 2 T. Modulation of cerebral blood oxygenation levels in response to apnea was followed in real time with T2*‐weighted (gradient‐recalled) echo‐planar MR imaging. Signal loss in the T2*‐weighted images occurred only in perfused tissues as blood became globally deoxygenated. These data complemented information from diffusion‐weighted and contrast agent bolus–‐tracking images. In addition, observation of the signal recovery behavior on reventilation in both normal and ischemic brain offered potentially useful information about the state of the cerebral autoregulatory mechanism.
Brodie Abscess: MR imaging appearance in 10 patients
Authors: Marti‐Bonmati Luis , Aparisi Francisco , Poyatos Cecilio , Vilar Jose 
Published: March 2007

AbstractThe magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1‐weighted images and high signal intensity on T2‐weighted and STIR (short‐inversion‐time inversion recovery) images, (b) an inner ring isointense to muscle on T1‐weighted images and with high signal intensity on T2‐weighted and STIR images, (c) an outer ring hypoin‐tense on all images, and (d) a peripheral halo hypointense on T1‐weighted images. In six of eight cases, a soft‐tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1‐weighted images and high signal intensity on T2‐weighted and STIR images. Only the peripheral halo was clearly identified in both cases.
Single‐breath‐hold venous or arterial flow‐suppressed pulmonary vascular MR imaging with phased‐array coils
Authors: Foo Thomas K. F. , Macfall James R. , Dirk Sostman H. , Hayes Cecil E. 
Published: March 2007

AbstractA method for acquiring pulmonary vascular magnetic resonance (MR) images with either venous or arterial flow suppression is described. The proposed method only marginally increases the overall imaging time compared with conventional flow‐suppression techniques. This enables an acquisition to be completed within a single breath hold with some selectivity as to flow direction. Instead of applying a spatially selective presaturation pulse before each radio‐frequency (RF) excitation pulse, the flow presaturation pulse is applied once every 16‐20 RF excitation pulses. To avoid image artifacts and to maintain a steady state, each presaturation pulse interval is followed by a normal imaging segment but with data acquisition turned off. Overall imaging time is increased by two TR intervals for each presaturation segment. For a 256 × 128 matrix acquisition, venous flow presaturation increases overall imaging time by approximately 14 TR intervals, while arterial flow suppression increases imaging time by 10 TR intervals.
Frequency dependence of MR relaxation times I. Paramagnetic ions
Authors: Vymazal Josef , Bulte Jeff W. M. , Frank Joseph A. , Chiro Giovanni Di , Brooks Rodney A. 
Published: March 2007

AbstractT1 and T2 of paramagnetic ions in free and chelated form were measured over the range of clinical magnetic resonance imaging field strengths (0.02‐1.5 T). T1 values agreed with published data; however, to our knowledge, the field dependence of T2 has not been systematically studied before. Mn2+, Cr3+, and Fe3+ all showed T2 reduction at high field strengths, although reduction due to Fe3+ was minimal. This is believed to be due to “contact” interactions, which have been previously noted for manganese. No such T2 reduction was seen in the chelates, except that dysprosium chelate (but not free ion) showed an anomalous decrease in T2 at high field strengths, which may possibly be explained by a dephasing effect caused by the large magnetic moment of Dy3+.
Frequency dependence of MR relaxation times II. Iron oxides
Authors: Bulte Jeff W. M. , Vymazal Josef , Brooks Rodney A. , Pierpaoli Carlo , Frank Joseph A. 
Published: March 2007

AbstractThe frequency dependence of T1 and T2 was measured for homogeneous suspensions of magnetite and iron oxyhydroxide particles in water with various concentrations of gelatin. The transverse relaxivity showed two types of behavior: (a) For magnetite particles, there was a rapid increase in T2 relaxivity with frequency, followed by a saturation plateau, which accorded with the Langevin magnetization function. From these curves, the magnetic moment of the particle domains was estimated to range from 0.8 to 6.3 104 Bohr magnetons, (b) For iron oxyhydroxide (fer‐ritin, ferrihydrite, and akaganeite) particles, T2 relaxivity increased linearly with frequency, the slope of the increase characteristic for each particle. T2 relaxivity generally increased with increasing gelatin concentration, corresponding to the measured decrease in the water diffusion coefficient. For iron oxides, homogeneously distributed either as iatrogenic agents or endogenous biominerals, these findings may aid in the interpretation of in vivo relaxivity and the effect on MR imaging.
Implementation of wavelet‐encoded MR imaging
Authors: Panych Lawrence P. , Jakab Peter D. , Jolesz Ferenc A. 
Published: March 2007

AbstractReconstructions of images from wavelet‐encoded data are shown. The method of MR wavelet encoding in one dimension was proposed previously by Weaver and Healy. The technique relies on selective excitation with wavelet‐shaped profiles generated by special radio‐frequency waveforms. The result of the imaging sequence is a set of inner products of the image with orthogonal functions of the wavelet basis. Inversion of the wavelet data is accomplished with an efficient algorithm with processing times comparable with those of a fast Fourier transform. The experiments show that wavelet encoding by selective excitation of wavelet‐shaped profiles is feasible. Wavelet‐encoded images are compared with phase‐encoded images that have a similar signal‐to‐noise ratio, and there is no discernible degradation in image quality due to the wavelet encoding. Potential benefits of wavelet encoding are briefly discussed.
MR monitoring during cryotherapy in the liver: Predictability of histologic outcome
Authors: Matsumoto Reiko , Selig Abby M. , Colucci Vincent M. , Jolesz Ferenc A. 
Published: March 2007

AbstractFor well‐controlled application of cryotherapy to focal liver lesions, real‐time monitoring is necessary to limit the final necrotic effect in the treated area. In this study, near real‐time magnetic resonance (MR) monitoring images of normal rabbit liver were obtained during the freezing procedure. The MR‐monitored, freezing‐induced lesions were followed with MR images for up to 3 weeks. Corresponding histologic samples were also obtained over the same time period. Our results indicate that MR images obtained during the freezing procedure can adequately depict the area of final necrosis. Furthermore, histologic changes at each stage of lesion development correlated well with MR signal intensities on follow‐up images. With the development of an MR‐compatible cryogen probe, MR imaging may prove to be a robust method for monitoring, controlling, and following up cryotherapy in the liver.
Reduction of ringing and blurring artifacts in fast spin‐echo imaging
Authors: Zhou Xiaohong , Liang Zhi‐Pei , Cofer Gary P. , Beaulieu Chris F. , Suddarth Steve A. , Johnson G. Allan 
Published: March 2007

AbstractA simple method was devised to reduce ringing and blurring artifacts caused by discontinuous T2 weighting of k‐space data in fast spin‐echo magnetic resonance (MR) imaging. The method demodulates the weighting function along the phase‐encoding direction by using multiple T2 values derived from a set of non–phase‐encoded echoes obtained from an extra excitation. The performance of this method was evaluated by computer simulations and experiments, which confirmed its capability of effectively reducing or, in some cases, even completely removing the ringing and blurring artifacts. The results also show that the proposed method produces better results than other artifact reduction methods. The method is particularly useful at high magnetic field strengths (7.1–9.4 T) and with strong gradients (>20 G/cm) used in MR microscopy, in which the apparent T2 values are short for most tissues. The authors expect that the proposed method will find useful applications in various fast spin echo pulse sequences.
Fast spin‐echo imaging of the knee: Factors influencing contrast
Authors: Piraino David W. , Hardy Peter A. , Schils Jean P. , Richmond Bradford J. , Tkach Jean A. , Belhobek George H. 
Published: March 2007

AbstractConventional T2‐weighted spin‐echo magnetic resonance imaging of the knee requires a long TR. Fast spin‐echo (FSE) imaging can improve acquisition efficiency severalfold by collecting multiple lines of k space for each TR. Compromises in resolution, section coverage, and contrast inevitably result. The authors examined the compromises encountered in FSE imaging of the knee and discuss the variations in image contrast and resolution due to choices of sequence parameters. For short TR/TE knee imaging, FSE does not appear to offer any advantages, since the increased collection efficiency for one section reduces the available number of sections, so that the total imaging time for a given number of sections remains constant relative to conventional spin‐echo imaging. For T2‐weighted images, considerable time can be saved and comparable quality images can be obtained. This saved time can be usefully spent on increasing both the resolution of the image and its signal‐to‐noise ratio, while still reducing total acquisition time by a factor of two. The preferred FSE T2‐weighted images were acquired with a TR of 4,500 msec, TE of 120 msec, and eight echoes. The available number of sections is compromised, and the sequence remains sensitive to flow artifacts; however, the FSE sequence appears to be promising for knee imaging.
Uterine contractions: Possible diagnostic pitfall at MR imaging
Authors: Togashi Kaori , Kawakami Satoshi , Kimura Isshu , Asato Reinin , Okumura Ryousuke , Fukuoka Masatsune , Mori Takahide , Konishi Junji 
Published: March 2007

AbstractA total of 206 nongravid patients with various gynecologic problems underwent pelvic magnetic resonance (MR) examinations that included both sagittal T2‐weighted and contrast agent–enhanced T1‐weighted images. MR images were retrospectively reviewed to identify changes in endometrial configuration on serial images obtained during the same MR examination. In 20 MR examinations (all in women of reproductive age), endometrial distortion due to myometrial bulging was noted on T2‐weighted or contrast‐enhanced T1‐weighted images. It was absent on other MR images obtained at different times. Myometrial bulging exhibited low signal intensity in 18 examinations. The finding resembled adenomyosis or leiomyoma on T2‐weighted or contrast‐enhanced T1‐weighted images. These results evidence the presence of transient myometrial bulging and transient low‐intensity myometrium in the nongravid uterus. This phenomenon is thought to represent uterine contraction. Clinicians should be aware of the potential presence of transient low‐signal‐intensity myometrial bulging that could present diagnostic problems in the normal uterus.
MR imaging of disorders of the brachial plexus
Authors: Bilbey James H. , Lamond Rod G. , Mattrey Robert F. 
Published: March 2007

AbstractThe authors evaluated 64 consecutive patients with suspected brachial plexus (BP) abnormalities of diverse cause with magnetic resonance (MR) imaging, using the body coil and a standardized protocol. Of the 43 patients for whom follow‐up was available, 25 were suspected of having neoplastic involvement of the BP, nine had sustained injuries, and nine presented with BP symptoms of uncertain cause. MR imaging was 63% sensitive, 100% specific, and 77% accurate in demonstrating the abnormality in this diverse patient population. When patients with neoplastic and traumatic disorders were considered separately, sensitivity increased to 81%, accuracy to 88%, and specificity remained unchanged. In the patients with a clinical diagnosis of idiopathic or viral plexitis, the MR imaging findings were normal, serving to exclude other structural abnormalities. It is concluded that MR imaging is valuable in the assessment of a wide range of BP disorders.
MR imaging findings after transplant surgery for Parkinson disease
Authors: Rauch Ronald A. , Markham Charles H. , Rand Robert W. , Becker Donald P. , Lufkin Robert B. 
Published: March 2007

AbstractThe authors describe the magnetic resonance (MR) imaging appearance of the head of the right caudate nucleus in patients who have undergone adrenal medullary transplant surgery for Parkinson disease. All four patients examined showed some clinical improvement after surgery. The MR images acquired 4–6 months postoperatively showed no evidence of caudate atrophy. Three of the four patients showed some increase in size of the operated caudate head relative to preoperative studies. Neither cavitation nor high signal intensity on T2‐weighted images was evident within the caudate head. The one patient studied after administration of gadopentetate dimeglumine showed no abnormal enhancement. These images provided a description of the transplant site and also suggested that the clinical improvement seen was not due to simple ablation of caudate tissue or to postoperative inflammation. The increase in size of the caudate head also suggested that some implanted tissue may have remained in these patients at the time the MR images were acquired.
Velocity and flow quantitation in the superior sagittal sinus with ungated and cine (gated) phase‐contrast MR imaging
Authors: Jordan John E. , Pelc Norbert J. , Enzmann Dieter R. 
Published: March 2007

AbstractNormal blood flow and velocity in the superior sagittal sinus were measured in 30 patients. A fast two‐dimensional ungated phase‐contrast (PC) pulse sequence was compared with a peripherally gated cine PC technique for velocity and flow quantitation. The same imaging parameters were used for both methods. Measured values for mean velocity and flow obtained with the two methods were compared by using regression analysis and t testing. For blood flow, the correlation coefficient was 0.976. For velocity measurements, r was 0.950. Mean flow was 285 mL/min ± 19 with the ungated PC method and 281 mL/min ± 19 with the cine PC method. The mean velocities measured with the two methods were 12.94 cm/sec ± 1.1 and 13.59 cm/sec ± 1.1, respectively. There was no significant difference (paired t test) between the methods for mean flow or velocity data. This was true even though flow in the superior sagittal sinus is moderately pulsatile, as shown with the cine PC technique. The ungated PC method provided these data in 13 seconds versus 3.5 minutes for the cine PC method.
Quantitative MR relaxometry study of muscle composition and function in duchenne muscular dystrophy
Authors: Huang Yanmin , Majumdar Sharmila , Genant Harry K. , Chan Wing P. , Sharma Khema R. , Yu Pearl , Mynhier Mark , Miller Robert G. 
Published: March 2007

AbstractMagnetic resonance imaging and maps of T1 and T2 values were used to study muscle composition in Duchenne muscular dystrophy (DMD). The mean T2 of anterior tibial muscle was 27 msec in healthy control subjects and 43 msec with increased fatty infiltration in DMD patients. In stronger DMD patients, the distribution of muscle T2 values was narrow, centered at 27 msec as in the controls, with a nonoverlapping fat peak centered at 49 msec. In weaker DMD patients, the width of the muscle T2 peak increased and the peak shifted toward the fat peak. Mean muscle T1 decreased from 1.7 to 0.6 second with increasing fatty infiltration. These results show that quantitative T1 and T2 maps may be used to assess muscle status and monitor DMD progression.
Spin‐echo and dynamic gadoliniumenhanced flash MR imaging of hepatocellular carcinoma: Correlation with histopathologic findings
Authors: Yamashita Yasuyuki , Fan Zhan Ming , Yamamoto Hiroaki , Matsukawa Tetsuya , Yoshimatsu Shunji , Miyazaki Toshiyuki , Sumi Minako , Harada Mikihiko , Takahashi Mutsumasa 
Published: March 2007

AbstractEvaluation of histologic subtype and degree of differentiation in hepatocellular carcinoma (HCC) is essential because it affects patient prognosis and treatment planning. To evaluate the histologic subtype of HCC with magnetic resonance (MR) imaging, conventional spin‐echo and dynamic studies were correlated with histopathologic and angiographic findings in 72 HCCs. Dynamic MR imaging was performed with the fast low‐angle shot (FLASH) technique after administration of gadopentetate dimeglumine. There was considerable overlap in signal intensity between various tumor grades on both T1‐ and T2‐weighted images. On dynamic MR images, the peak contrast enhancement ratio correlated with tumor grade (well‐differentiated, 29.5 ± 24.7; moderately differentiated, 63.5 ± 24.1; poorly differentiated, 86.9 ± 26.4) or degree of dilatation of the sinusoidlike vascular space between tumor cells. The maximum contrast‐to‐noise ratio in tumor (relative to surrounding liver) was achieved within 60 seconds in 45 HCCs (mostly of the trabecular or pseudoglandular type). Enhancement was slight or minimal in 17 tumors (mostly small, well‐differentiated tumors). In 10 tumors, the degree of enhancement increased with time, with maximum enhancement in the delayed phase (most frequently in scirrhous HCC). These dynamic patterns correlated with angiographic findings. These data indicate that the degree and pattern of enhancement on dynamic MR images reflect tumor differentiation and architecture of HCC.
Distribution of normal and abnormal fluid collections in the glenohumeral joint: Implications for MR arthrography
Authors: Recht Michael P. , Kramer Josef , Petersilge Cheryl A. , Yu Joseph , Pathria Mini , Trudell Debra , Sartoris David J. , Resnick Donald 
Published: March 2007

AbstractAlthough magnetic resonance (MR) images of the glenohumeral joint frequently demonstrate intraarticular fluid, no specific criteria have, to the authors' knowledge, been published that allow accurate assessment of the amount of fluid present. Also, despite the increasing use of MR arthrography of the shoulder, the optimal amount of intra‐articular fluid that should be used with this technique has not been determined. The authors progressively distended the glenohumeral joint in six cadaveric shoulder specimens with a dilute gadopentetate dimeglumine solution and obtained MR images after injection of 2, 5, 10, 15, and 20 mL of the solution. The pattern of fluid distribution was evaluated, and these results were then used to estimate the amount of fluid that was present in the glenohumeral joint on MR images of 20 shoulders obtained in 12 asymptomatic volunteers. In 14 of these shoulders, intraarticular fluid was present; however, in none was more than 2 mL evident. Results of the cadaveric study also indicated that 15 mL of intraarticular fluid appears to be the optimal amount for MR arthrography.
Computer‐assisted identification and quantification of multiple sclerosis lesions in MR imaging volumes in the brain
Authors: Mitchell J. Ross , Karlik Stephen J. , Lee Donald H. , Fenster Aaron 
Published: March 2007

AbstractMagnetic resonance (MR) imaging is the principal imaging technique for the diagnosis of multiple sclerosis (MS). However, quantifying the number and extent of lesions on MR images manually is arduous. The authors have developed a computerized three‐dimensional (3D) quantitative system to assist in the identification and analysis of MS lesions in proton‐density (PD)‐ and T2‐weighted volumes of the head. The system provides intuitive, interactive operations that allow flexible extraction of information from the data. Use of the system to analyze MR examinations of a phantom containing regular “lesions” showed that accurate (average error, <0.21 cm3) and precise (10% or better for lesions > 1 cm3) measurements of objects less than 7 cm3 is possible, and that an estimate of the quantization error predicted the uncertainty in the volume. Analysis of four MR examinations of a chronic‐progressive MS patient conducted over an 18‐month period was performed. A two‐dimensional histogram showing the frequency of voxels with particular PD‐ and T2‐weighted intensities revealed a distinct cluster only in histograms of sections that contained lesions. Measurements and 3D volume rendering of lesions clearly showed changes in lesion shape, position, and size.
Surgical sutures: MR artifacts and sequence dependence
Authors: Haramati Nogah , Penrod Brian , Staron Ronald B. , Barax Charles N. 
Published: March 2007

AbstractArtifact reduction is fundamental to the daily clinical application of magnetic resonance (MR) imaging. Imaging of the postoperative patient may be difficult because of surgically introduced materials that result in artifacts. The authors tested some commonly used types of surgical suture for MR susceptibility artifact with various imaging sequences. Ten different suture types were studied. Suture was immersed in vegetable oil in separate plastic test tubes. The sutures were also studied embedded in meat. All samples were studied with T1‐weighted and T2‐weighted spin‐echo, STIR (short‐inversion‐time inversion‐recovery), and two‐dimensional and three‐dimensional gradient‐echo sequences. Silk suture produced the most artifact.