bluuebunny/crossref_metadata_2025_split huggingface dataset:
MRI evaluation of thermal ablation of tumors with focused ultrasound
Authors: McDannold Nathan , Hynynen Kullervo , Wolf Delia , Wolf Gerald , Jolesz Ferenc 
Published: March 2007

AbstractMRI was used to target and evaluate the tissue effects of focused ultrasound ablation on tumors implanted in the skeletal muscle of rabbits in vivo. First, MRI was used to localize the tumors and plan the ultrasound therapy. Second, temperature‐sensitive phase‐difference images were acquired to monitor the location of the ultrasound focus and to estimate the effects of temperature rise. After the treatment, the spatial and temporal temperature profiles for defining boundaries of tissue coagulation were calculated. Finally, these boundaries were compared to T2‐weighted and contrast‐enhanced T1‐weighted images obtained immediately after therapy. The results indicate that using MRI for planning and evaluating focused ultrasound surgery is feasible. We showed a linear relationship between applied power and shifts in the proton resonant frequency. Fluctuations in the location of the focus about the target location were on the order of the resolution of the MR images. The temperature rise and lesion size varied significantly. Regions of tissue coagulation calculated from MR data correlated well with post‐therapy imaging.
Invited. On the feasibility of MRI‐guided focused ultrasound for local induction of gene expression
Authors: Madio David P. , van Gelderen Peter , DesPres Daryl , Olson Alan W. , de Zwart Jacco A. , Fawcett Timothy W. , Holbrook Nikki J. , Mandel Myrna , Moonen Chrit T. W. 
Published: March 2007

AbstractGene therapy is a promising approach to the treatment of many forms of disease, including cancer. Of critical concern in its implementation is the ability to control the location, duration, and level of expression of the therapeutic gene. Here, we propose the use of local heat in combination with a heat‐sensitive promoter to help accomplish this. Certain members of the family of heat shock protein (hsp) promoters display a regulation that depends strongly on temperature. We present a study of natural hsp70 induction in rat leg by MRI‐guided focused ultrasound to investigate the hsp70 promoter as a possible candidate for use in control of gene expression with local heat. A temperature increase of 5–8°C in the focal region for 45 minutes led to a differential expression of the hsp70 mRNA between the focal region and the surrounding tissue ranging from a factor of 3 to 67.
MR‐guided placement of a temporary vena cava filter: Technique and feasibility
Authors: Frahm Christian , Gehl Hans‐Björn , Lorch Heike , Zwaan Martin , Drobnitzky Matthias , Laub Gerhard A. , Weiss Hans‐Dieter 
Published: March 2007

AbstractThe purpose of this paper was to investigate the feasibility of MR‐guided insertion of a temporary vena cava filter on an open low‐field imager. In vivo procedures were performed on four anesthetized pigs using a common nonferromagnetic temporary vena cava filter and a special prototype guidewire developed for vascular interventions guided by low‐field MRI. Breath‐hold spoiled gradient‐echo sequences (fast low‐angle shot [FLASH]) with flow compensation were used for position monitoring of the passively visualized intravascular devices. Using the described technique and equipment, all steps of the procedure were feasible in the MR unit. Practicability of the procedure seems to be sufficient for clinical purposes but was inferior compared to the conventional technique of filter placement.
Invited. Temperature monitoring of interstitial thermal tissue coagulation using MR phase images
Authors: Stollberger Rudolf , Ascher Peter W. , Huber Dietrich , Renhart Werner , Radner Herbert , Ebner Franz 
Published: March 2007

AbstractThe temperature‐dependent water proton frequency shift was investigated for temperature monitoring of interstitial thermal coagulation. A procedure for online temperature calculation was developed, and errors due to temperature‐dependent susceptibility were investigated by finite element analysis and reference measurements. The temperature coefficient of magnetic susceptibility and proton chemical shift were determined for brain tissue and other substances. With the proposed procedure, the location of isotherms could be well visualized during laser‐induced interstitial coagulation in vitro and in vivo. Systematic errors caused by magnetic susceptibility changes with temperature depend strongly on the characteristics of the heat source and can exceed susceptibility effects caused by physiologic tissue changes. For the laser applicators discussed here, however, a first order compensation for this effect was found to be satisfactory, because it reduces the absolute error to the range of ± 1°C. The proposed method represents a very promising approach for monitoring of the interstitial thermal coagulation.
Active MR visualization of a vascular guidewire in vivo
Authors: Ladd Mark E. , Zimmermann Gesine G. , Quick Harald H. , Debatin Jörg F. , Boesiger Peter , von Schulthess Gustav K. , McKinnon Graeme C. 
Published: March 2007

AbstractThe purpose of this study was development of an actively visualized .035‐inch vascular guidewire for use in MR‐guided interventions. The guidewire was actively visualized by inclusion of a 6‐cm‐long radiofrequency coil in its tip. A high contrast outline of the distal tip of the guidewire was obtained by acquiring an image with the radiofrequency coil as the receiving antenna. The position of the guidewire relative to the surrounding anatomy was determined by overlaying the guidewire image on a previously acquired road map. The guidewire was evaluated in vivo in the abdominal vessels of a rabbit and swine at 1.5 T. The built‐in radiofrequency coil delivered a high contrast signal over its full length, enabling visualization of the position and curvature of the tip of the guidewire. The ability to see the curvature of the guidewire over several centimeters significantly eased manipulation into targeted vessels and represents an important advance toward MR‐guided vascular interventions.
Intraoperative, real‐time, functional MRI
Authors: Gering David T. , Weber David M. 
Published: March 2007

AbstractFunctional MRI (fMRI) methods have been demonstrated to noninvasively identify motor‐sensory, visual, and other areas of eloquent cortex for guiding surgical intervention. Typically, fMRI data are acquired preoperatively during a conventional surgical planning MRI examination. Unlike direct cortical stimulation at the time of surgery, however, preoperative fMRI methods do not account for the potential movement of tissues (relative to the time of functional imaging) that may occur in the surgical suite as a direct result of the intervention. Recently, an MRI device has been demonstrated for use in the surgical suite that has the potential to reduce the extent of cortical exposure required for the intervention. However, the invasive requirements of cortical mapping may supersede the invasive requirements of the surgical intervention itself. Consequently, we demonstrate here a modification to the intraoperative MRI device that facilitates a noninvasive, real‐time, functional MR examination in the surgical suite.
Shifted rotated keyhole imaging and active tip‐tracking for interventional procedure guidance
Authors: Wendt Michael , Busch Martin , Wetzler Rainer , Zhang Qiang , Melzer Andreas , Wacker Frank , Duerk Jeffrey L. , Lewin Jonathan S. 
Published: March 2007

AbstractThe tools and devices used for patient treatment during interventional procedures must be accurately and safely localized. Recently, procedure guidance has been performed increasingly with MRI, but tool localization has been performed primarily by analyzing the lack of signal caused by displaced excited tissue and/or susceptibility artifacts. In this investigation, a new technique was developed to actively detect and visualize interventional tools using receive coils mounted on the tip of the interventional devices. Unlike earlier methods, in which images from small devicemounted coils are superimposed on a previously acquired image data set, our localization method uses similar tip‐mounted tools in combination with a radiofrequency (RF) switching circuit, standard imaging coils, and specially modified sequences to toggle between the standard and tipmounted receive coil within a single fluoroscopic mode sequence. With this technique, the misregistration between the reported anatomic location and true location of interventional devices is minimized.
Rapid tip tracking with MRI by a limited projection reconstruction technique
Authors: Shimizu Kenji , Mulkern Robert V. , Oshio Koichi , Panych Lawrence P. , Yoo Seung‐Schik , Jolesz Ferenc A. , Kikinis Ron 
Published: March 2007

AbstractTo rapidly track invasive devices within MRI systems, a novel approach using a limited projection reconstruction technique is presented. Our method exploits the difference between images reconstructed from a limited number of projections and serves to depict the tip of a needle during its advancement. This method was implemented on a standard MRI system with a radial fast‐spin‐echo sequence and examined in phantom studies. We demonstrated that the proposed method could track the tip every 300 msec and the tip depicted by the present technique was consistently displaced along the needle by a small distance (5 mm).
Invited. MR findings of Minamata disease — Organic mercury poisoning
Authors: Korogi Yukunori , Takahashi Mutsumasa , Okajima Toru , Eto Komyo 
Published: March 2007

AbstractWe describe MR findings in patients with Minamata disease who have been followed for a long time. All patients examined were affected after daily eating of a large quantity of methylmercury‐contaminated seafood, from 1955 to 1958, and showed typical neurological findings. On MR images, the visual cortex, the cerebellar vermis and hemispheres, and the postcentral cortex are significantly atrophic in Minamata disease. The visual cortex is slightly hypointense on T1‐weighted images and hyperintense on T2‐weighted images, probably representing the pathologic changes of status spongiosus. MRI can demonstrate the lesions located in the calcarine area, cerebellum, and postcentral gyri, which are probably related to three of the characteristic manifestations of this disease: the constriction of the visual fields, ataxia, and sensory disturbance, respectively.
Invited. Hepatitis, cirrhosis, and hepatoma
Authors: Murakami Takamichi , Kim Tonsok , Nakamura Hironobu 
Published: March 2007

AbstractVirus hepatitis and liver cirrhosis are found at high incidence in Asia, and they require not only biochemical examination of blood but also subsequent imaging, because they are often complicated by hepatocellular carcinoma (HCC). It is, therefore, very important to know the specific appearances of hepatitis, liver cirrhosis, and HCC when we diagnose these diffuse liver diseases. Liver necrosis due to severe hepatitis is seen as high intensity on T2‐weighted spin echo images. Regeneration is seen as low intensity on T2‐weighted images. Morphologic and pathologic changes of cirrhotic liver are well demonstrated by MR imaging techniques. Fibrotic septum with inflammatory cell infiltration or rich pseudo bile duct show high intensity on T2‐weighted images, and regenerating nodules shows low intensity. Gradient echo images show regenerating nodules with iron deposition as low‐intensity nodules due to susceptibility artifact. MRI also has the potential to evaluate function of diffuse liver disease, cirrhosis, and hepatitis. MRI can visualize and diagnose HCC objectively. Dynamic MRI is very useful for diagnosing HCC. It is also applied for evaluation of effect after transcatheter arterial chemoembolization, because it shows enhancement only in the viable region at an arterial phase. MRI is less invasive and is thus an extremely important form of liver imaging.
Invited. Ultrafast MR imaging of the abdomen: Echo planar imaging and diffusion‐weighted imaging
Authors: Yamashita Yasuyuki , Tang Yi , Takahashi Mutsumasa 
Published: March 2007

AbstractUltrafast MRI technique has become available with the introduction of new generation MR scanners for abdominal imaging. However, there is no consensus about the optimal imaging acquisition at the present time. Because single shot echo planar imaging (EPI) technique is based on high technology and had just applied in clinical imaging, further clinical investigation will be needed. Currently, the hypersensitivity to magnetic inhomogeneity and local magnetic susceptibility and the low spatial resolution may limit the widespread application of EPI technique. In addition to providing information for morphologic diagnosis, EPI will be more widely used for functional and qualitative diagnosis. Diffusion‐weighted imaging can be used for differentiation of solid tumors according to their different cellular construction, evaluation of cystic lesions based on the different viscosity of their contents, and assessment of diffused pathologic changes in the parenchyma of solid organs. In addition to the previous parameters such as proton density and T1 and T2 values, diffusion factors may provide important information for the qualitative and dynamic evaluation of abdominal pathologic changes. Even though there are many difficulties that must be solved for diffusion‐weighted imaging, a more wide application of this technique is expected through technologic improvement.
Invited. Application of MRI for Small Intestinal Diseases
Authors: Ha Hyun Kwon , Lee Eun Hye , Lim Cheong Hwan , Shin Yong Moon , Jeong Yoong Ki , Yoon Kwon Ha , Lee Moon‐Gyu , Min Young Ii , Auh Yong Ho 
Published: March 2007

AbstractUntil recently, MRI has not been considered to be suitable for the evaluation of the small intestine due to artifacts associated with bowel peristalsis or respiration. However, recent advances of MR techniques enable the acquisition of clear images of the small intestine. Therefore, the purpose of this article is to review the details for the application of MRI in patients with small intestinal diseases. This article discusses bowel preparation and oral contrast agents as well as MR techniques and pulse sequences. Thereafter, the usefulness of MRI for the lesions in the peritoneal cavity or in the gastrointestinal tract are discussed. Small intestinal lesions are categorized into inflammatory, neoplastic, ischemic, and obstructive bowel diseases. In conclusion, MRI can be used as an alternate modality of choice for imaging various diseases of the small intestine.
Invited. Ultrafast T2‐weighted imaging of the abdomen and pelvis: Use of single shot fast spin‐echo imaging
Authors: Tang Yi , Yamashita Yasuyuki , Takahashi Mutsumasa 
Published: March 2007

AbstractSingle shot (SS) rapid acquisition with relaxation enhancement (RARE) and half Fourier SS‐RARE (HFSS‐RARE, HASTE, or SS‐FSE) sequences allow ultrafast imaging acquisition and generate high imaging quality. Images can be acquired within a very short time, without artifacts from physiologic motion. They are widely applied in the abdominal MRI. Clinical application of the ultrafast SS‐RARE imaging techniques provide not only improved temporal resolution but better spatial resolution, higher SNR, and higher tissue contrast. Imaging parameters must be optimized for different MR scanners to obtain diagnostic images.
Invited. Cervical cancer
Authors: Togashi Kaori , Morikawa Kenji , Kataoka Milliam Lika , Konishi Junji 
Published: March 2007

AbstractThe stage estimated by clinical FIGO staging is the main determinant in guiding the treatment decisions. However, clinical FIGO staging does have inherent inaccuracies, because it does not include significant prognostic factors. Presently, MRI is not officially incorporated in the staging workup system; however, it is widely accepted as the most reliable imaging modality in evaluating cervical cancer and in treatment planning. MRI offers direct tumor visualization, accurate assessment of the depth of stromal invasion and tumor volume, lymph node evaluation, and reliable staging accuracy. Published reports show the superiority of MRI over clinical staging, and several recent works on dynamic MRI suggest further improvement of MRI in evaluating cervical cancer.
Invited. Takayasu arteritis: MR manifestations and diagnosis of acute and chronic phase
Authors: Matsunaga Naofumi , Hayashi Kuniaki , Sakamoto Ichiro , Matsuoka Yojiro , Ogawa Yoji , Honjo Kazumitsu , Takano Katsuyuki 
Published: March 2007

AbstractDiagnosis of Takayasu arteritis is difficult because the clinical features are similar to those of other diseases. In the late occlusive or pulseless phase Takayasu arteritis, angiography usually demonstrates luminal changes such as such as stenosis, occlusion, or aneurysmal dilatation of the aorta and pulmonary artery and of their branches. However, absence of such luminal changes does not exclude the possibility of early or systemic phase Takayasu arteritis. Cross‐sectional scanning such as CT scan and MRI plays an important role in demonstrating arterial wall changes in the early diagnosis of Takayasu arteritis. Improvement in the clinical findings and subsidence of the active inflammatory process can be expected with early steroid treatment. The common and uncommon MR appearances of the late occlusive phase and the recently described radiographic features of the early systemic phase are illustrated.
Invited. Application of MR in stereotactic radiosurgery
Authors: Guo Wan‐Yuo 
Published: March 2007

AbstractRadiosurgery, a bladeless brain surgery without opening skull, requires higher imaging accuracy as compared to microsurgery. Accordingly, we must refine the ways we use the MR scanner and interpret the obtained images. A well tuned and regularly calibrated MR scanner provides excellent images, which allow us to define detailed intracranial structures without distortion. This enables us to obtain a reliable imaging diagnosis despite the fact that pathologic diagnosis is not available in many radiosurgical patients. Due to its three‐dimensional imaging and excellence in tissue and spatial contrast, MR is important in exploring new radiosurgical indications. Large arteriovenous malformations (AVM), dural AVM of cavernous sinus and trigeminal neuralgia are some of the successful examples. By using MR, longitudinal investigation of radiosurgical effects becomes feasible. For tumors, the longitudinal studies are important in optimization of dose selection. For AVM, MR is reliable in verification of radiosurgical result. The reliability is comparable to conventional x‐ray angiography. Application of MR enhances the essence of noninvasiveness of radiosurgery.
Characterization of focal liver lesions with half‐Fourier acquisition single‐shot turbo‐spin‐echo (HASTE) and inversion recovery (IR)‐HASTE sequences
Authors: Tang Yi , Yamashita Yasuyuki , Namimoto Tomohiro , Takahashi Mutsumasa 
Published: March 2007

AbstractThe half‐Fourier acquisition single‐shot turbo‐spinecho (HASTE) sequence allows for heavily T2‐weighted images, and the inversion recovery (IR)‐HASTE sequence represents the T1 value of the tissue in a very short time. This study was undertaken to determine whether characterizing focal liver lesions can be made by combination with these very fast sequences. Seventy‐four patients (33 cysts, 28 hemangiomas, and 33 malignant solid liver masses [15 metastatic tumors, 14 hepatocellular carcinomas, and 4 cholangiocarcinomasl]) underwent dynamic CT and breath‐hold abdominal MRI using turbo‐spin‐echo (TSE), HASTE, and IR‐HASTE sequences with variable TI values on a 1.5‐T MR unit. The imaging time for each slice was 2 seconds for HASTE imaging and 2 to 4 seconds for IR‐HASTE imaging. Lesion detection and qualitative characterization were evaluated. Quantitative analysis was performed by measuring the contrast‐to‐noise ratios (CNRs) as well as visual analysis. The inversion time (TI) nulling values were also statistically analyzed. All cystic lesions were detected on both TSE and HASTE imagings. For solid lesions, TSE failed to detect one small solid lesion and HASTE sequence failed to detect three lesions. With HASTE sequences, all cysts and hemangiomas were markedly hyperintense in comparison with malignant solid masses. CNRs of hemangiomas or cysts were significantly higher than those of malignant solid masses (P < .01), and there was no overlap. The TI nulling value was 1,100 ± 100 msec for hemangiomas, 1,900 ± 110 msec for cysts, and 740 ± 140 msec for malignant solid masses. There was no overlap between the TI nulling values of hemangiomas and cysts (P < .01). By combining the CNR from the HASTE sequence and the TI nulling value from the IR‐HASTE sequence, complete discrimination among malignant solid masses, hemangiomas, and cysts of the liver could be made. Application of HASTE (representing T2 values) and IR‐HASTE (representing T1 values) sequences provided a rapid and reliable imaging method for characterizing focal liver lesions without the use of contrast medium.
Enhancement of phase‐contrast MR angiography with superparamagnetic iron oxide
Authors: Tanimoto Akihiro , Yuasa Yuji , Hiramatsu Kyoichi 
Published: March 2007

AbstractThe effect of superparamagnetic iron oxide particles (AMI‐227) was assessed in three‐dimensional (3D) phase‐contrast (PC) MR angiography (MRA), with various scanning parameters for rats at 1.5 T. The blood T1 and T2 before and after 20 μmol Fe/kg of AMI‐227 injection were measured sequentially at .47 T. The visualization of abdominal aorta, renal artery, inferior vena cava, and portal vein was respectively evaluated before and after AMI‐227 injection qualitatively by the four confidence levels and quantitatively by analysis of signal‐to‐noise ratio (SNR) of vessels. The blood T1 and T2 were sufficiently shortened for at least 1 hour after AMI‐227 injection. The visualization of each vessel was improved by AMI‐227 at various velocity encoding (VENC) value, suggesting the extended application of PC‐MRA in various conditions. The optimal flip angle was increased from 20° to 30° in higher VENC after AMI‐227 injection, resulting in higher signal from blood flow. Quantitative analyses showed that the optimal flip angle to achieve the maximum SNR seemed to be 20° in unenhanced images, but the optimal flip angle of the high speed flow was increased by contrast enhancement. The postcontrast PC‐MRA provides the increased sensitivity of slow flow components, even with a high VENC gradient. AMI‐227 can significantly improve SNR to blood vessels during 3D‐PC‐MRA with various scanning parameters.