共查询到20条相似文献,搜索用时 171 毫秒
1.
Minoru Maehara Koshi Ikeda Hiroaki Kurokawa Naoto Ohmura Shigeki Ikeda Yuzo Hirokawa Saori Maehara Keita Utsunomiya Noboru Tanigawa Satoshi Sawada 《Magnetic resonance imaging》2014
Purpose
To investigate whether image quality can be improved using liquid perfluorocarbon pads (Sat Pad) and clarify the optimal fat-suppression method among chemical shift selective (CHESS), water excitation (WEX), and short TI inversion recovery (STIR) methods in diffusion-weighted imaging (DWI) of the head and neck using 3-T magnetic resonance imaging. Correlations between results of visual inspection and quantitative analysis were also examined.Material and Methods
This study was approved by our Institutional Review Board and informed consent was waived. DWI was performed on 25 subjects with/without Sat Pad and using three fat-suppression methods (6 patterns). Image quality was evaluated visually (4-point scales and lesion-depiction capability) and by quantitative analysis (signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)). Two-way repeated-measures analysis of variance (ANOVA) was used to detect significant differences in scores of visual evaluation, SNR, and CNR.Results
Mean visual evaluation scores were significantly higher with Sat Pad using STIR than without Sat Pad for all fat-suppression methods (P < 0.05). DWI with Sat Pad using STIR tended to be useful for depicting lesions. DWI using STIR showed reduced W-SNR (W: whole area of depicted structure) and CNR (between semispinalis capitis muscle and subcutaneous fat) due to fewer artifacts and uniform fat suppression.Conclusion
Combining Sat Pad with STIR provides good image quality for visual inspections. When numerous artifacts are present and fat suppression is insufficient, higher SNR and CNR do not always provide good diagnostic image quality. 相似文献2.
Background and Purpose
A new neurological implant, the Sensor-Reservoir, was developed to provide a relative measurement of ICP, which permits a noninvasive technique to detect and localize occlusions in ventricular drainage systems and, thus, to identify mechanical damage to shunt valves. The “reservoir” of this device can be used to administer medication or a contrast agent, to extract cerebral spinal fluid (CSF), and with the possibility of directly measuring ICP. The Sensor-Reservoir was evaluated to identify possible MRI-related issues at 1.5-T/64-MHz and 3-T/128-MHz.Materials and Methods
Standard testing techniques were utilized to evaluate magnetic field interactions (i.e., translational attraction and torque), MRI-related heating, and artifacts at 3-T for the Sensor-Reservoir. In addition, 12 samples of the Sensor-Reservoir underwent testing to determine if the function of these devices was affected by exposures to various MRI conditions at 1.5-T/64-MHz and 3-T/128-MHz.Results
Magnetic field interactions for the Sensor-Reservoir were not substantial. The heating results indicated a highest temperature rise of 1.8 °C, which poses no patient risks. Artifacts were relatively small in relation to the size and shape of the Sensor-Reservoir, but may interfere diagnostically if the area of interest is near the device. All devices were unaffected by exposures to MRI conditions at 1.5-T/64-MHz and 3-T/128-MHz.Conclusion
When specific guidelines are followed, the Sensor-Reservoir is “MR conditional” for patients undergoing MRI examinations at 3-T or less. 相似文献3.
Laurence Gury-Paquet Antoine Millon Fatima Salami Alexandru Cernicanu Jean-Yves Scoazec Philippe Douek Loïc Boussel 《Magnetic resonance imaging》2012
Purpose
To assess the sensitivity and specificity of intra-plaque hemorrhage (IPH), large lipid-rich necrotic core (LR-NC) and ulceration or cap rupture (UCR) for symptomatic carotid plaque characterization and to evaluate a new imaging score [Hemorrhage, Ulceration or cap rupture, Lipid-rich necrotic Core (HULC) score based on the sum of presence/absence of IPH, UCR and LR-NC; range 0–3] for assessment of recently symptomatic carotid plaques.Material and methods
Twenty-seven recently symptomatic (< 8 weeks) and 36 asymptomatic patients with a carotid plaque thicker than 2 mm were prospectively imaged on a 3-T magnetic resonance (MR) system using high-resolution, multi-contrast MR sequences. Prior to analysis, all images were reviewed to assess image quality of each sequence. Sensitivity and specificity of IPH, LR-NC, UCR and HULC scores were calculated.Results
Fifty-one patients were analyzed (26 symptomatic carotids and 67 asymptomatic carotids) after exclusion of studies with poor image quality. Sensitivity and specificity for symptomatic carotid plaque was, respectively, 46.1% and 97% for IPH, 84.6% and 73.1% for UCR and 80.7% and 76.1% for LR-NC. A HULC score of 2 or more showed a sensitivity of 73% and a specificity of 92.5%.Conclusion
At 3 T, intra-plaque hemorrhage is the most specific criterion to characterize symptomatic carotid plaque. The HULC score offers the best compromise between sensitivity and specificity. 相似文献4.
Purpose
Most objective image quality metrics average over a wide range of image degradations. However, human clinicians demonstrate bias toward different types of artifacts. Here, we aim to create a perceptual difference model based on Case-PDM that mimics the preference of human observers toward different artifacts.Method
We measured artifact disturbance to observers and calibrated the novel perceptual difference model (PDM). To tune the new model, which we call Artifact-PDM, degradations were synthetically added to three healthy brain MR data sets. Four types of artifacts (noise, blur, aliasing or “oil painting” which shows up as flattened, over-smoothened regions) of standard compressed sensing (CS) reconstruction, within a reasonable range of artifact severity, as measured by both PDM and visual inspection, were considered. After the model parameters were tuned by each synthetic image, we used a functional measurement theory pair-comparison experiment to measure the disturbance of each artifact to human observers and determine the weights of each artifact's PDM score. To validate Artifact-PDM, human ratings obtained from a Double Stimulus Continuous Quality Scale experiment were compared to the model for noise, blur, aliasing, oil painting and overall qualities using a large set of CS-reconstructed MR images of varying quality. Finally, we used this new approach to compare CS to GRAPPA, a parallel MRI reconstruction algorithm.Results
We found that, for the same Artifact-PDM score, the human observer found incoherent aliasing to be the most disturbing and noise the least. Artifact-PDM results were highly correlated to human observers in both experiments. Optimized CS reconstruction quality compared favorably to GRAPPA's for the same sampling ratio.Conclusions
We conclude our novel metric can faithfully represent human observer artifact evaluation and can be useful in evaluating CS and GRAPPA reconstruction algorithms, especially in studying artifact trade-offs. 相似文献5.
Marco Moschetta Michele TelegrafoLeonarda Rella Arcangela CapolongoAmato Antonio Stabile Ianora Giuseppe Angelelli 《Magnetic resonance imaging》2014
Objectives
Diffusion imaging represents a new imaging tool for the diagnosis of breast cancer. This study aims to investigate the role of diffusion-weighted MRI with background body signal suppression (DWIBS) for evaluating breast lesions.Methods
90 patients were prospectively evaluated by MRI with STIR, TSE-T2, contrast enhanced THRIVE-T1 and DWIBS sequences. DWIBS were analyzed searching for the presence of breast lesions and calculating the ADC value. ADC values of ≤ 1.44 × 10- 3 mm2/s were considered suspicious for malignancy. This analysis was then compared with the histological findings. Sensitivity, specificity, diagnostic accuracy (DA), positive predictive value (PPV) and negative (NPV) were calculated.Results
In 53/90 (59%) patients, DWIBS indicated the presence of breast lesions, 16 (30%) with ADC values of > 1.44 and 37 (70%) with ADC ≤ 1.44. The comparison with histology showed 25 malignant and 28 benign lesions. DWIBS sequences obtained sensitivity, specificity, DA, PPV and NPV values of 100, 82, 87, 68 and 100%, respectively.Conclusion
DWIBS can be proposed in the MRI breast protocol representing an accurate diagnostic complement. 相似文献6.
Matthew Ethan MacDonald Randall B. Stafford Jérôme Yerly Linda B. Andersen Cheryl R. McCreary Richard Frayne 《Magnetic resonance imaging》2013
Background
Using magnetic resonance (MR) imaging for navigating catheters has several advantages when compared with the current “gold standard” modality of X-ray imaging. A significant drawback to interventional MR is inferior temporal and spatial resolutions, as high spatial resolution images cannot be collected and displayed at rates equal to X-ray imaging. In particular, passive MR catheter tracking experiments that use positive contrast mechanisms have poor temporal imaging rates and signal-to-noise ratio. As a result, with passive methods, it is often difficult to reconstruct motion artifact-free tracking images from areas with motion, such as the thoracic cavity.Methods
In this study, several accelerated MR acquisition strategies, including parallel imaging and compressed sensing (CS), were evaluated to determine which method is most effective at improving the frame rate and passive detection of catheters in regions of physiological motion. Device navigation was performed both in vitro, through the aortic arch of an anthropomorphic chest phantom, and in vivo from the femoral artery, up the descending aorta into the supra-aortic branching vessels in canines.Results and Discussion
The different parallel imaging methods produced images of low quality. CS with a two-fold acceleration was found to be the most effective method for generating tracking images, improving the image frame rate to 5.2 Hz, while maintaining a relatively high in-plane resolution. Using CS, motion artifact was decreased and the catheters were visualized with good conspicuity near the heart.Conclusions
The improvement in the imaging frame rate by image acceleration was sufficient to overcome motion artifacts and to better visualize catheters in the thoracic cavity with passive tracking. CS preformed best at tracking. Navigation with passive MR catheter tracking was demonstrated from the femoral artery to the carotid artery in canines. 相似文献7.
Colleen M. Costelloe John E. Madewell Vikas Kundra Robyn K. Harrell Roland L. Bassett Jr. Jingfei Ma 《Magnetic resonance imaging》2013
Purpose
The purpose of the study was to evaluate the conspicuity of bone metastases on each of the numerous sequences produced by fast Dixon-based multisequence whole-body (WB) magnetic resonance imaging (MRI) scanning in order to determine the most clinically useful sequences overall and per anatomic region.Materials and Methods
Twenty-seven breast cancer patients with bone metastases were prospectively studied with fast Dixon-based WB MRI including head/neck, chest, abdominal, pelvic, thigh, calf/feet and either cervical, thoracic and lumbar or cervical/thoracic and thoracic/lumbar regions. Sequences included coronal T2, axial T1 without and with intravenous gadolinium (+ C), sagittal T1 spine + C, each associated fat-only (FO) and fat-saturated (FS) sequence, axial diffusion-weighted imaging (DWI) and short tau inversion recovery (STIR). Blinded reviewers evaluated lesion conspicuity, a surrogate of clinical utility, on a five-point scale per anatomic region. Sequences were compared using analysis of variance, differences were detected with Tukey's honestly significant difference test, and the four sequences with highest mean conspicuity were compared to the remainder overall and per anatomic region.Results
Overall, a significant lesion conspicuity difference was found (P < .0001), and lesion conspicuity was significantly higher on FS T1 + C, FO T1 + C, T1 + C sagittal and FS T1 + C axial sequences (P < .0001). Per-region results were the same in the head/neck. Other sequences overlapped with these and included the following: chest/abdomen — FO T2, DWI; pelvis — DWI, FO T2; thigh — FS T2, FO T2, FO T1 + C; calf/feet — FS T2, DWI, FO T2, STIR.Conclusion
Overall, bone lesions were most conspicuous on FS T1 + C sagittal, FO T1 + C sagittal, T1 + C sagittal and FS T1 + C axial fast Dixon WB MRI sequences. 相似文献8.
Yusuke Inoue Hirofumi Hata Ai Nakajima Yuji Iwadate Gou Ogasawara Keiji Matsunaga 《Magnetic resonance imaging》2014
Purpose
To optimize the navigator-gating technique for the acquisition of high-quality three-dimensional spoiled gradient-recalled echo (3D SPGR) images of the liver during free breathing.Materials and methods
Ten healthy volunteers underwent 3D SPGR magnetic resonance imaging of the liver using a conventional navigator-gated 3D SPGR (cNAV-3D-SPGR) sequence or an enhanced navigator-gated 3D SPGR (eNAV-3D-SPGR) sequence. No exogenous contrast agent was used. A 20-ms wait period was inserted between the 3D SPGR acquisition component and navigator component of the eNAV-3D-SPGR sequence to allow T1 recovery. Visual evaluation and calculation of the signal-to-noise ratio were performed to compare image quality between the imaging techniques.Result
The eNAV-3D-SPGR sequence provided better noise properties than the cNAV-3D-SPGR sequence visually and quantitatively. Navigator gating with an acceptance window of 2 mm effectively inhibited respiratory motion artifacts. The widening of the window to 6 mm shortened the acquisition time but increased motion artifacts, resulting in degradation of overall image quality. Neither slice tracking nor incorporation of short breath holding successfully compensated for the widening of the window.Conclusion
The eNAV-3D-SPGR sequence with an acceptance window of 2 mm provides high-quality 3D SPGR images of the liver. 相似文献9.
Background and Purpose
Fine-mesh braided, stent-like structures (flow diverters) have been proposed for treatment of brain aneurysms. To date, the safety of performing magnetic resonance imaging (MRI) in patients with these implants is unknown. Therefore, the purpose of this study was to evaluate MRI issues at 3-T for a new flow-diverting implant used to treat brain aneurysms.Methods
The Surpass NeuroEndoGraft (Surpass Medical, Ltd., Tel Aviv, Israel) underwent evaluation for magnetic field interactions, MRI-related heating and artifacts using standardized techniques. Magnetic field interactions were assessed for this implant with regard to translational attraction (i.e., using the deflection angle technique) and torque (qualitative assessment method). MRI-related heating was evaluated by placing the implant in a gelled-saline-filled, head/torso phantom and performing MRI using a transmit/receive radiofrequency body coil at a whole-body-averaged specific absorption rate of 2.9 W/kg for 15 min. Artifacts were characterized using T1-weighted, spin echo (SE) and gradient echo (GRE) pulse sequences.Results
The Surpass NeuroEndoGraft exhibited minor magnetic field interactions (21° deflection angle and no torque), which were acceptable from a safety consideration. Heating was not substantial, with the highest temperature change being 2.3°C (background temperature rise without the implant was 1.5°C). Artifacts may create issues if the area of interest is in the same area or close to this implant.Conclusions
The findings demonstrated that it would be acceptable for patients with this next-generation, flow-diverting implant to undergo MRI at 3-T or less. 相似文献10.
Lei Jiang Yiming Zhou Cheng Zhou Min Chen Yongming Dai Yuan Fu Xuna Zhao 《Magnetic resonance imaging》2014
Purpose
To investigate the influence of dual-source parallel radiofrequency (RF) excitation on clinical breast MR images.Methods
A 3 T MR system with both dual-source and conventional single-source RF excitations was used to examine 22 patients. Axial TSE-T2WI with fat suppression, TSE-T1WI without fat suppression, THRIVE (3D field echo) and DWI (SE-EPI) were obtained by using both excitation techniques. Image homogeneity, image contrast and lesion conspicuity were measured or independently scored by two radiologists and were compared by paired-sample t test or Wilcoxon test.Results
Both excitations revealed 24 lesions. For SE sequences using dual-source mode, image homogeneity was improved (P = 0.00), scan time was reduced, and ghost artifacts on DWI were significantly reduced (P = 0.00). However, image contrast was not increased and lesion conspicuity had no significant difference between two modes, except DWI on which lesion conspicuity was significantly improved (P = 0.00), due to less ghost artifacts. For field-echo sequence, image homogeneity, acquisition time, image contrast and lesion conspicuity had no significant difference between the two modes.Conclusions
Dual-source parallel RF transmission has some added value for improving breast image quality. However, its value is limited in terms of improving lesion detection and characterization. 相似文献11.
Matthias Rief Moritz Wagner Tobias Franiel Viola Bresan Matthias Taupitz Christian Klessen Bernd Hamm Patrick Asbach 《Magnetic resonance imaging》2009,27(9):1223-1229
Purpose
To investigate the image quality and detection rate of focal liver lesions by comparing a T2-weighted breath-hold single-shot sequence and a T2-weighted high spatial resolution fast spin-echo sequence with respiratory triggering via unenhanced and superparamagnetic iron oxide (SPIO)-enhanced liver imaging.Materials and Methods
The study was approved by the local ethical review board; informed consent was waived. Liver-lesion contrast was measured and a qualitative consensus evaluation of image quality and lesion detection was performed in 42 consecutive patients using a 1.5-T MR system.Results
The liver-lesion contrast was significantly higher (P<.05) for the respiratory-triggered sequence compared to the breath-hold sequence regarding unenhanced and SPIO-enhanced imaging. The respiratory-triggered sequences revealed significantly higher image quality scores as well as higher numbers of detected liver lesions compared to the breath-hold sequence on unenhanced and SPIO-enhanced imaging. The SPIO contrast did not significantly improve the number of detected lesions on the respective sequences (P>.05).Conclusion
We find that respiratory-triggered fast spin-echo sequences produce a higher image quality and a more precise liver-lesion detection rate thereby justifying the increased acquisition time necessary for this method. 相似文献12.
Objectives
A patient with a breast tissue expander may require a diagnostic assessment using magnetic resonance imaging (MRI). To ensure patient safety, this type of implant must undergo in vitro MRI testing using proper techniques. Therefore, this investigation evaluated MRI issues (i.e., magnetic field interactions, heating, and artifacts) at 3-Tesla for a breast tissue expander with a remote port.Methods
A breast tissue expander with a remote port (Integra Breast Tissue Expander, Model 3612-06 with Standard Remote Port, PMT Corporation, Chanhassen, MN) underwent evaluation for magnetic field interactions (translational attraction and torque), MRI-related heating, and artifacts using standardized techniques. Heating was evaluated by placing the implant in a gelled-saline-filled phantom and MRI was performed using a transmit/receive RF body coil at an MR system reported, whole body averaged specific absorption rate of 2.9-W/kg. Artifacts were characterized using T1-weighted and GRE pulse sequences.Results
Magnetic field interactions were not substantial and, thus, will not pose a hazard to a patient in a 3-Tesla or less MRI environment. The highest temperature rise was 1.7 °C, which is physiologically inconsequential. Artifacts were large in relation to the remote port and metal connector of the implant but will only present problems if the MR imaging area of interest is where these components are located.Conclusions
A patient with this breast tissue expander with a remote port may safely undergo MRI at 3-Tesla or less under the conditions used for this investigation. These findings are the first reported at 3-Tesla for a tissue expander. 相似文献13.
Objectives
To objectively identify possible differences in the signal characteristics of benign and malignant soft tissue masses (STM) on magnetic resonance (MR) images by means of texture analysis and to determine the value of these differences for computer-assisted lesion classification.Method
Fifty-eight patients with histologically proven STM (benign, n=30; malignant, n=28) were included. STM texture was analyzed on routine T1-weighted, T2-weighted and short tau inversion recovery (STIR) images obtained with heterogeneous acquisition protocols. Fisher coefficients (F) and the probability of classification error and average correlation coefficients (POE+ACC) were calculated to identify the most discriminative texture features for separation of benign and malignant STM. F>1 indicated adequate discriminative power of texture features. Based on the texture features, computer-assisted classification of the STM by means of k-nearest-neighbor (k-NN) and artificial neural network (ANN) classification was performed, and accuracy, sensitivity and specificity were calculated.Results
Discriminative power was only adequate for two texture features, derived from the gray-level histogram of the STIR images (first and 10th gray-level percentiles). Accordingly, the best results of STM classification were achieved using texture information from STIR images, with an accuracy of 75.0% (sensitivity, 71.4%; specificity, 78.3%) for the k-NN classifier, and an accuracy of 90.5% (sensitivity, 91.1%; specificity, 90.0%) for the ANN classifier.Conclusion
Texture analysis revealed only small differences in the signal characteristics of benign and malignant STM on routine MR images. Computer-assisted pattern recognition algorithms may aid in the characterization of STM, but more data is necessary to confirm their clinical value. 相似文献14.
Chengcheng Zhu Umar Sadat Andrew J. Patterson Zhongzhao Teng Jonathan H. Gillard Martin J. Graves 《Magnetic resonance imaging》2014
Objective
Development of a fast 3D high-resolution magnetic resonance imaging (MRI) protocol for improved carotid artery plaque imaging.Methods
Two patients with carotid atherosclerosis disease underwent 3D high-resolution MRI which included time-of-flight and T1-weighted variable flip angle, fast-spin-echo (FSE) imaging, pre- and post-intravenous gadolinium-based contrast agent administration.Results
Good quality images with intrinsic blood suppression were obtained pre- and post-contrast administration using a 3D FSE sequence. The plaque burden, lipid core volume, hemorrhage volume and fibrous cap thickness were well determined.Conclusions
3D high-resolution MR imaging of carotid plaque using TOF and 3D FSE can achieve high isotropic resolution, large coverage, and excellent image quality within a short acquisition time. 相似文献15.
David K.W. Yeung Kunwar S. Bhatia Yolanda Y.P. Lee Ann D. King Philippe Garteiser Ralph Sinkus Anil T. Ahuja 《Magnetic resonance imaging》2013
Purpose
The purpose was to describe the design and fabrication of a driver suitable for magnetic resonance elastography (MRE) of the head and neck and to assess its performance in evaluating human parotid gland, lymph nodes and thyroid at 3.0 T.Materials and methods
A head and neck driver was fabricated using a commercial transducer, headrest mould and piston extension. Driver performance was tested using a motion-sensitized spin-echo MRE pulse sequence. Six healthy volunteers and three patients (two metastatic nodes and one papillary carcinoma) were evaluated using MRE. Viscoelastic maps were computed to obtain storage modulus (G’) and loss modulus (G”) of the normal parotid and thyroid, metastatic node and thyroid cancer. Reproducibility was assessed by coefficient of variation.Results
All subjects completed MRE examination without discomfort. Initial G’ and G” values were as follows: normal parotid gland, 1.12 kPa and 0.48 kPa; thyroid, 0.58 kPa and 0.42 kPa; metastatic node, 0.66 kPa and 0.58 kPa; and thyroid cancer, 0.17 kPa and 0.28 kPa. Based on parotid data, the coefficient of variation for G’ and G” was 4.7% and 9.8%.Conclusion
A new MRE driver for head and neck was successfully implemented, and our initial results suggested the device was suitable for the mechanical assessment of tissues in the head and neck. 相似文献16.
MR Imaging of total hip arthroplasty: comparison among sequences to study the sciatic nerve at 1.5 T
Alberto Tagliafico Andrea Podestà Andrea Assini Leonardo Boccacini Giovanni Serafini Massimo Calabrese Carlo Martinoli 《Magnetic resonance imaging》2010
Purpose
This study was done to test a series of MR sequences for evaluating the sciatic nerve after total hip arthroplasty (THA).Material and Methods
The study protocol was approved by the institutional review board. Informed consent was obtained from all patients. Twenty-five patients (11 men and 14 women mean age: 62.3±5.7 years) with THA were included in this prospective study. MRI protocol included sequences that were preliminarily tailored for nerve imaging in patients with THA: proton density (PD)-weighted turbo SE, T1-weighted turbo SE (TSE) 3 mm thickness, T1-weighted turbo SE (TSE) 6 mm thickness, T1-weighted turbo SE with high bandwidth (TSE hBW), T2- weighted TSE, T2-weighted with fat saturation and short-tau inversion recovery (STIR). For each sequence, we evaluated the visibility of the sciatic nerve using a semiquantitative score (0=total masking; 1=insufficient visibility; 2=sufficient visibility; 3=optimal visibility). The sum of the scores given to each sequence was divided by the maximal sum, obtaining a percentage visibility index. Friedman and sign tests were used for statistical analysis.Results
MR examination time was approximately 40 min. No patients reported pain, heat or symptoms related to nerve stimulation. The visibility index ranged between 88% and 70% for the first four sequences. The T1-weighted TSE hBW sequence had the best visibility index (P<.05). The visibility indexes of the first four sequences were significantly higher (P<.004, sign test) than those of the remaining three sequences.Conclusion
The sciatic nerve could be studied at 1.5 T in patients following THA. The nerve is better visualized with T1-weighted TSE hBW sequences. On T2-weighted sequences and STIR, the visibility of the nerve is low. 相似文献17.
Objective
Coronary artery stents are made from metallic mesh and, therefore, to ensure patient safety, these implants must be evaluated to determine risks associated with MRI. Recently, bioabsorbable scaffolds, which have metallic markers, have been developed for use in the coronary arteries. Because of the metallic materials, these implants may present issues for patients undergoing MRI. Therefore, the objective of this investigation was to assess MRI issues (i.e., magnetic field interactions, MRI-related heating, and artifacts at 3 T) for a new bioabsorbable, coronary artery scaffold with metallic markers.Methods
A bioabsorbable, coronary artery scaffold (Mirage Microfiber Scaffold) underwent assessments for magnetic field interactions, MRI-related heating, and artifacts at 3-Tesla using standard techniques. MRI-related heating was evaluated with the scaffold placed in a gelled-saline-filled phantom and MRI was performed at an MR system reported, whole body averaged SAR of 2.9 W/kg for 15 minutes. Artifacts were characterized using T1-weighted spin echo and gradient echo, pulse sequences.Results
There were no magnetic field interactions. The highest temperature rise was 1.6 °C (highest background temperature rise, 1.6 °C). Artifacts were relatively small in relation to the size and shape of this coronary artery scaffold. Notably, the lumen of the scaffold could be visualized on the GRE pulse sequence.Conclusion
The results demonstrated that the coronary artery scaffold is acceptable (or “MR conditional,” using current MRI labeling terminology) for a patient undergoing an MRI procedure at 3 T or less. To our knowledge, this is the first bioabsorbable, coronary artery scaffold that has been evaluated for MRI issues. 相似文献18.
Objective
In general, low-field MRI scanners such as the 0.5- and 1-T ones produce images that are poor in quality. The motivation of this study was to lessen the noise and enhance the signal such that the image quality is improved. Here, we propose a new approach using stochastic resonance (SR)-based transform in Fourier space for the enhancement of magnetic resonance images of brain lesions, by utilizing an optimized level of Gaussian fluctuation that maximizes signal-to-noise ratio (SNR).Materials and Methods
We acquired the T1-weighted MR image of the brain in DICOM format. We processed the original MR image using the proposed SR procedure. We then tested our approach on about 60 patients of different age groups with different lesions, such as arteriovenous malformation, benign lesion and malignant tumor, and illustrated the image enhancement by using just-noticeable difference visually as well as by utilizing the relative enhancement factor quantitatively.Results
Our method can restore the original image from noisy image and optimally enhance the edges or boundaries of the tissues, clarify indistinct structural brain lesions without producing ringing artifacts, as well as delineate the edematous area, active tumor zone, lesion heterogeneity or morphology, and vascular abnormality. The proposed technique improves the enhancement factor better than the conventional techniques like the Wiener- and wavelet-based procedures.Conclusions
The proposed method can readily enhance the image fusing a unique constructive interaction of noise and signal, and enables improved diagnosis over conventional methods. The approach well illustrates the novel potential of using a small amount of Gaussian noise to improve the image quality. 相似文献19.
Bertine L. Stehouwer Dennis W.J. KlompMies A. Korteweg Helena M. VerkooijenPeter R. Luijten Willem P.Th.M. MaliMaurice A.A.J. van den Bosch Wouter B. Veldhuis 《Magnetic resonance imaging》2013
Purpose
Here we describe our first experience with contrast-enhanced (CE) MRI of breast cancer at 7 tesla (T), compared to 3 T and histopathology.Materials and Methods
A 52 year old female patient with a mammographically suspicious breast mass (BI-RADS V) underwent 7 T CE-MRI. Results were described according to the BI-RADS-MRI criteria and compared to 3 T and histopathology.Results
After contrast administration, a homogeneously enhancing, irregular spiculated mass was depicted at both 3 T and 7 T; sizes were identical. The most malignant kinetic curve was characterized by a rapid initial rise followed by a wash-out pattern in the delayed phase, i.e. a type 3 curve, at both field strengths. Even though T1-effects of contrast agents are suggested to be reduced at higher fields, quantification of contrast enhancement-to-noise ratio showed a ratio of 4.6 at 7 T and 2.8 at 3 T when comparing contrast-to-noise of the mass before and after contrast administration. Both examinations, using a single dose of gadolinium-based contrast agent, achieved good image quality. Final histopathological evaluation showed an invasive ductulolobular carcinoma with an intraductal component.Conclusion
This initial experience suggests that clinical contrast-enhanced 7 T MRI of the breast is technically feasible and may allow BI-RADS-conform analysis. 相似文献20.
Qunli Deng Scott B. King Vyacheslav Volotovskyy Boguslaw Tomanek Jonathan C. Sharp 《Magnetic resonance imaging》2013