Strategies for inner volume 3D fast spin echo magnetic resonance imaging using nonselective refocusing radio frequency pulses

Fast spin echo (FSE) trains elicited by nonselective "hard" refocusing radio frequency (RF) pulses have been proposed as a means to enable application of FSE methods for high-resolution 3D magnetic resonance imaging (MRI). Hard-pulse FSE (HPFSE) trains offer short (3-4 ms) echo spacings, but are unfortunately limited to imaging the entire sample within the coil sensitivity thus requiring lengthy imaging times, consequently limiting clinical application. In this work we formulate and analyze two general-purpose combinations of 3D HPFSE with inner volume (IV) MR imaging to circumvent this limitation. The first method employs a 2D selective RF excitation followed by the HPFSE train and focuses on required properties of the spatial excitation profile with respect to limiting RF pulse duration in the 5-6 ms range. The second method employs two orthogonally selective 1D RF excitations (a 90x degrees - 180y degrees pair) to generate an echo from magnetization within the volume defined by their intersection. Subsequent echoes are formed via the HPFSE train, placing the focus of the method on (a) avoiding spurious echoes that may arise from transverse magnetization located outside the slab intersection when it is unavoidably affected by the nonselective refocusing pulses and (b) avoiding signal losses due to the necessarily different spacing (in time) of the RF pulse applications. The performance of each method is experimentally measured using Carr-Purcell-Meiboom-Gill (CPMG) multi-echo imaging, enabling examination of the magnetization evolution throughout the echo train. The methods as implemented achieve 95% to 97% outer volume signal suppression, and higher suppression appears to be well within reach, by further refinement of the selective RF excitations. Example images of the human brain and spine are presented with each technique. We conclude that the SNR efficiency of volume imaging in conjunction with the short echo spacing afforded by hard pulse trains enables high-resolution 3D HPFSE MRI of a small field-of-view (FOV) with minimal aliasing artifact.     

3D Isotropic Super-resolution Prostate MRI Using Generative Adversarial Networks and Unpaired Multiplane Slices

We developed a deep learning–based super-resolution model for prostate MRI. 2D T2-weighted turbo spin echo (T2w-TSE) images are the core anatomical sequences in a multiparametric MRI (mpMRI) protocol. These images have coarse through-plane resolution, are non-isotropic, and have long acquisition times (approximately 10–15 min). The model we developed aims to preserve high-frequency details that are normally lost after 3D reconstruction. We propose a novel framework for generating isotropic volumes using generative adversarial networks (GAN) from anisotropic 2D T2w-TSE and single-shot fast spin echo (ssFSE) images. The CycleGAN model used in this study allows the unpaired dataset mapping to reconstruct super-resolution (SR) volumes. Fivefold cross-validation was performed. The improvements from patch-to-volume reconstruction (PVR) to SR are 80.17%, 63.77%, and 186% for perceptual index (PI), RMSE, and SSIM, respectively; the improvements from slice-to-volume reconstruction (SVR) to SR are 72.41%, 17.44%, and 7.5% for PI, RMSE, and SSIM, respectively. Five ssFSE cases were used to test for generalizability; the perceptual quality of SR images surpasses the in-plane ssFSE images by 37.5%, with 3.26% improvement in SSIM and a higher RMSE by 7.92%. SR images were quantitatively assessed with radiologist Likert scores. Our isotropic SR volumes are able to reproduce high-frequency detail, maintaining comparable image quality to in-plane TSE images in all planes without sacrificing perceptual accuracy. The SR reconstruction networks were also successfully applied to the ssFSE images, demonstrating that high-quality isotropic volume achieved from ultra-fast acquisition is feasible.

     

Evaluation of congenital heart disease by three-dimensional magnetic resonance imaging

This study was undertaken to compare electrocardiographically gated magnetic resonance imaging (MRI) to established imaging modalities in the detection of complex intra- and extracardiac morphologic defects. Twenty-three patients with congenital cardiac abnormalities were imaged by four methods: cardiac catheterization, echocardiography, two-dimensional (2D) transaxial MRI, and three-dimensional (3D) MRI surface reconstruction. Observers with experience in congenital cardiac disease diagnosis (two for echo, one for catheterization, two for 2D MR, and three for 3D MR) evaluated the images in a blinded fashion, and the results were analyzed with receiver operating characteristic (ROC) analysis. Overall, cardiac catheterization had the best diagnostic performance. The diagnostic value of routine 2D cardiac MR images and 3D MR reconstruction images were similar to that of echocardiography. All of the modalities performed poorly in the diagnosis of extracardiac defects and atrial septal defects.     

兔VX2恶性骨肿瘤骨髓内浸润范围MRI与病理对照研究

目的 探讨MRI常用序列在判断恶性骨肿瘤骨髓内浸润范围及显示病变阳性率方面的应用价值。方法 2010年6月—2012年3月选取兔龄8周、体质量2.0～3.0 kg的雄性新西兰大白兔26只,1只制备荷瘤兔,25只接种VX2肉瘤肿瘤组织块于兔右侧胫骨平台下2 cm处的骨髓腔内,制备成恶性骨肿瘤模型兔。模型兔制备成功后,在全身麻醉状态下行MRI检查。选取肿瘤纵径最大层面,观察并测量MR 自旋回波(SE) T₁WI、脂肪抑制FSE T₂WI、短时间反转恢复序列(STIR)、脂肪抑制SE T₁WI 增强序列图像中的髓内肿瘤浸润纵径。MRI检查完成后,处死模型兔,切取兔右下肢标本,用硬组织切片系统自MR扫描起始点间隔4 mm连续切割,选取与MRI中骨髓内肿瘤纵径最大层面相对应的标本切片进行肿瘤髓内浸润纵径的测量和病理学观察。采用单因素方差分析和配对t检验,比较MR不同序列之间及MR不同序列和病理切片检查之间肿瘤髓内浸润纵径测量值的差异;并对MR不同序列间显示肿瘤髓内浸润的阳性率｛[真阳性/(真阳性+假阳性)]×100%｝进行χ²检验。结果 成功制备21只模型兔。MRI 中SE T₁WI、脂肪抑制FSE T₂WI、STIR、脂肪抑制SE T₁WI 增强序列间肿瘤髓内浸润纵径的测量值分别为(44.5±10.8)mm、(41.0±9.7)mm、(40.7±9.4)mm、(40.3±9.5)mm,4种序列之间的差异无统计学意义(F= 0.802,P＞0.05)。 4种序列图像的肿瘤髓内浸润纵径测量值均大于病理标本测量值(39.3±9.3)mm,配对t检验分析差异均有统计学意义(t=7.053、6.334、6.445、8.150,P值均＜0.01)。MRI不同序列显示肿瘤髓内浸润阳性率由高到低依次为脂肪抑制SE T₁WI增强序列(76.54%,62/81)、STIR(57.69%,45/78)、脂肪抑制FSE T₂WI(52.05%,38/73)、SE T₁WI(45.71%,32/70),差异有统计学意义(χ²=16.857,P＜0.01);组间两两比较,脂肪抑制 SE T₁WI 增强序列显示的肿瘤髓内浸润阳性率高于SE T₁WI、脂肪抑制FSE T₂WI,差异均有统计学意义(P值均＜0.05)。结论 MRI不同序列中,脂肪抑制 SE T₁WI 增强序列图像测量肿瘤髓内浸润纵径的测量值与病理测量值最为接近,显示肿瘤髓内浸润的阳性率最高,可作为观察肿瘤髓内浸润范围及显示病变阳性率的优选MR序列。     

Feature space analysis: effects of MRI protocols.

We present a method for exploring the relationship between the image segmentation results obtained by an optimal feature space method and the MRI protocols used. The steps of the work accomplished are as follows. (1) Patients with brain tumors were imaged on a 1.5 T General Electric Signa MRI System using multiple protocols (T1 and T2-weighted fast spin-echo and FLAIR). T1-weighted images were acquired before and after gadolinium injection. (2) Image volumes were co-registered, and images of a slice through the center of the tumor were selected for processing. (3) For each patient, several image sets were defined by selecting certain MR images (e.g., 4T2's+ IT1, 4T2's+FLAIR, 2T2's+ 1T1). (4) Using each image set, the optimal feature space was generated and images were segmented into normal tissues and different tumor zones. (5) Segmentation results obtained using the different MRI sets were compared. Based on the analysis results from 27 image sets, we found that the locations of the clusters for the tumor zones and their corresponding regions in the image domain changed as a function of the MR images (MRI protocols) used. However, the segmentation results for the total lesion and normal tissues remained relatively unchanged.     

Detection of in situ mammary cancer in a transgenic mouse model: in vitro and in vivo MRI studies demonstrate histopathologic correlation

Improving the prevention and detection of preinvasive ductal carcinoma in situ (DCIS) is expected to lower both morbidity and mortality from breast cancer. Transgenic mouse models can be used as a 'test bed' to develop new imaging methods and to evaluate the efficacy of candidate preventive therapies. We hypothesized that despite its microscopic size, early murine mammary cancer, including DCIS, might be accurately detected by MRI. C3(1) SV40 TAg female mice (n = 23) between 10 and 18 weeks of age were selected for study. Eleven mice were subjected to in vitro imaging using a T(2)-weighted spin echo sequence and 12 mice were selected for in vivo imaging using a T(1)-weighted gradient echo, a T(2)-weighted spin echo and high spectral and spatial resolution imaging sequences. The imaged glands were carefully dissected, formalin fixed and paraffin embedded, and then H&E stained sections were obtained. The ratio of image-detected versus histologically detected cancers was obtained by reviewing the MR images and H&E sections independently and using histology as the gold standard. MR images were able to detect 12/12 intramammary lymph nodes, 1/1 relatively large ( approximately 5 mm) tumor, 17/18 small ( approximately 1 mm) tumors and 13/16 ducts distended with DCIS greater than 300 microm. Significantly, there were no false positives-i.e., image detection always corresponded to a histologically detectable cancer in this model. These results indicate that MR imaging can reliably detect both preinvasive in situ and early invasive mammary cancers in mice with high sensitivity. This technology is an important step toward the more effective use of non-invasive imaging in pre-clinical studies of breast cancer prevention, detection and treatment.     

3.0T MR前列腺扫描参数的应用

目的比较不同扫描参数对前列腺MRI图像质量及扫描时间的影响。方法应用GE Signa Excite 3.0T MR和8通道体部线圈,对13名健康志愿者中的第一组前7位采用抑脂FSE-XLT2WI、非抑脂FSE-XL T1WI序列和FSE-IR进行前列腺MR成像,对比不同参数图像的信噪比;对第二组后6位志愿者根据图像质量及扫描时间选择适合前列腺MR成像的扫描序列和参数。结果在其它参数相同时采用抑脂FSE-XL T2WI序列、非抑脂FSE-XL T1WI序列、FSE-IR序列,可在较短的扫描时间内获得较高的前列腺图像质量。结论 3.0T MR前列腺成像,通过优化参数可节约扫描时间、提高图像质量。     

Magnetic resonance imaging of third molars: developing a protocol suitable for forensic age estimation

Background: Established dental age estimation methods in sub-adults study the development of third molar root apices on radiographs. In living individuals, however, avoiding ionising radiation is expedient. Studying dental development with magnetic resonance imaging complies with this requirement, adding the advantage of imaging in three dimensions.

Aim: To elaborate the development of an MRI protocol to visualise all third molars for forensic age estimation, with particular attention to the development of the root apex.

Subjects and methods: Ex vivo scans of porcine jaws and in vivo scans of 10 volunteers aged 17–25 years were performed to select adequate sequences. Studied parameters were T1 vs T2 weighting, ultrashort echo time (UTE), fat suppression, in plane resolution, slice thickness, 3D imaging, signal-to-noise ratio, and acquisition time. A bilateral four-channel flexible surface coil was used. Two observers evaluated the suitability of the images.

Results: T2-weighted images were preferred to T1-weighted images. To clearly distinguish root apices in (almost) fully developed third molars an in plane resolution of 0.33?×?0.33?mm² was deemed necessary. Taking acquisition time limits into account, only a T2 FSE sequence with slice thickness of 2?mm generated images with sufficient resolution and contrast. UTE, thinner slice T2 FSE and T2 3D FSE sequences could not generate the desired resolution within 6.5?minutes.

Conclusion: Three Tesla MRI of the third molars is a feasible technique for forensic age estimation, in which a T2 FSE sequence can provide the desired in plane resolution within a clinically acceptable acquisition time.     

蝶鞍区薄层横断面解剖与MRI对照研究

目的 研究蝶鞍区的薄层断层解剖与对应的MRI图像,探讨该区域结构在薄层断层解剖上的变化规律.为影像学诊断及临床开展该区手术提供详细的形态学资料.方法取2例成人头部标本,用1.5T MRI以眦耳线为基线进行扫描获取薄层MRI图像,经冷冻包埋后采用铣削精度为0.001mm的SKC500型数控机床由下往上铣削层厚为0.1mm的薄层标本,其中蝶鞍区层厚为0.05mm.从标本中选取典型断面,与相应的MRI图像相对照,观察蝶鞍区的重要解剖结构. 结果 共获得MRI图像T1加权40幅和41幅,T2加权40幅和41幅,薄层断层图像304张和310张.在薄层断层标本上进行连续追踪,并与相应的MRI图像对照,总结其规律.在垂体层面能清楚地显示海绵窦内结构及其相互关系:1.颈内动脉弯曲走行于海绵窦内,且与海绵窦之间形成几个间隙;2.第Ⅲ、Ⅳ、Ⅵ脑神经以及三叉神经的眼神经支、上颌神经支在海绵窦外侧壁由前向后依次排列.在视交叉层面能够清楚地看到垂体柄穿过鞍膈与垂体相连.结论冷冻数控铣削技术获得的超薄断面与MRI图像对照能精确显示蝶鞍区的微细解剖结构,为该区病变的断层影像诊断和临床治疗提供实用的亚毫米断层解剖学依据.     

Tomographic abdominal anatomy with magnetic resonance color composites

Magnetic resonance imaging (MRI) is an excellent modality for tomographically visualizing abdominal structures, particularly the liver, In an effort to simulate the natural color scheme of the living abdomen using MRI, we have generated color composites from sets of gray tone MR images obtained at corresponding anatomic slice positions from two healthy individuals. Pulse sequences used for our image sets included T1-, T2-, and proton density-weighted spin echo sequences as well as an angiographic FISP gradient echo sequence. A PC/AT-compatible computer with 24-bit graphics display capbilites, along with commerical and customized image-processing software, was used for composite generation. The applied colors were selected based on quantitative characteristics tissue intensity patterns so that tissue contrast could be optimized in the final image. The generated composites were correlated with cadaver sections to evaluate the color scheme of these false-colored images. With our composite generation techniques, it was possible to generated near-natural appearing color images of the abdomen. Color composites may be useful for teaching human cross-sectional anatomy and may also have diagnostic applications in abdominal MRI studies. © 1992 Wiley-Liss, Inc.     

SiPM-PET with a short optical fiber bundle for simultaneous PET-MR imaging

For positron emission tomography (PET) inserts to magnetic resonance imaging (MRI) applications, optical fibers have been used for some time to transfer scintillation photons to photomultiplier tubes positioned outside the fringe magnetic field. We previously proposed a novel utilization of an optical fiber for good radio frequency (RF) transmission from body coils to an imaging object. Optical fiber bundles between silicon photomultipliers (SiPM) and scintillation crystals provide an increased spacing between RF-shielded electronics boxes, facilitating RF passage from the body RF coils to imaging objects. In this paper, we present test results of a SiPM-PET system with a short optical fiber bundle for simultaneous PET-MR imaging. We built the SiPM-PET system which consisted of 12 SiPM-PET modules; each module was assembled with a lutetium yttrium oxyorthosilicatecrystal block, a 31?mm optical fiber bundle, a Hamamatsu multi-pixel photon counter S11064-050P and a signal processing box shielded with copper. The SiPM-PET system, with a face-to-face distance of 71?mm, was placed inside a 3 T MRI. A small surface coil placed inside the SiPM-PET system was used to receive the signal from phantoms while the body RF coil transmitted the RF pulses. The SiPM-PET system showed little performance degradation during the simultaneous PET-MR imaging and it caused no significant degradation of MR images with turbo spin echo (TSE), gradient echo or 3D spoiled gradient recalled sequences. Echo planar imaging MR images with and without the SiPM-PET inside the MR scanner were significantly worse than the images obtained with the TSE sequence.     

PROPELLER for motion-robust imaging of in vivo mouse abdomen at 9.4 T

In vivo high-field MRI in the abdomen of small animals is technically challenging because of the small voxel sizes, short T(2) and physiological motion. In standard Cartesian sampling, respiratory and gastrointestinal motion can lead to ghosting artefacts. Although respiratory triggering and navigator echoes can either avoid or compensate for motion, they can lead to variable TRs, require invasive intubation and ventilation, or extend TEs. A self-navigated fast spin echo (FSE)-based periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) acquisition was implemented at 9.4 T to enable high-resolution in vivo MRI of mouse abdomen without the use of additional navigators or triggering. T(2)-weighted FSE-PROPELLER data were compared with single-shot FSE and multi-shot FSE data with and without triggering. Single-shot methods, although rapid and robust to motion, demonstrated strong blurring. Multi-shot FSE data showed better resolution, but suffered from marked blurring in the phase-encoding direction and motion in between shots, leading to ghosting artefacts. When respiratory triggering was used, motion artefacts were largely avoided. However, TRs and acquisition times were lengthened by up to approximately 20%. The PROPELLER data showed a 25% and 61% improvement in signal-to-noise ratio and contrast-to-noise ratio, respectively, compared with multi-shot FSE data, together with a 35% reduction in artefact power. A qualitative comparison between acquisition methods using diffusion-weighted imaging was performed. The results were similar, with the exception that respiratory triggering was unable to exclude major motion artefacts as a result of the sensitisation to motion by the diffusion gradients. The PROPELLER data were of consistently higher quality. Considerations specific to the use of PROPELLER at high field are discussed, including the selection of practical blade widths and the effects on contrast, resolution and artefacts.     

A study of artefacts in simultaneous PET and MR imaging using a prototype MR compatible PET scanner.

We have assessed the possibility of artefacts that can arise in attempting to perform simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) using a small prototype MR compatible PET scanner (McPET). In these experiments, we examine MR images for any major artefacts or loss in image quality due to inhomogeneities in the magnetic field, radiofrequency interference or susceptibility effects caused by operation of the PET system inside the MR scanner. In addition, possible artefacts in the PET images caused by the static and time-varying magnetic fields or radiofrequency interference from the MR system were investigated. Biological tissue and a T2-weighted spin echo sequence were used to examine susceptibility artefacts due to components of the McPET scanner (scintillator, optical fibres) situated in the MR field of view. A range of commonly used MR pulse sequences was studied while acquiring PET data to look for possible artefacts in either the PET or MR images. Other than a small loss in signal-to-noise using gradient echo sequences, there was no significant interaction between the two imaging systems. Simultaneous PET and MR imaging of simple phantoms was also carried out in different MR systems with field strengths ranging from 0.2 to 4.7 T. The results of these studies demonstrate that it is possible to acquire PET and MR images simultaneously, without any significant artefacts or loss in image quality, using our prototype MR compatible PET scanner.     

Magnetic resonance imaging of the ovarian cyst: its diagnostic value of endometrial cyst

The role of magnetic resonance imaging (MRI) in diagnosing the ovarian cyst was reviewed with emphasis on its diagnostic value of endometrial cyst. 94 cystic ovarian masses in 77 patients were evaluated using 0.15 Tesla MRI just before laparotomy at Okayama University Hospital from 1984 to 1987 and these images were followed up by histopathological data. From these obtained images, 6 parameters; that is (1) laterality and (2) delineation of the cyst, (3) presence or absence of septal image, and (4) homogeneity, (5) signal intensity and (6) T1 value of the cyst contents, were extracted and analyzed respectively. In 95.5% of endometrial cysts, homogenous internal pattern was observed in all 3 images (short spin echo (SE), inversion recovery (IR) and long SE) and its signal intensity was at the same level or higher than that of myometrium. On the other hand, in all cases of follicular cyst, para-ovarian cyst, corpus luteum cyst and in 95.0% of serous cystadenoma and in 90.9% of mucinous cystadenoma, cyst contents showed either lower signal intensity than the myometrium or similar to it in T1 contrast images (short SE and IR). 93.1% of dermoid cyst showed heterogenous signal intensity in all 3 images and their signal intensity levels were widely ranging. High signal intensity of cyst contents in all 3 images could be observed in 72.7% of endometrial cyst, 5.0% of serous cystadenoma with internal hemorrhage, 9.1% of mucinous cystadenoma with internal hemorrhage and 3.4% of dermoid cyst consisted of fatty tissue only. Endometrial cyst showed markedly shortened T1 value (209.6 +/- 102.7 ms) and the other hemorrhagic cyst showed comparatively short value (360-970 ms). On the other hand, T1 value of non hemorrhagic cyst was as high as the level of urine. All of endometrial cysts were clearly defined from the other pelvic structures. In result, endometrial cysts were found to exhibit the characteristic findings in MRI images such as homogenous high signal intensity of internal fluid and clear delineation of cyst contour. The diagnostic accuracy of MRI in endometrial cyst were considered 96.8% in our cases.     

An algorithm for automatic segmentation and classification of magnetic resonance brain images

In this article, we describe the development and validation of an automatic algorithm to segment brain from extracranial tissues, and to classify intracranial tissues as cerebrospinal fluid (CSF), gray matter (GM), white matter (WM) or pathology. T1 weighted spin echo, dual echo fast spin echo (T2 weighted and proton density (PD) weighted images) and fast Fluid Attenuated Inversion Recovery (FLAIR) magentic resonance (MR) images were acquired ino 100 normal patients and 9 multiple sclerosis (MS) patients. One of the normal studies had synthesized MS-like lesions superimposed. This allowed precise measurement of the accuracy of the classification. The 9 MS patients were imaged twice in one week. The algorithm was applied to these data sets to measure reproducibility. The accuracy was measured based on the synthetic lesion images, where the true voxel class was known. Ninety-six percent of normal intradural tissue voxels (GM, WM, and CSF) were labeled correctly, and 94% of pathological tissues were labeled correctly. A low coefficient of variation (COV) was found (mean, 4.1%) for measurement of brain tissues and pathology when comparing MRI scans on the 9 patients. A totally automatic segmentation algorithm has been described which accurately and reproducibly segments and classifies intradural tissues based on both synthetic and actual images.     

T2-weighted fast spin-echo MR findings of adenocarcinoma of the uterine cervix: comparison with squamous cell carcinoma.

The purpose of this study was to investigate the differences in MR findings of adenocarcinoma (AC) and squamous cell carcinoma (SCC) of the uterine cervix and to compare MR findings with pathologic findings. MR images of 17 patients with pathologically proven AC, using a fast spin-echo (FSE) T2-weighted image (T2WI) with pelvic phased-array coil on a 1.5-T unit, were retrospectively evaluated. After measurement of the signal intensity (SI) ratios of the region of interest between tumors and gluteus maximus muscle, we compared the ratios of AC with those of 16 patients with SCC. AC showed relatively high SI on FSE T2WI with multiseptated lesions in four cases and hydrometrocolpos in three cases. The mean SI ratio was 3.82 +/- 1.68 in AC and 2.35 +/- 0.42 in SCC (p < 0.0001, t-test). Multiple tumorous glands with cytoplasmic and intraglandular mucin or serous fluid were pathologically found in AC, but SCC revealed the compact cellularity of stratified squamous tumor cells. The cervical AC showed higher SI than SCC on FSE T2WI with occasional multiseptated lesions and hydrometrocolpos. If the SI ratio of the tumor was more than 3.0, AC could be diagnosed with a sensitivity of 68.8% and a specificity of 100%.     

High-resolution 8 Tesla imaging of the formalin-fixed normal human hippocampus

The purpose of this study was to evaluate the capacity of high-resolution magnetic resonance imaging (MRI) to visualize the normal anatomic features of the human hippocampus in vitro, using high field imaging equipment, parameters, and acquisition times appropriate for imaging human subjects in vivo. This research compared high field, high-resolution MRI of formalin-fixed normal human hippocampus specimens to histologic sectioning of the same hippocampus samples. Four specimens were evaluated using an 8 Tesla (T), 80 cm bore whole-body MRI scanner equipped with a 12.7 cm single strut transverse electromagnetic resonator (TEM) coil. Hahn spin echo images were acquired with a repetition time (TR) of 800 msec, echo times (TE) of 20, 50, 90, and 134 msec, and an acquisition time (TA) of 3.25 min. The image quality was superb with demonstration of most of the features of the hippocampus. High field, high-resolution MRI can be used to depict multiple layers of the formalin-fixed human hippocampus in vitro using an 8 T whole-body scanner, a TEM coil, and short acquisition times compatible with human imaging in vivo.     

Assessment of cardiac function,blood flow and myocardial tissue relaxation parameters at 0.35 T

A low field strength (B0) system could increase cardiac MRI availability for patients otherwise contraindicated at higher field. Lower equipment costs could also broaden cardiac MR accessibility. The current study investigated the feasibility of cardiac function with steady‐state free precession and flow assessment with phase contrast (PC) cine images at 0.35 T, and evaluated differences in myocardial relaxation times using quantitative T1, T2 and T2* maps by comparison with 1.5 and 3 T results in a small cohort of six healthy volunteers. Signal‐to‐noise ratio (SNR) differences across systems were characterized with proton density‐weighted spin echo phantom data. SNR at 0.35 T was lower by factors of 5.5 and 15.0 compared with the 1.5 and 3 T systems used in this study. All cine images at 0.35 T scored 3 or greater on a five‐point image quality scale. Normalized blood‐myocardium contrast in cine images, left ventricular volumes (end diastolic volume, end systolic volume) and function (ejection fraction and stroke volume) measures at 0.35 T matched 1.5 and 3 T results. Phase‐to‐noise ratio in 0.35 T PC images (11.7 ± 1.9) was lower than 1.5 T (18.7 ± 5.2) and 3 T (44.9 ± 16.5). Peak velocity and stroke volume determined from PC images were similar across systems. Myocardial T1 increased (564 ± 13 ms at 0.35 T, 955 ± 19 ms at 1.5 T and 1200 ± 35 ms at 3 T) while T2 (59 ± 4 ms at 0.35 T, 49 ± 3 ms at 1.5 T and 40 ± 2 ms at 3 T) and T2* (42 ± 8 ms at 0.35 T, 33 ± 6 ms at 1.5 T and 24 ± 3 ms at 3 T) decreased with increasing B0. Despite SNR deficits, cardiovascular function, flow assessment and myocardial relaxation parameter mapping is feasible at 0.35 T using standard cardiovascular imaging sequences.     

胎儿心肺异常MRI诊断

目的探讨MRI在胎儿心肺异常诊断中的应用价值。方法30例孕妇,年龄21～43岁．平均年龄28岁：孕龄16～36周,平均孕龄27周。产前常规行超声（US）检查后24～48h内行MRI检查,采用二维快速平衡稳态采集（2D FIESTA）序列、单次激发快速自旋回波（SSFSE）序列,非门控实时稳态采集序列,行胎儿颅脑胸腹部常规及心肺重点冠状面、矢状面及横断面扫描,将产前MRI、US表现与出生后影像表现或手术（16例胎儿）、引产后尸体解剖结果或尸体影像表现（14例胎儿）对照。结果30例胎儿心肺异常。其中肺部异常20例．心脏异常10例。全部病例产前MRI均诊断正确．产前US漏诊2例、误诊3例。结论MRI在胎儿肺异常诊断方面具有较高的应用价值,能发挥US的补充作用,在心脏畸形诊断方面目前不如US．但能提供一定的信息。MRI联合US能提高胎儿心肺异常的产前诊断准确率。     

Can pre-procedural MRI signal intensity ratio predict the success of uterine artery embolization in treatment of myomas?

Background/aim Magnetic resonance (MR) images, signal intensity ratios calculated using region of interests (ROI) in T2W images by proportioning the dominant myoma to iliac muscle can aid patient selection and, thus, in achieving better outcomes with the uterine artery embolization (UAE) procedure. The present study investigates the association between the success of UAE treatment with signal intensity (SI) ratio of the dominant myoma to the iliac muscle in MR imaging performed prior to the procedure.Materials and methods This is a retrospective study and included 30 patients who admitted to our clinic between February 2017 and July 2019 due to symptoms associated with myoma and who underwent MR imaging before and after UAE treatment. All patients, MR images obtained before UAE treatment and at the 12th month after the procedure were evaluated. In MRI, SI values were calculated by proportioning the dominant myoma to the iliac muscle using circular ROI in T1 weighted (W), T2W, and post-contrast T1W images. In the present study, 50% or more volumetric regression of the myoma with infarction of fibroids (loss of enhancement) at the 12-month follow-up MRI after the procedure was considered a successful procedure. Results Myoma volumes calculated in MR images showed significant differences between the MRI performed before UAE procedure and the MRI performed at the 12th month after the procedure (p < 0.0001). SI ratio calculated from pre-procedure T2W MR images was found to be a significant determinant of 50% or more volumetric regression in the myoma after UAE procedure (p = 0.017), T1W, post-contrast T1W images were not statistically significant (p = 0.211).Conclusion Our results indicate that SI ratio of the dominant myoma to the iliac muscle calculated using ROI in T2W images of MR studies performed before UAE procedure can predict the success of the procedure.