Fast and ultrafast magnetic resonance imaging in renal lesions

Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre-and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.     

An experimental study of the optimal flip angle for hepatocellular magnetic resonance imaging with Gd-EOB-DTPA

Gadoxetate Sodium (Gd-EOB-DTPA) is a relatively new contrast agent used for liver examination by magnetic resonance (MR) imaging. The setting of the flip angle (FA) is very important to obtain images with high contrast in hepatocellular MR imaging. The aim of this study was to determine the optimal FA for hepatocellular MR imaging. Optimal FA was estimated using a visual evaluation by observers. We made the visual evaluation with a paired comparison test. When the overall characteristic showed a significant difference, we then evaluated the optimal FA using a yardstick analysis. The visual evaluation by observers indicated that the FA was best at 22 degrees for the overall characteristic, the contrast characteristic, and the sharpness characteristic, and for the noise characteristic, the best FA was 18 degrees. All characteristics showed a significant difference between 18 and 22 degrees. Based on our results, the most important factor was the contrast characteristic for the visual evaluation, and we concluded that the optimal FA in hepatocelluar MR imaging was 22 degrees.     

磁共振成像技术在产前诊断中的作用

产前磁共振成像检查技术在产前诊断中的作用日益重要。与超声相比，作为一种可选的影像学检查方法，磁共振在对于超声不能够单独作出诊断或对异常分类困难的病例中发挥着越来越重要的作用。当前快速单次激发磁共振序列，如True-FISP或HASTE序列可对活动的胎儿进行高分辨率、高质量的成像。应努力提高我国产前磁共振成像检查的水平。     

实验性自身免疫性脑脊髓炎的MRI研究进展

实验性自身免疫性脑脊髓炎(EAE)是公认的研究人类多发性硬化(MS)的动物模型。MRI能提供大鼠中枢神经系统的高分辨率图像,在活体上动态监测EAE病变的演变过程。随着MR设备及MRI新技术的不断研发及应用,EAE大鼠的MRI研究将更好的诠释EAE病灶的病理生理演变过程,为探索MS病因、发病机制和评估疗效提供了一种重要的研究手段。     

Comparison of three methods for generating group statistical inferences from independent component analysis of functional magnetic resonance imaging data

PURPOSE: To evaluate the relative effectiveness of three previously proposed methods of performing group independent component analysis (ICA) of functional magnetic resonance imaging (fMRI) data. MATERIALS AND METHODS: Data were generated via computer simulation. Components were added to a varying number of subjects between 1 and 20, and intersubject variability was simulated for both the added sources and their associated time courses. Three methods of group ICA analyses were performed: across-subject averaging, subject-wise concatenation, and row-wise concatenation (e.g., across time courses). RESULTS: Concatenating across subjects provided the best overall performance in terms of accurate estimation of the sources and associated time courses. Averaging across subjects provided accurate estimation (R > 0.9) of the time courses when the sources were present in a sufficient fraction (about 15%) of 100 subjects. Concatenating across time courses was shown not to be a feasible method when unique sources were added to the data from each subject, simulating the effects of motion and susceptibility artifacts. CONCLUSION: Subject-wise concatenation should be used when computationally feasible. For studies involving a large number of subjects, across-subject averaging provides an acceptable alternative and reduces the computational load.     

Recent technological and application developments in computed tomography and magnetic resonance imaging for improved pulmonary nodule detection and lung cancer staging

This review compares the emerging technologies and approaches in the application of magnetic resonance (MR) and computed tomography (CT) imaging for the assessment of pulmonary nodules and staging of malignant findings. Included in this review is a brief definition of pulmonary nodules and an introduction to the challenges faced. We have highlighted the current status of both MR and CT for the early detection of lung nodules. Developments are detailed in this review for the management of pulmonary nodules using advanced imaging, including: dynamic imaging studies, dual energy CT, computer aided detection and diagnosis, and imaging assisted nodule biopsy approaches which have improved lung nodule detection and diagnosis rates. Recent advancements linking in vivo imaging to corresponding histological pathology are also highlighted. In vivo imaging plays a pivotal role in the clinical staging of pulmonary nodules through TNM assessment. While CT and positron emission tomography (PET)/CT are currently the most commonly clinically employed modalities for pulmonary nodule staging, studies are presented that highlight the augmentative potential of MR.     

青少年抑郁症的功能磁共振研究进展

近年来功能磁共振成像在成人抑郁症中的研究较为深入,而对于青少年抑郁症的研究则相对有限,故本文就目前功能性磁共振在青少年抑郁症中的研究进展作一综述。     

颞叶癫痫的功能MRI研究进展

颞叶癫■（TLE）是癫■中最常见的难治性类型,临床上对于药物难以控制的癫■,手术切除致■灶具有良好的治疗效果。随着MRI技术的迅速发展,功能磁共振成像（fMRI）在癫■研究中的优势越来越显著,尤其在癫■灶的定侧、定位方面明显优于常规MRI,具有更好的临床应用价值。fMRI对TLE脑网络、认知功能的研究,及在TLE病因、病理生理机制、治疗预后等方面的应用取得了诸多进展。     

T1rho contrast in functional magnetic resonance imaging.

The application of T1 in the rotating frame (T1rho) to functional MRI in humans was studied at 3 T. Increases in neural activity increased parenchymal T1rho. Modeling suggested that cerebral blood volume mediated this increase. A pulse sequence named spin-locked echo planar imaging (SLEPI) that produces both T1rho and T2* contrast was developed and used in a visual functional MRI (fMRI)experiment. Spin-locked contrast significantly augments the T2* blood oxygen level-dependent (BOLD) contrast in this sequence. The total functional contrast generated by the SLEPI sequence (1.31%) was 54% larger than the contrast (0.85%) obtained from a conventional gradient-echo EPI sequence using echo times of 30 ms. Analysis of image SNR revealed that the spin-locked preparation period of the sequence produced negligible signal loss from static dephasing effects. The SLEPI sequence appears to be an attractive alternative to conventional BOLD fMRI, particularly when long echo times are undesirable, such as when studying prefrontal cortex or ventral regions, where static susceptibility gradients often degrade T2*-weighted images.     

宫颈癌功能磁共振成像研究进展

宫颈癌是女性生殖系统最常见的恶性肿瘤,早期诊断和治疗是防治的关键。MR成像尤其是功能MR成像技术在宫颈癌的早期诊断、生物学评价、疗效和预后评估等方面具有明显的优势。综述宫颈癌的功能MRI研究进展,重点分析各种功能成像技术的临床应用价值及其不足,以期为临床工作中根据具体情况和技术条件选择和组合多种功能MRI技术提供有益提示,从而提高宫颈癌的诊断准确率。     

功能磁共振成像在多发性硬化认知功能障碍中的研究进展

多发性硬化(multiple sclerosis,MS)是中枢神经系统中以多灶性血管周围炎性细胞浸润、白质脱髓鞘为特征的自身免疫性疾病.认知障碍(cognitive impairment,CI)是MS病情过程中重要的临床表现之一,发生率高,约为40%~65%[1],严重影响患者的生活质量.     

Venous refocusing for volume estimation: VERVE functional magnetic resonance imaging.

A novel, noninvasive magnetic resonance imaging-based method for measuring changes in venous cerebral blood volume (CBV(v)) is presented. Venous refocusing for volume estimation (VERVE) exploits the dependency of the spin-spin relaxation rate of deoxygenated blood on the refocusing interval. Interleaved CPMG EPI acquisitions following a train of either tightly or sparsely spaced hard refocusing pulses (every 3.7 or 30 msec, respectively) at matched echo time were used to isolate the blood signal while minimizing the intravascular blood oxygenation level dependent (BOLD) signal contribution. The technique was employed to determine the steady-state increase in the CBV(v) in the visual cortex (VC) in seven healthy adult volunteers during flickering checkerboard photic stimulation. A functional activation model and a set of previously collected in vitro human whole blood relaxometry data were used to evaluate the intravascular BOLD effect on the VERVE signal. The average VC venous blood volume change was estimated to be 16 +/- 2%. This method has the potential to provide efficient and continuous monitoring of venous cerebral blood volume, thereby enabling further exploration of the mechanism underlying BOLD signal changes upon physiologic, pathophysiologic, and pharmacologic perturbations.     

正常人丘脑及岛盖功能连接的MRI研究

目的:探讨正常人在静息和认知任务状态下丘脑及岛盖功能连接的变化情况。方法:采用BOLD-fMRI方法,检测16例健康志愿者在静息和2-back任务状态下的脑功能连接,将前额叶内侧皮层作为种子点,应用SPM2、AFNI及Matlab软件进行图像数据处理,对2-back任务和静息状态行组内和组间2个水平的统计分析,统计阈值概率设定为P=0.005(未校正)。结果:与左侧丘脑前核相关的网络系统与默认网络一致,而丘脑背侧部属"任务正激活网络",且受试者反应正确率与左侧丘脑背侧的相关性差异有统计学意义(r=-0.52,P=0.04)。"岛盖相关网络"与"默认网络"呈负相关,前者在静息状态相关性高于任务状态,其主要脑区包括双岛叶、双顶下小叶、双中央旁小叶、双颞上回、双海马旁回等。结论:人脑在静息和任务状态下脑区间的功能连接不同,表现为丘脑前核和丘脑背侧部的功能分化,及"岛盖相关网络"与"默认网络"在静息状态的功能拮抗。     

fMRI评价移植肾功能异常的研究进展

肾移植术后及时准确地评价移植肾功能受损至关重要,并发症的早期准确鉴别有助于及时干预及治疗,从而进一步提高移植肾的长期存活率。目前多种扩散成像、血氧水平依赖成像（BOLD）、动脉自旋标记（ASL）等功能MRI技术已用于评价移植肾功能,可以从肾脏水分子扩散、血氧水平及血流灌注微观角度等方面对肾功能进行评估。就多种功能MRI技术对移植肾功能的评价、肾移植术后并发症的鉴别作一综述,为临床诊断及治疗提供依据及思路。     

脑功能MRI在青少年非自杀性自伤中的研究进展

非自杀性自伤（NSSI）是指没有自杀意图且以自伤行为为主的精神障碍,脑功能MRI（fMRI）可揭示NSSI病人的异常脑活动特征。静息态fMRI的不同功能连接模式对NSSI的诊断和疗效评估具有重要价值,基于不同任务状态的fMRI的异常脑激活可评估NSSI病人的脑功能改变。就不同分析方法（基于种子点、独立成分分析和图论的分析方法）的静息态fMRI连接模式和不同任务状态（情绪、社交和奖赏任务）下fMRI的脑活动在NSSI中的研究进展予以综述。     

Evaluation of motion and realignment for functional magnetic resonance imaging in real time.

Functional magnetic resonance imaging in real time is an emerging tool for the assessment of dynamic changes in brain activation. The short response latency (tens of seconds) renders the technique more sensitive to motion artifacts. Motion correction in real time requires computationally efficient algorithms which can be executed on a complete 3D data set within a single time of repetition cycle. In this study, a method to evaluate motion and realign functional images in real time implemented on standard imaging hardware is introduced. The detection of activity in correlation maps is improved, and artifactual edge enhancements are reduced. As the estimation of large movements is stable, this algorithm is attractive for clinical studies with uncooperative patients. Magn Reson Med 45:167-171, 2001.     

Multimodal morphometry and functional magnetic resonance imaging in schizophrenia and auditory hallucinations

AIM:To validate a multimodal[structural and functional magnetic resonance(MR)]approach as coincidence brain clusters are hypothesized to correlate with clinical severity of auditory hallucinations.METHODS:Twenty-two patients meeting Diagnostic and Statistical Manual of Mental Disorders(fourth edition,DSM-Ⅳ)criteria for schizophrenia and experiencing persistent hallucinations together with 28 healthy controls were evaluated with structural and functional MR imaging with an auditory paradigm designed to replicate those emotions related to the patients’hallucinatory experiences.Coincidence maps were obtained by combining structural maps of gray matter reduction with emotional functional increased activation.Abnormal areas were correlated with the brief psychiatric rating scale(BPRS)and the psychotic symptom rating scale(PSYRATS)scales.RESULTS:The coincidence analysis showed areas with coexistence gray matter reductions and emotional activation in bilateral middle temporal and superior temporal gyri.Significant negative correlations between BPRS and PSYRATS scales were observed.BPRS scores were negatively correlated in the middle temporal gyrus(right)(t=6.86,P=0.001),while negative PSYRATS correlation affected regions in both the superior temporal gyrus(left)(t=7.85,P=0.001)and middle temporal gyrus(left)(t=4.97,P=0.002).CONCLUSION:Our data identify left superior and middle temporal gyri as relevant areas for the understanding of auditory hallucinations in schizophrenia.The use of multimodal approaches,sharing structural and functional information,may demonstrate areas specifically linked to the severity of auditory hallucinations.     

Bicuculline-induced brain activation in mice detected by functional magnetic resonance imaging.

Dynamic measurements of local changes in relative cerebral blood volume (CBV(rel)) during a pharmacological stimulation paradigm were performed in mice. Using magnetite nanoparticles as an intravascular contrast agent, high-resolution CBV(rel) maps were obtained. Intravenous administration of the GABA(A) antagonist bicuculline prompted increases in local CBV(rel) as assessed by MRI with a high spatial resolution of 0.2 x 0.2 mm(2) and a temporal resolution of 21 s. Signal changes occurred 20-30 s after the onset of drug infusion in the somatosensory and motor cortex, followed by other cortical and subcortical structures. The magnitudes of the CBV(rel) increases were 18% +/- 4%, 46% +/- 14%, and 67% +/- 7%, as compared to prestimulation values for the cortex, and 9% +/- 3%, 25% +/- 4%, and 36% +/- 7% for the caudate putamen for bicuculline doses of 0.6, 1.25, and 1.5 mg/kg, respectively. On-line monitoring of transcutaneous carbon dioxide tension PtcCO(2) reflecting arterial PaCO(2) did not show any alteration during the stimulation paradigm. One of five of the mice receiving the highest bicuculline dose, and three of seven receiving the intermediate dose displayed a different cortical response pattern. After a CBV(rel) increase of 40% lasting for approximately 1 min, significant CBV(rel)reductions by 80% have been observed. Subcortical structures did not display this behavior. The present study suggests that this noninvasive approach of functional MRI (fMRI) can be applied to study drug-induced brain activation by central nervous system (CNS) drugs in mice under normal and pathological situations.