肝退变结节的病理学改变及CT、MRI表现

肝细胞肝癌及胆管细胞癌均可在退变结节的基础上发展形成，因此及早、准确的诊断肝退变结节具有积极的临床意义。本文通过分析肝退变结节的CT、MRI表现及病理学改变，以期提高对肝退变结节的诊断水平。     

Measurement of xenon diffusing capacity in the rat lung by hyperpolarized 129Xe MRI and dynamic spectroscopy in a single breath-hold.

We used the dual capability of hyperpolarized 129Xe for spectroscopy and imaging to develop new measures of xenon diffusing capacity in the rat lung that (analogously to the diffusing capacity of carbon monoxide or DLCO) are calculated as a product of total lung volume and gas transfer rate constants divided by the pressure gradient. Under conditions of known constant pressure breath-hold, the volume is measured by hyperpolarized 129Xe MRI, and the transfer rate is measured by dynamic spectroscopy. The new quantities (xenon diffusing capacity in lung parenchyma (DLXeLP)), xenon diffusing capacity in RBCs (DLXeRBC), and total lung xenon diffusing capacity (DLXe)) were measured in six normal rats and six rats with lung inflammation induced by instillation of fungal spores of Stachybotrys chartarum. DLXeLP, DLXeRBC, and DLXe were 56 +/- 10 ml/min/mmHg, 64 +/- 35 ml/min/mmHg, and 29 +/- 9 ml/min/mmHg, respectively, for normal rats, and 27 +/- 9 ml/min/mmHg, 42 +/- 27 ml/min/mmHg, and 16 +/- 7 ml/min/mmHg, respectively, for diseased rats. Lung volumes and gas transfer times for LP (TtrLP) were 16 +/- 2 ml and 22 +/- 3 ms, respectively, for normal rats and 12 +/- 2 ml and 35 +/- 8 ms, respectively, for diseased rats. Xenon diffusing capacities may be useful for measuring changes in gas exchange associated with inflammation and other lung diseases.     

Continuously moving table 3D MRI with lateral frequency-encoding direction.

A method is presented for 3D MRI in an extended field of view (FOV) based on continuous motion of the patient table and an efficient acquisition scheme. A gradient-echo MR pulse sequence is applied with lateral (left-right (L/R)) frequency-encoding direction and slab selection along the direction of motion. Compensation for the table motion is achieved by a combination of slab tracking and data alignment in hybrid space. The method allows fast k-space coverage to be achieved, especially when a short sampling FOV is chosen along the direction of table motion, as is desirable for good image quality. The method can be incorporated into different acquisitions schemes, including segmented k-space scanning, which allows for contrast variation with the use of magnetization preparation. Head-to-toe images of volunteers were obtained with good quality using 3D spoiled gradient-echo sequences. As an example of magnetization-prepared imaging, fat/water separated images were acquired using chemical shift selective (CHESS) presaturation pulses.     

MR评价垂体腺瘤质地及与其胶原含量的关系

目的利用MR测量垂体腺瘤不同质地的信号强度,并分析其与肿瘤胶原含量间的关系。方法57例经手术证实的垂体腺瘤标本,术前均行MR检查,根据术中肿瘤硬度分为质地韧组(8例)与质地软组(49例),标本行天狼猩红染色检测其胶原含量。结果纤维化与非纤维化组T1WI瘤体/灰质信号强度比分别为1.31±0.31、1.16±0.26;T1WI瘤体/白质信号强度比分别为1.01±0.25、0.91±0.18,两组间差异无统计学意义(P(0.05);T1+WI瘤体/灰质信号强度比分别为1.83±0.28、1.84±0.51;T1+WI瘤体/白质信号强度比分别为1.56±0.24、1.46±0.37,两组间差异无统计学意义(P(0.05);T2WI瘤体/灰质信号强度比分别为1.15±0.26、1.57±0.46(P(0.05);T2WI瘤体/白质信号强度比分别为1.48±0.39、2.10±0.61,两组间有统计学意义(P(0.01);胶原含量分别为20.03%±7.99%、7.87%±4.82%,两组间有统计学意义(P<0.01);且T2WI瘤体/灰质、T2WI瘤体/白质与胶原含量呈显著负相关(r=-0.531、r=-0.726,P均(0.01)。结论术前MR可以预测垂体腺瘤的质地;其中以T2WI瘤体/白质为预测指标为最佳。胶原含量影响垂体腺瘤质地,MRI上T2WI可以反映其胶原含量的多少。     

脊椎转移瘤增强减影MR成像

目的评估增强减影在脊椎转移瘤MR I中的应用价值。方法50例脊椎转移瘤病人进行MR I增强扫描,对比剂采用Gd-DTPA(0.1 mmol/kg),然后用T1W I增强后的图像与增强前的图像进行减影。通过对比噪声比(CNR)、信噪比(SNR)以及肿瘤边界清晰程度的比较,对MR I减影与否进行评估。结果MR I对比增强减影图像比传统的T1W I增强图像显示更清晰、更直观。所有脊椎转移瘤图像MR I减影的CNR和SNR比常规T1W I增强图像的CNR和SNR高。MR I减影CNR为155.05±24.73(x±SD),常规T1W I增强图像的CNR为11.11±14.26(t=35.65,Ρ<0.001)。MR I减影SNR为192.82±32.89(x±SD),常规T1W I增强图像的SNR为46.03±28.22(t=23.95,Ρ<0.001))。MR I对比增强减影图像比传统的T1W I增强图像能更好地显示脊椎转移瘤的边界和侵犯情况(2χ=29.34,Ρ<0.005)。结论MR I增强减影为探查和评估脊椎转移瘤提供了一个新的诊断方法。     

Turboprop: improved PROPELLER imaging.

A variant of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) MRI, called turboprop, is introduced. This method employs an oscillating readout gradient during each spin echo of the echo train to collect more lines of data per echo train, which reduces the minimum scan time, motion-related artifact, and specific absorption rate (SAR) while increasing sampling efficiency. It can be applied to conventional fast spin-echo (FSE) imaging; however, this article emphasizes its application in diffusion-weighted imaging (DWI). The method is described and compared with conventional PROPELLER imaging, and clinical images collected with this PROPELLER variant are shown.     

急性一氧化碳中毒后迟发性脑病的临床表现和影像学特点

目的探讨急性一氧化碳中毒后迟发性脑病的临床表现和影像学特点及其诊断价值。方法回顾性对23例急性一氧化碳中毒后迟发性脑病的临床表现和影像学特点进行归纳和分析。结果23例患者中智能障碍23例（100％），言语功能障碍17例（73.9％），另有共济失调精神障碍帕金森综合症及尿失禁等。头部CT和MRI主要表现为皮层下脑白质异常信号及基底节区或苍白球区异常信号，极少累及大脑皮质脑干和小脑。结论急性一氧化碳中毒后迟发性脑病的诊断主要依靠病史和临床症状，MRI比CT更有诊断价值。     

Hematoma Size in Deep Intracerebral Hemorrhage and its Correlation with Dot-Like Hemosiderin Spots on Gradient Echo T2*-Weighted MRI

BACKGROUND AND PURPOSE: Dot-like low intensity spots (dot-like hemosiderin spots: dotHSs) on gradient echo T2*-weighted MRI have been histologically diagnosed to represent old cerebral microbleeds associated with microangiopathies. They have also been correlated to the fragility of small vessels and the tendency to bleed. Therefore, a substantial number of dotHSs might be associated with a large-sized, deep intracerebral hematoma (ICH). On the other hand, dotHSs may reflect old microbleeds that did not enlarge to symptomatic size. METHODS: To investigate how dotHSs are related to the size (maximal diameter) of primary deep ICH, we analyzed the diameter and the number of dotHSs in 151 patients with deep ICH not associated with subarachnoid hemorrhage or intraventricular hemorrhage (75 males and 76 females, age ranged from 37 to 90 [65.7 +/- 11.3 years old] who were consecutively admitted to Hakodate Municipal Hospital. The hazard ratio (HR) for a maximal diameter of deep ICH < or =2 cm was estimated, using the number of dotHSs and risk factors for stroke. RESULTS: The number of dotHSs associated with the diameter < or =2 cm was 9.2 +/- 11.5, significantly larger than that with the diameter > or =2 cm (4.7 +/- 7.0, P= .012). Multivariate analysis revealed that a maximal diameter of deep ICH of < or =2 cm was found in patients with dotHS (HR, 3.7; 95% confidence interval [CI], 1.4-10.1; P= .009). CONCLUSION: Though small sample size limited the power of our analyses, these findings suggest that the number of dotHSs may be associated with a small diameter of deep ICH.     

腰椎终板、椎间盘退变及椎间盘造影疼痛激发试验的相关性研究

目的探讨下腰痛患者腰椎终板Modic退变、椎间盘退变及CT引导下腰椎间盘造影疼痛激发试验的相关性.方法对45例下腰痛患者常规行腰椎X线和MR检查,分别按Modic终板退变标准（0～3级）与Pearce椎间盘退变标准（Ⅰ～Ⅴ级）对终板和椎间盘进行评估.在CT引导下对45例患者中的40例（120个椎间盘）进行造影和疼痛激发试验,并按Dallas椎间盘造影分级系统（DDD）测评椎间盘退变程度.采用SPSS 11.5统计学软件分析腰椎终板Modic退变、椎间盘退变与腰椎间盘造影疼痛激发试验之间的相关性.结果40例下腰痛患者的腰椎终板Modic分级与椎间盘退变Pearce分级存在较强的相关性（Pearson x^2=43.326,P=0.000）,与椎间盘造影疼痛激发试验有显著相关性（Pearson x^2=27.858,P=0.000）;椎间盘退变Pearce分级与CT椎间盘造影椎间盘退变Dallas分级也呈较强的相关性.结论腰椎终板Modic退变分级与椎间盘退变Pearce分级密切相关,而与椎间盘疼痛激发试验有显著相关性,提示终板Modic退变可能是下腰痛的原因之一.     

Longitudinal gradient coil optimization in the presence of transient eddy currents.

The switching of magnetic field gradient coils in magnetic resonance imaging (MRI) inevitably induces transient eddy currents in conducting system components, such as the cryostat vessel. These secondary currents degrade the spatial and temporal performance of the gradient coils, and compensation methods are commonly employed to correct for these distortions. This theoretical study shows that by incorporating the eddy currents into the coil optimization process, it is possible to modify a gradient coil design so that the fields created by the coil and the eddy currents combine together to generate a spatially homogeneous gradient that follows the input pulse. Shielded and unshielded longitudinal gradient coils are used to exemplify this novel approach. To assist in the evaluation of transient eddy currents induced within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using the total-field scattered-field (TFSF) scheme was performed. The simulations demonstrate the effectiveness of the proposed method for optimizing longitudinal gradient fields while taking into account the spatial and temporal behavior of the eddy currents.