MR urography today

Magnetic resonance (MR) urography is performed by pursuing two different imaging strategies. On the one hand, heavily T2-weighted turbo spin-echo sequences are employed for obtaining unenhanced static-water images of the urinary tract. On the other, the T(1)-weighted MR urographic technique imitates conventional intravenous pyelography and is, therefore, referred to as excretory MR urography. For this reason, a gadolinium contrast agent is injected intravenously and, after its renal excretion, the gadolinium-enhanced urine is imaged with fast T1-weighted gradient-echo sequences. Both MR urographic techniques can be combined for a comprehensive examination of the upper urinary tract. This article reviews the current technical principles, imaging capabilities, and clinical applications of T2- and T1-weighted MR urography in adult and pediatric patients.     

宫颈癌MRI分期与病理对照研究

目的 探讨宫颈癌磁共振成像(MRI)分期与病理分期的相关性.方法 80例经手术或活检病理证实的宫颈癌患者行盆腔MRI检查,MRI的成像序列包括T1加权像、T2加权像、脂肪抑制T2加权像、弥散加权成像,以及钆喷酸葡胺增强T1加权像.观察肿瘤的位置、信号特征及侵犯范围.将MRI所见与病理结果相对比.结果 MRI对宫颈癌分期总的准确率为88.73%.对宫旁侵犯判断的准确率为92.50%,特异度为91.18%,敏感度为100%.MRI与病理诊断的差异主要与宫旁浸润的评价差异有关.结论 MRI在宫颈癌临床分期中具有很高的准确性,是宫颈癌诊断中重要的影像学手段.     

Optimization of a contrast medium suitable for conventional enteroclysis,MR enteroclysis,and virtual MR enteroscopy

BACKGROUND: The purpose of the current study was to optimize a gadolinium-barium sulfate solution suitable for performing conventional and MR enteroclysis examinations in the same session. METHODS: Eighteen vials of 20% barium sulfate and various gadolinium concentrations (lower 0 ml/lt, higher 45 ml/lt) were prepared and placed in the magnet. The imaging protocol was consisted of the following sequences: true FISP, HASTE with fat saturation and 3d FLASH with fat saturation in various flip angles. Ten patients underwent conventional enteroclysis with 1.2 lt of 20% barium sulfate enema and 18 ml of gadolinium. MR enteroclysis was performed afterwards using true FISP, fat suppressed 3d FLASH and fat suppressed HASTE sequences. RESULTS: The lowest gadolinium concentration in the barium sulfate solution generating low intraluminal signal on HASTE and high intraluminal signal on true FISP and 3d FLASH sequences was 15 ml/lt. The presence of gadolinium did not influence the lumen opacification in conventional enteroclysis examination. In all patients the proposed contrast medium acted as positive in 3d FLASH (T1w), true FISP (T2/T1 w) and as a negative in HASTE (T2w). Bowel wall conspicuity, lumen opacification and distention were ranked as very good to excellent on MR enteroclysis images while artifacts level did not downgraded the overall image quality. High quality virtual MR endoluminal views of the small bowel, based on 3d FLASH images, were obtained in all cases. CONCLUSION: A 20% barium sulfate enema with 15 ml/lt gadolinium is appropriate for conventional and MR enteroclysis examinations.     

Magnetic resonance imaging of the postoperative hip

Magnetic resonance imaging (MRI) of the postoperative hip for delineation of various pathological conditions has been established in addition to conventional radiography and computed tomography. MRI provides superior soft-tissue contrast than the other imaging modalities, and it can be used for visualization of structures and pathological entities that cannot be depicted by conventional radiography and computed tomography. These entities include bone marrow changes such as bone marrow edema and avascular necrosis, and infiltration of the bone marrow by tumor recurrence or infections after insertion of metallic osteosynthetic material. The image quality of MRI, which is reduced as result of artifacts caused by metal alloys, can be optimized by using spin-echo or fast spin-echo sequences, and by adapting phase- and frequency-encoding directions in cases where metallic osteosynthetic materials were used. MRI, in addition to computed tomography and conventional radiography, appears to be a valuable tool for imaging the different pathological conditions of the postoperative hip, including after implantation of metallic osteosynthetic material.     

胰岛细胞瘤的影像学表现（附10例分析）

目的胰岛细胞瘤较少见，目前对胰岛细胞瘤的CT表现报道较多，MRI表现报道较少。本研究分析胰岛细胞瘤的CT及MRI表现，着重探讨MRI的诊断价值。方法回顾性分析经手术病理证实的10例胰岛细胞瘤的CT及MRI表现。结果10例胰岛细胞瘤中，8例为功能性胰岛细胞瘤，2例为无功能性胰岛细胞瘤，其中4例为恶性。胰岛素瘤普通CT多表现为等密度，轻度强化，较易漏诊。MRI多表现为T1WI低信号，T2WI高信号，常规增强后轻度强化，动态MRI增强早期可明显强化。功能性胰岛细胞瘤体积多较小，无功能性或恶性胰岛细胞瘤体积多较大。恶性胰岛细胞瘤多伴肝脏或淋巴结转移。结论胰岛细胞瘤的影像学表现具有一定的特征性，MRI较常规CT能提供更多的诊断信息．尤其是动态增强MRI。     

肝脏及上腹部MRI扫描序列的应用价值

目的通过对六种扫描序列的分析与评价以期达到发现中低场强中最有价值的扫描序列及序列组合的目的.方法对26名临床怀疑肝脏病变的患者进行了MR检查,均应用了快速自旋回波(TSE)的T2加权像,快速梯度回波(TFE)的反相位T1加权像,快速自旋回波加脂肪抑制的T2加权像,标准自旋回波(SE)的T1和T2加权像,快速梯度回波(TFE)的动态增强扫描等六种扫描序列,对各序列的图像质量及腹部常见正常结构的显示进行了分析和评价.结果快速自旋回波(TSE)T2加权像图像质量最好,24/26例(92%)选择了这一扫描序列,其次为标准自旋回波(SE)的T1加权像,6/26例选择了这一扫描序列.图像质量最差的序列为标准自旋回波(SE)T2加权像(24/24,100%).其他三种扫描序列的图像质量则介于上述三种序列之间.经统计学分析TSE的T2加权像与其他五种扫描序列在图像质量上均存在显著差异(P＜0.005).结论腹部病变常规应做标准自旋回波T1加权像,快速自旋回波T2加权像,快速自旋回波加脂肪抑制和梯度回波反相位这四种序列,病变鉴别有困难时则可加做标准自旋回波的多回波序列和快速梯度回波的动态增强扫描序列.     

克-亚二氏综合征的MR表现

目的描述克-亚二氏综合征的脑部MRI表现,探讨MRI对该病的诊断价值。方法经病理证实的克-亚二氏综合征4例,回顾性分析其MRI和扩散加权像(DWI)表现,并复习相关临床及文献资料。结果1例表现为双侧脑室旁深部白质区及内囊后肢皮质脊髓束走行区稍长T1、稍长T2信号;2例T2WI及DWI上表现为双侧尾状核和壳核区对称性稍高信号影和部分皮质带状异常高信号;1例T2WI及DWI上表现为部分皮质带状异常高信号,伴脑萎缩。结论克-亚二氏综合征的脑部MRI表现有比较典型的特点,MRI是诊断该病的重要手段。     

In vivo magnetic resonance imaging of embryonic neural grafts in a rat model of striatonigral degeneration (multiple system atrophy)

The effects of embryonic neural transplantation in experimental models of neurodegenerative disorders are commonly assessed by behavioral tests and postmortem neurochemical or anatomical analysis. The purpose of the present study was to evaluate embryonic neuronal grafts in a novel rat model of multiple system atrophy (MSA) with the help of in vivo magnetic resonance imaging (MRI) and to correlate imaging with histological parameters. Striatonigral double lesions were created in male Wistar rats by unilateral intrastriatal injection of 3-nitropropionic acid (3-NP). Seven weeks following lesion surgery animals were divided into four transplantation groups receiving either pure mesencephalic, pure striatal, mesencephalic-striatal cografts, or sham grafts. In vivo structural imaging was performed 21 weeks after transplantation using a whole body 1.5 Tesla MR scanner. The imaging protocol comprised T2-weighted TSE and T1-weighted TIR sequences. Immunohistochemistry using DARPP-32 as striatal marker and tyrosinhydroxylase as marker for nigral neurons was performed for correlation analysis of imaging and histological parameters. The sensitivity of graft detection by in vivo MRI was 100%. The graft tissue was clearly demarcated from the remaining striatal tissue in both T2- and T1-weighted sequences. Morphometrically, cross-sectional areas of the grafts and spared intact striatum as defined by immunohistochemistry correlated significantly with measurements obtained by in vivo MRI. In conclusion, we were able to evaluate in vivo both lesion-induced damage and graft size in a 3-NP rat model of MSA using a conventional whole body 1.5 Tesla MRI scanner. Additionally, we obtained an excellent correlation between MRI and histological measurements.     

磁共振扩散张量成像对脊髓型颈椎病脊髓慢性损伤的评价

目的 评价磁共振扩散张量成像（DTI）对脊髓型颈椎病脊髓慢性损伤早期诊断的可行性。方法 采用单次激发平面回波成像（SE-EPI）序列对31例临床确诊的脊髓型颈椎病患者行颈髓常规MRI和DTI检查。测量病变处ADC值和FA值并按病变常规T2WI高信号阳性与阴性分组进行数据分析,计算常规MRI和DTI对颈髓病变检出的敏感度、特异度、阳性预测值（PPV）、阴性预测值（NPV）。结果所有脊髓型颈椎病患者均能完成DTI检查,后处理图像颈髓显示清晰,无明显图像变形及伪影。9例（29%）表现为颈髓病变T2WI高信号的患者均出现颈髓受压平面ADC值升高,FA值下降,平均ADC值为（1183.44±121.96）×10-6mm2/s,相应FA值为（432.56±59.97）×10-3,与正常值相比有统计学意义;22例（71%）颈髓病变T2WI高信号阴性患者中,7例（32%）病变处平均ADC值及FA较正常值无明显变化;15例（68%）颈髓受压平面ADC值升高,FA值下降,平均ADC值（1055.07±80.61）×10-6mm2/s,FA值为（501.87±41.09）×10-3,有统计学意义。检查方法的敏感度常规T2WI为29.0%,DTI为67.7%;特异度常规T2WI为71.0%,DTI为22.6%;PPV常规T2WI为27.3%,DTI为72.7%;NPV常规T2WI为75.9%,DTI为24.1%。结论 DTI较常规MRI更早期而准确地诊断脊髓型颈椎病颈髓慢性损伤,是一种显示脊髓型颈椎病颈髓病变和观察病变修复过程的有效手段。     

Focal nodular hyperplasia of the liver: detection and characterization with plain and dynamic-enhanced MRI

Background: We compared nonenhanced and dynamic gadolinium (Gd)–enhanced magnetic resonance imaging (MRI) appearances of hepatic focal nodular hyperplasia (FNH) as depicted with breath-hold MR sequences and assessed the detectability of the individual MR sequences used. Methods: We retrospectively reviewed 48 consecutive patients with FNH. All patients underwent nonenhanced (T1 fast low-angle shot [FLASH] and T2 half-Fourier acquisition [HASTE]) and dynamic Gd-enhanced (T1 FLASH) MRI between December 1997 and March 2000. Individual MR sequences were analyzed separately for number of lesions, signal intensity features, dynamic enhancement pattern, and the presence and enhancement profile of a central scar. Ninety-five percent confidence intervals of absolute discrepancy were calculated to define differences in lesion detection. Results: Seventy-seven lesions were found in 48 patients. Nonenhanced FLASH imaging depicted 59 (76.6%) lesions in 45 patients. HASTE images showed 55 (71.4%) lesions in 44 patients. On T1- and T2-weighted images, lesions appeared predominantly hypointense (69.5%) and hyperintense (72.7%), respectively. Arterial and portal venous dominant phase Gd-enhanced MRI demonstrated all 77 lesions (100%), most of which showed hypervascular (94.8%), homogeneous (97.4%), and incomplete (except the central scar: 58.4%) enhancement in the arterial phase. Portal venous phase images showed lesion isointensity (50.6%) or moderate hyperintensity (46.8%) with complete enhancement (central scar: 94.8%). A central scar was detected on nonenhanced T1-weighted images (hypointense: 100%), T2-weighted images (hyperintense: 100%), arterial phase (hypointense: 59.7%) and portal venous phase (hyperintense: 71.4%) Gd-enhanced images in 78%, 69.1%, 77.9%, and 75.3% of tumors, respectively. Conclusion: Arterial and portal venous phase Gd-enhanced T1-weighted sequences are superior to nonenhanced images in the detection of FNH. Typical MRI appearances include hypointensity on T1-weighted and hyperintensity on nonenhanced T2-weighted images. Most commonly, FNH shows a homogeneous (without scar) and strong enhancement during the arterial phase, with lesion isointensity or slight hyperintensity during the portal venous phase. Received: 15 May 2001/Revision accepted: 22 August 2001     

磁共振增强减影技术在结核性脑膜炎中的运用

目的评价磁共振增强减影方法在结核性脑膜炎中的应用价值。方法对30例结核性脑膜炎患者进行磁共振检查，对增强前后T1加权图像行减影处理。在不同的解剖层面，随机选取120处异常强化柔脑膜在常规增强T1加权和减影图像中分另Ⅱ进行长度及相对信号强度测量，所获数据用统计软件进行分析，评价并比较异常强化柔脑膜在减影图像与常规增强T1WI中的显示。结果磁共振减影图像比常规增强T1Wi显示异常强化柔脑膜更清晰、直观。减影图像显示异常强化柔脑膜多呈连续状，而常规增强T1加权图像大多呈断片状，2种成像方法显示异常强化柔脑膜的长度有显著性差异（P〈0．01）。减影图像中异常强化柔脑膜信号强度相对比值明显高于常规增强T1W1，其差异有极显著性意义（P〈0．01）。结论磁共振增强减影技术是一种能明显提高结脑异常强化柔脑膜显示率的简便方法，可为临床早期诊断结脑提供一个全新的诊断工具。     

儿童小肠MR成像临床应用评价

目的分析儿童小肠病变MRI表现,评价小肠MR成像在儿科中的临床应用价值。方法对12例经手术和病理证实的小肠病变患儿进行回顾性分析,检查前让患儿口服2.5%的等渗甘露醇溶液后,静脉注射山莨菪碱0.3mg/kg,随后行MR扫描,扫描方法包括冠状面真稳态进动快速成像(TrueFisp)序列,横断面及冠状面T1WI、T2WI脂肪抑制序列、vibe超薄容积扫描(压脂)序列,然后行带脂肪饱和技术的T1WI横断面及冠状面增强扫描。结果 12例患儿均能接受等渗甘露醇溶液,未发现并发症,其中Crohn病6例,共显示16段炎症肠管,MRI表现为增强后病变肠壁强化明显,病变肠段肠壁增厚(厚度为5～14mm),且多表现环形增厚,肠壁厚薄不均,肠腔变窄。十二指肠球部慢性溃疡、十二指肠球部穿孔、胃肠吻合口溃疡、小肠梗阻(柿石症)、小肠淋巴瘤、肠套叠各1例。小肠MR成像不仅显示了病变本身,还显示了肠壁、肠外血管及肠系膜脂肪的情况。结论小肠MR成像安全、有效、无创、无电离辐射,能全方位多维显示儿童小肠疾病的方法。     

2D probabilistic undersampling pattern optimization for MR image reconstruction

With 3D magnetic resonance imaging (MRI), a tradeoff exists between higher image quality and shorter scan time. One way to solve this problem is to reconstruct high-quality MRI images from undersampled k-space. There have been many recent studies exploring effective k-space undersampling patterns and designing MRI reconstruction methods from undersampled k-space, which are two necessary steps. Most studies separately considered these two steps, although in theory, their performance is dependent on each other. In this study, we propose a joint optimization model, trained end-to-end, to simultaneously optimize the undersampling pattern in the Fourier domain and the reconstruction model in the image domain. A 2D probabilistic undersampling layer was designed to optimize the undersampling pattern and probability distribution in a differentiable manner. A 2D inverse Fourier transform layer was implemented to connect the Fourier domain and the image domain during the forward and back propagation. Finally, we discovered an optimized relationship between the probability distribution of the undersampling pattern and its corresponding sampling rate. Further testing was performed using 3D T1-weighted MR images of the brain from the MICCAI 2013 Grand Challenge on Multi-Atlas Labeling dataset and locally acquired brain 3D T1-weighted MR images of healthy volunteers and contrast-enhanced 3D T1-weighted MR images of high-grade glioma patients. The results showed that the recovered MR images using our 2D probabilistic undersampling pattern (with or without the reconstruction network) significantly outperformed those using the existing start-of-the-art undersampling strategies for both qualitative and quantitative comparison, suggesting the advantages and some extent of the generalization of our proposed method.     

磁共振T1WI加脂肪抑制扫描序列在膝关节半月板及关节软骨成像中的应用价值

目的 探讨T1WI加脂肪抑制序列在显示半月板及关节软骨的价值。方法 50例膝关节MRI检查的患者行矢状位T1WI常规自旋回波序列；质子密度加权快速自旋回波序列；T2加权梯度回波序列和SET1WI加脂肪抑制序列。分别将SET1WI加脂肪抑制序列与其他三种序列的影像进行比较。结果 矢状位T1加脂肪抑制序列清晰显示半月板结构达84％，其他三种序列仅为0.24％和30％；T1加脂肪抑制序列清晰显示关节软骨结构达94％，另三种序列为30％，16％，50％。结论 T1WI加脂肪抑制序列在半月板及关节软骨结构方面比其他三种序列更清晰，可作为膝关节检查的常规序列。     

MRI differential diagnosis of intrahepatic biloma from subacute hematoma

The magnetic resonance imaging (MRI) differential diagnosis of intrahepatic biloma from intrahepatic subacute hematoma has been reported in two cases. The biloma was heterogenously intense on T1-weighted images and homogenously hyperintense on T2-weighted images. The hematoma was hyperintense on the both T1-and T2-weighted MR images. The clinical significance of this MRI difference is that intrahepatic biloma needs drainage, whereas intrahepatic hematoma can heal spontaneously.     

Magnetic resonance imaging of abdominal pain during pregnancy

The objective of this review is to demonstrate magnetic resonance imaging as an important adjunct to ultrasound and computed tomography in the evaluation of the pregnant patient with abdominal pain. With the advent of ultrafast T2-weighted pulse sequences, fetal and bowel motion cause minimal artifact on the images. An accurate diagnosis can often be made in a few minutes based on these high-contrast images performed in 2 or 3 planes. T1-weighted gradient echo images with and without fat saturation are useful for identifying blood and fat, especially in the case of adnexal masses. Gadolinium-diethylenetriamine pentaacetic acid is rarely used to diagnose inflammatory or obstructive disease and is reserved for those patients with suspected malignancies.     

MR imaging of hepatocellular carcinoma

In this article, MR imaging features of hepatocellular carcinoma (HCC) are described. To better understand the MR imaging features of HCC, recent progress regarding its etiology, treatment, carcinogenesis, histology, and gross pathology will be described. Currently, T2-weighted fast spin-echo with fat saturation, and multiphasic dynamic gadolinium-enhanced two-dimensional and three-dimensional T1-weighted gradient echo imaging provides excellent results for detection and characterization of HCC.     

Fetal magnetic resonance hydrography: evaluation of a single-shot thick-slab RARE (rapid acquisition with relaxation enhancement) sequence in fetal thoracoabdominal pathology.

OBJECTIVES: To evaluate the potential of a single-shot thick-slab RARE (rapid acquisition with relaxation enhancement) sequence in fetal thoracoabdominal magnetic resonance (MR) examinations compared with multislice T2-weighted sequence and postnatal imaging. METHODS: RARE sequence is rapid and provides very heavily T2-weighted images. Twenty-seven fetal thoracoabdominal MR imaging examinations were performed at 23-38 weeks using our conventional protocol. This included thin multislice T2-weighted half-Fourier acquired single-shot turbo spin-echo (HASTE) sequence and thin-slice GE (gradient echo) T1-weighted images with a 1.5-T MR unit. A single-shot thick-slab (60 mm) RARE sequence was added to all MR examinations. The acquisitions were obtained with the mother breath-holding. The thick-slab heavily T2-weighted images were compared with HASTE sequence images and with postnatal imaging in all cases. RESULTS: The thick-slab RARE sequence did not show additional abnormalities compared with the conventional protocol but displayed an overall view of the urinary tract, tracheobronchial tract and small bowel. It gave information that was highly correlated with postnatal imaging, such as abdominal plain films, chest film or cystography. The quality of the thick-slab RARE images was considered as good in 13 cases (48%), moderate in 12 cases (45%) and poor in two cases (7%). CONCLUSION: Although thick-slab RARE sequence does not show additional abnormalities compared with the conventional protocol, it illustrates very nicely static fluids such as those in urinary dilatation, the esophagus and small bowel (normal or dilated) and thoracic cystic masses. It is very rapid (5 s) to perform, allows fetal hydrography, and correlates well with postnatal imaging.     

原发性骨骼淋巴瘤的影像学诊断

目的:分析13例骨骼淋巴瘤的影像学特征以探讨其影像学的诊断价值。材料和方法:13例经手术病理证实的骨骼淋巴瘤病例,术前均经平片检查,其中CT检查10例,MR检查9例。结果:4例何杰金淋巴瘤和9例非何杰金淋巴瘤分别累及脊柱6例,长管状骨5例,骨盆2例,病变主要累及脊柱的椎体和长管状骨的骨干,骨质改变为溶骨型9例(69%)和混合型4例(31%),骨质破坏以浸润性虫噬状骨质破坏为主;骨皮质破坏11例,但皮质破坏的程度总是很轻微;骨膜成骨3例(23%),软组织肿块形成7例(54%)。软组织肿块CT表现为低密度或等密度,境界清楚;骨骼MRI T1WI低信号9例,T2WI显示为略低信号2例,等信号2例,高信号5例;软组织肿块的MR信号变化少,T1WI略低于肌肉,T2WI总是略高于肌肉,MR动态增强扫描为轻~中等程度强化。结论:骨骼淋巴瘤影像学特征:①明显的浸润性虫噬状骨质破坏,而骨皮质破坏轻微,骨膜反应少见;②软组织肿块T2WI信号略高,且信号相对均匀。平片、CT和MRI等影像学检查可以作出诊断。     

乳腺磁共振成像扫描序列及扫描方位的选择

目的 探讨常规SE序列、FSE序列和3D-FSEGR序列及不同扫描方位在乳腺病变MRI诊断中作用。方法 40例乳腺肿块性病变常规SE序列T1WI及脂肪抑制FSE序列T2WI分别行轴位及矢状位平扫。注射Gd-DTPA后采用3D-FSPGR序列行矢状位动态增强扫描．之后再采用SE序列行脂肪抑制T1WI轴位、矢状位和(或)冠状位扫描。结果 3种扫描序列均有较高的信噪比及较高的病变与正常组织对比分辨率。SE序列T1WI平扫信噪比优，但病变与正常组织的对比分辨率不及FSE序列T2WI，而动态增强3D-FSPGR序列显示病变最敏感，可显示平扫不能显示或显示不明确的病变，且可根据病变的增强特点及时间-信号强度曲线进行定性诊断。增强后脂肪抑制SE序列T1WI显示病变亦较敏感，但不能行动态增强扫描。3种成像方位中，轴位与矢状位更利于显示病变及病变侵犯胸壁和腋窝淋巴结肿大。结论 动态增强3D-FSPGR是乳腺肿块病变中最有价值的检查序列。轴位与矢状位应作为乳腺检查中的基本位置。