基于正则化的磁共振相控阵线圈图像均匀性校正算法

由于能提供更大的扫描视野,更高的信噪比和缩短扫描时间,相控阵线圈已经被广泛使用在磁共振成像(MRI)设备中。相控阵线圈的图像重建合成最常用的是SOS算法,但是SOS算法通常会造成图像的灰度不均匀。这样不仅会直接影响医生诊断的准确性,同时对图像自动分割等后处理技术的使用也会产生不良影响。本文提出一种改进的基于正则化的最小二乘化方法,用于MRI相控阵图像的合成。在该方法中利用均匀的大体线圈和相控阵线圈进行预扫描获得线圈敏感图,通过引入正则函数来控制重建图像的噪声。此外,在正则函数中还使用大体线圈的预扫描图像作为参考图像。使用水模和志愿者成像数据验证,该方法能够有效提高相控阵线圈重建图像的均匀性。     

台式核磁共振成像仪高灵敏微型射频线圈的研制

RF线圈(又称探头)是核磁共振波谱仪和磁共振成像仪中的关键部件。根据不同用途,磁共振射频线圈可以分为许多种。研制了一种用于试管样品的高灵敏度微型射频线圈,并在台式磁共振成像仪上进行了相关射频线圈的性能测试,证实了设计的理论和方法。     

以电解可脱性弹簧圈急诊栓塞破裂动脉瘤疗效观察

目的探讨电解可脱性弹簧圈(GDC)急诊栓塞破裂动脉瘤的临床治疗效果。方法对24例急性自发性蛛网膜下腔出血(SAH)患者于SAH发病12 h内行GDC动脉瘤栓塞,动脉瘤直径3~22 mm。6例动脉瘤颈较宽的患者行瘤颈成形术。术后常规给予低分子肝素静脉滴注7 d。结果动脉瘤栓塞后随访3个月~1 a,无一例发生再出血。其中恢复良好17例,中等5例,差2例,死亡3例。有6例发生血管痉挛。结论用GDC急诊栓塞为治疗破裂动脉瘤开拓了新途径。     

磁共振成像在颞下颌关节内紊乱症诊断中的价值

目的：评价磁共振成像（MRI）诊断颞下颌关节内紊乱症（TMJID）的价值.方法：20例（40侧颞下颌关节）颞下颌关节紊乱病（TMD）患者,使用GE Signa ExciteⅡ 1.5T超导型MR扫描仪,采用颞下颌关节表面线圈,在斜矢状闭口位、开口位和斜冠状闭口位上应用自旋回波（SE）T1WI、T2WI、PDWI及快速梯度回波（FSPGR）序列进行扫描,确定有无TMJID.结果：40侧关节均获得清晰的MR图像,其中13侧（32.5%）关节盘的位置和形态表现正常,21侧（52.5%）关节盘有前移位,6侧（15.0%）关节盘有旋转移位.15侧关节盘在移位的同时存在变形改变,4侧关节髁状突存在退行性骨关节病改变;SE T1WI、T2WI能清晰地显示关节盘的位置、形态和关节的骨性结构及翼外肌结构,可作为TMJ检查的常规扫描序列.PDWI和FSPGR序列可作为辅助扫描序列,斜矢状闭口位能清晰地显示盘前移位和后移位,斜矢状开口位能清晰地显示可复性和不可复性盘前、后移位,斜冠状闭口位能清晰地显示关节盘侧方移位.结论：MRI是诊断关节内紊乱症理想的方法.     

磁共振8通道神经血管阵列线圈的临床应用与扫描技术

目的:介绍和探讨NVA-8通道神经血管阵列线圈(neurovascular array 8 channel,简称NVA-8线圈)的临床应用优势与扫描技术。方法:使用美国GE 公司生产的1．5T超导型核磁共振成像系统(GE, Signa,CV/i)及其配置的NVA-8线圈,分别对100例疑有或确诊有头颈部某些疾病的病例进行颅脑、鼻咽、颈部、颈椎扫描,或上述部位中两个或两个以上联合扫描,并与以往用4通道头颈联合线圈、单通道头部线圈扫描的100例患者影像资料作比较,探讨NVA-8线圈的临床应用优势与扫描技术。结果:100例均获得满意的MR影像,且与4通道头颈联合线圈、单通道头部线圈比较,具有明显的优越性。结论:1．使用NVA-8线圈,提高了MR图像的质量,同时比使用4通道头颈联合线圈、单通道头部线罔缩短了1/3-1/2的检查时间: 2．可以给患者一次摆位,同时进行头颈多个部位的扫描,获得完整的头颈部MR影像,避免了多次搬动线圈和患者多次上下扫描床的麻烦。     

Iatrogenic secondary post‐partum haemorrhage: Apropos of two uncommon cases

In this article we would like to highlight uterine pseudoaneurysm as a cause of secondary post‐partum haemorrhage following Caesarean section. We would like to stress Doppler ultrasound scan as the initial screening modality for this condition. We also describe angioembolization as the prudent treatment option for this condition rather than resorting to surgery.     

Endovascular occlusion of intracranial aneurysms with Guglielmi detachable coils: correlation between coil packing density and coil compaction

Summary  This retrospective analysis was undertaken to evaluate a possible relationship between coil packing densitiy and coil compaction on intracranial aneurysms embolized using Guglielmi detachable coils (GDCs).  Of the patients who underwent endovascular surgery using GDC in our hospital between 1994 and 1998, 33 patients had endovascular treatment with GDC and were examined by follow-up angiography at least 12 months after surgery. They had coil embolization to the extent where aneurysms were no longer filled or only faintly filled as shown by cerebral angiography immediately after surgery.  At follow-up angiography, coil compaction was observed in 3 aneurysms. In all patients with coil compaction, the coil packing density was below 20% (14.5±4.0%). On the other hand, it was over 20% (25.7±4.7%) in all patients without coil compaction. In the 11 patients with a basilar bifurcation aneurysm, the coil packing density was over 24% and no coil compaction was observed.  The coil packing density seems to be one of the critical factors, particularly for predicting whether or not coil compaction will occur. Endovascular surgery should be performed to obtain coil packing density higher than 20%.     

Pilot study of dermal and subcutaneous fat structures by MRI in individuals who differ in gender, BMI, and cellulite grading

BACKGROUND/AIMS: Puckered, dimply skin on the thighs, hips, and buttocks is known as cellulite. The cause of cellulite is not known, although there are a number of different hypotheses. In this study, we use magnetic resonance (MR) micro-imaging to study cellulite skin. To the best of our knowledge, this is the first reported MR study of cellulite. METHODS: High-resolution in vivo MR images of the postlateral thigh skin of two male groups and four female groups were obtained. Subjects were grouped according to their body mass index (BMI) and cellulite grade. A qualitative assessment of how MRI can be used to differentiate skin tissue at different levels of cellulite grading was performed. RESULTS: We found that changes in skin architecture with cellulite can be visualized by in vivo MR micro-imaging. The skin fat layers beneath the dermis and down to the level of muscles are well visualized in the images. Also, the diffuse pattern of extrusion of underlying adipose tissue into dermis is clearly imaged, and was found to correlate with cellulite grading. We also show that other skin tissue parameters such as (a) the percentile of adipose vs. connective tissue in a given volume of hypodermis and (b) the percentile of hypodermic invaginations inside the dermis are correlated with cellulite grade. CONCLUSION: MR images can be interpreted to measure tissue parameters correlated with cellulite. Considering that we had only three subjects in each group, the achievements of this pilot study were highly satisfactory. We have shown that the in vivo micro-MR is a technique able to detect the effects of cellulite and gender. This study can be extended for further investigations of drugs and/or medical devices for cellulite treatment.     

High resolution MR imaging of the bilateral hips with dual phased-array coil

We applied dual-flex coils in a phased-array configuration to obtain high resolution MR images of the bilateral hips and compared the image quality with non-phased-array imaging. Multiple fast spin-echo images of both hips were obtained in a single acquisition. Two consecutive acquisitions with and without phased-array capability were performed in 22 hips and a fluid-filled phantom. The signal-to-noise ratio (S/N) enhancement values were calculated. Subjective image analysis was also obtained from three independent reviewers. High quality MR images were obtained using dual-array coils with a S/N enhancement value of 1.40 for a phantom and 1.83 to 2.22 for subject hips. On subjective analysis, the dual array enhanced delineation of the acetabular labrum, articular cartilage, and retained fluid. The dual array may be of diagnostic value with a higher S/N enhancement and subjective superiority of the images obtained.     

Slightly flexed knee position within a standard knee coil: MR delineation of the anterior cruciate ligament

The purpose of this study was to assess the value of positioning the knee slightly flexed within a standard MR knee coil in delineation of the anterior cruciate ligament (ACL). Within the confined space of a commercially available knee coil, knee could bend as much as 30 °, average 17 °of flexion. Sets of oblique sagittal MR images were obtained at both fully extended and slightly flexed positions. Twenty-two normal knees and 18 knees with ACL tears were examined and paired MR images were evaluated by two observers. Compared with knee extension, the MR images for knee flexion provided better clarity in 57 % of reviews of full length of the ACL and 53 % of the femoral attachment. In the extended position the anterior margin of the ligament was obscured due to partial averaging with the intercondylar roof. We recommend examining the knee in an achievable flexed position within the standard knee coil. Received 3 December 1996; Revision received 24 February 1997; Accepted 9 April 1997