梯度回波化学位移成像用于诊断腹腔含脂病变的价值

目的：评价梯度回波化学位移成像诊断腹腔含有脂质病变的价值。方法：把35例腹腔病变分成含脂病变组和非含脂病变组。均行梯度回波同相（in-phase,IP)和反相（opposed-phase,OP)扫描,观察这些病灶在IP和OP像上的显示情况;测定其信号强度。计算IP和OP像上信号强度变化率,并作非统计检验。结果：腹腔内含脂病灶在OP像上信号强度较IP像有明显下降,其信号强度变化率的中位数37．1％,而非含脂病灶信号强度变化不大,中位数为3．3％,两组差异有显著性意义（u＝4．56,P＜0．01）。结论：梯度回波化学位移成像简单实用,对检测腹部病变是否含有脂质有一定帮助。     

Quantitation of lipid in biological tissue by chemical shift magnetic resonance imaging

A method combining several previously used approaches is described for the rapid, accurate quantitation of the fat content of biological tissue based on chemical shift images (CSI) corrected for magnetic field inhomogeneity, and compensated for T₁, and T₂, effects. The gravimetrically determined lipid content of fatty tissues (pork fat, rabbit and human liver) that had been differentially depleted of lipid by chloroform extraction correlated well (r = 0.99) with the lipid image intensities of the respective tissues. This multi-point CSI method was used to quantitate lipid in fresh fatty human liver tissue (wet and dry) containing varying amounts of lipid. Plots of integrated lipid intensity versus tissue lipid content gave straight parallel lines for hydrated (r = 0.94) and dehydrated (r = 0.98) tissues, permitting determination of a proportionality constant for measuring absolute amounts of lipid present in a specific biological tissue. These results suggest the feasibility of using the method in vivo for absolute quantitation of lipid in tissues of agricultural (e.g. pork, beef) and medical (e.g. human liver) interest.     

Osteoblastoma in a lumbar vertebral body

We report a young man with low back pain suspected to have a disc protrusion. Imaging suggested a tumour of the dorsal portion of the fifth lumbar vertebral body. Operation suggested a giant-cell tumour and subsequent histology showed an osteoblastoma. All typical imaging features of osteoblastoma are demonstrated in this rather uncommon location. Contrast-enhancing bone-marrow oedema on MRI, with mild enhancement of the tumour, together with the CT appearances were the clues to the diagnosis. Received: 11 December 1997 Accepted: 3 September 1998     

Vertebral neoplastic compression fractures: assessment by dual-phase chemical shift imaging

PURPOSE: To compare normal vertebrae with vertebrae with neoplastic compression fractures by means of opposed-phase (OP) and in-phase (IP) gradient-echo (GRE) imaging. MATERIALS AND METHODS: On OP and IP T1-W GRE images (obtained at 1.5 T with the fast low-angle shot (FLASH) technique) of dual-phase chemical shift sequences, we compared the signal intensity ratios (SIRs) of normal and compression-fractured vertebrae in 108 patients. Dual-phase chemical shift sequences were measured in three groups of vertebral bone marrow in terms of the relative SIR in OP and IP images: group 1: normal vertebrae (N = 30 with 90 vertebrae); group 2: non-neoplastic compression-fractured vertebrae (N = 58 with 73 vertebrae); and group 3: neoplastic compression-fractured vertebrae (N = 20 with 27 vertebrae). The presence of compressed vertebrae was ascertained based on the consensus of two experienced radiologists. The mean SIRs among the three groups were compared by means of the Tukey-Kramer test. RESULTS: The mean SIRs of the three groups (group 1: 0.46 +/- 0.14; group 2: 0.63 +/- 0.21; and group 3: 1.02 +/- 0.11) were significantly different according to the Tukey-Kramer test (P < 0.01). CONCLUSION: OP and IP T1-W GRE MRI of vertebral SI abnormalities can help predict the nature of compression fractures.     

Taking advantage of chemical shift imaging: using opposed-phase images to locate the normal appendix on MR

Multiple sequences of 50 consecutive adult pelvic MRI exams were retrospectively reviewed by two radiologists to determine if opposed-phase T1 gradient echo imaging can assist in locating the normal appendix on pelvic MRI. If the appendix was visualized, it was always seen on the T2 sequence, except for one exam. The opposed-phase sequence had the second highest visualization rate, and the appendix was identified the least on the post-gadolinium sequence. The presence of a “button nose” sign was also assessed and was present in one third of cases.     

Determination of bone mineral density in the third lumbar vertebral body using photon absorptiometry techniques

Dual-photon absorptiometry and triple-energy X-ray absorptiometry were used to investigate the total bone mineral content and density as well as the trabecular bone mineral density in the third lumbar vertebral body. Both anteroposterior (AP) and lateral (LAT) measurements were performed. By combining the two projections it was found that the mean trabecular bone mineral density for all 202 subjects included in the study was 52% (SD±20%) of the total bone mineral density in the third lumbar vertebral body. The mean trabecular bone mineral density as a fraction of the total vertebral body bone mineral density decreased as a function of age. The relative annual change in this fraction differed between males and females. It was also found that neither trabecular nor total bone mineral density differed significantly between male and female subjects aged 25–35 years, and bone mineral density (BMD), expressed in g/cm³, showed no correlation to subject height, body weight or body mass index (BMI). Male and female individuals showed different rates of change of trabecular bone mineral density with age.     

化学位移成像及MR波谱分析在体外水脂模型中对脂肪定量的研究

目的 评价化学位移成像(chemical shift imaging,CSI)和MRS两种方法在脂肪研究中的作用,为进一步活体实验提供定量标准.方法 在7.0 T MR成像仪上运用CSI和MRS方法对体外水脂模型进行水脂定量分析.体外水脂模型的脂肪含量从0～100%平均分成11个组,各组间浓度相差10%,分别应用水、脂肪选择性CSI和1H-MRS对体外水脂模型进行图像和波谱数据采集,对2种方法所得结果分别与实际水脂含量进行单样本t检验及相关分析并比较两种方法问的相关性.MRS计算100%油模型饱和脂肪酸(fraction of saturated fatty acids,FS)、不饱和脂肪酸(fraction of unsaturated fatty acids,FU)的相对含量及多聚不饱和程度(polyunsaturation degree,PUD).结果 CSI法测定实际脂肪含量为50%～100%的测量值分别为(48.0±1.0)%、(57.0±0.5)%、(67.3±0.6)%、(77.3 ±0.6)%、(83.3±0.6)%和(91.0±1.0)%;MRS测定实际脂肪含量为10%～60%的测量值分别为(8.3±0.6)%、(16.3±0.7)%、(27.7±0.6)%、(36.0±1.0)%、(43.5±0.6)%和(56.5±1.0)%,均轻度低估了脂肪含量,差异均有统计学意义(P值均<0.05).CSI与MRS计算的脂肪含量与实际脂肪含量间均呈线性相关(CSI:r=0.998,MRS:r=0.996;P值均<0.01);两种方法间也呈线性相关(r=0.992,P<0.01),两种方法定量脂肪含量差异无统计学意义(t=-0.125,P:0.903).MRS计算橄榄油的FS和FU相对含量分别为0.15和0.85,PUD为0.0325,与实际含量一致.结论 在7.0 T MR成像仪上,体外水脂模型证实CSI和MRS定量脂肪的准确性及在脂肪研究上的可行性.     

腰椎静脉丛三维增强MR静脉成像初步研究

目的 探讨正常人腰椎静脉系统在三维增强MR静脉造影(MRV)的显示率,初步确定正常人腰椎椎管内前静脉(AIVV)的宽度范围。观察腰椎静脉系统在各种疾病情况下的表现。方法89例MR增强扫描受检者行MRV检查,其中62例为正常志愿者。分别观察不同年龄组各个腰椎节段的椎管内、外静脉显示情况。测量AIVV的宽度。观察各种疾病时椎管内、外静脉的表现。结果除L1和L2水平的左右吻合静脉外,其他各个节段41岁以上组的静脉显示率均低于40岁以下组(P<0.05)。AIVV平均宽度从L1-5逐渐增粗;年龄、性别、左右侧差异无统计学意义。AIVV全部显示的42例正常志愿者中,AIVV的平均宽度L1-L5逐渐增粗,范围在(3.9±0.6)mm-(7.9±1.2)mm;各种疾病时,AIVV可表现为正常、受压、移位或扩张。结论 三维增强MR静脉造影能满意地显示AIVV各分支及椎管外静脉的全貌,能够显示各种病变时椎静脉相应改变,对于指导临床治疗、研究椎静脉的临床意义具有潜在价值。     

High-resolution magnetic resonance imaging of normal porcine cartilaginous epiphyseal maturation

The aim of this study was to determine whether highresolution magnetic resonance (MR) imaging could differentiate epiphyseal and articular cartilage in the cartilaginous epiphysis and demonstrate its developmental changes. T1- and T2-weighted (T1W and T2W) spin-echo sequences at 50-mm field of view (FOV) of hip joints were obtained from 14 piglets (newborn to 6 months). Subsequently, high-resolution MR images (15-mm FOV) of a biopsy core of the proximal femoral cartilaginous epiphysis were correlated with histology. Newborn cartilaginous epiphysis demonstrated homogeneous signal intensity on T1W and T2W imaging with abundant cartilage canals. From 2 weeks of age, the cartilaginous epiphysis showed a diminution of cartilage canals, with three zones evident on T2W imaging consisting of a low-signal middle zone separating two higher signal zones. Histologic evaluation demonstrated four distinct morphologic laminas with a decrease in overall cartilage thickness with age. The laminas were not as well defined in the newborn compared with the older piglets. No simple correlation was found between the MR zonal pattern and the morphological laminas on histology. No distinct demarcation between the articular cartilage and epiphyseal cartilage was present. MR can visualize cartilage canals and demonstrate changes in the cartilaginous epiphysis that occur with maturation. What component of the cartilaginous epiphysis that accounts for the MR differences seen between newborn and older piglets remains unclear.     

Fracture-associated and idiopathic subchondral vertebral lesions: a magnetic resonance study in autopsy specimens with histologic correlation

Objective  The aim of this study was to describe and compare the magnetic resonance (MR) and histological appearance of subchondral vertebral lesions that are idiopathic or that develop with vertebral fractures. Materials and methods  T1- and T2-weighted spin-echo images and radiographs were obtained in 81 cadaveric spine specimens. All subchondral vertebral lesions that were considered to be idiopathic or associated with vertebral end plate fractures were selected. Lesions due to growth disturbance were excluded. Radiographs and MR images were analyzed in consensus by two radiologists, and sampled specimens were analyzed by a pathologist. Results  Eleven idiopathic and ten fracture-associated vertebral lesions were available. On T1-weighted images, all lesion signal intensity was low and homogeneous. On T2-weighted images, all idiopathic lesions showed a heterogeneous signal with a central low or intermediate signal component and a peripheral high or intermediate component. All but one fracture-related lesions showed a homogeneous intermediate to high signal intensity. Histological analysis of idiopathic lesions showed a central acellular fibrous connective tissue in all cases surrounded by loose connective tissue in nine cases. Herniated disk material and cartilage metaplasia were found in one lesion only. Fracture-associated lesions contained herniated disk material, necrotic tissue, and loose connective tissue with a peripheral component of loose fibrovascular connective tissue in four cases only. Conclusion  MR and histological appearance of idiopathic and fracture-associated subchondral vertebral lesions differ, suggesting that they might have a different origin.     

Popliteal cysts: a reassessment using magnetic resonance imaging

The advent of magnetic resonance imaging (MRI) prompted the reevaluation of the incidence of popliteal cyst and its associated injuries. We reviewed more than 1000 consecutive MRI examinations of the knee performed on patients referred for evaluation of internal derangement. We report a 5% incidence of popliteal cyst, which is lower than has previously been determined. We believe that the reported higher incidence was due to arthrographic distention of normal, collapsed bursae. The strong association between popliteal cyst and tear of the medial meniscus is confirmed. We report for the first time to our knowledge the 13% association between popliteal cyst and complete tear of the anterior cruciate ligament.     

腰椎骨髓信号在高、低场磁共振的对比

目的：通过对比腰椎骨髓信号在高、低场磁共振各序列上的差异,找出高、低场磁共振对病灶检查的局限性,避免不同场强磁共振的不足,以积累诊断经验。方法收集2012年9月～2012年12月腰椎退变14例,腰椎外伤8例,腰椎骨转移瘤5例,在Siemens verio 3．0T和日立Airis‐Ⅱ0．3T磁共振仪上分别做检查,两次检查在同一天完成,期间未做任何治疗,两名副主任医师单盲法阅片,分析14例腰椎退变中30处局灶性黄骨髓,8例腰椎外伤中10处骨髓水肿,5例腰椎转移瘤中16处转移灶及2例瘤周水肿的信号在高、低场磁共振各序列的表现差异。结果在Siemens verio 3．0T磁共振仪上,各序列信号清晰,但T2加权像对水肿显示不清;在Airis‐Ⅱ0．3T磁共振仪,各序列图像较模糊,尤其 T2加权像对局灶性黄骨髓显示不清,但对水肿信号的显示明显优于高场T2加权像。结论高场磁共振,各序列图像清晰,低场磁共振图像模糊;低场T2加权像对于局灶性黄骨髓的显示明显差于高场;而对于水肿的显示明显优于高场 T2加权像,高场磁共振的T2压脂序列是不可缺少的。     

Intralabyrinthine schwannoma shown by magnetic resonance imaging

Intralabyrinthine schwannomas are rare benign tumours which present with progressive or fluctuant audiovestibular symptoms and may mimic Meniéres discase. The size and position of these lesions make preoperative diagnosis unusual and most are discovered incidentally at labyrinthectomy. A case is reported which was diagnosed on magnetic resonance imaging and confirmed at surgery.     

增强减影MRI诊断椎体转移瘤的研究

目的:探讨增强减影MRI对椎体转移瘤的诊断价值。方法:对30例41个椎体行常规MR平扫及增强扫描,并在增强后对病灶同一层面进行叠加减影处理。结果:增强减影MRI能清晰显示椎体内骨小梁结构,更容易发现微小病灶,更好地显示转移性肿瘤的形态学特点。结论:增强减影MRI技术对提高脊椎转移瘤的检出率有重要的临床应用价值。     

全身DWI的正常表现及在转移瘤筛查中的临床应用

目的:探讨磁共振全身扩散加权成像(全身DWI)的正常表现及在转移瘤筛查中的应用价值。方法:20例健康志愿者及25例疑似或确诊恶性肿瘤患者行磁共振全身扩散加权成像,其中11例肿瘤患者同时行PET/CT检查。全身DWI应用STIR抑制背景信号,从头顶至股骨上分段无间隔扫描,共覆盖1080～1440mm,b值取0及600s/mm2。结果:在健康志愿者的全身DWI像上,脑实质、涎腺、椎间盘、脊髓、脾脏、肾脏和前列腺、睾丸、子宫、卵巢等脏器呈高信号,其余脏器及骨骼呈等信号。原发恶性肿瘤及转移灶在全身DWI呈明显高信号,对比度高于常规MRI序列。25例患者全身DWI共检出70处高信号病灶,包括原发恶性肿瘤及转移灶68处,良性病灶2处,显示率为98.6%。11例PET/CT检查共有20处阳性显像,原发恶性肿瘤及转移灶16处,良性病灶4处,显示率100%。结论:磁共振全身扩散加权成像一次检查可完成从头顶至股骨上段的大范围成像,对恶性肿瘤原发灶及转移灶有较高的显示率,可以作为恶性肿瘤患者原发及转移灶筛查的有力工具之一。     

大脑胶质瘤病磁共振成像结合磁共振波谱成像的诊断价值

目的：探讨磁共振成像（MRI）结合磁共振波谱成像（MRS）对大脑胶质瘤病的诊断价值。方法对15例经活体组织检查或手术病理证实的大脑胶质瘤病患者的临床表现及MRI平扫、增强,MRS影像学资料进行回顾性分析。MRI常规行T1WI、T2WI及FLAIR序列,采用时间飞跃法（TOF）的磁共振血管成像（MRA）,T1WI增强扫描。氢质子MRS采用单体素STEAM序列,并分析N-乙酰天门冬氨酸（NAA）、肌酸（Cr）、胆碱复合物（Cho）等物质峰值改变。结果所有病例均侵犯2个或2个以上脑叶,以颞叶、枕叶、胼胝体、基底节和丘脑等部位侵犯受累常见。病变区T1WI呈低或等低信号、T2WI呈高或混杂高信号、FLAIR上为高信号,未见明显坏死、钙化,受累区域脑组织肿胀,占位效应轻。注射钆喷酸葡胺增强扫描示10例无明显强化、3例斑片状强化、1例结节状强化、1例线状轻度强化。病变区域MRS表现为不同程度NAA降低,NAA/Cr比值降低;Cho上升,Cho/Cr和Cho/NAA的比值上升。结论 MRI结合MRS对大脑胶质瘤病的诊断及鉴别诊断具有临床价值,是目前诊断大脑胶质瘤病的首选影像学方法。     

Temperature mapping using water proton chemical shift obtained with 3D-MRSI: Feasibility in vivo

This article discusses the applicability to a living animal of the temperature mapping method using the water proton chemical shift obtained with three-dimensional magnetic resonance spectroscopic imaging (3D-MRSI). There are several sources of error in obtaining the spectra with 3D-MRSI: signal noise, limitation in the frequency resolution due to the finite signal length, intravoxel inhomogeneity in the static magnetic field, and variation in the magnetic field due to the eddy current magnetic field. A spectral estimation method called phase deduction complex Lorentzian fitting (PD-CLF) was proposed. Numerical simulations demonstrated that this method reduces the error in the chemical shift to one third of that obtained with the simple frequency subtraction method that uses zero-padded first Fourier transformation (FFT). The temperature images obtained using 3D-MRSI with PD-CLF clearly visualized the changes and distribution of temperature in an anesthetized rat.     

Utility of chemical shift and diffusion-weighted imaging in characterization of hyperattenuating adrenal lesions at 3.0T

Objective

The purpose of our study was to evaluate the value of chemical shift imaging (CSI) and diffusion weighted imaging (DWI) at 3.0 T MRI in adrenal hyperattenuating lesions.

Methods

Fifty-one hyperattenuating adrenal lesions in 40 patients were evaluated. Signal intensity index (SII), adrenal to spleen ratio (ASR) and apparent diffusion coefficient (ADC) were used as quantitative analysis parameters.

Results

The mean SII, ASR and ADC values were: benign pheochromocytomas (n = 22), 7.04%; 0.96, 1.15 × 10⁻³ mm²/s; lipid-poor adenomas (n = 18), 33.77%, 0.71, 1.07 × 10⁻³ mm²/s; malignant tumors (n = 7), 11.24%; 1.00; 0.92 × 10⁻³mm²/s. There were significant differences between the lipid-poor adenomas and nonadenomas for SII and ASR, and there were significant differences between the benign and the malignant tumor ADC values. The optimal diagnostic threshold point of SII and ASR for lipid-poor adenomas was 11.96%, 0.83, the sensitivity and specificity were 88.9%, 97.5% and 97%, 83.3%. The optimal diagnostic threshold point of ADC value for benign lesions and malignant tumors was 1.04 × 10⁻³ mm²/s, the sensitivity and specificity were 61.4% and 85.7%.

Conclusion

Quantitative analysis of chemical shift MRI and DWI can help to characterize the hyperattenuating adrenal lesions, especially in differentiatiation between the lipid-poor adenomas, the benign pheochromocytomas, and the malignant tumors.     

慢性肾衰病人椎体骨质变化的MRS研究进展

慢性肾功能衰竭病人的骨质改变目前已成为影响其生存质量的突出问题.如何更好地评估其骨质变化情况,进而早期进行有效干预及治疗已成为重要的研究内容.MR波谱成像(MRS)作为MR功能成像的一种已成功应用于中枢神经系统、乳腺及前列腺等的检测,而在评价骨质变化中的价值亦在研究中.现就MRS评估慢性肾功能衰竭病人椎体骨质变化情况予以综述.