The influence of field strength on the apparent diffusion coefficient of 3He gas in human lungs

The (3)He MR diffusion signal is sensitive to lung microstructure, but it is also affected by the presence of background field inhomogeneities induced by the magnetic susceptibility difference at the air-tissue interface. These susceptibility-induced gradients, which are dependent on field strength, have been assumed negligible in theoretical models used to extract airway morphometric information from (3)He MR diffusion data at field strengths up to 4.7 T. In this work, the effect of susceptibility gradients on (3)He apparent diffusion coefficient is demonstrated with experiments in healthy volunteers at two B(0) field strengths: 1.5 and 3 T. Apparent diffusion coefficient values obtained at 3 T were systematically larger than at 1.5 T, demonstrating that susceptibility effects are statistically significant even at clinical field strengths (B(0) ≤ 3 T) and introduce biases in the estimates of airway dimensions (e.g., mean linear intercept up to 17% larger at 3 T than 1.5 T). Susceptibility effects should be taken into account in the development of theoretical models of lung (3)He MR diffusion and considered when interpreting (3)He apparent diffusion coefficients obtained at different B(0).     

Renal and perirenal space involvement in acute pancreatitis: An MRI study

Objectives

To study the prevalence and characteristics of renal and perirenal space involvement and its relation to the severity of acute pancreatitis (AP) using MRI.

Methods

115 patients with AP who underwent MRI with the clinical kidney function test were retrospectively analyzed in this study. MRI sequences included conventional and diffusion weighted imaging (DWI) sequences. The renal and perirenal space involvement in AP was noted on MRI. The renal apparent diffusion coefficient (ADC) on DWI was measured for each kidney. The severity of AP on MRI was graded using MR severity index (MRSI). The relationships among the renal and perirenal space involvement on MRI, the renal ADC, MRSI and the results of the kidney function test were analyzed.

Results

In the 115 patients with AP, the renal and perirenal space abnormalities detected included renal parenchymal abnormalities (0.8%), abnormalities of the renal collecting system (2.6%), renal vascular abnormalities (1.7%), thickened renal fascia (99%), perirenal stranding (62%) and perirenal fluid collection (40%). The prevalence of perirenal space abnormalities was correlated with the severity of AP based on MRSI (P < 0.05). The renal ADC values were lower in patients with abnormal kidney function than in those without kidney injury (P < 0.05). The prevalence of kidney function abnormalities was 9.4%, 32% and 100% in mild, moderate, and severe AP cases, respectively (P = 0.00).

Conclusion

Perirenal space involvement is much more than renal parenchymal involvement in AP. The prevalence of perirenal space involvement in AP on MRI has a positive correlation with the severity of AP according to MRSI.     

Differential diagnosis between malignant and benign hepatic tumors using apparent diffusion coefficient on 1.5-T MR imaging: a meta analysis

This meta-analysis evaluates the diagnostic accuracy of diffusion-weighted MR imaging with ADC values for differentiation between malignant and benign hepatic focal lesions. From retrieved articles, we selected 7 sets of data in 6 articles, which met all the included criteria, for meta-analysis. The pooled sensitivity and specificity were 86% (95% CI, 0.83-0.90) and 84% (95% CI, 0.78-0.88), respectively. However, notable heterogeneity between studies was noted and no covariate evaluated can explain the cause. Only b factor correlated with the mean ADC values of malignant and benign hepatic tumors. In conclusion, ADC value was useful for differentiation between malignant and benign hepatic focal lesions. But, significant heterogeneity between studies underlines the need for further efforts to optimize standardization and reproducibility of the utilized techniques and methods.     

Can DWI & ADC differentiate orbital lymphoma,non-specific orbital inflammation and orbital cellulitis?

The aim of this work

To differentiate orbital lymphoma, non-specific orbital inflammation (NSOI) and orbital cellulitis using DWI & ADC, as there is marked clinical overlap in the diagnosis of these three orbital conditions.

Material and methods

Twenty-five cases chosen from attendants of the outpatient clinic of the Ophthalmology Department of Zagazig University Hospitals with different orbital pathologies presenting with orbital inflammatory signs and/or proptosis were all examined with conventional MRI sequences then functional DWI and ADC map and values were performed.

Results

Six cases (6/25) were diagnosed as orbital lymphomas (24%), 14 cases (14/25) NSOI (formerly known as orbital inflammatory syndrome) (56%) and 5 cases (5/25) as orbital cellulitis (20%), in DWI the greater the restriction was detected in lymphomas, followed by NSOI and lastly with orbital cellulitis and ADC values ranging from 0.6 to 0.9 × 10⁻³ mm²/s for lymphoma, 1.1 to 1.3 × 10⁻³ mm²/s in NSOI and 1.5 to 1.7 × 10⁻³ mm²/s in orbital cellulitis.

Conclusion

DWI & ADC can differentiate orbital lymphoma from NSOI and orbital cellulitis and help rapid management.     

多元文化背景下医学生医德系统构建探讨

在医德构建面临多元文化挑战的背景下,医学生医德培养应以社会主义核心价值观为核心原点,从构建目标、医德内容、教育方式、时间维度四个方面入手,系统构建;以学生为本、培育共同价值观;注重制度建设和路径选择是医德系统构建的着力点。     

表观弥散系数预测评估鼻咽癌淋巴结放化疗后早期疗效的价值

目的 通过测量、分析鼻咽癌转移性淋巴结放化疗前后的相关表观弥散系数(ADC)指标,探讨ADC值在预测鼻咽癌转移性淋巴结放射敏感性以及辅助评估放化疗后早期疗效中的应用价值.方法 共收入符合纳入标准的鼻咽癌患者60例,淋巴结115枚.分别测量靶病灶放化疗前后的平均ADC(ADCmean)、最小ADC值(ADCmin)和体积(V),计算放化疗前后的ADC差值(△ADC)、ADC变化率(△ADC％)及体积变化率(△V％),分析各ADC指标与△V％之间的相关性,并将淋巴结分为有效组(CR+ PR,n=92)及无效组(SD+ PD,n=23),比较两组间各ADC指标的差异.结果 放化疗前ADC mean、ADCmin与△V％均无明显相关性,而△ADC及△ADC％(包括ADCmean、ADCmin)与△V％均呈负相关,其中△ADCmean与△V％间的相关系数最大(r=-0.427,P＜0.01).放化疗后有效组及无效组间治疗前ADC值(ADC0)差异无明显统计学意义,△ADC及△ADC％差异有统计学意义(P＜0.05).绘制ADC各指标的ROC曲线,ADCmean的曲线下面积最大.结论 放疗前ADC尚不能作为预测鼻咽癌转移性淋巴结放疗敏感性及放化疗后早期疗效的指标,而△ADCmean可作为评估其早期疗效的辅助指标.     

临床医学教育综合改革中的医学生职业精神培养研究内容——医学生职业精神培养研究之三

临床医学教育综合改革对医学生职业精神培养提出了具体要求.医学生职业精神培养应当以社会主义核心价值观为指导思想,以以人为本、诚实守信;爱岗敬业、恪尽职守;热爱生命、维护健康;至真至善、追求卓越为主要内容.医学生职业精神培养过程中要处理好公平与公益、显性与隐性、他律与自律的关系.     

子宫肌瘤患者子宫正常区域的表观弥散系数研究

目的研究子宫肌瘤患者子宫正常区域各分区结构（内膜、结合带、肌层）表观弥散系数（ADC）特点及其随月经周期的变化趋势。方法 31例具有正常月经周期的子宫肌瘤患者,分为分泌期（17例）和增殖期（14例）两组。行子宫横断面DWI（b值为0、700s/mm2）扫描,分别测量子宫内膜、结合带和肌层ADC值,分析子宫分区结构ADC值差异及月经周期对其影响。结果分泌期组,子宫三层分区结构ADC值两两之间有明显统计学差异（F=104.279,p〈0.001）。增殖期组,内膜和肌层ADC值之间无统计学差别;结合带ADC值均小于内膜、肌层ADC值,有明显统计学差异（P〈0.001）。肌层ADC值在分泌期组（1.726±0.210×10^-3mm^2/s）和增殖期组（1.550±0.128×10^-3mm^2/s）有统计学差异（t=2.729,p〈0.05）;内膜在分泌期组和增殖期组比较,以及结合带在分泌期组和增殖期组比较,均无统计学差异。结论具有正常月经周期的子宫肌瘤患者子宫体部正常区域ADC值受到解剖分区结构及月经周期的影响。同时,内膜及结合带ADC值在增殖期和分泌期无统计学差异,可能与子宫肌瘤患者性激素分泌异常相关。     

神经白塞病的MRI价值探讨

目的通过对神经白塞病(Neuro-Behcet's disease NBD)磁共振(magnetic resonance image,MRI)的影像学表现分析,以提高对神经白塞病MRI诊断的认识。方法回顾性分析经临床证实的6例神经白塞病MRI表现,评估病灶的分布及形态学特点,分析总结不同序列MRI的信号特征。结果 6例患者均为实质型中枢神经系统损害,其中单纯脑干损害1例,混合型损害5例。6例脑干损害表现为长条形或不规则形,包括中脑大脑脚、桥脑、和延髓病变;5例为类圆形基底节区损害;2例颈髓损害为长条形。6例行头颅MRI检查,均显示颅内散在T2WI稍高信号,T1WI等或低信号影,FLAIR呈高信号,DWI(b值为1000s/mm2)显示为稍高信号,ADC图信号轻度升高且ADC值病灶处较对侧增高。3例行增强扫描均出现环形强化。2例颈髓MRI分别显示颈4、5水平颈髓长条形T2稍高信号影。1例行磁共振波谱(Magnetic resonance spectroscopy,MRS)检查显示病灶处各代谢产物的峰值均正常。结论 MRI检查对于神经白塞病的诊断非常敏感,且不同序列均具有其特征性的改变。