MRI of an angiomyolipoma

Angiomyolipomas are uncommon, benign tumors of the kidney with certain characteristic diagnostic features. We report a case of this condition in which MRI helped to characterize the lesion.     

MRI findings of primary small-cell carcinoma of kidney

We report the MRI findings of primary small-cell carcinoma of the kidney (PSCCK) in a 59-year-old female. This tumor appeared as a 16-cm mass that arose from the right kidney. This lesion had diminished signal on T1-weighted images and heterogeneous mixed signal on T2-weighted images. The tumor primarily involved the renal medulla with persistent thin renal cortex. Despite the tumors' large size, no substantial central necrosis was present. The predominant medullary location and the lack of central necrosis in this large tumor were features unusual for renal cell carcinoma and should raise the suspicion of another malignancy, the differential diagnosis of which should contain extrapulmonary small-cell carcinoma of the kidney.     

Quantitative renal function assessment of atheroembolic renal disease using view-shared compressed sensing based dynamic-contrast enhanced MR imaging: An in vivo study

Atheroembolic renal disease (AERD) is the major cause of renal insufficiency in the elderly, and particularly, the diagnose of AERD is often delayed and even missed due to its nonspecific presentation and the sudden occurrence of an embolic event.To investigate the feasibility of the view-shared compressed sensing (VCS) based dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in the assessment of AERD in animal models. The reproducibility of VCS DCE-MRI based glomerular filtration rate (GFR) estimation was first evaluated using the three healthy rabbits. Animal models of unilateral AERD were then conducted. All the rabbits underwent VCS DCE-MRI and the GFR maps were estimated by a commonly used cortical-compartment model. The whole kidney and suspicious lesion region GFR values of embolized kidneys were then compared with the corresponding values of normal kidneys. Finally, the suspicious lesion regions were confirmed by the corresponding renal specimens and histological findings. The reproducibility of GFR measurements was analyzed using the coefficient of variation and Bland-Altman analysis. The GFR values of normal and embolized kidneys were compared using the Student t-test.Contrast-enhanced images with sufficient diagnostic quality and reduced motion artifacts are obtained at a temporal resolution of 2.5 s. The Bland-Altman plot indicated close agreement between the GFR values estimated from between-day scans in healthy rabbits. Besides, there existed significant differences between the pixel-wise GFR values of normal and AERD kidneys in region-based comparison(P < 0.0001). The suspicious lesions are consistent well with the renal specimen and histological findings.The preliminary animal study verified the feasibility of VCS DCE-MRI for renal function evaluation, and the strategy could potentially provide a valuable tool to identify AERD.     

Apparent diffusion coefficient (ADC) measurements may be more reliable and reproducible than lesion volume on diffusion-weighted images from patients with acute ischaemic stroke-implications for study design

Early ischemic change after stroke can be demonstrated with diffusion-weighted imaging (DWI) and quantified by measuring the apparent diffusion coefficient (ADC) and/or lesion volume. We examined the reliability and reproducibility of lesion volume and ADC measurement on DWI images, and discuss the implications for clinical studies. Using 38 DWI scans from 15 stroke patients, two observers (a physicist and a neuroscience graduate) blind to each other, recorded the lesion volume on DWI sequences, measured the ADC values in this volume and calculated the ratio of ischemic: control ADC (ADCr). One observer repeated his measurements blind to his first, and also examined the effect on lesion volume and ADC of deliberately varying by only one pixel, the outline of the visible boundary of the lesion. The inter and intra-rater reliability were worse for lesion volume than ADC or ADCr measurements: lesion volume, inter-rater coefficient of variation (CoV) 85 +/- 130%, intra-rater CoV 20+/-SD80% (p < 0.05); ADC inter-rater CoV 7.7 +/- SD 19%, intra-rater CoV 0.2 +/- SD 12% (p = NS); and ADCr inter-rater CoV 8 +/- SD27%, intra-rater CoV 0.8 +/- SD73% (p = NS). Altering the position of the outline tracing of the lesion boundary by one pixel altered the measured volumes by 22 +/- SD25% (p < 0.05), but ADC values were altered by only 2.9 +/- SD4.9% and ADCr by 2.7 +/- SD4.8% (p = NS). ADC and ADCr values are more reliable and reproducible than DWI lesion size in acute ischemic stroke because altering where the lesion boundary is measured has a much greater impact on lesion volume than on the ADC or ADCr. This effect is greatest in large lesions.     

How does brain MRI lesion volume change on serial scans in patients with multiple sclerosis?

Although lesion load changes on conventional T₂-weighted brain magnetic resonance imaging (MRI) scans from patients with multiple sclerosis (MS) are used to monitor the effect of treatment, there is no clear definition of how lesion load changes over years according to the lesion load present at a baseline evaluation. In the present study, we evaluated the relationship between lesion load changes over time and lesion load at a baseline evaluation in a group of untreated patients with MS. We scanned nineteen patients on two separate occasions with a mean interval 16.4 months between the two examinations. In each scanning session, a scan with forty contiguous 3-mm-thick axial slices was acquired. We assessed MRI lesion loads using a semi-automated local thresholding technique. Both a linear (p < 0.0001) and a quadratic component (p = 0.0008) of the baseline volume were significant in describing the follow-up volume. The equation to model this finding was as follows: V_f = β₀ V_b + β₁ (V_b)², where V_f is the lesion volume at follow-up, V_b is the lesion volume at baseline, β₀ = 0.834 (SE = 0.098), and β₁ = 0.014 (SE = 0.003) (mL)⁻¹. Our data indicate that lesion volume changes detectable on serial brain MRI studies from patients with MS are dependent on the extent of lesion burden present on the baseline MRI scans. This finding has to be considered when planning phase III trials.     

Detecting cortical lesions in multiple sclerosis at 7 T using white matter signal attenuation

Cortical lesions have recently been a focus of multiple sclerosis (MS) MR research. In this study, we present a white matter signal attenuating sequence optimized for cortical lesion detection at 7 T. The feasibility of white matter attenuation (WHAT) for cortical lesion detection was determined by scanning eight patients (four relapsing/remitting MS, four secondary progressive MS) at 7 T. WHAT showed excellent gray matter-white matter contrast, and cortical lesions were hyperintense to the surrounding cortical gray matter, The sequence was then optimized for cortical lesion detection by determining the set of sequence parameters that produced the best gray matter-cortical lesion contrast in a 10-min scan. Despite the B1 inhomogeneities common at ultra-high field strengths, WHAT with an adiabatic inversion pulse showed good cortical lesion detection and would be a valuable component of clinical MS imaging protocols.     

Computer-aided quantification of focal cartilage lesions of osteoarthritic knee using MRI

Noninvasive assessment of articular cartilage using magnetic resonance imaging (MRI) has gained popularity in the diagnosis of osteoarthritis (OA), a condition that affects 20 million Americans. Focal cartilage lesions, a defect found in roughly 19% of the OA population, currently can only be evaluated with confidence using minimally invasive arthroscopy. This article presents a computer-aided procedure using MRI to quantify focal cartilage lesions and aims to support clinical practices of diagnosis and monitoring of lesion progress. Upon a local minima search for identifying focal lesions, the proposed gradient peak method outlines lesion boundaries and then generates morphological properties, such as lesion volume and lesion area. The procedure was evaluated using simulated and in vivo data. First, a simulated lesion was created and analyzed, and the results were compared with the exact solutions. Second, an in vivo evaluation was carried out on seven human knees in which nine focal lesions were identified and quantified. Three of the subjects had follow-up analyses, at either 1 or 2 years. Finally, in an attempt to characterize local biochemical changes underlying focal lesions, MR-derived T2 values of defective cartilage within the lesion boundaries were examined and compared with the values of adjacent cartilage compartments.     

Deep tissue microscopic imaging of the kidney with a gradient-index lens system

Intravital microscopy using two-photon excitation is proven to be a valuable tool for studying the kidney and associated disease processes. However, routine performance of intravital kidney imaging is limited by the fact that fluorescence signal is attenuated by the tissue and at certain tissue depth lost its strength completely. For most of the animal tissues, this finite imaging depth is limited to a few hundred microns. Currently it is not possible to non-invasively image the kidney beyond the superficial tissue layers of the cortex. This has imposed significant limitations on the animal models one can use for imaging since structure such the glomerulus is typically located below the superficial layer of the cortex that cannot be imaged using a conventional fluorescence microscope. Here we report the use of a needle-like lens system based on gradient-index (GRIN) microlenses capable of transferring high quality fluorescence images of the tissue through a regular microscope objective for deep tissue imaging of the kidney. By combining this GRIN lens system with a Zeiss LSM 510 NLO microscope, we are able to extend the depth for imaging kidney tissues far beyond the few hundred microns limit. This GRIN lens imaging system provides an alternative microendoscopic imaging tool that will enhance current intravital kidney imaging techniques for studying structural and functional properties of local tissues at locations below the superficial layers of the kidney.     

甜瓜尾孢叶斑病的高光谱成像检测

农作物生长发育过程中经常会遭到病虫害等外界因素侵染,如果不能实施有效的监测诊断和科学的防治,极易引起农药喷洒不当或过量,不仅会影响作物的产量和种植户的经济效益,还会造成严重的环境污染。近年在广西大棚厚皮甜瓜上发生了一种严重的由瓜类尾孢（Cercospora citrullina）引起的甜瓜叶斑病,导致甜瓜减产和种植户的经济损失。故此应用高光谱成像开展甜瓜叶片的尾孢叶斑病检测,获取健康甜瓜叶片和受瓜类尾孢感染的具有不同病变程度的甜瓜叶片在380~1 000和900~1 700 nm的高光谱图像,选取感兴趣区域并获取相应的平均光谱反射率,比较发现健康叶片和不同病变程度叶片染病区域的平均反射率差异显著。在540 nm处附近,健康叶片和病变程度轻微的叶片的光谱具备波峰形态,随着病变程度增加,波峰逐渐消失;在700~750 nm处附近,叶片反射率曲线急剧上升,出现绿色植物光谱曲线显著的“红边效应”特征;750~900 nm范围,健康叶片与轻微病变区域的光谱反射率变化趋于平稳,而其他病变区域的反射率呈上升趋势,且健康叶片的反射率高于病变区域,反射率随病变程度增加而下降,这一变化规律一直持续到近红外波段的900~1 350 nm范围。运用主成分分析、最小噪声分离法观察叶片早期病变的特征,经主成分分析和最小噪声分离法处理后,特别是对于早期病变,样本受感染后发病的区域更为明显。基于高光谱图像提取的前三个主成分得分绘制三维散点图,虽然不同病变程度的部分样本有重叠,但病变样本与健康样本的分布区分明显。应用K-近邻法和支持向量机方法建立叶片病变判别模型,结果显示：KNN模型对健康样本测试集判别率为98.7%,病变样本的判别率随病变程度加重而逐渐升高;对病变程度较轻样本,支持向量机模型相比于KNN模型而言,判别正确率更高、分类效果更好;总体上,高光谱图像对健康样本的判别率较高（>97%）,可用于健康样本与病变样本的识别,但对不同病变程度的区分效果欠佳。研究结果表明,高光谱成像可用于甜瓜尾孢叶斑病的检测,对不同病变程度的区分效果仍有待提高。     

Determination of relaxation characteristics during preacute stage of lysophosphatidyl choline-induced demyelinating lesion in rat brain: an animal model of multiple sclerosis

Relaxation time measurements were carried out during the preacute stage of lesion progression in an animal model of demyelination created in the internal capsule (ic) area of the rat brain using lysophosphatidyl choline (LPC). T1 and T2 were determined both before and after 36 h of lesion creation. Histology carried out on the rats after MR measurements showed focal demyelinating lesion and surrounding edema with prominent infiltration of inflammatory cells. Both T1 and T2 were statistically higher for the lesion compared to that determined before lesion creation. Percentage increase in T2 was found to be higher by approximately 45% compared to before lesion creation while T1 showed about 25% increase. Increase in T1 and T2 may be attributed to the early acute inflammatory response due to LPC. The beginning of the inflammatory response following LPC injection may also be a contributing factor. The study demonstrates that the quantitative estimate of MR relaxation provides useful information on the pathological events occurring during the early phase of the progression of demyelination.     

Lesion location inside live tissues using the scattering of polarized light

The temporal intensity distributions of the transmitted light through the tissue with lesion structures are investigated using the polarized Monte Carlo technique. Simulation results show that time-resolved curves of transmitted light change obviously for different lesion structures. When the lesion thickness increases, the intensity of transmitted light decreases for co-polarization detection and increases for cross-polarization detection. With the increase of the lesion depth, the amplitude rises for both co- and cross-polarization detection. A method considering the dependence of the peak temporal distribution on the lesion position is thus proposed to locate lesions inside live tissues.     

基于同步辐射显微CT的肾结石微观结构特征研究

肾结石是全球的泌尿系统常见病、多发病,且复发率高居不下。一般认为,尿中结石晶体的盐类呈超饱和状态,以及尿中抑制晶体形成物质不足是肾结石产生的主要因素。肾结石病因较复杂,目前提出了多种有关肾结石病因的学说,主要是从人体种族遗传、疾病、代谢和饮食习惯等方面研究结石病因,来推测其导致不同的种类的产生,再针对性制定治疗方案,但临床上肾结石内科治疗效果仍欠佳。积极探索肾结石形成和生长机制,无疑能对科学治疗肾结石有积极的意义。直观观察到结石的内部结构,并根据这些结构特征推测出结石的形成和成长轨迹,是研究肾结石形成和生长机制的重要一环。传统的研究手段难以无损获得结石的内部结构,目前未见肾结石微观结构相关报道。高分辨率显微CT特别是同步辐射X射线显微CT的出现,无疑能为这一研究提供先进的检测手段。上海同步辐射光源作为第三代优质同步辐射光源,具有高光子通量、高准直性、高极化性、高相干性及宽频谱范围等特点,其配合高分辨的X射线探测器可实现精确、灵敏的组织结构信息的快速、无损检测,在保持标本完整性的前提下,清晰再现样品内部的三维显微结构,从而克服了传统的二维切片技术存在破坏组织结构的完整性、无法准确获得组织...     

Uncertainties in estimates of lesion detectability in diagnostic ultrasound.

Statistical properties of estimates of focal lesion detectability for medical ultrasonic imaging systems are investigated. Analytic forms for bias and variance of estimates of detectability of a lesion consisting of fully developed speckle embedded within a speckle background are derived. Bias and variance of estimates of detectability are investigated using a computer simulation and experiments on tissue-mimicking phantoms. This work offers a systematic methodology for interpreting measurements on phantoms in order to assess lesion detectability. In addition, it provides useful results which may be used to improve design of phantoms and experiments for imaging-system performance assessment.     

Impact of cavitation on lesion formation induced by high intensity focused ultrasound

High intensity focused ultrasound(HIFU) has shown a great promise in noninvasive cancer therapy. The impact of acoustic cavitation on the lesion formation induced by HIFU is investigated both experimentally and theoretically in transparent protein-containing gel and ex vivo liver tissue samples. A numerical model that accounts for nonlinear acoustic propagation and heat transfer is used to simulate the lesion formation induced by the thermal effect. The results showed that lesions could be induced in the samples exposed to HIFU with various acoustic pressures and pulse lengths. The measured areas of lesions formed in the lateral direction were comparable to the simulated results, while much larger discrepancy was observed between the experimental and simulated data for the areas of longitudinal lesion cross-section. Meanwhile,a series of stripe-wiped-off B-mode pictures were obtained by using a special imaging processing method so that HIFUinduced cavitation bubble activities could be monitored in real-time and quantitatively analyzed as the functions of acoustic pressure and pulse length. The results indicated that, unlike the lateral area of HIFU-induced lesion that was less affected by the cavitation activity, the longitudinal cross-section of HIFU-induced lesion was significantly influenced by the generation of cavitation bubbles through the temperature elevation resulting from HIFU exposures. Therefore, considering the clinical safety in HIFU treatments, more attention should be paid on the lesion formation in the longitudinal direction to avoid uncontrollable variation resulting from HIFU-induced cavitation activity.     

时间反转聚焦在组织中形成损伤的数值建模

为考察基于时间反转方法的高强度聚焦超声治疗在预设目标点处的组织损伤情况,使用三维有限差分算法求解Westervelt方程,建立非线性声波传播数值模型,采用97阵元相控阵结合虚拟源的时间反转方法进行超声聚焦,分析其形成的声场和热场,并考察目标点偏离轴线时的组织损伤形成规律。结果表明随着目标点偏轴距离的增大,声压旁瓣开始增多。旁瓣的温升较低,不足以形成组织损伤。时间反转方法可用于多点聚焦,在一定的范围内,形成多点目标损伤而不产生额外的周围组织损伤。同时多点聚焦可以形成一个较大的损伤区域,减少超声治疗时间。     

Direct EPR Detection of Nitric Oxide in Mice Infected with the Pathogenic Mycobacterium Mycobacterium tuberculosis

It has been shown that treatment of mice preinfected with Mycobacterium tuberculosis with spin NO traps (iron complexes with diethyldithiocarbamate) enables detection of large amounts of NO in internal organs 2 and 4 weeks after infection (up to 55–57 μmol/kg of wet lung tissue accumulated with spin NO traps during 30 min). The animals were infected with the drug-sensitive laboratory strain H37Rv and a clinical isolate nonrespondent to antituberculous drugs (the multidrug-resistant strain of M. tuberculosis) obtained from a patient with an active form of tuberculosis. Two weeks after infection with the multidrug-resistant strain, the NO level in the lungs, spleen, liver and kidney increased sharply concurrently with slight lesions of lung tissue. A reverse correlation, i.e., low level of NO in the lungs and other internal organs and extensive injury of lung tissue, was established for H37Rv-infected mice. Four weeks after infection, NO production in the lungs increased dramatically for both M. tuberculosis strains resulting in 80–84% damage of lung tissue. The lesion is suggested to be due to the development of defense mechanisms in M. tuberculosis counteracting NO effects.     

Computational determination of radiation damage effects on DNA structure

Molecular dynamics (MD) studies of several radiation originated lesions on the DNA molecules are presented. The pyrimidine lesions (cytosinyl radical, thymine dimer, thymine glycol) and purine lesion (8-oxoguanine) were subjected to the MD simulations for several hundred picoseconds using MD simulation code AMBER 5.0 (4.0). The simulations were performed for fully dissolved solute molecules in water. Significant structural changes in the DNA double helical structure were observed in all cases which may be categorized as: a) the breaking of hydrogen bonds network between complementary bases and resulted opening of the double helix (cytosinyl, radical, 8-oxoguanine); b) the sharp bending of the DNA helix centered at the lesion site (thymine dimer, thymine glycol); and c) the flippingout of adenine on the strand complementary to the lesion (8-oxoguanine). These changes related to the overall collapsing of the double helical structure around the lesion, are expected to facilitate the docking of the repair enzyme into the DNA in the formation of DNA-enzyme complex. The stable DNA-enzyme complex is a necessary condition for the onset of the enzymatic repair process. In addition to structural changes, specific values of electrostatic interaction energy were determined at several lesion sites (thymine dimer, thymine glycol and 8-oxoguanine). This lesion-specific electrostatic energy is a factor that enables repair enzyme to discriminate lesion from the native site during the scanning of the DNA surface.     

Brain MRI lesion load quantification in multiple sclerosis: a comparison between automated multispectral and semi-automated thresholding computer-assisted techniques

Brain magnetic resonance imaging (MRI) lesion volume measurement is an advantageous tool for assessing disease burden in multiple sclerosis (MS). We have evaluated two computer-assisted techniques: MSA multispectral automatic technique that is based on bayesian classification of brain tissue and NIH image analysis technique that is based on local (lesion by lesion) thresholding, to establish reliability and repeatability values for each technique. Brain MRIs were obtained for 30 clinically definite relapsing-remitting MS patients using a 2.0 Tesla MR scanner with contiguous, 3 mm thick axial, T1, T2 and PD weighted modalities. Digital (Dicom 3) images were analyzed independently by three observers; each analyzed the images twice, using the two different techniques (Total 360 analyses). Accuracy of lesion load measurements using phantom images of known volumes showed significantly better results for the MSA multispectral technique (p < 0.001). The mean intra-and inter-observer variances were, respectively, 0.04 ± 0.4 (range 0.04–0.13), and 0.09 ± 0.6 (range 0.01–0.26) for the multispectral MSA analysis technique, 0.24 ± 2.27 (range 0.23–0.72) and 0.33 ± 3.8 (range 0.47–1.36) for the NIH threshold technique. These data show that the MSA multispectral technique is significantly more accurate in lesion volume measurements, with better results of within and between observers’ assessments, and the lesion load measurements are not influenced by increased disease burden. Measurements by the MSA multispectral technique were also faster and decreased analysis time by 43%. The MSA multispectral technique is a promising tool for evaluating MS patients. Non-biased recognition and delineation algorithms enable high accuracy, low intra-and inter-observer variances and fast assessment of MS related lesion load.     

Ultrasonic absorbed dose,dose rate,and produced lesion volume

Histological preparations of ultrasonically produced lesions in cat brain, at 3 and 4 MHz, have been studied microscopically. The relationship of the delivered acoustic intensity at the lesion site, the energy absorbed per unit volume of the lesion, and the lesion volume is exhibited. It is suggested that universal responses to ultrasonic exposure may exist for different tissues.     

Lesion edge preserved direct average strain estimation for ultrasound elasticity imaging

Elasticity imaging techniques with built-in or regularization-based smoothing feature for ensuring strain continuity are not intelligent enough to prevent distortion or lesion edge blurring while smoothing. This paper proposes a novel approach with built-in lesion edge preservation technique for high quality direct average strain imaging. An edge detection scheme, typically used in diffusion filtering is modified here for lesion edge detection. Based on the extracted edge information, lesion edges are preserved by modifying the strain determining cost function in the direct-average-strain-estimation (DASE) method. The proposed algorithm demonstrates approximately 3.42–4.25 dB improvement in terms of edge-mean-square-error (EMSE) than the other reported regularized or average strain estimation techniques in finite-element-modeling (FEM) simulation with almost no sacrifice in elastographic-signal-to-noise-ratio (SNRe) and elastographic-contrast-to-noise-ratio (CNRe) metrics. The efficacy of the proposed algorithm is also tested for the experimental phantom data and in vivo breast data. The results reveal that the proposed method can generate a high quality strain image delineating the lesion edge more clearly than the other reported strain estimation techniques that have been designed to ensure strain continuity. The computational cost, however, is little higher for the proposed method than the simpler DASE and considerably higher than that of the 2D analytic minimization (AM2D) method.