Simulation of realistic abnormal SPECT brain perfusion images: application in semi-quantitative analysis

Simulation is useful in the validation of functional image analysis methods, particularly when considering the number of analysis techniques currently available lacking thorough validation. Problems exist with current simulation methods due to long run times or unrealistic results making it problematic to generate complete datasets. A method is presented for simulating known abnormalities within normal brain SPECT images using a measured point spread function (PSF), and incorporating a stereotactic atlas of the brain for anatomical positioning. This allows for the simulation of realistic images through the use of prior information regarding disease progression. SPECT images of cerebral perfusion have been generated consisting of a control database and a group of simulated abnormal subjects that are to be used in a UK audit of analysis methods. The abnormality is defined in the stereotactic space, then transformed to the individual subject space, convolved with a measured PSF and removed from the normal subject image. The dataset was analysed using SPM99 (Wellcome Department of Imaging Neuroscience, University College, London) and the MarsBaR volume of interest (VOI) analysis toolbox. The results were evaluated by comparison with the known ground truth. The analysis showed improvement when using a smoothing kernel equal to system resolution over the slightly larger kernel used routinely. Significant correlation was found between effective volume of a simulated abnormality and the detected size using SPM99. Improvements in VOI analysis sensitivity were found when using the region median over the region mean. The method and dataset provide an efficient methodology for use in the comparison and cross validation of semi-quantitative analysis methods in brain SPECT, and allow the optimization of analysis parameters.     

人脑MRI和PET图像的融合方法

目的：研究MRI和PET医学图像融合的方法并且应用在人脑神经解剖中。方法：以Chamfer matching为基本配准方法和以模糊数学为理论基础的融合方法。结果：使得融合后图像有很强的抗配准偏差能力,并且能极大程度地保留原来解剖性信息图像和功能性图像的信息。能根据融合算子的不同组合,得到倾向于不同检查仪器结果的图像。结论：通过本文方法得出的融合后图像,能在人脑解剖结构上显示出该区域的功能状态,对于了解该结构的存在、变异、病变提供了很大的便利。对人脑神经解剖学研究和临床应用都有很大的理论和实践意义。     

A hybrid strategy to integrate surface-based and mutual-information-based methods for co-registering brain SPECT and MR images

Co-registration of brain SPECT and MR images has been used extensively in clinical applications. The complementary features of two major co-registration methods—surface- and mutual-information-based (MI-based)—motivated us to study a hybrid-based scheme that uses the surface-based method to achieve a quick alignment, followed by the MI-based method for fine tuning. Computer simulations were conducted to evaluate the accuracy and robustness of surface-, MI-, and hybrid-based registration methods by designing different levels of noise and mismatch in the registration experiments. Results demonstrated that the hybrid surface-MI-based scheme outperforms both the surface- and MI-based methods in providing superior accuracy and success rates. Specifically, the translational and rotational errors were no more than 1 mm and 2°, respectively, with consistent success rates over 98%. Besides, the hybrid-based method saved 12–53% of the computation efforts, compared with using the MI-based method alone. We recommend the use of hybrid-based method when the orientational differences between the floating and reference images exceed 10°.     

A methodology for evaluation of boundary detection algorithms on breast ultrasound images

Image segmentation is the partition of an image into a set of non-overlapping regions that comprise the entire image. The image is decomposed into meaningful parts, which are uniform with respect to certain characteristics, such as grey level or texture. This study presents a novel methodology to evaluate ultrasound image segmentation algorithms. The sonographic features can differentiate between various sized malignant and benign breast tumours. The clinical experiment can determine whether a tumour is benign or not, based on contour, shape, echogenicity and echo texture. Further study of the standardized sonographic features, especially the tumour contour and shape, will improve the positive predictive value and accuracy rate in breast tumour detection. The effectiveness of using this methodology is illustrated by evaluating image segmentation on breast ultrasound images. Via definite segmentation, the appreciated tumour shape and contour can be ascertained. Furthermore, this method can enhance the ability of ultrasound to distinguish between benign and malignant breast lesions.     

单光子发射型计算机断层成像与CT融合图像评价125I粒子在靶器官中的分布

目的 结合全身扫描,探讨单光子发射型计算机断层成像(SPECT)与CT融合图像对植入的放射性125I粒子在体内分布的评价.方法 2008年5月至2009年6月复旦大学附属中山医院核医学科接受治疗的47例125I粒子植入患者中,6例前列腺癌患者实施了超声诱导下125I粒子植入,另41例有明确肿瘤病史并伴有门静脉或上腔静脉癌栓患者,在数字减影血管成像(DSA)诱导下行支架和125I粒子链条植入到血管腔内.所有患者在125I粒子植入24 h后行全身扫描,再根据125I粒子所在部位行SPECT与CT显像检查.结合全身扫描图像和SPECT与CT图像对植入125I粒子的分布情况进行评价.结果 全身扫描图像为SPECT与CT检查提供准确定位,但无法显示粒子的准确解剖部位.6例前列腺癌患者中,SPECT与CT融合图像显示5例患者植入粒子在前列腺内分布较好,而1例患者粒子植入到右侧精囊腺内;41例有明确肿瘤病史并伴有门静脉或上腔静脉癌栓患者中,SPECT与CT融合图像显示40例血管腔内的粒子链条位于合理的位置,1例植入到上腔静脉内的粒子链条脱离到右心腔内.结论 结合全身扫描,SPECT与CT融合图像可以评价125I粒子在靶器官的分布情况,能及时发现位置偏离的粒子.     

单光子发射型计算机断层成像与CT融合图像评价^125I粒子在靶器官中的分布

目的结合全身扫描,探讨单光子发射型计算机断层成像（SPECT）与CT融合图像对植入的放射性^125I粒子在体内分布的评价。方法2008年5月至2009年6月复旦大学附属中山医院核医学科接受治疗的47例^125I粒子植入患者中,6例前列腺癌患者实施了超声诱导下^125I粒子植入,另41例有明确肿瘤病史并伴有门静脉或上腔静脉癌栓患者,在数字减影血管成像（DSA）诱导下行支架和^125I粒子链条植入到血管腔内。所有患者在^125I粒子植入24h后行全身扫描,再根据^125I粒子所在部位行SPECT与CT显像检查。结合全身扫描图像和SPECT与CT图像对植入^125I粒子的分布情况进行评价。结果全身扫描图像为SPECT与CT检查提供准确定位,但无法显示粒子的准确解剖部位。6例前列腺癌患者中,SPECT与CT融合图像显示5例患者植入粒子在前列腺内分布较好,而1例患者粒子植入到右侧精囊腺内;41例有明确肿瘤病史并伴有门静脉或上腔静脉癌栓患者中,SPECT与CT融合图像显示40例血管腔内的粒子链条位于合理的位置,1例植入到上腔静脉内的粒子链条脱离到右心腔内。结论结合全身扫描,SPECT与CT融合图像可以评价^125I粒子在靶器官的分布情况,能及时发现位置偏离的粒子。     

A system for detecting and describing pathological changes using dynamic perfusion computer tomography brain maps

This paper presents a novel method of detecting and describing pathological changes that can be visualized on dynamic computer tomography brain maps (perfusion CT). The system was tested on a set of dynamic perfusion computer tomography maps. Each set consisted of two perfusion maps (CBF, CBV and TTP for testing the irregularity detection algorithm) and one CT brain scan (for the registration algorithm) from 8 different patients with suspected strokes. In 36 of the 84 brain maps, abnormal perfusion was diagnosed. The results of the algorithm were compared with the findings of a team of two radiologists. All of the CBF and CBV maps that did not show a diagnosed asymmetry were classified correctly (i.e. no asymmetry was detected). In four of the TTP maps the algorithm found asymmetries, which were not classified as irregularities in the medical diagnosis; 84.5% of the maps were diagnosed correctly (85.7% for the CBF, 85.7% for the CBV and 82.1% for the TTP); 75% of the errors in the CBF maps and 100% of the errors in the CBV and the TTP maps were caused by the excessive detection of asymmetry regions. Errors in the CBFs and the CBVs were eliminated in cases in which the symmetry axis was selected manually. Subsequently, 96.4% of the CBF maps and 100% of the CBV maps were diagnosed correctly.     

Significance of 99mTc-ECD SPECT in acute and subacute ischemic stroke: comparison with MR images including diffusion and perfusion weighted images

99mTc-ECD SPECT is valuable for the evaluation of cell viability and function. The purpose of the present study was to evaluate the significance of 99mTc-ECD brain SPECT in ischemic stroke. We compared 99mTc-ECD brain SPECT with perfusion and diffusion weighted images (PWI, DWI). Ten patients with acute and early subacute ischemic stroke were included in this prospective study. T2-weighted images (T2WI), DWI, PWI and 99mTc-ECD SPECT were obtained during both the acute/early subacute and late subacute stages. In the case of PWI, time to peak (TTP) and regional cerebral blood volume (rCBV) maps were obtained. The rCBV map and 99mTc-ECD SPECT images were compared in 8 lesions using DeltaAI. The asymmetry index (AI) was calculated as (Ci - Cc) X 200 / (Ci + Cc); where Ci is the mean number of pixel counts of an ipsilateral lesion and Cc is the mean number of pixel counts of the normal contralateral hemisphere. DeltaAI was defined as AIacute - AIsubacute in the ischemic core and periphery. PWI and 99mTc-ECD SPECT detected new lesions of the hyperacute stage or of evolving stroke more accurately than T2WI and DWI. 99mTc-ECD SPECT was able to localize the infarct core and peri-infarct ischemia in all lesions in both the acute and the subacute stages. DeltaAI was higher in the rCBV map than in the 99mTc-ECD SPECT images in the ischemic core (p = 0.063) and in the periphery (p = 0.091). In the 99mTc-ECD SPECT images, DeltaAI was higher in the ischemic core than in the periphery (p = 0.028). During the subacute stage, 99mTc-ECD SPECT detected all the lesions without the pseudonormalization seen in the MR images of 5/11 lesions. Based on this study, 99mTc-ECD SPECT is comparable to PWI in terms of its ability to detect acute stroke and is more useful than PWI in the case of subacute infarction.     

A comparative study of surface- and volume-based techniques for the automatic registration between CT and SPECT brain images

Image registration of multimodality images is an essential task in numerous applications in three-dimensional medical image processing. Medical diagnosis can benefit from the complementary information in different modality images. Surface-based registration techniques, while still widely used, were succeeded by volume-based registration algorithms that appear to be theoretically advantageous in terms of reliability and accuracy. Several applications of such algorithms for the registration of CT-MRI, CT-PET, MRI-PET, and SPECT-MRI images have emerged in the literature, using local optimization techniques for the matching of images. Our purpose in this work is the development of automatic techniques for the registration of real CT and SPECT images, based on either surface- or volume-based algorithms. Optimization is achieved using genetic algorithms that are known for their robustness. The two techniques are compared against a well-established method, the Iterative Closest Point-ICP. The correlation coefficient was employed as an independent measure of spatial match, to produce unbiased results. The repeated measures ANOVA indicates the significant impact of the choice of registration method on the magnitude of the correlation (F = 4.968, p = 0.0396). The volume-based method achieves an average correlation coefficient value of 0.454 with a standard deviation of 0.0395, as opposed to an average of 0.380 with a standard deviation of 0.0603 achieved by the surface-based method and an average of 0.396 with a standard deviation equal to 0.0353 achieved by ICP. The volume-based technique performs significantly better compared to both ICP (p<0.05, Neuman Keuls test) and the surface-based technique (p<0.05, Neuman-Keuls test). Surface-based registration and ICP do not differ significantly in performance.     

Comparative evaluation of image segmentation methods for volume quantitation in SPECT.

A wide variety of image segmentation techniques have been proposed for the measurement of organ or lesion volumes in SPECT images. Evaluation of the relative performance of the various methods is difficult due to wide variations in system response characteristics, size, shape, and contrast of the imaged objects, and image acquisition and processing techniques. Selected image segmentation methods for volume quantitation in SPECT were applied to a set of simulated SPECT images containing objects ranging in volume from 1.8 to 113.1 cc. The specific segmentation methods included: (1) operator drawn regions of interest, (2) count-based methods, (3) three levels of fixed thresholds, (4) an adaptive threshold (GLH method), (5) a two-dimensional (2-D) edge detection method, and (6) a three-dimensional (3-D) edge detection method. In general, the 3-D edge detection method required minimal operator intervention while providing the most accurate and consistent estimates of object volume across changes in object contrast and size.     

Apolipoprotein E4allele in the normal elderly: neuropsychologic and brain MRI correlates

The presence of the apolipoprotein E e4 allele has been considered to be a risk factor for Alzheimer's disease and vascular dementia. We therefore used demanding neuropsychologic testing and brain MRI to determine if elderly normals with at least one e4 allele demonstrate subclinical changes in cognition and a higher frequency of brain atrophy or silent ischemic brain damage. The study population consisted of 214 randomly selected individuals aged 50 to 75 years without neuropsychiatric or general disease. There were 175 (81.8%) subjects without and 39 (18.2%) with at least one e4 allele. The two groups were comparable for age, length of education, verbal intelligence, mood and major vascular risk factors. Apolipoprotein E e4 carriers performed significantly worse than non-carriers when assessed for learning and memory abilities, while there were no differences in test results of conceptualization, attention, speed of mental processing and visuopractical skills. There were no between-group differences for thromboembolic and lacunar infarcts, white matter hyperintensity grading and the semiautomatically measured white matter hyperintensity area. The extent of sulcal and ventricular widening as well as hippocampal and parahippocampal volumes were also similar between the comparative subsets. We conclude that the apolipoprotein E e4 allele is associated with subtle learning and memory deficits in normal elderly persons and may therefore be suggested a marker for accelerated cognitive aging. In this group of subjects it was not associated with brain parenchymal changes as demonstrated by MRI.     

A lifespan MRI evaluation of ventricular enlargement in normal aging mice

Ventricular enlargement has been proposed as a structural biomarker for the progression of Alzheimer's disease (AD). This biomarker, established in human patients, needs to be translated to animals to facilitate drug development for the disease. However, ventricular enlargement is not exclusive to AD, since the ventricle size increases during normal aging. A longitudinal characterization of ventricular enlargement in normal aging in mice is therefore crucial before further evaluations of mouse models or neurodegenerative diseases associated to brain atrophy. To this end, ventricular enlargement in normal aging mice was characterized over the lifespan (i.e., 2 years). The results showed that the overall ventricle size increased with age, with the expansion beginning during the early life stages and continuing to old age. The reported data represent a biomarker benchmark for normal aging mice under unmodified conditions. This provides a foundation for evaluating the validity of AD mouse models or the effects of potential drugs. The considerable physiological ventricular enlargement during normal aging must be considered in related experiments.     

Implementation and quantitative evaluation of analytical methods for attenuation correction in SPECT: a phantom study.

Three differing exact methods of inverting the two-dimensional (2D) exponential Radon transform were implemented and evaluated quantitatively with a phantom study. The phantom had the shape of a pie-chart divided into six cavities, each 480 ml in volume and 10 cm in height, that were symmetrically positioned in a cylinder that was 20 cm in diameter and 10 cm in height. This phantom tests for linearity between true activity concentration and measured activity concentration, and it is denoted as a linearity phantom in the present study. Each cavity contained a different concentration of a homogeneous solution of 99mTc (74, 148, 222, 296, 370 and 444 kBq ml(-1)). Data acquisition was performed with two energy windows: a 20% photopeak energy window set symmetrically over the 140 keV of 99mTc and a secondary 5% energy window set over the 122 keV peak. We optimized a triple-energy window scatter correction method for a gamma camera-collimator system to obtain accurate scatter-corrected projections. A circular ROI 3 cm in diameter was identified over each cavity region, and count density (counts per pixel) was calculated. This value was converted to activity concentration (kBq ml(-1)) using a cross-calibration coefficient between SPECT counts and the gamma well counter. The relation between true activity (x) and measured activity concentration (y) was fitted to a line using the least-squares method. Regression lines were y = 0.63 + 1.0255x (R2 = 0.9987), y = -2.62 + 1.0278x (R2 = 0.9995), and y = 0.092 + 1.0241x (R2 = 0.9989) for the Bellini, Inouye and Metz-Pan methods respectively. In another phantom study using two different types of phantoms, contrast of a cold region in the two was 96% and 101% for all three methods. Combined optimized scatter correction and analytical attenuation correction methods achieve good accuracy in quantification of activity distribution with a uniform attenuating medium.     

Morphometric evaluation of intracytoplasmic lipid in normal and pathological parathyroid glands

The chief morphological criterion for classifying parathyroid glands as 'normal', 'suppressed', or 'activated' is the lipid content of the cytoplasm. In particular, cytoplasm lipid deposit is scanty in the active parathyroid cell, according to many authors. In this paper we present the results of a morphometrical study of ten normal parathyroid glands from patients undergoing thyroidectomy, 20 enlarged 'adenomatous' glands from patients with primary hyperparathyroidism, and 20 glands of normal size from the same hyperparathyroid patients. We aimed at assessing the content of intracytoplasmic lipid of secretory cells in all these conditions. The results show that secretory cells of adenomatous glands have less lipid than those from normal glands; however, there was considerable overlapping of the data in the two groups. The mean lipid content of cells in glands of normal size taken from hyperparathyroid patients was not significantly different from the mean value of normal cells, even when ultrastructural evidence of activation was present in the former. These data suggest that caution has to be exercised in assessing the functional status of parathyroid glands on the basis of lipid content of secretory cells, mainly when differentiating between adenoma and hyperplasia.     

探索建立颅脑MRI图像、断层标本图像及三维重建图像的对比数据模型

目的利用计算机图像处理系统对颅脑主要重要结构进行三维成像,探索建立1套正常颅脑部MRI图像、断层标本及三维重建图像的数据对照计算机模型,为影像诊断及颅脑部手术定位提供形态依据。方法利用Microsoft Visual Studio将获得的MRI图像、断层标本图像及重建的三维图像建立数据模型。结果建立的数据模型提供了颅脑部正常解剖学影像学对比特点,构建了主要结构的三维立体模型图像,使抽象结构数字化、立体化、可视化,有助于对人脑的理解。结论本数据模型把颅脑结构的三维图像结合到标本MRI的对比图中,有利于初次接触颅脑断层的初学者。     

CXCL12 in normal and pathological pregnancies: A review

The survival of allogeneic fetuses during pregnancy is a rather paradoxical phenomenon with a complex mechanism. Chemokine ligand12 (CXCL12) and its receptors CXC chemokine receptor (CXCR)4 and 7 are extensively found in placenta tissues and cells, including trophoblast cells, vascular endothelial cells, and decidual stromal and decidual immune cells (eg, NK cells and regulatory T cells). Evidence has illustrated that the CXClL12/CXCR4/CXCR7 axis could enhance the cross talk at the maternal‐fetal interface through multiple processes, such as invasion and placental angiogenesis, which appears to be critical signaling components in placentation and fetal outcome. In addition, an increasing number of studies have demonstrated that the CXCL12/CXCR4/CXCR7 axis also stands out for its pleiotropic roles in several pregnancy‐associated diseases (eg, recurrent spontaneous abortion (RSA), pre‐eclampsia (PE), and preterm labor). In the present review, the different biological properties and signaling in physiological and pathological pregnancy conditions of CXCL12/CXCR4/CXCR7 axis were discussed, with the aim of obtaining a further understanding of the regulatory mechanisms and highlighting their potential as a target for therapeutic approaches.     

Asymmetry of human brain in early embryogenesis under normal and pathological conditions

The effect of some developmental abnormalities on the morphogenesis of human brain asymmetry during early embryonic stages was studied. Insignificant predominance of the left hemisphere (1–3%) was revealed in human embryos. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 130, No. 10, pp. 442–444, October, 2000