基于非均匀颅骨头模型的电阻抗断层成像图像重构

目的 研究非均匀颅骨对脑部电阻抗断层成像(EIT)的影响,以提高重构图像的质量.方法 提出一种基于非均匀颅骨头模型的二维动态EIT成像算法,对脑出血病灶进行成像,并依据本文提出的图像质量评价指标,将重构结果与采用均匀圆头模型和4层同心圆头模型的脑出血成像结果进行了比较. 结果 采用非均匀颅骨头模型时,重构图像的相关性与目标定位准确性均有明显提高. 结论 结合颅骨非均匀性进行图像重构是一种有效的提高脑部EIT成像质量的方法.     

基于电阻抗断层成像的非均匀电导率颅骨物理模型研究

目的 用非均匀电导率分布的颅骨模型进行电阻抗断层成像(EIT)实验,分析颅骨电导率非均匀分布对成像结果的影响.方法 选用石膏材料制作非均匀电导率的颅骨模型,用此模型模拟头颅进行EIT目标成像,并将结果与均匀电导率颅骨模型的成像结果进行比较.结果 相对于均匀电导率模型,在非均匀电导率模型内成像目标更加远离电导率较低一侧,且所在位置边界电压扰动量降低.结论 颅骨模型的电导率非均匀分布对成像定位有明显影响,需要在成像算法上做进一步改进.     

Image Quality Required for the Diagnosis of Skull Fractures Using Head CT: A Comparison of Conventional and Improved Reconstruction Kernels

BACKGROUND AND PURPOSE:Although skull fractures are generally assessed on bone images obtained by using head CT, the combined multikernel technique that enables evaluation of both brain and bone through a change in the window settings of an image set has been reported. The purpose of this retrospective study was to determine the image quality required for the accurate assessment of skull fractures by using head CT.MATERIALS AND METHODS:A random sample of 50 patients (25 nonfracture and 25 simple nondisplaced skull fractures) was selected, and sets of conventional brain and bone images and improved combined multikernel images were reconstructed (4614 images). Three radiologists indicated their confidence levels regarding the presence of skull fractures by marking on a continuous scale for each image set. The mean area under the receiver operating characteristic curve was calculated for each kernel, and the statistical significance of differences was tested by using the Dorfman-Berbaum-Metz method.RESULTS:Although a difference in the diagnostic performance of the 3 radiologists was suggested, the mean area under the curve value showed no significant differences among the 3 reconstruction kernels (P = .95 [bone versus combined]), P = .91 [bone versus brain]), and P = .88 [brain versus combined]). However, the quality of brain images was distinctly poorer than the quality of the other 2 images.CONCLUSIONS:There was no significant difference in the diagnostic performance of brain, bone, and combined multikernel images for skull fractures. Skull fracture diagnosis is made possible by brain image assessments. Combined multikernel images offer the advantage of high-quality brain and bone images.

The quality of CT images reconstructed with conventional filtered back-projection depends on the type of reconstruction kernel used. In head CT, low-pass filter kernels that decrease higher spatial frequencies and noise are generally used to reconstruct brain images, whereas high-pass filter kernels that preserve higher spatial frequencies and increase noise are generally used to reconstruct bone images.^1,2 In all cases, the reconstruction of brain images is required. In contrast, according to the policy of each institution, bone images are reconstructed either in all cases or only for patients with clinically suspected bone disease. Because assessment of bone tissue is not required for all cases, worthless images increase if there is reconstruction for all cases. However, when bone images are reconstructed only in case of clinical suspicion, additional reconstruction is required if the need for bone images is determined after examination (in the situation of assessing brain images) or if the radiology technician forgets to reconstruct before sending the images (despite reconstruction of bone image being ordered in advance). Furthermore, bone image reconstruction is not possible once the raw data are deleted from the CT device. Although observers have to assess the bone tissue on brain images reconstructed by low-pass filter kernels in such cases, to our knowledge, the diagnostic performance for bone lesions has not been reported.To resolve this issue, the usefulness of a combined multikernel technique that enables the evaluation of both brain and bone through a change in the window settings of an image set for the assessment of skull fractures has been reported.^3,4 The use of this technique not only decreases the number of stored images and simplifies head CT examinations, but also enables the assessment of bone tissue in all cases. However, the diagnostic performance of this technique has not been sufficiently investigated.The purpose of this study was to determine the CT image quality required for the assessment of skull fractures by using receiver operating characteristic (ROC) analysis of different reconstruction kernels and to evaluate the diagnostic performance of the combined multikernel technique for skull fractures.     

构建国人头颈三维有限元模型

目的研究构建国人头颈三维有限元模型。方法依据正常国人头颅CT、MRI断层扫描图像，识别确定重建对象，对皮肤、颅骨采用灰度阈值法、轮廓跟踪算法及B样条曲线拟合法进行自动重建；对其他结构采用人机对话方式提取边界关键点，进行重建实体。定义结构材料参数后划分网格。筛选相邻体积交接面节点，粘连节点完成建模。结果完成包含皮肤、颅骨、硬膜、静脉窦、脑灰白质、脑干、小脑、脑室系统、颈椎及颈髓的国人头颈三维有限元模型。模型单元及节点数分别为168733，80535，总质量约5．14kg。结论利用医学影像资料，采用轮廓跟踪算法等数字图像技术可半自动实现人颅脑复杂结构的三维重建。     

MRI和CT图像融合构建头面部分层网格模型的研究

目的:分层构建头面部软、硬组织三维网格模型,探讨其在计算机辅助手术中的应用价值.方法:依据正常人头面部MRI和三维CT断层扫描图像,进行MRI与CT图像的融合,识别确定重建对象,对皮肤、皮下组织及骨组织采用灰度阈值法进行自动重建;采用MIMICS软件对获取的医学信息进行分层网格划分,完成建模.结果:完成了包含皮肤、皮下组织和骨组织的正常人头面部三维网格模型.模型单元及节点数分别为皮肤层36524个单元,18263个节点;皮下层38954个单元,19247个节点;头颅68722个单元,33689个节点.结论:利用医学影像资料的图像融合,采用MIMICS软件等数字图像技术可实现人头面部复杂结构的精确三维重建和分层网格划分.     

Difference of Gaussians revolved along elliptical paths for ultrasound fetal head segmentation

We present a fully automatic method to segment the skull from 2-D ultrasound images of the fetal head and to compute the standard biometric measurements derived from the segmented images. The method is based on the minimization of a novel cost function. The cost function is formulated assuming that the fetal skull has an approximately elliptical shape in the image and that pixel values within the skull are on average higher than in surrounding tissues. The main idea is to construct a template image of the fetal skull parametrized by the ellipse parameters and the calvarial thickness. The cost function evaluates the match between the template image and the observed ultrasound image. The optimum solution that minimizes the cost is found by using a global multiscale, multistart Nelder–Mead algorithm. The method was qualitatively and quantitatively evaluated using 90 ultrasound images from a recent segmentation grand challenge. These images have been manually analyzed by three independent experts. The segmentation accuracy of the automatic method was similar to the inter-expert segmentation variability. The automatically derived biometric measurements were as accurate as the manual measurements. Moreover, the segmentation accuracy of the presented method was superior to the accuracy of the other automatic methods that have previously been evaluated using the same data.     

Schussbedingtes Schädel-Hirn-Trauma

Gunshot injuries to the head usually present special findings due to the anatomical conditions of the head (brain enclosed in a relatively solid skull capsule). From a physical wound ballistic view the brain is a very inelastic and incompressable object/tissue. In general this is the reason why gunshots to the head lead to lethal fluid dynamic effects even when no vitally important structures have been directly injured. Severe brain injuries can occur even distant from the wound canal mainly due to distensional and shearing forces during the development of the temporary wound cavity. The lower the cross-sectional density and the more energy a bullet has, the more these effects will be pronounced. Even gunshots with caliber 9 mm Luger can result in hydraulic pressure effects with development of complex fracturing of the skull.     

CT和MRI三维定位在神经导航立体定向系统中的应用

目的：为神经导航定位系统提供最精确的医学影像资料，提高神经外科手术的质量和成功率。材料和方法：结合医学影像的薄层扫描和三维重建技术，调整CT和MRI导航定位扫描中的各项参数。结果：确定了神经导航立体定向系统的CT和MRI定位扫描步骤及参数，为临床提供了精确的影像资料，共完成25例病例的手术治疗，效果满意。结论：精确的医学影像资料是神经导航定位系统准确性的重要保证。     

Normalized accurate measurement of longitudinal brain change

PURPOSE: Quantitative measurement of change in brain size and shape (e.g., to estimate atrophy) is an important current area of research. New methods of change analysis attempt to improve robustness, accuracy, and extent of automation. A fully automated method has been developed that achieves high estimation accuracy. METHOD: A fully automated method of longitudinal change analysis is presented here, which automatically segments brain from nonbrain in each image, registers the two brain images while using estimated skull images to constrain scaling and skew, and finally estimates brain surface motion by tracking surface points to subvoxel accuracy. RESULTS AND CONCLUSION: The method described has been shown to be accurate ( approximately 0.2% brain volume change error) and to achieve high robustness (no failures in several hundred analyses over a range of different data sets).     

Optimised PET reconstruction of the head and neck area: improved diagnostic accuracy

Purpose Reconstruction parameters are an important factor in PET image quality. In the head and neck area, where the level of photon attenuation is relatively low, standard whole-body reconstruction (SWR) parameters may lead to suboptimal results. The purpose of this study was to evaluate the impact of optimised head and neck reconstruction (OHR) parameters on image quality and diagnostic accuracy, using pathology as the gold standard.Methods SWR parameters consisted of 2 iterations, 8 subsets and a 6-mm Gaussian filter. Predetermined OHR parameters were 4 iterations, 16 subsets and a 5-mm Gaussian filter, generating images with increased spatial and contrast resolution but also with increased noise. SWR- and OHR-based FDG-PET images of 28 patients with malignancies in the head and neck area were evaluated for primary tumour and pathological lymph nodes. Diagnostic accuracy was determined by histopathological verification after lymph node dissection.Results Using OHR, sensitivity for detection of a primary tumour increased from 92% to 100%. Eleven additional lymph nodes were visualised in eight patients, resulting in an increased sensitivity for lymph node metastases from 11% to 44%. Specificity decreased from 89% to 74% owing to visualisation of small reactive lymph nodes. In total, using OHR, FDG-PET diagnosis improved in six patients (21%) at the expense of three additional false positives for lymph node metastasis (11%). Primary tumour SUV_max increased by 42%, indicating enhanced contrast resolution.Conclusion Image reconstruction adapted to low photon attenuation in the head and neck area may improve image quality and the diagnostic value of FDG-PET, despite a slightly higher false positive rate attributable to the fact that visualisation of FDG accumulation in benign reactive lymph nodes is also enhanced.     

螺旋CT重建技术在颅脑外伤中的应用

目的：探讨螺旋CT重建技术在颅脑外伤中的应用价值。方法：15例颅脑外伤患者，利用三维(3D)重建软件(SSD)、二维重建(MPR)显示颅脑外伤病灶。结果：3D软件的最大密度投影(MIP)对颅顶部骨折显示良好，脑表面重建软件可清楚显示硬膜外出血的范围和与脑沟、脑回的关系。结论：螺旋CT重建技术可为临床提供更多有价值的信息，可充分发挥高挡CT机的作用。     

Large scan field, high spatial resolution flat-panel detector based volumetric CT of the whole human skull base and for maxillofacial imaging

OBJECTIVES: To assess the feasibility of flat-panel detector based volumetric CT (fpVCT) scanning of the whole human skull base and maxillofacial region, which has thus far only been demonstrated on small, excised specimens. Flat-panel detectors offer more favourable imaging properties than image intensifiers. It is therefore likely that they will replace them in cone-beam CT scanners that are currently used to scan parts of the skull base and maxillofacial region. Furthermore, the resolution of current CT imaging limits diagnosis, surgical planning and intraoperative navigation within these regions. fpVCT might overcome these limitations because it offers higher resolution of high contrast structures than current CT. METHODS: Three embalmed cadaver heads were scanned in two scanners: an experimental fpVCT that offers a scan field large enough for a whole human head, and in a current multislice CT (MSCT). 28 structures were compared. RESULTS: Both scanners produced bone images of diagnostic quality. Small high contrast structures such as parts of the ossicular chain and thin bony laminas were better delineated in fpVCT than in MSCT. fpVCT of maxillofacial region and skull base was rated superior to MSCT (P=0.002) as found in this limited, experimental study. CONCLUSIONS: High spatial resolution fpVCT scanning of both regions in a whole human head is feasible and might be slightly superior to MSCT. fpVCT could improve diagnostic accuracy in selected cases, as well as surgical planning and intraoperative navigation accuracy.     

Quantitative analysis of errors in fractionated stereotactic radiotherapy

Fractionated stereotactic radiotherapy (FSRT) offers a technique to minimize the absorbed dose to normal tissues; therefore, quality assurance is essential for these procedures. In this study, quality assurance for FSRT of 58 cases, between August 1995 and August 1997 are described, and the errors for each step and overall accuracy were estimated. Some of the important items for FSRT procedures are: accuracy in CT localization, transferred image distortion, laser alignment, isocentric accuracy of linear accelerator, head frame movement, portal verification, and various human errors. A geometric phantom, that has known coordinates was used to estimate the accuracy of CT localization. A treatment planning computer was used for checking the transferred image distortion. The mechanical isocenter standard (MIS), rectilinear phantom pointer: (RLPP), and laser target localizer frame (LTLF) were used for laser alignment and target coordinates setting. Head-frame stability check was performed by a depth confirmation helmet (DCH). A film test was done to check isocentric accuracy and portal verification. All measured data for the 58 patients were recorded and analyzed for each item. 4-MV x-rays from a linear accelerator, were used for FSRT, along with homemade circular cones with diameters from 20 to 70 mm (interval: 5 mm).

The accuracy in CT localization was 1.2 ± 0.5 mm. The isocentric accuracy of the linear accelerator, including laser alignment, was 0.5 ± 0.2 mm. The reproducibility of the head frame was 1.1 ± 0.6 mm. The overall accuracy was 1.7 ± 0.7 mm, excluding human errors.     

In vivo 7Li NMR imaging and localized spectroscopy of rat brain.

Lithium-7 in vivo NMR spectroscopy and imaging techniques have been developed at 4.7 T for rat head. The pharmacokinetics of lithium (Li) uptake in rat head has been measured using STEAM localized spectroscopy for the whole brain, which showed relatively rapid uptake of Li and a steady level of Li from about 5 to 20 h. Localized spectroscopy on brain sections revealed no differences in Li concentration among the front, middle, and rear of the brain. The spin-lattice relaxation time showed a single exponential decay for the head. The spin-spin relaxation time for head showed a biexponential behavior. Using a 1H-7Li double coil assembly, 7Li images were generated for rat head, as was the corresponding 1H image for anatomic localization. The 7Li image (7-mm slice thickness, 4-mm in-plane resolution) recorded after the last dose in a multiple ip dose protocol shows the Li distribution in the head and neck. Based on 7Li images, the Li level in muscle was about twice that in the brain. Variations of 7Li intensity level across the brain were typically small.     

Evaluation of clinical usefulness of Web-based results on distribution of brain MRI

We evaluated clinical usefulness of MD online Image Match with the clinical images of 70 intracranial lesions. Total diagnostic accuracy and image similarity between the clinical image and search results was better with enhanced-T1WI. In all sequence, localization was matched precisely in more than 90% of cases. MDOL Image Match was thought to be useful for enhancing the quality of brain MRI diagnosis.     

Influence of "optical illusion" on detectability in diagnosis for head CT images: participation of optical illusion of light perception in medical image reading and diagnosis

Even if the visual impression of the photographic density of the brain in head CT images is shown as physically the same, it is known that optical illusions of lightness perception (assimilation, contrast, picture frame effect, etc.) occur and that practical density can be observed psychologically differently, according to differences in the color of the skull and background, and differences in cases (differences in picture pattern). Therefore, in this study, in order to clarify the influence of optical illusion on detectability in diagnosis, the author attempted to compare detectability in four sample cases, consisting of acute cerebral infarction (1), acute epidural hematoma (1), and chronic subdural hematoma (2), using visual subjective evaluation. In the case of acute cerebral infarction, there was no significant difference in detectability between the original image and the virtual images. Further, it clarified that the original head CT image (acute epidural hematoma) with the high-density hematoma recognized at the marginal limited part of the brain was inferior to virtual images in detectability, while it clarified that the original head CT image (chronic subdural hematoma) with the low-density hematoma was superior to virtual images in detectability, because of visual psychological emphasis on the difference of the film contrast between the hematoma and white skull.     

利用3D打印颅脑辐射等效体模进行个性化适形放疗的剂量验证

目的 建立利用3D打印颅脑辐射等效体模对患者进行个性化放疗剂量验证的方法,为三维适形放射治疗安全提供一种可靠的剂量保证手段。方法 采集两例患者（患者1和患者2）的CT图像数据,基于患者1的图像数据,重建其颅骨与脑组织,制作颅脑体模,验证颅骨与脑组织的等效材料。基于患者2的图像数据,根据3D图像重建并选用组织等效材料重建完全的头颅结构,采用3D打印技术制作全头颅体模。通过对目标区域插入电离室剂量仪并行放射治疗方案,获得头颅体模病灶部的剂量,验证和校准实际放疗计划的安全性。结果 对所获两个体模分别进行DR、CT成像,颅脑体模的等效骨骼与患者1骨骼的X射线灰度值差异为13 721,颅脑体模的等效脑组织与患者1的脑组织的CT值差异为35~40 HU,全头颅体模等效颞肌与患者2的颞肌组织的CT值差异为18~28 HU,影像数据表明体模材质的辐射等效性与人体组织近似,并且等效剂量分布符合常规治疗范围,体模的剂量验证可以有效验证放疗计划系统的准确性。结论 基于3D打印和组织等效技术所设计的个性化放疗体模,可应用于个性化放射治疗验证。体模制作方法简单快速,个性化程度高,为三维适形放射治疗安全提供一种可靠的剂量保证手段。     

Computerized tomography using the EMI general purpose scanner

The EMI general Purpose Scanner is briefly described, with particular reference to the use of window height and window width variations. Patient preparation in relation to movement artefacts and contrast medium is considered, and a method of localization of tomographic sections is described. The Scanner produces brain examinations of high quality. Because a head water bath is no longer required, the base of the skull can also be examined. In the thorax computerized tomography is particularly valuable in showing pleural disease in the forms of thickening, plaques or tumours, and in demonstrating retrosternal lymph node enlargement. Small peripheral metastases can be identified when not shown by conventional tomography. In the abdomen lymph node masses, retroperitoneal tumours and pancreatic disease has been identified, often more completely than by other methods, or where other methods have failed. This has proved particularly valuable in the grading of malignant disease and in the monitoring of subsequent treatment. It is particularly helpful in the planning of radiotherapy. Metastases in liver and bone can be clearly defined when still quite small (0-5.1 cm), but comparison with other methods of diagnosis such as grey scale ultrasound and isotope scanning will be needed before the role of computerized tomography in evaluating these lesions is known.     

Does two-segment image reconstruction at 64-section CT coronary angiography improve image quality and diagnostic accuracy?

PURPOSE: To prospectively evaluate the effect of single- versus two-segment image reconstruction on image quality and diagnostic accuracy at 64-section multidetector computed tomographic (CT) coronary angiography by using conventional coronary angiography as the reference standard. MATERIALS AND METHODS: The study design was approved by a human research committee; patients gave informed consent. The study was HIPAA compliant. Forty consecutive patients (22 men, 18 women; mean age, 61 years +/- 8 [standard deviation]) underwent both 64-section multidetector CT coronary angiography and conventional angiography. All data sets were reconstructed by using single- and two-segment image reconstruction algorithms, with resulting temporal resolution of 82.5-165 msec. Two experienced observers independently evaluated image quality and signs of coronary artery disease. A five-level grading scheme was used to grade stenosis (0%, <50%, <70%, <99%, 100%) and image quality (1[unacceptable] to 5[excellent]). Interobserver correlation, Spearman correlation coefficients, and diagnostic accuracy were calculated. RESULTS: Six hundred coronary artery segments were visible on conventional angiograms, of which 560 (93.3%) were seen by using single-segment and 561 (93.5%) were seen by using two-segment image reconstruction (P=.35). Mean quality scores were not significantly different (P=.22) for single- (3.1 +/- 0.9) and two-segment (3.2 +/- 0.8) reconstruction. Significantly (P=.03) better image quality was observed for two-segment reconstruction only at heart rates of 80-82 beats per minute, at which temporal resolution was approximately 83 msec. For grading coronary artery stenosis, correlation was 0.64 for single- and 0.66 for two-segment reconstruction (P=.43). Significant stenosis (>50%) was detected on a per-segment basis with 77.1% sensitivity and 98.6% specificity by using single-segment and with 79.2% sensitivity and 99.1% specificity by using two-segment image reconstruction. CONCLUSION: At heart rates of more than 65 beats per minute, use of two-segment reconstruction improves image quality at multidetector CT coronary angiography but does not significantly affect overall diagnostic accuracy compared with single-segment reconstruction.