How to obtain high-accuracy image registration: application to movement correction of dynamic positron emission tomography data

When registering dynamic positron emission tomography (PET) sequences, the time-dependent changes in uptake pattern prevent registration of all frames to the first frame in a straightforward manner. Instead, a sequential registration of each frame to its predecessor may be used, provided the registration algorithm is completely free of bias. It is shown that most existing algorithms introduce a bias, the size of which depends on the pixel size and the signal-to-noise ratio of the data. The bias is introduced by the pixelisation of the underlying continuous process. All existing cost-functions are more or less sensitive to noise, and the noise reduction resulting from translating one image set relative to the other means that a small movement will always be detected in the cases where no actual movement has occurred. The problem is solved by an initial resampling of the reference volume into a representation with another image and pixel size. If the new representation is sensibly chosen it means that all possible transforms applied to the other image volume will yield approximately the same noise reduction, thereby removing the source of the bias. The described effect is demonstrated on phantom data, and its impact is shown on human data. Received 15 October 1997 and in revised form 9 February 1998     

Image-guided MR spectroscopy volume of interest localization for longitudinal studies

Longitudinal magnetic resonance spectroscopy (MRS) studies require accurate repositioning of the volume of interest (VOI) over which measurements are made. In this work we present and evaluate a method for the image-guided repositioning of brain volumes of interest. The point-based registration technique we developed allows the repositioning to be performed on-line (i.e. while the patient is in the scanner). MR image volumes were acquired from six subjects, three scans each over the course of a month. During the first scan, two spectroscopy VOIs are visually selected: one in the frontal white matter, the other in the superior cerebellar vermis. The coordinates of 13 internal brain landmarks are also identified. During both subsequent scans, the same 13 landmarks are also identified, and the transformation that registers the first set of landmarks to the subsequent set is computed. This result is used to automatically map the position of the spectroscopy VOIs from the first volume to the current volume. For the six subjects evaluated to date, we show an average repositioning error of the spectroscopy VOIs in the order of 1 mm. This accuracy allows us to conclude that any variations in the MR spectra are unlikely to be due to repositioning error.     

Validation of MRI to TRUS registration for high-dose-rate prostate brachytherapy

PurposeThe objective of this study was to develop and validate an open-source module for MRI to transrectal ultrasound (TRUS) registration to support tumor-targeted prostate brachytherapy.Methods and MaterialsIn this study, 15 patients with prostate cancer lesions visible on multiparametric MRI were selected for the validation. T2-weighted images with 1-mm isotropic voxel size and diffusion weighted images were acquired on a 1.5T Siemens imager. Three-dimensional (3D) TRUS images with 0.5-mm slice thickness were acquired. The investigated registration module was incorporated in the open-source 3D Slicer platform, which can compute rigid and deformable transformations. An extension of 3D Slicer, SlicerRT, allows import of and export to DICOM-RT formats. For validation, similarity indices, prostate volumes, and centroid positions were determined in addition to registration errors for common 3D points identified by an experienced radiation oncologist.ResultsThe average time to compute the registration was 35 ± 3 s. For the rigid and deformable registration, respectively, Dice similarity coefficients were 0.87 ± 0.05 and 0.93 ± 0.01 while the 95% Hausdorff distances were 4.2 ± 1.0 and 2.2 ± 0.3 mm. MRI volumes obtained after the rigid and deformable registration were not statistically different (p > 0.05) from reference TRUS volumes. For the rigid and deformable registration, respectively, 3D distance errors between reference and registered centroid positions were 2.1 ± 1.0 and 0.4 ± 0.1 mm while registration errors between common points were 3.5 ± 3.2 and 2.3 ± 1.1 mm. Deformable registration was found significantly better (p < 0.05) than rigid registration for all parameters.ConclusionsAn open-source MRI to TRUS registration platform was validated for integration in the brachytherapy workflow.     

一种人机交互式快速脑图像配准系统

为了推广配准研究在实际临床中的应用,提出并实现了一种脑图像配准系统.与其它自动化配准不同,该系统有意将人机交互引入配准过程,实现了脑图像的快速精确配准,并避免了局部极值等问题.同时,系统包含多种配准测度,适用于不同配准任务.试验表明,该系统配准效率高、能够解决大多数临床脑图像配准问题.     

Geometry driven multimodality matching of brain images

Summary Clinical diagnosis, as well as therapy planning and evaluation, are increasingly supported by multimodal images. There are many instances desiring integration of the information obtained by various imaging devices. This paper describes a new approach to match images of different modalities. Differential operators are used in combination with Gaussian blurring to extract geometric features from the images that correspond to similar structures. The resulting feature images may be used with existing matching techniques that minimize the distance between the features in the images to be matched. Our first application of this new approach concerns matching of MRI and CT brain images. The so-called L operator produces a ridge-like feature image from which in CT and MRI the center curve of the cranium is easily extracted. First results of this operator's performance in matching tasks are shown. Another promising operator is the umbilicity operator, which is presented in combination with SPECT images.This research was supported in part by the Netherlands ministries of Education & Science and Economic Affairs through a SPIN grant, and by the industrial companies Agfa-Gevaert, Philips Medical Systems, and KEMA. The valuable discussions with E. J. D. Pol, B. M. ter Haar Romeny, and L. M. J. Florack are gratefully acknowledged.     

企业职业卫生管理试行注册职业健康主任制度的探讨

目的 为扭转现阶段企业内部职业卫牛管理人员缺乏的困难局面,探讨在广东省试行注册职业健康主任制度的可行性.方法 参照我国近20年来安全生产领域推行注册安全主任的方法,试行注册职业健康主任制度.结果 对注册职业健康主任试点工作、技术支持和行政干预与市场化管理进行探讨.结论 注册安全主任通过职业卫生管理专题培训和考核,取得资格后成为注册职业健康主任是比较可行的.     

Overview of REACH: Issues Involved in the Registration of Metals

New European legislation known as REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) was introduced in 2007 to increase the speed at which the health and/or environmental risks of industrial chemicals were being assessed and managed (REACH (EC) No 1907/2006). REACH consolidated earlier chemicals-control statutes and placed the burden of assessing, and identifying the means to manage risks on industry. This paper details the REACH process for controlling and managing hazardous chemicals and challenges encountered in applying the provisions of REACH and the guidance documents available from European Chemical Agency. Special attention is paid to challenges in evaluating potential health risks of metals such as aluminum and aluminum compounds. Lessons learned from over a decade of experience with REACH legislation are also noted.     

Specific antibody responses of primary cells from different cell sources are able to predict immunotoxicity in vitro

Alternative methods for the prediction of immunotoxicity are highly desirable. However, until now no in vitro test for this purpose has been fully validated or accepted by regulatory authorities. MD cultures are in vitro equivalent to the widely used ex vivo primary T cell dependent antibody responses (TDAR), which has been identified in a regulatory context as a main functional test for immunotoxicological investigations. The purpose of the present study was to use MD cultures of spleen and blood cells to compare data from three different chemicals using SRBC as antigen in two different species. Using this approach we were able to show that cell sources from both rats and mice were able to correctly predict all tested compounds and to clearly distinguish immunosuppressants from control substances. Furthermore, animal studies can be refined by using MD cultures of PBMC. During a 28d benzo(a)pyrene treatment of rats we were able to follow the kinetic of an immune response by in vitro analyses. Additionally evaluation of in vitro antibody responses of spleen cells and PBMC from rats treated with cyclophosphamide revealed similar results compared to the conventional ex vivo plaque forming cell assay (PFCA).In conclusion, investigation of in vitro antibody responses is a sensitive and reliable approach for detection of a compound induced specific effect on the immune system. MD cultures may not only replace the ex vivo TDAR in the future, but their implementation in routine toxicology also enables refinement of existing in vivo studies by reducing the numbers of animals.     

乳房植入体产品注册申报思路

目的对乳房植入体产品注册申报思路及相关资料作一总结。方法查阅相关企业申报乳房植入体产品标准,对所需资料进行总结。结果企业申报乳房植入体医疗器械产品注册资料较繁杂,主要涉及产品技术资料提供、注册产品标准制订、产品的注册检测、说明书的制订等方面。结论生产企业需对乳房植入体的风险具有充分认识,并具有相当的研发技术能力,严格进行风险控制,才能确保产品的安全性和有效性。     

一种医学图像几何特征的自动检测

医学图像配准的方法有许多种，它的原理都是选取合适的图像特征量，根据特征量再来确定配准变换，因此特征量的选取是图像配准的第一步。目前用于配准的图像特征量有多种，如图像边界、图像外标记点等。本文提供了一种提取图像脊特征，作为用于配准的特征量的方法，取得了良好效果。