Unsupervised estimation of myocardial displacement from tagged MR sequences using nonrigid registration.

We propose a fully automatic cardiac motion estimation technique that uses nonrigid registration between temporally adjacent images to compute the myocardial displacement field from tagged MR sequences using as inputs (sources) both horizontally and vertically tagged images. We present a new multisource nonrigid registration algorithm employing a semilocal deformation model that provides controlled smoothness. The method requires no segmentation. We apply a multiresolution optimization strategy for better speed and robustness. The accuracy of the algorithm is assessed on experimental data (animal model) and healthy volunteer data by calculating the root mean square (RMS) difference in position between the estimated tag trajectories and manual tracings outlined by an expert. For the approximately 20000 tag lines analyzed (45 slices over 20-40 time frames), the RMS difference between the automatic tag trajectories and the manually segmented tag trajectories was 0.51 pixels (0.25 mm) for the animal data and 0.49 pixels (0.49 mm) for the human volunteer data. The RMS difference in the separation between adjacent tag lines (RMS_TS) was also assessed, resulting in an RMS_TS of 0.40 pixels (0.19 mm) in the experimental data and 0.52 pixels (0.56 mm) in the volunteer data. These results confirm the subpixel accuracy achieved using the proposed methodology.     

A phantom study of the accuracy of CT, MR and PET image registrations with a block matching-based algorithm

PURPOSE: The aim of the present study was to quantitatively assess the performance of a block matching-based automatic registration algorithm integrated within the commercial treatment planning system designated ISOgray from Dosisoft. The accuracy of the process was evaluated by a phantom study on computed tomography (CT), magnetic resonance (MR) and positron emission tomography (PET) images. MATERIALS AND METHODS: Two phantoms were used to carry out this study: the cylindrical Jaszczak phantom and the anthropomorphic Liqui-Phil Head Phantom (the Phantom Laboratory), containing fillable spheres. External fiducial markers were used to quantify the accuracy of 41 CT/CT, MR/CT and PET/CT automatic registrations with images of the rotated and tilted phantoms. RESULTS: The study first showed that a cylindrical phantom was not adapted for the evaluation of the performance of a block matching-based registration software. Secondly, the Liqui-Phil Head Phantom study showed that the algorithm was able to perform automatic registrations of CT/CT and MR/CT images with differences of up to 40 degrees in phantom rotation and of up to 20-30 degrees for PET/CT with accuracy below the image voxel size. CONCLUSION: The study showed that the block matching-based automatic registration software under investigation was robust, reliable and yielded very satisfactory results. This phantom-based test can be integrated into a periodical quality assurance process and used for any commissioning of image registration software for radiation therapy.     

基于梯度矢量流与粒子群优化算法的多模态医学图像配准

目的研究用梯度矢量流与粒子群优化算法实现多模态医学图像配准,提高配准的精度。方法算法对图像配准的特征空间、相似性测度、搜索策略3个方面进行改进：先由原始图像产生梯度矢量流场,作为配准的特征空间;然后提出并计算3种基于梯度矢量流场的相似性测度;最后使用结合了遗传算法交叉机制的粒子群优化算法找到两幅图像的最优变换。结果对仿真及实际医学图像的54次配准实验,表明该方法配准精度优于基于像素的粒子群优化方法和Walsh变换法。结论基于梯度矢量流与粒子群优化算法的图像配准方法能有效地实现多模态医学图像的配准。     

An Alternative Technique for an Accurate Implant-Retained Prosthesis Impression

A technique is described to help ensure the accurate reproduction of rigid implant components and the edentulous soft tissue. Splinted implant impression copings are luted together with resin to a specially designed custom tray.     

多分辨率的数字减影图像配准算法

提出基于小波变换的图像配准算法是一种多分辨率匹配算法。该算法可以利用数字减影图像在不同层次上的相似性,配准精度从低至高逐步提高,同时有效地减少运动矢量的搜索复杂度,较好地解决了运算量和检测精度之间的矛盾。该方法被证明是以指数衰减收敛的。整个配准过程在不牺牲配准效果的前提下,提高了匹配速度以及一致性。     

宫颈癌内外照射后放射性直肠损伤临床预测模型的研究

目的 探讨宫颈癌内外照射放疗不同剂量叠加方式的剂量学差异,建立宫颈癌放疗后慢性放射性直肠损伤(RLRI)的临床预测模型。方法 回顾性分析2020年1月1日至2021年11月30日于川北医学院附属医院肿瘤科接受根治性同步放化疗宫颈癌患者的临床资料,放疗采用外照射+近距离治疗方式,内外照射剂量评估采用内、外照射生物等效剂量(EQD2)参数直接叠加和内外照射三维计划图像形变配准(DIR)剂量叠加,分析两种剂量评估方式剂量学差异。RLRI分级标准采用肿瘤放射治疗协作组标准。运用两种剂量评估方式构建RLRI的预测模型,使用受试者工作特征(ROC)曲线计算曲线下面积,以评估不同剂量评估方式的预测准确性。结果 多次近距离治疗剂量叠加的EQD2参数较DIR剂量叠加高危临床靶区D_95%和D_90%分别高2.18和2.92 Gy,直肠D_{2 cm³}、D_{1 cm³}、D_{0.1 cm³}分别高1.74、2.28、2.26 Gy(t=3.82、5.21、4.58、5.17、2.05,P<0.05)。外照射与近距离治疗,直肠D_{2 cm³}、D_{1 cm³}、D_{0.1 cm³}的EQD2参数直接叠加比DIR剂量叠加高6.22、7.61、9.56 Gy(t=9.40、10.59、7.87,P<0.001)。联合预测模型ROC曲线下面积为0.788,最佳预测阈值的灵敏度为0.850,特异度为0.660,Hosmer-Lemeshow拟合优度检验显示,拟合优度较好(P>0.05)。传统预测指标DIR剂量叠加的预测模型:直肠D_{2 cm³}、D_{1 cm³}的ROC曲线下面积分别为0.784、0.763,最佳预测阈值的灵敏度分别为0.850、0.750,特异度分别为0.679、0.717。结论 内外照射EQD2参数直接叠加与三维计划图进行DIR剂量叠加评估剂量参数有剂量学差异。DIR剂量叠加直肠D_{2 cm³}、D_{1 cm³}与联合预测模型预测RLRI的价值较高,但联合预测模型预测RLRI计算复杂,建议临床上通过DIR剂量叠加直肠D_{2 cm³}、D_{1 cm³}预测RLRI。     

Effects of image normalization on the statistical analysis of perfusion MRI in elderly brains

Purpose

To fully understand the effects of an image processing methodology on the comparisons of regional patterns of brain perfusion over time and between subject groups.

Materials and Methods

Two brain normalization methods were compared using images of elderly controls and subjects with MCI and AD: the normalization package of statistical parametric mapping (SPM2), and a fully deformable model (FDM). The performance of these two normalization methods was quantitatively evaluated based on two criteria: (a) the alignment accuracy of five brain structures to the colin27 reference volume, and (b) impact of spatial normalization methods on the sensitivity of perfusion magnetic resonance imaging (pMRI).

Results

The delineations of all five brain structures had significantly higher overlap with expert manual tracings using FDM compared to SPM (two‐tailed, P < 0.025). When applied to the biostatistical analysis of CBF maps, a larger number of statistically significant voxels was identified from FDM compared with SPM2 regardless of the effects of the threshold and smoothing kernel.

Conclusion

The greater degree of deformation freedom associated with FDM may yield more accurate region matching and higher statistical sensitivity in identifying regions of CBF differences between elderly groups with prevalent late‐life neurodegenerative conditions. J. Magn. Reson. Imaging 2008;28:1351–1360. © 2008 Wiley‐Liss, Inc.     

骨科金属内植入材料规范化使用登记表的设计

提出了加强骨科金属内植入材料使用管理的必要性。介绍了科室研究设计的“医用骨科植入性材料使用登记表”，该表解决了因金属内植入材料的质量问题而引起的医疗纠纷问题，其应用统一了运作流程，避免了医疗工作秩序的混乱，在骨科手术中应用637例，取得了良好效果，保证了医院的整体医疗质量。     

A national evaluation of the Australian Occupational Therapy Competency Standards (1994): A multistakeholder perspective

This paper summarises results from an evaluation of the adequacy and utility of the Australian Competency Standards for Entry-Level Occupational Therapists © (OT AUSTRALIA, 1994a). It comprised a two-part study, incorporating an online survey of key national stakeholders ( n  = 26), and 13 focus groups ( n  = 152) conducted throughout Australia with occupational therapy clinicians, academics, OT AUSTRALIA association and Occupational Therapy Registration Board representatives, as well as university program accreditors. The key recommendations were that: (i) urgent revision to reflect contemporary practice, paradigms, approaches and frameworks is required; (ii) the standards should exemplify basic competence at graduation (not within two years following); (iii) a revision cycle of five years is required; (iv) the Australian Qualifications Framework should be retained, preceded by an introduction describing the scope and nature of occupational therapy practice in the national context; (v) access to the standards should be free and unrestricted to occupational therapists, students and the public via the OT AUSTRALIA (national) website; (vi) the standards should incorporate a succinct executive summary and additional tools or templates formatted to enable occupational therapists to develop professional portfolios and create working documents specific to their workplace; and (vii) language must accommodate contextual variation while striking an appropriate balance between providing instruction and encouraging innovation in practice.     

Sensitivity analysis of fiducial placement on transorbital target registration error

Objective In many clinical applications of image-guided surgery, skin fiducial placement is poorly defined and occasionally poorly executed, leading to an increase in the target registration error (TRE). Fiducial placement analysis usually focuses on a single target, where surgical guidance requires accurate localization of a region or volume of tissue. To address these limitations, a method of fiducial positioning for minimizing the TRE in a target region was developed. Method This methodology uses patient specific anatomic data, the patient skin surface and accounts for areas which may be poor choices for fiducial placement due to likely fiducial motion. The effect of skin motion on the expected TRE of a target region was modeled and evaluated. Transorbital therapy delivery was selected as the application of interest, so facial morphology is of greatest importance. Our target region is the pyramidal space behind the globe of the eye. A laser range scan of the face of a skull phantom with taboo regions chosen semiautomatically was used as an input to the simulated annealing optimization algorithm. Results Optimizing the fiducial position reduced the expected TRE by 50% when compared to an unoptimized fiducial placement. In addition, the effect of fiducial motion or localizer fiducial localization error is also reduced in the optimized version. Conclusion Improved registration results for transorbital therapy delivery were achieved semiautomatically using optical facial surface scans for image-guided surgical localization. The target registration error minimization method was feasible for in vivo applications.