Image Registration Using Robust Correlation

We have investigated an intensity-based image registration technique using a robust correlation coefficient as a similarity measure. The proposed method has an advantage over the ordinary correlation coefficient since it reduces the effect of "outlier" image intensity values. For the application of image registration to radiotherapy or image-guided surgery, there may be outlier samples due to the presence of the objects such as surgical instruments. We have verified the usefulness of the proposed method by simulation and phantom experiment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86025/1/Fessler176.pd

Intensity-Based Image Registration Using Robust Correlation Coefficients

The ordinary sample correlation coefficient is a popular similarity measure for aligning images from the same or similar modalities. However, this measure can be sensitive to the presence of “outlier” objects that appear in one image but not the other, such as surgical instruments, the patient table, etc., which can lead to biased registrations. This paper describes an intensity-based image registration technique that uses a robust correlation coefficient as a similarity measure. Relative to the ordinary sample correlation coefficient, the proposed similarity measure reduces the influence of outliers. We also compared the performance of the proposed method with the mutual information- based method. The robust correlation-based method should be useful for image registration in radiotherapy (KeV to MeV X-ray images) and image-guided surgery applications. We have investigated the properties of the proposed method by theoretical analysis, computer simulations, a phantom experiment, and with functional magnetic resonance imaging data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85801/1/Fessler55.pd

Considerations for experimental animal ethics in the research planning and evaluation process

Research using experimental animals has substantially contributed to advances in science and medicine. Animal experiments are nearly essential for biomedical research and development efforts. Because many animals are sacrificed, researchers should consider the welfare of experimental animals and related ethical issues, along with the successful results of their experiments. This review introduces the criteria that should be considered in terms of experimental animal ethics, based on the principles of the 3 R’s: replacement, representing careful consideration of the need for animal experiments; reduction, representing the use of the minimal number of animals to obtain meaningful experimental results; and refinement, representing continuous effects to find alternative methods to reduce pain and distress in experimental animals. Based on these principles, the following points should be considered when planning experiments: the necessity of animal experiments; alternatives to animal experiments; the relevance of the species and numbers of experimental animals; appropriate assessment and management of pain; the proper usage of sedatives, painkillers, and anesthesia; and valid timing for humane endpoints and euthanasia. These criteria are beneficial for both experimental animals and researchers because careful handling to ensure experimental animal welfare guarantees that scientific research will yield convincing, repeatable, and accurate results

Intensity-based image registration using multiple distributed agents

Image registration is the process of geometrically aligning images taken from different sensors, viewpoints or instances in time. It plays a key role in the detection of defects or anomalies for automated visual inspection. A multiagent distributed blackboard system has been developed for intensity-based image registration. The images are divided into segments and allocated to agents on separate processors, allowing parallel computation of a similarity metric that measures the degree of likeness between reference and sensed images after the application of a transform. The need for a dedicated control module is removed by coordination of agents via the blackboard. Tests show that additional agents increase speed, provided the communication capacity of the blackboard is not saturated. The success of the approach in achieving registration, despite significant misalignment of the original images, is demonstrated in the detection of manufacturing defects on screen-printed plastic bottles and printed circuit boards

Intensity based image registration using robust similarity measure and constrained optimization: Applications for radiation therapy.

In radiotherapy, an x-ray beam arrangement should be planned based on a correct patient model using a planning CT (Computed Tomography) and the x-ray beam should be focused accurately to implement the plan on actual patient. Since the patient model may not be accurate due to organ motion and there is patient set-up error, the actual delivery of the x-ray may differ from the optimal one intended by a physician, thus risking damage to normal tissues and possibly delivering a suboptimal radiation dose to the tumors. Correct estimation of the patient set-up error and organ motion is important since one can retrospectively calculate the actual x-ray dose accumulation from the treatment using the estimated set-up error and organ motion. Moreover, if the set up estimate can be completed quickly before the treatment, then one can compensate for the set-up error by adjusting either the radiotherapy table or the x-ray beam position prior to treatment delivery. Also, if one can build a dynamic model of patient organ motions before treatment, the treatment plan can be established more accurately considering the motions. Image registration is a very useful technique for estimating both patient set up and organ motion for radiation therapy. Patient set up may be estimated by 3D/2D image registration, which registers planning CT image onto radiograph images from the treatment room and organ motion from one time to another may be estimated using nonrigid image registration of two images from two time instances. We investigated several rigid and nonrigid image registration methods that are useful for estimating patient set up positioning and organ motion. By conducting an experiment with anthropomorphic chest phantom, we investigated the feasibility of 3D/2D registration methods for the set-up estimation. We achieved sub-voxel accuracy using two orthogonal projection images by the sample correlation coefficient based and the MI (Mutual Information) based methods. We have proposed a novel robust image registration method based on a robust correlation coefficient, which is useful for registering images containing unexpected objects. Images from treatment rooms usually contain objects that are not present in the planning CT image, such as radiotherapy table. The statistical properties such as bias, variance and robustness of the proposed method in comparisons with the sample correlation and the MI based method have been analyzed. We also investigated a novel nonrigid image registration method in which the estimated deformation obeys the physical constraint of positive Jacobian determinant. We derived a closed form expression of possible minimum and maximum Jacobian in terms of gradient bounds analytically. To enforce the gradient bounds of the deformation in optimization, we have introduced constraint sets in the parameter space. The optimization was accomplished using the gradient projection method with Dykstra's cyclic projection method.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124097/2/3121965.pd

Constrained Optimization: Applications for Radiation Therapy

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Regularized Auto-Encoder-Based Separation of Defects from Backgrounds for Inspecting Display Devices

We investigated a novel method for separating defects from the background for inspecting display devices. Separation of defects has important applications such as determining whether the detected defects are truly defective and the quantification of the degree of defectiveness. Although many studies on estimating patterned background have been conducted, the existing studies are mainly based on the approach of approximation by low-rank matrices. Because the conventional methods face problems such as imperfect reconstruction and difficulty of selecting the bases for low-rank approximation, we have studied a deep-learning-based foreground reconstruction method that is based on the auto-encoder structure with a regression layer for the output. In the experimental studies carried out using mobile display panels, the proposed method showed significantly improved performance compared to the existing singular value decomposition method. We believe that the proposed method could be useful not only for inspecting display devices but also for many applications that involve the detection of defects in the presence of a textured background

GABA/glycine signaling during degeneration and regeneration of mouse hypoglossal nerves

In the adult central nervous system (CNS), GABA and glycine (Gly) are predominant inhibitory neurotransmitters, negatively regulating glutamatergic transmission. In the immature CNS, on the other hand, they act as trophic factors, mediating morphogenesis. In the present study, to investigate their involvement in axonal regeneration, we morphologically examined changes in their signaling in mouse hypoglossal nuclei during degeneration and regeneration of hypoglossal nerves. We found that (1) expression and localization of presynaptic elements were not changed, (2) localization of gephyrin, which anchors GABA and Gly receptors, was spread on the surface of motor neuron cell bodies and dendrites, (3) KCC2-expression markedly decreased, (4) choline acetyltransferase, which mediates acetylcholine-synthesis, immediately disappeared from the motor neurons, and (5) the synaptic cleft of both excitatory and inhibitory synapses became irregularly wider, in the hypoglossal nuclei of the sutured side after the operation. These changes gradually normalized during regeneration. These results suggested that synthesis of acetylcholine may be stopped in the motor neuron after axotomy. GABA/Gly may be normally released from presynaptic terminals, be spilled over the original synaptic cleft, be diffused into the neighboring space, bind to extrasynaptically localized receptors, and mediate depolarization of the membrane potential of motor neurons during degeneration and regeneration. Furthermore, it was suggested that GABA/Gly signaling in postsynaptic motor neurons went back to being immature after axotomy, and may play an important role in axonal regeneration