Registration of preoperative and postresection images is often needed to evaluate the effectiveness of treatment. While several non-rigid registration methods exist, most would be unable to accurately align these types of datasets due to the absence of tissue in one image. Here we present a joint registration and segmentation algorithm which handles the missing correspondence problem. An intensity-based prior is used to aid in the segmentation of the resection region from voxels with valid correspondences in the two images. The problem is posed in a maximum a posteriori (MAP) framework and optimized using the expectation-maximization (EM) algorithm. Results on both synthetic and real data show our method improved image alignment compared to a traditional non-rigid registration algorithm as well as a method using a robust error kernel in the registration similarity metric.

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To evaluate changes in brain structure or function, longitudinal images of brain tumor patients must be non-rigidly registered to account for tissue deformation due to tumor growth or treatment. Most standard non-rigid registration methods will fail to align these images due to the changing feature correspondences between treatment time points and the large deformations near the tumor site. Here we present a registration method which jointly estimates a label map for correspondences to account for the substantial changes that may occur during tumor treatment. Under a Bayesian parameter estimation framework, we employ different probability distributions depending on the correspondence labels. We incorporate models for image similarity, an image intensity prior, label map smoothing, and a transformation prior that encourages deformation near the estimated tumor location. Our proposed algorithm increases registration accuracy compared to a traditional voxel-based registration method as shown using both synthetic and real patient images.

The treatment of metastatic brain tumors with stereotactic radiosurgery requires that the clinician first locate the tumors and measure their volumes. Thoroughly searching a patient scan for brain tumors and delineating the lesions can be a long and difficult task when done manually and is also prone to human error. In this paper, we present an automated method for detecting changes in brain tumor lesions over longitudinal scans to aide the clinician’s task of determining tumor volumes. Our approach jointly registers the current image with a previous scan while estimating changes in intensity correspondences due to tumor growth or regression. We combine the label map with correspondence changes with tumor segmentations from a previous scan to estimate the metastases in the new image. Alignment and tumor tracking results show promise on 28 registrations using real patient data.

Registration of images with missing correspondences, such as in the alignment of preoperative and postresection brain data, is a difficult task. To simplify this problem, we introduce an indicator map to segment valid correspondence regions from areas with missing data. The registration problem is posed in a marginalized maximum a posteriori (MAP) estimation framework in which the transformation and correspondence regions are simultaneously estimated using the expectation-maximization (EM) algorithm. The E-step calculates the weights of the possible indicator maps while the M-step updates the transformation. A spatial prior based on principal component analysis (PCA) is used to guide indicator map selection. We demonstrate the promise of our approach on synthetic and real data by comparing results using our algorithm to those from a standard non-rigid registration method.