Abstract. Our paper summarizes experiments for measuring the accuracy of deformable 2D-3D registration between sets of simulated x-ray images (DRR's) and a statistical shape model of the pelvis bones, which includes x-ray attenuation information ("density"). In many surgical scenarios, the images contain a truncated view of the pelvis anatomy. Our work specifically addresses this problem by examining different selections of truncated views as target images. Our atlas is derived by applying principal component analysis to a population of up to 110 instance shapes. The experiments measure the registration error with a large and truncated FOV. A typical accuracy of about 2 mm is achieved in the 2D-3D registration, compared with about 1.4 mm of an "optimal" 3D-3D registration.

Abstract. We present an iterative bootstrapping framework to create and analyze statistical atlases of bony anatomy such as the human pelvis from a large collection of CT data sets. We create an initial tetrahedral mesh representation of the target anatomy and use deformable intensitybased registration to create an initial atlas. This atlas is used as prior information to assist in deformable registration/segmentation of our subject image data sets, and the process is iterated several times to remove any bias from the initial choice of template subject and to improve the stability and consistency of mean shape and variational modes. We also present a framework to validate the statistical models. Using this method, we have created a statistical atlas of full pelvis anatomy with 110 healthy patient CT scans. Our analysis shows that any given pelvis shape can be approximated up to an average accuracy of 1.5036 mm using the first 15 principal modes of variation. Although a particular intensity-based deformable registration algorithm was used to produce these results, we believe that the basic method may be adapted readily for use with any registration method with broadly similar characteristics.

Cone beam computed tomography (CBCT) is a well-established imaging modality with numerous proven applications across multiple clinical disciplines. More recently, CBCT has emerged as an important imaging tool for bronchoscopists, primarily used during transbronchial biopsy of peripheral pulmonary lesions (PPLS). For this application CBCT has proved useful in navigating devices to a target lesion, in confirming device tool-in-lesion, as well as during tissue acquisition. In addition, CBCT is poised to play an important role in trials evaluating bronchoscopic ablation by helping to determine the location of the ablative probe relative to the target lesion. Before adopting this technology, it is key for bronchoscopists to learn some basic concepts that will allow them to have a safer and more successful experience with CBCT.Hence, in the current manuscript, we will focus on both technical and practical aspects of CBCT imaging, ranging from systems considerations, image quality, radiation dose and dose-reduction strategies, procedure room set-up, and best practices for CBCT image acquisition.

Abstract. Intra-operative guidance in Transrectal Ultrasound (TRUS) guided prostate brachytherapy requires localization of inserted radioactive seeds relative to the prostate. Seeds were reconstructed using a typical C-arm, and exported to a commercial brachytherapy system for dosimetry analysis. Technical obstacles for 3D reconstruction on a nonisocentric C-arm included pose-dependent C-arm calibration; distortion correction; pose estimation of C-arm images; seed reconstruction; and C-arm to TRUS registration. In precision-machined hard phantoms with 40-100 seeds, we correctly reconstructed 99.8% seeds with a mean 3D accuracy of 0.68 mm. In soft tissue phantoms with 45-87 seeds and clinically realistic 15 o C-arm motion, we correctly reconstructed 100% seeds with an accuracy of 1.3 mm. The reconstructed 3D seed positions were then registered to the prostate segmented from TRUS. In a Phase-1 clinical trial, so far on 4 patients with 66-84 seeds, we achieved intra-operative monitoring of seed distribution and dosimetry. We optimized the 100% prescribed iso-dose contour by inserting an average of 3.75 additional seeds, making intra-operative dosimetry possible on a typical C-arm, at negligible additional cost to the existing clinical installation.

Background and purpose The metal coverage ratio (MCR) of a flow diverter influences the intra-aneurysmal hemodynamics; a high MCR will occlude an aneurysm early, while a low MCR may delay aneurysm occlusion. The true MCR of a pipeline embolization device (PED) could be lower due to oversize, device deformation, or aneurysm location. In this study deviation of the true MCR from the nominal MCR is assessed and whether their difference affects aneurysm occlusion rate is determined. Methods A total of 40 consecutive patients, each of them treated by one PED for their aneurysms at the internal carotid artery (ICA), were retrospectively analyzed. The DynaCT images of these deployed PEDs were used to determine their true dimensions and estimate three MCRs (local, mean, and nominal). These data were compared in two groups of patients who had different aneurysm outcomes at six months. Results The difference in the local MCR between two groups is small, but statistically significant (24.5% vs 21.6%, p = 05). The local MCR is consistently lower than the nominal MCRs (23.2% vs 30.2%, p < 0.001); however, the difference between the mean and local MCRs is small (23.9% vs 23.2%). Conclusions An expectation that a PED can achieve a MCR of 30% may not be reasonable. Device oversize and deformation during deployment lower the local MCR by 5–7%. A lowered MCR affects the aneurysm occlusion rate at six months.