Determination of optimal ultrasound planes for the initialisation of image registration during endoscopic ultrasound-guided procedures.

PURPOSE: Navigation of endoscopic ultrasound (EUS)-guided procedures of the upper gastrointestinal (GI) system can be technically challenging due to the small fields-of-view of ultrasound and optical devices, as well as the anatomical variability and limited number of orienting landmarks during navigation. Co-registration of an EUS device and a pre-procedure 3D image can enhance the ability to navigate. However, the fidelity of this contextual information depends on the accuracy of registration. The purpose of this study was to develop and test the feasibility of a simulation-based planning method for pre-selecting patient-specific EUS-visible anatomical landmark locations to maximise the accuracy and robustness of a feature-based multimodality registration method. METHODS: A registration approach was adopted in which landmarks are registered to anatomical structures segmented from the pre-procedure volume. The predicted target registration errors (TREs) of EUS-CT registration were estimated using simulated visible anatomical landmarks and a Monte Carlo simulation of landmark localisation error. The optimal planes were selected based on the 90th percentile of TREs, which provide a robust and more accurate EUS-CT registration initialisation. The method was evaluated by comparing the accuracy and robustness of registrations initialised using optimised planes versus non-optimised planes using manually segmented CT images and simulated ([Formula: see text]) or retrospective clinical ([Formula: see text]) EUS landmarks. RESULTS: The results show a lower 90th percentile TRE when registration is initialised using the optimised planes compared with a non-optimised initialisation approach (p value [Formula: see text]). CONCLUSIONS: The proposed simulation-based method to find optimised EUS planes and landmarks for EUS-guided procedures may have the potential to improve registration accuracy. Further work will investigate applying the technique in a clinical setting.

Evaluation of the Risk of Relapse in Ulcerative Colitis According to the Degree of Mucosal Healing (Mayo 0 vs 1): A Longitudinal Cohort Study.

BACKGROUND AND AIMS: Mucosal healing in ulcerative colitis (UC) has become a common endpoint in most clinical trials and a relevant therapeutic goal in clinical practice. Despite important differences between endoscopic Mayo scores 0 and 1, both scores are considered as mucosal healing in most important trials. The aim of the present study was to evaluate the risk of relapse in UC patients according to the degree of mucosal healing (endoscopic Mayo scores of 0 and 1). METHODS: A prospective longitudinal cohort study was designed. All UC patients who presented with mucosal healing at colonoscopy were consecutively included. Mucosal healing was defined as an endoscopic Mayo score of 0 or 1. Clinical relapse was defined as the need for therapy to induce remission, any treatment escalation, hospitalization or colectomy. All clinical relapses were evaluated at months 6 and 12 after study entry. Results were subjected to unconditional stepwise logistic and Kaplan-Meier regression analysis. RESULTS: One hundred and eighty-seven consecutive UC patients (126 [67.3%] with Mayo score 0 and 61 [32.7%] with Mayo score 1) were included. Of patients with Mayo scores 0 and 1, 9.4 and 36.6% respectively presented a relapse during the first 6 months of follow-up (p < 0.001). The only factor independently associated with UC relapses in the multivariate analysis was an endoscopic Mayo score of 1 (odds ratio 6.27, 95% confidence interval 2.73-14.40, p < 0.001). CONCLUSIONS: Patients with an endoscopic Mayo score of 1 have a higher risk of relapse than those with a score of 0. The concept of mucosal healing should be limited to patients with an endoscopic Mayo score of 0.