The potential impact of CT-MRI matching on tumor volume delineation in advanced head and neck cancer

To study the potential impact of the combined use of CT and MRI scans on the Gross Tumor Volume (GTV) estimation and interobserver variation. Four observers outlined the GTV in six patients with advanced head and neck cancer on CT, axial MRI, and coronal or sagittal MRI. The MRI scans were subsequently matched to the CT scan. The interobserver and interscan set variation were assessed in three dimensions. The mean CT derived volume was a factor of 1.3 larger than the mean axial MRI volume. The range in volumes was larger for the CT than for the axial MRI volumes in five of the six cases. The ratio of the scan set common (i.e., the volume common to all GTVs) and the scan set encompassing volume (i.e., the smallest volume encompassing all GTVs) was closer to one in MRI (0.3-0.6) than in CT (0.1-0.5). The rest volumes (i.e., the volume defined by one observer as GTV in one data set but not in the other data set) were never zero for CT vs. MRI nor for MRI vs. CT. In two cases the craniocaudal border was poorly recognized on the axial MRI but could be delineated with a good agreement between the observers in the coronal/sagittal MRI. MRI-derived GTVs are smaller and have less interobserver variation than CT-derived GTVs. CT and MRI are complementary in delineating the GTV. A coronal or sagittal MRI adds to a better GTV definition in the craniocaudal directio

Unsupervised correspondence with combined geometric learning and imaging for radiotherapy applications

The aim of this study was to develop a model to accurately identify corresponding points between organ segmentations of different patients for radiotherapy applications. A model for simultaneous correspondence and interpolation estimation in 3D shapes was trained with head and neck organ segmentations from planning CT scans. We then extended the original model to incorporate imaging information using two approaches: 1) extracting features directly from image patches, and 2) including the mean square error between patches as part of the loss function. The correspondence and interpolation performance were evaluated using the geodesic error, chamfer distance and conformal distortion metrics, as well as distances between anatomical landmarks. Each of the models produced significantly better correspondences than the baseline non-rigid registration approach. The original model performed similarly to the model with direct inclusion of image features. The best performing model configuration incorporated imaging information as part of the loss function which produced more anatomically plausible correspondences. We will use the best performing model to identify corresponding anatomical points on organs to improve spatial normalisation, an important step in outcome modelling, or as an initialisation for anatomically informed registrations. All our code is publicly available at https://github.com/rrr-uom-projects/Unsup-RT-Corr-NetComment: Accepted in 3rd Workshop on Shape in Medical Imaging (ShapeMI 2023). This preprint has not undergone peer review or any post-submission improvements or correction

Insertion of ester bonds in three terpolymerization systems

Nonbiodegradable (co)polymers with all-carbon backbone produced via radical polymerization are used in various applications. For some applications, like for example in skincare and haircare, these polymers are nonrecoverable and therefore would be preferably made biodegradable. Therefore, inserting ester bonds in the backbone via radical ring opening terpolymerization of acrylates and 2-methylene-1,3 dioxepane (MDO) could be a suitable approach to obtain biodegradable terpolymers. This report investigates the influence of batch versus semibatch process on the polymerization of three terpolymerization systems viz. (i) methacrylamide (MAAM)/n-butyl acrylate (nBA)/BMDO (5,6-Benzo-2-Methylene-1,3-Dioxepane), (ii) MAAM/nBA/MDO, and (iii) methyl methacrylate (MMA)/VAc (vinyl acetate) /MDO. We demonstrate the improvement in number of ester groups inserted and the homogeneity of insertion via semibatch polymerization processes. The process is guided via optimal monomer addition feeding profiles generated using the reactivity ratios of comonomers. Such improved insertion was demonstrated by the molecular weight distribution of fragments after alkali degradation in the investigated systems.</p

New Vesicle-polymer Hybrids: the parachute architecture

The influence of organized media on polymerization reactions results in many cases in interesting morphologies of the polymeric material. In the present study, vesicle bilayers were used as ordered medium for the free radical polymerization of styrene. Cryo-electron microscopy gives evidence that the polymerization induces phase-separation phenomena leading to parachute-like morphologies. On the basis of general knowledge about vesicles and polymerizations in heterogeneous media, explanations for the observed phenomena are given. Bearing in mind that vesicles are outstanding models for membrane mimetic chemistry, it becomes evident that these findings can be relevant to the investigation of, for example, membrane−protein interactions