Automated,accurate, and three-dimensional method for calculating sagittal slope of the tibial plateau

Increased posterior-inferior directed slope of the subchondral bone of the lateral tibial plateau is a risk factor for noncontact rupture of the anterior cruciate ligament (ACL). Previous measures of lateral tibial slope, however, vary from study to study and often lack documentation of their accuracy. These factors impede identifying the magnitude of lateral tibial slope that increases risk of noncontact ACL rupture. Therefore, we developed and evaluated a new method that (1) requires minimal user input; (2) employs 3D renderings of the tibia that are referenced to a 3D anatomic coordinate system; and (3) is precise, reliable, and accurate. The user first isolated the proximal tibia from computed tomography (CT) scans. Then, the algorithm placed the proximal tibia in an automatically generated tibial coordinate system. Next, it identified points along the rim of subchondral bone around the lateral tibial plateau, iteratively fit a plane to this rim of points, and, finally, referenced the plane to the tibial coordinate system. Precision and reliability of the lateral slope measurements were respectively assessed via standard deviation and intra- and inter-class correlation coefficients using CT scans of three cadaveric tibia. Accuracy was quantified by comparing changes in lateral tibial slope calculated by our algorithm to predefined in silico changes in slope. Precision, reliability, and accuracy were ≤0.18°, ≥0.998, and ≤0.13°, respectively. We will use our novel method to better understand the relationship between lateral tibial slope and knee biomechanics towards preventing ACL rupture and improving its treatment.     

A classical molecular approach to computer simulation of biological sorting

Steinberg's theory of sorting is modified by replacing the free energy minimization principle with dynamical equations of a molecular nature. Correct cellular sorting then follows in all cases where the mixture is in a liquid or a near-liquid state. Computer examples are described and discussed, primarily for two dimensional, but also for three dimensional, interactions.     

Genetic compatibility in long-term intimate relationships: partner similarity at major histocompatibility complex (MHC) genes may reduce in-pair attraction

Theoretical models from evolutionary biology predict that individual mate choice will be influenced by the extent of similarity between potential mates at the major histocompatibility complex (MHC) genes. A number of studies have sought to uncover an effect of MHC similarity on mate choice in humans, but the extent to which MHC similarity influences attraction within existing human relationships has been relatively under-explored. We investigated this question in a sample of 168 heterosexual couples that were typed and matched at 3 classical MHC markers. Findings were mixed with respect to the prediction that higher levels of MHC similarity would be linked to a reduction of in-pair attraction. In the full sample, there were no effects of MHC similarity on any of the dependent variables used to measure in-pair attraction, but there were strong and consistent effects of MHC similarity on these measures in couples with two Asian partners (N couples =44). In sum, our findings are consistent with an effect of MHC similarity on in-pair attraction within existing relationships, but they also suggest that this effect may be moderated by additional factors, particularly the ancestral background of the individual relationship partners.     

A software platform for statistical evaluation of patient respiratory patterns in radiation therapy

AimThe aim of this work was to design and evaluate a software tool for analysis of a patient’s respiration, with the goal of optimizing the effectiveness of motion management techniques during radiotherapy imaging and treatment.Materials and methodsA software tool which analyses patient respiratory data files (.vxp files) created by the Varian Real-Time Position Management System (RPM) was developed to analyse patient respiratory data. The software, called RespAnalysis, was created in MATLAB and provides four modules, one each for determining respiration characteristics, providing breathing coaching (biofeedback training), comparing pre and post-training characteristics and performing a fraction-by-fraction assessment. The modules analyse respiratory traces to determine signal characteristics and specifically use a Sample Entropy algorithm as the key means to quantify breathing irregularity. Simulated respiratory signals, as well as 91 patient RPM traces were analysed with RespAnalysis to test the viability of using the Sample Entropy for predicting breathing regularity.ResultsRetrospective assessment of patient data demonstrated that the Sample Entropy metric was a predictor of periodic irregularity in respiration data, however, it was found to be insensitive to amplitude variation. Additional waveform statistics assessing the distribution of signal amplitudes over time coupled with Sample Entropy method were found to be useful in assessing breathing regularity.ConclusionsThe RespAnalysis software tool presented in this work uses the Sample Entropy method to analyse patient respiratory data recorded for motion management purposes in radiation therapy. This is applicable during treatment simulation and during subsequent treatment fractions, providing a way to quantify breathing irregularity, as well as assess the need for breathing coaching. It was demonstrated that the Sample Entropy metric was correlated to the irregularity of the patient’s respiratory motion in terms of periodicity, whilst other metrics, such as percentage deviation of inhale/exhale peak positions provided insight into respiratory amplitude regularity.