Assessment of Left Ventricular Viscoelastic Components Based on Ventricular Harmonic Behavior

Background: Assessment of left ventricular (LV) function with an emphasis on contractility has been a challenge in cardiac mechanics during the recent decades. The LV function is usually described by the LV pressure-volume (P-V) relationship. Based on this relationship, the ratio of instantaneous pressure to instantaneous volume is an index for LV chamber stiffness. The standard P-V diagrams are easy to interpret but difficult to obtain and require invasive instrumentation for measuring the corresponding volume and pressure data. In the present study, we introduce a technique that can estimate viscoelastic properties, not only the elastic component but also the viscous properties of the LV based on oscillatory behavior of the ventricular chamber and it can be applied non-invasively as well. Materials and Methods: The estimation technique is based on modeling the actual long axis displacement of the mitral annulus plane toward the cardiac base as a linear damped oscillator with time-varying coefficients. Elastic deformations resulting from the changes in the ventricular mechanical properties of myocardium are represented as a time-varying spring while the viscous components of the model include a time-varying viscous damper, representing relaxation and the frictional energy loss. To measure the left ventricular axial displacement ten healthy sheep underwent left thoracotomy and sonomicrometry transducers were implanted at the apex and base of the LV. The time-varying parameters of the model were estimated by a standard Recursive Linear Least Squares (RLLS) technique. Results: LV stiffness at end-systole and end-diastole was in the range of 61.86–136 dyne/g.cm and 1.25–21.02 dyne/g.cm, respectively. Univariate linear regression was performed to verify the agreement between the estimated parameters, and the measured values of stiffness. The averaged magnitude of the stiffness and damping coefficients during a complete cardiac cycle were estimated as 58.63±12.8 dyne/g.cm and 0 dyne.s/g.cm, respectively. Conclusion: The results for the estimated elastic coefficients are consistent with the ones obtained from force-displacement diagram. The trend of change in the estimated parameters is also in harmony with the previous studies done using P-V diagram. The only input used in this model is the long axis displacement of the annulus plane, which can also be obtained non-invasively using tissue Doppler or MR imaging.     

Deep neural models for color classification and color constancy

Color constancy is our ability to perceive constant colors across varying illuminations. Here, we trained deep neural networks to be color constant and evaluated their performance with varying cues. Inputs to the networks consisted of two-dimensional images of simulated cone excitations derived from three-dimensional (3D) rendered scenes of 2,115 different 3D shapes, with spectral reflectances of 1,600 different Munsell chips, illuminated under 278 different natural illuminations. The models were trained to classify the reflectance of the objects. Testing was done with four new illuminations with equally spaced CIEL*a*b* chromaticities, two along the daylight locus and two orthogonal to it. High levels of color constancy were achieved with different deep neural networks, and constancy was higher along the daylight locus. When gradually removing cues from the scene, constancy decreased. Both ResNets and classical ConvNets of varying degrees of complexity performed well. However, DeepCC, our simplest sequential convolutional network, represented colors along the three color dimensions of human color vision, while ResNets showed a more complex representation.     

A mechanism for sensory re-weighting in postural control

A key finding of human balance experiments has been that the integration of sensory information utilized for postural control appears to be dynamically regulated to adapt to changing environmental conditions and the available sensory information, a process referred to as “sensory re-weighting.” We propose a postural control model that includes automatic sensory re-weighting. This model is an adaptation of a previously reported model of sensory feedback that included manual sensory re-weighting. The new model achieves sensory re-weighting that is physiologically plausible and readily implemented. Model simulations are compared to previously reported experimental results to demonstrate the automated sensory re-weighting strategy of the modified model. On the whole, the postural sway time series generated by the model with automatic sensory re-weighting show good agreement with experimental data, and are capable of producing patterns similar to those observed experimentally.     

Late presentation of a complete complex thumb metacarpophalangeal joint dislocation: A case report

Metacarpophalangeal (MP) joint injuries and dislocations of the fingers and thumb are not uncommon. They can be classified directionally as either being volar or dorsal, and are further categorized as incomplete, simple complete or complex complete. Complex dislocations are described as dislocations that are irreducible and often require surgical intervention. This is often because tissue has become entrapped within the MP joint, precluding its anatomical reduction. For the thumb MP joint, anatomical structures that may become trapped include the volar plate, sesamoid bones, bony fracture fragments or the flexor pollicis longus tendon. Both dorsal and volar surgical approaches have been described, and their relative merits will be discussed. The unusual case of a late presentation (two months postinjury) of a complex complete dorsal dislocation of the thumb MP joint approached from a dorsal incision is presented.     

Quality Measures for Supportive Cancer Care: The Cancer Quality-ASSIST Project

Patients and physicians often cite symptom control as one of their most important goals in cancer care. Despite this, a previous systematic review found few tools for evaluating the quality of supportive cancer management. We developed a comprehensive set of quality indicators for evaluating pain and nonpain symptom management as well as care planning needs in cancer patients. Based on the prevalence and quality-of-life data, clinician-researchers prioritized pain, psychosocial distress, dyspnea, nausea and vomiting, fatigue and anorexia, treatment-associated toxicities, and information and care planning for quality-indicator development. Using search terms and selection criteria, we identified English-language documents from Medline (1997–2007) and Internet-based searches. Based on this evidence, clinician-reviewers proposed process quality indicators. We then used the VA Health Services Research and Development (VA HSR & D) appropriateness methods to compile the ratings of a multidisciplinary, international expert panel of the validity and feasibility of each indicator. The panel judged 92 out of 133 (69%) proposed quality indicators valid and feasible (15 out of 23 pain, 5 out of 6 depression, 8 out of 11 dyspnea, 15 out of 19 nausea and vomiting, 13 out of 26 fatigue and anorexia, 23 out of 32 other treatment-associated toxicities, and 13 out of 16 information and care planning). Of the final indicators, 67 are potentially useful for inpatient and 81 for outpatient evaluation, and 26 address screening, 12 diagnostic evaluation, 20 management, and 21 follow-up. These quality indicators provide evidence-explicit tools for measuring processes critical to ensuring high-quality supportive cancer care. Research is needed to characterize adherence to recommended practices and to evaluate the use of these measures in quality improvement efforts.     

Optical coherence tomography for presurgical margin assessment of non‐melanoma skin cancer – a practical approach

In the clinical setting, optical coherence tomography (OCT) is applicable for the non‐invasive diagnosis of skin cancer and may in particular be used for margin definition prior to excision. In this regard, OCT may improve the success rate of removing tumor lesions more effectively, preventing repetitive excision, which may subsequently result in smaller excisions. In this study, we have aimed to evaluate the applicability of OCT for in vivo presurgical margin assessment of non‐melanocytic skin tumors (NMSC) and to describe the feasibility of different scanning techniques. A total number of 18 patients planned for excision of lesions suspicious of NMSC were included in this study. Based on OCT, we defined the specific tumor margins on 19 lesions preoperatively using different scanning modalities. Sixty‐one margin points and five complete tumor margins were analysed on 18 patients with a total of 19 lesions including 63% basal cell carcinoma (BCC) (n = 12), 16% (n = 3) squamous cell carcinoma (SCC) and 21% of other types of skin tumors (n = 4) were classified. In 84% of the cases (n = 16), the OCT‐defined lateral margins correctly indicated complete removal of the tumor. The surgical margins chosen by the surgeon never fell below the OCT‐defined margin. Regarding the techniques of marginal definition, punctual tumor border scan in the perpendicular direction, with an extension of free‐run scans for unsure cases can hardly be recommended. This study shows that suspected NMSC can effectively be confirmed, and furthermore, resection margin can be minimized under OCT control without reducing the rate of complete removal.