Management of epistaxis in hereditary haemorrhagic telangiectasia (HHT) patients using pulsed dye laser and the effect of withholding treatment during the COVID pandemic.

Using a patient survey, pulsed dye laser (PDL) treatment of epistaxis for hereditary haemorrhagic telangiectasia (HHT) patients was evaluated after initial referral. Subsequently, due to the COVID pandemic, a natural experimental set-up allowed assessment of an enforced withdrawal of treatment. A total of 34 subjects were identified as undergoing PDL for HHT-related epistaxis. They were surveyed to look at the effectiveness of PDL treatment after initial referral and at the effect of delay to treatment during COVID on epistaxis and the associated quality of life. The survey also examined the comparison to other available treatments. Retrospective pre-COVID Epistaxis Severity Scores (ESS) were compared to post-COVID data to assess the effect of treatment withdrawal. The patients were then followed up after resumption of their treatment to assess the ensuing change in ESS. After initial referral, frequency and severity of epistaxis decreased. Fifty-six percent of patients experienced several bleeds per day before treatment, compared to 12% after. 88% of patients had episodes of epistaxis longer than 5 min, which was halved to 44% after treatment. Average ESS pre-COVID was 4.42 compared to 5.43 post-COVID delay, with a significant statistical difference (p = 0.02). On resumption of treatment, average ESS reduced to below pre-COVID levels at 4.39 after only 2 sessions. Seventy-six percent of patients found that withdrawal of PDL during COVID diminished their quality of life. PDL treatment of nasal mucosal telangiectasia reduces the frequency and duration of epistaxis. The ESS is reduced following treatment with PDL and quality of life subjectively improved.

Model validation for a noninvasive arterial stenosis detection problem.

A current thrust in medical research is the development of a non-invasive method for detection, localization, and characterization of an arterial stenosis (a blockage or partial blockage in an artery). A method has been proposed to detect shear waves in the chest cavity which have been generated by disturbances in the blood flow resulting from a stenosis. In order to develop this methodology further, we use one-dimensional shear wave experimental data from novel acoustic phantoms to validate a corresponding viscoelastic mathematical model. We estimate model parameters which give a good fit (in a sense to be precisely defined) to the experimental data, and use asymptotic error theory to provide confidence intervals for parameter estimates. Finally, since a robust error model is necessary for accurate parameter estimates and confidence analysis, we include a comparison of absolute and relative models for measurement error.

High-order space-time finite element schemes for acoustic and viscodynamic wave equations with temporal decoupling.

We revisit a method originally introduced by Werder et al. (in Comput. Methods Appl. Mech. Engrg., 190:6685-6708, 2001) for temporally discontinuous Galerkin FEMs applied to a parabolic partial differential equation. In that approach, block systems arise because of the coupling of the spatial systems through inner products of the temporal basis functions. If the spatial finite element space is of dimension D and polynomials of degree r are used in time, the block system has dimension (r + 1)D and is usually regarded as being too large when r > 1. Werder et al. found that the space-time coupling matrices are diagonalizable over [Formula: see text] for r ⩽100, and this means that the time-coupled computations within a time step can actually be decoupled. By using either continuous Galerkin or spectral element methods in space, we apply this DG-in-time methodology, for the first time, to second-order wave equations including elastodynamics with and without Kelvin-Voigt and Maxwell-Zener viscoelasticity. An example set of numerical results is given to demonstrate the favourable effect on error and computational work of the moderately high-order (up to degree 7) temporal and spatio-temporal approximations, and we also touch on an application of this method to an ambitious problem related to the diagnosis of coronary artery disease. Copyright © 2014 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.

The speed of sound and attenuation of an IEC agar-based tissue-mimicking material for high frequency ultrasound applications.

This study characterized the acoustic properties of an International Electromechanical Commission (IEC) agar-based tissue mimicking material (TMM) at ultrasound frequencies in the range 10-47 MHz. A broadband reflection substitution technique was employed using two independent systems at 21°C ± 1°C. Using a commercially available preclinical ultrasound scanner and a scanning acoustic macroscope, the measured speeds of sound were 1547.4 ± 1.4 m∙s(-1) and 1548.0 ± 6.1 m∙s(-1), respectively, and were approximately constant over the frequency range. The measured attenuation (dB∙cm(-1)) was found to vary with frequency f (MHz) as 0.40f + 0.0076f(2). Using this polynomial equation and extrapolating to lower frequencies give values comparable to those published at lower frequencies and can estimate the attenuation of this TMM in the frequency range up to 47 MHz. This characterisation enhances understanding in the use of this TMM as a tissue equivalent material for high frequency ultrasound applications.

Assessment of tissue Doppler imaging measurements of arterial wall motion using a tissue mimicking test rig.

The aim of this in vitro study is to assess the accuracy of the tissue Doppler imaging arterial wall motion (TDI AWM) technique in measuring dilation over a range of distances and velocities. A test rig, consisting of two parallel blocks of tissue mimicking material (TMM), has been developed to generate known wall motion. One block remains stationary while the other moves in a cyclical motion. A calibrated laser range finder was used to measure the TMM motion. The TDI AWM measurements were found to underestimate the dilation by 21% +/- 4.7% when using the recommended scanner parameters. The size of the error was found to increase with a decrease in ultrasound output power. Results suggested that errors in the TDI AWM dilation measurements relate to underestimates in the velocity measured by the TDI technique. The error demonstrated in this study indicates a limitation in the value of TDI AWM result obtained in vivo. (E-mail: abigail.thrush@bartsandthelondon.nhs.uk).