Medical & Biological Engineering & Computing

The paper describes the design, technical characteristics and first results of an adjustable staircase with commercial force plates embedded in the steps and custom force transducers as part of the handrail supports. For the railing assembly, the greatest errors (<10% of maximum signal) and cross-talk range (0.58–6.74%) were in the medial-lateral direction and were corrected using a calibration matrix. Power spectral density analyses showed free vibration frequency responses for both the railing (15Hz) and steps (38.6Hz) that were relatively distinct from lower applied forces recorded during stair ascent. The creation of standardised filtering protocols was therefore possible to provide step reaction force signals identical to the literature and examples of upper-limb reaction forces that have not been shown before. Such a staircase will allow a more complete study of full body contributions to stair walking across various subject populations.

An electronic feature-extraction system is presented that simplifies the measurement of five parameters of the action potential. These parameters are: (a) the peak amplitude of the action potential, (b) the maximum slope, (c) the threshold as measured at the inflection on the rising phase of the action potential, (d) the time interval between the inflection and the peak of the action potential, and (e) the time constant of the ‘exponentially’ rising foot of the action potential. Using this equipment, the foot of the action potential was found in the squid giant axon to be close to a pure exponential only at temperatures less than 15° C.

A catheter tip pressure transducer was testedin vitro to determine its stability, linearity and frequency response. It was then compared simultaneously with an oesophageal balloon in two trained adult subjects, using measurements of end-expiratory oesophageal pressure and the ratio of oesophageal pressure to mouth pressure changes during airway occlusion. This ratio should be unity, since during airway occlusion there is no flow and pressure changes should be evenly distributed throughout the closed system. The catheter tip pressure transducer was used in 13 infants, who were all studied initially with an oesophageal balloon, during the course of routine lung function tests. Measurements of pulmonary resistance, compliance, end-expiratory oesophageal pressure and the ratio of oesophageal pressure change to mouth pressure change were made with both instruments. The ratio of oesophageal to mouth pressure change and pulmonary resistance were elevated and dynamic compliance reduced when measured with the catheter tip pressure transducer, showing that the catheter tip pressure transducer was overestimating the size of pressure swings within the oesophagus. The absolute value of end-expiratory oesophageal pressure was always more positive when measured with the catheter tip pressure transducer than with the balloon, suggesting that absolute pressure was also incorrectly monitored. It is recommended that the catheter tip pressure transducer should not be used in studies of infant lung mechanics until these problems have been resolved.

Two cases of fetal tachycardia are reported: atrial flutter and fibrillation. The waveforms from each case were detected by fetal magnetocardiograms (FMCGs) using a 64-channel superconducting quantum interference device (SQUID) system. Because the magnitude of supraventricular arrhythmia signals is very weak, two subtraction methods were used to detect the fetal MCG waveforms: subtraction of the maternal MCG signal, and subtraction of the fetal QRS complex signal. It was found that atrial-flutter waveforms showed a cyclic pattern and that atrial-fibrillation waveforms showed f-waves with a random atrial rhythm. Fast Fourier transform analysis determined the main frequency of the atrial flutter to be about 7 Hz, and the frequency distribution of atrial fibrillation consisted of small, broad peaks. To visualise the current pattern, current-arrow maps, which simplify the observation of pseudo-current patterns in fetal hearts, of the averaged atrial flutter and fibrillation waveforms were produced. The map of the atrial flutter had a circular pattern, indicating a re-entry circuit, and the map of the atrial fibrillation indicated one wavelet, which was produced by a micro-re-entry circuit. It is thus concluded that an FMCG can detect supraventricular arrhythmia, which can be characterised by re-entry circuits, in fetuses.

A method for the theoretical estimation of the MTF of columnar phosphors with a homogeneous part at the end used in X-ray imaging has been developed. This method considers the light transport inside the scintillator through an analytical modelling, the optical photon beams distribution on the scintillator–optical sensor interface, and uses the definition of the PSF and a Gauss fitted LSF to estimate the MTF of an indirect detector. This method was applied to a columnar CsI:Tl scintillator and validated against experimental results found in literature, and a good agreement was observed. It was found that, by increasing the pixel size of the optical detector and the thickness of the scintillator, the MTF decreased as expected. This method may be used in evaluating the performance of the columnar phosphors used in medical imaging, given their physical and geometrical characteristics. Graphical abstract

Specific absorption rate (SAR) assessment is essential for safety purposes during MR acquisition. Online SAR assessment is not trivial and requires, in addition, knowledge of the electric tissue properties and the electric fields in the human anatomy. In this study, the potential of the recently developed CSI-EPT method to reconstruct SAR distributions is investigated. This method is based on integral representations for the electromagnetic field and attempts to reconstruct the tissue parameters and the electric field strength based on $$B_{1}^{ + }$$ field data only. Full three-dimensional FDTD simulations using a female pelvis model are used to validate two-dimensional CSI reconstruction results in the central transverse plane of a 3T body coil. Numerical experiments demonstrate that the reconstructed SAR distributions are in good agreement with the SAR distributions as determined via 3D FDTD simulations and show that these distributions can be computed very efficiently in the central transverse plane of a body coil with the two-dimensional approach of CSI-EPT.

Cherry andSayers (1956) showed that stammering could be inhibited by the use of low frequency tones which prevented the subject hearing his own voice. They mentioned that this could have possible application in the treatment of stammer but are not aware of this having been pursued (personal communication). Arising out of difficulties of interview in psychiatric practice a search was made for means of communicating more fully with the patient and the Cherry and Sayers principle was developed, and owing to the rather dramatic effects of this it was decided to pursue the treatment of stammer by this means. A tiny portable tone producing apparatus was constructed which the patient could switch on and off at will so that he could hear when questioned but operate the tone when he wished to speak or read. Several cases of successful treatment using this method are described.

The electroencephalogram (EEG) recordings from the human brain are useful for detecting various brain syndromes. These recordings are typically contaminated by high amplitude eye blink artifacts, which leads to deliberate misinterpretation of the EEG signal. Recently, variational mode extraction (VME) has been used to detect eye blink artifacts. But, the VME performance is impacted by the balancing parameter and center frequency selection. Therefore, this research uses two metaheuristic algorithms, particle swarm optimization and Harris hawks optimization, to determine the optimal set of the VME parameters. In the proposed method, the optimized VME (OVME) extracts the desired mode to locate the eye blink artifactual intervals. Then, the regression analysis (REG) filters the identified artifactual intervals from short EEG data segments. The significance of the proposed OVME-REG algorithm is that it is adequate for determining the optimum values of the VME algorithm. The analysis is carried out on the CHB-MIT Scalp EEG, BCI Competition, and EEG motor movement/imagery datasets. The proposed OVME-REG method provides an improved performance for suppressing single and repeated eye blink artifacts as compared to the current approaches in terms of (a) high correlation coefficient (93.08%, 87.3%, 82.17%), respectively, (b) low value of RRMSE (0.379, 0.506, 0.502), respectively, (c) high SSIM (0.892, 0.842, 0.694), and (d) low computation time and better preservation of the EEG data.

Benign prostate hyperplasia (BPH) is a condition in older men in which the mass of tissue in the prostate gland gradually increases over the course of many years, ultimately leading to urinary outflow obstruction. Current treatment of this condition is to surgically remove the obstructing tissue. One novel alternative therapy being studied is transurethral thermocoagulation of excessive prostatic mass. In this approach, a heat-emitting catheter is placed in the prostatic urethra, and the intraprostatic segment of the catheter is heated to temperatures above 60°C for one hour. Two-dimensional cylindrical-co-ordinate computer simulations of this treatment modality were run to model resultant temperature distributions within the prostate gland and surrounding tissues. The simulations revealed that resultant tissue temperature changes were related directly to the power delivered to the catheter and inversely to the rate of blood perfusion. Further analysis of the temperature profiles produced a rapidly computable predictor of tissue temperature in the radial dimension. Using the predictor, a ‘kill radius’ around the prostatic urethra can be easily computed on-line, during treatment, from clinically available data, catheter, power and catheter temperature. The computed kill radius may serve as a useful predictor of the extent of thermal devitalisation of unwanted obstructing tissue and the long-term success of the treatment in relieving urinary outflow obstruction without surgery.