Clinical utility of ultrasound imaging for measuring anterior thigh thickness after anterior cruciate ligament injury in an individual patient to assess postsurgery outcome

The present study investigated the clinical utility of ultrasound imaging (USI) for assessing changes in an individual’s quadriceps muscle and subcutaneous fat (SF) thickness of the anterior thigh and their relative proportions. A patient was studied prior to and after anterior cruciate ligament reconstruction (ACLR) surgery and during rehabilitation. This case study involved an 18-year-old female recreational athlete with a complete tear of the anterior cruciate ligament (ACL). Tissue thickness (SF and quadriceps muscle) was measured from transverse USI of the anterior thigh before surgery, at weekly intervals during 12 weeks of postsurgery, and then every 2 weeks for the following 12 weeks (total of 21 measurement sets). Statistically significant differences presurgery to postrehabilitation were found for muscle thickness () and SF tissue thickness () measurements. There was no difference in muscle to fat ratio (). Changes in measurements greater than the reported minimal detectable change (MDC) demonstrate the sensitivity of the USI technique as an objective tool to assess clinically useful changes in an individual’s anterior thigh muscle thickness post-ACLR surgery and during rehabilitation

Down syndrome and aberrant right subclavian artery

Down syndrome (DS) may be associated with various organ system disorders. Feeding problems are frequent in children with DS and may be caused by associated defects, including congenital heart defects, gastrointestinal defects, or endocrine disorders. In the absence of these associated conditions, feeding problems are often attributed to general hypotonia. However, an aberrant right subclavian artery (ARSA), a rare vascular anomaly and an unusual cause of problems with the passage of solid food through the esophagus, has recently been suggested to occur more frequently in patients with DS. This knowledge is of importance when evaluating feeding difficulties in patients with DS. Additional investigation for identifying an ARSA may be indicated in selected patients. Diagnostic techniques, such as transthoracic echocardiography, barium contrast esophagram, angiography, or computed tomography–angiography (CT) can be used in a diagnostic flow chart. The presence of ARSA is not synonymous to the cause of feeding problems in patients with DS and corrective surgery of this vascular anomaly should be restricted to selected cases

Clinical performance of a novel textile interface for neonatal chest electrical impedance tomography

Objective: Critically ill neonates and infants might particularly benefit from continuous chest electrical impedance tomography (EIT) monitoring at the bedside. In this study a textile 32-electrode interface for neonatal EIT examination has been developed and tested to validate its clinical performance. The objectives were to assess ease of use in a clinical setting, stability of contact impedance at the electrode–skin interface and possible adverse effects. Approach: Thirty preterm infants (gestational age: 30.3 ± 3.9 week (mean ± SD), postnatal age: 13.8 ± 28.2 d, body weight at inclusion: 1727 ± 869 g) were included in this multicentre study. The electrode–skin contact impedances were measured continuously for up to 3 d and analysed during the initial 20-min phase after fastening the belt and during a 10 h measurement interval without any clinical interventions. The skin condition was assessed by attending clinicians. Main results: Our findings imply that the textile electrode interface is suitable for long-term neonatal chest EIT imaging. It does not cause any distress for the preterm infants or discomfort. Stable contact impedance of about 300 Ohm was observed immediately after fastening the electrode belt and during the subsequent 20 min period. A slight increase in contact impedance was observed over time. Tidal variation of contact impedance was less than 5 Ohm. Significance: The availability of a textile 32-electrode belt for neonatal EIT imaging with simple, fast, accurate and reproducible placement on the chest strengthens the potential of EIT to be used for regional lung monitoring in critically ill neonates and infants

A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing

Classical homogenization theory based on the Hashin-Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples, as well as by using reconstructed Electrical Impedance Tomography (EIT) images based on clinical data from an ongoing study within the EU-funded CRADL project. The theory may be potentially useful for improving the imaging algorithms and clinical evaluations in connection with lung EIT for respiratory management and monitoring in neonatal intensive care units

13th International conference on electrical bioimpedance and 8th conference on electrical impedance tomography

This issue of Physiological Measurement follows the successful 13th ICEBI conference held at the Graz University of Technology, Austria, from 29 August to 2 September 2007. It was organized jointly with the 8th Conference on Electrical Impedance Tomography. The conference was co-organized by the Impedance Imaging Research Centre (IIRC) in Seoul and the Austrian Society for Biomedical Engineering (ÖGBMT), and it was kindly endorsed by the IFMBE. The combined conferences created a platform for investigators from both research communities of bio-impedance and EIT to engage in common areas of interest whilst also allowing an opportunity for the community to broaden its outlook in the areas of bio-sensors, clinical applications and new technologies. This upholds the tradition of successful conferences on biomedical applications of electrical impedance tomography and bio-impedance. It follows the 7th Conference on Biomedical Applications of Electrical Impedance Tomography combined with the World Congress 2006, which took place in Seoul from 27 August to 1 September 2006. The next EIT conference is scheduled to take place in Dartmouth College, USA, in June 2008. This issue contains papers produced from discussion and feedback during the conference in both bio-impedance and EIT research areas. It was also an opportunity for new researchers to join the community and propose recent innovations. Of the 259 papers presented at the conference, Springer Verlag published 207 in the IFMBE proceedings. All authors were invited to prepare new papers for inclusion in this issue of Physiological Measurement. The manuscripts were put through a process of careful review before selection. A total of 43 were accepted, covering an important range of topics from bio-impedance, hardware, algorithms, new technologies and clinical applications. From the scientific point of view, bio-impedance has a very long tradition that dates back to the days of Maxwell. Nevertheless, until the end of the 20th century, research was focused on the development of methods and basic experimental work while clinical or other practical applications remained limited. Consequently, there were not so many companies interested enough to produce professional equipment for easy and reliable data collection and interpretation. This may appear surprising as bio-impedance reflects so many (patho-) physiological processes, but on the other hand, a number of proposed applications, though sensitive, still exhibit low specificity, especially when aimed at processes far from the body surface. The 2007 conference may have shown a slight change of tendency. From 2000 to 2006, the number of papers cited in Medline and containing the keywords 'bio-impedance' or 'impedance tomography' increased by 56%. At the same time, we face an increasing number of applications related to micro- and nano-technologies that have emerged along with the tremendous growth of biochemical and cellular engineering. In recent years both the number of newly founded companies for bio-impedance devices and the involvement of established companies in bio-impedance research have increased. The papers included in this year's issue clearly reflect this. New developments and trends are visible, such as non-contact methods using magnetic fields; MREIT, bringing together EIT and magnetic resonance imaging; and magnetic induction tomography (MIT), clinical applications, bio-impedance spectroscopy, new hardware and algorithms. The presentations of these new technologies continue to grow and it will be interesting to see how these contribute to future clinical applications. At this conference, clinical applications were strongly represented; they included brain function, breast imaging, and thorax and gastric applications. It is important that researchers do not neglect the challenges of clinical applications of bio-impedance and EIT as there are still many technical difficulties that the technology needs to overcome in order to provide valuable clinical tools; however, there are promising signs that these tools are close to realization. The future of both EIT and bio-impedance continues to provide researchers with new challenges. The high quality of research papers in this special issue shows clear evidence of significant advances in this research field

Dynamic electrical impedance tomography image reconstruction of neonate lung function based on linear Kalman filter techniques

Electrical impedance Tomography (EIT) has great potential as a low cost continuous monitoring system for neonate lung function. However EIT data obtained from clinical measurements are inherently noisy and require reconstruction algorithms that are robust enough to cope with these difficulties. In this paper, we examine the potential of a linear Kalman approach for EIT difference imaging. Simulated data is used for the reconstruction process; real time-data is being tested and the results will be introduced at a latter stage of this research. Our objective is to use this initial research to develop a nonlinear Kalman filter for frequency difference imaging of neonate lung function

Comparison of a new integrated current source with the modified Howland circuit for EIT applications

Multi-frequency electrical impedance tomography (MF-EIT) systems require current sources that are accurate over a wide frequency range (1 MHz) and with large load impedance variations. The most commonly employed current source design in EIT systems is the modified Howland circuit (MHC). The MHC requires tight matching of resistors to achieve high output impedance and may suffer from instability over a wide frequency range in an integrated solution. In this paper, we introduce a new integrated current source design in CMOS technology and compare its performance with the MHC. The new integrated design has advantages over the MHC in terms of power consumption and area. The output current and the output impedance of both circuits were determined through simulations and measurements over the frequency range of 10 kHz to 1 MHz. For frequencies up to 1 MHz, the measured maximum variation of the output current for the integrated current source is 0.8% whereas for the MHC the corresponding value is 1.5%. Although the integrated current source has an output impedance greater than 1 MΩ up to 1 MHz in simulations, in practice, the impedance is greater than 160 kΩ up to 1 MHz due to the presence of stray capacitance