A comparison of sensors for minimizing the primary signal in planar-array magnetic induction tomography

In magnetic induction tomography reducing the influence of the primary excitation field on the sensors can provide a significant improvement in SNR and/or allow the operating frequency to be reduced. For the purposes of imaging, it would be valuable if all, or a useful subset, of the detection coils could be rendered insensitive to the primary field for any excitation coil activated. Suitable schemes which have been previously suggested include the use of axial gradiometers and coil-orientation methods (Bx sensors). This paper examines the relative performance of each method through computer simulation of the sensitivity profiles produced by a single sensor, and comparison of reconstructed images produced by sensor arrays. A finite-difference model was used to determine the sensitivity profiles obtained with each type of sensor arrangement. The modelled volume was a cuboid of dimensions 50 cmx50 cmx12 cm with a uniform conductivity of 1 S m-1. The excitation coils were of 5 cm diameter and the detection coils of 5 mm diameter. The Bx sensors provided greater sensitivity than the axial gradiometers at all depths, other than on the surface layer of the volume. Images produced using a single-planar array were found to contain distortion which was reduced by the addition of a second array.

Design and performance of a planar-array MIT system with normal sensor alignment

In this study the performance of a planar array for magnetic induction tomography (MIT) was investigated and the results of measurements to determine the precision and sensitivity of the sensor were undertaken. A planar-array MIT system utilizing flux-linkage minimization for the primary field has been constructed and evaluated. The system comprises 4 printed excitation coils of 4 turns which were shielded, 8 surface-mount inductors of inductance 10 microH as sensor, mounted such that in principle no primary-field flux threads them, and a calibration coil to produce a strong primary field. The excitation current was multiplexed via relays to drive the excitation and reference coils. The noise values were similar in real and imaginary components in the lower frequencies and the factor to which the primary field could be reduced was greatest in the nearest coil. Methods for determining the true real and imaginary components and for flux-linkage minimization for the primary field for variations in channel sensitivities are described and the results of measurements of the system's noise and drift are given. A SNR of 47 dB was observed at 4 MHz when a 0.3 Sm-1 saline filled tank of dimensions 20 cmx20 cmx10 cm was placed centrally over the array. Finally, images were reconstructed from measurements of saline samples in a free space background, with the samples moved past the array in 21 1 cm steps to emulate mechanical scanning of the array. The image reconstruction characteristics of the planar array in conjunction with the reconstruction technique employed are discussed.

A primary field compensation scheme for planar array magnetic induction tomography

In biomedical magnetic induction tomography (MIT), measurement precision may be improved by incorporating some form of primary field compensation/cancellation scheme. Schemes which have been described previously include gradiometric approaches and the use of 'back-off' coils. In each of these methods, however, the primary field cancellation was achieved only for a single transmitter/receiver combination. For the purpose of imaging, it would be desirable for a fully electronically scanned MIT system to provide a complete set of measurements, all with the primary field cancelled. A single channel suitable for incorporation into an MIT system with planar-array geometry is described. The transmitter is a 6-turn coil of wire 5 cm in diameter. The receiver is a surface mount inductor, of inductance 10 microH, mounted such that, in principle, no net primary field flux threads it. The results of measurements carried out with the single channel system suggest that the signal due to the primary excitation field can be reduced on average by a factor of 298 by the sensor geometry over the operating frequency range 1-10 MHz. The standard deviation and drift of the signal with the system adjusted for maximum primary field cancellation, expressed as a percentage of the signal when the receiver coil was rotated until its axis of sensitivity lay along the primary field, were 0.0009% and 0.009%, respectively. The filter time constant used was 30 ms.

CLIC-2 modulates cardiac ryanodine receptor Ca2+ release channels

We have examined the biochemical and functional properties of the recently identified, uncharacterised CLIC-2 protein. Sequence alignments showed that CLIC-2 has a high degree of sequence similarity with CLIC-1 and some similarity to the omega class of glutathione transferases (GSTO). A homology model of CLIC-2 based on the crystal structure of CLIC-1 suggests that CLIC-2 belongs to the GST structural family but, unlike the GSTs, CLIC-2 exists as a monomer. It also has an unusual enzyme activity profile. While the CXXC active site motif is conserved between CLIC-2 and the glutaredoxins, no thiol transferase activity was detected. In contrast, low glutathione peroxidase activity was recorded. CLIC-2 was found to be widely distributed in tissues including heart and skeletal muscle. Functional studies showed that CLIC-2 inhibited cardiac ryanodine receptor Ca2+ release channels in lipid bilayers when added to the cytoplasmic side of the channels and inhibited Ca2+ release from cardiac sarcoplasmic reticulum vesicles. The inhibition of RyR channels was reversed by removing CLIC-2 from the solution or by adding an anti-CLIC-2 antibody. The results suggest that one function of CLIC-2 might be to limit Ca2+ release from internal stores in cells.

The risk of complications of uveitis in a district hospital cohort

AIMS

To establish the frequency and risk factors for visual loss in a primary referral cohort of hospital patients with uveitis.

METHODS

561 consecutive uveitis patients attending three district hospitals were recruited and the acuity at the end of the study period recorded. A retrospective case-control study of risk factors for visual loss (permanent loss of acuity <6/9) was performed. Risk factors examined included type of uveitis, age at onset of uveitis, race, type of systemic inflammatory disease, length of follow up, and treatment variables.

RESULTS

Visual loss of at least 6/12 in one eye was found in 111 patients (19.9%). Only four patients (0.7%) suffered severe bilateral visual loss (6/36 or less). Visual loss was associated with age at onset >60 years (odds ratio 3.9, 95% confidence interval (CI) 2.2 to 7.0, long follow up 2.0 (1.2 to 3.3) and a history of cataract surgery 3.9 (2.1 to 7.2). It was less likely in patients with acute anterior uveitis 0.2 (0.1 to 0.3).

CONCLUSION

The frequency of visual loss associated with uveitis in a district hospital cohort is less than that found in referral centres and levels of legal blindness are low. Although acute anterior uveitis has a low frequency of visual loss it contributes significantly to the total burden. The ocular co-morbidity of the elderly may contribute to the increased visual loss of late onset uveitis.

Hypercalcaemia in infancy; a presenting feature of spinal muscular atrophy

A 10 month old girl presented with a history of constipation from early life. She was found to be hypercalcaemic with hypercalciuria and nephrocalcinosis. Her mild motor delay and hypotonia were thought to be linked to chronic hypercalcaemia, but when these features failed to improve despite normocalcaemia on a low calcium diet the possibility of neuromuscular disease was explored in more detail. She was subsequently found to have spinal muscular atrophy type 2. We suspect that the hypercalcaemia with hypercalciuria observed in this case reflects altered bone turnover secondary to reduced muscular activity.

An analytical method for shipboard extraction of the odour compounds, 2-methylisoborneol and geosmin

Extractions for the analysis of geosmin and 2-methylisoborneol (MIB) were carried out on board a research vessel by extracting water samples in the collection bottles with dichloromethane. The extracts are stable and can be stored for up to two months with no apparent loss of analytes. Workup and analysis could be done at the rate 15-20 samples per week. Approximately 150 samples from Lake Ontario were analyzed in 2000 and 120 samples in 2001. Concentrations as low as 1 ng/L could be detected, but reliable determination was only attained above 5 ng/L (> 80% qualifier ion match within +/- 50%). Reproducibility between duplicates was generally better than 10%, and recovery of surrogate standards from reagent water averaged ca. 80% and from lake water ca. 60%. In early September, 2000, geosmin concentrations in Lake Ontario ranged from 1-13 ng/L and MIB from 1-31 ng/L. In 2001, the ranges were 1-47 and 1-56 ng/L for geosmin and MIB, respectively. Lowest concentrations occurred in the western and central regions and highest concentrations in the eastern region and St Lawrence River.

Mentor preparation: reasons for undertaking the course and expectations of the candidates

This study sought to explore the assumption that potential participants to do the English National Board Teaching and Assessing in Clinical Practice course (ENB 998) were motivated to undertake the programme by a commitment to become a mentor. Two cohorts of students (n=127) were invited to complete a specifically constructed questionnaire and the majority responded (n=115, response rate 90.6%). The results were analysed using SPSS v10 [SPSS Inc., SPSS for Windows, 1999]. The findings suggest that commitment to undertaking the role of the mentor was not the only motivator for those undertaking this programme of preparation. Fifty-eight percentage (n=67) identified enhanced job prospects as a benefit of the course. Recommendations are made that the course should not be universally required for promotion and that it be, solely, identified as a course for mentor preparation. It is also recognised that this approach requires a national movement in this area if it is to succeed.

Multiple actions of imperatoxin A on ryanodine receptors: interactions with the II-III loop "A" fragment

Imperatoxin A is a high affinity activator of ryanodine receptors. The toxin contains a positively charged surface structure similar to that of the A fragment of skeletal dihydropyridine receptors (peptide A), suggesting that the toxin and peptide could bind to a common site on the ryanodine receptor. However, the question of a common binding site has not been resolved, and the concentration dependence of the actions of the toxin has not been fully explored. We characterize two novel high affinity actions of the toxin on the transient gating of cardiac and skeletal channels, in addition to the well documented lower affinity induction of prolonged substates. Transient activity was (a) enhanced with 0.2-10 nm toxin and (b) depressed by >50 nm toxin. The toxin at >/=1 nm enhanced Ca(2+) release from SR in a manner consistent with two independent activation processes. The effects of the toxin on transient activity, as well as the toxin-induced substate, were independent of cytoplasmic Ca(2+) or Mg(2+) concentrations or the presence of adenine nucleotide and were seen in diisothiocyanostilbene-2',2'-disulfonic acid-modified channels. Peptide A activated skeletal and cardiac channels with 100 nm cytoplasmic Ca(2+) and competed with Imperatoxin A in the high affinity enhancement of transient channel activity and Ca(2+) release from SR. In contrast to transient activity, prolonged substate openings induced by the toxin were not altered in the presence of peptide A. The results suggest that Imperatoxin A has three independent actions on ryanodine receptor channels and competes with peptide A for at least one action.

Bipolar disorder ignored by the Mental Health National Service framework but not forgotten by the British Association for Psychopharmacology

Bipolar disorder (BD) is a severe mental illness that has been largely ignored by the National Service Framework (NSF) for Mental Health. This is particularly notable because it is associated with a higher suicide rate than schizophrenia and has a greater burden of disability. The NSF offers little guidance on service models that specifically consider BD. This is of concern because of the complexities that are inherent in the management of BD. These deficiencies in the NSF may have far-reaching implications for resource allocation, service organization, and patient management and well-being. Moreover, the standards and performance targets laid out in the NSF will be difficult to meet if this important and common mental illness is not specifically catered for in mental health services. Local Implementation Teams would be well advised to take note of the recently published British Association for Psychopharmacology guidelines for the management of BD.

Staphylococcal species in the oral cavity from patients in a regional burns unit

The aim of this study was to perform a quantitative and qualitative analysis of oral carriage of staphylococci in a range of oral specimens from patients admitted to a regional burns unit. The study recruited 28 patients and reasons for admittance were: burns (46%), skin grafting (39%), lacerations (7%), scalding (4%) and necrotizing fasciitis (4%). No patient had smoke inhalation injuries or trauma to the oro-pharynx. There were five patients from whom methicillin-sensitive S. aureus (MRSA) could be detected in oral specimens. For three patients only the wound and oral specimens were positive for MRSA. In one patient only the oral specimens were positive for MRSA. There were five patients from whom methicillin-sensitive S. aureus (MRSA) could be detected in the oral specimens. In one patient only the oral specimens were positive for MSSA. Staphylococci could be recovered from the dental plaque, denture and toothbrush specimens with a mean count of 1.1 x 10(4)cfu/mL (range 20-5.3 x 10(4)), 5.4 x 10(3) (range 40-2.1 x 10(4)) and 264 cfu/mL (range 20-500), respectively. Both MSSA and MRSA could be recovered from these specimen types. In one patient only the toothbrush was positive for MRSA and all other oral specimens were negative. This study suggests that staphylococci are not infrequent colonizers of the oral cavity, and that this site may serve as a potential reservoir for transmission to other body sites.

Expression of p53, pRB, and p16 in lung tumours: a validation study on tissue microarrays

Tissue microarrays have been created from 326 lung tumours, including 173 squamous cell carcinomas (SCCs) and 132 adenocarcinomas (ADs). In order to evaluate the usefulness of this microarray series, the expression of p53, p16, and Rb proteins was compared by immunohistochemistry on both the tissue microarrays and the corresponding whole sections for all 326 tumours. The presence of replicate punches improved both the yield and the concordance of data relative to the whole section results, so that the consensus score from the replicates agreed with the whole section result in more than 90% of informative tumours. The large number of tumours in this series also allowed significant differences in protein expression patterns to be detected between SCC and AD, the major subtypes of non-small cell lung carcinoma (NSCLC). SCC had higher levels of p53 staining (67% vs 52% in AD) and substantially increased p16 loss (SCC 75%, AD 53%) combined with greater retention of pRB expression (SCC 86% vs 67% in AD). The strong inverse correlation between p16 and pRB seen in SCC was essentially absent in AD. This study represents the largest single immunohistochemical survey of protein expression for p53, p16, and RB in NSCLCs.