Hydrophilins in the filamentous fungus Neosartorya fischeri (Aspergillus fischeri) have protective activity against several types of microbial water stress.

Hydrophilins are proteins that occur in all domains of life and protect cells and organisms against drought and other stresses. They include most of the late embryogenesis abundant (LEA) proteins and the heat shock protein (HSP) Hsp12. Here, the role of a predicted LEA-like protein (LeamA) and two Hsp12 proteins (Hsp12A and Hsp12B) of Neosartorya fischeri was studied. This filamentous fungus forms ascospores that belong to the most stress-resistant eukaryotic cells described to date. Heterologous expression of LeamA, Hsp12A and Hsp12B resulted in increased tolerance against salt and osmotic stress in Escherichia coli. These proteins were also shown to protect lactate dehydrogenase against dry heat and freeze-thaw cycles in vitro. Deletion of leamA caused diminished viability of sexual ascospores after drought and heat. This is the first report on functionality of Hsp12 and putative LeamA proteins derived from filamentous fungi, and their possible role in N. fischeri ascospore resistance against desiccation, high temperature and osmotic stress is discussed.

Computed tomographic features of feline sino-nasal and sino-orbital aspergillosis.

Feline upper respiratory tract aspergillosis (URTA) occurs as two distinct anatomical forms, namely, sino-nasal aspergillosis (SNA) and sino-orbital aspergillosis (SOA). An emerging pathogen, Aspergillus felis, is frequently involved. The pathogenesis of URTA, in particular the relationship between the infecting isolate and outcome, is poorly understood. In this study, computed tomography was used to investigate the route of fungal infection and extension in 16 cases (SNA n = 7, SOA n = 9) where the infecting isolate had been identified by molecular testing. All cases had nasal cavity involvement except for one cat with SNA that had unilateral frontal sinus changes. There was a strong association between the infecting species and anatomic form (P = 0.005). A. fumigatus infections remained within the sino-nasal cavity, while cryptic species infections were associated with orbital and paranasal soft-tissue involvement and with orbital lysis. Cryptic species were further associated with a mass in the nasal cavity, paranasal sinuses or nasopharynx. Orbital masses showed heterogeneous contrast enhancement, with central coalescing hypoattenuating foci and peripheral rim enhancement. Severe, cavitated turbinate lysis, typical of canine SNA, was present only in cats with SNA. These findings support the hypothesis that the nasal cavity is the portal of entry for fungal spores in feline URTA and that the route of extension to involve the orbit is via direct naso-orbital communication from bone lysis. Additionally, a pathogenic role for A. wyomingensis and a sinolith in a cat with A. udagawae infection are reported for the first time.

Water- and air-distributed conidia differ in sterol content and cytoplasmic microviscosity.

Airborne and waterborne fungal spores were compared with respect to cytoplasmic viscosity and the presence of ergosterol. These parameters differed markedly between the two spore types and correlated with spore survival. This suggests that the mode of spore dispersal has a bearing on cellular composition, which is relevant for the eradication of industrially relevant fungal propagules.

Feasibility study on the MammoSite in early-stage breast cancer: initial experience.

The aims of this study were to evaluate the feasibility, practicality, efficacy and safety of the delivery of accelerated partial breast irradiation using the MammoSite for the boost phase. Six patients aged 53-69 years with stage T1N0, T2N0, Grade I-II invasive ductal carcinoma received 9-10 Gy prescribed at 1 cm from the MammoSite balloon surface in two fractions of 4.5-5 Gy 6 h apart. The MammoSite was inserted 20-37 days postoperatively. External beam radiation therapy to the whole breast commenced 1-5 days after accelerated partial breast irradiation. The maximum skin dose ranged from 3 to 9 Gy. The skin-cavity distance ranged from 7 to 19 mm. Local discomfort resolved as the scar healed spontaneously within 3-5 days. No Grade III or higher acute toxicity or local infection was recorded. The ease of insertion and accuracy of dosimetry makes the MammoSite suitable for use in properly selected women with early-stage breast cancer in a trial setting.

Tumour resistance to cisplatin: a modelling approach.

Although chemotherapy has revolutionized the treatment of haematological tumours, in many common solid tumours the success has been limited. Some of the reasons for the limitations are: the timing of drug delivery, resistance to the drug, repopulation between cycles of chemotherapy and the lack of complete understanding of the pharmacokinetics and pharmacodynamics of a specific agent. Cisplatin is among the most effective cytotoxic agents used in head and neck cancer treatments. When modelling cisplatin as a single agent, the properties of cisplatin only have to be taken into account, reducing the number of assumptions that are considered in the generalized chemotherapy models. The aim of the present paper is to model the biological effect of cisplatin and to simulate the consequence of cisplatin resistance on tumour control. The 'treated' tumour is a squamous cell carcinoma of the head and neck, previously grown by computer-based Monte Carlo techniques. The model maintained the biological constitution of a tumour through the generation of stem cells, proliferating cells and non-proliferating cells. Cell kinetic parameters (mean cell cycle time, cell loss factor, thymidine labelling index) were also consistent with the literature. A sensitivity study on the contribution of various mechanisms leading to drug resistance is undertaken. To quantify the extent of drug resistance, the cisplatin resistance factor (CRF) is defined as the ratio between the number of surviving cells of the resistant population and the number of surviving cells of the sensitive population, determined after the same treatment time. It is shown that there is a supra-linear dependence of CRF on the percentage of cisplatin-DNA adducts formed, and a sigmoid-like dependence between CRF and the percentage of cells killed in resistant tumours. Drug resistance is shown to be a cumulative process which eventually can overcome tumour regression leading to treatment failure.

The linear accelerator mechanical and radiation isocentre assessment with an electronic portal imaging device (EPID).

Regular checks on the performance of radiotherapy treatment units are essential and a variety of protocols has been published. These protocols identify that the determination of isocentre must be accurate and unambiguous since both the localization of a radiation field on a patient and positioning aids are referenced to it. An EPID (BIS 710) with a combined light and radiation scintillation detector screen was used to assess mechanical and radiation isocentres for different collimator and gantry angles. Crosshair positions within light field images were determined from fitted Gaussian intensity profiles and then used to calculate the displacement of the mechanical isocentre. For comparison, the position of the crosshair was also recorded on a graph paper. The radiation field centre was first calculated from the set up geometry for given gantry/collimator angles and then compared with measured values to assess the displacement of the radiation isocentre. The radiation isocentre was also checked by locating a marker, positioned on the couch, on the EPID radiation images for different treatment couch angles. The mechanical and radiation isocentres were determined from the EPID light field and radiation images respectively with an accuracy of 0.3 mm using simple PC based programs. The study has demonstrated the feasibility of using the EPID to assess mechanical and radiation isocentres of a linear accelerator in a quick and efficient way with a higher degree of accuracy achieved as compared to more conventional methods, e.g. the star shot.

First photon detection in time-resolved transillumination imaging: a theoretical evaluation.

First photon detection, as a special case of time-resolved transillumination imaging, is studied through the derivation of the temporal probability density function (pdf) for the first arriving photon. The pdf for different laser intensities, media and second and later arriving photons were generated. The arrival time of the first detected photon reduced as the laser power increased and also when the scattering and absorption coefficients decreased. The pdf for an imbedded totally absorbing 3 mm inhomogeneity may be distinguished from the pdf of a homogeneous turbid medium similar to that of human breast in dimensions and optical properties.

Modelling of post-irradiation accelerated repopulation in squamous cell carcinomas.

The mechanisms postulated to be responsible for the accelerated repopulation of squamous cell carcinomas during radiotherapy are the loss of asymmetry of stem cell division, acceleration of stem cell division, abortive division and/or recruitment of the non-cycling cell with proliferative capacity. Although accelerated repopulation was observed with recruitment and accelerated cell cycles, it was not sufficient to cause an observable change to the survival curve. However, modelling the loss of asymmetry in stem cell division has reshaped the curve with a 'growth' shoulder. Cell recruitment was not found to be a major contributor to accelerated tumour repopulation. A more significant contribution was provided through the multiplication of surviving tumour stem cells during radiotherapy, by reducing their cell cycle time, and due to loss of asymmetry of stem cell division.

Quality of life and metabolic control in patients with diabetes mellitus type 1 treated by continuous subcutaneous insulin infusion or multiple daily insulin injections.

OBJECTIVE: To assess the quality of life and metabolic control in patients with diabetes mellitus type 1 on continuous subcutaneous insulin infusion (CSII) in comparison with patients on multiple daily insulin injections (MDII). RESEARCH DESIGN AND METHODS: The study included 49 patients (13 males, 36 females), aged 41.4+/-11.3 years (mean+/-SD) on CSII for >1 year and 79 patients (43 males, 36 females), aged 43.1+/-14.8 years on MDII for >1 year, from three Dutch diabetic clinics. There were no statistically significant differences in duration of diabetes, social class, level of education, marital status, smoking or recent admissions to hospital. The questionnaires used were a Diabetes Quality of Life scale adapted from the DCCT, the Diabetes Satisfaction Questionnaire (DTSQ), and the WHO Well-Being Questionnaire. HbA1c was measured with an HPLC method (reference range 4.3 to 6.1 %). RESULTS: Using two-sided t-tests no statiscally significant differences were found between the patients on CSII and MDII with respect to quality of life (version A (<30 years) 4.32+/-0.22 vs 4.20+/-0.30; version B (> or =30 years) 4.18+/-0.25 vs 4.29+/-0.28), well-being (48.59+/-9.23 vs 50.99 +/-8.70), satisfaction with treatment (5.10+/-0.69 vs 5.15+/-0.71) and HbA1c (8.14+/-1.51 vs 8.47+/-1.40). Frequency of daily blood glucose monitoring was slightly higher in CSII than in MDII patients (4.52+/-1.19 vs 3.60+/-1.47; p<0.0001). CONCLUSION: The present data indicate that patients on CSII have similar QoL based on questionnaires when compared with patients on MDII. These data suggest that in patients with less optimal control on MDII, converting the treatment strategy to CSII is not associated with decreased quality of life.

Spatial resolution in fast time-resolved transillumination imaging: an indeterministic Monte Carlo approach.

The spatial resolution achievable in time-resolved optical transillumination imaging through a turbid (scattering and absorbing) medium has been reassessed theoretically. The temporal point spread function was constructed assuming a delta function input pulse, a approximately 50 mm thick medium and a small detector with zero risetime. Temporal profiles were derived from an indeterministic Monte Carlo simulation for different time scales. From the temporal point spread function (TPSF), an analytic edge response function from which the spatial resolution was determined was derived. Previous analytical methods for determining the spatial resolution are approximations for very short flight times (sub-100 ps time region). The results show that a spatial resolution of about two millimetres is possible under ideal signal-to-noise ratio conditions and with detector gate times of the order of ten picoseconds. If this predicted spatial resolution can be achieved in an imaging system, it may be possible to improve the diagnosis of breast tumours.

Assessment of flatness and symmetry of megavoltage x-ray beam with an electronic portal imaging device (EPID).

The input/output characteristics of the Wellhofer BIS 710 electronic portal imaging device (EPID) have been investigated to establish its efficacy for periodic quality assurance (QA) applications. Calibration curves have been determined for the energy fluence incident on the detector versus the pixel values. The effect of the charge coupled device (CCD) camera sampling time and beam parameters (such as beam field size, dose rate, photon energy) on the calibration have been investigated for a region of interest (ROI) around the central beam axis. The results demonstrate that the pixel output is a linear function of the incident exposure, as expected for a video-based electronic portal imaging system. The field size effects of the BIS 710 are similar to that of an ion chamber for smaller field sizes up to 10 x 10 cm2. However, for larger field sizes the pixel value increases more rapidly. Furthermore, the system is slightly sensitive to dose rate and is also energy dependent The BIS 710 has been used in the current study to develop a QA procedure for measurements of flatness and symmetry of a linac x-ray beam. As a two-dimensional image of the radiation field is obtained from a single exposure of the BIS 710, a technique has been developed to calculate flatness and symmetry from a defined radiation area. The flatness and symmetry values obtained are different from those calculated conventionally from major axes only (inplane, crossplane). This demonstrates that the technique can pick up the "cold" and "hot" spots in the analysed area, providing thus more information about the radiation beam. When calibrated against the water tank measurements, the BIS 710 can be used as a secondary device to monitor the x-ray beam flatness and symmetry.

An indeterministic Monte Carlo technique for fast time of flight photon transport through optically thick turbid media.

A time-resolved indeterministic Monte Carlo (IMC) simulation technique is proposed for the efficient construction of the early part of the temporal point spread function (TPSF) of visible or near infrared photons transmitted through an optically thick scattering medium. By assuming a detected photon is a superposition of photon components, the photon is repropagated from a point in the original path where a significant delay in forward propagation occurred. A weight is then associated with each subsequently detected photon to compensate for shorter components. The technique is shown to reduce the computation time by a factor of at least 4 when simulating the sub-200 picosecond region of the TPSF and hence provides a useful tool for analysis of single photon detection in transillumination imaging.

Growth of a virtual tumour using probabilistic methods of cell generation.

A study into treatment enhancement in combined chemo-radiotherapy for unresectable head and neck cancer has initiated the development of a computer model of tumour growth. The model is based on biological parameters, and characterises tumour growth prior to chemo-radiotherapy. Tumour growth starting from a single stem cell is modelled using the Monte Carlo method. The type of the cell function, their relative proportions on mitosis, their proliferative capacity, the duration of the four phases of the cell cycle, the mean cell cycle time, and the cell loss due to natural causes are the main parameters of the basic model. A Gaussian distribution function operates in establishing the cell cycle time, with a mean value of 33 hours, while the cell type is sampled from a uniform distribution. With the established model, the sensitivity of the developed tumour's cell population to the stem, proliferative and nonproliferative ratio at mitosis was assessed. The present model accurately reflects the exponential distribution of cells along the cell cycle (70% cells in GI phase, 15% in S, 10% in G2, 5% in M) of a developed tumour as described in the literature. The proportion of stem, finitely proliferating and resting cells during tumour growth is maintained within their biological limits (2% stem, 13% finitely proliferating, 85% nonproliferating cells). The ratio (R = 3) between the time necessary to develop a clinically detectable tumour (10(9) cells) and the further time to grow to its lethal size (10(12) cells) is in accordance with the biological data when tumour volume is compared for the two periods (30 doublings and 10 doublings respectively). In conclusion, computer simulation can illustrate the biological growth of a tumour and the cell distribution along the cell cycle. These distributions may then be used in the assessment of tumour response to radiotherapy and to specific chemotherapeutic agents.

A design for a dual assembly multileaf collimator.

A multileaf collimator for radiation therapy has been designed that splits each leaf bank into two vertically displaced levels with each level consisting of alternate leaves and leaf spaces. The leaves in the upper level shield the spaces in the lower level. Each level can move laterally, in the direction perpendicular to leaf motion by one leaf width. Following lateral movement of one level, the leaves align with the other level and radiation is transmitted through the collimator as multiple slit fields in a grid pattern. This transmission can be used to form an image of the external anatomy and would enable double-exposure portal images to be acquired much more rapidly than at present. These could potentially be acquired during the treatment delivery. The radiation profiles transmitted for image formation through the collimator design were investigated. Individual and grid pattern slit field profiles formed by tungsten and lead alloy collimators were measured with varying slit width, source-collimator distance, collimator-detector distance, and collimation thickness. The slit width was found to have the major influence on the transmitted profiles. As the slit width decreases the profiles become broader than the geometric slit projection resulting in increasing overlap of adjacent profiles. The overlap results in a modulated image of the external anatomy for small slit widths, rather than a sampled or "grid" image for larger widths. The shielding of this design was found to be adequate provided the leaf faces of the adjacent vertically displaced leaves are at least aligned, therefore an overlap or tongue and groove is not required.

Evaluation of an algorithm for the assessment of the MTF using an edge method.

An algorithm to calculate the presampling modulation transfer function (MTF) of an imaging system from an angled edge image has its own inherent transfer function. Factors such as the angle of the sampling aperture to the edge, registration of edge function profiles using the determined edge angle, differentiation, smoothing, and folding all combine to produce the frequency response of the algorithm. In this work, the profile registration transfer function accounting for an error in the determined edge angle has been derived. This has been incorporated with other, previously reported, algorithm component transfer functions to fully characterize the MTF calculation algorithm. When registering profiles, small errors in the edge angle determination were found to result in large errors in the MTF, as the misalignment errors increase with the number of profiles. For example, registering 50 profiles a 0.07 degree error in a 7 degree edge angle (1% error) produces a 36% error in the MTF at the system cutoff frequency f=f(c) when profiles are oversampled at a frequency f(s)=8f(c)(f(c) is defined as the maximum frequency reproducible without aliasing when sampling at the limiting system Nyquist frequency f(s) = 2f(c)). These results highlight the importance of quantifying the transfer function of the algorithm used to determine an imaging system modulation transfer function. The MTF calculation algorithm and the transfer function analysis have been incorporated into a Windows-based software program to be made available for general use.

Evaluation of the mechanical alignment of a linear accelerator with an electronic portal imaging device (EPID).

Mechanical misalignment of a medical linear accelerator can be caused by any combination of source position displacement relative to the collimator rotational axis, collimator jaw asymmetry, or when the rotational axes of the gantry and the collimator do not intersect. A test procedure sensitive to all of these problems has been developed using an Electronic Portal Imaging Device (EPID). Each marker is placed on top of the EPID housing and on the treatment couch, then two images are acquired for gantry positions 180 degrees apart. By comparing the positions of the markers and their distances to the beam centre, mechanical alignment of the linear accelerator can be assessed. By comparing the positions of the beam centre for another two images acquired at collimator angles 180 degrees apart, the three potential sources of misalignment can be distinguished. Results with Siemens' Beam View were presented and determination accuracy of better than 0.25 mm can be achieved.

Mass screening of Irish wolfhound puppies for portosystemic shunts by the dynamic bile acid test.

Five hundred and sixty-six Irish wolfhound puppies aged six to 15 weeks were tested for congenital portosystemic shunts by the dynamic bile acid method. Plasma ammonia concentration was also measured in 165 of the puppies both fasting and postprandially. Nineteen puppies (3.4 per cent), nine males and 10 females, had portosystemic shunts. Smaller litters appeared to be more likely to contain affected puppies. The postprandial bile acid concentration was a reliable predictor of the presence of a shunt, with the highest concentration in a normal puppy being 38 mumol/litre and the lowest in an affected puppy being 43 mumol/litre. In contrast, fasting bile acid concentrations were normal in the majority of the affected puppies. There was considerable overlap in fasting plasma ammonia concentrations between normal and affected puppies (26 puppies, 15.8 per cent of those tested). Postprandial ammonia concentration appeared to give better separation between the two groups, apart from two individuals which produced bizarre results. It was concluded that the postprandial or dynamic bile acid test is an appropriate test for the mass screening of Irish wolfhound puppies for portosystemic shunts, and guidelines are proposed for the interpretation and follow-up of the test.

Development of a CCD array imaging system for measurement of dose distributions in doped agarose gels.

An imaging system for agarose gel sections has been investigated for applications in rapid two-dimensional radiation dosimetry. The imaging system, with white light illumination and CCD camera detection, was designed for measurement of the radiation-induced optical density changes in iron- and xylenol orange dye-doped agarose gels. The performance of the imaging system was compared with that of a laser scanning system for the gels and with the accepted dosimetry standard, the ionization chamber. In measurement of beam profiles of two therapeutic radiation fields, relative dose values from the CCD camera imaging system were on average within 3% ranging from 0.005% to 7.5%) of values recorded with a parallel plate ionization chamber. In comparison with the laser scanner, the CCD camera imaging system provided comparable spatial resolution and an increased rate of data acquisition, although a consistently reduced signal to noise ratio was observed. Suggestions for improving the camera imaging technique include noise reduction through camera cooling and further frame averaging.

A Monte Carlo model for bone mineral measurement using dual energy X-ray absorptiometry.

A detailed Monte Carlo model designed to simulate bone mineral measurements using a typical K-edge DEXA technique (LUNAR DPX-L bone densitometer) has been developed. Factors considered in the model include measurement geometry, K-edge filtration of the X-ray spectrum, photon statistics, count rate corrections and detector resolution. Two semi infinite elliptical phantoms simulating the lumbar spine and the femoral neck respectively have been used. Each phantom consists of four tissue components-fat, lean soft tissue, cortical bone and trabecular bone. Model results display similar levels of accuracy and precision to those observed in clinical practice. The Monte Carlo model of bone mineral measurements provides a valid tool for study of the LUNAR DPX-L DEXA technique.

A three-dimensional NMR imaging scheme utilizing doubly resonant gradient coils.

A 3DFT gradient-echo technique has been developed which, in conjunction with series-resonant gradient-coil circuits, can produce three-dimensional NMR images with an echo time of less than 100 microseconds. The method involves a read-gradient waveform composed of two sinusoids of different frequencies. This is an improvement on previous imaging sequences using a single sinusoid where only half of k space was sampled and where the second half was calculated using conjugate symmetry. The inaccuracies involved in the necessary "cut and paste" of k space inevitably lead to artifacts in the final image. The important features of the new method are that with suitable phase encoding all octants of k space are sampled, the RF pulse is applied when the gradients are all zero, and the echo forms when the gradient is essentially constant. This method will allow more extensive application of solid imaging techniques to biological samples in vivo.