Optimization of image quality and patient dose in radiographs of paediatric extremities using direct digital radiography.

OBJECTIVE: The purpose of this study was to evaluate the effect of beam quality on the image quality (IQ) of ankle radiographs of paediatric patients in the age range of 0-1 year whilst maintaining constant effective dose (ED). METHODS: Lateral ankle radiographs of an infant foot phantom were taken at a range of tube potentials (40.0-64.5 kVp) with and without 0.1-mm copper (Cu) filtration using a Trixell Pixium 4600 detector (Trixell, Morains, France). ED to the patient was computed for the default exposure parameters using PCXMC v. 2.0 and was fixed for other beam qualities by modulating the tube current-time product. The contrast-to-noise ratio (CNR) was measured between the tibia and adjacent soft tissue. The IQ of the phantom images was assessed by three radiologists and a reporting radiographer. Four IQ criteria were defined each with a scale of 1-3, giving a maximum score of 12. Finally, a service audit of clinical images at the default and optimum beam qualities was undertaken. RESULTS: The measured CNR for the 40 kVp/no Cu image was 12.0 compared with 7.6 for the default mode (55 0.1 mm Cu). An improvement in the clinical IQ scores was also apparent at this lower beam quality. CONCLUSION: Lowering tube potential and removing filtration improved the clinical IQ of paediatric ankle radiographs in this age range. ADVANCES IN KNOWLEDGE: There are currently no UK guidelines on exposure protocols for paediatric imaging using direct digital radiography. A lower beam quality will produce better IQ with no additional dose penalty for infant extremity imaging.

Fostering innovation and collaboration.

The Health Technologies Knowledge Transfer Network is taking active steps to foster innovation and collaboration. Users of its internet portal can access a range of valuable tools to aid this process, including free virtual meeting facilities.

Physical and biological properties of a novel siloxane adhesive for soft tissue applications.

The aim of this study was to investigate the adhesive properties of an in-house aminopropyltrimethoxysilane-methylenebisacrylamide (APTMS-MBA) siloxane system and compare them with a commercially available adhesive, n-butyl cyanoacrylate (nBCA). The ability of the material to perform as a soft tissue adhesive was established by measuring the physical (bond strength, curing time) and biological (cytotoxicity) properties of the adhesives on cartilage. Complementary physical techniques, X-ray photoelectron spectroscopy, Raman and infrared imaging, enabled the mode of action of the adhesive to the cartilage surface to be determined. Adhesion strength to cartilage was measured using a simple butt joint test after storage in phosphate-buffered saline solution at 37 degrees C for periods up to 1 month. The adhesives were also characterised using two in vitro biological techniques. A live/dead stain assay enabled a measure of the viability of chondrocytes attached to the two adhesives to be made. A water-soluble tetrazolium assay was carried out using two different cell types, human dermal fibroblasts and ovine meniscal chondrocytes, in order to measure material cytotoxicity as a function of both supernatant concentration and time. IR imaging of the surface of cartilage treated with APTMS-MBA siloxane adhesive indicated that the adhesive penetrated the tissue surface marginally compared to nBCA which showed a greater depth of penetration. The curing time and adhesion strength values for APTMS-MBA siloxane and nBCA adhesives were measured to be 60 s/0.23 MPa and 38 min/0.62 MPa, respectively. These materials were found to be significantly stronger than either commercially available fibrin (0.02 MPa) or gelatin resorcinol formaldehyde (GRF) adhesives (0.1 MPa) (P < 0.01). Cell culture experiments revealed that APTMS-MBA siloxane adhesive induced 2% cell death compared to 95% for the nBCA adhesive, which extended to a depth of approximately 100-150 microm into the cartilage surface. The WST-1 assay demonstrated that APTMS-MBA siloxane was significantly less cytotoxic than nBCA adhesive as an undiluted conditioned supernatant (P < 0.001). These results suggest that the APTMS-MBA siloxane may be a useful adhesive for medical applications.

Cements from nanocrystalline hydroxyapatite.

Calcium phosphate cements are used as bone substitute materials because they may be moulded to fill a void or defect in bone and are osteoconductive. Although apatite cements are stronger than brushite cements, they are potentially less resorbable in vivo. Brushite cements are three-component systems whereby phosphate ions and water react with a soluble calcium phosphate to form brushite (CaHPO4 x 2H2O). Previously reported brushite cement formulations set following the mixture of a calcium phosphate, such as beta-tricalcium phosphate (beta-TCP), with an acidic component such as H3PO4 or monocalcium phosphate monohydrate (MCPM). Due to its low solubility, hydroxyapatite (HA) is yet to be reported as a reactive component in calcium phosphate cement systems. Here we report a new cement system setting to form a matrix consisting predominantly of brushite following the mixture of phosphoric acid with nanocrystalline HA. As a result of the relative ease with which ionic substitutions may be made in apatite this route may offer a novel way to control cement composition or setting characteristics. Since kinetic solubility is dependent on particle size and precipitation temperature is known to affect precipitated HA crystal size, the phase composition and mechanical properties of cements made from HA precipitated at temperatures between 4 and 60 degrees C were investigated.

Electrolyte pH changes in Human Milk.

Milk samples from 100 lactating mothers in the 10 days following delivery have been analyzed for pH, sodium, and potassium. The sodium concentration was high in the first 5 days, mean 21 +/- 5 mmol/liter, but fell to a mean 15 mmol/liter by the end of the first week and 12 mmol/liter by the 10th day. A similar downward trend was shown for potassium with an initial mean concentration of 18.5 mmol/liter falling to 15 mmol/liter by the 10th day. The pH fluctuated widely from day to day through a range of 6.75-7.42 with a mean pH 7.09. Considerable variations were shown in individuals from day to day, and from the beginning to the end of feeds (Table 1). The relatively high sodium concentration in the first few days may be an important defense mechanism against dehydration and hyponatremia during a period of relative thirst and starvation. The variation in the pH and electrolyte content of human milk may be expected to have some influence on the acid-base and electrolyte status of the infant.

Metabolic acidosis and infant feeding.

Most cows' milk based formulae for infant feeding present a greater acid load to the infant than breast milk. To determine the effect of this difference the acid base state of 180 healthy term infants was measured on the sixth day of life and related to the type of feed. Those infants fed on cows' milk formula (SMA) had a mean pH of 7-34 +/- 0-05 and a base deficit of 8-8 +/- 3-1, while those fed on breast milk had a mean pH of 7-38 +/- 0-05 and a base deficit of 5-6 +/- 3-1. The difference between the two groups of infants was significant for both these measurements. Metabolic acidosis was defined as a base deficit greater than 10 mmol/l. Seventy-four per cent of the 34 infants who were acidotic at six days were bottle-fed. There was a significant correlation between the pH of the feed and the degree of acidosis in the infant as measured by the base deficit. The findings suggest that when breast milk is not available a pH-adjusted milk formula would be desirable for preventing and treating neonatal metabolic acidosis.