Evaluation and optimization of the new EBT2 radiochromic film dosimetry system for patient dose verification in radiotherapy

A new radiochromic film, the yellow Gafchromic EBT2, has been marketed as a drop-in replacement for the discontinued blue EBT film. In order to verify the manufacturer's claims prior to clinical use, EBT2 was characterized in transmission, and the less commonly used, reflection modes with an Epson Expression 10000XL A3 flatbed scanner. The red channel was confirmed to provide the greatest sensitivity and was used for all measurements. The post-irradiation darkening of the film was investigated, and the relative response was found to be dose dependent with higher doses stabilizing earlier than lower doses. After 13 h all dose levels had stabilized to within 1% of their value at 24 h. Uniformity of irradiated EBT2 films was within 0.8% and 1.2% (2SD of signal), in reflection and transmission modes, respectively. The light scattering effect, arising from the structure and thickness of EBT2, was found to give rise to an apparent scanner non-uniformity of up to 5.5% in signal. In reflection mode, differences of up to 1.2% were found between the signal obtained from a small film fragment (5 x 5 cm(2)) and the signal obtained from the same fragment bordered by extra film. Further work is needed to determine the origin of this effect, as there will be implications for reflection dosimetry of intensity modulated fields; reflection mode cannot yet be regarded as a viable alternative to transmission mode. Our results suggest that EBT2 film is a valid alternative, rather than a direct replacement for EBT film.

Scattering of the fundamental torsional mode at an axial crack in a pipe

A quantitative study of the interaction of the T(0,1) torsional mode with an axial defect in a pipe is presented. The results are obtained from finite element simulations and experiments. The influence of the crack axial extent, depth, excitation frequency, and pipe circumference on the scattering is examined. It is found that the reflection from a defect consists of a series of the wave pulses with gradually decaying amplitudes. Such behavior is caused by the shear waves diffracting from the crack and then repeatedly interacting with the crack due to circumferential propagation. Time-domain reflection coefficient analysis demonstrates that the trend of the reflection strength for different crack lengths, pipe diameters, and frequencies from a through-thickness crack satisfies a simple normalization. The results show that the reflection coefficient initially increases with the crack length at all frequencies but finally reaches an oscillating regime. Also, at a given frequency and crack length the reflection decreases with the increase in pipe circumference. An additional scattering study of the shear wave SH(0) mode at a part-thickness notch in a plate shows that the reflection coefficient, when plotted against depth of the notch, increases with both frequency and notch depth.

Stem cell through present and future

Stem cell transplantation (SCT) has the potential to transform the lives of children with a wide variety of genetic diseases, ranging from inherent defects of hemopoietic cell production or function through to metabolic diseases mostly affecting solid organs. For these children life expectancy or quality of life would otherwise be very poor. It ranks as one of the most remarkable therapeutic advances of the past 40 years. Despite rapid technological improvements, however, there are still many short term risks and potential long term toxicities. Consequently, the rapid emergence of alternative therapies (including new drugs, enzyme and gene therapies), necessitate constant re-evaluation of the risk/benefit ratio for each disease and hence the appropriateness of SCT. This review describes the major aspects of the transplant process, indications for transplantation, outcome statistics, and areas where alternative therapies are becoming available. SCT remains a highly experimental therapy. Due to the relatively short history of the discipline no data exists on truly long term follow up. This is important as some organs benefit relatively poorly or problems may emerge which were never apparent as part of the untreated disease. The speed of technological change makes randomised trials on these diseases, which are individually quite rare, almost impossible to perform.

Five-day storage of platelet concentrates. I. In-vitro studies

Platelet concentrates have been prepared in standard PVC (PL-146) packs and polyolefin (PL-732) packs. Comparison of pH and hypotonic stress of the platelet concentrates has shown that significantly improved values are obtained after storage of the concentrates at 22 C in PL-732 packs for 5 days than after storage for 3 days in PL-146 packs. There was no significant difference under conditions of the test between vertical and horizontal agitation of the concentrates. Since both pH and hypotonic stress recovery have shown a relationship to post-transfusion recovery and viability, evidence is presented to support the 5-day storage period of concentrates prepared and stored in PL-732 packs.

Treatment of Paget's disease of bone: a survey of clinical practice in Australia

Consensus guidelines for the treatment of Paget's disease of bone have been published, but it is not known how closely these reflect clinical practice. We conducted a multi-centre, stratified, retrospective review of case notes of 531 subjects treated for Paget's disease of bone between 2000 and 2005 in 29 Australian centres. The subjects received 1072 courses of bisphosphonate treatment (pamidronate 363, alendronate 324, risedronate 208, tiludronate 103, zoledronic acid 69, and etidronate 5). The most recent treatment received was oral therapy in 57% of patients (alendronate 29%, risedronate 24%, and tiludronate 4%) and intravenous in 43% (pamidronate 33%, and zoledronic acid 10%). For oral bisphosphonates, the percentages of courses which were at the recommended dosage and duration were: alendronate 33%, risedronate 60% and tiludronate 29%. Pamidronate was administered in a wide range of dosing schedules, most commonly 60 mg every 3 months (18%), 6 months (17%) or annually (12%), whereas zoledronic acid was mainly given as a 4 mg infusion (98%) as a single dose (52%) or annually (19%). Most clinicians reported taking into account symptoms, plasma alkaline phosphatase activity and anatomical location of disease in determining the need for treatment. Patient preference, intolerance of oral therapy and compliance were ranked highest in determining the choice between oral and intravenous therapy. We conclude that oral and intravenous bisphosphonate dosing regimens are both commonly used to treat Paget's disease of bone in Australia. Only a minority of courses of oral bisphosphonate treatment are at the recommended dosage and duration, and there is a lack of consensus on regimens for intravenous treatment.

The influence of antisense oligonucleotide length on dystrophin exon skipping

Antisense oligonucleotides (AOs) can be used to redirect dystrophin pre-messenger RNA (mRNA) processing, to remove selected exons from the mature dystrophin mRNA, to overcome nonsense mutations, and/or restore the reading frame. Redundancy within the dystrophin protein allows some domains to be removed without seriously compromising function. One of the challenges for splicing blockade is to design AOs that efficiently remove targeted exons across the dystrophin pre-mRNA. AOs are initially designed to anneal to the more obvious motifs implicated in the splicing process, such as acceptor or donor splice sites and in silico predicted exonic splicing enhancers. The AOs are evaluated for their ability to induce targeted exon skipping after transfection into cultured myoblasts. Although no single motif has been implicated in the consistent induction of exon skipping, the length of the AO has emerged as an important parameter in designing compounds that redirect dystrophin pre-mRNA processing. We present data from in vitro studies in murine and human cells showing that appropriately designed AOs of 25-31 nucleotides are generally more effective at inducing exon skipping than shorter counterparts. However, there appears to be an upper limit in optimal length, which may have to be established on a case-by-case basis.

Cell-penetrating peptide-morpholino conjugates alter pre-mRNA splicing of DMD (Duchenne muscular dystrophy) and inhibit murine coronavirus replication in vivo

The cellular uptake of PMOs (phosphorodiamidate morpholino oligomers) can be enhanced by their conjugation to arginine-rich CPPs (cell-penetrating peptides). Here, we discuss our recent findings regarding (R-Ahx-R)(4)AhxB (Ahx is 6-aminohexanoic acid and B is beta-alanine) CPP-PMO conjugates in DMD (Duchenne muscular dystrophy) and murine coronavirus research. An (R-Ahx-R)(4)AhxB-PMO conjugate was the most effective compound in inducing the correction of mutant dystrophin transcripts in myoblasts derived from a canine model of DMD. Similarly, normal levels of dystrophin expression were restored in the diaphragms of mdx mice, with treatment starting at the neonatal stage, and protein was still detecTable 22 weeks after the last dose of an (R-Ahx-R)(4)AhxB-PMO conjugate. Effects of length, linkage and carbohydrate modification of this CPP on the delivery of a PMO were investigated in a coronavirus mouse model. An (R-Ahx-R)(4)AhxB-PMO conjugate effectively inhibited viral replication, in comparison with other peptides conjugated to the same PMO. Shortening the CPP length, modifying it with a mannosylated serine moiety or replacing it with the R(9)F(2) CPP significantly decreased the efficacy of the resulting PPMO (CPP-PMO conjugate). We attribute the success of this CPP to its stability in serum and its capacity to transport PMO to RNA targets in a manner superior to that of poly-arginine CPPs.