Surface dosimetry for breast radiotherapy in the presence of immobilization cast material

Curative breast radiotherapy typically leaves patients with varying degrees of cosmetic damage. One problem interfering with cosmetically acceptable breast radiotherapy is the external contour for large pendulous breasts which often results in high doses to skin folds. Thermoplastic casts are often employed to secure the breasts to maintain setup reproducibility and limit the presence of skin folds. This paper aims to determine changes in surface dose that can be attributed to the use of thermoplastic immobilization casts. Skin dose for a clinical hybrid conformal/IMRT breast plan was measured using radiochromic film and MOSFET detectors at a range ofwater equivalent depths representative of the different skin layers. The radiochromic film was used as an integrating dosimeter, while the MOSFETs were used for real-time dosimetry to isolate the contribution of skin dose from individual IMRT segments. Strips of film were placed at various locations on the breast and the MOSFETs were used to measure skin dose at 16 positions spaced along the film strips for comparison of data. The results showed an increase in skin dose in the presence of the immobilization cast of up to 45.7% and 62.3% of the skin dose without the immobilization cast present as measured with Gafchromic EBT film and MOSFETs, respectively. The increase in skin dose due to the immobilization cast varied with the angle of beam incidence and was greatest when the beam was normally incident on the phantom. The increase in surface dose with the immobilization cast was greater under entrance dose conditions compared to exit dose conditions

New Structural and Functional Contexts of the Dx[DN]xDG Linear Motif: Insights into Evolution of Calcium-Binding Proteins

Binding of calcium ions (Ca2+) to proteins can have profound effects on their structure and function. Common roles of calcium binding include structure stabilization and regulation of activity. It is known that diverse families – EF-hands being one of at least twelve – use a Dx[DN]xDG linear motif to bind calcium in near-identical fashion. Here, four novel structural contexts for the motif are described. Existing experimental data for one of them, a thermophilic archaeal subtilisin, demonstrate for the first time a role for Dx[DN]xDG-bound calcium in protein folding. An integrin-like embedding of the motif in the blade of a β-propeller fold – here named the calcium blade – is discovered in structures of bacterial and fungal proteins. Furthermore, sensitive database searches suggest a common origin for the calcium blade in β-propeller structures of different sizes and a pan-kingdom distribution of these proteins. Factors favouring the multiple convergent evolution of the motif appear to include its general Asp-richness, the regular spacing of the Asp residues and the fact that change of Asp into Gly and vice versa can occur though a single nucleotide change. Among the known structural contexts for the Dx[DN]xDG motif, only the calcium blade and the EF-hand are currently found intracellularly in large numbers, perhaps because the higher extracellular concentration of Ca2+ allows for easier fixing of newly evolved motifs that have acquired useful functions. The analysis presented here will inform ongoing efforts toward prediction of similar calcium-binding motifs from sequence information alone

Clinical role of flow cytometry in redefining bone marrow involvement in diffuse large B-cell lymphoma (DLBCL) - a new perspective

Aims: The clinical role of flow cytometry in staging bone marrow in diffuse large B-cell lymphoma (DLBCL), especially its impact on outcome, remains uncertain. The aim was to determine the contribution of flow cytometry to conventional staging, and to study the impact of this revised staging on survival. Methods and results: One hundred and thirteen cases of DLBCL diagnosed at The Canberra Hospital from 1996 to 2005 were identified. Blinded analysis of bone marrow (BM) morphology and flow cytometric data showed involvement on morphology (M) in 25 (22.1%) cases, on flow cytometry (F) in 21 (18.6%) cases and overall (M + F) in 32 cases (28.3%); discordance was noted in 16 cases (16.1%). Cases with and without marrow involvement on conventional staging alone (M) had no significant difference in survival (P = NS). However, when BM involvement was defined as positivity on morphology and/or flow cytometry (M + F), the median survival of patients with involvement was significantly worse than patients without involvement (P = 0.026). Conclusions: Flow cytometry-positive cases should be included with those positive on morphology in a summative model to define BM involvement in DLBCL, as it may have a potential impact on predicting outcome

Electrical Impedance Tomography for high speed chest imaging

Electrical Impedance Tomography (EIT) is a method for imaging the internal conductivity distribution of a cross section of human body using known injected currents and measured potentials on the surface. The problem of recovering the internal conductivity from this data is extremely ill-conditioned and, by contrast to many other medical imaging techniques, nonlinear. Inevitably EIT images will be low in spatial resolution but the technique promises high temporal resolution, continuous monitoring, relatively low cost and the possibility that soft tissue changes may be imaged which are invisible to other imaging techniques

Chest Impedance Imaging Using Trigonometric Current Patterns

This paper reports the results from the application of the 32 channel Oxford Brookes Adaptve Current Tomograph, OXBACT-III to the chest of a human volunteer. A frame rate of 10 per second was achieved using trigonometric drive currents

Measurement of serum antigen concentration by ultrasound-enhanced immunoassay and correlation with clinical outcome in meningococcal disease

The distribution of Neisseria meningitidis serogroup B and C polysaccharide antigen in blood and the prognostic significance of antigen concentration was examined by ultrasound-enhanced immunoagglutination of coated microparticles. Specimens (169 sera/plasma from 145 patients with confirmed meningococcal disease) were tested retrospectively. The ultrasonic immunoassay detected serum antigen in 136 samples from 112 patients. Titration of antigen-positive specimens allowed estimation of blood antigen concentration. The modal blood antigen titre was 1/16, corresponding to an estimated polysaccharide concentration of 0.85 microg/ml. The lowest mean blood antigen concentration found ultrasonically was 0.05 microg/ml; compared to the 1.98 microg/ml found by conventional latex agglutination, this represents an approximately 30-fold improvement in sensitivity. Three grades of outcome were correlated with the presenting antigen titre in 83 patients: (i) or =2 weeks hospitalisation and (iii) mortality. High polysaccharide concentrations correlated with mortality. Nine of 15 patients with a serum antigen titre of 1/64 or greater (> or =3.4 microg/ml polysaccharide) died, whereas no patient with titres equal to or less than 1/4 (< or = 0.21 microg/ml) died, including those patients in whom antigen was undetectable by ultrasonic immunoassay. Increasing antigen concentration significantly correlated with severity of outcome (P<0.001). Ultrasound-enhanced agglutination provides a rapid prognostic indicator by sensitive measurement of serum antigen level