Verifying 4D gated radiotherapy using time-integrated electronic portal imaging: a phantom and clinical study

<p>Abstract</p> <p>Background</p> <p>Respiration-gated radiotherapy (RGRT) can decrease treatment toxicity by allowing for smaller treatment volumes for mobile tumors. RGRT is commonly performed using external surrogates of tumor motion. We describe the use of time-integrated electronic portal imaging (TI-EPI) to verify the position of internal structures during RGRT delivery</p> <p>Methods</p> <p>TI-EPI portals were generated by continuously collecting exit dose data (aSi500 EPID, Portal vision, Varian Medical Systems) when a respiratory motion phantom was irradiated during expiration, inspiration and free breathing phases. RGRT was delivered using the Varian RPM system, and grey value profile plots over a fixed trajectory were used to study object positions. Time-related positional information was derived by subtracting grey values from TI-EPI portals sharing the pixel matrix. TI-EPI portals were also collected in 2 patients undergoing RPM-triggered RGRT for a lung and hepatic tumor (with fiducial markers), and corresponding planning 4-dimensional CT (4DCT) scans were analyzed for motion amplitude.</p> <p>Results</p> <p>Integral grey values of phantom TI-EPI portals correlated well with mean object position in all respiratory phases. Cranio-caudal motion of internal structures ranged from 17.5–20.0 mm on planning 4DCT scans. TI-EPI of bronchial images reproduced with a mean value of 5.3 mm (1 SD 3.0 mm) located cranial to planned position. Mean hepatic fiducial markers reproduced with 3.2 mm (SD 2.2 mm) caudal to planned position. After bony alignment to exclude set-up errors, mean displacement in the two structures was 2.8 mm and 1.4 mm, respectively, and corresponding reproducibility in anatomy improved to 1.6 mm (1 SD).</p> <p>Conclusion</p> <p>TI-EPI appears to be a promising method for verifying delivery of RGRT. The RPM system was a good indirect surrogate of internal anatomy, but use of TI-EPI allowed for a direct link between anatomy and breathing patterns.</p

Production and properties of tragacanthin-conjugated lysozyme as a new multifunctional biopolymer

In this communication we describe preparation and characterization of an enzyme-biopolymer conjugate composed of water-soluble part of gum tragacanth and chicken egg white lysozyme (LZM) under mild Maillard reaction conditions. SDS-PAGE together with FT-IR spectroscopy revealed that Maillard reactions occurred between LZM and tragacanthin (TRG). Under optimum conditions (pH = 8.5, 60 degrees C, RH = 79%, 8 days), approximately 2 TRG molecules were attached to one LZM molecule. DSC analysis showed that conjugation with TRG increased denaturation temperature by 6.35 degrees C. The resulting conjugates were characterized using scanning electron microscopy. The modified enzyme activity retained 77% of the original enzymatic activity after 8 days. TRG-conjugated LZM exhibited improved solubility and emulsion properties as compared with the native LZM. In addition, a significant increase in foam capacity and stability of LZM-TRG conjugate was detected. Conjugate with TRG significantly improved the inhibitory effect of LZM on the growth of Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhi in a dose dependent manner such that at 4000 mu g/ml, LZM-TRG conjugate inhibited S. aureus, Bacillus cereus, Escherichia coli and Salmonella typhi by 90%, 80%, 50% and 40%, respectively. Taken together these results suggest that the functional properties and antimicrobial activities of LZM can be improved by conjugation with TRG. The conjugation might expand the applications of LZM as a multifunctional ingredient in food and pharmaceutical industries