Browsing by Author "Mehmood, Shahid"

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    Dosimetric effect of limited aperture multileaf collimator on VMAT plan quality: A study of prostate and head-and-neck cancers
    (Reports of Practical Oncology and Radiotherapy, 2018-02-16) Murtaza, Ghulam; Mehmood, Shahid; Rasul, Shahid; Murtaza, Imran; Ehsan ullah Khan
    The aim of study was to evaluate the dosimetric effect of collimator-rotation on VMAT plan quality, when using limited aperture multileaf collimator of Elekta Beam Modulator™ providing a maximum aperture of 21 cm × 16 cm. Background The increased use of VMAT technique to deliver IMRT from conventional to very specialized treatments present a challenge in plan optimization. In this study VMAT plans were optimized for prostate and head and neck cancers using Elekta Beam-ModulatorTM, whereas previous studies were reported for conventional Linac aperture. Materials and methods VMAT plans for nine of each prostate and head-and-neck cancer patients were produced using the 6 MV photon beam for Elekta-SynergyS® Linac using Pinnacle3 treatment planning system. Single arc, dual arc and two combined independent-single arcs were optimized for collimator angles (C) 0°, 90° and 0°–90° (0°–90°; i.e. the first-arc was assigned C0° and second-arc was assigned C90°). A treatment plan comparison was performed among C0°, C90° and C(0°–90°) for single-arc dual-arc and two independent-single-arcs VMAT techniques to evaluate the influence of extreme collimator rotations (C0° and 90°) on VMAT plan quality. Plan evaluation criteria included the target coverage, conformity index, homogeneity index and doses to organs at risk. A ‘two-sided student t-test’ (p ≤ 0.05) was used to determine if there was a significant difference in dose volume indices of plans. Results For both prostate and head-and-neck, plan quality at collimator angles C0° and C(0°–90°) was clinically acceptable for all VMAT-techniques, except SA for head-and-neck. Poorer target coverage, higher normal tissue doses and significant p-values were observed for collimator angle 90° when compared with C0° and C(0°–90°). Conclusions A collimator rotation of 0° provided significantly better target coverage and sparing of organs-at-risk than a collimator rotation of 90° for all VMAT techniques.
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    Prediction of Protein Solubility in Escherichia coli and Experimental Verification
    (University of Management & Technology, 2017) Mehmood, Shahid
    Soluble protein in proper concentration is very important for different experimental studies. Solubility of protein can be estimated by the sequence of amino acids in protein. The solubility of protein is important for biophysical and structural development. To achieve the soluble protein in high concentration is a major challenge. The protein which are heterologous expressed are often insoluble and their solubilization is highly trial and error process with low success rate. Although very highly overexpression in inclusion body is some time desirable which result in clean protein. A new method is develop which will predict the solubility of protein on overexpression in E.coli. This method use four classifier named as Multilayer Perceptron, Decision Tree, Random Forest, Bayes Classifier. Theses classifier were trained for the prediction of recombinant protein solubility. Many features are used by this method such as canonical variable (CV),Surrounding hydrophobicity, Solubility index composition, Intrinsic aggregation propensity, Intrinsic Z-scores for aggregation, = tripeptide score, AI = aliphatic index, II= instability index, Fn= frequency of occurrence of Asn, Ft = frequency of occurrence of Thr, Fy= frequency of occurrence of Tyr. It is very simple and easy method for the prediction of recombinant protein solubility. To evaluate the validity of this method test is performed. For this purpose dataset consist of 1500 proteins, out of which 1000 are soluble and 500 are insoluble. Each classifier was trained for the prediction of 450 protein sequences. This method will predict the protein solubility with greater accuracy of about 95.9%. The accuracy of this method is also compared with the previous work or methods. Results shows that this method has more accuracy and precision then other previous works.