Imaging of moving fiducial markers during radiotherapy using a fast, efficient active pixel sensor based EPID.

Purpose: The purpose of this work was to investigate the use of an experimental complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) for tracking of moving fiducial markers during radiotherapy.

Methods: The APS has an active area of 5.4 × 5.

Electrostatic potential maps of damaged DNA studied by image analysis tools. 8-Oxoguanine and abasic site lesions.

Changes of electrostatic potential around the DNA molecule resulting from chemical modifications of nucleotides may play a role in enzymatic recognition of damaged sites. The electrostatic potential around the DNA fragments containing either the intact guanine-cytosine pair or 8-oxoguanine-cytosine or the guanine-abasic site was projected on a cylindrical surface around the double helix. The 2D maps of EP of intact and damaged DNA fragments were compared using image analysis methods.

Cylindrical projection of electrostatic potential and image analysis tools for damaged DNA: the substitution of thymine with thymine glycol.

Changes of electrostatic potential around the DNA molecule resulting from chemical modifications of nucleotides may play a role in enzymatic recognition of damaged sites. Effects of chemical modifications of nucleotides on the structure of DNA have been characterized through electronic structure computations. Quantum mechanical structural optimizations of fragments of five pairs of nucleotides with thymine or thymine glycol were performed at the density functional level of theory with a B3LYP exchange-correlation functional and 6-31G(d,p) basis sets.