Since the release of the Cyberknife Multileaf Collimator (CK-MLC), it has been a constant concern on the realistic dose differences computed with its early-available Finite Size Pencil Beam algorithm (FSPB) from those computed by using industry well-accepted algorithms such as the Monte Carlo (MC) dose algorithm. In this study dose disparities between FSPB and MC dose calculation algorithms for selected CK-MLC treatment plans were quantified. The dosimetry for planning target volume (PTV) and major organs at risks (OAR) was compared by calculating normalized percentage deviations (Ndev) between the two algorithms. It is found that the FSPB algorithm overestimates D95 of PTV when compared with the MC algorithm by averaging 24.0% in detached lung cases, and 15.0% in non-detached lung cases which is attributed to the absence of heterogeneity correction in the FSPB algorithm. Average dose differences are 0.3% in intracranial and 0.9% in pancreas cases. Ndev for the D95 of PTV range from 8.8% to 14.1% for the CK-MLC lung treatment plans with small field (SF ≤ 2x2cm2). Ndev is ranged from 0.5-7.0% for OARs. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

No description available.

The goal of conformal radiation techniques is to improve local tumour control through dose escalation to target volumes while at the same time sparing surrounding healthy tissue. Respiratory motion is known to be the largest intra-fractional organ motion and the most significant source of uncertainty in treatment planning for chest lesions. A method to account for the effects of respiratory motion is to use four-dimensional radiotherapy. While analytical models are useful, it is essential that the motion problem in radiotherapy is addressed by both modeling as well as experimentally studies so that different obstacles can be overcome before clinical implementation of a motion compensation method. Validation of techniques aimed at measuring and minimizing the effects of respiratory motion require a realistic dynamic deformable phantom for use as a gold standard. In this work we present the design, construction, performance and deformable image registration of a novel breathing, tissue equivalent phantom with a deformable lung that can reproducibly emulate 3D non-isotropic lung deformations according to any real lung-like breathing pattern. The phantom consists of a Lucite cylinder filled with water containing a latex balloon stuffed with dampened natural sponges. The balloon is attached to a piston that mimics the human diaphragm. Nylon wires and Lucite beads, emulating vascular and bronchial bifurcations, were glued at various locations, uniformly throughout the sponges. The phantom is capable of simulating programmed irregular breathing patterns with varying periods and amplitudes. A deformable, tissue equivalent tumour, suitable for holding radiochromic film for dose measurements was embedded in the sponge. Experiments for 3D motion assessment, motion reproducibility as well as deformable image registration and validation are presented using the deformable phantom.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2008/05/09). Includes bibliographical references.