We have sequenced five distinct mitochondrial genomes in maize: two fertile cytotypes (NA and the previously reported NB) and three cytoplasmic-male-sterile cytotypes (CMS-C, CMS-S, and CMS-T). Their genome sizes range from 535,825 bp in CMS-T to 739,719 bp in CMS-C. Large duplications (0.5-120 kb) account for most of the size increases. Plastid DNA accounts for 2.3-4.6% of each mitochondrial genome. The genomes share a minimum set of 51 genes for 33 conserved proteins, three ribosomal RNAs, and 15 transfer RNAs. Numbers of duplicate genes and plastid-derived tRNAs vary among cytotypes. A high level of sequence conservation exists both within and outside of genes (1.65-7.04 substitutions/10 kb in pairwise comparisons). However, sequence losses and gains are common: integrated plastid and plasmid sequences, as well as noncoding ''native'' mitochondrial sequences, can be lost with no phenotypic consequence. The organization of the different maize mitochondrial genomes varies dramatically; even between the two fertile cytotypes, there are 16 rearrangements. Comparing the finished shotgun sequences of multiple mitochondrial genomes from the same species suggests which genes and open reading frames are potentially functional, including which chimeric ORFs are candidate genes for cytoplasmic male sterility. This method identified the known CMS-associated ORFs in CMS-S and CMS-T, but not in CMS-C.

Specially designed electronic event reporting systems in a radiotherapy setting can provide valuable data for process and patient safety improvement and are more effective reporting mechanisms than paper-based systems. Additional work is needed to develop methods that can more effectively utilize reported data for process improvement, including the development of standardized event taxonomy and a classification system for RT.

Purpose: Target tracking using dynamic multileaf collimator ͑DMLC͒ is a promising approach for intrafraction motion management in radiation therapy. The purpose of this work is to develop a DMLC tracking algorithm capable of delivering volumetric-modulated arc therapy ͑VMAT͒ to the targets that experience two-dimensional ͑2D͒ rigid motion in the beam's eye view. Methods: The problem of VMAT delivery to moving targets is formulated as a control problem with constraints. The relationships between gantry speed, gantry acceleration, MLC leaf-velocity, dose rate, and target motion are derived. An iterative search algorithm is developed to find numerical solutions for efficient delivery of a specific VMAT plan to the moving target using 2D DMLC tracking. The delivery of five VMAT lung plans is simulated. The planned and delivered fluence maps in the target-reference frame are calculated and compared. Results: The simulation demonstrates that the 2D tracking algorithm is capable of delivering the VMAT plan to a moving target fast and accurately without violating the machine constraints and the integrity of the treatment plan. The average delivery time is only 29 s longer than that of notracking delivery, 101 versus 72 s, respectively. The fluence maps are normalized to 200 MU and the average root-mean-square error between the desired and the delivered fluence is 2.1 MU, compared to 14.8 MU for no-tracking and 3.6 MU for one-dimensional tracking. Conclusions: A locally optimal MLC tracking algorithm for VMAT delivery is proposed, aiming at shortest delivery time while maintaining treatment plan invariant. The inconsequential increase of treatment time due to DMLC tracking is clinically desirable, which makes VMAT with DMLC tracking attractive in treating moving tumors.

The investigations derive and prove time optimal VMAT deliveries. The relationships between delivery parameters are determined. The optimal alternative delivery strategies are discussed.

The purpose of this study was to independently verify the transferred delivery sinogram between two dosimetrically matched helical tomotherapy machines with the goal of eliminating redundant quality assurance (QA) measurements on the second machine. The equivalence of the two machines was evaluated based on both geometric and dosimetric beam characteristics, including measuring open field per cent depth doses (PDD), longitudinal and transverse profiles and helical delivery of clinical patient treatment plans measured in phantoms. QA of 56 patient plans was studied. The delivery sinogram on the secondary machine was computed by accounting for the differences in the MLC characteristics of the two machines. Computed sinograms were compared against the transferred sinograms by tomotherapy's data management system for the same 56 patient plans. The PDD, transverse and longitudinal dose profiles agreed within ±1% between the two machines. Ionization chamber and planar dose measurements with the Iba MatriXX device on both machines for the 56 patients were found to be within ±3% of the doses computed by the tomotherapy treatment planning system. For all 56 patients, the differences between computed sinograms and DMS-converted sinograms were within ±2%. The matched tomotherapy machines had similar beam characteristics. The sinogram-based QA was validated using point and planar dose measurements and found to be acceptable for clinical use.