V Fanti | PubMed Health

PubMed2005

A Simulator for X-ray images.

A simulator for X-ray images is presented based on a virtual X-ray source and a virtual human body obtained from tomographic slices. In the simulator it is possible to modify the tube potential, the anodic current, the exposure time, the filtration and some geometric parameters such as source-skin distance, orientation and field size. The virtual body consists of a three-dimensional voxel matrix in which CT numbers for each point of the body are stored. The interactions of X rays passing through the body are evaluated using the pencil beam technique. The image is obtained by computing the dose absorbed by the detector and converting it into optical density using a proper response function. The image spatial resolution is limited by the voxel size. The influence of each parameter on the image quality can be observed interactively. The dose absorbed in each point of the body is an important parameter obtained as output of the simulator.

Computer Simulation↗

PubMed2000

Apical microleakage of radiolabeled lysozyme over time in three techniques of root canal obturation.

The three methods of obturation assessed in this study were lateral condensation (80 teeth), Thermafil (40 teeth), and McSpadden (40 teeth). All teeth were prepared to the master apical file 30 and widened coronally by Gates Glidden burs before being randomly assigned to experimental groups to be filled by each technique; they were then sealed with nail polish, except for the apical 1 mm. Quantitative evaluation of apical microleakage for each technique was obtained after periods of 1 day, 7 days, 14 days, and 28 days of immersion in a lysozyme solution labeled with radioactive iodine by preparing horizontal sections of the teeth and measuring the level of radioactivity in each section using a gamma counter. Initial (1-day) leakage was least in the Thermafil group and was significantly different from the other techniques. Leakage was greatest in the laterally condensed samples. By the end of the study (28th day) values for lateral condensation were lowest, but were significantly different only for the McSpadden group. For all techniques leakage was most significant in the first 3 mm from the apex and was very low below this level so that all methods can be considered as giving a hermetic seal below 3 mm.

Analysis of Variance↗