Influence Of CT Simulator Scan Parameters On TPS Image Reconstruction Accuracy

Background: Three-dimensional conformal radiation therapy and intensity-modulated radiation therapy technology, can make the high dose area distribution and drew the outline of the tumor target to establish shape in 3 D space to achieve very good conformal, is relying on CT simulation positioning machine with its unique advantage throughout the whole process of radiotherapy. CT simulation positioning(CT- Sim) technology has been the tumor treatment units are widely used in the three dimensional conformal and intensity modulated radiation therapy.Objective: Using commercial image quality control body model, measuring two manufacturers and models of TPS system in different CT scan parameters when the geometry precision of image reconstruction, for the department to establish different TPS system specification and plan of the CT scan design to provide the most powerful basis. Method to choose a CT machine 6 groups of different scan parameters on the built-in known volume, structure of different shape, density and other relative electron density range scanning module. Two TPS workstation in different manufacturers test for image reconstruction. Comparing the system reconstruction quality, geometric accuracy and CT value and relative change of electron density. Results(1) in the TPS system reconstruction volume of length, width and height and length, width and height of die bodies actual volume deviation is very small, CT- Sim simulation positioning technology standard; Measured by two different sets of TPS workstation system image reconstruction even there are different degrees of deviation;(2) on the system of image reconstruction has distinct effect on the volume: scan die body volume less than(< 5 cc) reconstruction error is larger, the volume of the clinical commonly us ed(5 cc- 125 cc) within the scope of the results are basically in the reconstruction of the TPS system deviation less than 6%.(3) CT scan for reconstruction with a thick layer of volume is more significant than other factors: the influence of scanning l ayer thickness, the greater the image reconstruction error, the greater the volume of each system.(4) scanning the reconstruction of the pitch value of 1.0 volume precision is betterThan the other pitch; With the increase of pitch, volume error and the error of the upper and lower diameter also increases.(5) scanning current voltage obviously on the CT values, two different sets of TPS system calculation value and CT machine calibration curve is relatively consistent.(6) the TPS system, target zone affected by the scanning parameters. Conclusion the experimental results show that the tumor radiation therapy unit at all levels is very necessary to the clinical use of each CT- Sim workstation system and computed tomography(CT) scan parameters testing an d evaluation of image quality, have decided to fit this unit use condition and theerror range of specific system; In the use of volume dose assessment tools, such as DVH, TPS project assessment when considering the error of image reconstruction of volume. And according to the actual tumor growth factors such aslocation status structure selection of CT scanning parameters, combined with the practical, reasonable and effective treatment.