| Precise radiation therapy is the trend of the modern radiation oncology development.It is also an advanced technology to improve cancer cure rate with reducing complications and radiation therapy side effects.Dose verification plays an important role to make the treatment plan more accurate and improve the gain ratio of radiation therapy.However,current methods based on transmitted dose verification cannot gather three-dimensional real-time dose verification for the target volume.With improvement of positron emission tomography and particle therapy technology,the combination of them can be used more and more for biological dose verification.The specialty is high-energy carbon ions hit the body tissue and the positron is effected at the position of dose distribution,then the positron and the original electron of tissue will annihilate to release the gamma photon.Positron-Emitting Isotope(PEI)distributions activated by carbon-ions are significantly different at depths near the distal edges of doses.Because the Bragg-Peak of carbon ions is narrower and a peak-like PEI distributions by carbon ions was observed with flatter distribution toward to proximal depth.Therefore,mean values of PET activity could be related to delivered doses to the clinical target volume by carbon ion.This specialty can be used for the image fusion of the carbon ion treatment planning CT and online treatment target PET-CT,after radiation in the same decay period,the relationship between the different target volume and the PET-CT SUV of every different single fraction dose can be found,then the range of SUV for the radiation target could be decided.So this online PET-CT SUV range also can provide reference for the correlation and consistency in planning target dose verification and evaluation for the clinical trial.the head phantom can be used as a simulation of the real human body,the 1cc,4cc and 10 cc cube volume target contouring are done in the TPS,the 90 degree fixed carbon ion beams should be delivered in different single fraction effective dose of 2.5Gy,5Gy and 8Gy.After the beam delivery,later the PET-CT scanning is performed after about 7 minutes,the scanning period is 30 minutes,and parameters of scanning follow the trial regulation.The MIM Maestro software is used for the image processing and fusion,the software function should be performed to find out the max,min,median and average value of SUV in the virtual clinical target volumes for the different single fraction dose.The result of this research shows for the same volume,the SUV range of target have a linear relationship with effective dose of target;otherwise,the same effective dose can give the same SUV range to all the different volume targets,there is no obvious difference between them.So the method of making an evaluation for accuracy of the dose distribution using the SUV range which is from the planning CT with after treatment online PET-CT fusion for the carbon ion treatment plan is available.And this method also can be used in the hyper-fraction treatment plan.In the SUV range research of different decay period,the similar method can be performed for the exploration. |
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