ABSTRACT
Objective:To test the usefulness of PET-range verification (RV) method for proton radiation accuracy verification in poly (methyl methacrylate) (PMMA) phantom using off-line PET/CT scanning.Methods:Proton irradiation dose of 2 Gy and 4 Gy were delivered in PMMA phantom. Given the difference of clinical target volume (CTV), 7 subgroups with different depth (5.0, 7.5, 10.0, 12.5, 15.0, 17.5, 20.0 cm) were set for each dose (14 radiation plans or radiation fields). PET/CT scan was performed 10 min after irradiation of 48-221 MeV proton beam. A co-registration between CT from treatment planning system and PET/CT was performed, as well as the smoothing and normalization of PET/CT data. The region of interest (ROI) and profile lines were drawn with the Raystation PET-RV software. The predictive induced radioactivity and the measured induced radioactivity profile lines were analyzed to evaluate the Δ R50, namely, the error at the position corresponding to 50% of the maximum predictive induced radioactivity at the end of both curves. Results:The size of each ROI was 5.0 cm×5.0 cm×2.5 cm. Profile lines were evenly distributed with the interval of 3 mm, and totally 289 pairs of profile lines were drew. The 2 Gy- and 4 Gy-dose groups yielded similar mean depth errors (Δ R50 between 1 mm and -1 mm with a standard deviation <1 mm). Conclusions:The off-line PET/CT scanning of PMMA phantom reveals a good agreement between predicted and measured PET data, with error of ±1 mm. The PET-RV method can be extended to clinical cases′ verification in human body treatment with further investigation.
ABSTRACT
Objective The positron generated at the dose deposition site by using high-energy carbon ions to hit the material annihilate with the negative electron in the material to release the gamma photon.The positron-emitting isotope (PEI) distributions in the target volume are activated significantly by carbon ions.Therefore, the mean values of positron emission tomography (PET) activity could be related to the delivered doses to the clinical target volume from carbon ion.This specialty can be used for the image registration fusion of the carbon ion treatment planning computed tomography (CT) and treatment verification PET-CT.After radiation in the almost same decay period, the relationship between the different target volume and the PET-CT SUV of different every single fraction dose can be found, then the range of SUV for the radiation target could be decided.So this PET-CT standardized uptake value (SUV) range can also provide a reference for the correlation and consistency in planning target dose verification and evaluation for the clinical trial.Methods The head phantom was used as a simulation of the real human body, the 1 cc, 4 cc, and 10 cc cube volume target contouring were done in the TPS, the 90 degree fixed carbon ion beams were delivered in different single fraction effective dose of 2.5 GyE, 5 GyE, and 8 GyE.After the beam delivery, later the PET-CT scanning was performed and parameters of scanning followed the trial regulation.The MIM Maestro software was used for the image processing and fusion to determine the maximum, minimum, average, and total values of SUV in the virtual clinical target volumes for the different single fraction dose.Results The results showed that for the same target volume, the SUV range of target had an approximate linear correlation with effective dose of target (P=0.000).The same effective dose for the different target volumes got the same SUV range (P>0.05).Conclusions For the carbon ion treatment plan, the SUV range from image registration and fusion of planning CT and PET-CT after treatment can be used to make an evaluation for accuracy of the dose distribution.And this method also could be used in the hyper-fraction treatment plan.In the SUV range research of different decay periods, the similar method can be performed for the exploration.