Application Of CT Perfusion Imaging In The Formation Of Radiation Pneumonitis In Thoracic Tumor After Radiotherapy

Objective To measure perfusion parameters values and relative values of regional lung tissue in thoracic tumor after radiotherapy with different doses and to investigate the relation between the change of perfusion parameters values and the formation of radiation pneumonitis(RP), with the technique of CT perfusion imaging(CTPI).Methods 64 slices spiral CTPI were performed in 37 patients with thoracic tumor before and after irradiation with different doses in different phases. And varied perfusion parameters of region of interest(ROI) in lung tissue were assessed such as blood flow(BF), blood volume(BV), time to peak(TTP), permeability surface(PS), mean transit time (MTT) and Hounsfield unit(HU) and relative values of these parameters were calculated, i.e., rBF, rBV, rTTP, rPS, rMTT, rHU. (1) The perfusion parameters values of local non-tumor peripheral lung tissue were evaluated before irradiation. (2) The change of the parameters values and relative values were studied undergoing different dose radiotherapy. (3) The clinical value of CTPI parameters was estimated on predicting RP.Results (1)The values of perfusion parameters of non-tumor peripheral lung tissue before irradiation were as follows: BF 146.14±73.71ml/100ml/min,BV 142.60±64.10ml/100ml,TTP 7.55±1.62 s,MTT 9.96±1.58 s. And the data had no difference among lung or non-lung cancer and different gender as well. (2)The values of BF,BV,PS rose accompanied by the enhancement of dose. And RP occurred in the cases with the remarkable boost in rBF,rBV and rPS(P<0.05),while RP would not happen if rBF significantly ascended only. When rBF and rPS had both arisen distinctly with two latter dose(P<0.05), grade 2 RP would occur and grade 1 RP occurred with only rPS went up significantly(P<0.05). (3)The index of rBF combined with rBV was more valuable than single parameter in predicting grade 1-2 RP with high specificity(85.2% or 88.9%), total consistent rate(88.6% or 91.5% )and positive predictive value(66.7% or 72.7%).Conclusion (1)The rule of perfusion change of lung tissue after irradiation could be detected with CTPI and it had been demonstrated that the application of CTPI in studying lung perfusion and RP was valuable. (2)The parameters such as rBF, rBV and rPS had an important role in forecasting RP. (3)Grade 1-2 RP could be predicted with the parameters of CTPI and the index of rBF combined with rBV was recommended.