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Objective:To evaluate the spatial position and functional parameters of 18F-FDG PET-CT and diffusion-weighted imaging (DWI) before and during radiotherapy (RT) based on the medium of 3DCT in patients with esophageal cancer and to explore whether the high-signal area derived from DWI can be used for individualized definition of the volume in need of dose-escalation for esophageal cancer. Methods:Thirty-two patients with esophageal cancer treated with concurrent chemoradiotherapy or neoadjuvant chemoradiation sequentially underwent repeated 3DCT, 18F-FDG PET-CT and enhanced MRI scans before RT and at the 15 th time of RT. All images were fused with the 3DCT images by deformable registration. The gross tumor volume (GTV) was delineated based on PET Edge on the first and second 3DCT, PET-CT and DWI and corresponding T 2-weighted MRI (T 2W-MRI) fused images, and defined as GTV CTpre and GTV CTdur, GTV PETpre, GTV PETdur, GTV DWIpre and GTV DWIdur, respectively. SUV (SUV max, SUV mean, SUV peak), MTV, TLG, ADC (ADC min and ADC mean) values and △SUV (△SUV max, △SUV mean, △SUV peak), △MTV, △TLG, △ADC (△ADC mean and △ADC min) of lesions were measured before and during RT. Results:The differences in SUV (SUV max, SUV mean, SUV peak), MTV, TLG, ADC mean and ADC min of the GTV before and during RT were statistically significant (all P<0.001). The tumor ADC and SUV values before and during RT showed no significant correlation, and there was no correlation between △ADC and △SUV (both P>0.05). The conformity index (CI) of GTV PETpre to GTV DWIpre was significantly higher than that of GTV PETdur to GTV DWIdur ( P<0.001). The shrinkage rate of maximum diameter (△LD DWI)(24%) and the shrinkage rate of tumor volume (VRR DWI)(60%) based on DWI during RT were significantly greater than the corresponding PET-based △LD PET (14%) and VRR PET (41%)( P=0.017 and P<0.001). Conclusions:The location of high residual FDG uptake based on PET-CT yields poor spatial matching compared with the area with residual high signal based on DWI during RT. Tumor ADC and SUV values may play complementary roles as imaging markers for prediction of patterns of failure and for definition of the volume in need of dose-escalation. In addition, the shrinkage rates of tumor maximum diameter/volume based on DWI during RT are significantly faster than those based on PET-CT. Therefore, the feasibility of selecting boosting of the high signal area derived from DWI for individualized definition of the volume for esophageal cancer is not clear.
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Objective:To explore the interobserver variabilities in the delineation of the target volume using simulation three-dimensional computed tomography (3DCT) between the supine and prone positions for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS).Methods:Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study. All patients underwent axial 3DCT simulation scanning in the supine and prone positions during free breathing. Based on two different simulation 3DCT acquired, the gross target volume (TB) formed by using surgical clips and the clinical target volume (CTV) were delineated by five radiologists using specific guidelines. The following parameters including the target volume, coefficient of variations (COV) and matching degree (MD) were calculated to analyze the interobserver variability. Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study.Results:Whether in the supine or prone position, the interobserver variabilities for TB and CTV were statistically significant ( P<0.001, P=0.001, P<0.001, P=0.001). And the intersection of CTV in the prone position was 5.79 cm 3 greater than that in the supine position ( P=0.011). The interobserver variability of COV CTV in the prone positionwas significantly lower than that in the supine position ( P=0.014). And the interobserver variabilities of MDTB TB and MDTB CTV in the prone positionwere statistically greater than those in the supine position, respectively ( P<0.001, P= 0.001). Conclusions:When delineating the target volume of EB-PBI in the prone position, the interobsever variability can be reduced compared with that in the supine position. Hence, it is more reasonable to carry out EB-PBI in the prone position in free breathing.
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Objective To evaluate the dosimetric effects of target volume delineation with metal clip and seroma,alone or in combination,on external-beam partial breast irradiation (EB-PBI) based on four-dimensional computed tomography (4DCT).Methods Twenty female patients undergoing EB-PBI from 2009 to 2013 were enrolled as subjects.The gross tumor volumes (GTVs),GTVC,GTVS,and GTVC+S,were delineated on 4DCT images at 10 phases using metal clip,seroma,and both of them,respectively.The GTVS on 4DCT images at 10 phases were fused to generate the internal gross tumor volumes (IGTVS),IGTVC,IGTVS,and IGTVC+S.The planning target volumes (PTVS),PTVC,PTVS,and PTVC+S,were obtained via expansion of margin by 15 mm.The three-dimensional conformal radiotherapy plans were made by one physician based on PTVC,PTVS,and PTVC+S on end-inhalation images.The target volume,homogeneity index (HI),conformity index (CI),and doses to organs at risk were compared between the three groups.Results The C+S group had the largest IGTV,PTV,and the ratio of PTV to diseased breast volume,which was followed by the C group and the S group (all P＜ 0.05).The S group had significantly lower doses to the ipsilateral normal breast and lung than the C group and the C+S group (all P＜0.05).There were no significant differences in HI or CI between the three groups (all P＞ 0.05).Conclusions The volume variation caused by target volume dehneation on 4DCT images based on different references has little impact on dose distribution in target volume.However,it has substantial impact on radiation doses to the ipsilateral normal breast and lung.
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Objective To investigate the correlations in target volumes based on positron emission tomography CT (PET/CT) and the end-expiration phase of four-dimensional CT (4D-CT) images for non-small cell lung cancer (NSCLC).Methods Seventeen patients with NSCLC sequentially underwent three-dimensional CT (3DCT),4D-CT and 18F-FDG PET/CT thoracic simulation scans.The gross target volume (GTV) was contoured on the end-expiration phase (50％) of 4D-CT and defined as GTV50％.The internal gross target volumes (IGTV) based on PET/CT images (IGTVPET) were determined by the standardized uptake value (SUV) 2.0 (IGTVPET2.0) and 20％ percentage of the maximal standardized uptake value (SUVmax) (IGTVPET20％).The following parameters were calculated to analyze the correlation between IGTVPET and GTV50％ in volume ratio (VR) and conformity index (CI):maximum transverse diameter of GTV50％,volume of GTV50％,the displacement of GTV in the cranial-caudal direction and 3D Vector calculated from 4D-CT dataset as well as the SUVmax.Results There was no significant correlation between the VR of IGTVPET2.0 to GTV50％ and the maximum transverse diameter of GTV50％,volume of GTV50％,the displacement of GTV in the cranial-caudal direction,3D Vector and the SUVmax (P ＞ 0.05).The VR between IGTVPET20％ and GTV50％ inversely related to maximum transverse diameter of GTV50％,volume of GTV50％ and SUVmax (r =-0.663,-0.669,-0.752,P ＜0.05).The CI between IGTVPET2.0 and GTV50％ positively related to volume of GTV50％ and maximum transverse diameter of GTV50％ (r =0.613,0.483,P ＜ 0.05).Conclusions 3D PET images provide a time-averaged image of the tumor during the numerous breathing cycle.They fail to include the full information of moving tumor.The target volumes based on 3D PET might not reflect the real IGTV of NSCLC.
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Objective To investigate the differences in position and volume between planning target volumes (PTV) based on positron emission tomography?computed tomography (PET?CT) images with an standardized uptake value ( SUV) no less than 2?5, 20% of the maximum SUV ( SUVmax ), or 25% of SUVmax , three?dimensional ( 3D ) CT, and four?dimensional ( 4D ) CT in thoracic esophageal cancer. Methods Eighteen patients with thoracic esophageal cancer sequentially received chest 3DCT, 4DCT, and [18F]fluoro?2?deoxy?D?glucose (FDG) PET?CT scans. PTV3D was obtained by conventional expansion of 3DCT images;PTV4D was obtained by fusion of target volumes from 10 phases of 4DCT images. The internal gross tumor volumes ( IGTV) , IGTVPET2.5 , IGTVPET20%, and IGTVPET25%, were generated based on PET?CT images with an SUV no less than 2?5, 20% of SUVmax , and 25% of SUVmax , respectively. These IGTVs were expanded longitudinally by 3?5 cm and radically by 1 cm to make PTVPET2.5 , PTVPET20%, and PTVPET25%, respectively. Results PTV3D was significantly larger than both PTV4D and PTVPET(P=0?000 -0?044), while there was no significant difference between PTV4D and PTVPET ( P= 0?216 -0?633 ) . The mutual degrees of inclusion ( DIs ) between PTV3D and PTV4D were 0?70 and 0?95, respectively, which were negatively correlated with 3D?Vector ( P=0?039). The mutual DIs between PTVPET2.5, PTVPET20%, and PTVPET25% were 0?74, 0?72, 0?78, 0?73, 0?77, and 0?70, respectively, which showed no correlation with 3D?Vector (P=0?150 -0?822). The mutual DIs between PTV3D and PTVPET were 0?86, 0?84, 0?88, 0?63, 0?67, and 0?59, respectively. Conclusions It is difficult to achieve complete volumetric overlap of PTVs based on 3DCT, 4DCT and PET?CT in thoracic esophageal cancer due to different target volume information. PET scan during free breathing should be used with caution to generate PTVs in thoracic esophageal cancer.