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Objective To analyze the precision and stability of optical surface imaging system for patients who received radiotherapy with active breath control. Methods Eighteen radiotherapy patients with lung metastasis were managed by active breath control (ABC).The difference error detected by optical surface imaging system and CBCT were defined as the precision of optical surface imaging system. The variation among the error of optical surface imaging positioning the value of correction of treatment position and the error detected by optical surface imaging again were defined as the stability of optical surface imaging system. Intrafractional errors were analyzed by optical surface imaging system through whole treatment process (including breath hold and free breath). Results The optical surface imaging system had precision (systematic (Σ) and random errors (σ)) of 1.78/3.42 mm 2.54/6.57 mm and 2.79/3.22 mm respectively and stability of2.12/2.54 mm 3. 09/4.02 mm and 1.37/3.55 mm respectively in lateral-medial superior-inferior and anterior-posterior directions. The intrafractional errors (Σ and σ) were 0.42/0.85 mm 0.41/1.47 mm and 0.41/1.47 mm respectively for breath hold duration and 4.76/4.16 mm 6.54/7.78 mm and 3.13/5.92 mm for free breath duration in lateral-medial superior-inferior and anterior-posterior directions. Conclusions As an effective method for validate breath hold;Optical surface imaging system can improve the precision and safety of active breath control. However,the factors that affect the accuracy and stability of the optical surface imaging system in patients undergoing radiotherapy with ABC are not clear;it cannot replace the CBCT for positioning verification.
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Objective To compare the normal thickness of the esophageal wall measured by contrast?enhanced three?dimensional ( 3DCT ) , four?dimensional ( 4DCT ) , and cone beam computed tomography ( CBCT) ,and to provide a basis for target volume delineation in esophageal cancer. Methods From 2009 to 2016,thoracic contrast?enhanced 3DCT and 4DCT simulations were performed in 50 patients with lung cancer or metastatic lung cancer. Contrast?enhanced CBCT scans were acquired during the first three?dimensional conformal radiotherapy. The normal esophageal wall was contoured on 3DCT images, the end?exhalation phase of 4DCT images ( 4DCT50 ) , the maximum intensity projection of 4DCT images (4DCTMIP),and CBCT images. The wall thickness was measured on each segment and the average thickness of esophageal wall was obtained. Comparison of the thickness of a fixed segment of esophageal wall between different CT images was made by paired t test. Comparison of thickness on the same type of CT images between different segments of esophageal wall was made by one?way analysis of variance. Results For the thoracic and intra?abdominal segments,there was no significant difference in the thickness of esophageal wall between 3DCT and 4DCT50 images ( P= 0?056?0?550 );however, the thickness of esophageal wall was significantly smaller on 3DCT images than on 4DCTMIP or CBCT images (P=0?000?0?004).For the upper and middle thoracic segments,the thickness of esophageal wall was significantly larger on CBCT images than on 4DCTMIP images ( P= 0?008, P= 0?001 ) . On 3DCT, 4DCT50 , and 4DCTMIP images, the thickness of esophageal wall was significantly larger in the lower thoracic segment than in the upper or middle thoracic segments ( P=0.008~0?041);the intra?abdominal segment had a significantly larger thickness of esophageal wall than the thoracic segments ( all P=0?000 ) . There was no significant difference in wall thickness on CBCT images between three thoracic segments ( P=0.088~0?945) . Conclusions A uniform criterion can be adopted to judge the normal thickness of esophageal wall in gross tumor volume ( GTV ) delineation on 3DCT and 4DCT50 images for thoracic esophageal cancer. However,caution should be taken when 5 mm is used as a criterion for normal thickness of esophageal wall in GTV delineation on 4DCTMIP and CBCT images.
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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.
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Objective To investigate change of the volume and the epicenter of target volume under different scan speed of the three-dimensional (3D) simulation computed tomography (CT) and determine the scan speed which close to ITV.Methods A dynamic phantom-QUASAR,with a 3 cm × 3 cm × 3 cm target cubic simulating respiratory motion was used.The phantom was set with three different amplitudes and breathing frequencies under different scan speed.The dynamic phantom was also scanned using simulation 4DCT as ITV was the standard.The length of the phantom was 12 cm,the scan time were 6.6 s,12.8 s,31.7 s.The volume and epicenter of the target identified from 3DCT images were calculated and compared to 4DCT images.The number of times of target length (30 ± 2) mm/total scan times was used to assese the accuracy.Results The total accuracy was 6.8％.For different scan speed,the accuracy were 13％,4％ and 2％,respectively.The length of the epicenter of the target volume was (318.9 ±0.37) mm,(683.2 ±0.44) mm,(682.9 ± 0.66) mm under the 0.5 cm,1.0 cm and 2.0 cm,respectively.When the scan time was 31.7 s,the volume of the target from the 3DCT were close to ITV-10 mm,the frequency were 50％,78％,56％ for three different amplitude.Conclusions This study shows that the images from the 3D simulation CT were the partial image of the breathing cycle,and the epicenters were diversed with the breathing amplitude and scan speed.The accuracy rate of the 3DCT reflects the real target is low.In addition,the epicenter of the target changed randomly.
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Objective To compare the position,volume and matching index (MI) of patientspecific internal gross tumor volume (IGTV)delineated by 4 different approaches based on three- dimensional and four - dimensional CT ( 3 DCT and 4 DCT ) image for primary esophageal cancers.Methods Thirteen patients with primary esophageal cancer underwent 3DCT and 4DCT simulation scans during free breathing,and the patient were divided into group A (tumor located in the proximal thoracic esophagus) and B (tumor located in the mid-and distal thoracic esophagus).IGTV were delineated using four approaches: The gross tumor volume (GTV) contours from 10 respiratory phases were combined into IGTV10 ;IGTV2 was acquired by combining the GTV from 0％ and 50％ phases; IGTVMIP was the GTV contour delineated from the maximum intensity projection (MIP) ;IGTV3D was acquired from the enlargement of 3 DCT-based GTV by each spatial direction on the motion amplitude measured in the 4DCT.ResultsTarget movement in lateral (LR),anterio-posterior (AP),superio-inferior (SI) directions showed no statistically significant difference (0.11 cm,0.09 cm,0.18 cm,respectively; χ2 =1.06,P=0.589),and there was no statistically significant difference in centroid positions between IGTV10 and IGTV2 or IGTV3D in group A (t =-2.24,-0.00,P =0.089,- 1.000 ),MI between IGTV10 and IGTV2,IGTV10 and IGTV3D were 0.88,0.54,respectively. For group B, target movement amplitude in SI direction was bigger than in LR, AP ( 0.47 cm,0. 15cm,0. 12 cm,X2= 12.00,P = 0.002).Therewasno significantdifference betweenIGTV10 andIGTV3D inLR, AP, SI ( t =- 0.80.- 0.82,- 1.16,P = 0.450.0.438.0.285 ), MI was 0.59 ; but the target center coordinates was demonstrated significant difference in SI between IGTV10 and ICTV2 for group B ( t = 2.97.P = 0.021 ), Mlwas 0.86.Thevolume of IGTVMIPwassmaller thanIGTV10 ( t =- 2.84,P = 0.025 ), but the position of IGTv10 and ICTVMIp were with no statistically significant difference in the LR,AP,SI ( t =- 0.25,0. 84. - 1.22,P = 0. 809,0.429.0.263 ) ,MIbetweenIGTV10andIGTVMIp was 0.78.Conclusions Patient-specific IGTV can be acquired from 4DCT with correct target coverage while avoiding a geographic miss for the thoracic esophageal cancer,but IGTV2 and IGTVMIP can not contain all the information about primary tumor position,shape.and size at different phases of the respiratory cycle.
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Objective To research the feasibility of using three-dimensional CT (3DCT) associated with active breathing control (ABC) in determination of the individual internal tumor volume (ITV) for hepatocellular carcinoma (HCC) comparing the four-dimensional CT (4DCT).Methods After 4DCT scans of 15 HCC patients who had accepted TACE,completed the 3DCT scans associated with ABC in three ways of breathing:free breathing ( FB),end inspiration hold ( EIH),end expiration hold (EEH).4DCT images were sorted into 10 phases and the maximum intensity projection (MIP) images were constructed.The GTVs were manually contoured on 4DCT and 3DCT images (labeled as GTV0,GTV10.….GTV90,GTVMIP,,GTVFB,GTVEIH and GTVEEH).GTV0…GTV90,GTV0 and GTV50,GTV0,GTV20 and GTV50,GTVEIH and GTVEEH were respectively merged into IGTV1,IGTV2,IGTV3,IGTV4.The volume and geometry displacement of GTVs and IGTVs were compared.Results All patients were compatible with the ABC technique and completed the CT scans in two ways.The motion of diaphragm measured between 4DCT and 3DCT images was not significantly different ( 1.39 cm and 1.39 cm,t =-0.02,P =0.983 ),it was similar to the volume difference among GTV0,GTV20,GTV50,GTVEIH,GTVEEH and GTVFB (56.4,54.6,55.5,55.6,55.2,59.7 cm3,F =0.01,P =1.000 ).The comparison result of volume difference among IGTV1,IGTV2,IGTV3,IGTV4 and GTVMIP (77.9,71.4,73.4,72.3 and 66.3 cm3,F =0.02,P =1.000)were similar to the differences of geometry displacement in x,y and z axial among them (F =0.48,0.04,0.02,P =0.750,0.997,0.999,respectively).Conclusion The application of 3DCT associated with ABC in determination of the individual IGTV for HCC is feasible and safe comparing to 4DCT.