Application of 4DCT-based lung functional imaging in radiotherapy for lung cancer / 中华放射肿瘤学杂志

Radiation pneumonia is a side effect that cannot be ignored in the current radiation therapy for lung cancer. At present, there are studies and reports of the introduction of functional imaging technology into lung cancer radiotherapy plans, in which 4DCT has better application prospects in radiotherapy for lung cancer because of its advantages of simple operation, high spatial resolution and no additional cost, etc. Compared with single-photon emission computed tomography (SPECT)-CT, positron emission tomography (PET)-CT, MRI has a better application prospect in radiotherapy of lung cancer. The use of 4DCT to obtain the patient's lung function status can predict radiation pulmonary toxicity and assist clinicians to deliver prompt interventions. Moreover, it can help carry out radiotherapy for functional lung avoidance, mitigate the damage of normal lung tissues, and alleviate chest toxicity, which may have wider application value in the future. In this article, research progress on functional lung imaging algorithms based on 4DCT and the application of radiation therapy for lung cancer was reviewed.

Four-dimensional computed tomography protocol for preoperative evaluation of the parathyroid glands and its correlations with other imaging methods: a pictorial essay / Protocolo de tomografia computadorizada quadridimensional para avaliação pré-operatória da paratireoide e correlação com outros métodos de imagem: ensaio iconográfico

Abstract Parathyroid adenoma is the most common cause of primary hyperparathyroidism. Advances in surgical techniques have made it possible to excise only the affected parathyroid gland in most cases. Imaging examinations play a fundamental role in the preoperative planning of parathyroidectomy. To localize the parathyroid glands, imaging tests such as scintigraphy, ultrasound, and, more recently, four-dimensional computed tomography (4D CT). The aim of this pictorial review was to illustrate the use of the 4D CT protocol in cases of parathyroid adenoma and to determine how well it correlates with other imaging methods, in order to improve understanding of the 4D CT method.

Resumo O adenoma de paratireoide é a causa mais comum de hiperparatireoidismo primário. Com o avanço das técnicas cirúrgicas, na maioria das vezes é realizada a retirada apenas da paratireoide afetada. Para que isso seja possível, os exames de imagem têm papel fundamental. São utilizados para a localização das paratireoides exames como a cintilografia e a ultrassonografia, e recentemente a tomografia computadorizada quadridimensional (TC 4D) com protocolo específico. O objetivo deste ensaio é descrever o uso do protocolo TC 4D em casos de adenoma da paratireoide e determinar sua correlação com os outros métodos de imagem, para facilitar o entendimento do método.

Setting up a lung stereotactic body radiotherapy service in a tertiary center in Eastern India: The process, quality assurance, and early experience

Context: Stereotactic body radiotherapy (SBRT) is increasingly being used for early-stage lung cancer and lung oligometastases. Aims: To report our experience of setting up lung SBRT and early clinical outcomes. Settings and Design: This was a retrospective, interventional, cohort study. Subjects and Methods: Patients were identified from multidisciplinary tumor board meetings. They underwent four-dimensional computed tomography-based planning. The ROSEL trial protocol, the Radiation Therapy Oncology Group (RTOG) 0236, and the UK-Stereotactic Ablative Body Radiotherapy Consortium guidelines were used for target volume and organs-at-risks (OARs) delineation, dosimetry, and plan quality assessment. Each SBRT plan underwent patient-specific quality assurance (QA). Daily online image guidance using KVCT or MVCT was done to ensure accurate treatment delivery. Statistical Analysis Used: Microsoft Excel 2010 was used for data analysis. Results: Fifteen patients were treated to one or more lung tumors. One patient received helical tomotherapy in view of bilateral lung oligometastases at similar axial levels. All the remaining patients received volumetric modulated arc therapy (VMAT)-based treatment. The prescription dose varied from 40 to 60 Gy in 5–8 fractions with alternate-day treatment. The mean and median lung V20 was 5.24% and 5.16%, respectively (range, 1.66%–9.10%). The mean and median conformity indexes were 1.02 and 1.06, respectively (range, 0.70–1.18). After a median follow-up of 17 months, the locoregional control rate was 93.3%. Conclusions: SBRT was implemented using careful evaluation of OAR dose constraints, dosimetric accuracy and plan quality, patient-specific QA, and online image guidance for accurate treatment delivery. It was safe and effective for early-stage nonsmall cell lung cancer and lung metastases. Prospective data were collected to audit our outcomes

A method of dynamic scatter correction for direct 4?dimensional PET parametric imaging / 中华核医学与分子影像杂志

Objective To propose a method of dynamic scatter correction for direct 4-dimensional (4D) PET parametric image reconstruction. Methods Scatter correction for direct 4D PET parametric im-age reconstruction was achieved by extending 3-dimensional (3D) static single scatter simulation (SSS) into 4D dynamic SSS with the help of spatiotemporal cubic polynomial interpolation. The 2 h-serotonin transporter tracer 11 C-2-(2-(dimethylaminomethyl)phenylthio)-5-fluoromethylphenylamine (AFM) brain List mode data of 3 volunteers were obtained from a human brain-dedicated high resolution research tomograph (HRRT) PET scanner. Parametric images (K1 and VT ) were reconstructed by both conventional frame-based method (FM) and direct 4D method. Estimated scatter fractions by both methods were compared. Paired t test was used to analyze the data. Results Scatter fractions derived from FM and direct 4D method were 30.1％(6. 35×107 / (2.11× 108 )), 32.0％ (6.82× 107 / (2.13× 108 )) and 34.4％ (7.22× 107 / (2.10× 108 )), 30. 0％(6.33×107 / (2.11×108 )), 33.3％(7.10×107 / (2.13×108 )) and 34.1％(7.16×107 / (2.10×108 )) for the three subjects, respectively (t = -0.002, P>0.05). Scatter fractions obtained by the two methods were comparable. There was no significant difference between K1(FM: (0.51±0.11) ml·min-1 ·cm-3 , 4D: (0.48±0.09) ml·min-1 ·cm-3) and VT (FM: (24.77±11.80) ml/ cm3, 4D: (27.85±12.65) ml/ cm3) in the two methods (t values: -0.01, -0.97, both P>0.05). Conclusion The proposed dynamic scatter cor-rection method can be used for direct 4D parametric imaging and make it feasible for clinical use.

A comparison of dosimetric variance for external-beam partial breast irradiation using three-dimensional and four-dimensional computed tomography / 中华肿瘤杂志

Objective@#To investigate the potential dosimetric benefits of four-dimensional computed tomography (4DCT) compared to three-dimensional CT (3DCT) in the planning of radiotherapy for external-beam partial breast irradiation (EB-PBI).@*Methods@#Three-DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. For each patient a conventional 3D conformal plan (3D-CRT) was generated based on end-inhalation phase (EI). The treatment plan based on the 4DCT EI phase images was copied and applied to the end-exhalation phase (EE) and 3DCT images (defined as EB-PBIEI, EB-PBIEE, EB-PBI3D, respectively).@*Results@#The median volumes of the tumour bed based on 3DCT, EI and EE were 20.99 cm3, 19.28 cm3, and 18.78 cm3, respectively. The tumour bed volume based on 3DCT was significantly greater than that of EI and EE volumes (P<0.05). The planning target volumes (PTV) coverage of EB-PBI3D, EB-PBIEI and EB-PBIEE were 96.85%, 97.51%, 97.03%, respectively. The planning target volume (PTV) coverage of EB-PBI3D was significantly less than that of EB-PBIEI and EB-PBIEE (P<0.05). The median homogeneity indexs (HI) based on 3DCT, EI and EE were 0.13, 0.13, 0.13, respectively. The median conformal indexs (CI) based on 3DCT, EI and EE were 0.68, 0.69, 0.68, respectively. The median mean doses (Dmean) based on 3DCT, EI and EE were 36.20 Gy, 36.20 Gy, 36.22 Gy, respectively. However there were no significant differences in the homogeneity index, conformity index and the mean dose of PTV between the three treatment plans (P>0.05). The EB-PBI3D plan resulted in the largest organs at risk dose (P<0.05).@*Conclusion@#There was a significant benefit when using 4DCT to plan 3D-CRT for EB-PBI with regard to reduced non-target organ exposure, and might result in poor dose coverage when the PTV is determined using 3DCT.

Gross tumor volume dependency on phase sorting methods of four-dimensional computed tomography images for lung cancer

PURPOSE: To see the gross tumor volume (GTV) dependency according to the phase selection and reconstruction methods, we measured and analyzed the changes of tumor volume and motion at each phase in 20 cases with lung cancer patients who underwent image-guided radiotherapy. MATERIALS AND METHODS: We retrospectively analyzed four-dimensional computed tomography (4D-CT) images in 20 cases of 19 patients who underwent image-guided radiotherapy. The 4D-CT images were reconstructed by the maximum intensity projection (MIP) and the minimum intensity projection (Min-IP) method after sorting phase as 40%–60%, 30%–70%, and 0%–90%. We analyzed the relationship between the range of motion and the change of GTV according to the reconstruction method. RESULTS: The motion ranges of GTVs are statistically significant only for the tumor motion in craniocaudal direction. The discrepancies of GTV volume and motion between MIP and Min-IP increased rapidly as the wider ranges of duty cycles are selected. CONCLUSION: As narrow as possible duty cycle such as 40%–60% and MIP reconstruction was suitable for lung cancer if the respiration was stable. Selecting the reconstruction methods and duty cycle is important for small size and for large motion range tumors.

Gross tumor volume dependency on phase sorting methods of four-dimensional computed tomography images for lung cancer

PURPOSE: To see the gross tumor volume (GTV) dependency according to the phase selection and reconstruction methods, we measured and analyzed the changes of tumor volume and motion at each phase in 20 cases with lung cancer patients who underwent image-guided radiotherapy. MATERIALS AND METHODS: We retrospectively analyzed four-dimensional computed tomography (4D-CT) images in 20 cases of 19 patients who underwent image-guided radiotherapy. The 4D-CT images were reconstructed by the maximum intensity projection (MIP) and the minimum intensity projection (Min-IP) method after sorting phase as 40%–60%, 30%–70%, and 0%–90%. We analyzed the relationship between the range of motion and the change of GTV according to the reconstruction method. RESULTS: The motion ranges of GTVs are statistically significant only for the tumor motion in craniocaudal direction. The discrepancies of GTV volume and motion between MIP and Min-IP increased rapidly as the wider ranges of duty cycles are selected. CONCLUSION: As narrow as possible duty cycle such as 40%–60% and MIP reconstruction was suitable for lung cancer if the respiration was stable. Selecting the reconstruction methods and duty cycle is important for small size and for large motion range tumors.

A comparison of gross tumor volume among three-dimensional, four-dimensional and cone beam computed tomography in primary esophageal cancer / 中华放射医学与防护杂志

Objective To analyze the volume and position of the gross tumor volumes (GTV) in primary esophageal cancer based on contrast-enhanced three-dimensional (3D),four-dimensional (4D) and cone beam (CB) computed tomography (CT).Methods A total of thirty-four patients underwent 3D-CT and 4D-CT simulation scans for computer treatment plan and contrast-enhanced CBCT scans were conducted prior to the first treatment.GTV3D,GTV4D50,internal GTVMIP (IGTVMIP) and internal GTVCBCT (IGTVCBCT) were delineated on 3D-CT,4D-CT50 (the end expiratory phase),4D-CTMIP (the maximum intensity projection),and CBCT datasets,respectively.The IGTV10 was defined as 10 respiratory phases GTVs in 4D-CT.To evaluate the difference in position,volume and the volumes encompassed characteristic.Results The significant difference was observed in the volumes [IGTV10 ＞ (IGTVCBCT or IGTVMIP) ＞ (GTV3D or GTV4D50)] regardless of the tumor location.Regarding IGTV10 as the standard volume,the underestimations or overestimations between IGTV10 and IGTVCBCT were larger than that of between IGTV10 and JGTVMIP (t =-8.294--3.192,P ＜ 0.05).However,there was no significant difference between the areas of IGTV10 which excluded in IGTVCBCT and IGTV3D (P ＞ 0.05).The GTV4D50/ IGTVCBCT ratio for upper esophageal tumors was negatively correlated to motion vector (r =-0.756,P ＜ 0.05).The centroid coordinates of IGTVCBCT in AP direction were significantly different from the test volumes (GTV3D,GTV4D50,IGTVMIP and IGTV10) (t =-3.559--2.435,P ＜ 0.05).The IGTV10/IGTVCBCT ratio was positively correlated to motion vector (r =0.695,P ＜ 0.05) for middle esophageal tumors.The centroid coordinates of IGTVCBCT were significantly different IGTV10 (t =2.201,P ＜0.05) in AP direction.For distal esophageal tumors,the significant difference was observed in the centroid coordinate between IGTVcBcT and IGTVMIP (t =-2.365,P ＜ 0.05) in LR direction.The percentage of IGTV10 excluded the IGTVcBcT were significantly correlated to the motion vector (r =0.540,0.678,P ＜ 0.05) for both middle and distal esophageal tumors.The mean MI value of IGTVCBCT to the other four test volumes ranged from 0.65 to 0.72.Conclusions CBCT has much motion information than 3D-CT but less than IGTV10.CBCT was similar to MIP images based on respiration motion.However,the target motion information encompassed in CBCT and MIP images cannot be exchanged to each other.

Application of PET/CT combined with 4DCT in radiotherapy of esophageal carcinoma / 重庆医学

Objective To study the correlation of positron emission tomography/computed tomography (PET/CT) under different standardized uptake value (SUV) thresholds and full time four-dimensional computed tomography (4DCT) in esophageal carcinoma target delineation and explore the optimum SUV value that can accurately reflect the spatial movement of the target.Methods Eighty-two patients with esophageal cancer initial treatment in this hospital were respectively performed the scanning localization by PET/CT and 4DCT on the same day.Then different SUV thresholds (≥2.0,2.5,3.0,3.5) and the percentage of maximum SUV value (≥20％ SUV 30％ SUV 40％ SUVmax) were selected to delineate the internal gross target volume (IGTV) PET/CT in PET/CT,the ten phases of the 4DCT were collected to obtain the full time target IGTV10,the target center offset,volume ratio and conformity index (CI) were compared between the two images,the relatively good SUV value with the registration in 4DCT target was picked out,then the correlation between the target center offset,volume ratio and CI with the IGTV10 volume,long axial diameter of IGTV10,displacement of head-to-foot direction and spatial motion was analyzed.Results When the SUV threshold was 2.0 or 20 ％ SUV the spatial matching degree of 4DCT and PET/CT images was better.The head-to-foot direction displacement and special motion displacement in the target center offset of IGTVPET2.0,IGTVPET20％ and IGTV10 showed the positive correlation (P＜0.05);the volume ratio had no correlation with the IGTV10 volume,IGTV10 long axial diameter,head-to-foot direction displacement and special motion displacement (P＞0.05);CI had positive correlation with IGTV10 volume and IGTV10 long axial diameter,while had negative correlation with the head-to-foot direction displacement and special motion displacement (P＜0.05).Conclusion When SUV taking 2.0 or 20％ SUV the esophageal carcinoma target volume of PET/CT is similar to that of full time 4DCT,but there are still some deviations in the conformity index,therefore the PET/CT threshold value and 4DCT time phase selection should be further studied.

A comparison of rigid and deformable image registration at end-inhale and end-exhale phases based on 4DCT images for radiotherapy after breast-conserving surgery / 中华放射肿瘤学杂志

Objective To compare the geometric differences of gross tumor volumes(GTV)and displacements of selected clips propagated by rigid image registration(RIR)and deformable image registration (DIR)at end-inhale phase(CT0)and end-exhale phase(CT50)based on four-dimensional computed tomography(4DCT)of the whole breast after breast-conserving surgery(BCS). Methods Forty-four patients who underwent 4DCT simulation scans after BCS were selected. The GTV and displacements of selected metal clips at CT0and CT50were manually delineated by the same radiotherapy physician. Subsequently,the GTV and displacements of selected clips from CT0images were transformed and propagated to CT50images using RIR and DIR.The geometric differences of GTV and displacements of surgical clips from DIR were compared with those from RIR based on the dice similarity coefficient(DSC)and the displacements of the center of mass(COM)in the three-dimensional(3D)directions. Results The mean DSC was 0.86± 0.04 for RIR and 0.87± 0.04 for DIR(P=0.000).The displacements of COM in 3D directions from RIR were significantly greater than those from DIR(1.22 mm vs. 1.10 mm,P=0.000).In the anterior-posterior direction,the displacements from RIR were significantly greater than those from DIR for both GTV and selected clips(P=0.000).However,in the left-right and superior-inferior directions,there were no significant differences in displacements between RIR and DIR for both GTV and the selected clips(all P>0.05). Conclusions DIR can improve the overlap for GTV registration from 4DCT scans at CT0and CT50.Furthermore,DIR is superior to RIR in reflecting GTV and the displacements of selected clips in anterior-posterior direction induced by respiratory movement.

The impact of respiratory motion for target dose during external-beam partial breast irradiation / 中华放射医学与防护杂志

Objective To evaluate the impact of respiratory motion for dose of target and organ at risk during external-beam partial breast irradiation (EB-PBI).Methods 4D-CT scan sets were acquired for 20 patients who underwent EB-PBI.The volume of the tumour bed (TB) was determined based on seroma or surgical clips on the ten sets of 4D-CT images.For each patient a conventional 3D conformal plan (3D-CRT) was generated based on the 4D-CT end inhalation phase images,then copied and applied to the other phases.The following parameters were calculated to analyse:mean dose (D),homogeneity index (HI),conformal index (CI),and the volumes that received ≥ x Gy (Vx).Results During free breathing,the TB centroid motion was 0.90,0.75 and 0.80 mm in the lateral,anteroposterior and superior-inferior directions,respectively.The medium spatial motion vector was 0.95 mm.In the superiorinferior direction,TB motion significantly correlated with D HI,and CI of PTV (r =-0.458,-0.451 and 0.462,P ＜ 0.05),as well as D V20 and V30 received by the ipsilateral normal breast (r=0.527,0.488 and0.526,P ＜0.05).And in the motion vector,the D V5,V10,V20 of the ipsilateral lung all correlated with TB motion (r =0.416,0.503,0.522 and 0.498,P ＜ 0.05).A correlation also existed between dose and percent volume of heart and volume variation of heart (Dmean,V5 and V10) (r =0.727,0.704 and 0.695,P ＜ 0.05).Conclusions Small TB motion caused by respiratory motion during free breathing result in dosimetric variation of the target and potential dosimetric off-target or suboptimal dose coverage for EB-PBI.The doses of lung during free breathing were relatively sensitive to TB motion and thorax expansion,while heart doses were not influenced notably.

Detection of the correlations in target volumes for primary tumor of non-small cell lung cancer based on FDG PET/CT and the end-expiration phase of 4D-CT / 中华放射医学与防护杂志

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.

Comparison of internal gross target volumes delineated on the maximum intensity projection of four-dimensional CT images and positron emission tomography-CT for primary thoracic esophageal cancer / 中华放射医学与防护杂志

Objective To compare volumetric size, conformity index (CI), degree of inclusion (DI) of internal gross target volumes (IGTV) delineated on 4D-CT-MIP and PET-CT images for primary thoracic esophageal cancer. Methods Fifteen patients with thoracic esophageal cancer sequentially underwent enhanced 3D-CT, 4D-CT and PET-CT simulation scans. IGTVMIP was obtained by contouring on 4D-CT maximum intensity projection ( MIP). The PET contours were determined with nine different threshold methods (SUV≥2?0, 2?5, 3?0, 3?5), the percentages of the SUVmax(≥20%, 25%, 30%, 35%, 40%) and manual contours. The differences in size, conformity index (CI), degree of inclusion ( DI) of different volumes were compared. Results The volume ratios ( VRs) of IGTVPET2. 5 to IGTVMIP , IGTVPET20% to IGTVMIP, IGTVPETMAN to IGTVMIP were 0?86, 0?88, 1?06, respectively, which approached closest to 1. The CIs of IGTVPET2?0,IGTVPET2.5,IGTVPET20%,IGTVPETMAN and IGTVMIP which were 0?55, 0?56, 0?56, 0?54,0?55, respectively, were significantly larger than other CIs of IGTVPET and IGTVMIP (Z= -3?408-2?215,P 0?05). Conclusions The targets delineated based on SUV threshold setting of≥2?5, 20% of the SUVmax and manual contours on PET images correspond better with the target delineated on maximum intensity projection of 4D-CT images than other SUV thresholding methods.

Efficient approach for determining four-dimensional computed tomography-based internal target volume in stereotactic radiotherapy of lung cancer

PURPOSE: This study aimed to investigate efficient approaches for determining internal target volume (ITV) from four-dimensional computed tomography (4D CT) images used in stereotactic body radiotherapy (SBRT) for patients with early-stage non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: 4D CT images were analyzed for 15 patients who received SBRT for stage I NSCLC. Three different ITVs were determined as follows: combining clinical target volume (CTV) from all 10 respiratory phases (ITV10Phases); combining CTV from four respiratory phases, including two extreme phases (0% and 50%) plus two intermediate phases (20% and 70%) (ITV4Phases); and combining CTV from two extreme phases (ITV2Phases). The matching index (MI) of ITV4Phases and ITV2Phases was defined as the ratio of ITV4Phases and ITV2Phases, respectively, to the ITV10Phases. The tumor motion index (TMI) was defined as the ratio of ITV10Phases to CTVmean, which was the mean of 10 CTVs delineated on 10 respiratory phases. RESULTS: The ITVs were significantly different in the order of ITV10Phases, ITV4Phases, and ITV2Phases (all p < 0.05). The MI of ITV4Phases was significantly higher than that of ITV2Phases (p < 0.001). The MI of ITV4Phases was inversely related to TMI (r = -0.569, p = 0.034). In a subgroup with low TMI (n = 7), ITV4Phases was not statistically different from ITV10Phases (p = 0.192) and its MI was significantly higher than that of ITV2Phases (p = 0.016). CONCLUSION: The ITV4Phases may be an efficient approach alternative to optimal ITV10Phases in SBRT for early-stage NSCLC with less tumor motion.

Measurement of Intra-Fraction Displacement of the Mediastinal Metastatic Lymph Nodes Using Four-Dimensional CT in Non-Small Cell Lung Cancer

OBJECTIVE: To measure the intra-fraction displacements of the mediastinal metastatic lymph nodes by using four-dimensional CT (4D-CT) in non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Twenty-four patients with NSCLC, who were to be treated by using three dimensional conformal radiation therapy (3D-CRT), underwent a 4D-CT simulation during free breathing. The mediastinal metastatic lymph nodes were delineated on the CT images of 10 phases of the breath cycle. The lymph nodes were grouped as the upper, middle and lower mediastinal groups depending on the mediastinal regions. The displacements of the center of the lymph node in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured. RESULTS: The mean displacements of the center of the mediastinal lymph node in the LR, AP, and SI directions were 2.24 mm, 1.87 mm, and 3.28 mm, respectively. There were statistically significant differences between the displacements in the SI and LR, and the SI and AP directions (p < 0.05). For the middle and lower mediastinal lymph nodes, the displacement difference between the AP and SI was statistically significant (p = 0.005; p = 0.015), while there was no significant difference between the LR and AP directions (p < 0.05). CONCLUSION: The metastatic mediastinal lymph node movements are different in the LR, AP, and SI directions in patients with NSCLC, particularly for the middle and lower mediastinal lymph nodes. The spatial non-uniform margins should be considered for the metastatic mediastinal lymph nodes in involved-field radiotherapy.

Impact of delineator and delineating criteria on the target delineation of the peripheral lung cancer based on four-dimensional computed tomography / 中华放射医学与防护杂志

Objective To investigate the impact of delineator and delineating criteria on the target delineation of the peripheral lung cancer based on four-dimensional computed tomography (4D-CT).Methods The 4D simulation CT images of twelve patients with peripheral lung cancer were selected.Before and after the establishment of the target delineation criteria,six radiation oncologists were asked to delineate the targets based on 4D-CT images at the end-inhalation phase (0％),end-exhalation phase (50％),and three-dimensional computed tomography (3D-CT) images respectively.The delineated targets were denominated as GTV0,GTV50,GTV3D.IGTVIN+Ex was created by combining GTV0 and GTV50.IGTVMIP was delineated based on the maximum intensity projection (MIP) of 4D-CT.The interand intra-observer variability before and after the establishment of the delineation criteria was compared.Results The mean coefficients of variation of GTV0,GTV50,GTV3D,IGTVMIP and IGTVIN+Ex delineated by the six delineators before and after the establishment of the delineation criteria were 0.50 ± 0.25 vs 0.24 ±0.10,0.52 ±0.38 vs 0.26 ±0.12,0.45 ±0.19 vs 0.20 ±0.07,0.54 ±0.27 vs 0.23 ±0.09 and 0.44±0.23 vs 0.26 ±0.09,respectively.The differences were statistically significant(t =3.38,2.44,3.60,4.20,3.11,P ＜ 0.05).No statistically significant difference was found in the volume of the same target for GTV0,GTV50,GTV3D,IGTVMIP and IGTVIN+Ex delineated by the six oncologists before and after the establishment of the delineation criteria.For delineator 3 and 6,the differences of GTV0,GTV50,IGTVIN+EX before and after establishment of the delineation criteria were statistically significant(t =2.46,2.91,3.28,P ＜0.05 ;t =2.40,2.79,3.22,P ＜0.05).For delineator 4,the differences of GTV0,GTV50,IGTVIN+EX,IGTVMIP,GTV3D before and after establishment of the delineation criteria were statistically significant (t =2.70,3.21,3.04,3.99,3.00,P ＜ 0.05).Conclusions The unified delineation criteria can significantly reduce the inter-observer variability in delineating the GTVs based on 3D-CT or 4D-CT images,and in delineating the IGTVMIP based on 4D-CT images of peripheral lung cancer patients.However,regarding the same delineator,various influences of the unified delineation criteria on the target delineation are observed.