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In the delivery of stereotactic radiosurgery (SRS) by linear accelerator (LINAC), dynamic conformal arc therapy (DCAT) with non-coplanar beams is conventionally used. However, volumetric modulated arc therapy (VMAT) can improve target conformity, thereby decreasing the dose to organs at risk by inversed planning methods, but few studies have directly compared DCAT and VMAT with and without non-coplanar beams in patients with single brain metastasis. We therefore conducted a planning study to compare the dose distribution in DCAT, VMAT using only a coplanar arc (CoVMAT) and VMAT with non-coplanar arcs (NcVMAT) in the treatment of single brain metastasis. DCAT, CoVMAT and NcVMAT plans were created for 15 patients. The three modalities were compared in terms of target conformity, target coverage, the dose to normal brain tissue, monitor units (MUs) and beam-on time. Both conformity indices (RTOG-CI and IP-CI) as well as the D98% of the gross target volume (GTV) were significantly better in the NcVMAT plans than in the DCAT plans. Comparisons of the doses to normal brain tissue revealed that the V20Gy, V15Gy, V12Gy, V10Gy and V5Gy were significantly smaller in the NcVMAT plans than in the plans based on the other two modalities. The MUs of the DCAT and NcVMAT plans were larger than those of the CoVMAT plans, and the beam-on time was longer in the NcVMAT and CoVMAT plans than in the DCAT plans. Compared to the CoVMAT and DCAT plans, NcVMAT plans significantly improved target conformity and reduced the doses to normal brain tissue at V20Gy, V15Gy, V12Gy, V10Gy and V5Gy.

PURPOSE To investigate the clinical value of transrectal ultrasound in judging the Gross Target Volume (GTV) of cervical cancer (CC). METHODS A total of 196 CC patients admitted to the Department of Radiotherapy, China-Japan Union Hospital, Jilin University, from January 2016 to June 2019 were selected as the study subjects. The GTVs before and after applicator insertion were determined by transrectal ultrasound and compared with those judged by MRI. RESULTS All 196 patients were successfully undergoing applicator insertion according to the pretreatment plan. The GTV doses reached the clinical requirements during treatment. There was no significant difference between the GTVs judged by MRI and ultrasound before insertion in terms of upper/lower diameter (MRI Before 1 vs. Ultrasound Before 1) (MB1 vs. UB1), left/right diameter (MB2 vs. UB2), or ventral/dorsal diameter (MB3 vs. UB3), and the intragroup correlation coefficients (ICC) were 0.59, 0.77, and 0.66, respectively; moreover, there was no significant difference between the GTVs judged by MRI and ultrasound after insertion in terms of MRI After one vs. Ultrasound After one (MA1 vs. UA1), MA2 vs. UA2, and MA3 vs. UA3, and the ICC values were 0.62, 0.79, and 0.76, respectively. CONCLUSIONS Transrectal ultrasound can satisfactorily determine the GTV of CC and has certain value in brachytherapy for CC.

Shuli Hu,1 Man Luo,2 Yaling Li1 1Department of Intensive Care Unit, Wuhan No. 1 Hospital, Wuhan, 430022, People’s Republic of China; 2Department of Oncology, Wuhan No.1 Hospital, Wuhan, 430022, People’s Republic of ChinaCorrespondence: Yaling LiDepartment of Intensive Care Unit, Wuhan No.1 Hospital, 215 Zhongshan Road, Wuhan, Hubei Province, People’s Republic of ChinaTel +86 027-85332691Email 2861696710@qq.comPurpose: The lymph node gross target volume (GTV) delineation in patients with non-small cell lung cancer (NSCLC) is crucial for prognosis. This study aimed to develop a predictive model that can be used to differentiate between lymph nodes micrometastasis (LNM) and non-lymph nodes micrometastasis (non-LNM).Patients and Methods: A retrospective study involving 1524 patients diagnosed with NSCLC was collected in the First Hospital of Wuhan between January 1, 2017, and April 1, 2020. Duplicated and useless variables were excluded, and 16 candidate variables were selected for further analysis. The random forest (RF) algorithm and generalized linear (GL) algorithm were used to screen out the variables that greatly affected the LNM prediction, respectively. The area under the curve (AUC) was compared between the RF model and GL model.Results: The RF model revealed that the variables, including pathology, degree of differentiation, maximum short diameter of lymph node, tumor diameter, pulmonary membrane invasion, clustered lymph nodes, and T stage, were more significant for LNM prediction. Multifactorial logistic regression analysis for the GL model indicated that vascular invasion, tumor diameter, degree of differentiation, pulmonary membrane invasion, and maximum standard uptake value (SUVmax) were positively associated with LNM. The AUC for the RF model and GL model was 0.83 (95% CI: 0.75 to 0.90) and 0.64 (95% CI: 0.60 to 0.70), respectively.Conclusion: We successfully established an accurate and optimized RF model that could be used to predict LNM in patients with NSCLC. This model can be used to evaluate the risk of an individual patient experiencing LNM and therefore facilitate the choice of treatment.Keywords: non-small cell lung cancer, lymph nodes micrometastasis, prediction model, random forest, gross target volume, machine learning

Background and purpose To compare 68Ga-fibroblast activation protein inhibitor (FAPI) and 18F-FDG PET/CT in imaging locally advanced oesophageal cancer, and evaluate the potential usefulness of 68Ga-FAPI PET/CT on gross target volume (GTV) delineation aimed at radiotherapy planning for oesophageal cancer as compared with contrast-enhanced CT (CE-CT) and 18F-FDG PET/CT. Materials and methods Twenty-one patients with newly diagnosed oesophageal cancer who underwent both 18F-FDG and 68Ga-FAPI PET/CT scans were selected. GTVs of the primary tumours based on CE-CT (GTVCT), PET/CT, and CE-CT plus PET/CT were delineated. Gross tumour lengths were measured by GTVs and endoscopy and recorded. Results The 68Ga-FAPI PET showed significantly higher radiotracer uptake than 18F-FDG PET (median SUVmax 16.71 vs. 11.23; P = 0.002) in the primary tumours. SUV thresholds of FAPI ×20%, 30%, 40%, and FDG ×40% showed similar lesion lengths compared with that in endoscopic examination (P > 0.05). GTVCT demonstrated the largest volume (median: 48.80 mm3, range: 14.83–162.23 mm3) than PET-based GTVs. For PET/CT-guided complementary contouring of GTVCT, four patients (19%) were increased by FAPI ×20% and 30%, two patients (9.5%) were increased by FAPI ×40%, and only one patient was increased by FDG ×40%. Furthermore, the volume of GTV based on CE-CT plus FAPI ×20%, 30%, and 40% showed no significant difference with GTVCT and planning target volume based CE-CT plus FAPI-PET and meets the organ at risk standard. Conclusion The 68Ga-FAPI PET/CT methodology showed favourable tumour-to-background contrast in oesophageal cancer and might provide additional information for target volume delineation and help avoid tumour geographic misses.

Purpose The application value of 18 F-FDG PET-CT combined with MRI in the radiotherapy of esophageal carcinoma was discussed by comparing the differences in position, volume, and the length of GTVs delineated on the end-expiration (EE) phase of 4DCT, 18 F-FDG PET-CT, and T2 W-MRI. Methods A total of 26 patients with thoracic esophageal cancer sequentially performed 3DCT, 4DCT, 18 F-FDG PET-CT, and MRI simulation for thoracic localization. All images were fused with the 3DCT images by deformable registration. GTVCT and GTV50% were delineated on 3DCT and the EE phase of 4DCT images, respectively. The GTV based on PET-CT images was determined by thresholds of SUV ≥ 2.5 and designated as GTVPET2.5 . The images of T2 -weighted sequence and diffusion-weighted sequence were referred as GTVMRI and GTVDWI , respectively. The length of the abnormality seen on the 4DCT, PET-CT, and DWI was compared. Results GTVPET2.5 was significantly larger than GTV50% and GTVMRI (P = .000 and 0.008, respectively), and the volume of GTVMRI was similar to that of GTV50% (P = .439). Significant differences were observed between the CI of GTVMRI to GTV50% and GTVPET2.5 to GTV50% (P = .004). The CI of GTVMRI to GTVCT and GTVPET2.5 to GTVCT were statistically significant (P = .039). The CI of GTVMRI to GTVPET2.5 was significantly lower than that of GTVMRI to GTV50% , GTVMRI to GTVCT , GTVPET2.5 to GTV50% , and GTVPET2.5 to GTVCT (P = .000-0.021). Tumor length measurements by endoscopy were similar to the tumor length as measured by PET and DWI scan (P > .05), and there was no significant difference between the longitudinal length of GTVPET2.5 and GTVDWI (P = .072). Conclusion The volumes of GTVMRI and GTV50% were similar. However, GTVMRI has different volumes and poor spatial matching compared with GTVPET2.5 .The MRI imaging could not include entire respiration. It may be a good choice to guide target delineation and construction of esophageal carcinoma by combining 4DCT with MRI imaging. Utilization of DWI in treatment planning for esophageal cancer may provide further information to assist with target delineation. Further studies are needed to determine if this technology will translate into meaningful differences in clinical outcome.

PurposeTo simulate and analyze the dosimetric differences of intraoperative radiotherapy (IORT) or pre-operative single-fraction stereotactic radiosurgery (SRS) in addition to post-operative external beam radiotherapy (EBRT) in Glioblastoma (GB).MethodsImaging series of previously treated patients with adjuvant radiochemotherapy were analyzed. For SRS target definition, pre-operative MRIs were co-registered to planning CT scans and a pre-operative T1-weighted gross target volume (GTV) plus a 2-mm planning target volume (PTV) were created. For IORT, a modified (m)GTV was expanded from the pre-operative volume, in order to mimic a round cavity as during IORT. Dose prescription was 20 Gy, homogeneously planned for SRS and calculated at the surface for IORT, to cover 99% and 90% of the volumes, respectively. For tumors > 2cm in maximum diameter, a 15 Gy dose was prescribed. Plan assessment was performed after calculating the 2-Gy equivalent doses (EQD2) for both boost modalities and including them into the EBRT plan. Main points of interest encompass differences in target coverage, brain volume receiving 12 Gy or more (V12), and doses to various organs-at-risk (OARs).ResultsSeventeen pre-delivered treatment plans were included in the study. The mean GTV was 21.72 cm3 (SD ± 19.36) and mGTV 29.64 cm3 (SD ± 25.64). The mean EBRT and SRS PTV were 254.09 (SD ± 80.0) and 36.20 cm3 (SD ± 31.48), respectively. Eight SRS plans were calculated to 15 Gy according to larger tumor sizes, while all IORT plans to 20 Gy. The mean EBRT D95 was 97.13% (SD ± 3.48) the SRS D99 99.91% (SD ± 0.35) and IORT D90 83.59% (SD ± 3.55). Accounting for only-boost approaches, the brain V12 was 49.68 cm3 (SD ± 26.70) and 16.94 cm3 (SD ± 13.33) (pmax of chiasma (p=0.01), left optic nerve (p=0.023), right (p=0.008) and left retina (pConclusionDose escalation for Glioblastoma using IORT results in lower OAR exposure as conventional SRS.

OBJECTIVE The authors aimed to investigate the dosimetric parameter and the minimally required dose associated with long-term control of sellar and parasellar tumors after Gamma Knife surgery (GKS) in children. METHODS A retrospective analysis was performed on pediatric patients younger than 19 years of age who were diagnosed with sellar and parasellar tumors and received GKS at the authors’ institution from 1998 to 2019. Cox proportional hazards regression analyses were used to investigate the dosimetric parameters associated with treatment outcome. The Kaplan-Meier method was used to analyze tumor control rates after GKS. RESULTS Overall, 37 patients with 40 sellar and parasellar tumors, including 22 craniopharyngiomas and 12 pituitary adenomas, had a mean follow-up of 85.8 months. The gross target volume was 0.05 cm3 to 15.28 cm3, and the mean marginal dose was 15.8 Gy (range 9.6–30.0 Gy). Ten patients experienced treatment failure at a mean of 28.0 ± 26.7 months. The actuarial 5- and 10-year tumor control rates were 79.0% and 69.8%, respectively. D98% was an independent predictive factor of tumor control (HR 0.846 [95% CI 0.749–0.956], p = 0.007), with a cutoff value of 11.5 Gy for the entire cohort and 10 Gy for the craniopharyngioma group. Visual deterioration occurred in 2 patients with the maximum point dose of 10.1 Gy and 10.6 Gy to the optic apparatus. CONCLUSIONS In pediatric patients, D98% was a reliable index of the minimum required dose for long-term control of sellar and parasellar tumors after GKS. The optimal D98% value for each tumor diagnosis needs to be elucidated in the future.

BackgroundClinically, many esophageal cancer patients who planned for radiation therapy have already undergone diagnostic Positron-emission tomography/computed tomography (PET/CT) imaging, but it remains unclear whether these imaging results can be used to delineate the gross target volume (GTV) of the primary tumor for thoracic esophageal cancer (EC).MethodsSeventy-two patients diagnosed with thoracic EC had undergone prior PET/CT for diagnosis and three-dimensional CT (3DCT) for simulation. The GTV3D was contoured on the 3DCT image without referencing the PET/CT image. The GTVPET-ref was contoured on the 3DCT image referencing the PET/CT image. The GTVPET-reg was contoured on the deformed registration image derived from 3DCT and PET/CT. Differences in the position, volume, length, conformity index (CI), and degree of inclusion (DI) among the target volumes were determined.ResultsThe centroid distance in the three directions between two different GTVs showed no significant difference (P > 0.05). No significant difference was found among the groups in the tumor volume (P > 0.05). The median DI values of the GTVPET-reg and GTVPET-ref in the GTV3D were 0.82 and 0.86, respectively (P = 0.006). The median CI values of the GTV3D in the GTVPET-reg and GTVPET-ref were 0.68 and 0.72, respectively (P = 0.006).ConclusionsPET/CT can be used to optimize the definition of the target volume in EC. However, no significant difference was found between the GTVs delineated based on visual referencing or deformable registration whether using the volume or position. So, in the absence of planning PET–CT images, it is also feasible to delineate the GTV of primary thoracic EC with reference to the diagnostic PET–CT image.

Radiotherapy is the main treatment method for nasopharynx cancer. Delineation of Gross Target Volume (GTV) from medical images is a prerequisite for radiotherapy. As manual delineation is time-consuming and laborious, automatic segmentation of GTV has a potential to improve the efficiency of this process. This work aims to automatically segment GTV of nasopharynx cancer from Computed Tomography (CT) images. However, it is challenged by the small target region, anisotropic resolution of clinical CT images, and the low contrast between the target region and surrounding soft tissues. To deal with these problems, we propose a 2.5D Convolutional Neural Network (CNN) to handle the different in-plane and through-plane resolutions. We also propose a spatial attention module to enable the network to focus on the small target, and use channel attention to further improve the segmentation performance. Moreover, we use a multi-scale sampling method for training so that the networks can learn features at different scales, which are combined with a multi-model ensemble method to improve the robustness of segmentation results. We also estimate the uncertainty of segmentation results based on our model ensemble, which is of great importance for indicating the reliability of automatic segmentation results for radiotherapy planning. Experiments with 2019 MICCAI StructSeg dataset showed that (1) Our proposed 2.5D network has a better performance on images with anisotropic resolution than the commonly used 3D networks. (2) Our attention mechanism can make the network pay more attention to the small GTV region and improve the segmentation accuracy. (3) The proposed multi-scale model ensemble achieves more robust results, and it can simultaneously obtain uncertainty information that can indicate potential mis-segmentations for better clinical decisions.

Radiotherapy plays an important role in the treatment of non-small cell lung cancer. Accurate segmentation of the gross target volume is very important for successful radiotherapy delivery. Deep learning techniques can obtain fast and accurate segmentation, which is independent of experts’ experience and saves time compared with manual delineation. In this paper, we introduce a modified version of ResNet and apply it to segment the gross target volume in computed tomography images of patients with non-small cell lung cancer. Normalization was applied to reduce the differences among images and data augmentation techniques were employed to further enrich the data of the training set. Two different residual convolutional blocks were used to efficiently extract the deep features of the computed tomography images, and the features from all levels of the ResNet were merged into a single output. This simple design achieved a fusion of deep semantic features and shallow appearance features to generate dense pixel outputs. The test loss tended to be stable after 50 training epochs, and the segmentation took 21 ms per computed tomography image. The average evaluation metrics were: Dice similarity coefficient, 0.73; Jaccard similarity coefficient, 0.68; true positive rate, 0.71; and false positive rate, 0.0012. Those results were better than those of U-Net, which was used as a benchmark. The modified ResNet directly extracted multi-scale context features from original input images. Thus, the proposed automatic segmentation method can quickly segment the gross target volume in non-small cell lung cancer cases and be applied to improve consistency in contouring.

Purpose To determine whether there are any changes in brain metastases or resection cavity volumes between planning magnetic resonance imaging (MRI) and radiosurgery (RS) treatment and whether these led to a change in management or alteration in the RS plan. Methods and Materials Patients undergoing RS for brain metastasis or tumor resection cavities had a standardized planning MRI (MRI-1) performed and a repeat verification MRI (MRI-2) 24 hours before RS. Any change in management, including replanning based on MRI-2, was recorded. Results Thirty-four patients with a total of 59 lesions (44 metastases and 15 tumor resection cavities) were assessed with a median time between MRI-1 and MRI-2 of 7 days. Seventeen patients (50%) required a change in management based on the changes seen on MRI-2. For patients with 7 days or less between scans, 41% (9 of 22) required a change in management; among patients with 8 days or more between scans, 78% (7 of 9) required a change in management. Per lesion, 32 out of 59 lesions required replanning, including 7 of 15 (47%) cavities and 25 of 44 (57%) metastases, with the most common reason (23 lesions) being an increase in gross target volume (tumor) or clinical target volume (tumor cavity). Conclusions Measurable changes occur in brain metastasis over a short amount of time, with a change in management required in 41% of patients with 7 days between MRI-1 and MRI-2 and in 78% of patients when there is a delay longer than 7 days. We therefore recommend that the time between planning MRI and RS treatment be as short as possible.

In this paper, we study the reliability of a novel deep learning framework for internal gross target volume (IGTV) delineation from 4-D computed tomography (4DCT), which is applied to patients with lung cancer treated by stereotactic body radiation therapy (SBRT). Seventy seven patients who underwent SBRT followed by 4DCT scans were incorporated in this retrospective study. The IGTV_DL was delineated using a novel deep machine learning algorithm with a linear exhaustive optimal combination framework. For the purpose of comparison, three other IGTVs based on common methods was also delineated. We compared the relative volume difference (RVI), matching index (MI), and encompassment index (EI) for the above IGTVs. Then, multiple parameter regression analysis was performed to assess the tumor volume and motion range as clinical influencing factors in the MI variation. The results demonstrated that the deep learning algorithm with linear exhaustive optimal combination framework has a higher probability of achieving optimal MI compared with other currently widely used methods. For patients after simple breathing training by keeping the respiratory frequency in 10 breath per minute (BPM), the four phase combinations of 0%, 30%, 50% and 90% can be considered as a potential solution for an optimal combination to synthesize IGTV in all respiration amplitudes.

Radiotherapy, particularly the target delineation of cancer based on scanned images, plays a key role in the planning of cancer treatment. Recently, diffusion-weighted magnetic resonance imaging (DW-MRI) has emerged as a prospective superior procedure compared with intensified computed tomography (CT) and positron emission tomography (PET) in the target delineation of cancer. However, the implication of DW-MRI in lung cancer, the leading cause of cancer-associated mortality worldwide, has not been extensively evaluated. In the present study, the gross target volumes of lung cancer masses delineated using the DW-MRI, CT and PET procedures were compared in a pairwise manner in a group of 27 lung cancer patients accompanied with atelectasis of various levels. The data showed that compared with CT and PET procedures, DW-MRI has a more precise delineation of lung cancer while exhibiting higher reproducibility. Together with the fact that it is non-invasive and cost-effective, these data demonstrate the great application potential of the DW-MRI procedure in cancer precision radiotherapy.

Purpose: PET/CT is a standard medical imaging used in the delineation of gross tumor volume (GTV) in case of radiation therapy for lung tumors. However, PET/CT could present some limitations such as resolution and standardized uptake value threshold. Moreover, chest MRI has shown good potential in diagnosis for thoracic oncology. Therefore, we investigated the influence of chest MRI on inter-observer variability of GTV delineation. Methods and Materials: Five observers contoured the GTV on CT for 14 poorly defined lung tumors during three contouring phases based on true daily clinical routine and acquisition: CT phase, with only CT images; PET phase, with PET/CT; and MRI phase, with both PET/CT and MRI. Observers waited at least 1 week between each phases to decrease memory bias. Contours were compared using descriptive statistics of volume, coefficient of variation (COV), and Dice similarity coefficient (DSC). Results: MRI phase volumes (median 4.8 cm3) were significantly smaller than PET phase volumes (median 6.4 cm3, p = 0.015), but not different from CT phase volumes (median 5.7 cm3, p = 0.30). The mean COV was improved for the MRI phase (0.38) compared to the CT (0.58, p = 0.024) and PET (0.53, p = 0.060) phases. The mean DSC of the MRI phase (0.67) was superior to those of the CT and PET phases (0.56 and 0.60, respectively; p < 0.001 for both). Conclusions: The addition of chest MRI seems to decrease inter-observer variability of GTV delineation for poorly defined lung tumors compared to PET/CT alone and should be explored in further prospective studies.

Background: To determine optimum conditions for diagnosis of nasopharyngeal carcinoma, we established VX2 rabbit model to delineate gross target volume (GTV) in different imaging methods. Methods: The orthotopic nasopharyngeal carcinoma (NPC) was established in sixteen New Zealand rabbits. After 7-days inoculation, the rabbits were examined by CT scanning and then sacrificed for pathological examination. To achieve best delineation, different GTVs of CT, MRI, 18F-FDG PET/CT, and 18F-FLT PET/CT images were correlated with pathological GTV (GTVp). Findings: We found a 45% and 60% of the maximum standardized uptake value (SUVmax) as the optimal SUV threshold for the target volume of NPC in 18F-FDG PET/CT and 18F-FLT PET/CT images, respectively (GTVFDG45% and GTVFLT60%). Moreover, the GTVMRI and GTVCT were significantly higher than the GTVp (P ≤ 0.05), while the GTVFDG45% and especially GTVFLT60% were similar to the GTVp (R = 0.892 and R = 0.902, respectively; P ≤ 0.001). Interpretation: Notably, the results suggested that 18F-FLT PET/CT could reflect the tumor boundaries more accurately than 18F-FDG PET/CT, MRI and CT, which makes 18F-FLT PET-CT more advantageous for the clinical delineation of the target volume in NPC. Funding Statement: This research received financial support from the Scientific Research Project Fund of the Affiliated Hospital of Southwest Medical University (2013-60). Declaration of Interests: The authors have no financial interests related to the material in the manuscript. The authors declare that there are no conflicts of interest. Ethics Approval Statement: This study was approved by an independent ethics committee/institutional review board at Department of Oncology, Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China. All animal-related procedures and protocol were approved under the guidelines of the National Institutes of Health (NIH) Animal Care (1995, USA) and the local Ethics Committee guidelines by Institutional Animal Care and Treatment Committee of Southwest Medical University (Luzhou, China).

Differences in gross target volume (GTV) and central point positions among moving lung cancer models constructed by CT scanning at different frequencies were compared, in order to explore the effect of different respiratory frequencies on the GTV constructions in moving lung tumors. Eight models in different shapes and sizes were established to stimulate lung tumors. The three-dimensional computed tomography (3DCT) and four-dimensional computed tomography (4DCT) scanning were performed at 10, 15 and 20 times/min in different models. Differences in GTV volumes and central point positions at different motion frequencies were compared by means of GTV3Ds (GTV3D-10, GTV3D-15, GTV3D-20) and IGTV4Ds (IGTV4D-10, IGTV4D-15, IGTV4D-20). Volumes of GTV3D-10, GTV3D-15, GTV3D-20 were 12.41±14.26, 10.38±11.18 and 12.50±15.23 cm3 respectively (P=0.687). Central point coordinates in the x-axis direction were −8.16±96.21, −8.57±96.08 and −8.56±95.73 respectively (P=0.968). Central point coordinates in the y-axis direction were 108.22±25.03, 110.41±22.47 and 109.04±24.24 (P=0.028). Central point coordinates in the z-axis direction were 65.19±13.68, 65.43±13.40 and 65.38±13.17 (P=0.902). The difference was significant in the y-axis direction (P=0.028). Volumes of IGTV4D-10, IGTV4D-15, IGTV4D-20 were 17.78±19.42, 17.43±19.56 and 17.44±18.80 cm3 (P=0.417). Central point coordinates in the x-axis direction were −7.73±95.93, −7.86±95.56 and −7.92±95.14 (P=0.325). Central point coordinates in the y-axis direction were 109.41±24.54, 109.60±24.13 and 109.16±24.28 (P=0.525). Central point coordinates in the z-axis direction were 65.52±13.31, 65.59±13.39 and 65.51±13.34 (P=0.093). However, the central point position of GTV in the head and foot direction by 3DCT scanning was severely affected by the respiratory frequency.

Purpose: To investigate the difference in sparing normal livertissue between 4D‐CT and active breathing coordinator (ABC) in the radiotherapy of Hepatocellular carcinoma(HCC) applying RapidArc. Methods: Ten patients with HCC underwent 3D‐CT at end inspiration hold(EIH) associated with active breathing coordinator(ABC) ,and 4D‐CT scan. The 4D‐CT images were sorted in to 10 serious CTimages according respiratory phase. Gross tumor volumes(GTVs) were manually contoured on different CTimages. The individual internal gross target volume(IGTV) was obtained from 10 GTVs of 4D‐CT images. Plan target volumes (PTVs) were obtained based on IGTV and GTVEIH. PTV1 was obtained from IGTV plus 5 mm margins isotropically, and PTV2 was obtained from GTVEIH using 8 mm margins isotropically. RapidArc plans were designed on PTV1 and PTV2, for PTV1 RapidArc plans with one single whole arc were applied and for PTV2 three 135°arcs, and name RapidArc1 and RapidArc2. Dosimetric differences were compared. Results: There were no significant difference in conformity index (0.93±0.05 Vs 0.93±0.03), homogeneity index(1.08±0.01 Vs 1.08±0.01) , the Dl%(54.44±0.36 Gy Vs54.68±0.47 Gy) and D99%(49.18±0.48Gy Vs 49.00±0.34 Gy) between RapidArc1 and RapidArc2(P>0.05). There were no significant differences in the mean dose(8.23±1.5Gy Vs 7.63±3.00Gy),V5(46.64±19.31Vs43.29±19.94), V10(28.73±11.54 Vs 28.23±12.37), V15(17.87±6.61 Vs 18.20±7.55), V20(11.62±4.39 Vs 11.83±4.58), V25(7.71±2.91Vs 7.58±2.79),V30(5.14±2.01Vs5.05±1.79), 35(3.41±1.35Vs 3.35±1.21) and V40(2.12±0.86Vs2.06±0.75) between RapidArc1 and RapidArc2 (P>0.05). Conclusions: The RapidArc plans with three 135°arcs associated could achieve similar dose delivery as the plans with single whole arc, and 4D‐CT and ABC could play similar role in sparing normal livertissue assuring the accuracy of target volume in radiotherapy of HCC.

To achieve consistent target delineation in radiotherapy for hepatocellular carcinoma (HCC), image registration between simulation CT and diagnostic MRI was explored. Twenty patients with advanced HCC were included. The median interval between MRI and CT was 11 days. CT was obtained with shallow free breathing and MRI at exhale phase. On each CT and MRI, the liver and the gross target volume (GTV) were drawn. A rigid image registration was taken according to point information of vascular bifurcation (Method[A]) and pixel information of volume of interest only including the periphery of the liver (Method[B]) and manually drawn liver (Method[C]). In nine cases with an indefinite GTV on CT, a virtual sphere was generated at the epicenter of the GTV. The GTV from CT (V GTV [CT]) and MRI (V GTV [MR]) and the expanded GTV from MRI (V +GTV [MR]) considering geometrical registration error were defined. The underestimation (uncovered V[CT] by V[MR]) and the overestimation (excessive V[MR] by V[CT]) were calculated. Through a paired T -test, the difference between image registration techniques was analyzed. For method[A], the underestimation rates of V GTV [MR] and V +GTV [MR] were 16.4 ± 8.9% and 3.2 ± 3.7%, and the overestimation rates were 16.6 ± 8.7% and 28.4 ± 10.3%, respectively. For V GTV [MR] and V +GTV [MR], the underestimation rates and overestimation rates of method[A] were better than method[C]. The underestimation rates and overestimation rates of the V GTV [MR] were better in method[B] than method[C]. By image registration and additional margin, about 97% of HCC could be covered. Method[A] or method[B] could be recommended according to physician preference.

127 Background: To determine the optimum conditions for diagnosis of nasopharyngeal carcinoma, we established VX2 rabbit model to delineate gross target volume (GTV) in different imaging methods. Methods:The orthotopic nasopharyngeal carcinoma (NPC) was established in sixteen New Zealand rabbits. After 7-days inoculation, the rabbits were examined by CT scanning and then sacrificed for pathological examination. To achieve the best delineation, different GTVs of CT, MRI, 18F-FDG PET/CT, and 18F-FLT PET/CT images were correlated with pathological GTV (GTVp). Results: We found 45% and 60% of the maximum standardized uptake value (SUVmax) as the optimal SUV threshold for the target volume of NPC in 18F-FDG PET/CT and 18F-FLT PET/CT images, respectively (GTVFDG45% and GTVFLT60%). Moreover, the GTVMRI and GTVCT were significantly higher than the GTVp ( P ≤ 0.05), while the GTVFDG45% and especially GTVFLT60% were similar to the GTVp ( R = 0.892 and R = 0.902, respectively; P ≤ 0.001). Conclusions: Notably, the results suggested that 18F-FLT PET/CT could reflect the tumor boundaries more accurately than 18F-FDG PET/CT, MRI and CT, which makes 18F-FLT PET-CT more advantageous for the clinical delineation of the target volume in NPC. Keywords: Nasopharyngeal carcinoma; Gross tumor volume; Magnetic resonance imaging, Computed tomography; 18F-FLT PET/CT; 18F-FDG PET/CT

The background of this study is to evaluate 3D dose distribution in organs at risk (OARs). The sample of the study consists of 300 patients; with age-range mean and standard deviation (35 ± 2.32 respectively). The CT simulator was used to collect data to delineate pituitary adenoma including growth target volume (GTV) and planning target volume (PTV 95%) as an isodose line for treatment protocol in order to obtain dose distribution of 3D dose coverage to the target while sparing organs at risks. The main results of this study were, 3D dose distribution is safe, because it confines the dose to gross target volume only, while sparing escalating dose to the organ at risks (OARs), the average dose reaching the organs at risks during the pituitary adenoma to the adjacent critical organs are such as: in temporal lobe is 1.14 Gy, in eye is 0.86 Gy, and in optic chiasm is 0.95 Gy. Therefore, it is concluded that the 3D dose distribution in pituitary adenoma treatment reduces an unnecessary radiation to critical organs. Thus, new technique needs to be developed to halt an unnecessary dose reaching organs at risks during treatment.

The purpose of the study is to evaluate the two dimensional dose distribution techniques in pituitary adenoma patient treatment in order to provide 2D dose coverage to the target volume while sparing organs at risk (OARs). The CT simulator was used to radiograph 300 patients of pituitary adenomas to conform 2D dose distribution planning inside the tumour bed , and its structures were delineated; including gross target volume (GTV), clinical target volume (CTV), and planning target volume (PTV)), as well as organs at risks (OARs) . Dose distribution analysis was edited to provide 2D dose coverage to the target while sparing organs at risk. The main results of the study were, 2D dose distribution plans increases the unnecessary dose to the critical organs according to their geographical location from the pituitary adenoma site, and the present study , concludes that when the tumour dose increases from 45 to 55 Gy there is a linear proportional increment of dose to the organs at risks, and when the dose is about 60 Gy in 2D, the increment of unnecessary dose to temporal lobe is 0.31 Gy, and to eye is0.34Gy, and to optic chiasm is 0.42 Gy respectively .New techniques, which will lessen the unnecessary dose to OARs, needed to be developed .

Background Gross target volume of primary tumor (GTV-P) is very important for the prognosis prediction of patients with nasopharyngeal carcinoma (NPC), but it is unknown whether the same is true for locally advanced NPC patients treated with intensity-modulated radiotherapy (IMRT). This study aimed to clarify the prognostic value of tumor volume for patient with locally advanced NPC receiving IMRT and to find a suitable cut-off value of GTV-P for prognosis prediction. Methods Clinical data of 358 patients with locally advanced NPC who received IMRT were reviewed. Receiver operating characteristic (ROC) curves were used to identify the cut-off values of GTV-P for the prediction of different endpoints [overall survival (OS), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), and disease-free survival (DFS)] and to test the prognostic value of GTV-P when compared with that of the American Joint Committee on Cancer T staging system. Results The 358 patients with locally advanced NPC were divided into two groups by the cut-off value of GTV-P as determined using ROC curves: 219 (61.2%) patients with GTV-P ≤46.4 mL and 139 (38.8%) with GTV-P >46.4 mL. The 3-year OS, LRFS, DMFS, and DFS rates were all higher in patients with GTV-P ≤46.4 mL than in those with GTV-P > 46.4 mL (all P 46.4 mL was an independent unfavorable prognostic factor for patient survival. The ROC curve verified that the predictive ability of GTV-P was superior to that of T category (P 46.4 mL is an independent unfavorable prognostic indicator for survival after IMRT, with a prognostic value superior to that of T category.

Background The purpose of this study was to assess the efficacy and toxicities of reirradiation using intensity-modulated radiotherapy (IMRT) in patients with locally advanced recurrent nasopharyngeal carcinoma (NPC). Methods Thirty-eight patients with consecutive rT3 to rT4 NPC treated between 2005 and 2013 were retrospectively analyzed. Results The 3-year overall survival (OS), progression-free survival (PFS), and local control rate were 47.2%, 17.5%, and 44.3%, respectively. Gross target volume (GTV) D95, GTV D50, and age were all important prognostic factors for OS and PFS, but only GTV D95 was an important determinant for local control. A total of 73.7% patients experienced ≥1 grade 3 late toxicities and 3 patients died of massive epistaxis. Temporal lobe necrosis (TLN) developed sooner with a higher total biological equivalent dose. Conclusion Adequate tumor dose coverage was important for treating rT3 to rT4 NPC. Although late complications were common, treatment-related mortality was solely vascular in nature. Dose constraints of neurologic structures for reirradiation should be revised with the latest information on late toxicities. © 2016 Wiley Periodicals, Inc. Head Neck, 2016

The aim of this paper is to compare the dosimetric difference between intensity-modulated arc therapy (IMAT) and conventional intensity-modulated radiation therapy (IMRT) for radiotherapy of nasopharyngeal carcinoma (NPC) using simultaneously integrated boost (SIB) protocol. Ten patients with nasopharyngeal carcinoma underwent SIB protocol were retrospectively studied. The plan target volume (PTV) of NPC contained nasopharynx gross target volume and the positive neck lymph nodes, PTV1 contained the high-risk sites of microscopic extension and the whole nasopharynx and PTV2 contained the low-risk sites. The prescription dose of PTV was 66 Gy/30 fractions, and for PTV1 60 Gy/30 fractions and for PTV2 54 Gy/30 fractions. IMAT (two 358° arcs) and IMRT (7 fields) plans were designed for each patients using SIB strategies. The monitor unit (MU), treatment time (T) and dosimetric difference between IMRT and IMAT were compared. IMAT can achieve better conformal index (CI) than IMRT ( P < 0.05) for all PTVs, while no significant difference were found in homogeneity index (HI) ( P > 0.05). There's no significant difference found in radiation dose of brain stem, lenses and parotids, while the maximum dose of spinal cord of IMAT was higher than IMRT ( P < 0.05). The monitor unit of IMRT (1308 ± 213) was more than IMAT (606 ± 96) ( P < 0.05), while the treatment time of IMRT (540 ± 160S) was more than IMAT (160 ± 10S). This study shows that IMAT using SIB strategies for NPC radiotherapy can achieve similar target coverage with better conformity with less MU and delivery time comparing to IMRT.

We investigated the dosimetric differences among volumetric-modulated arc radiotherapy (RapidArc, RA) plans designed for various target volumes in hepatocellular carcinoma (HCC). Ten HCC patients underwent 3D-CT scanning at free breathing (FB), 3D-CT at end inspiration hold (EIH) assisted by an Active Breathing Coordinator (ABC), and 4D-CT scanning. Gross tumor volumes (GTVs) were manually contoured on CT images. The individualized internal gross target volume (IGTV(1)) was obtained from 10 GTVs from 4D-CT images. Tumor individual margins were measured from GTV(FB) to IGTV(1). The IGTV(2) was obtained from GTV(FB) by applying individual margins. Four planning target volumes (PTV(1-4)) were obtained from IGTV(1), IGTV(2), GTV(FB), and GTV(EIH), respectively. An RA plan was designed for each of the PTVs (RA(1-4)). One 358° arc was used for PTVs(1-3), while three 135° arcs were used for PTV(4). It was found that PTV(2) and PTV(3) were larger than PTV(1) and PTV(4). The mean values of PTV(3)/PTV(1) and PTV(3)/PTV(4) were 2.5 and 1.9, respectively. The individual margins in the X, Y and Z axial directions varied greatly among these patients. There were no significant differences in the conformal index or homogeneity index among the four RA plans. RA(1) and RA(4) significantly reduced the radiation dose of normal liver tissue compared with RA(2) and RA(3) (P < 0.01). There were no significant differences between the radiation doses of the stomach and duodenum. RapidArc combined with 4D-CT or ABC technology is a promising method in radiotherapy of HCC, and accurately targeted the tumor volume while sparing more normal liver tissue.

Purpose: To examine the impact of dose on local failure (LF) rates in the re-treatment of recurrent paraspinal metastases with image-guided intensity-modulated radiotherapy (IG-IMRT). Methods and Materials: The records of patients with in-field recurrence after previous spine radiation (median dose, 30 Gy) who received salvage IG-IMRT with either five 4-Gy (20-Gy group, n = 42) or five 6-Gy (30-Gy group, n = 55) daily fractions between January 2003 and August 2008 were reviewed. Institutional practice was 20 Gy before April 2006, when it changed to 30 Gy. A total of 47 cases (48%) were treated adjuvantly, after surgery to decompress epidural disease. LF after IG-IMRT was defined radiographically. Results: The median follow-up was 12.1 months (range, 0.2-63.6 months). The 1-year cumulative incidences of LF after 20 Gy and 30 Gy IG-IMRT were 45% and 26%, respectively (p = 0.04). Of all treatment characteristics examined (20-Gy vs. 30-Gy dose group, dose to 95% of the planned and gross target volume, tumor size, histology, receipt of surgery, and interval between first and second radiation), only dose group had a significant impact on actuarial LF incidence (p = 0.04; unadjusted HR, 0.51; 95% CI, 0.27-0.96). There was no incidence of myelopathy. Conclusions: Amore » significant decrease in LF after IG-IMRT with five 6-Gy fractions compared with five 4-Gy fractions was observed without increased risk of myelopathy. Until prospective data comparing stereotactic hypofractionated and single-fraction regimens become available, when reirradiating recurrent paraspinal metastases with IG-IMRT, administration of five 6-Gy daily fractions is reasonable.« less

Multileaf collimator (MLC)-assisted intensity modulated radiotherapy (IMRT) has greatly improved the target coverage and avoidance of organs at risk (OAR) for the treatment of nasopharyngeal carcinoma; however, its implementation is also constrained by the features of the MLC. Nasopharyngeal carcinoma tends to have a large gross target volume (GTV) and clinical target volume (CTV) due to its biological characteristics. More than one isocenter may be needed when small MLCs (i.e., BrainLAB M3, whose largest field is 10 x 10 cm(2)) are used to treat the nasopharyngeal carcinoma. The BrainLAB IMRT system was used to evaluate the effectiveness of a multi-isocenter IMRT plan for treating nasopharyngeal cancers. Dose coverage of GTVs and CTVs were compared among IMRT plans with 1, 2 and 3 isocenters, as were dose objectives for OARs including brainstem, cord, and parotids. The dosimetric variation and the delivery time were also measured with a phantom. IMRT plans with more than 1 isocenter achieved a better dose coverage, homogeneity, and conformity on GTVs and CTVs; however, with risk of higher doses given to OARs. In most cases, one can generate satisfactory IMRT plans using the 2-isocenter IMRT planning strategy. Two-isocenter planning strategy may be a suitable compromise when more isocenters are needed.

Magnetic resonance imaging (MRI)-based intracavitary brachytherapy offers several advantages over computed tomography (CT)-based brachytherapy, but many centers are unable to offer it at the time of brachytherapy because of logistic and/or financial considerations. We have implemented a method of integrating MRI into a CT-guided, high-dose-rate intracavitary brachytherapy workflow in clinics that do not have immediately available MRI capability.At our institution, patients receiving high-dose-rate intracavitary brachytherapy as a component of the definitive treatment of cervical cancer have a Smit sleeve placed during the first brachytherapy fraction in a dedicated suite with in-room CT-on-rails. After the first fraction of brachytherapy, an MRI is obtained with the Smit sleeve, but no applicator, in place. For each subsequent fraction, CT scans are coregistered to the MRI scan by the Smit sleeve. The gross target volume is defined by MRI and overlaid on the CT images for each brachytherapy treatment for dose optimization.This MRI-integrated workflow adds5 minutes to the brachytherapy session for image fusion. Our initial clinical experience suggests that this approach is feasible and results in target volume reductions compared with CT-alone brachytherapy.Our proposed combination MRI and/or CT workflow is a feasible compromise to preserve an efficient workflow while integrating MRI target delineation, and it provides many of the advantages of both MRI- and CT-based brachytherapy. The future collection and analysis of clinical data will serve to compare the proposed approach to non-MRI containing techniques.

The purpose of this work is to investigate the effect of dose-calculation accuracy on head and neck (H&N) intensity modulated radiation therapy(IMRT) plans by determining the systematic dose-prediction and optimization-convergence errors (DPEs and OCEs), using a superposition/convolution (SC) algorithm. Ten patients with locally advanced H&N squamous cell carcinoma who were treated with simultaneous integrated boost IMRT were selected for this study. The targets consisted of gross target volume (GTV), clinical target volume (CTV), and nodal target volumes (CTV nodes). The critical structures included spinal cord, parotid glands, and brainstem. For all patients, three IMRT plans were created: A: an SC optimized plan ( SC opt ) , B: an SC opt plan recalculated with Monte Carlo [ MC ( SC opt ) ] , and C: an MC optimized plan ( MC opt ) . For each structure, DPEs and OCEs were estimated as DPE SC = D B − D A and OCE SC = D C − D B where A, B, and C stand for the three different optimized plans as defined above. Deliverable optimization was used for all plans, that is, a leaf-sequencing step was incorporated into the optimization loop at each iteration. The range of DPE SC in the GTV D 98 varied from − 1.9 % to − 4.9 % , while the OCE SC ranged from 0.9% to 7.0%. The DPE SC in the contralateral parotid D 50 reached 8.2%, while the OCE SC in the contralateral parotid D 50 varied from 0.91% to 6.99%. The DPE SC in cord D 2 reached − 3.0 % , while the OCE SC reached to − 7.0 % . The magnitude of the DPE SC and OCE SC differences demonstrate the importance of using the most accurate available algorithm in the deliverable IMRToptimization process, especially for the estimation of normal structure doses.

We investigated the changes in dose distribution of three-dimensional conformal radiotherapy (3D CRT) during lung tumor treatment. Ten patients with non-small cell lung cancer who had undergone planning for radical radiotherapy were selected for study. Computed tomography (CT) examination was performed at two time intervals during the course of conformal radiotherapy: t0 Gy at the time of planning and t40 Gy at 40 Gy of treatment. We transferred all the planed beam data at t0 Gy to each t40 Gy CT image. The isodose distribution was recalculated at time t40 Gy for the same beam characteristics. Variations in volumes and dose-volume histograms (DVHs) were analyzed and compared for lung, gross target volume (GTV), and planning target volumes (PTV) between t0 Gy and t40 Gy. A paired t-test was performed to compare the DVH between t0 Gy and t40 Gy. The mean minimum doses for t40 Gy GTV, and PTV were lower than t0 Gy. However, there was no significant difference between t0 Gy and t40 Gy (p=0.493, 0.378, respectively). There was a patient whose minimum doses of GTV and PTV were decreased and who had notable improvement of lobar atelectasis after 40 Gy of radiotherapy. Comparison of the percent volume of received dose exceeding 20 Gy (V20) and the mean dose for the total lung revealed that t40 Gy was larger than t0 Gy (p=0.013, 0.012). Incorporation of the time factor into 3D treatment planning is mandatory for frequent reiteration of treatment planning during treatment periods. Clearly, more work in this area should be considered.

BACKGROUND: Radiation therapy is an available treatment modality for pituitary adenoma. In particular, it is effective for the case unable to be removed with surgery or repeating recurrence. However, hypopituitarism and optic nerve injury associated with radiation therapy become a problem. Novalis® (Brain Lab) is an equipment of radiation to establish the detailed irradiation area, fractionated stereotactic radiotherapy (fSRT) and intensity-modulated radiation therapy (IMRT). Retrospectively, we review local control and morbidity following fSRT with Novalis in pituitary adenoma. PATIENTS AND METHODS: Between 2007 and 2012, 29 patients with pituitary adenoma (9 functioning, 20 non-functioning) received fSRT with Novalis in our institute. Total radiation dose was 50.4-54Gy (1.8 Gy per fraction) and prescribed to the gross target volume + 2 mm. The effectiveness of fSRT was evaluated by tumor volume and clinical symptoms on pre- fSRT, and every 1-year. RESULTS: The median follow-up time was 59.1 months (20 to 83 months). Tumor regrowth was observed in 2 cases. Progression free survival rate was 93%. New visual field deficit was observed in 1 case, and new pituitary dysfunction were not observed in all patients. CONCLUSION: fSRT with Novalis is safe and effective in the treatment for pituitary adenoma. Although follow-up time is short, any problematic complications were not observed. In the future, fSRT is expected to make for safe and effective treatment in pituitary adenoma impossible to cure surgically.

The aims of this study were to evaluate the volume and dosimetric variations during IMRT for locally advanced NPC and to identify the benefits of a two-phase adaptive IMRT method. Twenty patients with locally advanced NPC having received IMRT treatment were included. Each patient had both an initial planning CT (CT-1) and a repeated CT scan (CT-2) after treatment at a dose of 40 Gy. Three IMRT planning scenarios were compared: (1) the initial plan on the CT-1 (plan-1); (2) the hybrid plan recalculated the initial plan on the CT-2 (plan-2); (3) the replan generated on the CT-2 being used to complete the course of IMRT (plan-3). The mean gross target volume and mean volumes of the positive neck lymph nodes, high-risk clinical target volume, and the left and right parotid glands significantly decreased by 30.2%, 45.1%, 21.1%, 14.7% and 18.2%, respectively on the CT-2. Comparing plan-2 with plan-1, the dose coverage of the targets remained unchanged, whereas the dose delivered to the parotid glands and spinal cord increased significantly. These patients with locally advanced NPC might benefit from replanning because of the sparing of the parotid glands and spinal cord.

While the accuracy of patient setup itself has been well documented in stereotactic radiosurgery (SRS), the amount of rotational patient setup errors needed to impact this accuracy is not well defined. The purpose of this study is to explore potential rotational setup error thresholds for SRS treatments of brain metastases. Two groups were analyzed in this study: Group A consisted of twenty cases where a single brain metastasis treatment was planned using a single isocenter located within the tumor; Group B consisted of five cases where two brain metastases were planned using a single isocenter located between the tumors. All twenty-five cases underwent simulations for rotations around the treatment isocenter of ±1°, ±3°, ±5°, and ±7°. In addition, cases in Group B included simulations of ±0.5° and ±2°. The percent of the gross target volume (GTV) and planning target volume (PTV) that received the prescription dose (V p) was compared between the original plans and rotation simulations to determine what degree of rotations will cause V p loss greater than 0% and 1% respectively. In Group A, the average loss in V p for the GTV and PTV was 0% and below 1% respectively for rotations below ±3°. Using the Spearman correlation coefficient, V p loss in Group A showed very weak to weak correlation with physical characteristic of the tumor. In Group B, the average loss in V p for the GTV and PTV was 0% and below 1% respectively for rotations of ±0.5°. V p loss as a result of rotations showed very strong correlation with increasing tumor distance from treatment isocenter. Our study suggests that a patient rotational setup error threshold of ±2° around all axes for isocentric treatments is conservative. For nonisocentric treatments, the rotational setup error threshold may need to be as low as or lower than ±0.5° for tumors that are far from the treatment isocenter.

Purpose: In recent years Multi-Criteria Optimization (MCO) has become commercially available as a potential optimization method for intensity modulated and volumetric arc therapies (IMRT and VMAT). The purpose of our work is to develop a universal set of objectives and constraints to generate prostate cancer MCO plans with VMAT and evaluate them using biological metrics. Methods: We randomly selected ten prostate plans (two-arc VMAT) for patients with intermediate risk prostate cancer prescribed 75.6–79.2Gy to the prostate and seminal vesicles. We compared the plan scores to our clinical plans generated with standard IMRT optimization techniques. The planning target volumes (PTV) were 5–10 mm set-up margin expansion of the gross target volume. Using the same two arcs we generated MCO plans with a standard set of constraints and objectives using Raystation v4.5. The dose-volume histograms (DVH) for the (PTV), rectum and bladder were exported and used to calculate tumor control probability (TCP) and the complication-free tumor control probability P+ using biological models from the literature. We classified the plans by their level of difficulty based on the rectum-PTV overlap and develop MCO plans with similar levels of conformality as the clinical plans. Results: The P+ values of the MCO plans had an average of 86.4%±2.3% and were equivalent to the clinical plans (P+ average of 85.0%±2.1%, p-value=0.33). The MCO NTCP values for the rectum ranged from 0.7% to 20% and were highly correlated with rectum-PTV overlap. NTCP values for the bladder were less than 1% for all MCO plans. Conclusion: MCO VMAT prostate plans obtained with standardized objectives and constraints generate biologically equivalent plans to the clinical plans generated with standard optimization techniques.

This paper expanded two-dimensional optical flow registration method to three- dimensional optical flow method (3D-OFM) to deform the four-dimensional computed tomography (4D CT) images. 4D CT can investigate the effect of breathing motion to the liver tumors and track the “trajectory” of the tumors. This algorithm was applied to the fully automated registration of 4D CT data for hepatocellular carcinoma patients. According to the respiratory phase, 4D CT data was segmented into 10-series CT images which were named CT0, CT10…CT90, and CT0 is at end inspiration and CT50 is at end expiration. In particular, The iodipin was used to help define the gross target volume of HCC to improve the image contrast. In addition, The iodipin also used to improve the registration method and verify the performance of registration method as the markers. We chose the end-exhale CT as the reference image. To verify the registration performance of this method, we qualitatively compared the subtractions of floating images and reference image and the iodipin deposition regions before and after registered, and we quantificationally computed the multi-information between floating images and reference image of 8 patients. The improving proportion of multi-information between end-exhale CT and in-exhale CT is from 1.71% to 4.17%.

Gross Target Volume as the Predictor for the Overall Survival for Stage III Non-Small Cell Lung Cancer Locally Advanced Non-Small Cell Lung Cancer J. SUN, X. Zhang, J.Y. Chang, D. Gomez, S. Jiang, P. Wang, Z. Yuan, l. Zhao, L. Wang, Z. Hui, and Z. Liao; M.D. Anderson Cancer Center, Houston, TX, Tianjin Cancer Hospital and Institute, Tianjin, China, Chinese Academy of Medical Sciences, Beijing, China

Purpose Differences in the delineation of the gross target volume (GTV) and planning target volume (PTV) in patients with non-small-cell lung cancer are considerable. The focus of this work is on the analysis of observer-related reasons while controlling for other variables. Methods In three consecutive patients, eighteen physicians from fourteen different departments delineated the GTV and PTV in CT-slices using a detailed instruction for target delineation. Differences in the volumes, the delineated anatomic lymph node compartments and differences in every delineated pixel of the contoured volumes in the CT-slices (pixel-by-pixel-analysis) were evaluated for different groups: ten radiation oncologists from ten departments (ROs), four haematologic oncologists and chest physicians from four departments (HOs) and five radiation oncologists from one department (RO1D). Results Agreement (overlap ⩾ 70% of the contoured pixels) for the GTV and PTV delineation was found in 16.3% and 23.7% (ROs), 30.4% and 38.6% (HOs) and 32.8% and 35.9% (RO1D), respectively. Conclusion A large interobserver variability in the PTV and much more in the GTV delineation were observed in spite of a detailed instruction for delineation. The variability was smallest for group ROID where due to repeated discussions and uniform teaching a better agreement was achieved.

Purpose To develop a technique using exclusively magnetic resonance imaging (MRI) to perform dwell position identification, targets and organs at risk delineation, and to apply inverse planning dose optimization to high-dose-rate brachytherapy for cervical cancer. Methods and materials We included 15 consecutive women treated with high-dose-rate (HDR) brachytherapy for cervical cancer. All patients underwent MRI after placement of tandem and ring applicator containing a gadodiamide-filled dummy marker. This technique allowed direct visualization of the source pathway and precise definition of the intra-applicator source positions. For each patient, we delineated gross target volume (GTV), high-risk clinical target volume (HR-CTV), and organs at risk on MRI, according to the European Gynecological GEC-ESTRO Working Group definitions. We performed inverse planning simulated annealing (IPSA) and analyzed the dose–volume histograms with the following endpoints: D90, D100, and V100 for GTV and HR-CTV; D0.1 cc, D1 cc, D2 cc for bladder, rectum, and bowel; and dose at Point A. Results The intra-applicator source pathway was easily visualized on MRI using the gadodiamide-filled marker. IPSA provided excellent target coverage. The mean D90 and V100 for HR-CTV were 103 ± 5% and 92 ± 3%, respectively. IPSA provided excellent bladder sparing. D1 cc and D2 cc of bladder were 73 ± 10% and 67 ± 10%, respectively. Conclusions We developed a novel technique that allows direct visualization of the intra-applicator source pathway on MRI. Using this technique, we successfully performed inverse planning directly from MRI.

Purpose: This work provides a proof-of-concept study for real-time 4D dose reconstruction on 4DCT lung data treated with MLC tracking and its impact on the size of target margins. Methods: We have implemented online dose reconstruction by connecting our research platform for dynamic dose delivery to an Agility MLC at an Elekta Synergy linac with our in-house treatment planning software (TPS). Actual MLC apertures and (simulated) target positions are reported to the TPS every 40ms and 33ms respectively. The dose is then accumulated in real-time by utilization of pre-calculated dose-influence matrices based on a collapsed-cone algorithm. To investigate the impact of a potentially reducible safety margin we have created and delivered treatment plans designed for a conventional internal target volume (ITV)+5mm and for a tracking scenario of a lung patient. Both were planned to meet the criteria of RTOG 1021 (3-Fx, 9-beam). For the tracking plan, a maximum target volume (MTV)+5mm was established by delineating the gross target volume (GTV) on every 4DCT phase. These were rigidly aligned to the chosen reference phase, resulting in a unified maximum GTV to which a 5mm isotropic margin was added. The dose accumulation on a reference phase of the 4DCT (2×2×2mm3) was accomplished by the use of 3D deformation vector fields. Results: D95 for GTV on the reference phase was 98% of the RTOG prescribed dose for both the ITV+5mm plan and the MTV+5mm plan with tracking. V20 for ipsilateral lung and mean chest wall dose decreased by 10% and 12% respectively for the tracking scenario. Dose calculation and accumulation were performed in

Purpose: We introduce a new method combined with the deformable image registration (DIR) and regions-of-interest mapping (ROIM) technique to accurately calculate dose on daily CBCT for esophageal cancer. Methods: Patients suffered from esophageal cancer were enrolled in the study. Prescription was set to 66 Gy/30 F and 54 Gy/30 F to the primary tumor (PTV66) and subclinical disease (PTV54) . Planning CT (pCT) were segmented into 8 substructures in terms of their differences in physical density, such as gross target volume (GTV), venae cava superior (SVC), aorta, heart, spinal cord, lung, muscle and bones. The pCT and its substructures were transferred to the MIM software to readout their mean HU values. Afterwards, a deformable planning CT to daily KV-CBCT image registration method was then utilized to acquire a new structure set on CBCT. The newly generated structures on CBCT were then transferred back to the treatment planning system (TPS) and its HU information were overridden manually with mean HU values obtained from pCT. Finally, the treatment plan was projected onto the CBCT images with the same beam arrangements and monitor units (MUs) to accomplish dose calculation. Planning target volume (PTV) and organs at risk (OARs) from both of the pCTmore » and CBCT were compared to evaluate the dose calculation accuracy. Results: It was found that the dose distribution in the CBCT showed little differences compared to the pCT, regardless of whether PTV or OARs were concerned. Specifically, dose variation in GTV, PTV54, PTV66, SVC, lung and heart were within 0.1%. The maximum dose variation was presented in the spinal cord, which was up to 2.7% dose difference. Conclusion: The proposed method combined with DIR and ROIM technique to accurately calculate dose distribution on CBCT for esophageal cancer is feasible.« less

Purpose: Curative radiotherapy for non-small-cell lung cancer is a difficult challenge, despite the use of conformal radiotherapy. Optimal three-dimensional delineation of treatment volumes is essential for improvement of local control and for limiting of tissue toxicity. Material and Methods: A planning course on clinical practice of lung cancer was held in Barcelona. A questionnaire was given concerning ( 1 ) patient positioning, ( 2 ) planning-computed tomography scan, ( 3 ) accounting for tumor mobility, ( 4 ) investigative-procedure respiration-gated radiotherapy and breath-holding maneuvers, ( 5 ) generation of target volumes, ( 6 ) treatment planning, and ( 7 ) treatment delivery. This questionnaire was made to determine the Spanish application of European recommendations. Results: On the negative side, 1 hospital did not use three-dimensional tools, less than 50% used immobilization devices, and 55.6% used computed tomography slices of greater than 5 mm. On the positive side, 70.4% did not use standard margins for gross target volume derived from a computed tomography scan, 92.6% agreed with the inclusion of Naruke anatomic criteria of 1 cm or more in gross target volume planning, and 75% used V20 to estimate the risk of pneumonitis. Conclusions: This study is the first validation of European recommendations for treatment planning and execution of radiotherapy in lung cancer. The main conclusion is the need to improve the negative aspects determined.

To compare CT and MRI target volumes for nasopharyngeal carcinoma (NPC) and evaluate the role of intensity-modulated radiotherapy (IMRT) in treating composite CT+MRI targets.CT and T(1)/T(2)-weighted MRI scans were obtained for 8 consecutive NPC patients. Using CT, MRI, and fused CT/MRI, various target volumes (gross target volume, clinical target volume, and planning target volume [PTV]) and critical structures were outlined. For each patient, three treatment plans were developed: (1) a three-dimensional conformal RT (3D-CRT) plan using CT-based targets; (2) a 3D-CRT plan using composite CT+MRI targets; and (3) a IMRT plan using CT+MRI targets. The prescription dose was 57.6 Gy and 70.2 Gy to the initial and boost PTV, respectively. Treatment plans were compared using the PTV dose to 95% volume (D(95)), critical structure dose to 5% organ volume (D(5)), and mean dose.Compared with CT, the MRI-based targets were 74% larger, more irregularly shaped, and did not always include the CT targets. For CT-based targets, 3D-CRT plans, in general, achieved adequate target coverage and sparing of critical structures. However, when these plans were evaluated using CT+MRI targets, the average PTV D(95) was approximately 60 Gy (14% underdosing), and critical structure doses were significantly worse. The use of IMRT for CT+MRI targets resulted in marked improvement in the PTV coverage and critical structure sparing: average PTV D(95) improved to 69.3 Gy, brainstem D(5) to43 Gy (19% reduction), spinal cord D(5) to37 Gy (19% reduction), and the mean dose to the parotids and cochlea reduced to below tolerance (23.7 Gy and 35.6 Gy, respectively).CT/MRI fusion improved the determination of target volumes in NPC. In contrast to 3D-CRT, IMRT planning resulted in significantly improved coverage of composite CT+MRI targets and sparing of critical structures.

Despite radical treatment with surgery, radiotherapy and chemotherapy, advanced gliomas recur within months. Geographic misses in radiotherapy planning may play a role in this seemingly ineluctable recurrence. Planning is typically performed on post-contrast MRIs, which are known to underreport tumour volume relative to FDOPA PET scans. FDOPA PET fused with contrast enhanced MRI has demonstrated greater sensitivity and specificity than MRI alone. One sign of potential misses would be differences between gross target volumes (GTVs) defined using MRI alone and when fused with PET. This work examined whether such a discrepancy may occur. Materials and Methods: For six patients, a 75 minute PET scan using 3,4-dihydroxy-6-18F-fluoro-L-phynel-alanine (18F-FDOPA) was taken within 2 days of gadolinium enhanced MRI scans. In addition to standard radiotherapy planning by an experienced radiotherapy oncologist, a second gross target volume (GTV) was defined by an experienced nuclear medicine specialist for fused PET and MRI, while blinded to the radiotherapy plans. The volumes from standard radiotherapy planning were compared to the PET defined GTV. Results: The comparison indicated radiotherapy planning would change in several cases if FDOPA PET data was available. PET-defined contours were external to 95% prescribed dose for several patients. However, due to the radiotherapy margins, the discrepancies were relatively small in size and all received a dose of 50 Gray or more. Conclusions: Given the limited size of the discrepancies it is uncertain that geographic misses played a major role in patient outcome. Even so, the existence of discrepancies indicates that FDOPA PET could assist in better defining margins when planning radiotherapy for advanced glioma, which could be important for highly conformal radiotherapy plans.

Elective nodal irradiation (ENI) is the irradiation of clinically uninvolved lymph node to account for microscopic tumor invasion of these lymph nodes. Dr. Belderbos et al., under the auspices of the International Atomic Energy Agency, have compiled a very thorough summary of the literature regarding ENI for non–small-cell lung cancer (NSCLC). Their major conclusion was, ‘‘The clinical value of ENI is uncertain.’’ However, it is my opinion that the evidence suggests that purposeful elective nodal irradiation is unlikely to improve patient outcomes and can increase toxicity. Thus suggesting that ENI is not beneficial. Additionally, the purposeful inclusion of ENI may hinder progress in treating NSCLC because it is likely to make the safe escalation of RT dose more challenging. This discussion will focus primarily on Stage III NSCLC because that is situation with which radiation oncologists are most often faced. The argument against the use of ENI may be summarized as follows. First, failure is uncommon in nodal regions that are neither clinically involved nor specifically targeted. Belderbos et al. published the result of a trial that is an excellent example. This study included both positron emission tomography and computed tomography scanning, which is consistent with modern state-of-the-art, noninvasive staging. This radiation therapy (RT) dose-escalation trial prospectively evaluated the incidence of isolated nodal failure with omission of the ENI (1). Only the metabolic active lymph nodes were included in the gross target volume. Positron emission tomography scans were obtained shortly before the RT in treatment position. Two (3%) of the 67 positron emission tomography–staged patients developed isolated nodal failures. These results are quite similar to other published reports (2, 3). Second, it appears that a dose greater than the conventional 60–70 Gy is required to cure a larger fraction of NSCLC patients. Le Chevalieret al. reported the results of a randomized

Materials/Methods: One hundred and four patients with nasopharyngeal carcinoma were accrued in this study from Jan. 2001 to Aug. 2004 at the Sun Yat-sen University Cancer Center. There were twenty-four females and eighty males, with a mean age of 42.5 (range 19–73). According to the AJCC Stage Classification, the disease was Stage I in 8 (7.69%), Stage II in 44 (42.31%), Stage III in 35 (33.65%), Stage IVa in 14 (13.46%), and Stage IVb in 3 (2.88%). IMRT method was carried out using an inverse planning system (CORVUS 3.0, Peacock plan) developed by the NOMOS Corp. Treatment was delivered with the Multi-leaf Intensity Modulating Collimator (MIMiC) using a slice-by-slice arc rotation approach. The prescription dose was 64-70Gy/25–30f to the nasopharynx gross target volume (GTVnx) and 60-66Gy/25–30f to the positive neck lymph nodes (GTVnd), and 55-66Gy/25–30f to the volume (Target 1), which was 5–10mm in the superior, inferior, anterior and lateral directions and 2–3mm in the posterior direction beside the GTVnx, and 42-54Gy/25–30f to the volume (Target 2), which was 5–10mm in the superior, inferior, anterior and lateral directions and 2–3mm in the posterior direction beside the Target 1 and included negative neck. The GTVnx and upper neck were irradiated using the IMRT techniques. The lower neck and the supraclavicular fossae were irradiated with a conventional technique using an anterior field. 24 (23.08%) patients received cisplatin and 5-fluorouracil before, or during and after radiotherapy. Acute toxicities were graded according to the RTOG radiation morbidity scoring criteria. The parotid function of some patients was examined by SPECT at the beginning, end, and 1-year after therapy. The Kaplan-Meier method was used to calculate actuarial rates of local-regional progression-free, distant metastasis-free survival, and overall survival from the last date of therapy.

5574 Background: To evaluate the outcome and toxicity of treatment of T4 nasopharyngeal carcinoma using proton radiotherapy. Methods: Between 1990 and 2002, 17 patients with newly diagnosed T4 nasopharyngeal carcinoma received combined conformal proton and photon radiotherapy. There were 3 females and 14 males, with a median age of 41 (range 14 - 73). The N staging distribution was as follows: N0, 8; N1, 3; N2, 5; N3, 1. The WHO histology classification was type 1 in 5 cases, type 2–3 in 12 cases. The median gross tumor volume was 83 cc (range 46 - 216 cc). The median total prescribed dose to the gross target volume was 73.6 Cobalt-Gray-Equivalent (CGE) (range 69 - 76.8). The radiation fractionation schedule was 1.6 CGE twice-daily in 10 patients, 1.2 CGE twice-daily in 1, and 1.8 - 2.0 CGE once-daily in 6. Ten patients received chemotherapy: 3 with induction docetaxel, cisplatin, 5FU, leucovorin; 5 with concurrent cisplatin; 1 with concurrent carboplatin; 1 with concurrent taxol. Results: All patients re...