Evaluation of Lung Tumor Target Volume in a Large Sample: Target and Clinical Factors Influencing the Volume Derived From Four-Dimensional CT and Cone Beam CT

Abstract

Background and PurposeThis study aimed to systematically evaluate the influence of target-related and clinical factors on volume differences and the similarity of targets derived from four-dimensional computed tomography (4DCT) and cone beam computed tomography (CBCT) images in lung stereotactic body radiation therapy (SBRT).Materials and Methods4DCT and CBCT image data of 210 tumors from 195 patients were analyzed. The internal gross target volume (IGTV) derived from the maximum intensity projection (MIP) of 4DCT (IGTV-MIP) and the IGTV from CBCT (IGTV-CBCT) were compared with the reference IGTV from 10 phases of 4DCT (IGTV-10). The target size, tumor motion, and the similarity between IGTVs were measured. The influence of target-related and clinical factors on the adequacy of IGTVs derived from 4DCT MIP and CBCT images was evaluated.ResultsThe mean tumor motion amplitude in the 3D direction was 6.5 ± 5 mm. The mean size ratio of IGTV-CBCT and IGTV-MIP compared to IGTV-10 in all patients was 0.71 ± 0.21 and 0.8 ± 0.14, respectively. Female sex, greater BSA, and larger target size were protective factors, while the Karnofsky Performance Status, body mass index, and motion were risk factors for the similarity between IGTV-MIP and IGTV-10. Older age and larger target size were protective factors, while adhesion to the heart, coexistence with cardiopathy, and tumor motion were risk factors for the similarity between IGTV-CBCT and IGTV-10.ConclusionClinical factors should be considered when using MIP images for defining ITV, and when using CBCT images for verifying treatment targets.

Impact of different respiratory gating methods on target delineation and a radiotherapy plan for solitary pulmonary tumors

“…In this study, the displacements of SPTs measured using prospective and retrospective gating methods were compared, and the results were consistent with those of previous studies 8,18 . Li et al 9 . showed that the displacement amplitudes of lung tumors in the left–right, anterior–posterior, and superior–inferior directions were 1.6 mm, 2.2 mm, and 5.5 mm, respectively, which were within the range of displacement amplitudes observed in this study.…”

“…4,5 This individual variability makes it challenging for radiation oncologists to accurately expand the safety margin and delineate the PTV based on traditional experience and documentation if they aim to cover the full range of tumor movement during the respiratory cycle. 6,7 Several researchers, including David, 8 Li, 9 and Guckenberger, 10 have used different methods to measure tumor displacement caused by respiratory motion. The use of fourdimensional (4D) cone beam CT (CBCT) technology allows the real-time observation of tumor trajectory and displacement measurement in three dimensions.…”

Simulation of dosimetric consequences of intrafraction variation of tumor drift in lung cancer stereotactic body radiotherapy

“…Many methods have been used to study the quantitative effects of tumor movement on the target area, while there is no standard method until now ( 12 , 13 ). Target and clinical factors influencing the volume and dose derived from 4DCT and Cone beam CT was evaluation of lung cancer ( 14 ). Many researchers have been trying to find better methods to study the influencing of tumor motion by all kind of simulations ( 15 , 16 ).…”