Purpose To evaluate the amplitude of lung tumor motion and impact of tumor motion on dose delivered to the organs at risk (OARs) during lung stereotactic body radiation therapy (SBRT).Materials and methods This study included 55 patients (30 males and 25 females) with lung cancer who had a small gross tumor volume (GTV). SBRT lung cancer patients were treated with a prescribed dose of 60 Gy in 4 to 8 fractions. Radiotherapy plans were planned in Pinnacle 9.10 with two partial dynamic conformal arcs (DCAs) for the peripheral region (PR) and three to four partial DCAs for the central region (CR). The amplitude of tumor motion and their impact on the maximum dose delivered (D max ) to the OARs were evaluated in the upper lobe (UL) and lower lobe (LL) in cases of CR and PR tumor's localizations. ResultsThe median tumor motions between CR and PR were 4.5 vs 2.2 mm in the UL and 12.5 vs 7.0 mm in the LL. Max dose delivered to the OARs between CR and PR in the UL and LL were as follows: 6.7 vs 8.9 Gy and 9.1 vs 11.7 Gy for the spinal cord; 15.2 vs 0.6 Gy and 22.4 vs 7.6 Gy for the heart; and 11.7 vs 10.8 Gy and 14.8 vs 9.8 Gy for the esophagus, respectively. Conclusion The dose received by the OARs depends on the amplitude of tumor motion and is relative to the OAR's location and motion, due to patient respiration and heart contribution.
Introduction: Using computed tomography (CT) and treatment planning systems (TPS) in radiotherapy, due to the difference in photon beam energy on CT and linear accelerator, it is necessary to convert Hounsfield units (HU) to relative electron density (RED) values. The aim of this dosimetric study was to determine whether there is a significant effect of potential in the CT tube, field of view size (FOV), and phantom dimensions on the CT conversion curve CT-RED. The second aim is whether there are significant differences between the CT-RED obtained by the Computerized Imaging Reference Systems (CIRS) Thorax 002LFC phantom and the “reference” curve in the TPS, obtained by the CIRS 062M pelvis phantom, at the same CT conditions.Methods: Heterogeneous CIRS 062M and CIRS Thorax 002LFC phantoms were used, which anatomically and dimensionally represent the human pelvis, head, and thorax, with a set of known RED inserts. They were scanned on a CT LightSpeed GE simulator and obtained CT-RED.Results: The high voltage in the CT tube had a significant effect on the HU (t = 10.72, p < 0.001) for RED values >1.1, while FOV as a parameter did not show statistical significance for the 062M pelvis phantom. Comparing the slopes (062M pelvis and head) of the CT-RED for RED ≥ 1.1, the obtained value is t = 1.404 (p = 0.163). In the case of a 062M pelvis and a 002LFC phantom, we have seen a difference in RED values (for the same HU value) of 5 % in the RED region ≥ 1.1 (bone).Conclusion: Patients should be imaged on a CT simulator only at the potential of the CT tube on which the conversion curve was recorded. The influence of the FOV and scanned phantom dimensions is not statistically significant on the appearance of the calibration curve (RED ≥ 1.1).
IntroductIonLung stereotactic body radiation therapy (SBRT) is used for the treatment of early-stage nonsmall cell lung cancer and metastatic lung tumors. [1,2] SBRT treatments are delivered in a hypofractionation mode, with high doses in a few fractions (from 3 to 8 fractions), depending on tumor localization (central or peripheral tumors). [3] The treatment of lung cancer with high doses can be impacted by tumor motion and proximity to the organ at risk. [4][5][6][7] Various techniques were developed to take into consideration tumor motion during treatment delivery to accurately target the moving tumor and to spare healthy tissues. [8][9][10] The abdominal compression technique is used to reduce the breathing amplitude, reducing the amplitude of the tumor motion throughout the respiratory cycle. [8] Radiation during a certain phase of the respiratory cycle can be performed using respiratory gating radiation therapy (RGRT). [9] Real-time tumor tracking allows for tumor irradiation throughout the respiratory cycle. [10] RGRT does not require controlled breathing or breath hold during simulation and dose delivery. There are three types of gating: phase gating, amplitude gating, and breath-hold gating techniques. With phase gating, the treatment is delivered during a certain phase of the respiratory cycle. With amplitude gating, the treatment is delivered when a chosen threshold of the breathing amplitude is reached, which is generally during the Introduction: This study compared phase-gated and amplitude-gated dose deliveries to the moving gross tumor volume (GTV) in lung stereotactic body radiation therapy (SBRT) using Gafchromic External Beam Therapy (EBT3) dosimetry film. Materials and Methods: Eighty treatment plans using two techniques (40 phase gated and 40 amplitude gated) were delivered using dynamic conformal arc therapy (DCAT). The GTV motion, breathing amplitude, and period were taken from 40 lung SBRT patients who performed regular breathing. These parameters were re-simulated using a modified Varian breathing mini phantom. The dosimetric accuracy of the phase-and amplitude-gated treatment plans was analyzed using Gafchromic EBT3 dosimetry film. The treatment delivery efficacy was analyzed for gantry rotation, number of monitor unit (MU), and target position per triggering window. The time required to deliver the phase-and amplitude-gated treatment techniques was also evaluated. Results: The mean dose (range) per fraction was 16.11 ± 0.91 Gy (13.04-17.50 Gy) versus 16.26 ± 0.83 Gy (13.82-17.99 Gy) (P < 0.0001) for phase-and amplitude-gated delivery. The greater difference in the gamma passing rate was 1.2% ±0.4% in the amplitude-gated compared to the phase gated. The gantry rotation per triggering time (tt) was 2° ±1° (1.2°-3°) versus 5° ±1° (3°-6°) (P < 0.0001) and MU per tt was 10 ± 3 MU (6-13 MU) versus 24 ± 7 MU (12-32 MU) (P < 0.0001), for phase-versus amplitude-gated techniques. A 90 beam interruption in the phase-gated technique impacted the treatment delivery efficacy, increasing the treatmen...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.