Clinical experience of volumetric‐modulated flattening filter free stereotactic body radiation therapy of lesions in the lung with deep inspiration breath‐hold

PurposeThis study evaluated the intra‐ and inter‐fractional variation of tumors with fiducial markers (FMs), relative to the tumor‐FM distance, to establish how close an FM should be inserted for respiratory‐gated stereotactic body radiation therapy (RG‐SBRT).MethodsForty‐five lung tumors treated with RG‐SBRT were enrolled. End‐expiratory computed tomography (CT) (CTplan) and four‐dimensional‐CT (4D‐CT) scans were obtained for planning. End‐expiratory CT (CTfr) scanning was performed before each fraction. The FMs were divided into two groups based on the median tumor‐FM distance in the CTplan (Dp). For the intra‐fractional variation, the correlations between the corresponding tumor and FM intra‐fractional motions, defined as the centroid coordinates of those in each 0–90% phase, with the 50% phase of 4D‐CT as the origin, were calculated in the left‐right, anterior‐posterior, and superior‐inferior directions. Furthermore, the maximum difference in the tumor‐FM distance in each phase of 4D‐CT scan, based on those in the 50% phase of 4D‐CT scan (Dmax), was obtained. Inter‐fractional variation was defined as the maximum distance between the tumors in CTplan and CTfr, when the CT scans were fused based on each FM or vertebra.ResultsThe median Dp was 26.1 mm. While FM intra‐fractional motions were significantly and strongly correlated with the tumor intra‐fractional motions in only anterior‐posterior and superior‐inferior directions for the Dp > 26 mm group, they were significantly and strongly correlated in all directions for the Dp ≤ 26 mm group. In all directions, Dmax values of the Dp ≤ 26 mm group were lower than those of the Dp > 26 mm group. The inter‐fractional variations based on the Dp ≤ 26 mm were smaller than those on the Dp > 26 mm and on the vertebra in all directions.ConclusionsRegarding intra‐ and inter‐fractional variation, FMs for Dp ≤ 26 mm can increase the accuracy for RG‐SBRT.

Section: Introductionmentioning

confidence: 99%

Intra‐ and inter‐fractional variations of tumors with fiducial markers measured using respiratory‐correlated computed tomography images for respiratory gated lung stereotactic body radiation therapy

Manabe,

Shiinoki,

Fujimoto

et al. 2024

“…When combined with hypofractionation of three to five treatments, DIBH becomes a tolerable option for specific patients undergoing lung SBRT. 14 Presently, image-guided radiotherapy (IGRT) utilizing kilovoltage cone-beam computed tomography (CBCT) is widely utilized. This approach provides 3D information for soft tissues, contributing to a substantial improvement in the precision of radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

“…The application of advanced treatment techniques, such as volumetric modulated arc therapy (VMAT) and higher dose rate flattening filter‐free (FFF) beam, has contributed to a reduction in treatment delivery time. When combined with hypofractionation of three to five treatments, DIBH becomes a tolerable option for specific patients undergoing lung SBRT 14 …”

Section: Introductionmentioning

confidence: 99%

Evaluating intra‐fractional tumor motion in lung stereotactic radiotherapy with deep inspiration breath‐hold

Fu,

Zhang,

Mehta

et al. 2024

PurposeTo evaluate the intra‐fractional tumor motion in lung stereotactic body radiotherapy (SBRT) with deep inspiration breath‐hold (DIBH), and to investigate the adequacy of the current planning target volume (PTV) margins.MethodsTwenty‐eight lung SBRT patients with DIBH were selected in this study. Among the lesions, twenty‐three were at right or left lower lobe, two at right middle lobe, and three at right or left upper lobe. Post‐treatment gated cone‐beam computed tomography (CBCT) was acquired to quantify the intra‐fractional tumor shift at each treatment. These obtained shifts were then used to calculate the required PTV margin, which was compared with the current applied margin of 5 mm margin in anterior‐posterior (AP) and right‐left (RL) directions and 8 mm in superior‐inferior (SI) direction. The beam delivery time was prolonged with DIBH. The actual beam delivery time with DIBH (Tbeam_DIBH) was compared with the beam delivery time without DIBH (Tbeam_wo_DIBH) for the corresponding SBRT plan.ResultsA total of 113 treatments were analyzed. At six treatments (5.3%), the shifts exceeded the tolerance defined by the current PTV margin. The average shifts were 0.0 ± 1.9 mm, 0.1±1.5 mm, and ‐0.5 ± 3.7 mm in AP, RL, and SI directions, respectively. The required PTV margins were determined to be 4.5, 3.9, and 7.4 mm in AP, RL, and SI directions, respectively. The average Tbeam_wo_DIBH and Tbeam_DIBH were 2.4 ± 0.4 min and 3.6 ± 1.5 min, respectively. The average treatment slot for lung SBRT with DIBH was 25.3 ± 7.9 min.ConclusionIntra‐fractional tumor motion is the predominant source of treatment uncertainties in CBCT‐guided lung SBRT with DIBH. The required PTV margin should be determined based on data specific to each institute, considering different techniques and populations. Our data indicate that our current applied PTV margin is adequate, and it is possible to reduce further in the RL direction. The time increase of Tbeam_DIBH, relative to the treatment slot, is not clinically significant.

“…Respiratory motion management techniques such as 4DCT, gating, and deep inspiration breath hold (DIBH) have been widely used in external beam radiation therapy for lung cancer, 1,2 liver cancer, 3–6 pancreatic cancer, 7 breast cancer, 8–12 etc., either in VMAT/IMRT or 3D radiotherapy. To manage respiratory motion, Varian's real‐time position management (RPM) system uses a reflector as a surrogate for organ motion due to patients’ respiration.…”

Section: Introductionmentioning

confidence: 99%

Comparison of baseline drifts using three reflector blocks versus using a single reflector block for the calibration of wall‐mounted Respiratory Gating for Scanner (RGSC) camera integrated with a CT

Liu,

Shi,

Prakash

et al. 2023

BackgroundThe calibration of the Respiratory Gating for SCanner (RGSC) system is critical to achieve better and more stable accuracy. The current procedure for a wall‐mounted RGSC system has a relatively large residual error.PurposeTo compare the baseline drifts in the image acquisition of DIBH using three reflector blocks versus using a single reflector block in the calibration of a wall‐mounted RGSC camera system.Materials and methodsVarian provides a calibration plate with three rows of calibration points: each row is separated by 15 cm longitudinally and by 10 cm laterally. In Varian's single‐block calibration method, the reflector block was first placed on the center point of the calibration plate and aligned with the scanner isocenter. The calibration took a picture of the block, then placed the block on the other eight points sequentially. In the proposed three‐block method, we placed three reflector blocks on the center row, with the center block aligned with the isocenter, and we took a picture of the center block by manually blocking the other two blocks in calibration. By moving the couch longitudinally in or out 15 cm, the calibration goes through all nine points. Monte Carlo simulation was done using Matlab to analyze the calibration matrix eigenvalue characteristics.ResultsFor a typical scan length of 40 cm of DIBH, the residual baseline drift in simulated DIBH is 0.02 ± 0.03 versus 0.30 ± 0.12 cm for three‐block calibration and single‐block calibration, respectively. To achieve 0.5 mm tolerance for the eigenvalue, the laser and reflector box should be within ±3 mm uncertainties based on the eigenvalue simulation.ConclusionThree‐block calibration method effectively removes baseline drift caused by couch movement in DIBH/4D CT scan for the wall‐mounted camera while the single‐block calibration method still has significant residual baseline drift.