Dosimetric effect of uncorrected rotations in lung SBRT with stereotactic imaging guidance

Han, Lei; Andrews, Martin B.; Markovich, A; Zhuang, Tingliang

doi:10.1016/j.ejmp.2017.09.135

Cited by 10 publications

(13 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the rotational motions of lung tumors with respect to the rLR, rAP, and rSI directions are larger than those of the prostate because the former are induced by respiratory motion and deformation. Liu et al 30 reported that systematic rotational errors of 2°may cause significant errors in delivering the planned dose in lung SBRT using a statistical method. Our results indicated that the dosimetric accuracy in the coronal and sagittal planes tended to decrease owing to the intrafraction systematic rotation of the lung tumors in rAP, rLR, and rSI, despite the use of respiratory-gated radiation therapy with real-time tumor monitoring [ Figs.…”

Section: Discussionmentioning

confidence: 99%

Analysis of dosimetric impact of intrafraction translation and rotation during respiratory‐gated stereotactic body radiotherapy with real‐time tumor monitoring of the lung using a novel six degrees‐of‐freedom robotic moving phantom

et al. 2020

View full text Add to dashboard Cite

This study aimed to develop a six degrees-of-freedom (6DoF) robotic moving phantom for evaluating the dosimetric impact of intrafraction rotation during respiratory-gated radiotherapy with real-time tumor monitoring in the lung. Materials and Methods: Fifteen patients who had undergone respiratory-gated stereotactic body radiotherapy (SBRT) with the SyncTraX system for lung tumors were enrolled in this study. A waterequivalent phantom (WEP) was set at the tip of the robotic arm. A log file that recorded the three-dimensional positions of three fiducial markers implanted near the lung tumor was used as the input to the 6DoF robotic moving phantom. Respiratory-gated radiotherapy was performed for the WEP, which was driven using translational and rotational motions of the lung tumor. The accuracy of the 6DoF robotic moving phantom was calculated as the difference between the actual and the measured positions. To evaluate the dosimetric impact of intrafraction rotation, the absolute dose distributions under conditions involving gating and movement were compared with those under static conditions. Results: For the sinusoidal patterns, the mean AE standard deviation (SD) of the root mean square errors (RMSEs) of the translation and rotation positional errors was <0.40 mm and 0.30°, respectively, for all directions. For the respiratory motion patterns of 15 patients, the mean AE SD of the RMSEs of the translation and rotation positional errors was <0.55 mm and 0.85°, respectively, for all directions. The c 3%/2mm values under translation with/without gating were 97.6 AE 2.2%/ 80.9 AE 18.1% and 96.8 AE 2.3%/80.0 AE 17.0% in the coronal and sagittal planes, respectively. Further, the c 3%/2mm values under rotation with/without gating were 91.5 AE 6.5%/72.8 AE 18.6% and 90.3 AE 6.1%/72.9 AE 15.7% in the coronal and sagittal planes, respectively. Conclusions: The developed 6DoF robotic phantom system could determine the translational and rotational motions of lung tumors with high accuracy. Further, respiratory-gating radiotherapy with real-time tumor monitoring using an internal surrogate marker was effective in compensating for the translational motion of lung tumors but not for correcting their rotational motion.

show abstract

Section: Discussionmentioning

confidence: 99%

Analysis of dosimetric impact of intrafraction translation and rotation during respiratory‐gated stereotactic body radiotherapy with real‐time tumor monitoring of the lung using a novel six degrees‐of‐freedom robotic moving phantom

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Similar to the results of Liu et al's study, 235 we found that a large target-to-isocenter distance could lead to underdosed targets. Unlike Cao et al 155 's study, we do not include dosimetric assessments for OARs since it is less realistic for highly deformable and mobile organs, such as bowel structures.…”

Section: Discussionsupporting

confidence: 91%

“…A related area of research is evaluation of plan robustness against different types of delivery errors. 155,[232][233][234][235][236] Liu et al 232 proposed a fast offline approach for conventional linac treatments for evaluating the dosimetric impacts on OARs for ± 2 mm and ± 1° level systematic uncertainties (e.g., errors in the collimator, gantry, couch table, isocenter shifts, and leaf bank position). They perturbed the planned dose using rigid transformations considering these uncertainties for six brain and six spine plans.…”

Section: Chapter 5 Dosimetric Assessmentsmentioning

confidence: 99%

“…They also found that the nearly spherical targets and dose distributions for lung SBRT were less sensitive to rotational offsets. Liu et al 235 evaluated the dosimetric effect of uncorrected rotations for 1°, 2°, 3°, and 5° in any direction for conventional linac SBRT lung treatments (N = 22), and recalculated the dose distribution on rotated CT image sets. When the isocenter was > 6 cm away from the GTV center, they found rotations as low as 2° might cause a significant dose reduction (>3%) for PTV D95.…”

Section: Chapter 5 Dosimetric Assessmentsmentioning

confidence: 99%

See 1 more Smart Citation

Patient-Specific Planning Target Volume Margins for Liver Stereotactic Robotic Radiosurgery

Liu¹

View full text Add to dashboard Cite

Purpose: To create analytical tools for a proposed clinical workflow, which implements patientspecific planning target volume (PTV) margins for liver radiation therapy treatments. Methods and Materials: Treatment log files are analyzed for liver treatments to assess tumour motion-tracking accuracy. A uniform PTV margin is estimated that considers motion-tracking errors and deformations, provided that the impact of uncorrected rotations is minimized. A supervised machine learning algorithm employing retrospective data, which emulates a dry-run session prior to treatment planning, is used to investigate if motion-tracking errors are less than 2 mm, and consequently, the standard PTV margins can be reduced by 2 mm. For a safer implementation in the clinic, we employ a warning system that quantifies the probability of a geographic miss if the PTV margin is reduced for every subsequent fraction. A dosimetric analytical tool is proposed to retrospectively assess the dose to a target against different types of delivery errors. The tool is validated by radiochromic film measurements for two very different types of treatments, liver and trigeminal neuralgia (a cranial nerve disorder). Case studies are conducted to access the suitability of a selected PTV margin based on the geometrical and dosimetric coverage of targets. The range of rotations that can be safely allowed for trigeminal neuralgia treatments is quantified since rotational corrections cannot be applied by the system for this specific disease site. Results: Isotropic 4 mm PTV margins are sufficient to account for tracking errors and deformations for 95% of patients. For patient-specific PTV margins, the accuracy of predicting if motion-tracking errors are less than 2 mm is 0.84 ± 0.06 using 5-fold cross-validation. Using the warning system, 11 out of 64 cases predicted to be treated with 2 mm reduced PTV margins might

show abstract

“…They found the rotational setup error was related to the isocenter location, and rotational setup error would be more significant if the isocenter is far from the geometric center of the target. To account for these rotation errors, an extra margin is needed for the margin between CTV and PTV . Zhang et al reported an analytical formula to determine the extra margin between CTV and PTV to account for both translational and rotational setup errors .…”

Section: Introductionmentioning

confidence: 99%

A study of nonuniform CTV to PTV margin expansion incorporating both rotational and translational uncertainties

Miao

Tian

et al. 2019

J Applied Clin Med Phys

View full text Add to dashboard Cite

PurposeIn this work, we implemented a method to obtain a nonuniform clinical target volume (CTV) to planning target volume (PTV) margin caused by both rotational and translational uncertainties and evaluated it in the treatment planning system (TPS).Materials and methodBased on a previously published statistical model, the relationship between a target margin and the distance d (from isocenter to target point), setup uncertainties, and significance level was established. For a single CTV, it can be thought as a combination of many small volume elements or target points. The margin of each point could be obtained using the suggested statistical model. The whole nonuniform CTV–PTV margin was determined by the union of all possible margins of the CTV boundary points. This method was implemented in the Pinnacle3 treatment planning system and compared with uniform margin algorithm. Ten vertebral metastases targets and multiple brain metastases targets were chosen for evaluation.ResultsThe combined CTV–PTV margin as a function of d for various initial translational margin and rotational uncertainties was calculated. The combined margin increases as d, rotational uncertainties and translational margin increase. For the same rotational uncertainty, a smaller initial translational margin requires a larger rotational margin to compensate for the rotational error. Compared with the uniform margin algorithm, the advantage of this method is that it could minimize the PTVs volume for given CTVs to obtain same significance level. Using vertebral metastases targets and multiple brain metastases targets, a series of volume difference was obtained for various translational margins and rotational uncertainties. The volume difference of PTV could be more than 17% when translational margin is 2 mm and rotational uncertainty is 1.4°.ConclusionNonuniform margin algorithm could avoid excessive compensation for the CTV boundary points near isocenter. This method could be used for clinical margin determination and might be useful for the protection of risk organs.

show abstract

Dosimetric effect of uncorrected rotations in lung SBRT with stereotactic imaging guidance

Cited by 10 publications

References 35 publications

Analysis of dosimetric impact of intrafraction translation and rotation during respiratory‐gated stereotactic body radiotherapy with real‐time tumor monitoring of the lung using a novel six degrees‐of‐freedom robotic moving phantom

Analysis of dosimetric impact of intrafraction translation and rotation during respiratory‐gated stereotactic body radiotherapy with real‐time tumor monitoring of the lung using a novel six degrees‐of‐freedom robotic moving phantom

Patient-Specific Planning Target Volume Margins for Liver Stereotactic Robotic Radiosurgery

A study of nonuniform CTV to PTV margin expansion incorporating both rotational and translational uncertainties

Contact Info

Product

Resources

About