Evaluation of the setup margins for cone beam computed tomography–guided cranial radiosurgery: A phantom study

Ortega, J.F. Calvo; Wunderink, Wouter; Delgado, David; Moragues, Sandra; Pozo, Miquel; Casals, Joan

doi:10.1016/j.meddos.2015.12.006

Cited by 7 publications

(6 citation statements)

References 28 publications

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“…The measure of end-to-end system accuracy is the distance between specified isodose points in the planned and measured dose profiles. This measurement procedure includes all sources of mechanical error causing a shift of the dose distribution from any of the systems involved from simulation to beam delivery, including the isocenter accuracies of the CBCT system and the radiation beam, the localization uncertainty of the CBCT system and the couch, and the MLC uncertainty [ 14 ]. A total of 14 dose planes were measured between both linear accelerators, where 10 planes were measured in the lateral direction, and 4 planes were measured in the longitudinal direction.…”

Section: Methodsmentioning

confidence: 99%

“…To represent the systematic error component, the standard deviation over the average planar shift values was calculated. The random component consists of the RMS sum of the individual intra-planar standard deviations [ 14 ]. Because there were no significant differences in the standard deviations of the measurements of the two directions, all measured planes were binned together.…”

Section: Methodsmentioning

confidence: 99%

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Analytical setup margin for spinal stereotactic body radiotherapy based on measured errors

2021

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Background No consensus currently exists about the correct margin size to use for spinal SBRT. Margins have been proposed to account for various errors individually, but not with all errors combined to result in a single margin value. The purpose of this work was to determine a setup margin for five-fraction spinal SBRT based on known errors during radiotherapy to achieve at least 90% coverage of the clinical target volume with the prescription dose for at least 90% of patients and not exceed a 30 Gy point dose or 23 Gy to 10% of the spinal cord subvolume. Methods The random and systematic error components of intrafraction motion, residual setup error, and end-to-end system accuracy were measured. The patient’s surface displacement was measured to quantify intrafraction motion, the residual setup error was quantified by re-registering accepted daily cone beam computed tomography setup images, and the displacement between measured and planned dose profiles in a phantom quantified the end-to-end system accuracy. These errors and parameters were used to identify the minimum acceptable margin size. The margin recommendation was validated by assessing dose delivery across 140 simulated patient plans suffering from various random shifts representative of the measured errors. Results The errors were quantified in three dimensions and the analytical margin generated was 2.4 mm. With this margin applied in the superior/inferior direction only, at least 90% of the CTV was covered with the prescription dose for 96% of the 140 patients simulated with minimal negative effect on the spinal cord dose levels. Conclusions The findings of this work support that a 2.4 mm margin applied in the superior/inferior direction can achieve at least 90% coverage of the CTV for at least 90% of dual-arc volumetric modulated arc therapy spinal SBRT patients in the presence of errors when immobilized with vacuum bags.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Analytical setup margin for spinal stereotactic body radiotherapy based on measured errors

2021

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“…A number of Authors gave an explicit formula to determine the appropriate set-up margins in radiotherapy. [22][23][24][25][26] Each formula was built for specific situations of fractionations, beam profiles, target shapes, sites of irradiation, biological dose equivalence, or radiation techniques. Margins should take account of systematic uncertainties, as well as of random uncertainties in the positioning of the patient.…”

Section: Resultsmentioning

confidence: 99%

“…A number of Authors gave an explicit formula to determine the appropriate set‐up margins in radiotherapy 22–26 . Each formula was built for specific situations of fractionations, beam profiles, target shapes, sites of irradiation, biological dose equivalence, or radiation techniques.…”

Section: Resultsmentioning

confidence: 99%

An empirical approach to the definition of the target margins in eye radiosurgery

Perrone

Laliscia

Traino

et al. 2023

J Applied Clin Med Phys

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Introduction: A system for stabilizing and monitoring eye movements during LINAC-based photon beam one single fraction stereotactic radiotherapy was developed at our Institution. This study aimed to describe the feasibility and the efficacy of our noninvasive optical localization system that was developed, tested, and applied in 20 patients treated for uveal melanoma. Methods: Our system consisted of a customized thermoplastic mask to immobilize the head, a gaze fixation LED, and a digital micro-camera. The localization procedure, which required the active collaboration of the patient, served to monitor the eye movements during all phases of the treatment, starting from the planning computed tomography up to the administration of radiotherapy, and allowed the operators to suspend the procedure and to interact with the patient in case of large movements of the pupil. Results: Twenty patients were treated with stereotactic radiosurgery (27 Gy in one fraction) for primary uveal melanoma. All patients showed a good tolerance to the treatment; until now, all patients were in local control during the follow up and one died for distant progression 6 months after radiosurgery. Conclusions: This study showed that this noninvasive technique, based on eye position control, is appropriate and can contribute to the success of LINACbased stereotactic radiotherapy. A millimetric safety margin to the clinical target volume was adequate to take account for the organ movement. All patients treated till now showed a good local control; failures in the disease control were due to metastatic spread.

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“…Conventionally, using invasive fixation devices to the patient's skull, such as metal frames or rings were essential for patient immobilization and target localization in SRS/SRT treatment of intracranial lesions . However, noninvasive (frameless) SRS/SRT treatment has become a standard procedure owing to the development of image‐guided radiotherapy (IGRT) systems in recent years . Chang et al reported that the accuracy of the patient setup with cone‐beam computed tomography (CBCT) image guidance was comparable to that with frame‐based radiosurgery systems .…”

Section: Introductionmentioning

confidence: 99%

Impact of patient positioning uncertainty in noncoplanar intracranial stereotactic radiotherapy

Tanaka

Oita

Inomata

et al. 2020

J Applied Clin Med Phys

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The aim of this study is to evaluate the patient positioning uncertainty in noncoplanar stereotactic radiosurgery or stereotactic radiotherapy (SRS/SRT) for intracranial lesions with the frameless 6D ExacTrac system. In all, 28 patients treated with SRS/SRT of 70 treatment plans at our institution were evaluated in this study. Two X‐ray images with the frameless 6D ExacTrac system were first acquired to correct (XC) and verify (XV) the patient position at a couch angle of 0º. Subsequently, the XC and XV images were also acquired at each planned couch angle for using noncoplanar beams to detect position errors caused by rotating a couch. The translational XC and XV shift values at each couch angle were calculated for each plan. The percentages of the translational XC shift values within 1.0 mm for each planned couch angle for using noncoplanar beams were 77.86%, 72.26%, and 98.47% for the lateral, longitudinal, and vertical directions, respectively. Those within 2.0 mm were 98.22%, 97.96%, and 99.75% for the lateral, longitudinal, and vertical directions, respectively. The maximum absolute values of the translational XC shifts among all planned couch angles for using noncoplanar beams were 2.69, 2.45, and 2.17 mm for the lateral, longitudinal, and vertical directions, respectively. The overall absolute values of the translational XV shifts were less than 1.0 mm for all directions except for one case in the longitudinal direction. The patient position errors were detected after couch rotation for using noncoplanar beams, and they exceeded a planning target volume (PTV) margin of 1.0–2.0 mm used commonly in SRS/SRT treatment. These errors need to be corrected at each planned couch angle, or the PTV margin should be enlarged.

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Evaluation of the setup margins for cone beam computed tomography–guided cranial radiosurgery: A phantom study

Cited by 7 publications

References 28 publications

Analytical setup margin for spinal stereotactic body radiotherapy based on measured errors

Analytical setup margin for spinal stereotactic body radiotherapy based on measured errors

An empirical approach to the definition of the target margins in eye radiosurgery

Impact of patient positioning uncertainty in noncoplanar intracranial stereotactic radiotherapy

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