Clinical experience with lung-specific electromagnetic transponders for real-time tumor tracking in lung stereotactic body radiotherapy

Jaccard, Maud; Champion, Ambroise; Dubouloz, A.; Picardi, C; Plojoux, Jérôme; Soccal, Paola M.; Miralbell, Raymond; Dipasquale, G.; Caparrotti, Francesca

doi:10.1016/j.phro.2019.11.002

Cited by 14 publications

(29 citation statements)

References 39 publications

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“…These studies found that EMTs can be used for monitoring and tracking during treatment and that EMTs are stable and do not migrate. One of these clinical studies evaluated four stereotactic body radiation therapy (SBRT) patients treated in DIBH and three patients treated in free breathing and found that the EMT positions in the lungs remained stable during treatment by using on‐treatment verification CBCTs to visualize whether the EMTs had good alignment with other structures 32 . The other clinical studies were performed using patients treated with free breathing only, with one study using breath‐hold CT images acquired before treatment and periodically throughout to assess whether the EMTs were stable 39 .…”

Section: Discussionmentioning

confidence: 99%

Can bronchoscopically implanted anchored electromagnetic transponders be used to monitor tumor position and lung inflation during deep inspiration breath‐hold lung radiotherapy?

Harris

Yorke

et al. 2022

Medical Physics

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Purpose To evaluate the efficacy of using bronchoscopically implanted anchored electromagnetic transponders (EMTs) as surrogates for 1) tumor position and 2) repeatability of lung inflation during deep‐inspiration breath‐hold (DIBH) lung radiotherapy. Methods Forty‐one patients treated with either hypofractionated (HF) or conventional (CF) lung radiotherapy on an IRB‐approved prospective protocol using coached DIBH were evaluated for this study. Three anchored EMTs were bronchoscopically implanted into small airways near or within the tumor. DIBH treatment was gated by tracking the EMT positions. Breath‐hold cone‐beam‐CTs (CBCTs) were acquired prior to every HF treatment or weekly for CF patients. Retrospectively, rigid registrations between each CBCT and the breath‐hold planning CT were performed to match to 1) spine, 2) EMTs and 3) tumor. Absolute differences in registration between EMTs and spine were analyzed to determine surrogacy of EMTs for lung inflation. Differences in registration between EMTs and the tumor were analyzed to determine surrogacy of EMTs for tumor position. The stability of the EMTs was evaluated by analyzing the difference between inter‐EMT displacements recorded at treatment from that of the plan for the CF patients, as well as the geometric residual (GR) recorded at the time of treatment. Results A total of 219 CBCTs were analyzed. The average differences between EMT centroid and spine registration among all CBCTs were 0.45±0.42 cm, 0.29±0.28 cm, and 0.18±0.15 cm in superior‐inferior (SI), anterior‐posterior (AP) and lateral directions, respectively. Only 59% of CBCTs had differences in registration < 0.5 cm for EMT centroid compared to spine, indicating that lung inflation is not reproducible from simulation to treatment. The average differences between EMT centroid and tumor registration among all CBCTs were 0.13±0.13 cm, 0.14±0.13 cm and 0.12±0.12 cm in SI, AP and lateral directions, respectively. Ninety‐five percent of CBCTs resulted in a < 0.5 cm change between EMT centroid and tumor registration, indicating that EMT positions correspond well with tumor position during treatments. Six out of the seven recorded CF patients had average differences in inter‐EMT displacements ≤0.26 cm and average GR ≤0.22 cm, indicating that the EMTs are stable throughout treatment. Conclusions Bronchoscopically implanted anchored EMTs are good surrogates for tumor position and are reliable for maintaining tumor position when tracked during DIBH treatment, as long as the tumor size and shape are stable. Large differences in registration between EMTs and spine for many treatments suggest that lung inflation achieved at simulation is often not reproduced.

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Section: Discussionmentioning

confidence: 99%

Can bronchoscopically implanted anchored electromagnetic transponders be used to monitor tumor position and lung inflation during deep inspiration breath‐hold lung radiotherapy?

Harris

Yorke

et al. 2022

Medical Physics

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“…Each patient had three lung electromagnetic beacons (Calypso, Varian Medical Systems, Palo Alto, CA) implanted endobronchially under fluoroscopic guidance. 5,22 The lung specific beacons incorporated the electromagnetic beacons along with three prongs, which were embedded into the airway wall during insertion to minimize migration. Planning for implantation was performed using a preimplant CT scan with the aim that all beacons were inserted as close as possible to the tumor, while attempting to form a triangle in three dimensions around the tumor.…”

Section: Methodsmentioning

confidence: 99%

Quantification of the geometric uncertainty when using implanted markers as a surrogate for lung tumor motion

et al. 2021

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Background Fiducial markers are used as surrogates for tumor location during radiation therapy treatment. Developments in lung fiducial marker and implantation technology have provided a means to insert markers endobronchially for tracking of lung tumors. This study quantifies the surrogacy uncertainty (SU) when using endobronchially implanted markers as a surrogate for lung tumor position. Methods We evaluated SU for 17 patients treated in a prospective electromagnetic‐guided MLC tracking trial. Tumor and markers were segmented on all phases of treatment planning 4DCTs and all frames of pretreatment kilovoltage fluoroscopy acquired from lateral and frontal views. The difference in tumor and marker position relative to end‐exhale position was calculated as the SU for both imaging methods and the distributions of uncertainties analyzed. Results The mean (range) tumor motion amplitude in the 4DCT scan was 5.9 mm (1.7–11.7 mm) in the superior–inferior (SI) direction, 2.2 mm (0.9–5.5 mm) in the left–right (LR) direction, and 3.9 mm (1.2–12.9 mm) in the anterior–posterior (AP) direction. Population‐based analysis indicated symmetric SU centered close to 0 mm, with maximum 5th/95th percentile values over all axes of −2.0 mm/2.1 mm with 4DCT, and −2.3/1.3 mm for fluoroscopy. There was poor correlation between the SU measured with 4DCT and that measured with fluoroscopy on a per‐patient basis. We observed increasing SU with increasing surrogate motion. Based on fluoroscopy analysis, the mean (95% CI) SU was 5% (2%–8%) of the motion magnitude in the SI direction, 16% (6%–26%) of the motion magnitude in the LR direction, and 33% (23%–42%) of the motion magnitude in the AP direction. There was no dependence of SU on marker distance from the tumor. Conclusion We have quantified SU due to use of implanted markers as surrogates for lung tumor motion. Population 95th percentile range are up to 2.3 mm, indicating the approximate contribution of SU to total geometric uncertainty. SU was relatively small compared with the SI motion, but substantial compared with LR and AP motion. Due to uncertainty in estimations of patient‐specific SU, it is recommended that population‐based margins are used to account for this component of the total geometric uncertainty.

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“… 3D and 4D imaging (cone beam CT-CBCT).  Newer technologies including imaging and monitoring of electromagnetic transponders (55)(56)(57) or small fiducial markers inserted near the tumor and visible on X-rays or CBCT (58)(59)(60)(61)(62).  Lately surface guidance is used for verification and monitoring of the patient set-up (63,64).…”

Section: Verification Of the Patient Positioning And Target Locationmentioning

confidence: 99%

Technical challenges of linac-based stereotactic ablative body radiotherapy: short review for non-radiation oncologists

Mihai¹,

Rock²,

Milano

2020

Ann Palliat Med

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Stereotactic ablative radiotherapy (SABR) is a radiation technique delivering high doses of radiation in a small number of treatments, to extracranial targets. It is standard of care in patients with inoperable early stage non-small cell lung cancer, and it is increasingly used in patients with oligometastatic disease. The main advantage of SABR is a steep dose gradient, allowing delivery of high biologically effective doses to the target, while minimizing irradiation exposure of the neighboring normal tissues. This results in high rates of local control of the treated target and minimal toxicity risks, and minimal impact on the quality of life of the patients. However, it requires high precision, accuracy and reproducibility during the entire process, from simulation to treatment planning and treatment delivery. This article will focus on general principles of SABR treatment planning and delivery, with emphasis on the strategies to reduce errors related to immobilization, respiratory management and treatment verification.

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Clinical experience with lung-specific electromagnetic transponders for real-time tumor tracking in lung stereotactic body radiotherapy

Cited by 14 publications

References 39 publications

Can bronchoscopically implanted anchored electromagnetic transponders be used to monitor tumor position and lung inflation during deep inspiration breath‐hold lung radiotherapy?

Can bronchoscopically implanted anchored electromagnetic transponders be used to monitor tumor position and lung inflation during deep inspiration breath‐hold lung radiotherapy?

Quantification of the geometric uncertainty when using implanted markers as a surrogate for lung tumor motion

Technical challenges of linac-based stereotactic ablative body radiotherapy: short review for non-radiation oncologists

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