Validation of dynamic treatment-couch tracking for prostate SBRT

Ehrbar, Stefanie; Schmid, Sofie; Jöhl, Alexander; Klöck, Stephan; Gückenberger, Matthias; Tanadini‐Lang, Stephanie

doi:10.1002/mp.12236

Cited by 18 publications

(21 citation statements)

References 35 publications

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“…For ten prostate cancer patients, SBRT treatment plans with integrated boost to the index lesion were generated as described in Ehrbar et al [11] using volumetric-modulated arc therapy (VMAT). A mean dose of 5 x 8 Gy = 40 Gy was prescribed to the planning target volume (PTV) around the index lesion (PTV index = index lesion plus 3-mm margin), and a lower dose of 5 x 7 Gy = 35 Gy to the PTV around the prostate (PTV prostate = prostate plus 5 mm).…”

Section: Treatment Planningmentioning

confidence: 99%

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Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Ehrbar

Schmid

Jöhl

et al. 2017

Radiotherapy and Oncology

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Section: Treatment Planningmentioning

confidence: 99%

“…Studies on prostate treatment improvement have been performed for MLC tracking [9,10] and couch tracking [11]. Moreover, both have been compared in a few studies.…”

Section: Introductionmentioning

confidence: 99%

Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Ehrbar

Schmid

Jöhl

et al. 2017

Radiotherapy and Oncology

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“…Time‐resolved light output was measured with the phantom (a) in static position, (b) with motion but without compensation (untracked), and (c) with motion and couch tracking for motion compensation (tracked). The couch tracking system is described in our earlier studies . Briefly, the patient's treatment couch is employed to perform a countermotion of the tumor motion to keep the tumor aligned with the treatment beam.…”

Section: Methodsmentioning

confidence: 88%

“…The couch tracking system is described in our earlier studies. 35,36 Briefly, the patient's treatment couch is employed to perform a countermotion of the tumor motion to keep the tumor aligned with the treatment beam. The Perfect Pitch treatment couch (Varian Medical Systems) was used in this study in combination with a TrueBeam treatment machine (Varian Medical Systems).…”

Section: G Dosimetry System and Tracking Experimentsmentioning

confidence: 99%

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

et al. 2019

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Purpose Real‐time motion‐adaptive radiotherapy of intrahepatic tumors needs to account for motion and deformations of the liver and the target location within. Phantoms representative of anatomical deformations are required to investigate and improve dynamic treatments. A deformable phantom capable of testing motion detection and motion mitigation techniques is presented here. Methods The dynamically dEformable Liver PHAntom (ELPHA) was designed to fulfill three main constraints: First, a reproducibly deformable anatomy is required. Second, the phantom should provide multimodality imaging contrast for motion detection. Third, a time‐resolved dosimetry system to measure temporal effects should be provided. An artificial liver with vasculature was casted from soft silicone mixtures. The silicones allow for deformation and radiographic image contrast, while added cellulose provides ultrasonic contrast. An actuator was used for compressing the liver in the inferior direction according to a prescribed respiratory motion trace. Electromagnetic (EM) transponders integrated in ELPHA help provide ground truth motion traces. They were used to quantify the motion reproducibility of the phantom and to validate motion detection based on ultrasound imaging. A two‐dimensional ultrasound probe was used to follow the position of the vessels with a template‐matching algorithm. This detected vessel motion was compared to the EM transponder signal by calculating the root‐mean‐square error (RMSE). ELPHA was then used to investigate the dose deposition of dynamic treatment deliveries. Two dosimetry systems, radio‐chromic film and plastic scintillation dosimeters (PSD), were integrated in ELPHA. The PSD allow for time‐resolved measurement of the delivered dose, which was compared to a time‐resolved dose of the treatment planning system. Film and PSD were used to investigate dose delivery to the deforming phantom without motion compensation and with treatment‐couch tracking for motion compensation. Results ELPHA showed densities of 66 and 45 HU in the liver and the surrounding tissues. A high motion reproducibility with a submillimeter RMSE (<0.32 mm) was measured. The motion of the vasculature detected with ultrasound agreed well with the EM transponder position (RMSE < 1 mm). A time‐resolved dosimetry system with a 1 Hz time resolution was achieved with the PSD. The agreement of the planned and measured dose to the PSD decreased with increasing motion amplitude: A dosimetric RMSE of 1.2, 2.1, and 2.7 cGy/s was measured for motion amplitudes of 8, 16, and 24 mm, respectively. With couch tracking as motion compensation, these values decreased to 1.1, 1.4, and 1.4 cGy/s. This is closer to the static situation with 0.7 cGy/s. Film measurements showed that couch tracking was able to compensate for motion with a mean target dose within 5% of the static situation (−5% to +1%), which was higher than in the uncompensated cases (−41% to −1%). Conclusions ELPHA is a deformable liver phantom with high motion reproducibility. It was demonstrated t...

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“…In addition, technologies currently under development may provide the tools to safely deliver spatiotemporal liver SBRT treatments in the future. This includes the development of MR-guided radiotherapy [22–24] as well as MLC and couch tracking [25–32]. …”

Section: Discussionmentioning

confidence: 99%

Spatiotemporal fractionation schemes for liver stereotactic body radiotherapy

Unkelbach

Papp

Gaddy

et al. 2017

Radiotherapy and Oncology

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Background and Purpose Dose prescription in stereotactic body radiotherapy (SBRT) for liver tumors is often limited by the mean liver dose. We explore the concept of spatiotemporal fractionation as an approach to facilitate further dose escalation in liver SBRT. Materials and Methods Spatiotemporal fractionation schemes aim at partial hypofractionation in the tumor along with near-uniform fractionation in normal tissues. This is achieved by delivering distinct dose distributions in different fractions, which are designed such that each fraction delivers a high single fraction dose to complementary parts of the tumor while creating a similar dose bath in the surrounding noninvolved liver. Thereby, higher biologically effective doses (BED) can be delivered to the tumor without increasing the mean BED in the liver. Planning of such treatments is performed by simultaneously optimizing multiple dose distributions based on their cumulative BED. We study this concept for five liver cancer patients with different tumor geometries. Results Spatiotemporal fractionation presents a method of increasing the ratio of prescribed tumor BED to mean BED in the noninvolved liver by approximately 10–20%, compared to conventional SBRT using identical fractions. Conclusions Spatiotemporal fractionation may reduce the risk of liver toxicity or facilitate dose escalation in liver SBRT in circumstances where the mean dose to the non-involved liver is the prescription-limiting factor.

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Validation of dynamic treatment-couch tracking for prostate SBRT

Cited by 18 publications

References 35 publications

Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

Comparison of multi-leaf collimator tracking and treatment-couch tracking during stereotactic body radiation therapy of prostate cancer

ELPHA: Dynamically deformable liver phantom for real‐time motion‐adaptive radiotherapy treatments

Spatiotemporal fractionation schemes for liver stereotactic body radiotherapy

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