Water-equivalent pathlength reproducibility due to respiratory pattern variation in charged-particle pancreatic radiotherapy

Kumagai, Motoki; Mori, Shinichiro; Hara, Ryusuke; Asakura, Hiroshi; Kishimoto, Riwa; Kato, Hirotoshi; Yamada, Shigeru; Kandatsu, Susumu

doi:10.1007/s12194-008-0052-z

Cited by 3 publications

(5 citation statements)

References 24 publications

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“…Beam undershoot or overshoot to the target can be instead expected with the rigid alignment procedure, due to the associated relevant shifts in ΔWEL distribution (figure 7). The results obtained with the proposed tracking method are comparable to the performance of the respiratory-gated method tested by Kumagai et al (2009) for charged particle pancreatic therapy, showing WEL variation from −1.5 to 1.3 mm in case of regular breathing and from −9.1 to 8.1 mm for irregular breathing. However, in that study (Kumagai et al 2009) ΔWEL was evaluated only for the end-exhale phase that is more stable and reproducible, while in our work all breathing phases were considered.…”

Section: Discussionsupporting

confidence: 57%

“…The results obtained with the proposed tracking method are comparable to the performance of the respiratory-gated method tested by Kumagai et al (2009) for charged particle pancreatic therapy, showing WEL variation from −1.5 to 1.3 mm in case of regular breathing and from −9.1 to 8.1 mm for irregular breathing. However, in that study (Kumagai et al 2009) ΔWEL was evaluated only for the end-exhale phase that is more stable and reproducible, while in our work all breathing phases were considered. Moreover, the abdominal region analysed for pancreatic cancers (Kumagai et al 2009) is mostly uniform in density, differently from the thoracic region assessed in our case for lung lesions.…”

Section: Discussionsupporting

confidence: 57%

“…However, in that study (Kumagai et al 2009) ΔWEL was evaluated only for the end-exhale phase that is more stable and reproducible, while in our work all breathing phases were considered. Moreover, the abdominal region analysed for pancreatic cancers (Kumagai et al 2009) is mostly uniform in density, differently from the thoracic region assessed in our case for lung lesions.…”

Section: Discussionmentioning

confidence: 99%

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Surrogate-driven deformable motion model for organ motion tracking in particle radiation therapy

et al. 2015

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The aim of this study is the development and experimental testing of a tumor tracking method for particle radiation therapy, providing the daily respiratory dynamics of the patient's thoraco-abdominal anatomy as a function of an external surface surrogate combined with an a priori motion model. The proposed tracking approach is based on a patient-specific breathing motion model, estimated from the four-dimensional (4D) planning computed tomography (CT) through deformable image registration. The model is adapted to the interfraction baseline variations in the patient's anatomical configuration. The driving amplitude and phase parameters are obtained intrafractionally from a respiratory surrogate signal derived from the external surface displacement. The developed technique was assessed on a dataset of seven lung cancer patients, who underwent two repeated 4D CT scans. The first 4D CT was used to build the respiratory motion model, which was tested on the second scan. The geometric accuracy in localizing lung lesions, mediated over all breathing phases, ranged between 0.6 and 1.7 mm across all patients. Errors in tracking the surrounding organs at risk, such as lungs, trachea and esophagus, were lower than 1.3 mm on average. The median absolute variation in water equivalent path length (WEL) within the target volume did not exceed 1.9 mm-WEL for simulated particle beams. A significant improvement was achieved compared with error compensation based on standard rigid alignment. The present work can be regarded as a feasibility study for the potential extension of tumor tracking techniques in particle treatments. Differently from current tracking methods applied in conventional radiotherapy, the proposed approach allows for the dynamic localization of all anatomical structures scanned in the planning CT, thus providing complete information on density and WEL variations required for particle beam range adaptation.

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Section: Discussionsupporting

confidence: 57%

Section: Discussionsupporting

confidence: 57%

Section: Discussionmentioning

confidence: 99%

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Surrogate-driven deformable motion model for organ motion tracking in particle radiation therapy

et al. 2015

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“…2 d, for example, tumor positions at exhalation around 10 s and 100 s after starting treatment are not the same. Further, beam range can vary due to differences in respiratory amplitude, even in the same respiratory phase [ 18 ]. Moreover, the beam weight map was designed to give the prescribed dose to the CTV under the assumption that tumor position in treatment planning and during irradiation is the same.…”

Section: Discussionmentioning

confidence: 99%

Amplitude-based gated phase-controlled rescanning in carbon-ion scanning beam treatment planning under irregular breathing conditions using lung and liver 4DCTs

Mori¹,

Inaniwa²,

Furukawa³

et al. 2014

Journal of Radiation Research

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Amplitude-based gating aids treatment planning in scanned particle therapy because it gives better control of uncertainty with the gate window. We have installed an X-ray fluoroscopic imaging system in our treatment room for clinical use with an amplitude-based gating strategy. We evaluated the effects of this gating under realistic organ motion conditions using 4DCT data of lung and liver tumors. 4DCT imaging was done for 24 lung and liver patients using the area-detector CT. We calculated the field-specific target volume (FTV) for the gating window, which was defined for a single respiratory cycle. Prescribed doses of 48 Gy relative biological effectiveness (RBE)/fraction/four fields and 45 Gy RBE/two fractions/two fields were delivered to the FTVs for lung and liver treatments, respectively. Dose distributions were calculated for the repeated first respiratory cycle (= planning dose) and the whole respiratory data (= treatment dose). We applied eight phase-controlled rescannings with the amplitude-based gating. For the lung cases, D95 of the treatment dose (= 96.0 ± 1.0%) was almost the same as that of the planning dose (= 96.6 ± 0.9%). Dmax/Dmin of the treatment dose (= 104.5 ± 2.2%/89.4 ± 2.6%) was slightly increased over that of the planning dose (= 102.1 ± 1.0%/89.8 ± 2.5%) due to hot spots. For the liver cases, D95 of the treatment dose (= 97.6 ± 0.5%) was decreased by ∼ 1% when compared with the planning dose (= 98.5 ± 0.4%). Dmax/Dmin of the treatment dose was degraded by 3.0%/0.4% compared with the planning dose. Average treatment times were extended by 46.5 s and 65.9 s from those of the planning dose for lung and liver cases, respectively. As with regular respiratory patterns, amplitude-based gated multiple phase-controlled rescanning preserves target coverage to a moving target under irregular respiratory patterns.

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“…For patient positioning in particle therapy, the prescribed dose is not deposited to the target when the water‐equivalent path length (WEL) to the target changes, even if the target is positioned to the correct irradiation position using CT images 11 , 12 , 13 . Therefore, both target positions and the WEL to the target need to be taken into account for accurate target irradiation.…”

Section: Introductionmentioning

confidence: 99%

Development of an automatic evaluation method for patient positioning error

Kubota

Tashiro

Shinohara

et al. 2015

J Applied Clin Med Phys

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Highly accurate radiotherapy needs highly accurate patient positioning. At our facility, patient positioning is manually performed by radiology technicians. After the positioning, positioning error is measured by manually comparing some positions on a digital radiography image (DR) to the corresponding positions on a digitally reconstructed radiography image (DRR). This method is prone to error and can be time‐consuming because of its manual nature. Therefore, we propose an automated measuring method for positioning error to improve patient throughput and achieve higher reliability. The error between a position on the DR and a position on the DRR was calculated to determine the best matched position using the block‐matching method. The zero‐mean normalized cross‐correlation was used as our evaluation function, and the Gaussian weight function was used to increase importance as the pixel position approached the isocenter. The accuracy of the calculation method was evaluated using pelvic phantom images, and the method's effectiveness was evaluated on images of prostate cancer patients before the positioning, comparing them with the results of radiology technicians' measurements. The root mean square error (RMSE) of the calculation method for the pelvic phantom was 0.23±0.05 mm. The coefficients between the calculation method and the measurement results of the technicians were 0.989 for the phantom images and 0.980 for the patient images. The RMSE of the total evaluation results of positioning for prostate cancer patients using the calculation method was 0.32±0.18 mm. Using the proposed method, we successfully measured residual positioning errors. The accuracy and effectiveness of the method was evaluated for pelvic phantom images and images of prostate cancer patients. In the future, positioning for cancer patients at other sites will be evaluated using the calculation method. Consequently, we expect an improvement in treatment throughput for these other sites.PACS number: 87

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Water-equivalent pathlength reproducibility due to respiratory pattern variation in charged-particle pancreatic radiotherapy

Cited by 3 publications

References 24 publications

Surrogate-driven deformable motion model for organ motion tracking in particle radiation therapy

Surrogate-driven deformable motion model for organ motion tracking in particle radiation therapy

Amplitude-based gated phase-controlled rescanning in carbon-ion scanning beam treatment planning under irregular breathing conditions using lung and liver 4DCTs

Development of an automatic evaluation method for patient positioning error

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