Dynamic gating window for compensation of baseline shift in respiratory‐gated radiation therapy

Pepin, Eric W.; Wu, Huanmei; Shirato, Hiroki

doi:10.1118/1.3556588

Cited by 30 publications

(27 citation statements)

References 35 publications

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“…Data collection times were 125 ± 81 s (range 30-492 s), and the duty cycle of the gated irradiation, defined as the ratio of beam-on frames to the total frames, was 0.51 ± 0.18 (range 0.11-0.98). Duty cycles were relatively large with small motions of the internal marker, as previously reported [26].…”

Section: Clinical Data Of Gate Signals For the Evaluationsupporting

confidence: 82%

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Optimization and evaluation of multiple gating beam delivery in a synchrotron-based proton beam scanning system using a real-time imaging technique

et al. 2016

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(Naoki Miyamoto) Purpose:To find the optimum parameter of a new beam control function installed in a synchrotron-based proton therapy system. Methods:A function enabling multiple gated irradiation in the flat top phase has been installed in a real-time-image gated proton beam therapy (RGPT) system. This function is realized by a waiting timer that monitors the elapsed time from the last gate-off signal in the flat top phase. The gated irradiation efficiency depends on the timer value, T w . To find the optimum T w value, gated irradiation efficiency was evaluated for each configurable T w value. 271 gate signal data sets from 58 patients were used for the simulation. Results:The highest mean efficiency 0.52 was obtained in T W = 0.2 s. The irradiation efficiency was approximately 21% higher than at T W = 0 s, which corresponds to ordinary synchrotron operation. The irradiation efficiency was improved in 154 (57%) of the 271 cases. The irradiation efficiency was reduced in 117 cases because the T W value was insufficient or the function introduced an unutilized wait time for the next gate-on signal in the flat top phase. In the actual treatment of a patient with a hepatic tumor at T w = 0.2 s, 4.48 GyE irradiation was completed within 250 s. In contrast, the treatment time of ordinary synchrotron operation was estimated to be 420 s. Conclusions:The results suggest that the multiple gated-irradiation function has potential to improve the gated irradiation efficiency and to reduce the treatment time.

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Section: Clinical Data Of Gate Signals For the Evaluationsupporting

confidence: 82%

“…For example, large marker recognition errors during low dose imaging can be reduced by image processing techniques [24,28]. The dynamic gating window technique [26] or management of the baseline shift [29] might also compensate for the variation of tumor motion and reduce toggling of the gate signals.…”

Section: Discussionmentioning

confidence: 99%

Optimization and evaluation of multiple gating beam delivery in a synchrotron-based proton beam scanning system using a real-time imaging technique

et al. 2016

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“…The model could be further explored for markerless tumor tracking during dose delivery using intrafraction diaphragm motion as a surrogate. For respiratory‐gated radiotherapy, size and position of the gating window were usually determined from each patient's unique respiratory trace 22, 23. Accurate tumor mean position and excursion are essential information for defining the gating window.…”

Section: Discussionmentioning

confidence: 99%

A feasibility study of intrafractional tumor motion estimation based on 4D‐CBCT using diaphragm as surrogate

Zhou

Hong

Yan

et al. 2018

J Applied Clin Med Phys

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PurposeTo investigate the intrafractional stability of the motion relationship between the diaphragm and tumor, as well as the feasibility of using diaphragm motion to estimate lung tumor motion.MethodsEighty‐five paired (pre and posttreatment) daily 4D‐CBCT images were obtained from 20 lung cancer patients who underwent SBRT. Bony registration was performed between the pre‐ and post‐CBCT images to exclude patient body movement. The end‐exhalation phase image of the pre‐CBCT image was selected as the reference image. Tumor positions were obtained for each phase image using contour‐based translational alignments. Diaphragm positions were obtained by translational alignment of its apex position. A linear intrafraction model was constructed using regression analysis performed between the diaphragm and tumor positions manifested on the pretreatment 4D‐CBCT images. By applying this model to posttreatment 4D‐CBCT images, the tumor positions were estimated from posttreatment 4D‐CBCT diaphragm positions and compared with measured values. A receiver operating characteristic (ROC) test was performed to determine a suitable indicator for predicting the estimate accuracy of the linear model.ResultsUsing the linear model, per‐phase position, mean position, and excursion estimation errors were 1.12 ± 0.99 mm, 0.97 ± 0.88 mm, and 0.79 ± 0.67 mm, respectively. Intrafractional per‐phase tumor position estimation error, mean position error, and excursion error were within 3 mm 95%, 96%, and 99% of the time, respectively. The residual sum of squares (RSS) determined from pretreatment images achieved the largest prediction power for the tumor position estimation error (discrepancy < 3 mm) with an Area Under ROC Curve (AUC) of 0.92 (P < 0.05).ConclusionUtilizing the relationship between diaphragm and tumor positions on the pretreatment 4D‐CBCT image, intrafractional tumor positions were estimated from intrafractional diaphragm positions. The estimation accuracy can be predicted using the RSS obtained from the pretreatment 4D‐CBCT image.

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“…With the 4D images, the tumor excursion range with respiration can be obtained and a patient‐specific internal margin can be decided for contouring the internal tumor volume 1, 6, 7. Respiratory gating in radiation delivery provides effective motion control by disabling radiation beam when respiration magnitude exceeds certain threshold, which is beneficial for reducing the planned target size and sparing more healthy tissues 8, 9, 10…”

Section: Introductionmentioning

confidence: 99%

“…The 3D volumetric images at individual respiratory phases are obtained by sorting the oversampled images or sinograms based on the associated respiratory phase‐angle or amplitude from the breathing trace that is acquired simultaneously during scanning 12. In the treatment planning process, if a gated treatment plan is decided, the 4D images are combined with the respiratory motion data to select an appropriate gating window 10. Several respiratory monitoring systems using external surrogates are available in the market for the purposes of measuring respiratory motion for 4D CT imaging and gated treatment 5.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the combined use of two different respiratory monitoring systems for 4D CT simulation and gated treatment

Liu

Lin

Fan

et al. 2018

J Applied Clin Med Phys

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PurposeTwo different respiratory monitoring systems (Varian's Real‐Time Position Management (RPM) System and Siemens’ ANZAI belt Respiratory Gating System) are compared in the context of respiratory signals and 4D CT images that are accordingly reconstructed. This study aims to evaluate the feasibility of combined use of RPM and ANZAI systems for 4DCT simulation and gated radiotherapy treatment, respectively.MethodsThe RPM infrared reflecting marker and the ANZAI belt pressure sensor were both placed on the patient's abdomen during 4DCT scans. The respiratory signal collected by the two systems was synchronized. Fifteen patients were enrolled for respiratory signal collection and analysis. The discrepancies between the RPM and ANZAI traces can be characterized by phase shift and shape distortion. To reveal the impact of the changes in respiratory signals on 4D images, two sets of 4D images based on the same patient's raw data were reconstructed using the RPM and ANZAI data for phase sorting, respectively. The volume of whole lung and the position of diaphragm apex were measured and compared for each respiratory phase.ResultsThe mean phase shift was measured as 0.2 ± 0.1 s averaged over 15 patients. The shape of the breathing trace was found to be in disagreement. For all the patients, the ANZAI trace had a steeper falloff in exhalation than RPM. The inhalation curve, however, was matched for nine patients, steeper in ANZAI for five patients and steeper in RPM for one patient. For 4D image comparison, the difference in whole‐lung volume was about −4% to +4% and the difference in diaphragm position was about −5 mm to +4 mm, compared in each individual phase and averaged over seven patients.ConclusionsCombined use of one system for 4D CT simulation and the other for gated treatment should be avoided as the resultant gating window would not fully match with each other due to the remarkable discrepancy in breathing traces acquired by the two different surrogate systems.

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Dynamic gating window for compensation of baseline shift in respiratory‐gated radiation therapy

Cited by 30 publications

References 35 publications

Optimization and evaluation of multiple gating beam delivery in a synchrotron-based proton beam scanning system using a real-time imaging technique

Optimization and evaluation of multiple gating beam delivery in a synchrotron-based proton beam scanning system using a real-time imaging technique

A feasibility study of intrafractional tumor motion estimation based on 4D‐CBCT using diaphragm as surrogate

Evaluation of the combined use of two different respiratory monitoring systems for 4D CT simulation and gated treatment

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