Effects of variable‐width jaw motion on beam characteristics for Radixact Synchrony®

Ferris, William S.; Culberson, Wesley S.; Smilowitz, Jennifer B.; Bayouth, John E.

doi:10.1002/acm2.13234

Cited by 4 publications

(7 citation statements)

References 11 publications

(30 reference statements)

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“…30 Underdosings of the target (1% for GTV and ∼4% for PTV) have been reported for other studies comparing 4D-accumulated, motion-compensated tracking doses to planned dose. 10,31 The differences in target dose may be from the dose deformation effect, 11,[31][32][33] the unflattened profile of the Radixact beam (causing maximum decrease in output of 3%-4% for the 1-cm jaw and 1%-2% for the 2.5-cm jaw as the target moves off -axis), 3,7 the discrete nature of MLC compensation (which allows for axial motion less than ±3.125 cm to be uncompensated), and uncertainties in the framework. These effects cause changes to the dose distribution within the field and penumbra, which are much smaller than changes to the dose distribution due to changes to the field (such as jaw sway).…”

Section: Discussionmentioning

confidence: 99%

“…The treatment plan is a plan that is intended to be treated with Synchrony and is planned on one of the phases of the 4DCT scan, designated as the reference phase. The reference phase is often the maximum inspiration or exhalation phase; however, using a mid‐ventilation phase will maximize the range of motion that can be corrected 4 and reduces the impact of the unflattened beam profile on the output as the target moves off axis 7 . The reference phase used for the calculations should be replicated by the patient during the pre‐treatment alignment images (e.g., chest/abdomen/diaphragm position and lung volume).…”

Section: Methodsmentioning

confidence: 99%

“…There have been several studies demonstrating Synchrony's ability to accurately correct the treatment for target motion. [1][2][3][4][5][6][7] However, there have not been any publications to date investigating the effect of the motion compensation on doses to OARs, which is a critical component of successful tracking since the planned treatment is changed in real time. 8 In fact, to our knowledge there are no works in the literature investigating the effect of any real-time tracking system on dose deviations to OARs.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Using 4D dose accumulation to calculate organ‐at‐risk dose deviations from motion‐synchronized liver and lung tomotherapy treatments

Ferris

Chao

Smilowitz

et al. 2022

J Applied Clin Med Phys

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Tracking systems such as Radixact Synchrony change the planned delivery of radiation during treatment to follow the target. This is typically achieved without considering the location changes of organs at risk (OARs). The goal of this work was to develop a novel 4D dose accumulation framework to quantify OAR dose deviations due to the motion and tracked treatment. The framework obtains deformation information and the target motion pattern from a four‐dimensional computed tomography dataset. The helical tomotherapy treatment plan is split into 10 plans and motion correction is applied separately to the jaw pattern and multi‐leaf collimator (MLC) sinogram for each phase based on the location of the target in each phase. Deformable image registration (DIR) is calculated from each phase to the references phase using a commercial algorithm, and doses are accumulated according to the DIR. The effect of motion synchronization on OAR dose was analyzed for five lung and five liver subjects by comparing planned versus synchrony‐accumulated dose. The motion was compensated by an average of 1.6 cm of jaw sway and by an average of 5.7% of leaf openings modified, indicating that most of the motion compensation was from jaw sway and not MLC changes. OAR dose deviations as large as 19 Gy were observed, and for all 10 cases, dose deviations greater than 7 Gy were observed. Target dose remained relatively constant (D95% within 3 Gy), confirming that motion‐synchronization achieved the goal of maintaining target dose. Dose deviations provided by the framework can be leveraged during the treatment planning process by identifying cases where OAR doses may change significantly from their planned values with respect to the critical constraints. The framework is specific to synchronized helical tomotherapy treatments, but the OAR dose deviations apply to any real‐time tracking technique that does not consider location changes of OARs.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using 4D dose accumulation to calculate organ‐at‐risk dose deviations from motion‐synchronized liver and lung tomotherapy treatments

Ferris

Chao

Smilowitz

et al. 2022

J Applied Clin Med Phys

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“…The Synchrony ® motion management system (Accuray, Inc., Sunnyvale, CA) on the Radixact ® linear accelerator uses kilovoltage (kV) images to locate the target periodically during treatment [3][4][5][6][7][8][9][10]. Images are acquired at 2 to 6 angles each time the gantry rotates.…”

Section: Introductionmentioning

confidence: 99%

Fiducial visibility on planar images during motion-synchronized tomotherapy treatments

Ferris¹,

DeWerd²,

Culberson³

2022

Biomed. Phys. Eng. Express

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Objective: Synchrony® is a motion management system on the Radixact® that uses planar kV radiographs to locate the target during treatment. The purpose of this work is to quantify the visibility of fiducials on these radiographs. Approach: A custom acrylic slab was machined to hold 8 gold fiducials of various lengths, diameters, and orientations with respect to imaging axis. The slab was placed on the couch at the imaging isocenter and planar radiographs were acquired perpendicular to the custom slab with varying thicknesses of acrylic on each side. Fiducial signal to noise ratio (SNR) and detected fiducial position error in millimeters were quantified. Main Results: The minimum output protocol (100 kVp, 0.8 mAs) was sufficient to detect all fiducials on both Radixact configurations when the thickness of the phantom was 20 cm. However, no fiducials for any protocol were detected when the phantom was 50 cm thick. The algorithm accurately detected fiducials on the image when the SNR was larger than 4. The MV beam was observed to cause RFI artifacts on the kV images and to decrease SNR by an average of 10%. Significance: This work provides the first data on fiducial visibility on kV radiographs from Radixact Synchrony treatments. The Synchrony fiducial detection algorithm was determined to be very accurate when sufficient SNR is achieved. However, a higher output protocol may need to be added for use with larger patients. This work provided groundwork for investigating visibility of fiducial-free solid targets in future studies and provided a direct comparison of fiducial visibility on the two Radixact configurations, which will allow for intercomparison of results between configurations.

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“… 12 , 13 Recently, a new tumor‐tracking system (Synchrony®; Accuray Inc.) that has been available for cyberknife has been developed for clinical use in the recent tomotherapy (Radixact®; Accuray Inc.). 14 , 15 , 16 , 17 , 18 , 19 With this system, the internal and set‐up margins can be tightened, like cyberknife, compared to conventional tomotherapy in the planning of SBRT for localized prostate cancer.…”

Section: Introductionmentioning

confidence: 99%

Stereotactic body radiotherapy using a hydrogel spacer for localized prostate cancer: A dosimetric comparison between tomotherapy with the newly‐developed tumor‐tracking system and cyberknife

Manabe

Hashimoto

Mukouyama

et al. 2021

J Applied Clin Med Phys

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Purpose With a new tumor‐tracking system (Synchrony®) for tomotherapy (Radixact®), the internal and set‐up margins can be tightened, like cyberknife (CyberKnife®), in the planning of stereotactic body radiotherapy (SBRT) for prostate cancer. Recently, the usefulness of placing a hydrogel spacer between the prostate and rectum has been established in prostate radiotherapy. We evaluated the characteristics of tomotherapy plans with the tumor‐tracking system and compared them with cyberknife SBRT plans for localized prostate cancer using a hydrogel spacer. Methods In 20 patients, two plans were created and compared using tomotherapy and cyberknife. All patients underwent hydrogel spacer injection behind the prostate before simulation CT and MRI for fusion. For all plans, 36.25 Gy in 7.25‐Gy fractions for a minimum coverage dose of 95% of planning target volume (PTV) (D95%) was prescribed. The D99% of PTV and D0.1 ml of the PTV, urethra, bladder, and rectum were intended to be > 90%, 110–130%, 100–110%, <110%, and <100%, respectively, of the prescribed doses. Results All plans using tomotherapy and cyberknife achieved the intended dose constraints. The cyberknife plans yielded better median PTV‐V110% (volume of PTV covered by 110% isodose line, 54.8%), maintaining lower median D0.1 ml of the urethra (37.5 Gy) and V80% of the bladder (11.0 ml) compared to the tomotherapy plans (39.0%; p < 0.0001, 38.2 Gy; p < 0.0001, and 18.3 ml; p < 0.0001, respectively). The tomotherapy plans were superior to the cyberknife plans for the rectum (V80% = 0.4 vs. 1.0 ml, p < 0.001; D1ml = 26.4 vs. 29.0 Gy, p = 0.013). Conclusions Our results suggested that tomotherapy with the tumor‐tracking system has reasonable potential for SBRT for localized prostate cancer using a hydrogel spacer.

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Effects of variable‐width jaw motion on beam characteristics for Radixact Synchrony®

Cited by 4 publications

References 11 publications

Using 4D dose accumulation to calculate organ‐at‐risk dose deviations from motion‐synchronized liver and lung tomotherapy treatments

Using 4D dose accumulation to calculate organ‐at‐risk dose deviations from motion‐synchronized liver and lung tomotherapy treatments

Fiducial visibility on planar images during motion-synchronized tomotherapy treatments

Stereotactic body radiotherapy using a hydrogel spacer for localized prostate cancer: A dosimetric comparison between tomotherapy with the newly‐developed tumor‐tracking system and cyberknife

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