Technical note: On the impact of the kV imaging configuration on doses from planar images during motion‐synchronized treatments on Radixact®

Ferris, William S.; DeWerd, Larry A.; Bayouth, John E.; Culberson, Wesley S.

doi:10.1002/acm2.13371

Cited by 3 publications

(8 citation statements)

References 7 publications

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“…A study by Ferris showed that when the kV imaging system was upgraded from Gen1 to Gen2, the kV doses per mAs were found to be reduced by ~66% for planar images during motion-synchronized treatments on Radixact ® [ 17 ]. Hence, with the improved target tracking accuracy and the decrease in the kV imaging dose, the Gen2 kV system is a better option than the Gen1 system for Radixact ® Lung Synchrony ® treatment.…”

Section: Discussionmentioning

confidence: 99%

The impact of the ClearRT™ upgrade on target motion tracking accuracy in Radixact® Synchrony® lung treatments

Kong

Chiu²,

Cheung³

et al. 2022

Rep Pract Oncol Radiother.

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Section: Discussionmentioning

confidence: 99%

The impact of the ClearRT™ upgrade on target motion tracking accuracy in Radixact® Synchrony® lung treatments

Kong

Chiu²,

Cheung³

et al. 2022

Rep Pract Oncol Radiother.

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“…There are two versions of Radixact available for clinical use, with and without kV computed tomography (kVCT) acquisition capabilities. This hardware difference affects the kV source-to-axis distance (SAD) and source-to-detector distance, which are 57.5 cm and 113.5 cm, respectively, for the standard configuration and 104.8 cm and 156.2 cm for the extended (with kVCT capabilities) configuration [12]. Currently, the imaging protocols (mAs, kVp) available on each configuration are the same despite the difference in SAD (e.g., the 'Large Thorax' protocol is 120 kVp 1.6 mAs for both).…”

Section: Introductionmentioning

confidence: 99%

“…Currently, the imaging protocols (mAs, kVp) available on each configuration are the same despite the difference in SAD (e.g., the 'Large Thorax' protocol is 120 kVp 1.6 mAs for both). Recent work has indicated that dose per mAs to the patient from planar radiographs is about 66% less for the extended configuration, primarily due to the extended distance [12]. It is hypothesized that image quality and fiducial visibility will be different between the two versions (for the same kV and mAs) since output is very different.…”

Section: Introductionmentioning

confidence: 99%

“…It is hypothesized that image quality and fiducial visibility will be different between the two versions (for the same kV and mAs) since output is very different. The previous work did not assess image quality differences from the two configurations [12]. Therefore, there is need for a controlled comparison of image quality between the versions.…”

Section: Introductionmentioning

confidence: 99%

“…• Compare image quality between the two Radixact configurations to determine the difference in image quality since source-to-detector distances are different [12].…”

Section: Introductionmentioning

confidence: 99%

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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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Performance evaluation of online motion synchronizing systems for patient-specific respiratory movements with helical tomotherapy

Chan¹,

Fok²,

Chiu³

et al. 2022

Biomed. Phys. Eng. Express

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Background and Purpose:The introduction of online motion synchronizing system on helical tomotherapy paves way for robust motion tracking. A recent upgrade launches modifications on both hardware and software of the kV tracking system. An evaluation on the kV subsystems, prior(Version1) and post upgrade(Version2), was performed to compare tracking accuracy by means of fiducial tracking error and resulted root-mean-square (RMS). Impacts influenced by various patient-specific breathing pattern regularities and target movements were also investigated to refine motion tracking error estimations upon future selection of possible candidates. Materials and Methods:Respiratory patterns from twenty-five lung cases were imported individually into a commercial dynamic platform model. Situating a phantom implanted with gold fiducial markers on the platform, superior-inferior(SI) movements of corresponding targets were simulated. Each case was delivered via an identical treatment plan in Version1 and was repeated in Version2. Motion tracking accuracy, by means of discrepancies between subsystem predicted model and raw data motion recorded in patient CT simulation, was analyzed statistically. Wilcoxon signed ranked test was employed to evaluate the difference in tracking error range between the two versions. Statistical model was fitted to inspect the dependence of internal target movement towards fiducial tracking errors. Results:A small difference of ±1 mm was exhibited in 99% of fiducial tracking errors for all cases experimented under both versions. RMS errors were all below 0.5 mm. Version2 demonstrated a greater extremity in fiducial tracking error (p=0.04). A positive correlation was depicted between internal target amplitudes and 95% interval of fiducial tracking errors (p< 0.02). Overall, irregular respiratory patterns tended to have greater fiducial tracking errors. Conclusions:The excellent tracking performance in both kV subsystem versions offers motion compensations benefits, yet Version1 outperformed Version2 in fiducial tracking accuracy. It is noticeable that greater magnitude in internal target movement and irregular breathing patterns yield greater tracking error.

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Technical note: On the impact of the kV imaging configuration on doses from planar images during motion‐synchronized treatments on Radixact®

Cited by 3 publications

References 7 publications

The impact of the ClearRT™ upgrade on target motion tracking accuracy in Radixact® Synchrony® lung treatments

The impact of the ClearRT™ upgrade on target motion tracking accuracy in Radixact® Synchrony® lung treatments

Fiducial visibility on planar images during motion-synchronized tomotherapy treatments

Performance evaluation of online motion synchronizing systems for patient-specific respiratory movements with helical tomotherapy

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