Feasibility study of range‐based registration using daily cone beam CT for intensity‐modulated proton therapy

Yao, Weiguang; Krasin, Matthew J.; Farr, J; Merchant, Thomas E.

doi:10.1002/mp.12760

Cited by 6 publications

(8 citation statements)

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“…34 Moreover, the type and energy of therapeutic radiation and the radiation delivery technique affect the required HU accuracy. 35 Based on our review of the literature, it appears the general strategy is to improve CBCT HU accuracy as close as possible to HU accuracy in helical CT to minimize errors in dose calculations. [36][37][38] In our work, 2D ASG combined with the GSS method provided better HU accuracy than the standard clinical CBCT protocol (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…However, it is challenging to define a target HU accuracy for CBCT‐based dose calculations; dose calculation errors depend on the cumulative effect of HU inaccuracy along the path of the therapeutic radiation, which is a function of multiple factors, such as location in the patient, tissue composition, patient size, and motion artifacts 34 . Moreover, the type and energy of therapeutic radiation and the radiation delivery technique affect the required HU accuracy 35 . Based on our review of the literature, it appears the general strategy is to improve CBCT HU accuracy as close as possible to HU accuracy in helical CT to minimize errors in dose calculations 36–38 .…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of scatter rejection and correction performance of 2D antiscatter grids in cone beam computed tomography

et al. 2021

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We have been investigating two-dimensional (2D) antiscatter grids (2D ASGs) to reduce scatter fluence and improve image quality in cone beam computed tomography (CBCT). In this work, two different aspects of 2D ASGs, their scatter rejection and correction capability, were investigated in CBCT experiments. To correct residual scatter transmitted through the 2D ASG, it was used as a scatter measurement device with a novel method: grid-based scatter sampling. Methods: Three focused 2D ASG prototypes with grid ratios of 8, 12, and 16 were developed for linac-mounted offset detector CBCT geometry. In the first phase, 2D ASGs were used as a scatter rejection device, and the effect of grid ratio on CT number accuracy and contrast-to-noise ratio (CNR) evaluated in CBCT images. In the second phase, a grid-based scatter sampling method which exploits the signal modulation characteristics of the 2D ASG's septal shadows to measure and correct residual scatter transmitted through the grid was implemented. To evaluate CT number accuracy, the percent change in CT numbers was measured by changing the phantom from head to pelvis size and configuration. Results: When 2D ASG was used as a scatter rejection device, CT number accuracy increased and the CT number variation due to change in phantom dimensions was reduced from 23% to 2-6%. A grid ratio of 16 yielded the lowest CT number variation. All three 2D ASGs yielded improvement in CNR, up to a factor of two in pelvis-sized phantoms. When 2D ASG prototypes were used for both scatter rejection and correction, CT number variations were reduced further, to 1.3-2.6%. In comparisons with a clinical CBCT system and a high-performance radiographic ASG, 2D ASG provided higher CT number accuracy under the same imaging conditions. Conclusions: When 2D ASG is used solely as a scatter rejection device, substantial improvement in CT number accuracy can be achieved by increasing the grid ratio. Two-dimensional ASGs also provided significant CNR improvement even at lower grid ratios. Two-dimensional ASGs used in conjunction with the grid-based scatter sampling method provided further improvement in CT number accuracy, irrespective of the grid ratio, while preserving 2D ASGs' capacity to improve CNR. The combined effect of scatter rejection and residual scatter correction by 2D ASG may accelerate implementation of new techniques in CBCT that require high quantitative accuracy, such as radiotherapy dose calculation and dual energy CBCT.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Evaluation of scatter rejection and correction performance of 2D antiscatter grids in cone beam computed tomography

et al. 2021

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“…Without scatter correction,one phantom study showed that the error of change of the calculated water-equivalent thickness (WET; the surrogate of proton range from daily CBCTs) was within 2 mm per 1 cm of phantom size change. 10 Proton range estimated by CBCT has been used in proton dose calculation 9,14 and proton range-based registration 10 but not in QACT frequency reduction.…”

Section: Introductionmentioning

confidence: 99%

“…An alternative is the use of proton range change in the CBCT from day 1, because we are more interested in the relative change of the range instead of the exact range itself. Without scatter correction, one phantom study showed that the error of change of the calculated water‐equivalent thickness (WET; the surrogate of proton range from daily CBCTs) was within 2 mm per 1 cm of phantom size change 10 . Proton range estimated by CBCT has been used in proton dose calculation 9,14 and proton range–based registration 10 but not in QACT frequency reduction.…”

Section: Introductionmentioning

confidence: 99%

“…Several groups have studied proton range by using cone-beam CT (CBCT) imaging of the patient on the couch. [8][9][10] The calculated proton range error for CBCT is high as a result of image quality and scatter 11,12 but can be mitigated by scatter correction 13,14 or generation of a synthetic CT. 15,16 An alternative is the use of proton range change in the CBCT from day 1, because we are more interested in the relative change of the range instead of the exact range itself. Without scatter correction,one phantom study showed that the error of change of the calculated water-equivalent thickness (WET; the surrogate of proton range from daily CBCTs) was within 2 mm per 1 cm of phantom size change.…”

Section: Introductionmentioning

confidence: 99%

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Use of CBCT plus plan robustness for reducing QACT frequency in intensity‐modulated proton therapy: Head‐and‐neck cases

et al. 2022

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Purpose Anatomic variation has a significant dosimetric impact in intensity‐modulated proton therapy. Weekly or biweekly computed tomography (CT) scans, called quality assurance CTs (QACTs), are used to monitor anatomic and resultant dose changes to determine whether adaptive plans are needed. Frequent CT scans result in unwanted QACT dose and increased clinical workloads. This study proposed utilizing patient setup cone‐beam CTs (CBCTs) and treatment plan robustness to reduce the frequency of QACTs. Methods We retrospectively analyzed data from 27 patients with head‐and‐neck cancer, including 594 CBCTs, 136 QACTs, and 19 adaptive plans. For each CBCT, water‐equivalent thickness (WET) along the pencil‐beam path was calculated. For each treatment plan, the WET of the first‐day CBCT was used as the reference, and the mean WET changes (ΔWET) in each following CBCT was used as the surrogate of proton range change. Using CBCTs acquired prior to a QACT, we predicted the ΔWET on the QACT day by a linear regression model. The impact of range change on target dose was calculated as the predicted ΔWET weighted by the monitor units of each field. In addition, plan robustness was estimated from the robust dose‐volume histograms (DVHs) and combined with ΔWET to reduce QACT frequency. Robustness was estimated from the distance between the DVH curves of the nominal and worst scenarios. Results When the estimated mean ΔWET was <6.5 mm (or <7.5 mm if the robustness was >95%), the QACT could be skipped without missing any adaptive planning; otherwise a QACT was required. Overall, 41% of QACTs could be eliminated when ΔWET was <6.5 mm and 56% when ΔWET was <7.5 mm, and robustness was >95%. At least one QACT could have been omitted in 25 of the 27 cases under skipping thresholds at ΔWETs <7.5 mm and R > 95%. Conclusion This study suggests that the number of QACTs can be greatly reduced by calculating range change in patient setup CBCTs and can be further reduced by combining this information with analyses of plan robustness.

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Cone-Beam CT Images as an Indicator of QACT During Adaptive Proton Therapy of Extremity Sarcomas

Biswal,

Zhang,

Nichols

et al. 2024

International Journal of Particle Therapy

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Feasibility study of range‐based registration using daily cone beam CT for intensity‐modulated proton therapy

Abstract: Range-based registration can efficiently mitigate range deviation due to patient positioning and anatomical changes. It can shorten patient positioning time and reduce the patient's dose from CBCT.

Cited by 6 publications

References 43 publications

Evaluation of scatter rejection and correction performance of 2D antiscatter grids in cone beam computed tomography

Evaluation of scatter rejection and correction performance of 2D antiscatter grids in cone beam computed tomography

Use of CBCT plus plan robustness for reducing QACT frequency in intensity‐modulated proton therapy: Head‐and‐neck cases

Cone-Beam CT Images as an Indicator of QACT During Adaptive Proton Therapy of Extremity Sarcomas

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