A potential method for<i>in vivo</i>range verification in proton therapy treatment

Lu, Hsiao‐Ming

doi:10.1088/0031-9155/53/5/016

Cited by 62 publications

(87 citation statements)

References 18 publications

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“…This simplified approach may be less accurate for WET computation, but has the advantage that the PDRs can be computed quickly. Regardless of the approach, techniques to experimentally validate calculated WET values include proton radiography, (12) proton range probe, (27) or an in vivo dosimetry method (28) …”

Section: Discussionmentioning

confidence: 99%

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

Wang

Yin

Zhang

et al. 2016

J Applied Clin Med Phys

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The aim of this work is to demonstrate the feasibility of using water‐equivalent thickness (WET) and virtual proton depth radiographs (PDRs) of intensity corrected cone‐beam computed tomography (CBCT) to detect anatomical change and patient setup error to trigger adaptive head and neck proton therapy. The planning CT (pCT) and linear accelerator (linac) equipped CBCTs acquired weekly during treatment of a head and neck patient were used in this study. Deformable image registration (DIR) was used to register each CBCT with the pCT and map Hounsfield units (HUs) from the planning CT (pCT) onto the daily CBCT. The deformed pCT is referred as the corrected CBCT (cCBCT). Two dimensional virtual lateral PDRs were generated using a ray‐tracing technique to project the cumulative WET from a virtual source through the cCBCT and the pCT onto a virtual plane. The PDRs were used to identify anatomic regions with large variations in the proton range between the cCBCT and pCT using a threshold of 3 mm relative difference of WET and 3 mm search radius criteria. The relationship between PDR differences and dose distribution is established. Due to weight change and tumor response during treatment, large variations in WETs were observed in the relative PDRs which corresponded spatially with an increase in the number of failing points within the GTV, especially in the pharynx area. Failing points were also evident near the posterior neck due to setup variations. Differences in PDRs correlated spatially to differences in the distal dose distribution in the beam's eye view. Virtual PDRs generated from volumetric data, such as pCTs or CBCTs, are potentially a useful quantitative tool in proton therapy. PDRs and WET analysis may be used to detect anatomical change from baseline during treatment and trigger further analysis in adaptive proton therapy.PACS number(s): 87.55‐x, 87.55.‐D, 87.57.Q‐

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Section: Discussionmentioning

confidence: 99%

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

Wang

Yin

Zhang

et al. 2016

J Applied Clin Med Phys

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“…By comparing the WEPL from the actual treatment session to the WEPL from the first day of treatment one can verify if the total cumulated WEPL changes during the course of the treatment have become unacceptable for continuing use of the same treatment plan. The effectiveness of this approach should be first validated against an independent technique for range verification such as prompt gamma camera measurement, 19 , 20 the PET method, (7 – 9) proton radiography, (10) or the in vivo time resolved dose rate method 11 , 12 , 13 , 14 , 15 …”

Section: Discussionmentioning

confidence: 99%

“…It is obvious that using CBCT for detecting any relative changes in patient WEPL along the treatment beam path does not enable direct verification of the proton beam range; however, it can be used to indirectly derive the beam range correction for this particular treatment session. That is because one can quantify the needed range correction by relating the measured relative changes in the WEPL computed using CBCT data to the already base‐lined WEPL from previous treatment sessions where the beam range was actually verified by the PET method 7 , 9 or other in vivo range verification techniques like time resolved dosimetry 12 , 13 , 14 , 15 …”

Section: Introductionmentioning

confidence: 99%

Using CBCT for pretreatment range check in proton therapy: a phantom study for prostate treatment by anterior–posterior beam

Bentefour

Both

Tang

et al. 2015

J Applied Clin Med Phys

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This study explores the potential of cone‐beam computed tomography (CBCT) for monitoring relative beam range variations due to daily changes in patient anatomy for prostate treatment by anterior proton beams. CBCT was used to image an anthropomorphic pelvic phantom, in eight sessions on eight different days. In each session, the phantom was scanned twice, first at a standard position as determined by the room lasers, and then after it was shifted by 10 mm translation randomly along one of the X, Y, or Z directions. The filling of the phantom bladder with water was not refreshed from day to day, inducing gradual change of the water‐equivalent path length (WEPL) across the bladder. MIMvista (MIM) software was used to perform image registration and re‐alignment of all the scans with the scan from the first session. The XiO treatment planning system was used to perform data analysis. It was found that, although the Hounsfield unit numbers in CBCT have substantially larger fluctuations than those in diagnostic CT, CBCT datasets taken for daily patient positioning could potentially be used to monitor changes in patient anatomy. The reproducibility of the WEPL, computed using CBCT along anterior–posterior (AP) paths across and around the phantom prostate, over a volume of 360 cc, is sufficient for detecting daily WEPL variations that are equal to or larger than 3 mm. This result also applies to CBCT scans of the phantom after it is randomly shifted from the treatment position by 10 mm. limiting the interest to WEPL variation over a specific path within the same CBCT slice, one can detect WEPL variation smaller than 1 mm. That is the case when using CBCT for tracking daily change of the WEPL across the phantom bladder that was induced by spontaneous change in the bladder filling due to evaporation. In summary, the phantom study suggests that CBCT can be used for monitoring day to day WEPL variations in a patient. The method can detect WEPL variation equal to or greater than 3 mm. The study calls for further investigation using the CBCT data from real patients. If confirmed with real patients' data, CBCT could become, in addition to patient setup, a standard tool for proton therapy pretreatment beam range check.PACS number: 87.55.Tm

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“…Therefore, Melancon et al 6 proposed a liquid scintillation detector to be inserted into the rectum, combined with a wedge compensator to measure the range before treatment. Lu 7 proposed to use a time-dependent dose consistent with a passively scattered beam. These devices are under development and may be suited for body sites where a detector can be inserted; such a device would not be feasible for lung or abdominal tumors.…”

Section: Introductionmentioning

confidence: 99%

Proton radiography and fluoroscopy of lung tumors: A Monte Carlo study using patient‐specific 4DCT phantoms

Han

Chen

2011

Medical Physics

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Purpose: Monte Carlo methods are used to simulate and optimize a time-resolved proton range telescope ͑TRRT͒ in localization of intrafractional and interfractional motions of lung tumor and in quantification of proton range variations. Methods: The Monte Carlo N-Particle eXtended ͑MCNPX͒ code with a particle tracking feature was employed to evaluate the TRRT performance, especially in visualizing and quantifying proton range variations during respiration. Protons of 230 MeV were tracked one by one as they pass through position detectors, patient 4DCT phantom, and finally scintillator detectors that measured residual ranges. The energy response of the scintillator telescope was investigated. Mass density and elemental composition of tissues were defined for 4DCT data. Results: Proton water equivalent length ͑WEL͒ was deduced by a reconstruction algorithm that incorporates linear proton track and lateral spatial discrimination to improve the image quality. 4DCT data for three patients were used to visualize and measure tumor motion and WEL variations. The tumor trajectories extracted from the WEL map were found to be within ϳ1 mm agreement with direct 4DCT measurement. Quantitative WEL variation studies showed that the proton radiograph is a good representation of WEL changes from entrance to distal of the target. Conclusions: MCNPX simulation results showed that TRRT can accurately track the motion of the tumor and detect the WEL variations. Image quality was optimized by choosing proton energy, testing parameters of image reconstruction algorithm, and comparing to ground truth 4DCT. The future study will demonstrate the feasibility of using the time resolved proton radiography as an imaging tool for proton treatments of lung tumors.

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A potential method forin vivorange verification in proton therapy treatment

Cited by 62 publications

References 18 publications

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

Using CBCT for pretreatment range check in proton therapy: a phantom study for prostate treatment by anterior–posterior beam

Proton radiography and fluoroscopy of lung tumors: A Monte Carlo study using patient‐specific 4DCT phantoms

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