Visualization of air and metal inhomogeneities in phantoms irradiated by carbon ion beams using prompt secondary ions

Gaa, T.; Reinhart, Merle; Hartmann, B.; Jakůbek, J.; Soukup, P; Jäkel, Oliver; Martišíková, M.

doi:10.1016/j.ejmp.2017.05.055

Cited by 10 publications

(11 citation statements)

References 30 publications

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“…Compared to the reference fraction, the secondary-ion emission profile is higher in front of the air cavity, lower at the depth of the cavity and higher behind the cavity. These observations are consistent with ( 11 ), due to the expected effect of the air cavity on the primary carbon ions and the charged fragments: the carbon ions penetrate deeper when they cross a low-density region such as the air cavity, leading to a shift of the emission profile towards deeper positions, which explains the larger amount of detected fragments behind the air cavity. In the air cavity itself, fewer fragments are produced, leading to a dip in the secondary-ion emission profile at the depth of the air cavity.…”

Section: Resultssupporting

confidence: 90%

“…A dataset equivalent to eight mini-trackers with an active area of 2 cm 2 each was used to detect and localize an air cavity of 2 mm thickness and 80 × 80 mm 2 transverse area from different detection angles relative to the beam axis. The size of the investigated inter-fractional change is considerably smaller than in previously published studies that used inserts with a thickness of 10 mm ( 11 ), 28.5 mm ( 29 ) and 28 mm ( 30 ).…”

Section: Discussionmentioning

confidence: 69%

“…Over the years, secondary-ions detection angles ranging from 0° (7,8) to 90° (9) were investigated. Most of the recently published experiments have been measured at either 30° (10,11), or at 60°and 90° (12)(13)(14). The first results of a clinical study were taken at a composite detection angle of 60°(horizontal plane) and 30°(vertical plane) relative to the beam direction (15).…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Suitable Detection Angles for Carbon-Ion Radiotherapy Monitoring in Depth by Means of Secondary-Ion Tracking

et al. 2021

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The dose conformity of carbon-ion beam radiotherapy, which allows the reduction of the dose deposition in healthy tissue and the escalation of the dose to the tumor, is associated with a high sensitivity to anatomical changes during and between treatment irradiations. Thus, the monitoring of inter-fractional anatomical changes is crucial to ensure the dose conformity, to potentially reduce the size of the safety margins around the tumor and ultimately to reduce the irradiation of healthy tissue. To do so, monitoring methods of carbon-ion radiotherapy in depth using secondary-ion tracking are being investigated. In this work, the detection and localization of a small air cavity of 2 mm thickness were investigated at different detection angles of the mini-tracker relative to the beam axis. The experiments were conducted with a PMMA head phantom at the Heidelberg Ion-Beam Therapy Center (HIT) in Germany. In a clinic-like irradiation of a single field of 3 Gy (RBE), secondary-ion emission profiles were measured by a 2 cm2 mini-tracker composed of two silicon pixel detectors. Two positions of the cavity in the head phantom were studied: in front and in the middle of the tumor volume. The significance of the cavity detection was found to be increased at smaller detection angles, while the accuracy of the cavity localization was improved at larger detection angles. Detection angles of 20° – 30° were found to be a good compromise for accessing both, the detectability and the position of the air cavity along the depth in the head of a patient.

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Section: Resultssupporting

confidence: 90%

Section: Discussionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

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Investigation of Suitable Detection Angles for Carbon-Ion Radiotherapy Monitoring in Depth by Means of Secondary-Ion Tracking

et al. 2021

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“…In contrast to previous Timepix detector generations (such as Timepix1 used in [9][10][11]), Timepix3 allows a dead-time-free data-driven data acquisition. Moreover, the position, energy, and time-of -arrival of single charged particles can be measured simultaneously.…”

Section: Mini-trackermentioning

confidence: 99%

“…In this work, carbon‐ion beam range differences of 1.3 mm were detectable, and beam‐width variations were measured with a precision of 0.9 mm. Follow‐up studies showed the potential of this monitoring method in heterogeneous phantoms, where cavities of 10‐mm‐thick air, 1‐mm thick stainless steel, or 28.5‐mm thick adipose tissue were detectable, but still considering single monoenergetic pencil beams centered on the isocenter 10,11 . Due to the long dead‐time of the first generation of the Timepix detector, it could not be evaluated in realistic clinical conditions with scanned pencil beams and at realistic dose levels.…”

Section: Introductionmentioning

confidence: 99%

Detecting perturbations of a radiation field inside a head‐sized phantom exposed to therapeutic carbon‐ion beams through charged‐fragment tracking

et al. 2022

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Purpose Noninvasive methods to monitor carbon‐ion beams in patients are desired to fully exploit the advantages of carbon‐ion radiotherapy. Prompt secondary ions produced in nuclear fragmentations of carbon ions are of particular interest for monitoring purposes as they can escape the patient and thus be detected and tracked to measure the radiation field in the irradiated object. This study aims to evaluate the performance of secondary‐ion tracking to detect, visualize, and localize an internal air cavity used to mimic inter‐fractional changes in the patient anatomy at different depths along the beam axis. Methods In this work, a homogeneous head phantom was irradiated with a realistic carbon‐ion treatment plan with a typical prescribed fraction dose of 3 Gy(RBE). Secondary ions were detected by a mini‐tracker with an active area of 2 cm2, based on the Timepix3 semiconductor pixel detector technology. The mini‐tracker was placed 120 mm behind the center of the target at an angle of 30 degrees with respect to the beam axis. To assess the performance of the developed method, a 2‐mm thick air cavity was inserted in the head phantom at several depths: in front of as well as at the entrance, in the middle, and at the distal end of the target volume. Different reconstruction methods of secondary‐ion emission profile were studied using the FLUKA Monte Carlo simulation package. The perturbations in the emission profiles caused by the air cavity were analyzed to detect the presence of the air cavity and localize its position. Results The perturbations in the radiation field mimicked by the 2‐mm thick cavity were found to be significant. A detection significance of at least three standard deviations in terms of spatial distribution of the measured tracks was found for all investigated cavity depths, while the highest significance (six standard deviations) was obtained when the cavity was located upstream of the tumor. For a tracker with an eight‐fold sensitive area, the detection significance rose to at least nine standard deviations and up to 17 standard deviations, respectively. The cavity could be detected at all depths and its position measured within 6.5 ± 1.4 mm, which is sufficient for the targeted clinical performance of 10 mm. Conclusion The presented systematic study concerning the detection and localization of small inter‐fractional structure changes in a realistic clinical setting demonstrates that secondary ions carry a large amount of information on the internal structure of the irradiated object and are thus attractive to be further studied for noninvasive monitoring of carbon‐ion treatments.

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Detection of an internal density change in an anthropomorphic head phantom via tracking of charged nuclear fragments in carbon‐ion radiotherapy

Schweins,

Kirchgässner,

Ochoa‐Parra

et al. 2024

Medical Physics

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BackgroundCarbon‐ion radiotherapy provides steep dose gradients that allow the simultaneous application of high tumor doses as well as the sparing of healthy tissue and radio‐sensitive organs. However, even small anatomical changes may have a severe impact on the dose distribution because of the finite range of ion beams.PurposeAn in‐vivo monitoring method based on secondary‐ion emission could potentially provide feedback about the patient anatomy and thus the treatment quality. This work aims to prove that a clinically relevant anatomical change in an anthropomorphic head phantom may be detected via charged‐fragment tracking during a treatment fraction.MethodsA clinically representative carbon‐ion treatment plan was created for a skull‐base tumor in an anthropomorphic head phantom. In order to imitate an inter‐fractional anatomical change — for example, through tissue swelling or mucous accumulation — a piece of silicone was inserted into the nasopharynx. Fragment distributions with and without the silicone insert were subsequently acquired with a mini‐tracker made of four hybrid silicon pixel detectors. Experimental irradiations were carried out at the Heidelberg Ion Beam Therapy Centre (HIT, Germany). FLUKA Monte Carlo simulations were performed to support the interpretation of the experimental results.ResultsIt was found that the silicone causes a significant change in the fragment emission that was clearly distinguishable from statistical fluctuations and setup uncertainties. Two regions of fragment loss were observed upstream and downstream of the silicone with similar amplitude in both the measurement and the simulation. Monte Carlo simulations showed that the observed signature is a consequence of a complex interplay of fragment production, scattering, and absorption.ConclusionsCarbon‐ion therapy monitoring with charged nuclear fragments was shown to be capable of detecting clinically relevant density changes in an anthropomorphic head phantom under realistic clinic‐like conditions. The complexity of the observed signal requires the development of advanced analysis techniques and underscores the importance of Monte Carlo simulations. The findings have strong implications for the ongoing InViMo clinical trial at HIT, which investigates the feasibility of secondary‐ion monitoring for skull‐base cancer patients.

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Visualization of air and metal inhomogeneities in phantoms irradiated by carbon ion beams using prompt secondary ions

Cited by 10 publications

References 30 publications

Investigation of Suitable Detection Angles for Carbon-Ion Radiotherapy Monitoring in Depth by Means of Secondary-Ion Tracking

Investigation of Suitable Detection Angles for Carbon-Ion Radiotherapy Monitoring in Depth by Means of Secondary-Ion Tracking

Detecting perturbations of a radiation field inside a head‐sized phantom exposed to therapeutic carbon‐ion beams through charged‐fragment tracking

Detection of an internal density change in an anthropomorphic head phantom via tracking of charged nuclear fragments in carbon‐ion radiotherapy

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