Review and performance of the Dose Profiler, a particle therapy treatments online monitor

In-beam PET treatment monitoring of carbon therapy patients: Results of a clinical trial at CNAO

PURPOSE

Carbon ion therapy treatments can be monitored non-invasively with in-beam Positron Emission Tomography (PET). At CNAO the INSIDE in-beam PET scanner has been used in a clinical trial (NCT03662373) to monitor cancer treatments with proton and carbon therapy. In this work we present the analysis results of carbon therapy data, acquired during the first phase of the clinical trial, analyzing data of nine patients treated at CNAO for various malignant tumors in the head-and-neck region.

MATERIALS AND METHODS

The patient group contained two patients requiring replanning, and seven patients without replanning, based on established protocols. For each patient the PET images acquired along the course of treatment were compared with a reference, applying two analysis methods: the beam-eye-view (BEV) method and the γ-index analysis. Time trends in several parameters were investigated, as well as the agreement with control CTs, if available.

RESULTS

Regarding the BEV-method, the average sigma value σ was 3.7 mm of range difference distributions for patients without changes (sensitivity of the INSIDE detector). The 3D-information obtained from the BEV analysis was partly in agreement with what was observed in the control CT. The data quality and quantity was insufficient for a definite interpretation of the time trends.

CONCLUSION

We analyzed carbon therapy data acquired with the INSIDE in-beam PET detector using two analysis methods. The data allowed to evaluate sensitivity of the INSIDE detector for carbon therapy and to make several recommendations for the future.

An in-vivo treatment monitoring system for ion-beam radiotherapy based on 28 Timepix3 detectors

Ion-beam radiotherapy is an advanced cancer treatment modality offering steep dose gradients and a high biological effectiveness. These gradients make the therapy vulnerable to patient-setup and anatomical changes between treatment fractions, which may go unnoticed. Charged fragments from nuclear interactions of the ion beam with the patient tissue may carry information about the treatment quality. Currently, the fragments escape the patient undetected. Inter-fractional in-vivo treatment monitoring based on these charged nuclear fragments could make ion-beam therapy safer and more efficient. We developed an ion-beam monitoring system based on 28 hybrid silicon pixel detectors (Timepix3) to measure the distribution of fragment origins in three dimensions. The system design choices as well as the ion-beam monitoring performance measurements are presented in this manuscript. A spatial resolution of 4 mm along the beam axis was achieved for the measurement of individual fragment origins. Beam-range shifts of1.5 mm were identified in a clinically realistic treatment scenario with an anthropomorphic head phantom. The monitoring system is currently being used in a prospective clinical trial at the Heidelberg Ion Beam Therapy Centre for head-and-neck as well as central nervous system cancer patients.

Feasibility of the J-PET to monitor the range of therapeutic proton beams

PURPOSE

The aim of this work is to investigate the feasibility of the Jagiellonian Positron Emission Tomography (J-PET) scanner for intra-treatment proton beam range monitoring.

METHODS

The Monte Carlo simulation studies with GATE and PET image reconstruction with CASToR were performed in order to compare six J-PET scanner geometries. We simulated proton irradiation of a PMMA phantom with a Single Pencil Beam (SPB) and Spread-Out Bragg Peak (SOBP) of various ranges. The sensitivity and precision of each scanner were calculated, and considering the setup's cost-effectiveness, we indicated potentially optimal geometries for the J-PET scanner prototype dedicated to the proton beam range assessment.

RESULTS

The investigations indicate that the double-layer cylindrical and triple-layer double-head configurations are the most promising for clinical application. We found that the scanner sensitivity is of the order of 10-5 coincidences per primary proton, while the precision of the range assessment for both SPB and SOBP irradiation plans was found below 1 mm. Among the scanners with the same number of detector modules, the best results are found for the triple-layer dual-head geometry. The results indicate that the double-layer cylindrical and triple-layer double-head configurations are the most promising for the clinical application, CONCLUSIONS:: We performed simulation studies demonstrating that the feasibility of the J-PET detector for PET-based proton beam therapy range monitoring is possible with reasonable sensitivity and precision enabling its pre-clinical tests in the clinical proton therapy environment. Considering the sensitivity, precision and cost-effectiveness, the double-layer cylindrical and triple-layer dual-head J-PET geometry configurations seem promising for future clinical application.

Few-seconds range verification with short-lived positron emitters in carbon ion therapy

In-beam PET (Positron Emission Tomography) is one of the most precise techniques for in-vivo range monitoring in hadron therapy. Our objective was to demonstrate the feasibility of a short irradiation run for range verification before a carbon-ion treatment. To do so a PMMA target was irradiated with a 220 MeV/u carbon-ion beam and annihilation coincidences from short-lived positron emitters were acquired after irradiations lasting 0.6 s. The experiments were performed at the synchrotron-based facility CNAO (Italian National Center of Oncological Hadrontherapy) by using the INSIDE in-beam PET detector. The results show that, with 3·107 carbon ions, the reconstructed positron emitting nuclei distribution is in good agreement with the predictions of a detailed FLUKA Monte Carlo study. Moreover, the radio-nuclei production is sufficiently abundant to determine the average ion beam range with a σ of 1 mm with a 6 s measurement of the activity distribution. Since the data were acquired when the beam was off, the proposed rapid calibration method can be applied to hadron beams extracted from accelerators with very different time structures.

In-vivo range verification analysis with in-beam PET data for patients treated with proton therapy at CNAO

Morphological changes that may arise through a treatment course are probably one of the most significant sources of range uncertainty in proton therapy. Non-invasive in-vivo treatment monitoring is useful to increase treatment quality. The INSIDE in-beam Positron Emission Tomography (PET) scanner performs in-vivo range monitoring in proton and carbon therapy treatments at the National Center of Oncological Hadrontherapy (CNAO). It is currently in a clinical trial (ID: NCT03662373) and has acquired in-beam PET data during the treatment of various patients. In this work we analyze the in-beam PET (IB-PET) data of eight patients treated with proton therapy at CNAO. The goal of the analysis is twofold. First, we assess the level of experimental fluctuations in inter-fractional range differences (sensitivity) of the INSIDE PET system by studying patients without morphological changes. Second, we use the obtained results to see whether we can observe anomalously large range variations in patients where morphological changes have occurred. The sensitivity of the INSIDE IB-PET scanner was quantified as the standard deviation of the range difference distributions observed for six patients that did not show morphological changes. Inter-fractional range variations with respect to a reference distribution were estimated using the Most-Likely-Shift (MLS) method. To establish the efficacy of this method, we made a comparison with the Beam’s Eye View (BEV) method. For patients showing no morphological changes in the control CT the average range variation standard deviation was found to be 2.5 mm with the MLS method and 2.3 mm with the BEV method. On the other hand, for patients where some small anatomical changes occurred, we found larger standard deviation values. In these patients we evaluated where anomalous range differences were found and compared them with the CT. We found that the identified regions were mostly in agreement with the morphological changes seen in the CT scan.

Hadron Therapy Achievements and Challenges: The CNAO Experience

Protons and carbon ions (hadrons) have useful properties for the treatments of patients affected by oncological pathologies. They are more precise than conventional X-rays and possess radiobiological characteristics suited for treating radio-resistant or inoperable tumours. This paper gives an overview of the status of hadron therapy around the world. It focusses on the Italian National Centre for Oncological Hadron therapy (CNAO), introducing operation procedures, system performance, expansion projects, methodologies and modelling to build individualized treatments. There is growing evidence that supports safety and effectiveness of hadron therapy for a variety of clinical situations. However, there is still a lack of high-level evidence directly comparing hadron therapy with modern conventional radiotherapy techniques. The results give an overview of pre-clinical and clinical research studies and of the treatments of 3700 patients performed at CNAO. The success and development of hadron therapy is strongly associated with the creation of networks among hadron therapy facilities, clinics, universities and research institutions. These networks guarantee the growth of cultural knowledge on hadron therapy, favour the efficient recruitment of patients and present available competences for R&D (Research and Development) programmes.

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

PURPOSE

Non-invasive 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 (6 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 9 standard deviations, and up to 17 standard deviations respectively. The cavity could be detected at all depths and its position measured within 6.5 mm ± 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 non-invasive monitoring of carbon-ion treatments. This article is protected by copyright. All rights reserved.

Radioactive Beams for Image-Guided Particle Therapy: The BARB Experiment at GSI

Several techniques are under development for image-guidance in particle therapy. Positron (β⁺) emission tomography (PET) is in use since many years, because accelerated ions generate positron-emitting isotopes by nuclear fragmentation in the human body. In heavy ion therapy, a major part of the PET signals is produced by β⁺-emitters generated via projectile fragmentation. A much higher intensity for the PET signal can be obtained using β⁺-radioactive beams directly for treatment. This idea has always been hampered by the low intensity of the secondary beams, produced by fragmentation of the primary, stable beams. With the intensity upgrade of the SIS-18 synchrotron and the isotopic separation with the fragment separator FRS in the FAIR-phase-0 in Darmstadt, it is now possible to reach radioactive ion beams with sufficient intensity to treat a tumor in small animals. This was the motivation of the BARB (Biomedical Applications of Radioactive ion Beams) experiment that is ongoing at GSI in Darmstadt. This paper will present the plans and instruments developed by the BARB collaboration for testing the use of radioactive beams in cancer therapy.

Application of Carbon Ion and Its Sensitizing Agent in Cancer Therapy: A Systematic Review

Carbon ion radiation therapy (CIRT) is the most advanced radiation therapy (RT) available and offers new opportunities to improve cancer treatment and research. CIRT has a unique physical and biological advantage that allow them to kill tumor cells more accurately and intensively. So far, CIRT has been used in almost all types of malignant tumors, and showed good feasibility, safety and acceptable toxicity, indicating that CIRT has a wide range of development and application prospects. In addition, in order to improve the biological effect of CIRT, scientists are also trying to investigate related sensitizing agents to enhance the killing ability of tumor cells, which has attracted extensive attention. In this review, we tried to systematically review the rationale, advantages and problems, the clinical applications and the sensitizing agents of the CIRT. At the same time, the prospects of the CIRT in were prospected. We hope that this review will help researchers interested in CIRT, sensitizing agents, and radiotherapy to understand their magic more systematically and faster, and provide data reference and support for bioanalysis, clinical medicine, radiotherapy, heavy ion therapy, and nanoparticle diagnostics.

Monitoring Carbon Ion Beams Transverse Position Detecting Charged Secondary Fragments: Results From Patient Treatment Performed at CNAO

Particle therapy in which deep seated tumours are treated using ¹²C ions (Carbon Ions RadioTherapy or CIRT) exploits the high conformity in the dose release, the high relative biological effectiveness and low oxygen enhancement ratio of such projectiles. The advantages of CIRT are driving a rapid increase in the number of centres that are trying to implement such technique. To fully profit from the ballistic precision achievable in delivering the dose to the target volume an online range verification system would be needed, but currently missing. The ¹²C ions beams range could only be monitored by looking at the secondary radiation emitted by the primary beam interaction with the patient tissues and no technical solution capable of the needed precision has been adopted in the clinical centres yet. The detection of charged secondary fragments, mainly protons, emitted by the patient is a promising approach, and is currently being explored in clinical trials at CNAO. Charged particles are easy to detect and can be back-tracked to the emission point with high efficiency in an almost background-free environment. These fragments are the product of projectiles fragmentation, and are hence mainly produced along the beam path inside the patient. This experimental signature can be used to monitor the beam position in the plane orthogonal to its flight direction, providing an online feedback to the beam transverse position monitor chambers used in the clinical centres. This information could be used to cross-check, validate and calibrate, whenever needed, the information provided by the ion chambers already implemented in most clinical centres as beam control detectors. In this paper we study the feasibility of such strategy in the clinical routine, analysing the data collected during the clinical trial performed at the CNAO facility on patients treated using ¹²C ions and monitored using the Dose Profiler (DP) detector developed within the INSIDE project. On the basis of the data collected monitoring three patients, the technique potential and limitations will be discussed.

Inter-fractional monitoring of [Formula: see text]C ions treatments: results from a clinical trial at the CNAO facility

The high dose conformity and healthy tissue sparing achievable in Particle Therapy when using C ions calls for safety factors in treatment planning, to prevent the tumor under-dosage related to the possible occurrence of inter-fractional morphological changes during a treatment. This limitation could be overcome by a range monitor, still missing in clinical routine, capable of providing on-line feedback. The Dose Profiler (DP) is a detector developed within the INnovative Solution for In-beam Dosimetry in hadronthErapy (INSIDE) collaboration for the monitoring of carbon ion treatments at the CNAO facility (Centro Nazionale di Adroterapia Oncologica) exploiting the detection of charged secondary fragments that escape from the patient. The DP capability to detect inter-fractional changes is demonstrated by comparing the obtained fragment emission maps in different fractions of the treatments enrolled in the first ever clinical trial of such a monitoring system, performed at CNAO. The case of a CNAO patient that underwent a significant morphological change is presented in detail, focusing on the implications that can be drawn for the achievable inter-fractional monitoring DP sensitivity in real clinical conditions. The results have been cross-checked against a simulation study.

The 20th Gray lecture 2019: health and heavy ions

OBJECTIVE

Particle radiobiology has contributed new understanding of radiation safety and underlying mechanisms of action to radiation oncology for the treatment of cancer, and to planning of radiation protection for space travel. This manuscript will highlight the significance of precise physical and biologically effective dosimetry to this translational research for the benefit of human health.This review provides a brief snapshot of the evolving scientific basis for, and the complex current global status, and remaining challenges of hadron therapy for the treatment of cancer. The need for particle radiobiology for risk planning in return missions to the Moon, and exploratory deep-space missions to Mars and beyond are also discussed.

METHODS

Key lessons learned are summarized from an impressive collective literature published by an international cadre of multidisciplinary experts in particle physics, radiation chemistry, medical physics of imaging and treatment planning, molecular, cellular, tissue radiobiology, biology of microgravity and other stressors, theoretical modeling of biophysical data, and clinical results with accelerator-produced particle beams.

RESULTS

Research pioneers, many of whom were Nobel laureates, led the world in the discovery of ionizing radiations originating from the Earth and the Cosmos. Six radiation pioneers led the way to hadron therapy and the study of charged particles encountered in outer space travel. Worldwide about 250,000 patients have been treated for cancer, or other lesions such as arteriovenous malformations in the brain between 1954 and 2019 with charged particle radiotherapy, also known as hadron therapy. The majority of these patients (213,000) were treated with proton beams, but approximately 32,000 were treated with carbon ion radiotherapy. There are 3500 patients who have been treated with helium, pions, neon or other ions. There are currently 82 facilities operating to provide ion beam clinical treatments. Of these, only 13 facilities located in Asia and Europe are providing carbon ion beams for preclinical, clinical, and space research. There are also numerous particle physics accelerators worldwide capable of producing ion beams for research, but not currently focused on treating patients with ion beam therapy but are potentially available for preclinical and space research. Approximately, more than 550 individuals have traveled into Lower Earth Orbit (LEO) and beyond and returned to Earth.

CONCLUSION

Charged particle therapy with controlled beams of protons and carbon ions have significantly impacted targeted cancer therapy, eradicated tumors while sparing normal tissue toxicities, and reduced human suffering. These modalities still require further optimization and technical refinements to reduce cost but should be made available to everyone in need worldwide. The exploration of our Universe in space travel poses the potential risk of exposure to uncontrolled charged particles. However, approaches to shield and provide countermeasures to these potential radiation hazards in LEO have allowed an amazing number of discoveries currently without significant life-threatening medical consequences. More basic research with components of the Galactic Cosmic Radiation field are still required to assure safety involving space radiations and combined stressors with microgravity for exploratory deep space travel.

ADVANCES IN KNOWLEDGE

The collective knowledge garnered from the wealth of available published evidence obtained prior to particle radiation therapy, or to space flight, and the additional data gleaned from implementing both endeavors has provided many opportunities for heavy ions to promote human health.

Radioactive Beams in Particle Therapy: Past, Present, and Future

Heavy ion therapy can deliver high doses with high precision. However, image guidance is needed to reduce range uncertainty. Radioactive ions are potentially ideal projectiles for radiotherapy because their decay can be used to visualize the beam. Positron-emitting ions that can be visualized with PET imaging were already studied for therapy application during the pilot therapy project at the Lawrence Berkeley Laboratory, and later within the EULIMA EU project, the GSI therapy trial in Germany, MEDICIS at CERN, and at HIMAC in Japan. The results show that radioactive ion beams provide a large improvement in image quality and signal-to-noise ratio compared to stable ions. The main hindrance toward a clinical use of radioactive ions is their challenging production and the low intensities of the beams. New research projects are ongoing in Europe and Japan to assess the advantages of radioactive ion beams for therapy, to develop new detectors, and to build sources of radioactive ions for medical synchrotrons.

Latest developments in in-vivo imaging for proton therapy

Owing to the favorable physical and biological properties of swift ions in matter, their application to radiation therapy for highly selective cancer treatment is rapidly spreading worldwide. To date, over 90 ion therapy facilities are operational, predominantly with proton beams, and about the same amount is under construction or planning.Over the last decades, considerable developments have been achieved in accelerator technology, beam delivery and medical physics to enhance conformation of the dose delivery to complex shaped tumor volumes, with excellent sparing of surrounding normal tissue and critical organs. Nevertheless, full clinical exploitation of the ion beam advantages is still challenged, especially by uncertainties in the knowledge of the beam range in the actual patient anatomy during the fractionated course of treatment, thus calling for continued multidisciplinary research in this rapidly emerging field.This contribution will review latest developments aiming to image the patient with the same beam quality as for therapy prior to treatment, and to visualize in-vivo the treatment delivery by exploiting irradiation-induced physical emissions, with different level of maturity from proof-of-concept studies in phantoms and first in-silico studies up to clinical testing and initial clinical evaluation.