proton detection
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Léčebná strategie u nádorů jícnu se kontinuálně vyvíjí a radioterapie v ní má nezastupitelné místo. Rostoucí dostupnost protonové radioterapie přináší aktuální otázku, jaký je její reálný benefit. Řada okolností - více indikačních oblastí, nejednotné dávkování, málo ověřený benefit dávkové eskalace a nejednotné určování cílových objemů - odpověď zásadně komplikuje. Dozimetrie protonové radioterapie má ve srovnání s konvenční fotonovou radioterapií výhody jednoznačné a přesvědčivé. Otázka manifestace dozimetrických výhod v klinice byla zatím řešena převážně na malých retrospektivně hodnocených souborech. U trimodální terapie (chemoradioterapie + chirurgický výkon) bylo nutné vytvořit speciální nástroje hodnocení (TTB - total toxicity burden a POC - perioperative complications). V terénu značně nehomogenních souborů a velké dávkové variability se u protonové radioterapie ve srovnání s konvenční radioterapií daří prokazovat snížení toxicity. Formou randomizované studie byl benefit protonové radioterapie prokázán pouze jednou, a to v kontextu trimodální terapie. Benefit také spočívá v signifikantním snížení toxicity. Další randomizované studie probíhají. Otázka se dále komplikuje rozšiřováním technik scanningu, zatímco dosavadní výsledky vycházejí z technik scatteringových. Současné užití protonové radioterapie u nádorů jícnu je zatím podloženo evidencí nižší toxicity. Evidence dalších výhod protonové radioterapie je na úrovni klinického výzkumu a to za situace, kdy na stejné úrovni výzkumu jsou základní zásady radioterapie per se, zejm. dávková eskalace.
The treatment strategy for esophageal cancer evolves continuously, with radiotherapy having an irreplaceable position. The growing availability of proton beam therapy raises the timely question of its real benefit. The answer is substantially complicated by a number of circumstances - multiple areas of indication for use, inconsistent dosage strategies, little evidence of dose escalation benefit, and nonuniform determination of target volumes. The dosimetric advantages of proton beam therapy over conventional photon radiotherapy are clear and convincing. To date, the issue of demonstrating dosimetric advantages in the clinical practice has largely been addressed in small, retrospectively analyzed cohorts. For trimodal therapy (chemoradiotherapy + surgery), it was necessary to create special evaluation tools (TTB - total toxicity burden and POC - perioperative complications). In the setting of greatly inhomogeneous cohorts and large dose variability, it has been possible to demonstrate a reduction in toxicity with proton beam therapy compared to conventional radiotherapy. In the form of a randomized trial, the benefit of proton beam therapy has been demonstrated only once, and it was in the context of trimodal therapy. Here, the benefit also consisted in a significant reduction in toxicity. Additional randomized trials are being conducted. The issue is further complicated by expanding scanning techniques, whereas the results so far have been based on scattering techniques. The current use of proton beam therapy in esophageal cancer has so far provided evidence of lower toxicity. The evidence of other benefits of proton beam therapy is at the level of clinical research, with the basic principles of radiotherapy per se, particularly dose escalation, being at the same level of research.
Objective.Protons have advantageous dose distributions and are increasingly used in cancer therapy. At the depth of the Bragg peak range, protons produce a mixed radiation field consisting of low- and high-linear energy transfer (LET) components, the latter of which is characterized by an increased ionization density on the microscopic scale associated with increased biological effectiveness. Prediction of the yield and LET of primary and secondary charged particles at a certain depth in the patient is performed by Monte Carlo simulations but is difficult to verify experimentally.Approach.Here, the results of measurements performed with Timepix detector in the mixed radiation field produced by a therapeutic proton beam in water are presented and compared to Monte Carlo simulations. The unique capability of the detector to perform high-resolution single particle tracking and identification enhanced by artificial intelligence allowed to resolve the particle type and measure the deposited energy of each particle comprising the mixed radiation field. Based on the collected data, biologically important physics parameters, the LET of single protons and dose-averaged LET, were computed.Main results.An accuracy over 95% was achieved for proton recognition with a developed neural network model. For recognized protons, the measured LET spectra generally agree with the results of Monte Carlo simulations. The mean difference between dose-averaged LET values obtained from measurements and simulations is 17%. We observed a broad spectrum of LET values ranging from a fraction of keVμm-1to about 10 keVμm-1for most of the measurements performed in the mixed radiation fields.Significance.It has been demonstrated that the introduced measurement method provides experimental data for validation of LETDor LET spectra in any treatment planning system. The simplicity and accessibility of the presented methodology make it easy to be translated into a clinical routine in any proton therapy facility.
Primární synchronně zjištěný bilaterální karcinom prsu (PSBBC) je relativně vzácná klinická entita. Adjuvantní radioterapie je standardní součástí léčby nepokročilého nádoru prsu. Přestože je tato léčba nenahraditelná, je zatížena nežádoucími účinky, které u části pacientek mohou vést k neakceptovatelnému zvýšení kardiovaskulárního rizika a rizika rozvoje sekundární malignity. Kardiovaskulární komplikace prokazatelně snižují přežití pacientek s karcinomem prsu, a proto je nutná snaha o co největší redukci dávek na srdce a srdeční struktury. Protonová radioterapie, díky svým dozimetrickým výhodám, přináší možnost snížení dávky na rizikové orgány a současně umožňuje zachovat optimální pokrytí cílového objemu. Tato výhoda stoupá se zvětšujícím se rozsahem a rostoucí náročností cílového objemu, mezi které synchronně zjištěný bilaterální karcinom prsu jednoznačně patří.
Primary synchronously detected bilateral breast cancer (PSBBC) is a relatively rare clinical entity. The adjuvant radiotherapy is a standard part of non-metastatic breast cancer treatment. Despite the fact that this treatment is irreplaceable, it bears the burden of side effects, which may lead to an unacceptable increase of cardiovascular risk and risk of developing secondary malignancy in some patients. Cardiovascular complications have been shown to reduce the survival in breast cancer patients, and therefore efforts should be made to reduce the dose to the heart and cardiac structure as much as possible. Due to its dosimetric advantages, proton radiotherapy offers the possibility to reduce dose to organs at risk while maintaining optimal target volume coverage. This advantage grows with increasing extent and severity of the target volume, among which the synchronously detected bilateral breast cancer clearly belongs. We retrospectively attempted to evaluate the feasibility and safety of using proton radiotherapy in the treatment strategy of synchronously detected bilateral breast cancer.
Activation of detectors and phantoms used for commissioning and quality assurance of clinical proton beams may lead to radiation protection issues. Good understanding of the activation nuclide vectors involved is necessary to assess radiation risk for the personnel working with these devices on a daily basis or to fulfill legal requirements regarding transport of radioactive material and its release to the public. 11 devices and material samples were irradiated with a 220 MeV proton pencil beam (PBS, Proton Therapy Center, Prague). This study focuses on devices manufactured by IBA Dosimetry GmbH: MatriXX PT, PPC05, Stingray, Zebra, Lynx, a Blue Phantom rail and samples of RW3, PMMA, titanium, copper and carbon fibre plastic. Monitor units (MU) were monitored during delivery. Gamma spectrometry was then performed for each item using a HPGe detector, with a focus on longer lived gamma emitting radionuclides. Activities were quantified for all found isotopes and compared to relevant legal limits for exemption and clearance of radioactive objects. Activation was found to be significant after long irradiation sessions, as done during commissioning of a proton therapy room. Some of the investigated devices may also cumulate activity in time, depending on the scenario of periodic irradiation in routine clinical practice. However, the levels of activity and resulting beta/gamma doses are more comparable to internationally recommended concentration limits for exemption than to dose limits for radiation workers. Results of this study will help to determine nuclide inventories required by some legal authorities for radiation protection purposes.
The aim of this study was to investigate the absorbed dose and the linear energy transfer (LET) of a scanning proton pencil beam at the Proton Therapy Center Czech, applied to phantoms containing metal implants. We investigated two different phantoms composed of commonly used metals with a known chemical composition. Two rectangular phantoms consisted of water-equivalent environment material with a 65 mm thickness surrounding the 2, 5, 10 and 15 mm inserts of grade-2 and grade-5 Titanium. Track-etched detectors (TEDs) were placed behind the phantoms to gather the data. The measured LET spectra behind the implants were compared with Monte Carlo simulations using the Geant4 toolkit, version 10.03.p01. The simulations were used to provide additional information regarding the contribution of each type of particles to the LET spectra (protons, alpha particles, deuteron, neutrons, photons, and electrons) and to estimate the LET spectra above the TED's detection threshold. We used two different beam energies to study the most pertinent irradiation scenarios, one in the Bragg curve plateau and one at the maximum. The measurement of the LET spectra behind phantoms irradiated with a proton beam in the plateau region of the Bragg curve led to the detection of numerous particles with a very high LET. Lateral dose enhancement at the border between implants and the plastic material was detected when the phantoms were exposed to a proton beam and the data were recorded in the Bragg peak maximum. In this area, the dose increased 13 times for grade-2 Ti and 12 times for grade-5 Ti. The performed experimental study highlights the effect of dental implants on the LET spectra and absorbed dose when a proton pencil beam is crossing high-density titanium.
Proton detection in solid state NMR is continuously developing and allows one to gain new insights in structural biology. Overall, this progress is a result of the synergy between hardware development, new NMR methodology and new isotope labeling strategies, to name a few factors. Even though current developments are rapid, it is worthwhile to summarize what can currently be achieved employing proton detection in biological solids. We illustrate this by analysing the signal-to-noise ratio (SNR) for spectra obtained for a microcrystalline α-spectrin SH3 domain protein sample by (i) employing different degrees of chemical dilution to replace protons by incorporating deuterons in different sites, by (ii) variation of the magic angle spinning (MAS) frequencies between 20 and 110 kHz, and by (iii) variation of the static magnetic field B0. The experimental SNR values are validated with numerical simulations employing up to 9 proton spins. Although in reality a protein would contain far more than 9 protons, in a deuterated environment this is a sufficient number to achieve satisfactory simulations consistent with the experimental data. The key results of this analysis are (i) with current hardware, deuteration is still necessary to record spectra of optimum quality; (ii) 13CH3 isotopomers for methyl groups yield the best SNR when MAS frequencies above 100 kHz are available; and (iii) sensitivity increases with a factor beyond B0 3/2 with the static magnetic field due to a transition of proton-proton dipolar interactions from a strong to a weak coupling limit.
PURPOSE: With the increasing use of proton therapy, there is a growing emphasis on including radiation quality, often quantified by linear energy transfer, as a treatment plan optimization factor. The Timepix detectors offer energy-sensitive particle tracking useful for the characterization of proton linear energy transfer. To improve the detector's performance in mixed radiation fields produced in proton therapy, we customized the detector settings and performed the per-pixel energy calibration. METHODS: The detection threshold and per-pixel signal shaping time (IKrum current) were customized, and energy calibration was performed for MiniPIX Timepix3. The detector calibration was verified using α source and clinical proton beams, as well as Monte Carlo simulations. The effects on the detector's performance, in terms of spectral saturation and pixel occupancy, were evaluated. RESULTS: Measurements with proton beams showed a good agreement with simulations. With the customized settings, the measurable energy range in the detector data-driven mode was extended, and the signal duration time was reduced by 80%, while the yield of pixel time occupancy reduction depends on the number of occupied pixels. For performed measurements with proton beams, the number of occupied pixels was further reduced up to 40% due to the increased threshold. CONCLUSIONS: Customized detector configuration of the Timepix3 detector allowed for reduced pixel occupancy and mitigation of signal saturation in a data-driven mode without significantly interfering with the energy deposition measurement. The presented approach enables the extension of the operational range, including higher intensities and mixed-radiation fields in particle radiotherapy environments.
Metodika: Autoři předkládají případ záchytu renálního tumoru u plodu ve 33. týdnu těhotenství pomocí ultrasonografie a nukleární magnetické rezonance. Průběh těhotenství byl komplikován současným polyhydramnion. Plod ženského pohlaví byl porozen spontánně ve 37. týdnu těhotenství. Postnatální nefrektomie potvrdila prenatální diagnostický předpoklad – kongenitální mezoblastický nefrom. Kontrolní vyšetření dítěte ve věku 12 měsíců neprokázalo recidivu onemocnění. Závěr: Nález renálního tumoru u plodu je vzácný. Nejpravděpodobnější diagnózou je kongenitální mezoblastický nefrom s příznivou prognózou. Prenatální záchyt umožňuje prevenci komplikací (prevenci prematurity, záchyt rozvoje kardiální dekompenzace a hydropsu plodu) s naplánováním porodu a postnatálního řešení.
Methods: The autors report a case of renal tumor in a fetus at 33 weeks of gestation detected by means of ultrasonography and magnetic resonance imaging. The pregnancy course was complicated by polyhydramnios. The female infant was born vaginally at 37 weeks of gestation. Postnatal nephrectomy confirmed prenatal diagnostic presumption – congenital mezoblastic nephroma. At folllow-up at 12 months of age, the infant had no evidence of the disease. Conclusion. Detection of renal tumor in a fetus is rare. Congenital mezoblastic nephroma with the favourable prognosis is most probable diagnosis. Prenatal detection enables the prevention of complications (prematurity prevention, detection of the developing cardial decompensation and fetal hydrops) with the planning of labour and postnatal management.
- MeSH
- lidé MeSH
- magnetická rezonanční tomografie využití MeSH
- mezoblastický nefrom MeSH
- nefrektomie využití MeSH
- polyhydramnion MeSH
- prenatální diagnóza MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- kazuistiky MeSH
PURPOSE: To measure the environmental doses from stray neutrons in the vicinity of a solid slab phantom as a function of beam energy, field size and modulation width, using the proton pencil beam scanning (PBS) technique. METHOD: Measurements were carried out using two extended range WENDI-II rem-counters and three tissue equivalent proportional counters. Detectors were suitably placed at different distances around the RW3 slab phantom. Beam irradiation parameters were varied to cover the clinical ranges of proton beam energies (100-220MeV), field sizes ((2×2)-(20×20)cm(2)) and modulation widths (0-15cm). RESULTS: For pristine proton peak irradiations, large variations of neutron H(∗)(10)/D were observed with changes in beam energy and field size, while these were less dependent on modulation widths. H(∗)(10)/D for pristine proton pencil beams varied between 0.04μSvGy(-1) at beam energy 100MeV and a (2×2)cm(2) field at 2.25m distance and 90° angle with respect to the beam axis, and 72.3μSvGy(-1) at beam energy 200MeV and a (20×20) cm(2) field at 1m distance along the beam axis. CONCLUSIONS: The obtained results will be useful in benchmarking Monte Carlo calculations of proton radiotherapy in PBS mode and in estimating the exposure to stray radiation of the patient. Such estimates may be facilitated by the obtained best-fitted simple analytical formulae relating the stray neutron doses at points of interest with beam irradiation parameters.
PURPOSE: To characterize stray radiation around the target volume in scanning proton therapy and study the performance of active neutron monitors. METHODS: Working Group 9 of the European Radiation Dosimetry Group (EURADOS WG9-Radiation protection in medicine) carried out a large measurement campaign at the Trento Centro di Protonterapia (Trento, Italy) in order to determine the neutron spectra near the patient using two extended-range Bonner sphere spectrometry (BSS) systems. In addition, the work focused on acknowledging the performance of different commercial active dosimetry systems when measuring neutron ambient dose equivalents, H(∗)(10), at several positions inside (8 positions) and outside (3 positions) the treatment room. Detectors included three TEPCs--tissue equivalent proportional counters (Hawk type from Far West Technology, Inc.) and six rem-counters (WENDI-II, LB 6411, RadEye™ NL, a regular and an extended-range NM2B). Meanwhile, the photon component of stray radiation was deduced from the low-lineal energy transfer part of TEPC spectra or measured using a Thermo Scientific™ FH-40G survey meter. Experiments involved a water tank phantom (60 × 30 × 30 cm(3)) representing the patient that was uniformly irradiated using a 3 mm spot diameter proton pencil beam with 10 cm modulation width, 19.95 cm distal beam range, and 10 × 10 cm(2) field size. RESULTS: Neutron spectrometry around the target volume showed two main components at the thermal and fast energy ranges. The study also revealed the large dependence of the energy distribution of neutrons, and consequently of out-of-field doses, on the primary beam direction (directional emission of intranuclear cascade neutrons) and energy (spectral composition of secondary neutrons). In addition, neutron mapping within the facility was conducted and showed the highest H(∗)(10) value of ∼ 51 μSv Gy(-1); this was measured at 1.15 m along the beam axis. H(∗)(10) values significantly decreased with distance and angular position with respect to beam axis falling below 2 nSv Gy(-1) at the entrance of the maze, at the door outside the room and below detection limit in the gantry control room, and at an adjacent room (<0.1 nSv Gy(-1)). Finally, the agreement on H(∗)(10) values between all detectors showed a direct dependence on neutron spectra at the measurement position. While conventional rem-counters (LB 6411, RadEye™ NL, NM2-458) underestimated the H(∗)(10) by up to a factor of 4, Hawk TEPCs and the WENDI-II range-extended detector were found to have good performance (within 20%) even at the highest neutron fluence and energy range. Meanwhile, secondary photon dose equivalents were found to be up to five times lower than neutrons; remaining nonetheless of concern to the patient. CONCLUSIONS: Extended-range BSS, TEPCs, and the WENDI-II enable accurate measurements of stray neutrons while other rem-counters are not appropriate considering the high-energy range of neutrons involved in proton therapy.
- MeSH
- dávka záření MeSH
- fantomy radiodiagnostické MeSH
- fotony MeSH
- neutrony MeSH
- protonová terapie přístrojové vybavení metody MeSH
- protony MeSH
- radiometrie přístrojové vybavení metody MeSH
- spektrální analýza přístrojové vybavení metody MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
