Loading the tumor with 31^{31}P, 63^{63}Cu and 89^{89}Y provides an in vivo prompt gamma-based range verification for therapeutic protons

International audienceIntroduction: The main rationale for using protons in cancer treatment is based on the highly conformal dose distribution and normal tissue spearing compared to conventional radiotherapy. The main limit of proton therapy is the particle range uncertainty due to patient setup, dose calculation and imaging. To account for this, a safety margin is added to the tumor to ensure the prescribed dose to the target. Reducing range uncertainties would result in the reduction of irradiation volume and would allow full exploitation of the proton therapy benefits. In this work, we presented a feasibility study for a strategy to achieve in vivo proton range verification based on prompt gammas (PG). This approach relies on the detection of signature prompt gammas, generated by the interaction of primary protons with a non-radioactive element, that is selectively loaded into a tumor with a drug carrier. The number of characteristic gammas is directly related to the proton range, and its measurement provides an estimate of the position at which the primary beam stops with respect to the tumor location.Method: We identified the criteria for selecting potential candidate materials and combined them with TALYS predictions to make the selection. We carried out an experimental campaign to characterize the PG spectra generated by the chosen materials when irradiated with therapeutic protons and compared them with TOPAS Monte Carlo toolkit predictions.Results: We identified 31-Phosphorous, 63-Copper and 89-Yttrium as potential candidates for this application based on TALYS calculations. The experimental data confirmed that all candidates emit signature prompt gammas different from water (here used as a proxy for normal tissue), and that the gamma yield is directly proportional to the element concentration in the solution. Four specific gamma lines were detected for both 31P (1.14, 1.26, 1.78, and 2.23 MeV) and 63Cu (0.96, 1.17, 1.24, 1.326 MeV), while only one for 89Y (1.06 MeV). The simulations indicate that the count of characteristic gammas is directly proportional to the proton range, reaching in some cases a saturation value around the tumor’s far edge. The results also indicate that to achieve a range accuracy below the current value of 2–3 mm, the uncertainty on the prompt gammas count has to be below 5% for 31-Phosphorous and 63-Copper, or 10% for 89-Yttrium.Discussion: We demonstrated that loading the tumor with a label element prior to proton treatment generates signature gammas that can be used to verify the beam range in vivo, reaching a potential range accuracy below the current limitations. This approach can be either used stand-alone or combined with other existing methodologies to further improve range resolution.</jats:p

Performances of a 1\u2033 71\u2033 Cs2LiYCl6 scintillator detector

In this work we have measured the performances of a 1\u2033 71\u2033 sample of a CLYC scintillator (Cs2LiYCl6) with 95% enrichment of 6Li produced by RMD. Different PMT models, with borosilicate glass window or quartz window have been used. The Pulse line-shape and Pulse shape discrimination for different type of incident radiation (gamma-rays and thermal neutrons) have been investigated. The response to thermal neutrons has been measured using an AmBe source and a digital oscilloscope. A measurement of the internal radiation and the energy resolution for different gamma rays have been additionally performed

Performances of a 1 '' x1 '' Cs2LiYCl6 scintillator detector

In this work we have measured the performances of a 1″×1″ sample of a CLYC scintillator (Cs 2 LiYCl 6 ) with 95% enrichment of 6 Li produced by RMD. Different PMT models, with borosilicate glass window or quartz window have been used. The Pulse line-shape and Pulse shape discrimination for different type of incident radiation (gamma-rays and thermal neutrons) have been investigated. The response to thermal neutrons has been measured using an AmBe source and a digital oscilloscope. A measurement of the internal radiation and the energy resolution for different gamma rays have been additionally performed. © 2013 IEEE.status: publishe

Analysis and first order correction of signal saturation effects in photomultiplier tubes for improved estimation of interacting radiation energy in Lanthanum bromide scintillators

The huge amount of optical photons emitted in burst by Cerium doped Lanthanum bromide scintillators poses a severe constraint on the specifications of photomultipliers, namely they must operate at very large instantaneous current values with minimum saturation of output pulse signals. Acquisition in shape and processing of photomultipliers output pulses by means of high-speed free-running analog to digital converters and processing devices allows specific correction for pulse saturation and distortion effects, due to high-gain tubes operated at relatively high power supply voltage. We analyze the effects of output signal saturation in photomultiplier tubes as a function of the high voltage level and the amount of energy released in the scintillator crystal, proposing a simple model to characterize this complex phenomenon. According to the proposed model, a preliminary first-order correction is calculated and applied to the energy estimations obtained by a traditional analog spectroscopy system, for energies up to 9 MeV, reducing the maximum estimation error by almost an order of magnitude

Thermal and fast neutron detection with two CLYC scintillators

© 2014 IEEE. The crystal Cs2LiYCl6:Ce (CLYC) is a very interesting scintillator material because of its excellent energy resolution and its capability to identify gamma rays and fast/thermal neutrons. In this work, the response to gamma, thermal and fast neutrons of two CLYC 1x1 crystals was measured: the first one, enriched with 6Li at 95% is ideal for thermal neutron measurements while the second one, enriched with 7Li at 99% is suitable for fast neutron measurements. The crystals were coupled to quartz window R6231-1000MOD HAMAMATSU PMTs. The thermal neutrons were measured in both detectors using an AmBe source in the gamma spectroscopy laboratory of the University of Milano, Italy. The measurements of fast neutrons were performed at Frascati (Italy) Neutron Generator facility providing neutrons of 14.1 MeV and 2.5 MeV.status: publishe

Statistical properties of the well deformed Sm 153,155 nuclei and the scissors resonance

The nuclear level densities (NLDs) and the γ-ray strength functions (γSFs) of Sm153,155 have been extracted from (d,pγ) coincidences using the Oslo method. The experimental NLD of Sm153 is higher than the NLD of Sm155, in accordance with microscopic calculations. The γSFs of Sm153,155 are in fair agreement with QRPA calculations based on the D1M Gogny interaction. An enhancement is observed in the γSF for both Sm153,155 nuclei around 3 MeV in excitation energy and is attributed to the M1 scissors resonance (SR). Their integrated strengths were found to be in the range 1.3-2.1 and 4.4-6.4 μN2 for Sm153 and Sm155, respectively. The strength of the SR for Sm155 is comparable to those for deformed even-even Sm isotopes from nuclear resonance fluorescence measurements, while that of Sm153 is lower than expected.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

PANDORA Project for the study of photonuclear reactions below A = 60

info:eu-repo/semantics/publishe