ترغب بنشر مسار تعليمي؟ اضغط هنا

Design of a new tracking device for on-line dose monitor in ion therapy

126   0   0.0 ( 0 )
 نشر من قبل Giuseppe Battistoni
 تاريخ النشر 2016
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Charged Particle Therapy is a technique for cancer treatment that exploits hadron beams, mostly protons and carbons. A critical issue is the monitoring of the dose released by the beam to the tumor and to the surrounding tissues. We present the design of a new tracking device for monitoring on-line the dose in ion therapy through the detection of secondary charged particles produced by the beam interactions in the patient tissues. In fact, the charged particle emission shape can be correlated with the spatial dose release and the Bragg peak position. The detector uses the information provided by 12 layers of scintillating fibers followed by a plastic scintillator and a small calorimeter made of a pixelated Lutetium Fine Silicate crystal. Simulations have been performed to evaluate the achievable spatial resolution and a possible application of the device for the monitoring of the dose profile in a real treatment is presented.



قيم البحث

اقرأ أيضاً

An extensive comparison of the path uncertainty in single particle tracking systems for ion imaging was carried out based on Monte Carlo simulations. The spatial resolution as function of system parameters such as geometry, detector properties and th e energy of proton and helium beams was investigated to serve as a guideline for hardware developments. Primary particle paths were sampled within a water volume and compared to the most likely path estimate obtained from detector measurements, yielding a depth-dependent uncertainty envelope. The maximum uncertainty along this curve was converted to a conservative estimate of the minimal radiographic pixel spacing for a single set of parameter values. Simulations with various parameter settings were analysed to obtain an overview of the reachable pixel spacing as function of system parameters. The results were used to determine intervals of detector material budget and position resolution that yield a pixel spacing small enough for clinical dose calculation. To ensure a pixel spacing below 2 mm, the material budget of a detector should remain below 0.25 % for a position resolution of 200 $mathrm{mu m}$ or below 0.75 % for a resolution of 10 $mathrm{mu m}$. Using protons, a sub-millimetre pixel size could not be achieved for a phantom size of 300 mm or at a large clearance. With helium ions, a sub-millimetre pixel spacing could be achieved even for a large phantom size and clearance, provided the position resolution was less than 100 $mathrm{mu m}$ and material budget was below 0.75 %.
Proton beam therapy can potentially offer improved treatment for cancers of the head and neck and in paediatric patients. There has been a sharp uptake of proton beam therapy in recent years as improved delivery techniques and patient benefits are ob served. However, treatments are currently planned using conventional x-ray CT images due to the absence of devices able to perform high quality proton computed tomography (pCT) under realistic clinical conditions. A new plastic-scintillator-based range telescope concept, named ASTRA, is proposed here as the energy tagging detector of a pCT system. Simulations conducted using Geant4 yield an expected energy resolution of 0.7% and have demonstrated the ability of ASTRA to track multiple protons simultaneously. If calorimetric information is used the energy resolution could be further improved to about 0.5%. Assuming clinical beam parameters the system is expected to be able to efficiently reconstruct at least, 10$^8$ protons/s. The performance of ASTRA has been tested by imaging phantoms to evaluate the image contrast and relative stopping power reconstruction.
Charged particle beams are used in Particle Therapy (PT) to treat oncological patients due to their selective dose deposition in tissues and to their high biological effect in killing cancer cells with respect to photons and electrons used in convent ional radiotherapy. Nowadays, protons and carbon ions are used in PT clinical routine but, recently, the interest on the potential application of helium and oxygen beams is growing due to their reduced multiple scattering inside the body and increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands for online dose monitoring techniques, crucial to improve the quality assurance of treatments. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Prompt photons are produced by nuclear de-excitation processes and, at present, different dose monitoring and beam range verification techniques based on the prompt {gamma} detection have been proposed. It is hence of importance to perform the {gamma} yield measurement in therapeutical-like conditions. In this paper we report the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a PMMA target. The measurements were performed at the Heidelberg Ion-beam Therapy center (HIT) with beams of different energies. A LYSO scintillator has been used as photon detector. The obtained {gamma} yields for $^{12}$C ion beams are compared with results from literature, while no other results from $^{4}$He and $^{16}$O beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-{gamma} based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.
Radiation therapy with protons as of today utilizes information from x-ray CT in order to estimate the proton stopping power of the traversed tissue in a patient. The conversion from x-ray attenuation to proton stopping power in tissue introduces ran ge uncertainties of the order of 2-3% of the range, uncertainties that are contributing to an increase of the necessary planning margins added to the target volume in a patient. Imaging methods and modalities, such as Dual Energy CT and proton CT, have come into consideration in the pursuit of obtaining an as good as possible estimate of the proton stopping power. In this study, a Digital Tracking Calorimeter is benchmarked for proof-of-concept for proton CT purposes. The Digital Tracking Calorimeteris applied for reconstruction of the tracks and energies of individual high energy protons. The presented prototype forms the basis for a proton CT system using a single technology for tracking and calorimetry. This advantage simplifies the setup and reduces the cost of a proton CT system assembly, and it is a unique feature of the Digital Tracking Calorimeter. Data from the AGORFIRM beamline at KVI-CART in Groningen in the Netherlands and Monte Carlo simulation results are used to in order to develop a tracking algorithm for the estimation of the residual ranges of a high number of concurrent proton tracks. The range of the individual protons can at present be estimated with a resolution of 4%. The readout system for this prototype is able to handle an effective proton frequency of 1 MHz by using 500 concurrent proton tracks in each readout frame, which is at the high end range of present similar prototypes. A future further optimized prototype will enable a high-speed and more accurate determination of the ranges of individual protons in a therapeutic beam.
138 - M. Lenti , M. Veltri 2011
In this paper we investigate, with a detailed Monte-Carlo simulation based on Geant4, the novel approach [Nucl. Instrum. Methods A588 (2008) 457] to 3D imaging with photon scattering. A monochromatic and well collimated gamma beam is used to illumina te the object to be imaged and the photons Compton scattered are detected by means of a surrounding germanium strip detector. The impact position and the energy of the photons are measured with high precision and the scattering position along the beam axis is calculated. We study as an application of this technique the case of brain imaging but the results can be applied as well to situations where a lighter object, with localized variations of density, is embedded in a denser container. We report here the attainable sensitivity in the detection of density variations as a function of the beam energy, the depth inside the object and size and density of the inclusions. Using a 600 keV gamma beam, for an inclusion with a density increase of 30% with respect to the sorrounding tissue and thickness along the beam of 5 mm, we obtain at midbrain position a resolution of about 2 mm and a contrast of 12%. In addition the simulation indicates that for the same gamma beam energy a complete brain scan would result in an effective dose of about 1 mSv.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا