89 research outputs found
Dose Delivery Concept and Instrumentation
Radiation therapy aims to deliver the prescribed amount of dose to a tumour
at the same time as sparing the surrounding tissues as much as possible. In
charged particle therapy, delivering the prescribed dose is equivalent to
delivering the prescribed number of ions of a given energy at each position of
the irradiation field. The accurate delivery is committed to a dose delivery
(DD) system that shapes, guides and controls the beam before the patient
entrance. Most of the early DD systems provided uniform lateral dose profiles
by using different devices, mainly patient-specific, placed in the beam line to
shape the three-dimensional final target dose. More recently, systems that
provide highly conformal dose distributions using thousands of narrow beams at
well-defined energy were developed which feature advanced scanning magnets and
real-time beam monitors, without patient-specific hardware. This lecture will
cover the general dose delivery concept as well as the different DD
instrumentations depending mainly on the beam delivery technique and on the
particle and accelerator types. Some characteristic worldwide DD and beam
monitor systems will be mentioned.Comment: presented at the CAS- CERN Accelerator School on Accelerators for
Medical Application, V\"osendorf, Austria, 26 May - 5 June, 201
Variation of the relative biological effectiveness with fractionation in proton therapy: analysis of prostate cancer response
Purpose: To present a methodology to analyze the variation of RBE with
fractionation from clinical data of tumor control probability (TCP) and to
apply it to study the response of prostate cancer to proton therapy.
M&M: We analyzed the dependence of the RBE on the dose per fraction by using
the LQ model and the Poisson TCP formalism. Clinical TCPs for prostate cancer
treated with photon and proton therapy for conventional fractionation (2
Gy(RBE)x37 fractions), moderate hypofractionation (3 Gy(RBE)x20 fractions) and
hypofractionation (7.25 Gy(RBE)x5 fractions) were obtained from the literature
and analyzed.
Results: The theoretical analysis showed three distinct regions with RBE
monotonically decreasing, increasing or staying constant with the dose per
fraction, depending on the change of ({\alpha}, \{beta}) values between photon
and proton irradiation (the equilibrium point being
at({\alpha}_p/\{beta}_p)=({\alpha}_X/\{beta}_X)({\alpha}_X/{\alpha}_p)). An
analysis of the clinical data showed RBE values that decline with increasing
dose per fraction: for low risk RBE=1.124, 1.119, and 1.102 for 1.82 Gy, 2.73
Gy and 6.59 Gy per fraction (physical proton doses), respectively; for
intermediate risk RBE=1.119, and 1.102 for 1.82 Gy, and 6.59 Gy per fraction
(physical proton doses), respectively. These values are nonetheless very close
to the nominal 1.1 value.
Conclusions: We presented a methodology to analyze the RBE for different
fractionations, and we used it to study clinical data for prostate cancer. The
analysis shows a monotonically decreasing RBE with increasing dose per
fraction, which is expected from the LQ formalism and the changes in ({\alpha},
\{beta}) between photon and proton irradiation. However, the calculations in
this study have to be considered with care as they may be biased by limitations
in the modeling and/or by the clinical data set used for the analysis.Comment: Minor changes to match accepted manuscript; in press Medical Physic
Direct evaluation of radiobiological parameters from clinical data in the case of ion beam therapy: an alternative approach to the relative biological effectiveness
Preliminary characterization tests of detectors of on-line monitors systems of the italian National Center of Oncological Hadron-therapy (CNAO)
Development of a front-end electronics for an innovative monitor chamber for high-intensity charged particle beams
A multi-gap ionization monitor chamber has been
developed by INFN and Torino University, for monitoring of
high intensity pulsed charged particle beams. The read-out
of the chamber is based on a 64-channel ASIC, designed in
CMOS 0.35ÎĽm technology which features for each channel
an independent current-to-frequency converter followed by a
synchronous counter. The chip was designed for connecting each
channel to a different detector element. However, high beam
intensities may lead to an input current above the saturation
level of a single channel. A novel readout has been tested where
all the input channels of the chip have been connected in parallel
to the same detector element allowing to reach 64-times higher
input current with only a modest deterioration of the resolution.
Results will be presented in terms of linearity and noise, and will
be compared to a simulation where the chip is modeled as a set
of independent and uncorrelated channels
Fluence Beam Monitor for High-Intensity Particle Beams Based on a Multi-Gap Ionization Chamber and a Method for Ion Recombination Correction
This work presents the tests of a multi-gap detector (MGD), composed of three parallel-plate ionization chambers (ICs) with different gap widths, assembled to prove the capability of correcting for charge volume recombination which is expected to occur when high fluence rates are delivered. Such beam conditions occur with a compact accelerator for charged particle therapy developed to reduce the costs, to accomplish faster treatments and to exploit different beam delivery techniques and dose rates as needed, for example, for range modulation and FLASH irradiations, respectively. The MGD was tested with carbon ions at the Centro Nazionale di Adroterapia Oncologica (CNAO Pavia, Italy), and with protons in two different beam lines: at Bern University Hospital with continuous beams and at the Laboratori Nazionale del Sud (Catania, Italy) of the Italian National Center of Nuclear Physics (INFN) with pulsed beams. For each accelerator, we took measurements with different beam intensities (up to the maximum rate of ionization achievable) and changed the detector bias voltage (V) in order to study the charge collection efficiency. Charge recombination models were used to evaluate the expected collected charge and to measure the linearity of the rate of ionization with the beam fluence rate. A phenomenological approach was used to determine the collection efficiency (f1) of the chamber with thinnest gap from the relative efficiencies, f1/f2 and f1/f3, exploiting the condition that, for each measurement, the three chambers were exposed to the same rate of ionization. Results prove that two calibration curves can be determined and used to correct the online measurements for the charge losses in the ICs for recombination
D-IMRT verification with a 2D pixel ionization chamber: dosimetric and clinical results in head and neck cancer
Characterization of a front-end electronics for the monitoring and control of hadrontherapy beams
Abstract An integrated 64-channel device for the read-out of parallel plate pixel and strip ionization detectors has been developed by the INFN and University of Torino. The detectors will be used for the monitoring and control of hadrontherapy beams. The ASIC has been designed in CMOS 0.8 ÎĽm technology and it is based on a current-to-frequency converter followed by a synchronous counter. In this paper, we present a detailed characterization of the device done with 113 chips
'Ionizing radiation effects on a 64-channel charge measurement ASIC designed in CMOS 0.35 ÎĽm technology'
A 64-channel circuit Application Specific Integrated Circuit (ASIC) for charge measurement has been designed in CMOS 0.35mm technology and characterized with electrical tests. The ASIC has been conceived to be used as a front-end for dosimetry and beam monitoring detector read-out. For that application, the circuitry is housed at a few centimeters from the irradiated area of the detectors and therefore radiation damages can affect the chip performances. The ASIC has been tested on an X-ray beam. In this paper, the results of the test and an estimate of the expected lifetime of the ASIC in a standard radio-therapeutical treatment environment are presented. An increase of the background current of 2 fA/Gy has been observed at low doses, whilst the gain changes by less than 3% when irradiated up to 15 kGy. Furthermore it has been assessed that, when used as an on-line beam monitor and the annealing effect has been taken into account, the background current increase is ďż˝ 440 fA/year
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