[en] Objective: to determine the influence of acquisition and reconstruction parameters on the dose and the image quality in multi detectors CT scanning to optimize the protocols. As conclusion: The optimization allowed to reduce, in average, the weighted computed tomography dose index-vol (wC.T.D.I.vol) of 20% through the pitch increase, the use of the broadest collimation and/or the use of a retrospectively reconstruction (zoom factor and/or increase matrix size) without deteriorating the noise and/or resolution performances more than 10%. (N.C.)

[en] Objective: to determine the influence of acquisition parameters and reconstruction of dose and the image quality in multi detectors T.D.M. for protocols optimization. conclusion: the optimization allowed to reduce in average, the C.T.D.I.vol (weighted computed tomography dose index) of 20% via the pitch increase, the use of a collimation as broad as possible and/or the use of a retrospectively construction (factor zoom and/or increased size of matrix) without degrading the performances of noise and:or resolution of more than 10%. (N.C.)

[en] The development of conformal radiotherapy techniques (CRT) and intensity modulated CRT requires an accurate delineation of target structures and organs at risk. Thus, additional information provided by anatomical and/or functional imaging modalities can be used for volume of interest determination combined with traditionally used Computed Tomography imaging (CT): for instance, functional or morphological Magnetic Resonance Imaging (f MRI or m MRI) or Positron Emission Tomography (PET). A prerequisite to the simultaneous use of this information is image registration. Due to the differences between the images and the information they provide, a quality control of image registration process for radiotherapy is mandatory. The purpose of this article is to present the difficulties in implementing such controls and to show the necessity for a clinical validation on patient's images. The last part of this work presents the possible interest in using f MRI to help radio-oncologists in the treatment planning for gliomas associated to image co-registration and quality control considerations. (authors)

[en] The increase in the collective radiation dose due to the large number of medical imaging exams has led the medical physics community to deeply consider the amount of dose delivered and its associated risks in these exams. For this purpose we have developed a Monte Carlo tool, PENRADIO, based on a modified version of PENELOPE code 2006 release, to obtain an accurate individualized radiation dose in conventional and interventional radiography and in computed tomography (CT). This tool has been validated showing excellent agreement between the measured and simulated organ doses in the case of a hip conventional radiography and a coronary angiography. We expect the same accuracy in further results for other localizations and CT examinations. (authors)

[en] The interest of precise calculation of radiation doses distributions remote areas of irradiation is to open new prospects in the knowledge of the contribution of radiotherapy in the occurrence of iatrogenic early and delayed effects. (N.C.)

[en] This study presents a method aimed at creating radiotherapy (RT) patient-adjustable whole-body phantoms to permit retrospective and prospective peripheral dose evaluations for enhanced patient radioprotection. Our strategy involves virtual whole-body patient models (WBPM) in different RT treatment positions for both genders and for different age groups. It includes a software tool designed to match the anatomy of the phantoms with the anatomy of the actual patients, based on the quality of patient data available. The procedure for adjusting a WBPM to patient morphology includes typical dimensions available in basic auxological tables for the French population. Adjustment is semi-automatic. Because of the complexity of the human anatomy, skilled personnel are required to validate changes made in the phantom anatomy. This research is part of a global project aimed at proposing appropriate methods and software tools capable of reconstituting the anatomy and dose evaluations in the entire body of RT patients in an adapted treatment planning system (TPS). The graphic user interface is that of a TPS adapted to obtain a comfortable working process. Such WBPM have been used to supplement patient therapy planning images, usually restricted to regions involved in treatment. Here we report, as an example, the case of a patient treated for prostate cancer whose therapy planning images were complemented by an anatomy model. Although present results are preliminary and our research is ongoing, they appear encouraging, since such patient-adjusted phantoms are crucial in the optimization of radiation protection of patients and for follow-up studies. (note)

[en] Full text: Public Health Codes more and more require that any information relevant for the estimation of the high doses delivered within the target volumes and the low doses delivered outside should be recorded. In this context, the availability, for each radiotherapy patient, of the magnitude of the unavoidable low doses delivered outside the target-volumes, becomes an important issue. However, to date, Treatment Planning Systems (TPS) are not designed for this issue. We therefore have developed a new version of the ISOgray TPS, which can provide, in addition to the dose distributions within the target-volumes, the magnitude of the doses to distant healthy tissues in the course of common radiotherapy procedures. Our strategy involves 3 modules: A library of adjustable whole-body patient models in treatment position, which allows different patient anatomies to be simulated; A multi-sources beam model, which allows the dosimetric data of the irradiation field to be extended to the whole body; A dose calculation program producing the dose distributions within the target-volumes and in any organ outside. This paper describes the principles of our approach and provides data on doses distributions to distant organs for various common radiotherapy procedures. At this stage the software is under development. The calculations with this system are checked against experimental data from ionisation chamber and thermoluminescent dosimetry. Although the development of our system is still in progress, the preliminary results are encouraging. Allowing whole-body dose evaluations for each patient at the time of the treatment planning, our approach should provide relevant information required for the patient radiation protection and radiation therapy benefit-risk management purposes. The systematic evaluation of the low doses delivered at distance of the target-volumes is a basic requirement for quality assurance of radiotherapy and prospective studies of long-term risks of modern radiotherapy procedures. (author)

[en] A new Monte Carlo system called PENSSART for 'PENELOPE Simulation for the Safety in Radiotherapy' has been developed for quality control of the treatment plans. PENSSART is based on the 2006 release of PENELOPE that we have adapted to allow for the transport of particles in voxelized geometries. The new platform is built upon three main modules that help the user in the definition of the different control procedure steps. The purpose of this study was twofold. In a first part we have validated the beam implementation and the patient/phantom description in PENSSART. In a second part we have compared dose distributions obtained experimentally, with PENSSART and also with an algorithm usually used in clinical practice for treatment planning. The results demonstrate the usefulness of the developed system. (authors)

[en] In this study, the impact of radiochromic films' (XR-RV3) calibration on PSD measurements was investigated under various peak kilovoltage (kV_p) and additional filtration conditions. Films were calibrated free-in-air for six beam qualities with Allura Xper FD20 system (Philips). Six calibration curves (CCs) were constructed. Each beam quality was characterized in terms of mean energy (ME) in the air, with table, with table and water phantom using Monte Carlo simulations. A cohort of 155 patient films from cardiology (37) and vascular (118) procedures were read with each CC. Routine calibration beam quality was taken as reference (Dose_N_o_r_m). Overall, it was observed that for a wider ME difference between the exposed film and the CC used, a larger deviation (from -28% to +41%) was observed. The choice of beam quality for the calibration is a key point when additional filtration and kVp are automatically controlled in clinical conditions. (authors)