The active vitamin D metabolites, 25-hydroxyvitamin D (25D) and 1,25-dihydroxyvitamin D (1,25D), are produced by successive hydroxylation steps and play key roles in several cellular processes. However, alternative metabolic pathways exist, and among them, the 4-hydroxylation of 25D is a major one. This study aims to investigate the structure-activity relationships of 4-hydroxy derivatives of 1,25D.
View Article and Find Full Text PDFPurpose: To determine prospectively the efficacy and to assess potential side effects of melphalan selective ophthalmic artery chemotherapy (SOAC) as first-line treatment for unilateral retinoblastoma.
Design: Phase 2 nonrandomized, prospective study.
Participants: Patients with unilateral retinoblastoma group B, C, or D of the International Classification for Intraocular Retinoblastoma (IRC).
Because of its principle and its high proof level clinical results, brachytherapy represents a specific irradiation technique for the treatment of primary tumors as well as some local relapses in pre-irradiated area. After a glory period between the 80's and 90's, brachytherapy has progressively lost its attractiveness. In order to provide a practical solution to this deleterious situation, it is important that guardianships, health care payers, patient associations, specialist doctors and radiation oncologists understand the reasons leading to this harmful state as well as the risks concerned.
View Article and Find Full Text PDFPurpose: A high level of accuracy while positioning the patient is mandatory for frameless stereotactic radiotherapy (SRT), as large doses in multiple fractions can be delivered near organs at risk. The objective of this study is to propose an end-to-end quality assurance method to verify that submillimetre alignment can be achieved with stereotactic conventional linacs.
Methods: We used a TrueBeam® linear accelerator equipped with a 6DOF robotic couch.
Purpose: A national survey was performed to assess patient dose indicators based on clinical indication and on patient morphology for most common adult computed tomography (CT) examinations in France.
Methods: Seventeen groups of clinical indications (GCIs) for diagnostic CT in adult patients were considered based on their frequency and on image quality requirements. Data was collected for 15-30 consecutive examinations performed between 2015 and 2017, per CT scanner and GCI.
Purposes: The introduction of digital breast tomosynthesis (DBT) into the French breast cancer screening program is forecast by the authorities. The aim of the present study was to evaluate image quality phantoms to be used as internal quality controls.
Methods: Seven breast phantoms dedicated to quality control in mammography were evaluated on reconstructed DBT images: ACR Model 015, BR3D, DBT QC model 021, Mam/Digi-EPQC, MTM100, TOMOMAM® and TOMOPHAN®.
Purpose: To evaluate whether patients with prostate cancer have worse functional urinary recovery with focal brachytherapy (FBT) at the base versus the apex of the prostate.
Methods And Materials: The functional outcomes of patients treated with FBT at the base of the prostate were compared with those of patients treated with FBT at the apex. Urinary symptoms, continence, and erectile dysfunction were measured using the International Prostate Symptom Score (IPSS), International Continence Score (ICS), and International Index of Erectile Function (IIEF-5) questionnaires, respectively, at baseline and at 6, 12, and 24 months after treatment.
Purpose: To analyse the rate of secondary malignancies observed in a series of 675 prostate cancer patients who underwent a permanent implant brachytherapy between 1999 and 2003, and to compare the incidence with the expected rate in a matched general French population.
Material And Methods: The cohort included low-risk patients and a selection of "favourable-intermediate" risk patients. All patients were homogeneously treated using an intraoperative dynamic planning prostate brachytherapy technique, with loose 125-iodine seeds and a prescription dose of 145Gy.
Purpose: To analyse long-term overall survival, relapse-free survival and late toxicities in a series of 675 patients treated between 1999 and 2003, with a median follow-up of 132 months.
Patients And Methods: The cohort included low-risk patients and a selection of "favourable-intermediate" risk patients. All patients were homogeneously treated using an intraoperative dynamic planning prostate brachytherapy technique, with loose 125 iodine seeds.
The French regulations concerning the involvement of medical physicists in medical imaging procedures are relatively vague. In May 2013, the ASN and the SFPM issued recommendations regarding Medical Physics Personnel for Medical Imaging: Requirements, Conditions of Involvement and Staffing Levels. In these recommendations, the various areas of activity of medical physicists in radiology and nuclear medicine have been identified and described, and the time required to perform each task has been evaluated.
View Article and Find Full Text PDFObjectives: To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT).
Methods: The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings.
Comput Methods Programs Biomed
September 2013
The morphological similarity of organs is studied with feature vectors based on geometric and Zernike 3D moments. It is particularly investigated if outliers and average models can be identified. For this purpose, the relative proximity to the mean feature vector is defined, principal coordinate and clustering analyses are also performed.
View Article and Find Full Text PDFPurpose: To evaluate the feasibility and the early toxicity of focal brachytherapy in highly selected localized prostate cancer patients.
Methods And Materials: Twenty-one patients underwent a focal brachytherapy between February 2010 and March 2012, representing 3.7% of the cases treated by our group during this period.
Cancer Radiother
April 2013
With an experience of more than 25 years for the pioneers (and more than 14 years in France), permanent implant brachytherapy using iodine 125 seeds (essentially) is now recognized as a valuable alternative therapy for localized low-risk prostate cancer patients. The possible extension of the indications of exclusive brachytherapy towards selected patients in the intermediate-risk group has now been confirmed by several studies. Moreover, for the other patients in the intermediate-risk group and for the patients in the high-risk group, brachytherapy, as an addition to external radiotherapy, could represent one of the best ways to escalate the dose.
View Article and Find Full Text PDFBrachytherapy dose distribution calculation has evolved from the simple use of charts to the TG-43 formalism. It depends on the physical and geometrical characteristics of each source, the position of the source relatively to the calculation point and on the medium composition. Its principles and limitations are presented as well as the different dosimetric systems associated with implementing rules and the definition of the prescribed dose.
View Article and Find Full Text PDFIntroduction: Patients with prominent median lobe hyperplasia and/or high International Prostate Symptom Score (IPSS) are often contraindicated for prostate brachytherapy, mainly because of the risk of post-implant urinary retention. We evaluated an approach combining in the same operative step a limited transurethral resection (TURP) of the median lobe, immediately followed by permanent implant-free seed brachytherapy.
Methods And Materials: From January 2007 to November 2008, 22 patients underwent a customized limited TURP of their median lobe immediately before brachytherapy.
This study was designed to measure organ absorbed doses from multi-detector row computed tomography (MDCT) on pediatric anthropomorphic phantoms, calculate the corresponding effective doses, and assess the influence of automatic exposure control (AEC) in terms of organ dose variations. Four anthropomorphic phantoms (phantoms represent the equivalent of a newborn, 1-, 5-, and 10-y-old child) were scanned with a four-channel MDCT coupled with a z-axis-based AEC system. Two CT torso protocols were compared: a first protocol without AEC and constant tube current-time product and a second protocol with AEC using age-adjusted noise indices.
View Article and Find Full Text PDFThis study assessed and compared various image quality indices in order to manage the dose of pediatric abdominal MDCT protocols and to provide guidance on dose reduction. PMMA phantoms representing average body diameters at birth, 1 year, 5 years, 10 years and 15 years of age were scanned in a four-channel MDCT with a standard pediatric abdominal CT protocol. Image noise (SD, standard deviation of CT number), noise derivative (ND, derivative of the function of noise with respect to dose) and contrast-to-noise ratio (CNR) were measured.
View Article and Find Full Text PDFWith an experience of more than 20 years for the pionneers (and more than 10 years in France), permanent implant brachytherapy using Iodin 125 seeds is now recognized as a valuable alternative therapy for localized low-risk prostate cancer patients. An extension of the indications of exclusive brachytherapy towards selected patients in the intermediate-risk group is presently under study. Moreover, for patients in the high-risk group, brachytherapy, as an addition to external radiotherapy, could represent one of the best way to escalate the dose for some patients.
View Article and Find Full Text PDFRadiat Prot Dosimetry
August 2008
Although great efforts have been made to improve the physical phantoms used to calibrate in vivo measurement systems, these phantoms represent a single average counting geometry and usually contain a uniform distribution of the radionuclide over the tissue substitute. As a matter of fact, significant corrections must be made to phantom-based calibration factors in order to obtain absolute calibration efficiencies applicable to a given individual. The importance of these corrections is particularly crucial when considering in vivo measurements of low energy photons emitted by radionuclides deposited in the lung such as actinides.
View Article and Find Full Text PDFNew biometric equations used for assessing the thickness of the overlay plate to be added to the physical phantom were determined based on the Computed Tomography (CT) chest images of 33 adult males in order to improve the calibration of in vivo lung counting systems using the Livermore phantom. These equations are specific to systems composed of four germanium detectors with the measured subject in supine position. A comparison with the biometric equations used to date as reference in France was carried out and proved the usefulness of equations directly applicable to the Livermore phantom.
View Article and Find Full Text PDFRadiat Prot Dosimetry
September 2008
In the frame of IDEA project, a research programme has been carried out to study the potential of the reconstruction of numerical anthropomorphic phantoms based on personal physiological data obtained by computed tomography (CT) and Magnetic Resonance Imaging (MRI) for calibration in in vivo monitoring. As a result, new procedures have been developed taking advantage of recent progress in image processing codes that allow, after scanning and rapidly reconstructing a realistic voxel phantom, to convert the whole measurement geometry into computer file to be used on line for MCNP (Monte Carlo N-Particule code) calculations. The present paper overviews the major abilities of the OEDIPE software studies made in the frame of the IDEA project, on the examples of calibration for lung monitoring as well as whole body counting of a real patient.
View Article and Find Full Text PDFThe paper presents the OEDIPE (French acronym that stands for tool for personalised internal dose assessment) and SESAME (for simulation of external source accident with medical images) computational tools, dedicated to internal and external dose assessment, respectively, and currently being developed at the Institute for Radiological Protection and Nuclear Safety. The originality of OEDIPE and SESAME, by using voxel phantoms in association with Monte Carlo codes, lies in their ability to construct personalised voxel phantoms from medical images and automatically generate the Monte Carlo input file and visualise the expected results. OEDIPE simulates in vivo measurements to improve their calibration, and calculates the dose distribution taking both internal contamination and internal radiotherapy cases into account.
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