S. Derreumaux

Potential of hybrid computational phantoms for retrospective heart dosimetry after breast radiation therapy: a feasibility study.

PURPOSE Current retrospective cardiovascular dosimetry studies are based on a representative patient or simple mathematic phantoms. Here, a process of patient modeling was developed to personalize the anatomy of the thorax and to include a heart model with coronary arteries. METHODS AND MATERIALS The patient models were hybrid computational phantoms (HCPs) with an inserted detailed heart model. A computed tomography (CT) acquisition (pseudo-CT) was derived from HCP and imported into a treatment planning system where treatment conditions were reproduced. Six current patients were selected: 3 were modeled from their CT images (A patients) and the others were modelled from 2 orthogonal radiographs (B patients). The method performance and limitation were investigated by quantitative comparison between the initial CT and the pseudo-CT, namely, the morphology and the dose calculation were compared. For the B patients, a comparison with 2 kinds of representative patients was also conducted. Finally, dose assessment was focused on the whole coronary artery tree and the left anterior descending coronary. RESULTS When 3-dimensional anatomic information was available, the dose calculations performed on the initial CT and the pseudo-CT were in good agreement. For the B patients, comparison of doses derived from HCP and representative patients showed that the HCP doses were either better or equivalent. In the left breast radiation therapy context and for the studied cases, coronary mean doses were at least 5-fold higher than heart mean doses. CONCLUSIONS For retrospective dose studies, it is suggested that HCP offers a better surrogate, in terms of dose accuracy, than representative patients. The use of a detailed heart model eliminates the problem of identifying the coronaries on the patients CT.

Dependence of coronary 3-dimensional dose maps on coronary topologies and beam set in breast radiation therapy: a study based on CT angiographies.

PURPOSE In left-side breast radiation therapy (RT), doses to the left main (LM) and left anterior descending (LAD) coronary arteries are usually assessed after delineation by prior anatomic knowledge on the treatment planning computed tomography (CT) scan. In this study, dose sensitivity due to interindividual coronary topology variation was assessed, and hot spots were located. METHODS AND MATERIALS Twenty-two detailed heart models, created from heart computed tomography angiographies, were fitted into a single representative female thorax. Two breast RT protocols were then simulated into a treatment planning system: the first protocol comprised tangential and tumoral bed beams (TGs_TB) at 50 + 16 Gy, the second protocol added internal mammary chain beams at 50 Gy to TGs_TB (TGs_TB_IMC). For the heart, the LAD, and the LM, several dose indicators were calculated: dose-volume histograms, mean dose (Dmean), minimal dose received by the most irradiated 2% of the volume (D2%), and 3-dimensional (3D) dose maps. Variations of these indicators with anatomies were studied. RESULTS For the LM, the intermodel dispersion of Dmean and D2% was 10% and 11%, respectively, with TGs_TB and 40% and 80%, respectively, with TGs_TB_IMC. For the LAD, these dispersions were 19% (Dmean) and 49% (D2%) with TGs_TB and 35% (Dmean) and 76% (D2%) with TGs_TB_IMC. The 3D dose maps revealed that the internal mammary chain beams induced hot spots between 20 and 30 Gy on the LM and the proximal LAD for some coronary topologies. Without IMC beams, hot spots between 5 and 26 Gy are located on the middle and distal LAD. CONCLUSIONS Coronary dose distributions with hot spot location and dose level can change significantly depending on coronary topology, as highlighted by 3D coronary dose maps. In clinical practice, coronary imaging may be required for a relevant coronary dose assessment, especially in cases of internal mammary chain irradiation.

Why diamond dimensions and electrode geometry are crucial for small photon beam dosimetry

Recent use of very small photon beams (down to 4 mm) in stereotactic radiotherapy requires new detectors to accurately determine the delivered dose. Diamond detectors have been presented in the literature as an attractive candidate for this application, due to their small detection volume and the diamond atomic number (Z = 6) which is close to water effective atomic number (Zeff ∼ 7.42). However, diamond exhibits a density 3.51 times greater than that of water and recent studies using Monte Carlo simulations have demonstrated the drawback of a high-density detector on small beam output factors. The current study focuses on geometrical parameters of diamond detector, namely, the diamond dimensions and the electrode geometry, in order to solve the dosimetric issues still observed in small photon beams with diamond detectors. To give better insights to these open questions, we have used both computational method and experimental analysis. This study highlighted that reducing diamond dimensions is crucial for...

Conditions de mise en œuvre des « nouvelles techniques et pratiques » en radiothérapie. Synthèse du rapport du groupe de travail issu du groupe permanent d’experts en radioprotection médicale de l’Autorité de sûreté nucléaire

In August 2013, the French nuclear safety agency (ASN) requested the permanent group of experts in radiation protection in medicine (GPMED) to propose recommendations on the implementation of new technology and techniques in radiation oncology. These recommendations were finalized in February 2015 by the GPMED. In April 2015, the ASN sent a letter to the French ministry of health (DGS/DGOS), and its national health agencies (ANSM, INCa, HAS). In these letters, ASN proposed that, from the 12 recommendations made by the GPMED, an action plan should be established, whose control could be assigned to the French national cancer institute (INCa), as a pilot of the national committee for radiotherapy and that this proposal has to be considered at the next meeting of the national committee of radiotherapy.

0174 : RadiothErapy for BrEast Cancer and early detection of CArdiotoxicity (REBECCA): a prospective cohort study

Breast radiotherapy (RT) techniques used until the 1990s were responsible for increased mortality due to long term cardiac complications. Since the 2000s, improved techniques of RT have appeared leading to different dose distributions to organ at risks such as heart. But up to now, little is known on their cardiac toxicity. The aim of the REBECCA study is to evaluate whether helical tomotherapy (HT) induces cardiac toxicity that could be detected in the first two years after treatment based on analysis of subclinical functional and anatomical cardiac lesions at myocardial and coronary levels and evolution of circulating biomarkers. REBECCA study is a prospective cohort study that will include 120 women treated with adjuvant HT for breast cancer at the Institut Universitaire du Cancer Toulouse-Oncopole (IUCT), and followed up for 2 years after RT. Women aged 40 to 70 years, surgically treated at IUCT for breast cancer and for whom adjuvant RT with HT is indicated, without chemotherapy will be eligible for the study. Follow-up will include measures of a panel circulating biomarkers, coronary plaque index based on Coronary computed tomography angiography and myocardial strain based on 2D-speckle tracking echocardiography. Absorbed doses will be evaluated for the whole heart and for each different parts of heart, in particular coronary arteries. Analysis will focus on dose-response relationship between subclinical cardiac lesions, biomarkers, and different organ absorbed doses. Furthermore, this study aims to create a bio-bank of plasma and blood of this cohort for future investigations. This clinical research study is a novel approach to early detect cardiotoxicity of current breast RT, combining anatomical and functional heart consequences based on cardiac imaging, a panel of circulating biomarkers and a detailed heart dosimetry. With this approach, REBECCA aims to improve understanding of the mechanisms and circumstances that underlie the development of potential heart side effects and sequelaes.

Erratum de l’article « Avis du groupe de travail missionné par l’Autorité de sûreté nucléaire concernant la radiothérapie stéréotaxique » [Cancer Radiother 2012;16(S1):5–9]

Departement de radiotherapie, centre Antoine-Lacassagne, 33, avenue de Valombrose, 06189 Nice cedex 2, France Institut de radioprotection et de surete nucleaire (IRSN), BP 17, 92262 Fontenay-aux-Roses cedex, France Societe franc aise de physique medicale (SFPM), centre Antoine-Beclere, faculte de medecine, 45, rue des Saints-Peres, 75006 Paris, France Centre Alexis-Vautrin, 6, avenue de Bourgogne, 54511 Vandœuvre-les-Nancy, France Centre Oscar-Lambret, 3, rue Frederic-Combemale, BP 307, 59020 Lille cedex, France Centre regional de radiochirurgie stereotaxique, CHU Rangueil, avenue Jean-Poulhes, 31052 Toulouse cedex, France Service de radiotherapie, groupe Oncorad Garonne, clinique Pasteur, « L’Atrium », 1, rue de la Petite-Vitesse, 31300 Toulouse, France Service de physique medicale, centre Rene-Gauducheau, CLCC Nantes Atlantique, site hospitalier Nord, boulevard Jacques-Monod, 44805 Nantes Saint-Herblain cedex, France Unite de radiophysique et de radioprotection du patient, CHU Henri-Mondor, 51, avenue du Marechal-de-Lattre-de-Tassigny, 94010 Creteil, France Autorite de surete nucleaire (ASN), division de Bordeaux, cite administrative de Bordeaux, boite 21, 2, rue Jules-Ferry, 33090 Bordeaux cedex, France Hopital de la Timone, 264, rue Saint-Pierre, 13385 Marseille cedex 5, France Haute Autorite de sante, 2, avenue du Stade-de-France, 93218 Saint-Denis-La Plaine cedex, France Direction des rayonnements ionisants et de la sante, Autorite de surete nucleaire (ASN), 6, place du Colonel-Bourgoin, 75572 Paris cedex 12, France