Integrate range shifter in immobilization for proton therapy: 3D printed materials characterization

3D printing is investigated for application in patient immobilization during proton therapy (PT). It potentially enables a merge of immobilization, range shifting and other functionality into one patient-specific structure. Beside minimizing the lateral beam spread due to the removal of air gap it could also reduce the collision risk and the treatment time compared to movable nozzle snouts. In this first study, 9 different 3D printed materials were characterized in detail. The resulting data (Table 1) will serve as input for the design of a printed immobilization structure. The printed test objects showed reduced geometric printing accuracy for 3 materials. Compression testing yielded Young’s moduli from 0.6 MPa to 3445 MPa, without deterioration after exposure to 100 Gy in a MV photon beam. Dual-energy CT methods were used to estimate the effective atomic number Zeff, the relative electron density e and the stopping power ratio SPR. Zeff ranged from 5.91 to 10.43. The SPR and e both ranged from 0.6 to 1.22. The measured photon attenuation coefficients at therapeutic energies scaled linearly with e. In a 62 MeV proton beam, good agreement was seen between the DECT estimated SPR and the measured range shift, except for the higher Zeff. As opposed to the photon attenuation, the proton range shifting was printing orientation dependent for certain materials. In conclusion printed materials exhibit a wide variation in structural and radiological properties. The quantification of these characteristics enables optimal material selection for the design of a multifunctional 3D printed immobilization structure for PT

PD-0462: Towards dosimetric tracking with adaptive VMAT?

The news and information source for the Henry M. Goldman School of Graduate Dentistr

Ethylene C2H3D isotopologue: high resolution study of v6, v4, v8, v7 and v10 fundamentals

High Resolution Fourier transform infrared spectra of the C2H3D molecule were recorded with Doppler limited resolution in the region of 600 - 1250 cm-1 at room temperature. The measurements were carried out under several different absorption conditions using the Bruker 120 HR spectrometer in Braunschweig Technical University. Five fundamentals v6, v4, v8, v7, and v10 were observed and found to be perturbed by different resonance interactions. About 6000 lines were assigned in the recorded spectrum. They were used then in the weighted fit procedure with the effective Hamiltonian taking into account five strongly interacting states

Towards 3D printed multifunctional immobilization for proton therapy: initial materials characterization

Purpose: 3D printing technology is investigated for the purpose of patient immobilization during proton therapy. It potentially enables a merge of patient immobilization, bolus range shifting, and other functions into one single patient-speci c structure. In this rst step, a set of 3D printed materials is characterized in detail, in terms of structural and radiological properties, elemental composition, directional dependence, and structural changes induced by radiation damage. These data will serve as inputs for the design of 3D printed immobilization structure prototypes. Methods: Using four di erent 3D printing techniques, in total eight materials were subjected to testing. Samples with a nominal dimension of 20×20×80 mm3 were 3D printed. The geometrical printing accuracy of each test sample was measured with a dial gage. To assess the mechanical response of the samples, standardized compression tests were performed to determine the Young’s modulus. To investigate the e ect of radiation on the mechanical response, the mechanical tests were performed both prior and after the administration of clinically relevant dose levels (70 Gy), multiplied with a safety factor of 1.4. Dual energy computed tomography (DECT) methods were used to calculate the relative electron density to water ρe, the e ective atomic number Ze , and the proton stopping power ratio (SPR) to water SPR. In order to validate the DECT based calculation of radiological properties, beam measurements were performed on the 3D printed samples as well. Photon irradiations were performed to measure the photon linear attenuation coe cients, while proton irradiations were performed to measure the proton range shift of the samples. The direc- tional dependence of these properties was investigated by performing the irradiations for di erent orientations of the samples. Results: The printed test objects showed reduced geometric printing accuracy for 2 materials (deviation > 0.25 mm). Compression tests yielded Young’s moduli ranging from 0.6 to 2940 MPa. No deterioration in the mechanical response was observed after exposure of the samples to 100 Gy in a therapeutic MV photon beam. The DECT-based characterization yielded Ze ranging from 5.91 to 10.43. The SPR and ρe both ranged from 0.6 to 1.22. The measured photon attenuation coe cients at clinical energies scaled linearly with ρe. Good agreement was seen between the DECT estimated SPR and the measured range shift, except for the higher Ze . As opposed to the photon attenuation, the proton range shifting appeared to be printing orientation dependent for certain materials. Conclusions: In this study, the rst step toward 3D printed, multifunctional immobilization was performed, by going through a candidate clinical work ow for the rst time: from the material printing to DECT characterization with a veri cation through beam measurements. Besides a proof of concept for beam modi cation, the mechanical response of printed materials was also investigated to assess their capabilities for positioning functionality. For the studied set of printing techniques and materials, a wide variety of mechanical and radiological properties can be selected from for the intended purpose. Moreover the elaborated hybrid DECT methods aid in performing in-house quality assurance of 3D printed components, as these methods enable the estimation of the radiological properties relevant for use in radiation therapy

The management of pancreatic cancer. Current expert opinion and recommendations derived from the 8th World Congress on Gastrointestinal Cancer, Barcelona, 2006

This article summarizes the expert discussion on the management of pancreatic cancer, which took place during the 8th World Congress on Gastrointestinal Cancer in June 2006 in Barcelona. A multidisciplinary approach to a patient with pancreatic cancer is essential, in order to guarantee an optimal staging, surgery, selection of the appropriate (neo-)adjuvant strategy and chemotherapeutic choice management. Moreover, optimal symptomatic management requires a dedicated team of health care professionals. Quality control of surgery and pathology is especially important in this disease with a high locoregional failure rate. There is now solid evidence in favour of chemotherapy in both the adjuvant and palliative setting, and gemcitabine combined with erlotinib, capecitabine or platinum compounds seems to be slightly more active than gemcitabine alone in advanced pancreatic cancer. There is a place for chemoradiotherapy in selected patients with locally advanced disease, while the role in the adjuvant setting remains controversial. Those involved in the care for patients with pancreatic cancer should be encouraged to participate in well-designed clinical trials, in order to increase the evidence-based knowledge and to make further progres

The diagnosis and management of gastric cancer: expert discussion and recommendations from the 12th ESMO/World Congress on Gastrointestinal Cancer, Barcelona, 2010

Well-recognized experts in the field of gastric cancer discussed during the 12th European Society Medical Oncology (ESMO)/World Congress Gastrointestinal Cancer (WCGIC) in Barcelona many important and controversial topics on the diagnosis and management of patients with gastric cancer. This article summarizes the recommendations and expert opinion on gastric cancer. It discusses and reflects on the regional differences in the incidence and care of gastric cancer, the definition of gastro-esophageal junction and its implication for treatment strategies and presents the latest recommendations in the staging and treatment of primary and metastatic gastric cancer. Recognition is given to the need for larger and well-designed clinical trials to answer many open question

Thermal study of the effect of several solvents on polymerization of acrylonitrile and their subsequent pyrolysis

The polymerization of acrylonitrile to polyacrylonitrile (PAN) has been studied using several solvents: N,N-dimethylformamide (DMF), hexane, toluene, water, and in bulk form (no solvent). The addition of DMF is the only case where both monomer and polymer are soluble in the solvent. Thermal analyses of the resultant products after polymerization have been performed by differential scanning calorimetry and pyrolysis–gas chromatography: mass spectrometry. The effect of the solvents employed as media for polymerization is interpreted from the results of the thermal and structural (X-ray diffraction) methods. The polymer samples obtained when using water or toluene as solvents have the greater content of amorphous components compared to the others. The amide molecules are difficult to completely eliminate in the product obtained after the polymerization reaction and even after prolonged heating at 110°C and remain occluded. DMF can be considered to exert a plasticized effect on PAN and is even capable of forming complexes by dipolar bonding. As a result of this interaction, the thermogram is quite different from the other samples studied in the present work, showing a single sharp exothermic peak. This is associated with nitrile group polymerization (cyclization) of PAN. It is deduced that the amount of heat evolved as well as the temperature interval over which it is released are influenced by the chemical processing of PAN, in particular when using DMF as solvent for both monomer and polymer. Pyrolysis of the different PAN samples revealed the release of occluded solvent molecules, mainly when using DMF, and compounds produced from the thermal degradation processes. Different types of cyclized compounds, such as pyridine derivatives and aromatic nitriles were identified. All these compounds could be derived from cyclized PAN structures which are not completely degraded by the thermal treatment of pyrolysis. Alkyldinitriles have also been tentatively identified associated with the final molecular breakdown of cyclized structures with six-member rings by pyrolysis. Valuable complementary information on the structure of the PAN samples (homopolymer) obtained using the different processing approaches involving several solvent media has been provided by pyrolysis. The present results will improve our understanding of the evolution of the structure and properties of carbon and activated carbon fibres which will enable us to establish processing strategies in order to obtain these materials under adequate and reproducible conditions.Peer reviewe

What do we know about the α/β for prostate cancer?

Since last decade, the debate on the parameter which reflects prostate cancer sensitivity to fractionation in a radiotherapy treatment, the α/β, has become extensive. Unlike most tumors, the low labeling indices (LI) and large potential doubling time that characterize the prostate tumor led some authors to consider that it may behave as a late responding tissue. So far, the existing studies with regard to this subject point to a low value of α/β, around 2.7 Gy, which may be considered as a therapeutic gain in relation to surrounding normal tissues by using fewer and larger fractions. The aim of this paper is to review several estimates that have been made in the last few years regarding the prostate cancer α/β both from clinical and experimental data, as well as the set of factors that have potentially influenced these evaluations

ECCO essential requirements for quality cancer care : Oesophageal and gastric cancer

Background: ECCO essential requirements for quality cancer care (ERQCC) are checklists and explanations of organisation and actions that are necessary to give high-quality care to patients who have a specific type of cancer. They are written by European experts representing all disciplines involved in cancer care. ERQCC papers give oncology teams, patients, policymakers and managers an overview of the elements needed in any healthcare system to provide high quality of care throughout the patient journey. References are made to clinical guidelines and other resources where appropriate, and the focus is on care in Europe. Oesophageal and gastric: essential requirements for quality care: Oesophageal and gastric (OG) cancers are a challenging tumour group with a poor prognosis and wide variation in outcomes among European countries. Increasing numbers of older people are contracting the diseases, and treatments and care pathways are becoming more complex in both curative and palliative settings. High-quality care can only be a carried out in specialised OG cancer units or centres which have both a core multidisciplinary team and an extended team of allied professionals, and which are subject to quality and audit procedures. Such units or centres are far from universal in all European countries. It is essential that, to meet European aspirations for comprehensive cancer control, healthcare organisations implement the essential requirements in this paper, paying particular attention to multidisciplinarity and patient-centred pathways from diagnosis, to treatment, to survivorship. Conclusion: Taken together, the information presented in this paper provides a comprehensive description of the essential requirements for establishing a high-quality OG cancer service. The ERQCC expert group is aware that it is not possible to propose a one size fits all' system for all countries, but urges that access to multidisciplinary units or centres must be guaranteed for all those with OG cancer.Peer reviewe