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The different tomography imaging modalities of the ESRF Medical Beamline are described and research applications are presented.

The different tomography imaging modalities of the ESRF Medical Beamline are described and research applications are presented

In Synchrotron stereotactic radiotherapy (SSR) the tumor is loaded with atoms ofhigh atomic number (Z) element, and exposed to monochromatic X-rays from a synchrotron source (50-100 keV), in stereotactic conditions. This method is under investigation at the European Synchrotron Radiation Facility (ESRF) for the treatment of brain tumors. Conventional treatment planning systems are not suitable for SSR since the beam energy, the irradiation geometry and the presence ofhigh Z elements differ from commercial systems. Therefore, SSR requires the development of new procedures for the evaluation of dose maps. Monte Carlo (MC) method offers the potential of calculating the dose in complicated geometries, made ofheterogeneous materials. MC calculations were performed using the MCNP4C general purpose code. Gel dosimetry allows accurate experimental verification ofthree-dimensional absorbed dose distributions from any irradiation geometries. In this study, the Fricke chemical dosimeter was employed for it is easy to prepare without special facilities. Various phantoms filled with Fricke gel were irradiated in SSR configuration. The dose profiles obtained were compared with MC simulations.

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml1 of iodine radiological contrast agent or cells pre-exposed with 10 mM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation.

In synchrotron stereotactic radiotherapy (SSR) the tumor is loaded with a high Z element, and exposed to monochromatic x-rays from a synchrotron source, in stereotactic conditions. The SSR treatment efficiency is related to the heavy element concentration achievable in the tumor, to the radiation energy, and the irradiation geometry [1,2]. The experimental dose verification of SSR in three dimensions with a good spatial resolution is highly desirable for radiotherapy [3]. In this study, Fricke dosimeter and Monte Carlo calculations were employed for assessing 2D dose distribution.

As stressed by clinicians (1), therapy of high grades brain gliomas can be considered as a model of therapeutic failure. Despite research efforts in many therapeutic domains, high grades gliomas are of poor prognosis. Radiation therapy is commonly used for these patients but a limiting factor of this tool is the difficulty to deliver high therapeutic dose of ionizing radiation to the tumour volume without exceeding normal tissue tolerance. In conventional external radiotherapy, the treatment of brain tumors is a delicate challenge because of energy deposit to surrounding healthy tissues. One strategy is to enhance x-rays dose deposition inside the tumor while sparing surrounding tissues, owing to injection of a contrast agent to the patient (2,3). It is possible to use computerized tomography scanner to deliver highest doses in the targeted tissue by using infused contrast material (4-6). The goal of any x-ray contrast material is to produce a gradient in cross-sections leading to a gradient in photon flux measured by the imaging device detector. The energy deposit in the vicinity of the contrast material has been assessed (2,7). Contrast agent accumulates in the tumor interstitium which is irradiated with diagnostic x-rays (lower than 150 keV) by means of a conventional scanner. The increase of dose deposit in the tumor, with regard to healthy tissues, results from the combination of two effects

In this paper we describe the results of experiments using synchrotron radiation to trigger the Auger effect in living human cancer cells treated with a widely used chemotherapy drug: cisdiamminedichloroplatinum (II) (cisplatin). The experiments were carried out at the ID17 beamline of the European Synchrotron Radiation Facility, which produces a high-fluence monochromatic beam that is adjustable from 20 to 80 keV. Cisplatin was chosen as the carrier of platinum atoms in the cells because of its alkylating-like activity and the irradiation was done with monochromatic beams above and below the platinum K-shell edge (78.39 keV). Cell survival curves were comparable with those obtained for the same cells under conventional irradiation conditions. At a low dose of cisplatin (0.1 mM, 48 h), no difference was seen in survival when the cells were irradiated above and below the K-shell edge of platinum. Higher cisplatin concentrations were investigated to enhance the cellular platinum content. The results with 1 mM cisplatin for 12 h showed no difference when the cells were irradiated with beams above or below the platinum K-shell edge with the exception of the higher cell death resulting from drug toxicity. The intracellular content of platinum was significant, as measured macroscopically by inductively coupled plasma mass spectrometry. Its subcellular localization and particularly its presence in the cell nucleus were verified by microscopic synchrotron X-ray fluorescence. This was the first known attempt at K-shell edge photon activation of stable platinum in living cells with a platinum complex used for chemotherapy. Its evident toxicity in these cells leads us to put forth the hypothesis that cisplatin toxicity can mask the enhancement of cell death induced by the irradiation above the K-shell edge. However, K-shell edge photon activation of stable elements provides a powerful technique for the understanding of the biological effects of Auger processes. Further avenues

The purpose of this work was to demonstrate the feasibility of a new imaging technique called synchrotron radiation computed tomography (SRCT). This technique leads to a direct assessment of the in vivo concentration of an iodine- or gadolinium-labeled compound. Rats bearing C6 glioma were imaged by MRI prior to the SRCT experiment. The SRCT experiments were performed after a 1.3 g I/kg (n = 5) or a 0.4 g Gd/kg (n = 5) injection. Finally, brains were sampled for histology. The SRCT images exhibited contrast enhancement at the tumor location. Ten minutes after injection, iodine and gadolinium tissular concentrations were equal to 0.80 ( +/- 0.40) mg/cm3 and 0.50 ( +/- 0.10) mg/cm3, respectively in the peripheral area of the tumor (respective background value: 0.20 +/- 0.02 to 0.10 +/- 0.01). Correlation to MRI and histology revealed that the contrast uptake occurred in the most vascularized area of the tumor. The present study summarizes the feasibility of in vivo SRCT to obtain quantitative information about iodine and gadolinium-labeled compounds. Beyond brain tumor pathology, the SRCT appears as a complementary approach to MRI and CT, for studying iodine- and gadolinium-labeled compounds by the direct achievement of the tissular concentration value in the tissue.