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Contrast-enhanced radiotherapy is an innovative treatment that combines the selective accumulation of heavy elements in tumors with stereotactic irradiations using medium energy X-rays. The radiation dose enhancement depends on the absolute amount of iodine reached in the tumor and its time course. Quantitative, postinfusion iodine biodistribution and associated brain perfusion parameters were studied in human brain metastasis as key parameters for treatment feasibility and quality. Twelve patients received an intravenous bolus of iodinated contrast agent (CA) (40 mL, 4 mL/s), followed by a steady-state infusion (160 mL, 0.5 mL/s) to ensure stable intratumoral amounts of iodine during the treatment. Absolute iodine concentrations and quantitative perfusion maps were derived from 40 multislice dynamic computed tomography (CT) images of the brain. The postinfusion mean intratumoral iodine concentration (over 30 minutes) reached 1.94 ± 0.12 mg/mL. Reasonable correlations were obtained between these concentrations and the permeability surface area product and the cerebral blood volume. To our knowledge, this is the first quantitative study of CA biodistribution versus time in brain metastasis. The study shows that suitable and stable amounts of iodine can be reached for contrast-enhanced radiotherapy. Moreover, the associated perfusion measurements provide useful information for the patient recruitment and management processes.

1. There is an increasing demand in diagnostic radiology for extracting additional morphological and functional quantitative parameters from three-dimensional computed tomography (CT) images. Synchrotron radiation computed tomography (SRCT) is the state-of-the-art method in preclinical X-ray CT, because its performance is close to the theoretical limits in terms of accuracy and precision. 2. The SRCT method with monochromatic X-ray beams yields absolute high-Z element contrast agent concentrations, without errors arising from beam hardening or scatter artefacts, by using digital subtraction techniques of the sinograms. Each pixel of the reconstructed difference images provides a quantitative concentration versus time curve of inhaled or injected high-Z contrast agents (xenon or iodine) with a high sensitivity. This is the key point of two functional imaging techniques that were developed at the European Synchrotron Radiation Facility: brain perfusion and lung function (ventilation and perfusion). 3. These two imaging techniques provide parametric images expressed in absolute perfusion parameters (blood volume, blood flow, mean transit time and capillary permeability) or ventilation parameters (lung volume, regional lung ventilation, bronchial lumen size, regional airway and lung compliance) with a high accuracy and precision. 4. The aim of the present brief review is to give a snapshot of the status and perspectives of these two imaging techniques, with emphasis on the performances and interests for functional imaging. Two separate sections will then describe the results obtained so far using SRCT as an in vivo functional imaging tool for measuring changes in haemodynamics and ventilation, in the investigation of experimental pathophysiology and in the effects of therapeutic intervention.

Purpose: Heavy-atom-enhanced synchrotron stereotactic radiotherapy (SSR) is a treatment that involves selective accumulation of high-Z elements in tumors followed by stereotactic irradiation with X-rays from a synchrotron source. The purpose of this study was to determine whether the efficacy of iodine-enhanced SSR could be further improved in the F98 rodent glioma model, by using a concomitant injection of an iodinated contrast agent and a transient blood-brain barrier opener (mannitol) during irradiation., Methods and Materials: Fourteen days after intracerebral inoculations of F98 cells, the rats were irradiated with 50-keV X-rays while receiving an infusion of hyperosmotic mannitol with iodine, either intravenously or via the carotid (9 to 15 rats per group, 117 rats total)., Results: For doses

Purpose: Enhancement of the radiation dose delivered to a brain tumor can be achieved by infusing an iodinated contrast agent to the patient and irradiating with kilovoltage X-rays in computed tomography (CT) mode. Synchrotron sources, providing monochromatic tunable intense beams, are ideal for this treatment. The aim of this study is to assess in vivo the efficiency of this novel radiotherapy modality, Synchrotron Radiation CT-Therapy., Materials and Methods: Intracranial implantations of 10(5) F98 glioma cells were performed on 18 Fisher 344 rats. Six rats were untreated controls, six received radiotherapy alone (10 Gy in the tumor by single fraction tomographic irradiation at 50 keV), and six received the same radiotherapy treatment under a continuous infusion of iodinated contrast agent., Results: The rats that received contrast agent during radiotherapy survived significantly longer than rats that received radiotherapy alone (p = 0.025). Mean survival times (mean +/- SD) were 12.3 +/- 0.8, 14.8 +/- 2.8, and 18.2 +/- 1.3 days; median survival times were 12.5, 15, and 18 days (untreated controls, irradiated without iodine, irradiated with iodine, respectively). The increase in life spans was 20% and 44% for the rats irradiated without or with iodine, respectively., Conclusions: This method of radiation dose enhancement in brain tumors with synchrotron radiation significantly increases survival and appears highly promising.