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Background: The aim of this study was to describe the clinical implementation of the Calypso system with its potential impact on the treatment delivery. Materials and methods: The influence of the electromagnetic array was investigated on the kilovoltage cone beam computed tomography (kV-CBCT) image quality using the CATPHAN 504 CBCT images. Then, the QFix kVue Calypso couch top and the array attenuation, and their dosimetric influence on the Volumetric modulated arc therapy (VMAT) treatments of prostate was evaluated. Results: Regarding the image quality, a significant increase of noise (p < 0.01) was detected with the array in place, resulting in a significant decrease in signal noise ratio (SNR) (p < 0.01). No difference in absolute contrast was observed. Finally, there was a significant decrease in contrast noise ratio (CNR) (p < 0.01) even if the deviation was only of 2.5%. For the dosimetric evaluation, the maximum attenuation of the couch was 12.02% and 13.19% for X6 and X6 flattening filter free (FFF), respectively (configuration of rails out). Besides, the mean attenuation of the array was 1.15% and 1.67% for X6 and X6 FFF, respectively. For the VMAT treatment plans, the mean dose was reduced by 0.61% for X6 and by 0.31% for X6 FFF beams when using the electromagnetic array. Conclusions: The Calypso system does not affect significantly the kV-CBCT image quality and the VMAT plan dose distribution. [ABSTRACT FROM AUTHOR]

Recently, the addition of nanoparticles (NPs) has been proposed as a new strategy to enhance the effect of radiotherapy particularly in the treatment of aggressive tumors such as glioblastoma. The physical processes involved in radiosensitisation by nanoparticles have been well studied although further understanding of its biological impact is still lacking, and this includes the localisation of these NPs in the target cells. Most studies were performed with NPs tagged with fluorescent markers. However, the presence of these markers can influence the NPs uptake and localisation. In this study, a set of methods was used to unambiguously and fully characterise the uptake of NPs, their co-localisation with cell organelles, and their radiosensitising efficacy. This set was applied to the case of gadolinium-based nanoparticles (GdBN) used to amplify the radiation killing of U87 glioblastoma cells extracted from highly aggressive human tumor. For the first time, Synchrotron Radiation Deep UV (SR-DUV) microscopy is proposed as a new tool to track label-free GdBN. It confirmed the localisation of the NPs in the cytoplasm of U87 cells and the absence of NPs in the nucleus. In a second step, Transmission Electron Microscopy (TEM) demonstrated that GdBN penetrate cells by endocytosis. Third, using confocal microscopy it was found that GdBN co-localise with lysosomes but not with mitochondria. Finally, clonogenic assay measurements proved that the presence of NPs in the lysosomes induces a neat amplification of the killing of glioblastoma cells irradiated by gamma rays. The set of combined experimental protocols--TEM, SR-DUV and confocal microscopy--demonstrates a new standard method to study the localisation of label-free NPs together with their radiosensitising properties. This will further the understanding of NP-induced radiosentisation and contribute to the development of nanoagents for radiotherapy. [ABSTRACT FROM AUTHOR]

One objective of modern neuroimaging is to identify markers that can aid in diagnosis, monitor disease progression, and impact long-term drug analysis. In this study, physiopathological modifications in seven subcortical structures of patients with mild cognitive impairment (MCI) due to Alzheimer's disease (AD) were characterized by simultaneously measuring quantitative magnetic resonance parameters that are sensitive to complementary tissue characteristics (e.g., volume atrophy, shape changes, microstructural damage, and iron deposition). Fourteen MCI patients and fourteen matched, healthy subjects underwent 3T-magnetic resonance imaging with whole-brain, T1-weighted, T2*-weighted, and diffusion-tensor imaging scans. Volume, shape, mean R2*, mean diffusivity (MD), and mean fractional anisotropy (FA) in the thalamus, hippocampus, putamen, amygdala, caudate nucleus, pallidum, and accumbens were compared between MCI patients and healthy subjects. Comparisons were then performed using voxel-based analyses of R2*, MD, FA maps, and voxel-based morphometry to determine which subregions showed the greatest difference for each parameter. With respect to the micro- and macro-structural patterns of damage, our results suggest that different and distinct physiopathological processes are present in the prodromal phase of AD. MCI patients had significant atrophy and microstructural changes within their hippocampi and amygdalae, which are known to be affected in the prodromal stage of AD. This suggests that the amygdala is affected in the same, direct physiopathological process as the hippocampus. Conversely, atrophy alone was observed within the thalamus and putamen, which are not directly involved in AD pathogenesis. This latter result may reflect another mechanism, whereby atrophy is linked to indirect physiopathological processes. [ABSTRACT FROM AUTHOR]

Background: This study's aim was to develop our dosimetric methodology using a commercial workstation for the routine evaluation of the organs at risk during peptide receptor radionuclide therapy (PRRT) with 177Lu.Methods: First, planar and SPECT sensitivity factors were determined on phantoms. The reconstruction parameters were optimized by SPECT/CT image acquisition using a NEMA IEC phantom containing a 500 ml bottle of 177Lu, to simulate a kidney. The recovery coefficients were determined on various phantoms. For the red marrow, this was calculated using a NEMA IEC phantom that contained a centrally placed bottle of 80 ml of 177Lu (to model the L2-L4 red marrow) flanked by two 200 ml bottles with 177Lu to simulate the kidneys.Then, SPECT/CT images were acquired at 4, 24, 72, and 192 h after injection in 12 patients with neuroendocrine tumors who underwent PRRT with 177Lu-DOTATATE. SPECT data were reconstructed using the iterative ordered subset expectation maximization (OSEM) method, with six iterations and ten subsets, attenuation, scatter, recovery resolution corrections, and a Gaussian post-filter of 0.11 cm. The liver, spleen, kidneys, and red marrow dose per administered activity (AD/A admin) values were calculated with the Medical Internal Radiation Dose (MIRD) formalism and the residence times (Dosimetry toolkit® application) using standard and CT imaging-based organ masses (OLINDA/EXM® V1.0 software).Results: Sensitivity factors of 6.11 ± 0.01 and 5.67 ± 0.08 counts/s/MBq were obtained with planar and SPECT/CT acquisitions, respectively. A recovery coefficient of 0.78 was obtained for the modeled L2-L4 red marrow. The mean AD/A admin values were 0.43 ± 0.13 mGy/MBq [0.27-0.91] for kidneys, 0.54 ± 0.58 mGy/MBq [0.12-2.26] for liver, 0.61 ± 0.13 mGy/MBq [0.42-0.89] for spleen, and 0.04 ± 0.02 mGy/MBq [0.01-0.09] for red marrow. The AD/A admin values varied when calculated using the personalized and standard organ mass, particularly for kidneys (p = 1 × 10−7), spleen (p = 0.0069), and red marrow (p = 0.0027). Intra-patient differences were observed especially in organs close to or including tumor cells or metastases.Conclusions: The obtained AD/A admin values were in agreement with the literature data. This study shows the technical feasibility of patient dosimetry in clinical practice and the need to obtain patient-specific information. [ABSTRACT FROM AUTHOR]