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Glioblastoma multiforme (GBM) is considered the most malignant form of primary brain tumor. Despite multimodal treatment, prognosis remains poor. Ketogenic diet (KD) has been suggested for the treatment of GBM. In this study, the syngenic, orthotopic GL261 mouse glioma model was used to evaluate the effects of KD on the metabolic responses of the tumor using 7T magnetic resonance imaging/spectroscopy. GL261 cells were injected into the caudate nucleus of mice. Following implantation, animals were fed with standard chow or underwent a KD. 18 days after initiating the diet, mice fed with KD displayed significantly higher plasmatic levels of ketone bodies and survived longer than those fed with the standard diet. Decreased concentrations of gamma-aminobutyric acid, N-Acetyl-Aspartate and N-acetylaspartylglutamate were found in tumor tissue after 9 days into the KD, while a huge increase in beta-hydroxybutyrate (bHB) was detected in tumor tissue as compared to normal brain. The accumulation of bHB in the tumor tissue in mice undergoing the KD, may suggest either elevated uptake/release of bHB by tumor cells, or the inability of tumor cells in this context to use it for mitochondrial metabolism. [ABSTRACT FROM AUTHOR]

Background and aims: Dose administration accuracy in radiosurgery (RS) treatments is of paramount importance to guarantee both the clinical outcome and the absence of severe toxicities. A comprehensive delivery quality assurance (DQA) program is therefore mandatory. In this study we evaluated the IBA myQA SRS® (IBA Dosimetry, Germany) high-resolution solid-state detector in a new context of RS delivered using CyberKnife® (Accuray, US) 6 MV robotic linac. The detector’s performance was investigated in periodic machine DQA and patientspecific treatments verification. Methods: MyQA SRS [Figure 1] is composed of a 140×120 mm CMOS matrix with 400 um resolution, allocated in a cylindrical ABS phantom topped by a hemispheric cap. Dose calibration was ensured delivering 500 cGy to the matrix central area by an ad-hoc optimized plan. System performance evaluation included: periodic dosimetry tests (dose linearity and reproducibility, output factors, off-axis-ratios) [Figure 2], detector angular response and dose rate dependence (in the clinically useful source-to-surface range between 650 mm and 1200 mm), and variable aperture IRIS® collimator field size measurement. For patient-specific DQA, the system performance was studied for various RS intracranial targets considering complete optimized plans and plans corrected taking into account the device angular response (delivered after removal of beams above a threshold angle selected according to the angular dependence analysis). An evaluation by 3% 1 mm Gamma Index was performed [Figure 3]. Results: Detector response for periodic DQA tests was always found to be in accordance with the authors center’s commissioning data. Dependence from dose rate was confirmed, corroborating the manufacturer requirement of a dose calibration specific for each dose rate of interest. Field dimensions for the IRIS collimator were consistent with commissioning values, with an accordance within 0.4 mm. Finally, angular dependence tests resulted in a signal decay greater than 5% when beams outside a ±50° amplitude cone with respect to the patient’s anterior-posterior direction were delivered. Concerning patient-specific QA, >50° angled beams elimination from treatment delivery led to an improvement in Gamma Index passing rates ranging between +3% and +115%, depending on target and plan characteristics. Conclusions: IBA myQA SRS proved to be a suitable device for constancy and daily DQA, providing highresolution real-time results and showing a potential for replacing radiochromic films in many dosimetric analyses. Preliminary patient-specific QA Gamma tests showed high passing rates once angular dependence corrections were performed, even when high complexity treatments, such as the trigeminal neuralgia case, were considered. [ABSTRACT FROM AUTHOR]