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Purpose: This paper aims to measure the absorbed‐dose‐rate in a CyberKnife unit reference‐field (6cm diameter) using three ionization chambers (IC) following the new IAEA/AAPM formalism and Gafchromic film (MD‐V3‐55 and EBT3) protocol according to our work reported previously. Methods: The absorbed‐dose‐rates were measured at 90cm and 70cm SSD in a 10cmx10cm field and at 70cm SSD in a 5.4cmx5.4cm equivalent to 6cm diameter field using a linac Varian iX. All measurements were performed at 10cm depth in water. The correction factors that account for the difference between the IC response on the reference field and the CyberKnife reference field, k_(Q_msr,Q)^(f_msr,f_ref), were evaluated and Gafchromic film were calibrated using the results obtained above. Under the CyberKnife reference conditions, the factors were used to measure the absorbed‐dose‐rate with IC according to the new formalism and the calibrated film was irradiated in water. The film calibration curve was used to evaluate the absorbed‐dose‐rate in the CyberKnife unit. Results: Difference up to 2.56% is observed between dose‐rate measured with IC in the reference 10cmx10cm field, depending where the chamber was calibrated, which was not reflected in the correction factor k_(Q_msr,Q)^(f_msr,f_ref) where variations of ~0.15%‐0.5% were obtained. Within measurements uncertainties, maximum difference of 1.8% on the absorbed‐dose‐rate in the CyberKnife reference field is observed between all IC and the films Conclusion: Absorbed‐dose‐rate to water was measured in a CyberKnife reference field with acceptable accuracy (combined uncertainties ~1.32%‐1.73%, k=1) using three IC and films. The MD‐V3‐55 film as well as the new IAEA/AAPM formalism can be considered as a suitable dosimetric method to measure absorbed‐dose‐rate to water in small and non‐standard CyberKnife fields used in clinical treatments However, the EBT3 film is not appropriated due to the high uncertainty provided (combined uncertainty ~9%, k=1) This work is partially supported by Conacyt grant 127409 and PAPIITUNAM grant IN10581

Objective. In cities situated at high-altitude, the measured X-ray spectra are required to calculate the absorbed dose to water in radiobiology and medical dosimetry because of the air-density effect. This work aims to measure, in a high-altitude city, a set of X-ray spectra from an X-ray tube with tungsten anode generated at potentials of the M-series X-ray beams from NIST in the range of 20 kV and 150 kV as well as other beam qualities that have been characterized and used for dosimetry study in our group called W-series. To also measure some spectra of mammography interest in the energy range of 25 kV and 35 kV using additional filtration of rhodium (Rh), molybdenum (Mo) and silver (Ag). Approach. A tungsten anode X-ray tube with potential between 10 kV to 160 kV was used. A high-purity germanium (HPGe) detector associated with a DSPEC Jr 2.0TM digital signal processing module has been used for the spectra measurements. Prior the spectra measurements, the HPGe detector has been characterized and calibrated using several radioactive sources. Main Results. The M80 spectrum was compared to a mathematically filtered beam from Physicalisch Technische Bundesanstalt corresponding to the same potential finding a difference of 0.7% in the average energy. So, the mathematically filtered beam from PTB matches very well our M80 beam. The beams M80, M100 and M120 were also compared with calculations for the corresponding kilovoltage from an executable that calculates X-ray spectra from tungsten anode X-ray tubes in the energy range between 40 kV to 300 kV called SpekCalc. The SpekCalc reproduces qualitatively the experimental spectra, but not quantitatively, mainly for M100 and M120 beams. Significance. These spectra can be used to simulate the patient dose as well as image quality using Monte Carlo (MC) codes or to evaluate the absorbed dose in dosimetry studies