Output Factor Values Research Articles

Small radiation field dosimetry with 2-methylalanine miniature dosimeters at K-band electron paramagnetic resonance

Minidosimeters of 2-methyalanine (2MA) with millimeter dimensions were produced and tested for small radiation field dosimetry. Their performance was assessed by measuring the relative output factor (ROF), beam profile (BP) and penumbra width values and were determined for square fields of 0.5 × 0.5 , 1 × 1 , 3 × 3 , 5 × 5 and 10 × 10 cm 2 . These results were compared with those obtained for Kodak X-Omat V radiographic film. The 2MA minidosimeters (mini2MA) were irradiated with 6 MV X-rays Varian/Clinac 2100 linear accelerator with SSD of 100 cm and depth of 1.5 cm (depth for build-up equilibrium). EPR measurements were made with a K-Band (24 GHz) spectrometer. The ROF and BP results demonstrate that the dimensions of the mini2MA are adequate for the field sizes used in this experiment. The results for penumbra width indicate that the spatial resolution of the mini2MA is comparable with that of radiographic film.

Photon and electron beam dosimetry with a CVD diamond detector

The performance of a radiation detector based on a 43 μm thick polycrystalline diamond film, obtained by hot filament CVD has been tested under realistic clinical conditions of irradiation generated by conventional photon and electron beams generally used for radiotherapy purposes. The linearity of the collected charge with the dose was verified and the sensitivity per unit of the detector sensitive volume was evaluated to be 20 nC Gy −1 mm −3 with an applied electric field of 23 kV/cm. This value is of the same order as that reported for PTW natural diamond detectors (50–135 nC Gy −1 mm −3). A correction factor Δ=0.94 was found for the detector current dependence on the dose rate working under the conditions of maximum signal-to-noise ratio. However, even a Δ=1.00 may be obtained when working with higher polarization electric field but at the expense of a lower signal-to-noise ratio. When the diamond detector signals were corrected for the dose rate dependence, the Percentage Depth Signal and the Output Factor values were in agreement with the results obtained with an ionization chamber well within the experimental uncertainty (1% 1 σ).

Efficiency Measurement in the Hotel Industry: Output Factor Constrained DEA Application

ABSTRACT The purpose of this study is to measure efficiency of hotels using Data Envelopment Analysis (DEA) and to assess the applicability of the DEA technique as a performance measurement tool in the tourism industry. In this framework, the DEA model has been used in efficiency analysis with an upper limit constraint on output factor values. The scope of this study has been limited to 4- and 5-star hotels in the Turkish Riviera—Antalya. The efficiency scores obtained from the DEA indicate that 4-star hotels are more efficient than 5-star hotels.

Computer‐controlled direct TMR measurement

It is common practice to derive tissue maximum ratios (TMRs) indirectly by calculation from percent depth dose (PDD) data which are more convenient to measure using currently available automated scanners. A system has been developed, however, for the completely automatic direct measurement of TMR, using an ionization chamber which is rigidly supported at the isocenter of a teletherapy machine. The chamber is immersed in a water phantom which is moved up and down by computer control of the motorized treatment couch. Ionization current is sampled by the computer which simultaneously regulates both the radiation field size and chamber depth. This system provides a means of rapidly measuring and processing complete sets of TMR and output factor values for both square and elongated field shapes. The results of such measurements performed on the Clinac 18 accelerator are described in this paper.