Recently, patients have more opportunities to have CT examinations [1] and the radiation doses to the patients have also increased. It is increasingly important to consider the balance between radiation dose and image quality [2]. In order to evaluate an exposure dose during CT scan, the CT dose index (CTDI) is often used to evaluate the exposure dose of a standardized patient [3] and is built in current CT scanners. Actually, the radiation dose to patients varies depending on the patient size and scanning parameters....

Fig. 2 shows the experimental materials. We measured X-ray spectra in a free-air and at the surface of cylindrical acrylic phantoms (T40027, PTW) having diameters of 16 cm and 32 cm. Acrylic scatterers were then placed in free-air (Fig. 3(a)) and on the phantoms (Fig. 3(b)). Here, volumetric CT scans were performed using a CT scanner (SOMATOM Force, Siemens Healthineers), and Compton-scattered X-rays at 90 degrees [10] were measured using a CdTe spectrometer (type123, EMF Japan). To reduce the pile-up effect and dead time of...

As shown in Fig. 7, the background X-rays were experimentally detected and subtracted. In the right figure, the red line shows the spectrum corrected for the response function of the CdTe spectrometer, the X-ray energy and the probability of the Compton-scattering effect. Using corrected spectra (see Fig. 8(a-1)), the CFs of the diagnostic X-ray of 80 kV derived from the experiments and Tucker’s formula were plotted as gray data of Fig. 8(b-1). The experimental results were in good agreement with the Monte-Carlo simulation. This fact...

In this study, the CFs for small-type OSL dosimeters were determined taking into consideration the X-ray spectra during the volumetric CT scan. From the results in experiment and Monte-Carlo simulation, we clarified that the quality of X-rays exposed to the dosimeter should be considered for the proper calibration to measure the ESD in CT examination. Additionally, we concluded that the uncertainty of the CFs was estimated to be at most 5% when the dose calibration is performed using the spectra at the surface of the...

Kazuki Takegami, M.S., R.T. [email protected] Hiroaki Hayashi, Ph.D [email protected] Kanazawa University, Japan HP_HayashiLab.

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