Medical radiation exposure in Japan is among the highest in the world [1]. One problem is that the public has little opportunity to receive information concerning the amount of radiation exposure they have been exposed to. Currently, CT scanning accounts for 62% of the amount of medical radiation exposure [2] and must be managed appropriately. One solution is to develop a method for measuring the actual dose of radiation a patient receives during CT examinations.<<Purpose>> In this presentation, we would like to propose a novel...

Materials used in this study are shown in Fig. 5. A CT scanner of 96 rows of detectors was used in the conventional scan mode with a tube voltage of 120 kV, pitch factor of 1.2, and effective tube-current time products of 150 mAs were applied. A cylindrical water phantom being 20 cm in a diameter and the chest area of a human-body phantom were used in this study. Dosimetry was performed using OSL dosimeters based on have a construction of Al2O3 [6,7,8]. This dosimeter...

<<Phantom Study>> Fig. 15 shows the results of the phantom study using five OSL dosimeters. The estimated dose distribution (green line) agrees well with the actual measured values (red closed circles). This indicates that the analysis of the proposed method works correctly.[Fig 15] Fig. 16 shows the results of the phantom study using only one OSL dosimeter.[Fig 16] In order to perform further quantitative analysis, the data obtained from 10 trials were analyzed as shown in Fig. 17. As shown in the graph on the...

In conclusion, we investigated a novel dosimetry method to be used during CT examinations. Our method identifies the incident direction of X-rays by analyzing the noise components of CT images. Then, a mathematical function predetermined from a phantom experiment is applied to measured dose data. This can be used to determine the patient's surface radiation dose distribution from only one point dose data.<<Limitations>> Our method uses a correction factor estimated from a standard-type human body phantom. Therefore, actual measurements of patients that are different than...

H. Hayashi: Nothing to disclose T. Maeda: Nothing to disclose S. Goto: Nothing to disclose K. Takegami: Nothing to disclose T. Asahara: Nothing to disclose R. Nishigami: Nothing to disclose D. Kobayashi: Nothing to disclose Y. Kanazawa: Nothing to disclose K. Yamashita: Nothing to disclose

Berrington de González A, Darby S. Risk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries. Lancet. 2004 Jan 31;363(9406):345-51. doi: 10.1016/S0140-6736(04)15433-0. Mahesh M, et al. Patient Exposure from Radiologic and Nuclear Medicine Procedures in the United States and Worldwide: 2009-2018. Radiology. 2023 Apr;307(1):e221263. doi: 10.1148/radiol.221263. Tominaga M, et al., Measurements of multidetector CT surface dose distributions using a film dosimeter and chest phantom. Med Phys. 2011 May;38(5):2467-78. doi: 10.1118/1.3570769. Takegami K, et al., Entrance surface dose measurements using a small...