[Evaluation of AEC Consistency in Digital X-ray Imaging Systems].

The Japan Network for Research and Information on Medical Exposures (J-RIME) established the diagnostic reference level (DRL) and is advancing optimization of radiation protection. We believe that the difference in the imaging dose between facilities may be due to the fact that automatic exposure control (AEC) adjustment is not unified among manufacturers. The consistency of AEC is specified in JIS 4751-2-54, but it is not applicable to digital X-ray imaging systems because it is for optical density of analog X-ray imaging systems. This article evaluates the consistency of AEC in digital X-ray imaging systems. The AEC consistency was compared with the AEC-estimated dose from the air kerma (KAEC) using the phosphor-based imaging plate placed at the back of the AEC detector. We measured the AEC tube voltage and subject thickness characteristics (tracking) of four types of digital X-ray imaging systems at three facilities. In the test of tube voltage characteristics, the average KAEC values at all tube voltages were 2.37±0.04 µGy for A system, 7.30±1.44 µGy for B system, 3.53±0.13 µGy for C system, and 5.70±0.18 µGy for D system. The relative errors were +2.6 to -1.8% for A system, +25.3 to -22.6% for B system, +5.2 to -1.4% for C system, and +2.5 to -4.4% for D system. In the subject thickness characteristics test, the average KAEC values for all Al thicknesses were 2.34±0.02 µGy for A system, 5.95±0.23 µGy for B system, 4.25±1.12 µGy for C system, and 5.03±1.27 µGy for D system. The relative errors were +1.0 to -0.9% for A system, +4.1 to -5.0% for B system, +40.5 to -28.1% for C system, and +19.7 to -42.9% for D system.

[Report Based on Fiscal 2015 Diagnostic X-ray Equipment Questionnaire Survey].

We have conducted a questionnaire survey every 5 years from 1974 to grasp the existing status of X-ray equipment. This time, we will report on the results of the fiscal 2015 diagnostic X-ray equipment questionnaire survey. Compared to the previous survey on X-ray equipment, there has been a progress in the introduction of inverter type X-ray generators and image receptor systems in digital systems. We think that this transition will be occurred when the X-ray equipment are updated. In addition, there has been an increase in digital breast tomosynthesis (DBT) and the use of tungsten anodes in the X-ray tubes of mammography apparatuses. X-ray equipment management was performed in many facilities. It seems that the importance of quality control of X-ray equipment is being realized. Constancy tests corresponding to digital systems were conducted at each facility. Maintenance by manufacturers has also increased. This is considered to be because the equipment management of digital systems has become difficult. We believe that it is necessary to continue the survey on the status of diagnostic X-ray equipment.

[Report based on Fiscal 2010 Diagnostic X-ray Equipment Questionnaire Survey (conditions of X-ray units and similar equipment)].

On X-ray diagnostic technology, it is important to grasp a change of the X-ray high-voltage equipment and radiographic technique factors. The 1st questionnaire was performed in 1974, and it carried out after that every five years, and conducted 8th investigation. As a result, we requested 656 institutions and got a reply from 103 institutions. The response rate was 15.7%. For X-ray high-voltage equipment, the inverter-type device shifts to 83.6% from 73.4% of last time. X-ray high-voltage equipment will be shifted to inverter-type device the near future. For X-ray tube device, the target angle becomes more smaller than usual, and maximum anode heat content is increasing tendency. The spread of digital devices is being advanced, and especially the flat panel detector (FPD) increases in the devices. The spread of soft copy diagnoses is 73.8% for chest image diagnoses, and 49.5% for breast image diagnosis. For the device management, the ratio of institutions measured at purchase time was 91.2%. But, the ratio of institutions performed an invariability examination was 58.4%. It is required to grasp the performance of an X-ray equipment and peripheral equipment, and to perform accuracy control in order to obtain proper radiographic technique factors and imaging. In order to use it for the improvement in photography technology, we would like to continue to conduct this investigation periodically.