POSTER SECTIONS Coverpage Learning objectives Background Findings and procedure details Conclusion Personal information and conflict of interest References

ECR 2024 / C-11117

Direct dose measurement method during chest CT examination by taking into consideration the X-ray incident direction

Congress:

ECR 2024

Poster Number:

C-11117

Type:

Educational Exhibit

Keywords:

Radiation physics, Radioprotection / Radiation dose, CT, Dosimetry, Education, Physics, Quality assurance

Authors:

H. Hayashi, T. Maeda, S. Goto, K. Takegami, T. Asahara, R. Nishigami, D. Kobayashi, Y. Kanazawa, K. Yamashita

DOI:

10.26044/ecr2024/C-11117

DOI-Link:

https://dx.doi.org/10.26044/ecr2024/C-11117

Findings and procedure details

<<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: Typical analysis results of a phantom experiment using five OSL dosimeters. The...

Fig. 16 shows the results of the phantom study using only one OSL dosimeter.

Fig 16: Typical analysis results of the phantom experiment using only one OSL...

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 left, the raw data showed large variations. On the other hand, as shown on the right, using our method, we were able to eliminate the influence of the incident angle of X-rays and calculate the mean value (min & max) with very small uncertainty.

Fig 17: Summary of 10 studies using one OSL dosimeter applied to the phantom. The graph...

<<Clinical Study>>

Fig. 18 shows typical analysis results of clinical data. The left and right are results for a 70-year-old man and a 67-year-old woman, respectively. It is very interesting that the absolute values of the doses differ greatly between the two patients. Using our method, we can measure the dose of each patient, which is a major technological innovation in the radiation exposure dose evaluation during CT examinations.

Fig 18: Typical analysis results of clinical data. The left and right figures are...

Fig. 19 shows the measurement results of 50 patients plotted against BMI. Measurement data shows a weak correlation with BMI. A more detailed analysis reveals that the data trends differ depending on the incident direction of the X-rays. We found that when X-rays are incident from the back direction, the intensity is adjusted due to AEC, and as a result, the exposure dose is similar regardless of BMI.

Fig 19: Summary of raw data for 50 patients. When raw data measured with OSL dosimeters...

As shown in Fig. 20, when analysis was performed using our analysis method, the influence of angle was excluded, and the estimated mean dose showed a strong BMI correlation. This result is consistent with a previous report [9]. The novel method we proposed in this paper is a very powerful tool as a radiation dose assessment method during CT examinations.

Fig 20: Results of analysis of our method. The dose analysis results correlated well...

Fig 1: A schematic drawing to explain the difficulty in measuring the exposure dose...

Fig 2: Examples of the published data showing that the exposure dose on the patient's...

Fig 3: Comparison of dose measurement methods between the conventional (left) and...

Fig 4: The concept of our novel idea to establish direct exposure dose measurement....

Fig 5: Experimental equipment used in this study. A CT scanner having 96 rows of...

Fig 6: A typical example (concept) of analysis flow. Dose measurement was performed by...

Fig 7: Concept of our analysis procedure. We assumed the surface dose of the human...

Fig 8: The overall picture of our analysis scheme. To analyze the experimental data,...

Fig 9: Symbol, description and illustration of functions which are used in our...

Fig 10: Mathematical functions used in the algorithm (part 1/3). Detailed explanations...

Fig 11: Mathematical functions used in the algorithm (part 2/3). Detailed explanations...

Fig 12: Mathematical functions used in the algorithm (part 3/3). Detailed explanations...

Fig 13: A detailed explanation of the algorithm to derive the incident angle of X-rays...

Fig 14: Clinical examination conditions and patient details. Dosimetry was performed on...