Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: To propose a method for generating simulated images that are used to produce a contrast detail (C-D) diagram in X-ray computed tomography (CT).

Methods: We numerically generated object functions assuming ideal spheres of 7 diameters and 9 contrasts between sphere density and background density. Sphere images were calculated from the object functions by the simulation technique of image blurring based on the 3-dimensional spatial resolution measured in the CT system. The calculated sphere images were added in images of the uniform water-equivalent section of a phantom acquired at different tube currents. Obtained images were arranged according to the sphere diameter and contrast and were applied to produce the C-D diagram. For each tube current, the C-D diagram was created by a board-certified diagnostic radiologist.

Results: The calculated sphere images showed good agreements with actually acquired sphere images of the phantom. Standard deviations (SDs) in subtraction images of them were equivalent to the SD in the background region of the actual image, suggesting the accuracy of the calculated sphere images. The obtained C-D diagram showed that smaller spheres and spheres with lower contrast tended to be detected as the tube current increased.

Conclusion: The proposed method was suggested to be feasible for producing the C-D diagram for CT.

Purpose: StarGuide (GE HealthCare, Haifa, Israel), a full-ring SPECT/CT system using Cadmium Zinc Telluride (CZT) technology, allows detectors to perform a pendulum motion (sweep) during SPECT acquisition. It offers two sweep modes: continuous and step and shoot, and we investigated the impact of different sweep modes on spatial resolution and image uniformity.

Methods: Spatial resolution was evaluated using the full width half maximum (FWHM) of line source images. Image uniformity was assessed using the root mean square uniformity (%RMSU) of pool phantom images. Image reconstruction was performed using the 3D-OSEM method. Attenuation correction and spatial resolution correction were applied, and no filters were used during the reconstruction process.

Results: FWHM at the center of rotation with update 500 was 5.60±0.13 mm for continuous and 4.40±0.15 mm for step and shoot. %RMSU with update 100 was 8.94±0.38% for continuous and 9.23±0.35% for step and shoot.

Conclusion: Using the step-and-shoot sweep mode can maintain high spatial resolution.

Purpose: We developed software that can analyze central lung distance (CLD) and central skin distance (CSD) in deep inspiration breath hold (DIBH) irradiation and verified the reproducibility of the DIBH irradiation method in our hospital.

Methods: CLD and CSD were analyzed using In-house software using cine images acquired during treatment; intra- or inter-fractional motion was calculated from the obtained data and compared with other reports using systematic error (ΔΣ) and random error (Δσ).

Results: The ΔΣ and Δσ were 1.15 mm and 1.53 mm, respectively, which were the same as those reported in other reports.

Conclusion: The reproducibility of the irradiation method for left breast DIBH irradiation at our hospital is considered good. Due to its characteristics, regular and quantitative evaluation is required, and verification and evaluation are required at each facility.

Purpose: Typically, grades are compiled using spreadsheet software, and the file is then emailed with the password sent in a separate email. The government has pointed out that this method does not provide robust security. Introducing a new system is difficult due to the psychological factor of status quo bias. Therefore, we devised a new grade compilation system that uses spreadsheet software that can be easily implemented. The research aims to develop an automatic grade compilation system that implements RSA encryption.

Methods: As Excel's specifications do not allow for the display of more than 16 significant digits, we devised a method of applying modular exponentiation to modular arithmetic. The time required for encryption was measured five times and the average value was calculated.

Results: The time required for encryption was approximately 2.3 seconds, and RSA encryption is highly secure, it has the advantage of being able to distribute files with e-mail, and a paperless workflow could be established.

Conclusion: The developed system is highly secure and can be sent via email, and its automation is effective as a means of preventing disputes caused by human error.