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.

Purpose: Recently, a new method has been devised to measure the anisotropic 2-dimensional noise power spectrum (2D-NPS) in computed tomography. The 2D-NPS varied with the X-ray tube angle θ in the helical scan; it was defined as 2D-NPS_θ. However, the method requires many scans to obtain the 2D-NPS_θ for each θ with less statistical variability and is laborious. In the present study, the 2D-NPS_θ was assumed to be an identical anisotropic 2D-NPS that rotated around the origin of the spatial frequency domain in conjunction with the rotation of the X-ray tube. We defined the identical 2D-NPS as 2D-NPS_rot and proposed its measurement method with fewer scans. Methods: The 2D-NPS_θ (θ from 0° to 180° in an increment of 30°) were obtained from noise images acquired by a hundred scans of a water phantom. In the proposed method, the 2D-NPS_θ were obtained from noise images by 2 scans, rotated backward around the origin by θ to generate the identical 2D-NPS, and averaged to generate the 2D-NPS_rot. Results: The 2D-NPS_rot, when it was rotated by θ, agreed well with the corresponding 2D-NPS_θ. Absolute values of the mean and standard deviation of percentage errors of the 2D-NPS_rot with the corresponding 2D-NPS_θ at each θ were less than 0.70% and 6.12%, respectively. Conclusion: The proposed method was suggested to be valid for simple measurement of anisotropic 2D-NPS.

Purpose: Image-guided radiation therapy using cone-beam computed tomography (CBCT) for prostate cancer is problematic due to the increasing exposure dose at each treatment session. This study aimed to evaluate the effect of exposure dose reduction using bismuth sheets for pelvic CBCT. Methods: Using a radiophotoluminescence dosimeter (GD-352M) and CBCT imaging conditions with three X-ray tube rotation angles (292°–88°, 92°–248°, and 92°–88°), absorbed doses were measured in the rectum, anterior and posterior bladder walls, right and left pelvic subcutaneous at 5 cm superior the prostate center of the pelvic phantom and in a testis. Next, the same measurements were performed when these measurement points were covered with a bismuth sheet. Results: The absorbed doses at 92°–248° with the bismuth sheets were reduced by 31.3% from 16.3±0.2 mGy to 11.2±0.2 mGy for the rectum and by 57.1% from 45.0±2.7 mGy to 19.3±1.0 mGy for the testis, which were the lowest among the imaging conditions. Although the anterior and posterior bladder walls were the highest dose at 48.7±11.5 and 20.2±0.4 mGy, the high reduction rates of 42.0% and 36.9%, respectively. Conclusion: From the viewpoint of the exposure risk to the bladder, rectum, and testis, using bismuth sheets and the X-ray tube rotation angle of 92°–248° effectively reduced the exposure dose.

Purpose: Japanese normal databases (NDB) for quantitative evaluation of ^99mTc myocardial perfusion SPECT have traditionally been created by the filtered back projection (FBP) method but are also applied to the iterative reconstruction (IR) method in some institutions. Although creating the NDB specifically for the IR method is desirable, it has not been done partly due to the ethical aspects of creating an institution-specific database. This study investigated the impact of using NDBs created by the FBP method on quantitative evaluations performed with the IR method. Methods: We analyzed single-photon emission computed tomography (SPECT) images from patients undergoing myocardial perfusion study in two hospitals with three SPECT vendors. Images were processed with and without various corrections, and a polar map was created by QPS software using a 17-segment model to obtain %uptake and scores. The effects of the reconstruction and correction methods were evaluated to determine the difference in the number of local segmental analyses by coronary artery territories. Results: In most segments, quantitative values showed no significant difference across device types, with or without corrections. However, both choices of the SPECT device and correction methods influenced the scores in specific coronary artery regions. Application of attenuation correction resulted in lower defect scores in the right coronary artery region. Conclusion: Applying FBP-derived NDB to the IR method generally yielded a consistent patient diagnosis in terms of defect score analysis. However, since the quantitative evaluation was partly affected by various correction methods and devices, recognizing these characteristics is crucial for enhancing diagnostic accuracy.

Purpose: The objective of this study was to quantitatively evaluate and compare the image contrast and image quality of several recently developed CT-like images (oZTEo, LAVA, MERGE). Methods: Using a self-made phantom created with a GE Healthcare (Milwaukee, WI, USA) MRI Pioneer 3.0T and pig leg bone, along with four types of tissue-mimicking phantoms, we compared cortical bone, contrast-to-noise ratio (CNR), signal change ratio of the tissue-simulating phantom, and visual evaluation. Results: CR and CNR were lowest in the order of MERGE, LAVA, and oZTEo. The signal change ratio of background signal and visual evaluation were highest in the order of oZTEo, LAVA, and MERGE. Conclusion: In comparing CT-like images using MRI, the bone cortex could be visualized in white using black-and-white inversion in all CT-like images, and fracture lines could also be visualized. By capturing CT-like images tailored to the characteristics of each imaging sequence, it is expected that the number of examinations that can be completed using MRI alone will increase, further enhancing the usefulness of MRI.

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.