Purpose: The purpose of this study was to avoid the influence of background activity in the calculation of heart to contralateral ratio (H/CL) in ^99mTc-pyrophosphate (PYP) scintigraphy for diagnosis of cardiac amyloidosis. Therefore, we investigated the utility of the H/CL calculation method using ray-summation (ray-sum) images created by multi-planar reconstruction and summing slices of the heart range from single-photon emission computed tomography (SPECT) images. Methods: The subjects were 33 patients who underwent ^99mTc-PYP planar and SPECT/CT at 3 hours after injection. Ray-summation axial (ray-sum axial) and ray-summation coronal (ray-sum coronal) images were created and H/CL was calculated. We compared the differences in sensitivity, specificity, accuracy, and area under the curve (AUC) between the conventional method and our method, and calculated the cutoff values. Results: Comparison of the conventional method and our method showed no significant difference in sensitivity and AUC, while specificity was significantly improved to 97% (p=0.003) of ray-sum axial image and 90% (p=0.01) of ray-sum coronal image, and accuracy was significantly improved to 94% (p=0.02) of ray-sum axial image. Conclusion: The H/CL calculation method using ray-sum images had higher diagnostic performance than the conventional method, with optimal cutoff of ray-sum axial images 3.07 and ray-sum coronal images 2.77.

Purpose: We aimed to investigate the usefulness of iViz air ver.4 Convex (FUJIFILM, Tokyo) as a tool to determine the bladder capacity before prostate radiotherapy by comparing it with the existing BladderScan BVI 6100 (Verathon Inc., Bothell, Washington). Methods: We investigated the usefulness of iViz air as a tool to determine the bladder capacity before prostate radiotherapy by comparing it with the current BladderScan. Results: The absolute value of each error rate was approximately 30.9%±27.2% and 26.4%±18.9% for the BladderScan and iViz air, respectively, with no significant differences between the instruments (p=0.16). Evaluated by urine volume, the mean error rates for bladder volumes >50 ml were 26.9%±19.0% and 26.1%±18.5% for the Bladder Scan and iViz air, respectively, with no significant differences (p=0.56). However, the BladderScan and iViz air had significantly higher error rates of 89.5%±52.5% and 31.5%±25.1%, respectively, if the bladder volume was <50 ml (p=0.005). Conclusion: The iViz air has limited measurement error to confirm images, especially in limited volumes, suggesting that it is a useful bladder capacity measurement device in performing prostate radiotherapy.

The purpose of this study were to evaluate the residual volume of radiopharmaceuticals in the three-way stopper and syringe used during radiopharmaceutical administration and the effect of washing. The three-way stoppers were a top injector tube, a top three-way stopper, and a Nipro three-way stopper with a needle. Sodium pertechnetate [^99mTc] injection (^99mTcO₄⁻) was used to compare the residual volume of radiopharmaceuticals in the three-way stopper and syringe without and with washing. Clinically, 137 patients who underwent cerebral blood flow scintigraphy, dopamine transporter scintigraphy, and bone scintigraphy were included. N-isopropyl-p-[¹²³I]iodoamphetamine (¹²³I-IMP), ¹²³I-N-ω-fluoropropyl-2β-carboxymethoxy-3β-(4-iodophenyl)nortropane (¹²³I-FP-CIT), and ^99mTc-methylene diphosphonate (^99mTc-MDP) were used to compare the residual volume of radiopharmaceuticals in the three-way stopper and syringe without and with washing. The residual volume depended on the type of three-way stopper and radiopharmaceutical used. The residual volume could be reduced by washing, but the effect depended on the type of three-way stopper and radiopharmaceutical used. The residual volume of radiopharmaceuticals in three-way stoppers and syringes can be determined and subtracted to achieve more accurate dose control.

Lowering the dose limit for the lens of the eye incorporated into the Regulation on Prevention of Ionizing Radiation Hazards, effective on April 2021, and dose reduction will become more and more important in the field of radiation. Radiation protective cloth is used as a protective equipment in fluoroscopy rooms. Although it is usually used to protect staff from radiation exposure during endoscopic retrograde cholangiopancreatography, we investigated whether there is a way to use it for procedures in clean areas. Assuming ureterostomy fistula replacement in urology, the protective cloth was suspended on the side of the patient’s head and posterior aspect of the tube, and the distance between the anterior aspect of the X-ray tube and the patient’s foot was 55 cm. As a result of measuring the dose rate, a 10% dose reduction was obtained for the lens of the eye of the surgeon, and the distribution of air dose rate in the examination room was significantly reduced. Although scattered radiation from the radiation protection cloth appeared in some areas, the radiation dose to the patient was reduced throughout the body, and a high degree of radiation protection was obtained, especially for the lens of the eye. It is expected that the radiation protection cloths may be useful even when the length of the cloths is limited due to the cleanliness of the area.

Purpose: Dark band (DB) artifact in head and neck computed tomography (CT) is caused by beam hardening (BH), and decreased CT values in the X-ray target become a problem. Therefore, we investigated whether it is possible to reduce DB artifact in the head and neck with a compensation filter. Methods: We made 2 types of filters with alcohol and water. We set each of these filters in front of the chest phantom’s clavicle and evaluated DB artifact. The evaluation method measured CT values in the DB artifact area and background (BG) area by changing each compensation filter thickness and the distance between the chest phantom’s surface and each compensation filter. In addition, we measured average standard deviation (SD) in the BG area by the presence of each compensation filter. Results: CT values in the DB artifact area were approximate to those in the BG area by setting the thickness of each compensation filter to more than 30 mm. Furthermore, these CT values were decreased by separating the distance between the chest phantom’s surface and each compensation filter. Average SD in the BG area showed no significant difference between no filter and each compensation filter. Conclusion: It was possible to reduce DB artifact by a compensation filter for DB.

In recent years, gadolinium ethoxybenzyl diethylenetriamine pantaacetic acid (Gd-EOB-DTPA) has been commonly used in magnetic resonance imaging (MRI) for liver contrast studies. The purpose of this study was to investigate the effect of Hyper SENSE factor on contrast in the Gd-EOB-DTPA hepatocyte phase. The subjects were 21 patients [16 males and 5 females, aged 50–94 years (mean age 68±12years)] who underwent hepatic contrast-enhanced MRI with Gd-EOB-DTPA from March 2021 to December 2021. The contrast ratios (CRs) of liver/spleen and liver/tumor were measured when the Hyper SENSE factor was changed to 1.0, 1.4 and 1.8. As a result, there was no statistically significant difference in signal intensity and CR with the change in the Hyper SENSE factor. In this study, the acquisition time can be shortened without decreasing the CR; therefore, it was suggested to improve MR images to avoid motion artifact.

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 (K_AEC) 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 K_AEC 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 K_AEC 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.