Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: For MRI phantom experiments, when a support such as agar is used to fix a container holding a substance to be measured, difficulties arise, such as the time and effort for support preparation and material changes occurring over time. We specifically examined super absorbent polymer (SAP) and confirmed the usefulness of SAP as a new support for MRI phantoms in terms of measurement and changes over time.

Methods: The simplicity of preparing SAP as a support, its influence on the measured values of substances, and its changes over time were compared with those of agar.

Results: Compared to agar, SAP was easier to prepare. The measured values, which were stable over time, were not markedly different from those of agar.

Conclusion: It was suggested that SAP could be useful as a new support in MRI phantom experiments in terms of measurements, procedures, techniques, and handling over time.

Purpose: To evaluate the robustness of the latest periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technology from each vendor against head movements and to investigate their characteristics for effective clinical use.

Methods: Using a phantom simulating the T2-weighted image of the human brain, images were acquired with devices from CANON MEDICAL SYSTEMS (Tochigi, Japan; hereinafter "Canon"), GE HealthCare (Chicago, IL, USA; hereinafter "GE"), Philips (Amsterdam, Netherlands), and Siemens Healthineers (Forchheim, Germany; hereinafter "SIEMENS"). The head motion patterns were divided into rotation angle dependency (single rotation and multiple rotations) and rotation frequency dependency and evaluated using structural similarity (SSIM).

Results: For rotation angle dependency, Canon was robust against small rotation angles and fine movements. Despite the rotation angle, GE was robust against movements, with deep learning reconstruction (DLR) improving correction functionality. Philips could be used with compressed sensitivity encoding (CS), and robustness varied with blade width. SIEMENS was robust against large movements. For rotation frequency dependency, results were similar across the 4 vendors.

Conclusion: The rotation angle and rotation frequency dependencies of the PROPELLER technology from the 4 vendors were quantitatively evaluated. Understanding the characteristics of PROPELLER allows for the possibility of providing diagnostic-quality images even for patients who move during head MRI exams by appropriately using PROPELLER.

We evaluated the effect of different xSPECT Bone acquisition methods on image quality and quantitative accuracy. A mixed bone-equivalent solution set to 250 HU and ^99mTc was filled with the SIM² Bone phantom. The xSPECT Bone acquisitions were performed with the step and shoot (SS) mode and two continuous modes (continuous_view, continuous_total) of the times per view, and the total acquisition times were the same as the SS mode. The radioactive concentration ratio of normal bone and tumor was set to 1 : 6. The reconstructed images were evaluated using uniformity, contrast, spatial resolution, recovery coefficient (RC) of the tumor part, and detectability. The detectability score (DS), an overall evaluation of detectability, was calculated from the results of uniformity and contrast. Uniformity of SS, continuous_view, and continuous_total methods was 29.4%, 17.4%, and 11.1%, respectively. Spatial resolution, RC, and detectability were similar among the SS mode and two continuous modes; however, the continuous modes showed good uniformity and contrast compared with the SS mode. In addition, the detectability of the continuous mode was equal to or superior to that of the SS mode.

Purpose: We evaluated the measurement accuracy and time efficiency of the tumor respiratory motion evaluation methods using a dynamic thorax motion phantom.

Methods: A total of 12 patterns of 4DCT images with different tumor displacements and artifacts were used for the measurement. Three methods were employed to measure tumor motion. The first method was the manual delineation of the tumor on each phase CT image with a treatment planning system (RTPS [Manual]). The second method was the automatic delineation of the tumor structure by deformation and copying (RTPS [Auto]). The third method was tumor motion analysis software (Simple 4D Analysis Ver.1.3.1 [Simple 4D]; Triangle Products, Chiba, Japan). For each method, the difference between the phantom motion and the measured value was determined.

Results: The differences (mean±standard deviation: SD) in the superior-inferior direction for RTPS (Manual), RTPS (Auto), and Simple 4D in the without-artifact images were -0.6 mm±0.6 mm, -5.0 mm±2.2 mm, and -1.0 mm±0.0 mm, respectively. The difference in the left-right and anterior-posterior directions was within 1 mm for all methods. Furthermore, the time required for Simple 4D was shorter than for the other methods.

Conclusion: Simple 4D showed the comparable measurement accuracy and improvement time efficiency to RTPS (Manual) and RTPS (Auto), and was useful for tumor respiratory motion analysis.

Purpose: Investigation of imaging conditions using human body equivalent phantom and neonatal phantom in portable chest radiography of newborns. Although attempts have been made to reduce dose by image processing in portable X-ray radiography of neonates, no evaluation has been made at the raw data level of the images. In this study, we investigated dose reduction from the current imaging conditions using a simulated phantom and a neonatal phantom in terms of raw data level image quality and incident surface dose.

Methods: The pixel values of each region were calculated from chest photographs of newborn infants taken at 60 kV and 2.0 mAs, and the thickness and combination of acrylic, aluminum, and copper were adjusted to create a simulated phantom with equivalent pixel values. The SdNR and incident surface dose at each site obtained from the simulated phantom were compared to obtain imaging conditions equivalent to or better than 60 kV, 2.0 mAs. The neonatal phantom was imaged, and the CNR of the processed images was compared to that of 60 kV, 2.0 mAs.

Results: SdNR and incident surface dose results showed that 62 kV, 1.8 mAs was superior. Comparison with neonatal phantoms showed no significant difference.

Conclusion: The simulated phantom was used to reproduce the clinical situation and to obtain excellent imaging conditions.

Purpose: The effects of scanning parameters such as CT system performance, CT bed geometry, and upper limb position on effective diameter (ED) and water equivalent diameter (WED) have not been assessed. The purpose of this study was to compare both ED and WED obtained with various CT systems with theoretical values and to assess their accuracy.

Methods: Jaszczak cylindrical phantom (Data Spectrum, Durham, NC, USA), NEMA IEC body phantom (AcroBio, Tokyo), and thoracic bone phantom were used in this study with and without upper limb phantom. The ED, WED, and size-specific dose estimate (SSDE) obtained using 8 types of CT systems were computed using radiation dose control software.

Results: The EDs had <5% error for all systems, but the error increased as the aspect ratio of the phantom increased. The accuracy of WED varied depending on the CT systems, with a maximum difference of 3.57 cm between systems. The influence of the upper limb depended on the shape of the bed of the CT systems, which affected the correlation between ED as well as WED and SSDE.

Conclusion: Although the ED did not show any dependence on the CT system, the accuracy of WED for fusion CT was low. We found that there are issues in the management of scanning data, including the upper limb.

Purpose: This study aimed to evaluate the influence of the scanning speed of whole-body scans on the detectability of positive vertebral bone images in bone scintigraphy.

Methods: We used SIM² bone phantom to obtain planar images equivalent to scanning speeds of 15, 17, and 20 cm/min. Receiver operating characteristic (ROC) analysis to evaluate lesion detectability and average count (Ct)/pixel, contrast ratio, and contrast-to-noise ratio (CNR) of the normal vertebral body and the simulated tumor site were measured.

Results: The average area under the ROC curves (AUC) was 0.936, 0.929, and 0.915 at speeds of 15, 17, and 20 cm/min, respectively. The average AUC at 20 cm/min was significantly lower than that at 15 cm/min (p<0.05) . However, no other significant differences were found (p=0.448, 0.139). The average Ct/pixel and CNR decreased at 15, 17, and 20 cm/min. The contrast ratio did not change.

Conclusions: The results showed that increasing the scan speed from 15 cm/min to 17 cm/min had no effect on the detection of vertebral lesions. Thus, it is possible to reduce the scan time, albeit slightly.

We investigated the impact of the tumor-to-normal bone ratio (TNR) on the concordance rate between a detectability score classified by software (DS_soft) using an automatic quantification package for bone SPECT (Hone Graph) and a detectability score classified by visual assessment (DS_visual), and considered the feasibility of applying this software to various TNR images. ^99mTc solution was filled into a SIM² bone phantom to achieve TNRs of 4, 6, and 8, performed by dynamic SPECT acquisitions performed for 12 minutes; reconstructions were performed using ordered subset expectation maximization at timepoints ranging from 4 to 12 minutes. This yielded a total of 384 lesions (96 SPECT images). We investigated the weighted kappa (κ_w) coefficient between DS_soft and DS_visual at various TNRs and evaluated the change in analysis accuracy before and after applying newly created analysis parameters. DSs were defined on a 4-point scale (4: excellent, 3: adequate, 2: average, 1: poor), and visual evaluations were conducted by three board-certified nuclear medicine technologists. The κ_w coefficients between DS_soft and DS_visual were 0.75, 0.97, and 0.93 for TNRs 4, 6, and 8, respectively, with each κ_w coefficient being significant (p<0.01). In the TNR 4 image group, κ_w coefficients significantly increased with the implementation of new parameters proposed in this study. We concluded that the software's automatic analysis would be closer to a visual assessment within the TNR range of 4-8 and that applying new parameters derived from this study to images with TNR 4 further improves the software's automatic analysis accuracy of DS_soft. We suggest that software will be a useful tool for optimizing bone SPECT imaging techniques.

Purpose: The purpose of this study was to evaluate the protective performance of several new radiation-protective clothing and to clarify issues of quality control.

Methods: The composition of the shielding elements was analyzed using X-ray fluorescence analysis, and the energy spectrum of transmitted X-rays was measured. Furthermore, the lead equivalent and uniformity were measured from the transmitted X-ray doses according to Japanese industrial standards (JIS). Uniformity was evaluated by transmitting X-ray images of each radiation protective clothing in addition to the conventional method.

Results: The energy spectrum showed K-absorption edges of lead, bismuth, tin, etc., which were detected in the composition analysis. The multi-layered protective material maintained higher shielding ability at high tube voltages. In addition, X-ray images of the radiation-protective clothing showed uneven density and dots, and the differences in uniformity measurement methods and points that didn't meet the required shielding capacity were seen.

Conclusion: The current JIS does not allow accurate evaluation of the lead equivalent and uniformity, so visual evaluation of X-ray images is important. It is necessary to establish standardized standards for quality control performed by each facility.

Purpose: Patients who were administered radiopharmaceuticals can be a source of radiation exposure to sonographers. This study aimed to identify factors associated with radiation exposure to breast sonographers from patients administered radiopharmaceuticals for bone scanning.

Methods: The exposure dose of six sonographers was measured during breast sonography in 59 patients administered ^99mTc-HMDP. We predicted the following factors to be related to exposure dose: time interval between administration and sonography, sonography examination time, estimated radioactivity at sonography, sonographer's years of experience, and patients' clinical data (age, renal function and surgical procedure). Spearman's rank correlation coefficient was used to examine the relationship between radiation dose and the aforementioned factors.

Results: The mean±standard deviation of the exposure dose for the sonographers was 9.3±3.8 µSv. The time interval between administering the radiopharmaceutical agent and sonography, the sonography examination time and estimated radioactivity at sonography were found to be factors related to the exposure of the sonographer. The exposure dose increased as a function of the shorter time interval, longer examination time and higher estimated radioactivity at sonography.

Conclusion: The time interval between drug administration and sonography, sonography examination time and estimated radioactivity at sonography contributed to the increased dose to breast sonographers. Although we considered that the exposure dose of sonographers would not possibly exceed the dose limit in the present study, we suggested that radiological technologists need to educate the physicians requesting sonography, and the sonographers about the radiation exposure in nuclear medicine.