Investigation of the relation between administered dose and image quality for pediatric 99mTc-DMSA renal scintigraphy: clinical study applying the JSNM (Japanese Society of Nuclear Medicine) pediatric dosage card : The Japanese Society of Nuclear Medicine Technology (JSNMT), the Optimization of Imaging Technique Committee for Pediatric Nuclear Medicine Studies.

PURPOSE: In 2013, the Japanese Society of Nuclear Medicine (JSNM) announced consensus guidelines for pediatric nuclear medicine. These JSNM guidelines proposed use of lower administered doses compared with traditionally determined doses, which were estimated from age, weight or body surface area (BSA) based on the administered dose for adults in Japan. When the JSNM guidelines are used, the relationship between this recommended administered dose and image quality remains unclear. In this study, we clarified the relationship between administered dose and image quality for pediatric 99mTc-DMSA renal scan retrospectively, and verified the diagnosable image quality with the recommended administered dose of the JSNM guidelines. MATERIALS AND METHODS: Data from 7 pediatric patients who underwent 99mTc-DMSA dynamic renal scans according to the guidelines' recommended doses were collected. Scan frame rate was 1 frame/min, and scan time was up to 8 min. Eight images, which had different acquired time periods from 1 min to 8 min were prepared by adding each frame. Nine nuclear medicine specialists determined 8 images with different acquired times as diagnosable or undiagnosable. A region of interest (ROI) with 50% thresholds was placed on each kidney of every image. Coefficient of variation (CV) was calculated by dividing the standard deviation (σ) by the mean counts (µ) of each ROI (CV = σ/µ × 100). 99mTc-DMSA renal scans (total of 2821 cases) that were performed previously in collaboration with 6 hospitals were collected, and CVs of these images were calculated in all cases. These 2821 cases were separated into 5 groups for every 10 kg weight; i.e., (1) less than 10 kg, (2) 10-19.9 kg, (3) 20-29.9 kg, (4) 30-39.9 kg, and (5) above 40 kg. Regression line of each group was analyzed in relation to the CV and administered dose. The CV at the point of intersection with the recommended dose range from the guideline was determined for each group. This CV value was considered as the estimated CV of the image obtained when the recommended dose of the guideline was used. Thus, if the CV was equal to or less than the estimated CV value, then the diagnostic image quality was deemed satisfactory. RESULTS: Average CV of the lower limit of diagnosable images in 7 cases as determined by 9 nuclear medicine specialists was 19.9%. Estimated CV was 21.2-24.2% in the group weighing < 10 kg (group 1), 19.9-20.6% in the group weighing > 10 kg and < 20 kg (group 2), 19.6% in group weighing > 20 kg and < 30 kg (group 3), 19.4-19.5% in the group weighing > 30 kg and < 40 kg (group 4), and 19.8% in the group weighing > 40 kg (group 5). The estimated CVs from groups 1 and 2 with weight < 20 kg exceeded 19.9%. CONCLUSIONS: Although 99mTc-DMSA renal scan can be carried out using the guidelines' recommended dose with conventional image acquisition time in patients weighing 20 kg or more, those < 20 kg need consideration for a longer image acquisition time to obtain diagnosable images.

Elasticity and viscoelasticity of embolization microspheres.

The present study investigates the mechanical properties of three embolization microspheres (E-ms): tris-acryl gelatin microspheres (TG-ms), acrylamido polyvinyl alcohol microspheres (APVA-ms), and polyphosphazene-coated polymethylmethacrylate microspheres (PP-PMMA-ms). Compression and relaxation tests were performed on monolayers of particles and their Young's moduli and relaxation half times (RHTs) were determined. The elasticity of E-ms was evaluated by applying Hertz theory with the assumptions of incompressibility and a Poisson's ratio of 0.5. The Young's moduli of TG-ms, APVA-ms, and PP-PMMA-ms were 39.6±5.05 kPa, 18.8±4.00 kPa, and 13.6±1.98 kPa, respectively. The RHTs of TG-ms, APVA-ms, and PP-PMMA-ms were 52.3±5.56 s, 59.1±8.16 s, and 31.0±7.01 s, respectively. TG-ms have a high rigidity and deform slightly under a sustained compression since they have a high elasticity. PP-PMMA-ms are soft and deform a lot under sustained compression. They are more viscous than the other two microspheres. APVA-ms have intermediate material properties, having the same low rigidity as PP-PMMA-ms and being more elastic than TG-ms.

Elastic characteristics of microspherical embolic agents used for vascular interventional radiology.

Embolic agents are used in vascular interventional radiology to occlude arteries under pathological conditions. The present study was performed to investigate the material properties of two microspherical embolic agents (MSEAs), tris-acryl gelatin microspheres (TGMS) and superabsorbent polymer microsphere (SAP-MS), using a loading-unloading compression test. The results demonstrated that for both TGMS and SAP-MS, the stress-strain relationship appeared to be linear up to 25% deformation. Therefore, one can reasonably treat TGMS and SAP-MS as linearly elastic materials for this range of deformation and apply the Hertz contact theory for analysis of the Young's modulus. The Young's moduli of TGMS and the SAP-MS obtained by applying Hertz theory under the assumption of a Poisson's ratio of 0.5 were 19.33 +/- 4.97 kPa and 9.64 +/- 2.46 kPa, respectively (mean +/- SD, P<0.001, Mann-Whitney U-test), indicating that TGMS showed higher stiffness than SAP-MS. The effects of a difference in these mechanical characteristics of embolic agents on the performance of interventional radiology were discussed from a viewpoint of their flowing behavior and clinical aspects.

[Gravity sag view of lateral radiography of the knee].

The gravity sag view(GSV)is a lateral radiograph taken in the same position when the posterior sag sign is observed. The purpose of this study was to standardize the radiography technique for GSV by adjusting lateral rotation. To confirm the benchmark and correction angle(CA)for the GSV position, we assessed three-dimensional(3D)CT of the GSV position of the knee using normal volunteers. The benchmark is established at the 3-point of the leg and adjusting the CA of the knee is established by estimating from Rosenberg technique radiography. This helped not only to correct external rotation in the initial radiography but also to correct rotation for repeat radiography. Our method is quantitative and highly reproducible, and it increases the success rate in adjusting lateral radiography of the knee.

Development of a system which automatically acquires optimal discrete-valued attributes by dividing and grouping continuous-valued attributes to assist clinical decision making in radiotherapy.

The purposes of this study were first to develop a system which statistically tests results of radiotherapy and which automatically acquires an optimal discrete-valued attribute by dividing and grouping continuous-valued attributes, and second to find the optimal range of values such as tumor dose by taking account of the conditions and statistics in ROGAD (Radiation Oncology Greater Area Database), a multi-institutional database in Japan. Our ultimate goal is to assist clinical decision making for every patient. In this research, two algorithms for acquiring a boundary value were developed without detecting false boundaries or accidental errors of acquired boundaries. The resolution of detected discrete-valued attributes and speed of convergence were confirmed to be practical. The optimal range of given tumor dose with the best reaction and with the fewest complications is expected to be clarified.

Evaluation of the effect of varying MPEG-2 compression ratios on digital coronary angiographic assessment of stenosis severity.

The purpose of this study is to evaluate the influence of MPEG-2 compression scheme on coronary angiography and to search the highest compression ratio at which no significant effect to accuracy of assessment of stenosis severity occurs. Forty-Four digital cine angiographies were used. Three cardiologists participated in a subjective study in which they read both uncompressed images and compressed images. Furthermore, an objective study was carried out to measure vessel stenosis ratio by using software. The influence of compression was evaluated by kappa statistics in case of subjective study and by both systematic error and random error in case of objective study. Kappa statistics between uncompressed image and compressed image at a ratio of 80:1 was significantly lower than that of other compression ratios such as 40:1. Similar results were obtained in objective evaluation. In this report, the authors provide the baseline for further studies on observer performance for motion images.