[Evaluation of AEC Consistency in Digital X-ray Imaging Systems].

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 (KAEC) 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 KAEC 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 KAEC 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.

Pharmacokinetic functions of human induced pluripotent stem cell-derived small intestinal epithelial cells.

To develop a novel intestinal drug absorption system using intestinal epithelial cells derived from human induced pluripotent stem (iPS) cells, the cells must possess sufficient pharmacokinetic functions. However, the CYP3A4/5 activities of human iPS cell-derived small intestinal epithelial cells prepared using conventional differentiation methods is low. Further, studies of the CYP3A4/5 activities of human iPS-derived and primary small intestinal cells are not available. To fill this gap in our knowledge, here we used forskolin to develop a new differentiation protocol that activates adenosine monophosphate signaling. mRNA expressions of human iPS cell-derived small intestinal epithelial cells, such as small intestine markers, drug-metabolizing enzymes, and drug transporters, were comparable to or greater than those of the adult small intestine. The activities of CYP3A4/5 in the differentiated cells were equal to those of human primary small intestinal cells. The differentiated cells had P-glycoprotein and PEPT1 activities equivalent to those of Caco-2 cells. Differentiated cells were superior to Caco-2 cells for predicting the membrane permeability of drugs that were absorbed through a paracellular pathway and via drug transporters. In summary, here we produced human iPS cell-derived small intestinal epithelial cells with CYP3A4/5 activities equivalent to those of human primary small intestinal cells.

Bioresorbable Bone Graft Composed of an RGD-Enriched Recombinant Human Collagen Polypeptide Induced Neovascularization and Regeneration of Mature Bone Tissue.

Bone graft materials provide a scaffold for migrating cells for bone regeneration. One of the major challenges is to support adequate neovascularization in the graft materials and bone tissue. Vascular endothelial cells have been shown to recognize the integrin-binding Arg-Gly-Asp (RGD) sequence in natural extracellular matrix (ECM) molecules. Here, we report a bone graft material composed of an RGD-enriched recombinant polypeptide based on human type I collagen alpha 1 chain (RCPhC1) and propose a category of bone graft materials called the recombinant bone matrix. RCPhC1 demonstrated significantly increased human umbilical vein endothelial cell attachment in vitro and was further processed through freeze casting and heat crosslinking processes to generate porous granular bone graft, in which RGD sequences remained canonical. When grafted in the rat model, RCPhC1 bone graft demonstrated a uniquely increased presence of CD34+ endothelial cells within the graft material. Bone tissue was found directly in contact with the pore structure of RCPhC1 bone graft, resulting in the regeneration of large bone tissue. By contrast, the combined demineralized and decellularized bone allograft containing bone collagen in the ECM did not show vascular formation within the graft material. When applied to canine tooth extraction socket, RCPhC1 bone graft rapidly induced highly vascularized regenerating tissues, which became a mature bone with the bone marrow tissue. These results indicate that RCPhC1 bone graft is a promising material and generated highly active bone tissues, which rapidly matured.

[Effect of Interspaces of Anti-scatter Grid on the Image Improvement Factor].

The standard general purpose of anti-scatter girds: JIS Z 4910: 2015 (IEC 60627: 2013) has been revised, with the new addition of an image improvement factor (Q) to the physical characteristic. Using aluminum (Al) and fiber-interspaced anti-scatter grids; we studied the meaning of Q by calculating each of the physical characteristics and assessing the image. The experimental method was based on JIS Z 4910: 2015. The two anti-scatter grids had a grid ratio of 12: 1 and a strip frequency of 40 cm-1. Assessment items consisted of grid exposure factor (B), grid selectivity (Σ), contrast improvement ratio (K), and Q. In addition, the contrast to noise ratio (CNR) and contrast-detail curve (CD-curve) were determined from the contrast-detail phantom image, and the inverse image quality figure (IQF) was then calculated from the CD-curve. Compared to the Al-interspaced anti-scatter grid, the fiber-interspaced anti-scatter grid had B at 0.87, Σ at 0.95, K at 0.99, and Q at 1.14. In the assessment of the contrast-detail phantom image, the fiber-interspaced anti-scatter grid had an IQF of 1.02 times and a CNR of approximately 1.24 times when compared to the Al interspaced anti-scatter grid. The fiber-interspaced anti-scatter grid was superior with respect to the B and Q of the physical characteristics and to the CNR of image quality assessment.

[Development of a simple measurement system for routine management of X-ray equipment].

Routine management of X-ray equipment is critically important, but due to the high cost of commercial management systems it is currently not practical to deploy this valuable instrumentation at every clinical facility. This led us to develop a simple measurement system for routine management purposes that can be deployed for around ¥100 thousand in materials. The system consists of an X-ray output meter, a clamp-type X-ray tube current meter (clamp meter), and a digital oscilloscope. Compared to a standard fluorescence meter, the X-ray output meter provides equivalent accuracy and reproducibility of X-ray tube voltage, X-ray tube current, and irradiation time changes, while also displaying the X-ray output time. The clamp meter must be periodically calibrated, however provides equivalent accuracy and reproducibility to a direct contact meter, while also displaying net X-ray tube current and loading time. Finally, the oscilloscope is able to estimate the waveform of X-ray tube voltage by monitoring each waveform, thus making it an extremely useful instrument for day-to-day management of X-ray equipment installed at clinical facilities.

[Characteristics of a new non-invasive x-ray output analyzer].

The X-ray systems study group used the Victoreen NERO mAx model 8000, a new non-invasive X-ray output analyzer, to measure the tube voltage, tube voltage waveform, tube current, and irradiation time for conditions corresponding to general radiography and mammography. The measurement results were then compared with those obtained using a conventional invasive measuring instrument. The peak values of the tube voltage measured by the NERO mAx and the invasive measuring instrument were compared. The NERO mAx had a good measurement error range of -1.2 to +0.9 kV. For tube current measurement by the NERO mAx, the maximum error for general radiography conditions was +11 mA and that for mammography conditions was +6 mA. For irradiation time measurement, the value for general radiography conditions was slightly greater and the value for mammography conditions was slightly less than the corresponding values obtained by the invasive measuring instrument. If radiation quality is changed during measurement of the characteristics, measurement values change. Since the NERO mAx incorporates two types of X-ray detectors, it shows good measurement reproducibility. The NERO mAx has been shown to have suitable characteristics for use as a measuring instrument for constancy tests. In the future, constancy tests should be used to quantitatively control the factors determining clinical image quality.