Relationship between radiation dose reduction and image quality change in photostimulable phosphor luminescence X-ray imaging systems.

OBJECTIVES: The aim of the study was to clarify the change in image quality upon X-ray dose reduction and to re-analyse the possibility of X-ray dose reduction in photostimulable phosphor luminescence (PSPL) X-ray imaging systems. In addition, the study attempted to verify the usefulness of multiobjective frequency processing (MFP) and flexible noise control (FNC) for X-ray dose reduction. METHODS: Three PSPL X-ray imaging systems were used in this study. Modulation transfer function (MTF), noise equivalent number of quanta (NEQ) and detective quantum efficiency (DQE) were evaluated to compare the basic physical performance of each system. Subjective visual evaluation of diagnostic ability for normal anatomical structures was performed. The NEQ, DQE and diagnostic ability were evaluated at base X-ray dose, and 1/3, 1/10 and 1/20 of the base X-ray dose. RESULTS: The MTF of the systems did not differ significantly. The NEQ and DQE did not necessarily depend on the pixel size of the system. The images from all three systems had a higher diagnostic utility compared with conventional film images at the base and 1/3 X-ray doses. The subjective image quality was better at the base X-ray dose than at 1/3 of the base dose in all systems. The MFP and FNC-processed images had a higher diagnostic utility than the images without MFP and FNC. CONCLUSIONS: The use of PSPL imaging systems may allow a reduction in the X-ray dose to one-third of that required for conventional film. It is suggested that MFP and FNC are useful for radiation dose reduction.

Prior treatment with vitamin K(2) significantly improves the efficacy of risedronate.

UNLABELLED: Prior 8-week treatment with menatetrenone, MK-4, followed by 8-week risedronate prevented the shortcomings of individual drugs and significantly increased the strength of ovariectomized ICR mouse femur compared to the ovariectomized (OVX) controls. Neither MK-4 following risedronate nor the concomitant administration may be recommended because they brought the least beneficial effect. INTRODUCTION: The objective of this study was to determine the best combinatory administration of risedronate at 0.25 mg/kg/day (R) with vitamin K(2) at approximately 100 microg MK-4/kg/day (K) to improve strength of osteoporotic mouse bone. METHODS: Thirteen-week-old ICR mice, ovariectomized at 9-week, were treated for 8 weeks with R, K, or R plus K (R/K), and then, either the treatment was withdrawn (WO) or switched to K or R in the case of R and K. After another 8 weeks, the mice were killed, and mechanical tests and analyses of femur properties by peripheral quantitative computed tomography, microfocus X-ray tube computed tomography, and confocal laser Raman microspectroscopy were carried out. RESULTS: The K to R femur turned out superior in parameters tested such as material properties, bone mineral density, BMC, trabecular structure, and geometry of the cortex. The increased cross-sectional moment of inertia, which occurred after K withdrawal, was prevented by risedronate in K to R. In addition to K to R, some properties of R to WO diaphysis and K to WO epiphysis were significantly better than OVX controls. CONCLUSION: Prior treatment with MK-4 followed by risedronate significantly increased femur strength in comparison to the OVX controls.

Influence of prednisolone-induced osteoporosis on bone mass and bone quality of the mandible in rats.

OBJECTIVES: The aim of this study was to clarify the effects of steroid treatment on the mandible. METHODS: We divided 24 male Fisher rats, aged 10 weeks, into 2 groups: a control group (n = 11) and a prednisolone (Pred) treatment group (n = 13). The dose for the Pred group was 40 mg kg(-1) and was administered orally three times per week for 8 weeks. At the end of the experiment, we measured bone mass, bone strength and trabecular structure of the mandible and femur. RESULTS: Pred treatment decreased cortical bone mineral content (BMC), cortical thickness, stress/strain index and tissue volume of the mandible. However, there were no marked changes in trabecular structure parameters. A strong correlation was seen between mandibular and femoral cortical BMC (r = 0.71). CONCLUSIONS: These findings suggest that steroid treatment decreases the cortical BMC, bone area and bone strength of the mandible.