An additional tilted-scan-based CT metal-artifact-reduction method for radiation therapy planning.

PURPOSE: As computed tomography (CT) imaging is the most commonly used modality for treatment planning in radiation therapy, metal artifacts in the planning CT images may complicate the target delineation and reduce the dose calculation accuracy. Although current CT scanners do provide certain correction steps, it is a common understanding that there is not a universal solution yet to the metal artifact reduction (MAR) in general. Particularly noting the importance of MAR for radiation treatment planning, we propose a novel MAR method in this work that recruits an additional tilted CT scan and synthesizes nearly metal-artifact-free CT images. METHODS: The proposed method is based on the facts that the most pronounced metal artifacts in CT images show up along the x-ray beam direction traversing multiple metallic objects and that a tilted CT scan can provide complementary information free of such metal artifacts in the earlier scan. Although the tilted CT scan would contain its own metal artifacts in the images, the artifacts may manifest in a different fashion leaving a chance to concatenate the two CT images with the metal artifacts much suppressed. We developed an image processing technique that uses the structural similarity (SSIM) for suppressing the metal artifacts. On top of the additional scan, we proposed to use an existing MAR method for each scan if necessary to further suppress the metal artifacts. RESULTS: The proposed method was validated by a simulation study using the pelvic region of an XCAT numerical phantom and also by an experimental study using the head part of the Rando phantom. The proposed method was found to effectively reduce the metal artifacts. Quantitative analyses revealed that the proposed method reduced the mean absolute percentages of the error by up to 86% and 89% in the simulation and experimental studies, respectively. CONCLUSIONS: It was confirmed that the proposed method, using complementary information acquired from an additional tilted CT scan, can provide nearly metal-artifact-free images for the treatment planning.

Conversion Total Knee Arthroplasty after Failed High Tibial Osteotomy.

Clinical results of high tibial osteotomy (HTO) deteriorate over time despite the initial satisfactory results. Several knees may require a conversion to total knee arthroplasty (TKA) because of failure such as the progression of degenerative osteoarthritis and the loss of the correction angle. It is important to know the long-term survival rate and common reason of failure in HTO to inform patients of postoperative expectations before surgery and to prevent surgical errors during surgery. In addition, it has been reported that clinical and radiological results, revision rate, and complication rate were poorer than those in patients without a previous HTO. There are few review articles that describe why conversion TKA after HTO is surgically difficult and the results are poor. Surgeons have to avoid the various complications and surgical errors in this specific situation. We would like to present the considering factors and technical difficulties during conversion TKA after HTO with a review of the literature. We could conclude through the review that the correction of deformity, lower amount of tibial bone resection, and sufficient polyethylene insert thickness, restoration of the joint line height, and adequate ligament balancing can be helpful in overcoming the technical challenges encountered during TKA following HTO.

Dehydroglyasperin C isolated from licorice caused Nrf2-mediated induction of detoxifying enzymes.

Our preliminary experiment demonstrated that a n-hexane/EtOH (9:1, volume) extract of Glycyrrhiza uralensis (licorice) caused a significant induction of NAD(P)H:oxidoquinone reductase (NQO1), one of the well-known phase 2 detoxifying enzymes. We isolated dehydroglyasperin C (DGC) as a potent phase 2 enzyme inducer from licorice. DGC induced NQO1 both in wild-type murine hepatoma Hepa1c1c7 and ARNT-lacking BPRc1 cells, indicating that the compound is a monofunctional inducer. The compound induced not only NQO1 but also some other phase 2 detoxifying/antioxidant enzymes, such as glutathione S-transferase, gamma-glutamylcysteine synthase, glutathione reductase, and heme oxygenase 1. Similar to most monofunctional inducers, DGC caused the accumulation of Nrf2 in the nucleus in dose- and time-dependent manners and thereby activated expression of phase 2 detoxifying enzymes. It also resulted in a dose-dependent increase in the luciferase activity in the reporter assay, in which HepG2-C8 cells transfected with antioxidant response element (ARE)-luciferase construct were used, suggesting that the induction of phase 2 detoxifying and antioxidant enzymes could be achieved through the interaction of Nrf2 with the ARE sequence in the promoter region of their genes.

Comparison of the effects of NADH- and NADPH-perturbation stresses on the growth of Escherichia coli.

To better understand how the reducing power of either NADH or NADPH affects cell growth, Escherichia coli strains expressing either NADH-dependent or NADPH-dependent azoreductase (EC 1.6.5.2), which mediates the reduction of an azo dye, were cultured in glucose minimal medium in the presence of 200 muM methyl red. Growth rates in NADH-perturbed, NADPH-perturbed, and control cells were 0.05, 0.12, and 0.13 h(-1), respectively. In addition, glucose consumption in NADH-perturbed cells was 10.8 g glucose/g cell, while that of control and NADPH-perturbed cells was very similar (3.6 vs 3.8 g glucose/g cell) during the perturbation phase. Therefore, NADH perturbation had a larger effect than NADPH on cellular growth.