Use of novel photon - counting detector CT for diagnosis of bowel infarction.

A 75 year old male with a history of thoraco-abdominal surgery presented with acute onset epigastric pain. CT of the abdomen and pelvis with contrast performed on a novel photon-counting detector CT demonstrated dilated loops of small bowel herniating into the thoracic cavity through a defect in the left hemidiaphragm. On conventional CT reconstructions, the bowel wall demonstrated a thin rim of hyper-density which could have been interpreted as normal mucosal enhancement in viable bowel. However, spectral-imaging data including the iodine map revealed a complete lack of enhancement within the herniated loops of bowel compatible with infarction. With the added diagnostic information, the patient was taken rapidly to surgery for small bowel resection, with good outcome.

Optimization of window settings for standard and advanced virtual monoenergetic imaging in abdominal dual-energy CT angiography.

OBJECTIVES: To determine the optimal window setting for displaying virtual monoenergetic reconstructions of third generation dual-source, dual-energy CT (DECT) angiography of the abdomen. METHODS: Forty-five patients were evaluated with DECT angiography (90/150 kV, 180/90 ref. mAs). Three datasets were reconstructed: standard linear blending (M_0.6), 70 keV traditional virtual monoenergetic (M70), and 40 keV advanced noise-optimized virtual monoenergetic (M40+). The best window setting (width and level, W/L) was assessed by two blinded observers and was correlated with aortic attenuation to obtain the Optimized W/L setting (O-W/L). Subjective image quality was assessed, and vessel diameters were measured to determine any possible influences between different W/L settings. Repeated measures of variance were used to evaluate comparison of W/L values, image quality, and vessel sizing between M_0.6, M70, and M40+. RESULTS: The Best W/L (B-W/L) for M70 and M40+ was 880/280 and 1410/450, respectively. Results from regression analysis inferred an O-W/L of 850/270 for M70 and 1350/430 for M40+. Significant differences for W and L were found between the Best and the Optimized W/L for M40+, and between M70 and M40+ for both the Best and Optimized W/L. No significant differences for vessel measurements were found using the O-W/L for M40+ compared to the standard M_0.6 (p ≥ 0.16), and significant differences were observed when using the B-W/L with M40+ compared to M_0.6 (p ≤ 0.04). CONCLUSION: In order to optimize virtual monoenergetic imaging with both traditional M70 and advanced M40+, adjusting the W/L settings is necessary. Our results suggest a W/L setting of 850/270 for M70 and 1350/430 for M40+.

Microgravity Induction of TRAIL Expression in Preosteoclast Cells Enhances Osteoclast Differentiation.

Evidence indicates that astronauts experience significant bone loss in space. We previously showed that simulated microgravity (µXg) using the NASA developed rotary cell culture system (RCCS) enhanced bone resorbing osteoclast (OCL) differentiation. However, the mechanism by which µXg increases OCL formation is unclear. RANK/RANKL signaling pathway is critical for OCL differentiation. Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) has been shown to increase osteoclastogenesis. We hypothesize that TRAIL may play an important role in µXg enhanced OCL differentiation. In this study, we identified by RT profiler PCR array screening that µXg induces high levels of TRAIL expression in murine preosteoclast cells in the absence of RANKL stimulation compared to ground based (Xg) cultures. We further identified that µXg elevated the adaptor protein TRAF-6 and fusion genes OC-STAMP and DC-STAMP expression in preosteoclast cells. Interestingly, neutralizing antibody against TRAIL significantly reduced µXg induced OCL formation. We further identified that over-expression of pTRAIL in RAW 264.7 cells enhanced OCL differentiation. These results indicate that TRAIL signaling plays an important role in the µXg increased OCL differentiation. Therefore, inhibition of TRAIL expression could be an effective countermeasure for µXg induced bone loss.