Objective: To analyze the value of combining the virtual monochromatic spectral (VMS) image and adaptive statistical iterative reconstruction V (ASiR-V) in low tube current dual-energy spectral imaging in head CTA, and to explore the optimal VMS and ASiR-V level while reducing the radiation dose. Method: (1) Phantom study: an Anthropomorphic PBU-60 angiographic head phantom was examined on a Revolution CT with spectral imaging mode at two different tube current. Images of different energy levels (at 40, 45, 50, 55, 60, 65 and 70 keV) in A group [the low tube current group (with 280 mA)] were reconstructed with the combination of filtered back projection (FBP), 20%, 40%, 60% and 80% ASiR-V. VMS images at 70 keV in B group [the routine tube current group (with 445 mA)] were reconstructed with FBP only. The standard deviation (SD), signal to noise ratio (SNR) and contrast to noise ratio (CNR) of phantom study were measured and examined by ANOVA variance analysis.(2) Clinical study: to prospectively select 40 patients (randomly divided into A and B groups with 20 patients in each group), the subjective scores of patients were assessed with a 5-point scale system and compared by the Mann-Whitney U test. The radiation dose was recorded and analyzed by t test. Results: (1) Phantom study: there were significant differences in the image noise, CNR of the simulated cerebral vessels at different energy levels of VMS image (P<0.05). VMS images at 40 to 55 keV yielded a higher CNR compared with 70 keV (P<0.05). The SNR and CNR in the low tube current group with ASiR-V 60% and ASiR-V 80% were higher than that of the FBP, ASiR-V 20% and ASiR-V 40% images in the same group (P<0.05). (2) Clinical study: the subjective scores at 55 keV and 60 keV were higher than others (P<0.05). The subject scores of 40,50 and 55 keV were increased as the proportion of ASiR-V increased. (3) The SNR and CNR of the simulated cerebral vessels and subjective scores in of the 55 keV VMS images with ASiR-V 60% and ASiR-V 80% in the low tube current patient group was higher than that of the 70 keV FBP images in the routine tube current group (P<0.05). The radiation dose of A group was lower than B group (t=23.974, P<0.05). Conclusions VMS images in low tube current spectral imaging combined with ASiR-V can significantly reduce radiation dose and ensure image quality in head CTA. The 55 keV VMS images with ASiR-V60% and 80% provide higher image quality.

Natural antisense transcripts (NAT) and alternative polyadenylation (APA) of messenger RNA (mRNA) are important contributors of transcriptome complexity, each playing a critical role in multiple biological processes. However, whether they have crosstalk and function collaboratively is unclear. We discovered that APA enriched in human sense-antisense (S-AS) gene pairs, and finally focused on RNASEH2C-KAT5 S-AS pair for further study. In cis but not in trans over-expression of the antisense KAT5 gene promoted the usage of distal polyA (pA) site in sense gene RNASEH2C, which generated longer 3' untranslated region (3'UTR) and produced less protein, accompanying with slowed cell growth. Mechanistically, elevated Pol II occupancy coupled with SRSF3 could explain the higher usage of distal pA site. Finally, NAT-mediated downregulation of sense gene's protein level in RNASEH2C-KAT5 pair was specific for human rather than mouse, which lacks the distal pA site of RNASEH2C. We provided the first evidence to support that certain gene affected phenotype may not by the protein of its own, but by affecting the expression of its overlapped gene through APA, implying an unexpected view for understanding the link between genotype and phenotype.
Cell Proliferation ; genetics ; Evolution, Molecular ; Gene Expression Regulation ; genetics ; HEK293 Cells ; Humans ; Polyadenylation ; genetics ; RNA, Antisense ; genetics ; RNA, Messenger ; genetics ; Ribonuclease H ; genetics ; Serine-Arginine Splicing Factors ; metabolism ; Transcription, Genetic ; Up-Regulation ; genetics