English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Flow back along a needle track (backflow) can be a problem during direct infusion, e.g. convection-enhanced delivery (CED), of drugs into soft tissues such as brain. In this study, the effect of needle insertion speed on local tissue injury and backflow was evaluated  in vivo  in the rat brain. Needles were introduced at three insertion speeds (0.2, 2, and 10 mm/s) followed by CED of Evans blue albumin (EBA) tracer. Holes left in tissue slices were used to reconstruct penetration damage. These measurements were also input into a hyperelastic model to estimate radial stress at the needle-tissue interface (pre-stress) before infusion. Fast insertion speeds were found to produce more tissue bleeding and disruption; average hole area at 10 mm/s was 1.87-fold the area at 0.2 mm/s. Hole measurements also differed at two fixation time points after needle retraction, 10 and 25 min, indicating that pre-stresses are influenced by time-dependent tissue swelling. Calculated pre-stresses were compressive (0 to 485 Pa) and varied along the length of the needle with smaller average values within white matter (116 Pa) than gray matter (301 Pa) regions. Average pre-stress at 0.2 mm/s (351.7 Pa) was calculated to be 1.46-fold the value at 10 mm/s. For CED backflow experiments (0.5, 1, and 2 µL/min), measured EBA backflow increased as much as 2.46-fold between 10 and 0.2 mm/s insertion speeds. Thus, insertion rate-dependent damage and changes in pre-stress were found to directly contribute to the extent of backflow, with slower insertion resulting in less damage and improved targeting.

Effect of Needle Insertion Speed on Tissue Injury, Stress, and Backflow Distribution for Convection-Enhanced Delivery in the Rat Brain