The main goal of teleoperated needle insertion is accurate tracking of needle in free motion and during insertion.
During the first period, all biopsies were performed by nephrologists with radiologists showing real-time USG image and tracking of needle without using the Ultra-pro needle guide; and during the second period, besides renal biopsies, real-time USG imaging and needle tracking were also performed by nephrologists themselves with needle guide (Ultra-pro II™ Needle guide, Civco, Iowa, USA),.
After the infusion, the needle was kept in place for another 5 min to prevent leakage along the track of the needle.
To examine this possibility, SCCVII tumours grown subcutaneously in C3H mice were injected with a 26 gauge needle containing 0.1 ml of the fluorescent dye Hoechst 33342 to label cells lining the track of the needle.
Intratumour injection transiently increased hypoxia from 18 to 70% in the tumour cells adjacent to the track of the needle.
Hoechst 33342 binds to cells lining the track of the needle, but tirapazamine was expected to diffuse to hypoxic regions within the tumours.
Since the drug concentration was highest in cells along the track of the needle, one could argue that more damage occurred here simply because these cells were exposed to the highest drug dose.
When pimonidazole was injected 90 min or more before intratumour injection of Hoechst, there was no significant difference between the hypoxic fraction of the Hoechst brightest or dimmest cells, that is, the hypoxic fraction was similar for cells lining the track of the needle or distant from the track.
If MRI evaluation was confirmative, further needle tumor biopsy was avoided for fear of needle track seeding.
To the best of our knowledge, there is no evidence to suggest that use of large needles increases the risk of needle track seeding relative to fine needles.
