Coaxial cutting needle biopsies: how important is it to rotate the cutting needle between passes?

To use an in-vitro model to measure the effect of turning the notch of the cutting needle between passes on the mass of core biopsy material obtained from a typical coaxial biopsy system when multiple passes are performed.

A coaxial guide needle was placed within tissue-equivalent agar cylinders and a cutting biopsy needle was used to take core biopsies. Two, three, or four sequential biopsies were performed on the same cylinder with the notch of the cutting needle either inserted facing in the same direction (no rotation) or placed in a sequence of different directions (rotation). The mass of the tissue core obtained at each biopsy pass was measured. A post hoc telephone questionnaire of radiologists across Australia was also undertaken to analyse current practice in the context of these results.

There were statistically significant increases in the mass of tissue obtained using rotation compared with no rotation. Using rotation, the total mass of tissue obtained from three passes was increased by 32.8% (95% CI 23.9-41.7%) and from four passes was increased by 45% (95% CI 37.2-52.9%). The mass of the second pass cores was statistically significantly greater (p<0.001). Fifty-nine percent of Australian radiologists surveyed do not currently change the rotation of the biopsy needle between passes.

This in-vitro model confirms that the notch of the cutting needle should be placed into different directions at each pass whenever a coaxial cutting biopsy system is being used to maximize the mass of tissue obtained.