Percutaneous radiofrequency ablation of virtual tumours in canine kidney using Global Positioning System-like...

What's known on the subject? And what does the study add? We have previously shown that percutaneous radiofrequency ablation guided by image-fusion technology allows for precise needle placement with real time ultrasound superimposed with pre-loaded imaging, removing the need for real-time CT or MR guidance. Emerging technology also allows real-time tracking of a treatment needle within an organ in a virtually created 3D format. To our knowledge, this is the first study utilising a sophisticated ultrasound-based navigation system that uses both image-fusion and real-time probe-tracking technologies for in-vivo renal ablative intervention.

• To evaluate the feasibility, accuracy and efficacy of ultrasonography (US)-guided percutaneous radiofrequency ablation (RFA) in the canine kidney model using novel Global Positioning System-like probe tracking technology. • Virtual tumours in the canine kidney were ablated in vivo by percutaneous RFA guided exclusively by two-dimensional (2D) US and a virtual navigation system.

• Gold fiducial markers were inserted into renal parenchyma to serve as centres of virtual tumours. • After capturing 2D US images, navigation software created a three-dimensional planning model of the kidney, and superimposed it onto the live US image. • Percutaneous RFA was guided by multiplanar navigation, showing real-time probe positions within the superimposed images, to treat each virtual tumour with a single treatment. • Navigator software predicted the percentage of tumour treated; treated kidney specimens were examined to evaluate projection and targeting accuracy.

• In total, 32 virtual tumours (median diameter 16 mm, range 10-24 mm) were treated in 16 canine kidneys. • Median (range) error between 'fiducial tumour centre' and 'treated area centre' was 1.8 (0-25) mm. • Targeting accuracy improved with experience: median (range) error decreased from 6.3 (2-25) mm in an initial 12 tumours to 1.3 (0-9.0) mm in the last 20 tumours (P= 0.008). • The percentage (range) of tumour actually treated improved significantly from the initial series at 23% (0-100%) to 100% (51-100%) (P < 0.001). • Overall, navigator-reported and pathologically confirmed treatment percentages were correlated significantly (r= 0.5; P= 0.006).

• Percutaneous renal RFA guided exclusively by real-time 2D US with multiplanar Global Positioning System-like probe tracking is feasible and accurate. • Near-future technologies, including elastic fusion overlay and anticipation of soft-tissue deformation, will further augment this guidance system.