TargetScan® 3D Transrectal Ultrasound System – Technical Review
positioning. The transducers within the probe are controlled robotically through the system’s software and touch-screen to allow the user to navigate seamlessly between transverse and longditudinal views. The area of interest is refined using the system software, which performs a bi-planar scan and then generates a 3D prostate image for biopsy and treatment guidance.
Transrectal Biopsy Approach
The software generates standardised biopsy templates of 16–24 sites at three to four levels depending on prostate volume, but these can be modified easily by adding or removing biopsy sites. Once the biopsy template is confirmed, the biopsy can take place, with the software guiding the process (see Figure 2). The biopsy location is defined by dual coordinates, depth from the apex of the prostate in centimetres and the degree of rotation (either clockwise or anticlockwise) from the 12 o’clock position22
(see Figure 3). Biopsies
can be taken under local anaesthesia, conscious sedation or general anaesthesia depending on the extent of the biopsy and clinical practice.
Biopsies are taken with an 18-gauge Nitinol Bendable Biopsy Needle (Envisioneering Medical Systems), which is one of the most novel developments of the system (see Figure 4). The disposable biopsy guide system allows deflection of the needle relative to the probe axis, allowing easy deflection of the needle at angles of 45–50° on repeated sampling without affecting core quality. Biopsy cores can be taken at precise depths and can be recorded for future reference for each patient.
Transperineal Biopsies and Treatment Options Following the same set-up procedure, the TargetScan system also allows for transperineal biopsies by incorporating a standard grid template (see Figure 5). Biopsies are taken through an 18-gauge disposable brachytherapy grid using standard 18-gauge biopsy needles. The touch-screen commands the transducers to automatically image the same point in both planes, which simultaneously identifies a needle position in the transverse grid view and the equivalent longitudinal view without the need to manipulate the probe to obtain different axial images (see Figure 6). The orientation that was carefully established can now be maintained and the prostate does not move. The steriotactic imaging and motionless probe are fundamental features when used in treatment modalities such as low-dose-rate bracytherapy, cryotherapy and photodynamic therapy.
Performance and Outcomes Using the TargetScan System
The TargetScan device has been evaluated in a simulation setting by Andriole et al. on 20 radical prostatectomy specimens. This showed that simulated TargetScan biopsy correctly identified cancer in 16 prostates (80%) and high-grade prostatic intraepithelial neoplasia in two others. It also correctly characterised 88% of prostatic octants in terms of whether they harboured cancer. This technique was reproducible from operator to operator, unlike standard methods, and 85% biopsy core concordance was attained when the TargetScan protocol was simulated in two urology residents.21
Megwalu and co-workers carried out a multicentre, retrospective study from two US centres and evaluated 140 patients who had undergone a TargetScan prostate biopsy during an 18-month period.
EUROPEAN UROLOGICAL REVIEW
Figure 5: Setup of Target Scan for Transperineal Biopsy or Brachytherapy Needle Placement
Figure 4: The Nitinol Bendable Biopsy Needle – An 18-gauge 20cm Biopsy Needle
Source: Envisioneering Medical Inc.
Figure 6: TargetScan touch™ Touch-screen Robotic Commands with Steriotactic Imaging Transverse Template View
The exact point touched in the transverse view is automatically tracked with live imagery in sagital plane and illustrated in the 3D reconstruction
They looked at overall cancer detection rate in all patients and subgroups and assessed the pathological significance of cancer detected (Gleason score of ≥7), positive margins, extracapsular disease or >20% tumour volume in the prostatectomy specimen. They also calculated concordance in Gleason score between the biopsy and prostatectomy specimen. Their results showed an
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