Between June,
16th 2010 and January,
the 22nd 2013,
we experienced the use of a novel optical-guidance computer-assisted system: ActiSight™/CT-guide™ System (Fig.
1).
On a series of 29 patients (10 female,
19 male; mean age: 59.9 ± 13.9 years; range: 25.6-80.9 years) we performed 36 CT-guided interventional procedures: 19 biopsies and 17 radiofrequency ablation procedures (RFA): 23 patients underwent a single procedure,
1 patient had 3 lesions treated with RFA,
3 patients had 2 lesions treated with RFA,
1 patient had 2 biopsies and 1 patient underwent biopsy,
then RFA of the same lesion.
Totally,
we targeted 35 lesions (mean diameter: 31.2 ± 22.2 mm; range: 6-90 mm): 29 lung lesions [16 lesions in right lung,
13 lesions in left lung; 18 lesions in upper lobe,
4 lesions in middle lobe or lingula,
7 lesions in inferior lobe; 14 peripheral lesions (<10 mm from pleura) and 15 parenchimal lesions (≥ 10 mm from pleura)]; 2 retroperitoneal lesions; 2 mediastinal lesions; 1 adrenal gland lesion,
1 iliac muscle lesion (Fig.
2).
CT-Guide™ system is a stereotactic accessory designed to assist the guidance of an interventional instrument for CT-guided procedures.
CT-Guide™ represents a technically updated version of ActiSight™ guidance system,
that we used from June 2010 to December 2012: some substantial improvements have been made.
Technical features of CT-Guide™ include (Fig.
1):
- a console with a computer supporting CT-Guide™ navigation software,
connected to RIS-PACS.
The software is able to import CT images,
convert them into DICOM format and allows the selection of an entry point to target and plan the needle path; an additional monitor is used as an interactive interface to guide the radiologist during navigation;
- a sterile,
single use miniature video-camera (ActiSensor™) on a plastic adaptor,
designed to fit most commercially available interventional instuments,
such as biopsy needles (14 to 20 Gauge needles supported) and ablation probes;
- a sterile,
single use sticker (ActiSticker™) to be applied on patient’s skin: the sticker’s top layer consists of a multi-colored printed pattern (optical reference markers).
Below each of the eight colored reference markers is a matching radio-opaque marker (CT reference markers).
The sticker now includes multiple available insertion ports (Left,
Medial and Right Entry Holes).
ActiSight system requires a dedicated CT scan acquisition protocol to be installed on the CT-suite console (spiral acquisition; slice thickness: 1.25 mm; gap: 1 mm; 120 kV; 110 mA).
The first step of the targeting procedure is the selection of an entry point to the lesion.
Entry point selection requires a CT scan,
wich can can be performed with a radiopaque grid located on the patient’s skin over the estimated area of the lesion.
A preliminary CT scan of the designated area is performed (Plan Scan),
then CT images are sent to CT-Guide™ (Fig.
3).
The target lesion and entry point are selected upon DICOM images,
then the software elaborates the CT slice location of the entry point,
the path length and the scan range between target and ActiSticker (Plan Application),
in order to scan only the area necessary for the current stage of the targeting procedure and reduce the patient’s exposure to irradiation (Fig.
4).
By the use of the CT gantry laser light,
skin is marked.
The area of intervention is shaved and disinfected (2% iodopovidone solution).
ActiSticker must be firmly attached to the patient’s body,
with the orthogonal black lines aligned to the skin marked lines.
A new CT scan is performed and images are sent to the software (Register Application): after verifying patient details,
target lesion and Entry Hole (Left,
Medial or Right) must be selected,
then the software produces a volume rendering (VR) image of the skin surface with ActiSticker™ (Fig.
5).
Upon the VR image of the sticker,
the Reference Points must be marked,
then the system is ready to plan the needle pathway to target lesion (Fig.
6).
Through the selected Entry Point Hole local anesthesia (lidocaine 2%) is administered.
The miniature video-camera is then connected to the computer (Navigate Application) and the length of the needle is calibrated.
Once calibration is complete and the navigation starts,
the software displays a blue/yellow circle icon indicating target position,
and crosshairs (“+”) indicating projected tip position overlaid on a video image of ActiSticker.
In addition,
a simulated needle path is displayed on 2 orthogonal CT images aligned to the needle path.
By adjusting the angle of the needle,
the crosshairs must be placed directly over the target icon (Fig.
7).
During the needle insertion,
the projection of the needle tip in the plane of the target is constantly updated along with the distance of the needle tip from the target and the radial distance to target (Fig.
8).
Additional CT scans may be taken as necessary during the procedure to verify needle position relative to the target.
The physician is informed graphically and numerically when the needle has reached the target.
A CT scan is then performed to confirm the needle has reached the target.
Since both ActiSight™ and CT-Guide™ have no breath correction for lung interventional procedures,
at the beginning of our experience with Acti-Sight™,
we tried performing targeting procedures for lung lesions with the patients breathing free or in some case in expiratory or inspiratory apnoea.
Recently,
we have established to standardize the targeting procedure for lung lesions,
teaching the patient to hold breath in expiration during targeting or intermediate CT scans and during navigation to target phase.