Hindawi

Radiology Research and Practice

Volume 2017, Article ID 3151694, 7 pages
https://doi.org/10.1155/2017/3151694

Research Article
Application of Real-Time 3D Navigation System in
CT-Guided Percutaneous Interventional Procedures:
A Feasibility Study

Priya Bhattacharji1,2 and William Moore1,2

1
Department of Radiology, State University of New York at Stony Brook University Hospital, HSC Level IV, Room 120,
Stony Brook, NY 11794, USA
2
Department of Radiology, New York University Medical Center, 650 First Avenue, Third Floor, Room 355, New York, NY 10016, USA

Correspondence should be addressed to William Moore; william.moore@nyumc.org

Received 13 June 2017; Revised 28 August 2017; Accepted 17 September 2017; Published 18 October 2017

Academic Editor: Andreas H. Mahnken

Copyright © 2017 Priya Bhattacharji and William Moore. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.

Introduction. To evaluate the accuracy of a quantitative 3D navigation system for CT-guided interventional procedures in a two-
part study. Materials and Methods. Twenty-two procedures were performed in abdominal and thoracic phantoms. Accuracies of
the 3D anatomy map registration and navigation were evaluated. Time used for the navigated procedures was recorded. In the
IRB approved clinical evaluation, 21 patients scheduled for CT-guided thoracic and hepatic biopsy and ablations were recruited.
CT-guided procedures were performed without following the 3D navigation display. Accuracy of navigation as well as workflow
fitness of the system was evaluated. Results. In phantoms, the average 3D anatomy map registration error was 1.79 mm. The average
navigated needle placement accuracy for one-pass and two-pass procedures, respectively, was 2.0 ± 0.7 mm and 2.8 ± 1.1 mm in the
liver and 2.7±1.7 mm and 3.0±1.4 mm in the lung. The average accuracy of the 3D navigation system in human subjects was 4.6 mm
± 3.1 for all procedures. The system fits the existing workflow of CT-guided interventions with minimum impact. Conclusion. A 3D
navigation system can be performed along the existing workflow and has the potential to navigate precision needle placement in
CT-guided interventional procedures.

1. Introduction guided interventions because of motion and deformation.

The modality chosen for these procedures depends on the
Precision placement of intervention instruments is critical for target of interest, its size, accessibility, and visibility all of
all procedures especially in percutaneous procedures such as which play a crucial role in increasing the complexity of
biopsies and ablations in order to achieve diagnostic accuracy diagnostic and therapeutic interventions.
as well as accurate tumor targeting. Additionally, with the Computed tomography (CT) and ultrasound (US) are the
increasing importance of immune-histochemical markers most commonly used modalities for interventional proce-
and molecular markers in cancer patients, the need for larger dures in the liver and lung. US is of limited utility in the
and more accurate biopsy has become paramount [1, 2]. More lung and can potentially be limited in the abdominal soft
recently, the use of minimally invasive treatments that require tissues specifically in the ability to detect small lesions, less
highly precise imaging guidance such as radiofrequency abla- than 1 cm in diameter [5]. Despite having high accuracy rates
tion (RFA), cryoablation, and microwave ablation (MWA) [6–8], CT is limited by the lack of real-time imaging which is
has become common place in cancer management because often necessary for procedural guidance. CT fluoroscopy can
of their effectiveness and safety [3, 4]. result in improvement in needle/probe positioning at the cost
Lesions in soft tissue organs, such as the liver and lung, of additional radiation exposure to the patient and operator.
present a unique challenge for radiologists to target in image Additionally, CT fluoroscopy is still a subject of debate for
2 Radiology Research and Practice

(a) (b)

(c) (d)

Figure 1: Sample of preprocedural CTs: (a) phantom abdominal scans; (b) phantom thoracic scans; (c) patient abdominal scan; (d) patient
thoracic scan.

small lesions and lesions near vital anatomies [9, 10]. Cone the accuracy of this navigational system. To our knowledge,
Beam Computed Tomography (CBCT) allows for real-time this is the only EMTNS that can generate a 3D fully quantified
visualization with CT imaging. Additionally, CBCT uses an anatomic map of the target and its surrounding vessels and
open gantry and provides flexibility to the operator with structures from one preprocedural CT or MRI scan and plan
needle positioning allowing for high accuracy rates even in a trajectory to the target lesion clear of vital anatomies. This
technically challenging conditions [11]. However, currently, small pilot study aims to assess the feasibility and accuracy of
this technique can be labor intensive and slow compared to a 3D quantitative computer aided navigation system, for
traditional CT scanners. thoracic and abdominal biopsies as well as interventional
Electromagnetic tracking systems (EMTS) use electro- oncologic procedures.
magnetic navigation (EMN), an established method to
improve accuracy using 3D spatial navigation information
[12, 13]. These systems have the ability to fuse several 2. Materials and Methods
imaging modalities (CT, PT, MRI, or US), thus combining the
benefits of each of these modalities to optimize visualization 2.1. 3D Navigation System. The quantitative 3D navigation
during interventional procedures and providing the ability system (IQQA-Guide, EDDA Technology, Inc.) contains an
to approach lesions that were not well visualized on con- electromagnetic tracking software package and tracks instru-
ventional imaging [14–18]. Given the increasing central role ment position and orientation in a fully quantified 3D pa-
that imaging plays in the early detection and diagnosis of a tient-specific anatomy map generated from one preproce-
variety of malignancies including lung cancer, colon cancer, dural CT (Figures 1(a)–1(d)) or MRI and its spatial relation
and renal cell cancer, [19–21] these systems are emerging to target. All procedures were performed with a Siemens
synergistically to allow for potential early detection initiatives Somatom (Erlangen, Germany) 16-detector CT scanner. CT
and to provide support for precisely targeted lesions for images were taken with 2 mm thickness with a pitch of 1 : 1.1,
diagnostic procedures and minimally invasive treatments. 16 × 0.5 mm detector configuration, at 120 peak kilovoltage
We connected this investigational EMNTS system to (kVp) and a variable milliamperage using an effective mAs of
patients who were having CT-guided biopsies to determine 100 mA.
Radiology Research and Practice 3

89.7 mm

93.3 mm

(a) (b)

68.3 mm
39.3 mm
21.3 mm

37.8 mm

EDDA Tech. EDDA Tech.

(c) (d)

Figure 2: Fully quantified 3D anatomy generated from the CT scans with interactively planned and real-time depth. (a) Abdominal scan in
phantom (b) Thoracic scan in phantom (c-d) 3D anatomic map in patients.

The navigation system has an extendable arm with an ducts, skin, bone, etc.) were then generated using the
electromagnetic field generator attached. The generator, with navigation system (Figures 2(a)–2(d)), [22]. Accuracy of
a working distance of over 40 cm, was positioned facing the 3D anatomic map registration (i.e., image registration
the intervention area, (patient). CIVCO (Coralville, Iowa) between the initial CT from which the 3D anatomic map
eTRAX coaxial needle system (for liver biopsies) and CIVCO was generated and the final needle tip position based on the
general purpose sensor together with virtuTRAX navigator coregistration of anatomic landmarks such as the carina or
(for lung biopsies and ablations) were used to acquire major vascular structures and fiducial markers placed on the
position and orientation tracking information of the needle. skin) was determined using final needle tip position on the
Tracked fiducial markers were placed on the patient. The final conformational CT compared to the expected location
electromagnetic- (EM-) tracked fiducial markers allow the of the needle tip based on the 3D model. Initial CT images
“patient-space” to be registered with the 3D patient-specific were performed at the time of the procedure not prior to the
anatomic map (“image-space”). This registration together procedure.
with the EM tracking information from the sensor in the All procedures with this system were performed by a
eTRAX/virtuTRAX allows the position and orientation of the radiologist with more than 15 years of experience in image
instrument relative to the 3D anatomic map to be computed guided intervention. The radiologist used either a one-pass
and displayed. The patient’s registration can be updated with or a two-pass method of accessing the specific lesion. In
additional intraprocedural scans as needed. the one-pass needle placement, the physician inserted the
needle directly to target using the quantitative 3D navigation
2.2. Phantom Experiment. An abdominal phantom and a system as a guide for appropriate needle positioning. A final
thoracic phantom (CIRS Inc. Norfolk, VA, USA) each with conformational CT was performed, to determine final needle
6 small lesions were used in this study. Preprocedural CT positioning; however, no additional imaging was performed
images were sent over the hospital networked to a 3D quan- during the needle placement to assist with the guidance.
titative navigation system (IQQA-Guide, EDDA technology, For the two-pass needle placement method, the radiologist
Inc., Princeton, NJ). Quantified 3D anatomic renderings of inserted the needle part of the way to the target using the
the liver and the lung inclusive of anatomic features (lesions, navigation system as guidance. Then, an intraprocedural
4 Radiology Research and Practice

(a) (b)

Figure 3: Sample of final confirmation CTs showing the actual needle positions and needle positions projected by the navigation system
(dashed lines). (a) Patient abdominal scan; (b) patient thoracic scan.

CT scan was performed, confirming the location of the tip computer generated 3D map anticipated needle tip position.
of the needle. The intraprocedural CT scan was used to The interventional radiologist specifically looked at the actual
update the “patient-space” with “image-space” alignment. needle path confirmed by CT as part of the standard of care.
The radiologist then inserted the needle to the target using the The radiologist was not allowed to see the 3D navigational
3D navigational system and a final conformational CT scan system. With each of the CT scans taken during the proce-
was performed. dure, the navigation system registration was updated allowing
for continued refinement of needle position.
2.3. Feasibility in Patients. From January 2014 to August 2014,
patients with preprocedural CT imaging who were scheduled 2.5. Accuracy and Workflow Fitness. Accuracy of the system
for a CT-guided biopsy or ablation of the liver or lung were was defined as the distance between the final needle tip
recruited for participation in this IRB approved prospective position on the conformational CT scan and the antici-
pilot study. A total of 21 patients were included in this part pated needle tip position predicted by the navigation system
of the study. During this part of the study the interventional (Figures 3(a) and 3(b)). Workflow of the system was also
radiologist did not use the navigational system. The system evaluated by the interventional radiologist. Setup time for the
was used passively; that is, the guidance system was not system and each of the additional steps necessary to use the
shown to the radiologist during the procedure, and the navigation system were noted and the time to complete each
radiologist was required to perform the procedure as he step was recorded.
normally would. The navigational system collected all data
2.6. Statistical Analysis. All statistical analysis was performed
and was reviewed for accuracy after the procedure was
using Graphpad Prism Version 6.0f (La Jolla, CA). All data
complete.
was analyzed using two-tailed Student’s 𝑡-test. Statistical
significance was set at 𝑝 < 0.05.
2.4. Biopsy Procedure. The patient or phantom was posi-
tioned on the CT table. All biopsy patients received sedation 3. Results
specifically titrated to moderate sedation using intravenous
versed and fentanyl. Both ablation patients received general 3.1. Evaluation in Phantoms. In the phantom experiment,
anesthesia. Five EM-tracked fiducial marks were placed on a total of 6 thoracic lesions and 6 liver lesions were
the phantom or patient in order to create the “patient- biopsied with the guidance of the navigation system. The
space.” In patients, the fiducial markers were placed on average lesion diameter was 13.2 ± 7.0 mm (SD) (range
the patients’ skin outside of the sterile field. An initial CT 4.8 mm–29.8 mm) and the mean distance to the lesions from
exam was then performed as part of standard of care and the surface along the planned path was 76.8 ± 21.3 mm
the 3D anatomic map was generated from this dataset. The (SD) (range 43.5 mm–121.4 mm). The mean needle placement
procedure proceeded as was planned by the radiologist. The accuracy in the liver was 2.0 ± 0.7 mm (SD) for one-pass
radiologist adjusted the needles as was his practice and procedures and 2.8 ± 1.1 mm (SD) for two passes and the
performed CT scans to verify the needle trajectory and average procedure time was 9.9 ± 0.2 (SD) minutes (range
lesion position for targeting purposes. During the biopsy 9.55−10.1 minutes) and 11.9 ± 0.3 (SD) minutes (range
procedure, the navigational system was monitored in order to 11.8−12.4), respectively. In thoracic procedures, the mean
determine the registration accuracy of the needle tracked needle placement accuracy was 2.7 ± 1.7 mm (SD) and 3.0 ±
comparing the 3D anatomic map and the actual path as seen 1.4 mm (SD) for one and two passes, respectively. The average
in the CT images. This was specifically performed by com- time of navigated needle placement was 8.8 minutes ± 1.1
paring the actual needle tip position based on CT with the (SD) (range 6.6–9.8 minutes) for one-pass procedures and
Radiology Research and Practice 5

Table 1: Patient demographics. manner. That is the radiologist performed, the procedure as
standard of care without the ability to use or see the 3D
Patient demographics (𝑛 = 21) navigational system. Accuracy of final needle position was
Mean age, years 63.8 (17–85) determined by comparing where the 3D navigational system
Gender indicated the final needle position and where the CT images
Male, 𝑛 6 indicated the final needle position. This was done to avoid any
Female, 𝑛 15 potential adverse events in patients.
Lung biopsy, 𝑛 15 The final aspect of the study was to evaluate this 3D
Lung cryoablation, 𝑛 2 navigational system in clinical scenarios. In addition to deter-
Liver biopsy, 𝑛 5 mining if this system can generate sufficiently high accuracy
in needle position the system must be easily integrated into
the clinical workflow. In this study, we measured the time of
Table 2: Interventional procedure details. each part of the procedures. The use of this 3D navigational
Interventional procedures
system added an average of 3.1 minutes. From our experience,
(𝑛 = 22) using this system, we are confident that adding this system
into the clinical workflow should be easily done in an imaging
Mean target diameter
14.3 ± 6.7 (7.4–32.0) suite as prior EMN image fusion studies have suggested [14–
(mm)
18]. Of interest the degree of variance of the final needle tip
Mean target distance
63.1 ± 25.2 (28.7–109.7) position observed with the two-pass method was greater than
from skin (mm)
the degree of variance observed with a one-pass method.
There was no clear reason for this difference which was not
statistically significantly different.
12.8 minutes ± 1.2 (SD) (range 10.8–13.8 minutes) for the two- The navigation system in this study differs from others
pass method. The average 3D anatomic map registration error by providing 3D fully quantified anatomies, making the
was 1.79 mm. physician aware of the surrounding structures and facilitating
a needle path planning and placement with an intuitive
3.2. Clinical Application of Navigation System. In the clinical approach. Navigation systems like the one used in this study
application segment of this study, a total of 21 patients fuse different 3D imaging modalities (CT, MR, and PET),
consented to participate in this study. The average patient was from previously taken reference datasets to create a 3D
63.8 years of age (17–85); 68.2% of patients were female; see workspace. When the target is not well visualized under
Table 1. Fifteen procedures were lung biopsy; 5 were targeted the 3D working data set (usually US or CT) but had been
liver biopsies; and 2 were lung neoplasm ablations. previously seen, both the 3D working and reference data
The average diameter of targets was 14.3 mm ± 6.7 sets can be superimposed and aligned to create a new 3D
(7.4–32 mm) SD with a mean distance from skin of 63.1 ± working data set in which the electromagnetic needle can be
25.2 mm SD (range 28.7–109.7) (Table 2). Eighteen-gauge tracked in a real-time multiplanar display. This has shown
biopsy needles were used for lung biopsy, while 16-gauge potential utility for target lesions with FDG avidity in biopsy
needles were used liver biopsy. Both lung ablations were procedures [15].
performed with a 13-gauge cryoablation probe. The mean Additionally, particularly for ablation treatments, where
accuracy of the 3D navigation system in this passive study the delineation of the ablation zone and lesion is more
was 4.6 mm ± 3.1 (SD) (range 0.88–14.29). Sixteen of the 22 difficult to see during intraprocedural imaging, having the
procedures (72.7%) had an accuracy less than 5 mm. There pretreatment image fused with an intraprocedural scan may
was no significant difference in accuracy between body parts help to more effectively determine treatment margins. This
or types of the procedures in this trial (𝑝 = 0.0802) or the may translate to better accuracy and treatment outcomes
distance to target from the skin surface (𝑝 = 0.2859). Average for noninvasive image guided therapies such as cryoabla-
time of the system setup was 3.1 minutes. tion, radiofrequency ablation (RFA), and microwave ablation
(MWA) [23].
4. Discussion The results of this study compare favorably to other stud-
ies using similar methodologies. For example, Wallach et al.
The results from this study suggest that (1) this 3D navi- [24] observed a target positioning error of 4.6 ± 1.2 mm
gational system was able to obtain highly accurate needle for liver lesions comparing free hand placement to aiming
placement both in phantoms and in patient’s procedures; (2) device-navigation. This is similar to the results we found
the use of this system is feasible within the existing workflow in our phantom studies. This study goes further in that it
for interventional procedures. shows that this system can be translated to clinical use and
The needle placement accuracy was evaluated in multiple in both liver and lung procedures with similar (4.6 ± 3.1 mm)
scenarios. First, in the controlled environment of a phantom accuracy.
study, in this scenario, we were able to document final needle There are several limitations to this study. This was a
position accuracy of 2.3 ± 1.2 mm. Since a phantom procedure pilot study with a small number of patients and future
is an idealized situation, we extended these experiments to randomized controlled trials in which the trajectory planned
use in patients. In these cases, the device was used in a passive by the 3D navigation system is utilized will be necessary
6 Radiology Research and Practice

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