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Abstract
Background and aim Accurate direct puncture access to vascular malformations and tumors of the head and neck is critical to successful embolization treatment and avoidance of complications. The primary focus of this project was to evaluate the accuracy and ease of needle placement using integrated 3D cone-beam CT and fluoroscopic guidance in accessing head and neck vascular malformations and tumors, and to determine its contribution to lesion treatment.
Methods A total of 27 patients, 14 female and 13 male, aged 4–63 years, were included in this study. The lesions included 11 venous malformations, 5 arteriovenous malformations, 5 juvenile nasopharyngeal angiofibromas, 2 lymphovenous malformations, 1 lymphatic malformation, 1 capillary malformation, 1 nasal cavity leiomyoma, and 1 dural arteriovenous fistula. A total of 65 needle placements in 33 procedures were performed using an integrated 3D cone-beam CT and fluoroscopic guidance system.
Results Targeting was successful with a single pass in 62 of 65 planned needle placements to a superficial location in 24, the hypopharynx, retro-pharyngeal, pyriform sinus, or paratracheal spaces in 21, the sphenoid sinus and upper nasal cavity via trans-nasal approach in 5, intra-orbital in 5, intra-laryngeal in 4, pterygo-palatine fossa in 4, external auditory canal in 1, and intracranial via a juxta-torcular burr hole in 1. Needle placement was within 2 mm of the planned target in 11 locations in the 8 patients where post needle-placement cone-beam CT was obtained.
Conclusion This integrated 3D cone-beam CT and fluoroscopic guidance allowed access to deep, difficult to access, locations with ease using a single needle pass in most cases, resulting in improved treatment with decreased procedure times.
- Neck
- Malformation
- Tumor
- CT
- Navigation
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Accurate direct puncture access to vascular lesions of the head and neck is critical to successful embolization treatment and avoidance of complication. Although less has been written on palpation or fluoroscopic guidance, much has been written on access obtained via sonographic,1–8 CT,1 9–13 or MR guidance14–18 to access lesions for aspiration or biopsy. However, the requirement for angiographic delineation creates added complexity of quick and easy access to an angiographic C-arm. Angiographic injection of the needle is crucial to the evaluation of direct puncture treatment of head and neck vascular lesions being embolized or sclerosed to assess the vascular filling and determine the appropriateness and volume of treatment material to inject.19–26 Palpation, fluoroscopic, and sonographic localization work well for superficial lesions or those with an acoustic window or radiographic landmark, but CT or MR guidance is the only method where deep lesions can be consistently and adequately localized. Angiographic C-arms are incompatible in the MR suite, except in rare integrated systems, which makes CT the preferred method in these cases where other methods fail. This requires either a combined CT/angiographic suite or limiting the angiography by using a portable angiographic C-arm in the CT scanner suite. The advent of cone-beam CT acquisitions using dedicated angiographic systems allows the performance of these procedures with CT guidance and excellent angiographic capability. These combined units enable the creation of integrated guidance systems to improve the technique of combined CT and fluoroscopic guidance. The primary focus of this project was to evaluate the accuracy and ease of needle placement using an integrated 3D cone-beam CT and fluoroscopic guidance system to access head and neck vascular malformations and tumors, and to determine its contribution to lesion treatment.
Patients and methods
Patients
A total of 27 patients, 14 female and 13 male, aged 4–63 years. were included in this study. The lesions included 11 venous malformations (VMs), five arteriovenous malformations (AVMs), five juvenile nasopharyngeal angiofibromas (JNAs), two lymphovenous malformations (LVMs), one lymphatic malformation (LM), one capillary malformation (CM), one nasal cavity leiomyoma, and one dural arteriovenous fistula. A total of 65 needle placements in 33 procedures were performed using the integrated system (Xper CT and Xper Guide, Philips Medical Systems, Bothell, Washingto, USA). Multiple needle placements were performed in a single procedure to achieve an expected clinical result and multiple procedures were performed in four patients either owing to planned staging of treatment or owing to limited response from the initial procedure. The target size, number of needle passes, access accuracy, fluoroscopy and procedure times, and specific times for planning and placement, were assessed. The target size was defined as the maximal diameter of the region that needed access, and correct placement was defined as needle placement into the expected target that allowed us to successfully treat. Based on the dictated report the start and finishing times of the procedures, not including anesthesia time, and the fluoroscopy times were recorded.
Technique
Depending upon location of entry point(s) and lesion(s) the patient is placed in a relatively firm (more open access) or rigid (more fixed positioning) head holder and a relatively wide sterile preparation is made to cover the maximum number of possible entry points. After this, a 3D cone-beam CT (25 cm FOV, 0.98 mm pixel width, 5 mm reconstructed section thickness) without contrast material is performed for all lesions except AVMs, and the lesion is correlated with the pre-procedure MRI and/or CT to plan needle trajectory and target point. In head and neck AVMs, 3D rotational angiography (3DRA) with intra-arterial external carotid artery branch injection is performed and directly or indirectly coordinated with the 3D cone-beam CT. The soft tissue-density masses are often difficult to distinguish from muscular, vascular, or mucosal structures, but with careful correlation with prior available MRI, a reasonably safe trajectory can be determined. Special attention is made to osseous structures (mandible, maxilla, nasal turbinates, spine, etc) or critical vascular structures (carotid artery, jugular vein) to avoid obstacles to needle passage and to provide excellent reference points for correlation. Phleboliths in VMs are often helpful in localization and planning as they are readily apparent on MRI and the cone-beam CT and can usually be seen on fluoroscopy.
The needle trajectory planning phase is performed on the workstation using the integrated 3D fluoroscopic guidance system and can be planned via two methods—two-point target/entry point selection or click-and-drag trajectory placement (figure 1). In the two-point mode the user selects the target point and then selects the entry point on the current or any other cone-beam CT slice. In the click-and-drag mode the user initially selects any cone beam CT plane parallel to the trajectory and then clicks on the target and drags to the entry point. Any plane, orthogonal, or complex oblique can be used with either method. All of the planned needle placement trajectories (from 1 to 8 in this series) are performed before the initial needle placement to maximize efficiency, and minimize patient movement with respect to the guidance system. Trajectory viability confirmation is performed during this planning phase with a visual reference of patient position and warning icons constantly in view during planning. Confirmation is also performed with single-click ‘entry point view’ (down the barrel), ‘progress view’ (90 degree orthogonal, optimized to table position), ‘accessory progress view’ (10 degree angulation from progress view maintaining orthogonal to entry point view), and ‘custom progress view’ (user-selected angle maintaining orthogonal to entry point view).
Direct puncture of the sphenoidal portion of a juvenile nasopharyngeal angiofibroma via the trans-nasal approach. (A) Sagittal T1 fat-suppressed post-gadolinium MRI demonstrates a large nasal cavity and sphenoidal mass. (B) Angiogram following intra-arterial embolization (using polyvinyl alcohol and coils) of the internal maxillary artery demonstrates continued filling of the sphenoidal portion via small branches arising from the cavernous and petrous internal carotid artery (ICA). (C) Initial cone-beam CT and integrated 3D guide target placement in the sphenoid sinus portion. (D) Entry point placement at the right nares. (E) Trajectory within the nasal cavity. (F) Trajectory image fluoroscopic overlay entry point view down the barrel. (G) Progress view with needle along trajectory. (H) Intratumoral ‘angiogram’ showing tumor filling without filling of the ICA.
The visual display demonstrates a cylinder demarcated by a circle (orange) at the entry point and a circle (yellow) at the target connected by a 1 mm increment dotted line (green) at its center point (figure 1). The cylindrical diameter (5 mm default) can be easily modified by the user. This cylinder is the reference used on fluoroscopy during the needle placement phase and is maintained using any of the four defined views (entry point to custom progress) or any other projection the user selects during positioning of the angiographic/fluoroscopic C-arm. This allows for one to select a target and trajectory, but, if the entry point is not accessible owing to poor planning or sterile preparation, poor fluoroscopic visualization of the planned plane such as the lateral lower neck region, or conflicting needle hub locations, one can still access the target via any other trajectory using variable positioning of the fluoroscopy during careful placement of the needle to the planned target.
The needle placement phase begins by selecting the guidance system on the table-side module. The overlay of a CT image/fluoroscopy/trajectory is immediately projected. The user initially selects ‘entry point view’ and holds the ‘accept’ button down until the C-arm reaches the selected location. The image then projects a circle (down the barrel with a center dot). With single-plane fluoroscopy, the user then localizes the entry point, places the needle using a needle holder or hemostat clamp on the center dot, realigns the needle down the barrel, and advances it 1–2 cm to achieve a reasonably stable position within the tissue. After releasing the needle, fluoroscopic confirmation reveals a good or correctable position. If the needle has fallen significantly out of alignment, further advancement under fluoroscopy with the entry point view can correct the alignment.
The user then selects ‘progress view’ (or the ‘angled’ or ‘custom progress’ views) and then holds the ‘accept’ button until the C-arm achieves this position. The image then projects a rectangle consisting of two lines (orange entry point and yellow target) connected by a dashed line (green center-line trajectory). Depending upon positioning and magnification, the entry point line may not be included on the image. The needle is visualized fluoroscopically and advanced to the target (or slightly beyond to account for tissue recoil). If the trajectory distance is significant (>6 cm), advancing to the half-way point and reconfirmation with the entry point view followed by final positioning in the progress view allows for target point acquisition with a single pass. Final confirmation of target access is made with return to the entry point view. At this time, one can confirm intralesional location with a needle injection angiogram and return to the guidance system for subsequent needle placement or proceed to other needle placement, as long as the table position is not changed and the patient does not move.
The user can then select the next needle and proceed as outlined above. All needle placements are usually performed first, before contrast injections or treatment to minimize patient movement during the, sometimes painful, treatment phase. Intralesional contrast injection is performed to demonstrate intravascular (arterial, venous, capillary, or lymphatic) filling, and treatment proceeds with injection of therapeutic material (absolute alcohol (AVM, VM, LVM), doxycycline (LVM, LM), or dimethylsulfoxide/Onyx 18 (JNA, Tumors, CM).
Results
The 65 planned needle placements in the 27 patients was to a superficial location in 24 placements, the hypopharynx, retro-pharyngeal, pyriform sinus, or paratracheal spaces in 21, the sphenoid sinus and upper nasal cavity via trans-nasal approach in five (figure 1), intra-orbital in five (figure 2), intra-laryngeal in four, pterygo-palatine fossa in four, external auditory canal in one, and intracranial via a juxta-torcular burr hole in one . The 3D CT guidance system was used in the 24 superficial locations in patients with multiple needle placements who had deeper lesions or in patients with superficial AVMs where other techniques might be less accurate. The target size was highly dependent upon the type of lesion. Target size maximal diameter ranged from 1.2 to 5.4 cm, mean 2.5 cm, in VMs, LMs, LVMs, CMs and JNAs, whereas the target was 0.5–0.8 cm in the AVMs and the dural arteriovenous fistula.
Direct puncture of an orbital venous malformation. (A) Cone-beam CT axial image showing the optic nerve and lateral rectus muscles (arrows). (B) Cone-beam CT axial image (7 mm above A) showing trajectory path between the globe, lateral, and superior rectus muscles with target lateral to a small phlebolith (arrow). (C) Post needle placement cone-beam CT showing needle along planned trajectory path within 2 mm of planned target. (D) Intralesional ‘venogram’ demonstrating filling of the micro-cavernous spaces of the venous malformation.
The number of 3D CT-guided needle placement locations, based on a single cone-beam CT, ranged from one to eight in a single procedure. Needle placement was successful with a single needle pass in 62 of the 65 procedures with three failures occurring in superficial locations owing to poor fluoroscopic visualization of the needle in a VM, difficult co-localization with 3DRA of the small draining vein in an AVM, and significant angulation from operator-planned deviation from planned trajectory (owing to the location of the sterile–prepped field) in another VM. The two VM locations were successfully accessed using ultrasound and the AVM site was successfully located using the same 3D CT guidance system and 3DRA on a follow-up procedure.
Needle placement was confirmed as within 2 mm of the planned target in 11 locations in eight patients where post-placement cone-beam CT was obtained. Four of these patients had VMs with no blood return, and cone-beam CT was obtained to confirm the location. After confirmation a contrast injection confirmed correct intralesional injection (figure 2). Our confidence in the accuracy of this system after these four patients led us to proceed with injection after needle placement in subsequent patients. In the other four patients, follow-up cone-beam CT was obtained owing to patient movement during multi-needle placement in these conscious sedated patients. Fluoroscopy times using the 3D navigation system ranged from 48 to 66 (mean 58) seconds per needle placement, including positioning times. Procedures times ranged from 5 to 17 min (mean 6 min) per needle placement with the longer times in patients with single needle treatment. In prior procedures using fluoroscopic guidance performed on seven patients without this system, the fluoroscopy time ranged from 168 to 322 (mean 287) seconds per needle placement, and the procedure time ranged from 10 to 22 (mean 16) minutes per needle placement.
The cone-beam CT phase added an average of 38.6 mGy radiation dose to the procedure technique, and varied depending upon the image acquisition technique used: high dose 48.5 mGy, low dose 25.7 mGy, and 3DRA 8.6 mGy. The cumulative dose of all sources (cone-beam CT, fluoroscopy, and angiography) ranged from 57 to 160 mGy per needle placement, with the lower per-needle doses in those patients with the higher number of needles placed.
Discussion
Direct puncture access to vascular lesions of the head and neck is a technique that is commonly used in low-flow and high-flow lymphatic and vascular malformations and in direct tumor embolization in patients for whom intra-arterial treatment carries high risk.19–29 Accurate trajectory planning and implementation and precise needle location is critical to the successful embolization treatment and avoidance of complications. Needle placement in these patients is often obtained via palpation or ultrasound in superficial lesions and lesions with an appropriate sonographic window. In some circumstances, fluoroscopic localization can be used when radiographic features, such as a phlebolith or osseous landmarks, are available. However, high-risk soft-tissue structures such as the carotid artery cannot be visualized. Though CT guidance is a highly effective method for trajectory and needle placement,1 9–13 the need to perform digital subtraction injections requires angiographic equipment, and this combination is cumbersome to use in the CT scanner suite. MR guidance is also effective in lesions poorly visualized by other methods, but complicates the technique and limits the devices that can be used.14–18 In addition, angiographic delineation is virtually impossible without moving the patient to another room or area.
Angiographic delineation of the lesion is necessary to determine the appropriateness and amount of treatment material to inject and to detect potential high-risk aspects. In many cases, high-resolution angiography is needed to visualize subtle aspects of the vasculature, such as retrograde filling of tiny branches to the ophthalmic or internal carotid artery.19–26 The advent of 3D cone-beam CT acquisitions using the angiographic system allows the performance of these procedures with CT guidance and excellent angiographic capability. Integrated 3D cone-beam CT and fluoroscopic guidance systems have been developed to take advantage of this and simplify the technique of combined CT and fluoroscopic guidance. The primary focus of this project was to evaluate the accuracy and ease of needle placement using such a guidance system when accessing head and neck vascular malformations and tumors, and to determine its contribution in lesion treatment.
Our results have shown that integrated 3D cone-beam CT and fluoroscopic guidance systems provides a highly accurate and user-friendly system for needle placement in the treatment of head and neck vascular malformations and tumors. The accuracy of the system was within 2 mm of the planned target in the eight patients where post-needle placement cone-beam CT was obtained. This is similar to the reported accuracy of 1.1 mm in phantom studies in frameless neurosurgical intraoperative guidance systems.27 Our clinical needle tip targeting accuracy appears to be better than the recent reports of 3.0–3.5 mm error in standard and intracranial phantom studies using the same integrated 3D fluoroscopic guidance system.28 29 This discrepancy may be due to more precise needle placement with respect to the 3D overlay target by the neurointerventionalists in our study, but may also be due to the verification method used in our study—namely, a follow-up cone-beam CT. Nonetheless, this accuracy is reasonable in lesions >10 mm. It is especially helpful in deeper lesions and lesions that cannot be accurately localized with fluoroscopy, ultrasound, or palpation. The accuracy is decreased in superficial lesions owing to difficulties in fluoroscopic visualization of the needle and image distortion that can occur at the margins of the fluoroscopic detector. However, these lesions are usually easily accessed by other methods such as sonographic or palpation localization.
Compared with needle placement using conventional CT guidance, integrated 3D cone-beam CT-guided placement is much more efficient owing to the fluoroscopic localization. Although CT fluoroscopy can be used in today's conventional CT scanners and may show the needle in the plane scanned, it carries a much higher radiation dose and has difficulty if the needle is not in the plane being scanned. Although we have used conventional CT guidance in conjunction with a portable digital subtraction angiography C-arm in the past, difficulties with placement of the C-arm in conjunction with the CT table, the limited resolution of the DSA system, and generalized complexity of performing neurovascular interventional procedures in the CT scanner suite make it difficult.
The image acquisition time and reconstruction time have decreased with 3D cone-beam CT, and the integration allows the planning and placement phases to occur quite quickly, usually less than a minute per needle placement, even in the more complex cases. This is in contrast to non-integrated 3D guidance systems used in head and neck surgery and neurosurgery. The early experience using these systems for the same purpose as our study requires on average 45 min of download, planning, and set-up time using a CT or MR acquisition with fiducials.30 The advantage of non-integrated systems compared with the integrated systems in this report is that they are not as sensitive to patient movement as long as the reference points remain stable. The three-dimensional planning capability and the ease with which the plane can be altered make the integrated 3D cone-beam method very efficient in the planning phase, and enable complete analysis of the trajectory and potential obstacles quickly.
Integrated fluoroscopic visualization also allows for correction or modification of a trajectory during needle placement and allows one to easily change the position of the C-arm while still visualizing the trajectory and the target in any projection. This capability is not available in the non-integrated systems where the needle is placed based on a pre-planned trajectory without visualized guidance. Alternative trajectories can be planned using these systems, if needed, but this usually requires a significant amount of time.
Patient movement during the needle placement phase is the most significant limitation and precautions to prevent this are critical. Because the system uses a CT overlay along with the trajectory, one can see significant movement as mis-registration of the osseous landmarks. One can repeat the 3D cone-beam CT and repeat the planning phase relatively quickly, but this does add radiation exposure and some procedural time. Although one can integrate imaging datasets such as 3DRA obtained at the same setting, another current limitation is the lack of availability in integration of prior imaging datasets such as MR or contrast-enhanced CT studies, which can be done using non-integrated systems. This is currently being developed and may be available shortly.
Integrated 3D cone-beam CT and fluoroscopic guidance systems such as the Xper Guide system have significantly improved our ability to place devices with ease and sufficient accuracy compared with other systems. In our experience, locations which were considered nearly impossible without this technique can be accessed quite simply. This technique may have other applications in neurointerventional and other neurosurgical procedures where the accuracy limitations would be appropriate. The direct burr-hole puncture of a torcular dural arteriovenous fistula is one such case. Procedures such as ventriculostomy placement, placement of intracranial drains, and potentially, biopsy of intracranial masses are potential uses of this integrated system, especially in patients where knowledge of the vascular anatomy may be crucial.
Conclusion
Integrated 3D cone-beam CT and fluoroscopic guidance allows access to deep, nearly inaccessible, regions with ease using a single needle pass, resulting in improved treatment with decreased procedure times. This has become our preferred technique in deep and difficult to access lesions of the head and neck.
References
Footnotes
Competing interests None.
Ethics approval This study was conducted with the approval of the Oregon Health & Science University Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.