Dual-phase cone-beam computed tomography (DP-CBCT) is a useful intraprocedural imaging technique for transarterial chemo-embolization treatment with drug-eluting beads of hepatocellular carcinoma. DP-CBCT has been used to perform three major steps in oncologic interventional radiology: tumor localization (see), navigation and intraprocedural catheter guidance (reach), and intraprocedural evaluation of treatment success (treat).
The advent of cone-beam computed tomography (CBCT) in the angiography suite has been revolutionary in interventional radiology. CBCT offers 3 dimensional (3D) diagnostic imaging in the interventional suite and can enhance minimally-invasive therapy beyond the limitations of 2D angiography alone. The role of CBCT has been recognized in transarterial chemo-embolization (TACE) treatment of hepatocellular carcinoma (HCC). The recent introduction of a CBCT technique: dual-phase CBCT (DP-CBCT) improves intra-arterial HCC treatment with drug-eluting beads (DEB-TACE). DP-CBCT can be used to localize liver tumors with the diagnostic accuracy of multi-phasic multidetector computed tomography (M-MDCT) and contrast enhanced magnetic resonance imaging (CE-MRI) (See the tumor), to guide intra-arterially guidewire and microcatheter to the desired location for selective therapy (Reach the tumor), and to evaluate treatment success during the procedure (Treat the tumor). The purpose of this manuscript is to illustrate how DP-CBCT is used in DEB-TACE to see, reach, and treat HCC.
Image guidance is the backbone of interventional radiology. Two relatively recent capabilities of the X-ray angiography equipment are three-dimensional (3D) rotational angiography, and C-arm cone-beam computed tomography (CBCT). CBCT has enabled the acquisition of 3D volumetric imaging in the angiography suite with the advent of the C-arm, the flat panel detector and the Feldkamp back projection algorithm1,2. These newer image acquisition capabilities have enabled clinicians to perform procedures not feasible with traditional fluoroscopy or digital subtraction angiography alone3-7. Recent improvements in image quality allow the comparison of CBCT images being with diagnostic imaging8,9. Moreover these recent tools can improve accuracy of a growing variety of interventions5,7.
Transarterial chemoembolization (TACE) is a therapeutic option for hepatocellular carcinoma (HCC) per Barcelona Clinic Liver Cancer staging and treatment algorithm10. Intraprocedural imaging directly guides this interventional oncology procedure. The intervention planning is a key step to optimize devices needed for procedure, determination of the best view to reach the tumor(s), potentially improving drug delivery to targeted tumor(s), and theoretically reducing potential complications. Tools for image acquisition, intraprocedural guidance, and therapeutic response assessment have been developed for use during TACE, to optimize TACE. The use of dual-phase CBCT (DP-CBCT) especially during TACE with drug-eluting beads (DEB-TACE) provides more information than traditional fluoroscopy, CBCT without contrast injection, or single phase enhanced CBCT11. Indeed, DP-CBCT is two five-seconds CBCT scans (early arterial and delayed venous phases) done intraprocedurally during one single intra-arterial injection17,21-23. DP-CBCT could be described as an essential tool in the armamentarium of the interventional oncologist to standardize TACE approach on a daily basis.
Firstly, DP-CBCT imaging is highly sensitive and specific for detecting HCC. It compares favorably to the existing gold standard, contrast-enhanced magnetic resonance imaging (CE-MRI) and multiphasic-multidetector computed tomography (M-MDCT)8,9,12. Accurate detection and tumor volume segmentation can be obtained from CBCT images often the delayed venous phase scan unless better visualization is achieved on arterial phase8,13,14. Secondly. DP-CBCT can generate a roadmap for the hyperselective catheterization and identification and embolization of feeding vessels. Recent data demonstrates that hyperselective chemotherapy delivery is associated with lower complications and improved results 15-17. Finally, DP-CBCT provides an intraprocedural predictive assessment of liver tumor (HCC) response after intra-arterial therapy and may augment or predict six-weeks follow-up CE-MRI18. The use of CBCT imaging during TACE has been shown to increase survival19.
The purpose of this manuscript is to describe the use of CBCT to execute the steps of DEB-TACE: seeing, reaching, and treating liver tumors. Modification of the DEB-TACE based upon DP-CBCT information is a common clinical scenario.
DP-CBCT is a useful tool to facilitate the three main steps in intra-arterial liver therapy: tumor localization (see), navigation planning and intraprocedural guidance for catheterization (reach), and intraprocedural evaluation of treatment goals and success (treat).
Firstly, DP-CBCT is as equally sensitive and specific for detecting HCC as current gold standard imaging techniques including, contrast-enhanced MRI and MDCT8. In addition, tumor segmentation and volume calculations on DP-CBCT are precise and reproducible13. Furthermore, the volume and the spatial localization of target lesions on CBCT and on MRI are strongly correlated13. Most importantly, this information is available during the procedure, when it is most needed.
Secondly, DP-CBCT can be used to generate a navigation "map" in order to reach difficult lesions and improving tumor targeting results in decreased nontarget embolization, increased tumor coverage and preservation of normal hepatic tissue.
Thirdly, the use of DP-CBCT immediately following therapy is predictive of treatment success, and may be used instead of a six weeks MRI or MDCT to assess treatment completeness18.
While respiratory motion can induce misalignment in image registration, the 3D roadmap can be adjusted visually by the operator using the catheter's position on fluoroscopy as a reference. Moreover more significant patient motion can be corrected manually by shifting the 3D roadmap on real-time fluoroscopy using bony landmarks or the catheter as a reference. Visual gating can be performed in this way, waiting for matched respiratory cycles to make catheter manipulations. Patient comfort is essential and an 8 sec breath-hold is needed to avoid significant motion artifact and significant image quality degradation. If necessary, oxygen can be administered to the patient during the acquisition to minimize the discomfort of breath holding.
The limitations of the CBCT include imaging artifacts and X-ray exposure. CBCT images present artifacts due to multiple sources such as noise, scatter, partial volume effects, beam hardening, ringing, and motion. Several algorithms have been developed to reduce noise during reconstruction, modify the X-ray spectrum or to reduce motion artifacts20-26. The direct impact of these artifacts during the DEB-TACE has not been, described to the author's knowledge. CBCT X-ray exposure is generally less than MDCT of similar protocol. In cases of diffuse liver disease, embolization can be performed from a proximal location. A 3D roadmap may not be necessary in those instances. Then, MDCT or MRI preprocedural images can be used to generate a 3D roadmap for proper hepatic artery catheterization. An intraprocedural DP-CBCT post therapy can still be used to predict treatment success when drug eluding beads are used
DP-CBCT is a useful tool in interventional oncology which can be used to standardize DEB-TACE procedures. DP-CBCT provides information that improves the three major steps of TACE procedures: see, reach and treat liver tumor.
The authors have nothing to disclose.
The authors wish to acknowledge the financial support of NIH/NCI R01 CA160771, P30 CA006973, Philips Research North America, Briarcliff Manor, NY, USA and the French Society of Radiology (SFR).
Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
Angiographic system (Allura Xper FD20) | Philips Healthcare, Best, The Netherlands | Angiographic system made of a C-arm computed tomography (CBCT) and a flat panel detector | |
Workstation (XtraVision 8) | Philips Healthcare, Best, The Netherlands | Workstation for CBCT images reconstruction and postprocessing | |
Contrast agent: Oxilan 300 (Ioxilan) | Guerbet LLC, Bloomington, IN, USA | Contrast agent used for acquiring DP-CBCT images | |
Sheath | (5Fr) | ||
Catheter | Terumo Medical, Somerset, NJ, USA | Glide Simmons 1 (5Fr) | |
Microcatheter | Boston Scientific, Natick, MA, USA | Renegade Hi-Flow (3Fr) | |
Steerable guidewire | Boston Scientific, Natick, MA, USA | Fathom wire (0.018 in) |