More than the Sum of Its Parts: The Synergy of Hybrid Angiography–Computed Tomography Systems in Interventional Radiology

Hong Kong J Radiol 2025 Dec;28(4):e232-3

 

 

Department of Radiology, Hong Kong Children’s Hospital, Hong Kong SAR, China

 

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The introduction of cross-sectional imaging during procedures has greatly improved treatment precision and allowed real-time assessment of therapeutic outcomes, particularly in the realm of interventional oncology. The first hybrid angiography–computed tomography (angio-CT) system was developed in the early 1990s by Professor Yasuaki Arai at Aichi Medical Centre in Japan.[1] In its early stages, integration between the two modalities was minimal, with each operating largely independently and requiring the operator to manually combine the imaging data.[2] The development of flat-panel detectors in the late 1990s paved the way for the rapid adoption of cone beam CT (CBCT). Compared to angio-CT, CBCT has since become the more widely utilised modality,[3] largely attributable to the higher cost and infrastructural demands of angio-CT systems, particularly the need to accommodate a sliding gantry. However, recent advances in workflow efficiency, decreasing relative costs, and the multipurpose capabilities of angio-CT systems have led to renewed interest. Increasingly, institutions are accepting the higher upfront investment, recognising the potential long-term benefits in terms of improved patient outcomes and enhanced procedural room utilisation.

 

In this issue of the Hong Kong Journal of Radiology, Wong et al[4] presented a case-based review that explores the advantages of angio-CT technology through a series of illustrative examples. While most of the interventional radiology (IR) literature has focused primarily on oncologic applications, this review highlights its broader utility in various vascular interventions, including embolotherapy for acute haemorrhage, management of pulmonary arteriovenous fistulae, and adrenal venous sampling. Additional potential non-oncological applications—though not addressed in this review— include complex drain placements, acute trauma management, prostate artery embolisation, geniculate artery embolisation, complex venous reconstruction, and lymphatic interventions.[5] [6] These examples underscore the versatility of angio-CT systems across a wide spectrum of IR procedures.

 

The most significant advantage of angio-CT lies in its ability to integrate high-resolution CT imaging with selective angiography and fluoroscopy, thereby eliminating the need to transfer patients to a separate CT scanner during critical procedural steps. Motion and beam-hardening artefacts commonly encountered with CBCT are minimised with angio-CT due to its superior temporal resolution. The capacity to accurately delineate perfused tissue volume is particularly valuable in procedures where extra-target embolisation may have serious consequences, such as geniculate artery embolisation and prostate artery embolisation. Additionally, the ability to provide three-dimensional needle guidance is invaluable for complex interventions such as sharp recanalisation in venous reconstructions and antegrade percutaneous puncture of the cisterna chyli. In the setting of acute polytrauma and stroke, angio-CT enables both diagnostic CT and subsequent therapeutic embolisation to be performed within the same gantry, thereby saving precious time and reducing the risks associated with transferring critical, often haemodynamically unstable, patients from one venue to another.

 

Converting a conventional IR suite into a hybrid angio-CT suite has been shown to enhance operational efficiency across both IR and diagnostic radiology services. This conversion allows CT scanners, which previously had to be shared between diagnostic and interventional services, to be dedicated solely to diagnostic imaging, while enabling CT-guided procedures to be performed directly within the hybrid IR suite. For instance, one institution reported a 19.1% relative increase in the utilisation of formerly shared CT scanners for diagnostic imaging, along with a 287.1% relative increase in the use of the hybrid IR suite, compared with the overall growth rates of both diagnostic radiology and IR departments.[7] [8] In addition, the potential use of the angio-CT scanner as a diagnostic scanner affords scheduling flexibility for both patients and physicians and contributes to workflow efficiency and optimisation.

 

A major limitation of angio-CT systems is the substantially higher cost of installation compared with single-modality fluoroscopy suites. In addition, these systems require a larger physical footprint, typically at least 50 m², to accommodate both CT and fluoroscopy units. To date, robust quantitative evidence demonstrating improved patient outcomes or cost-effectiveness is lacking. Comparison of radiation dose between CBCT and angio-CT is also challenging due to variability in imaging protocols and technical parameters, which introduces uncertainties in direct comparisons. Notably, a CT acquisition during a procedure may reduce the need for multiple digital subtraction angiography runs, thereby lowering and more evenly distributing overall radiation exposure to the patient. While one study found no significant difference in effective dose per CT scan between CBCT and angio-CT,[9] limited available data suggest that angio-CT systems may reduce the overall effective dose from both CT and angiographic imaging compared with CBCT systems.[10]

 

Hybrid angio-CT systems offer institutions a valuable opportunity to expand treatment capabilities and optimise workflow. The integration of diagnostic-quality intraprocedural CT with conventional angiography and fluoroscopy has substantially broadened the scope of interventional procedures while improving room utilisation. While the synergistic benefits of angio-CT are clear, the decision to invest in such a system should be informed by a comprehensive needs assessment and institutional considerations, including case mix, procedural complexity, patient volume, and the potential to enhance workflow efficiency and translate into improved patient outcomes.