Discussion

Haemorrhagic telangiectasia is a chronic disease that needs multi-disciplinary management and follow-up with multiple radiographic imaging modalities used on a regular basis resulting in an overall radiation burden which places these patients in a higher risk group for radiation-induced malignancies. ^{Reference Cevallos, Armstrong and Glatz13–Reference Miglioretti, Johnson and Williams15} Transcatheter closure of pulmonary arteriovenous malformations is a well described and accepted therapy. ^{Reference Garg, Khunger, Gupta and Kumar1,Reference Muhammad, Rauf, Shahid, Iqbal, Haq and Zafar5} The lesions are usually multiple, very distal in the lung parenchyma, and have complex morphology, which can make transcatheter embolisation a long and challenging procedure. This is further complicated by the need for multiple angiograms, which are challenging to interpret given numerous overlapping pulmonary branches on fluoroscopy.

In our experience, the added value of fusion imaging technology in these procedures is as follows. Firstly, as part of procedural planning, to determine the correct angiographic angles of interrogation and the size of the vessels involved, thus, narrowing the scope of devices that need to be available. This in itself can aid planning and reduce case time and complexity. Second, the initial diagnostic angiographic imaging is likely reduced due to the use of VesselNavigator^TM live guidance images superimposed on fluoroscopy. Thirdly, the combination of these features can lead to less contrast volume, fluoroscopy, and cine-angiographic image acquisition. As expected with our limited patient population, and the lack of a control group, we have a limited ability to demonstrate statistical superiority of fusion imaging over standard two-dimensional imaging. Nonetheless, this expected benefit has been previously demonstrated in other interventional procedures such as transcatheter pulmonary valve replacement, pulmonary vein stenosis, as well as other oncological and vascular interventions, showing a significant decrease in contrast dose and procedural duration. ^{Reference Markelj, Tomaževič, Likar and Pernuš8,Reference Ehret, Alkassar and Dittrich10,Reference Goreczny, Moszura and Dryzek11}

The first report to our knowledge, of the use of fusion imaging technology specific for pulmonary arteriovenous malformations embolisation, was recently published and showed a significant decrease in contrast dose when compared to standard two-dimensional imaging in this single centre (118.3 mL versus 285.3 mL; p < 0.002) but with no statistically significant difference found in procedural duration (19.5 min versus 31.4 min p = 0.054) ^{Reference Garnier, Curado and Grancher9} . In our series, predominantly paediatric, which inherently increases complexity of interventional procedures, we report a mean contrast dose of 28.8 mL (11–60 mL, 0.51 mL/kg), far lower (approx. 20%) than that reported by Garnier et al. (118.3 mL, range 50–300 mL) with a 29% higher mean number pulmonary arteriovenous malformations treated per patient in our series (3 versus 2.33). The same is true for radiation dose, where we report a mean of 66.3 mGy (25.6–140 mGy and an indexed mean dose of 40.5mGy/m²) compared to 599.9 mGy. When excluding patients with reintervention of previously embolised pulmonary arteriovenous malformation, the mean radiation dose was even lower at 55.6 mGy (34.4 mGy/m²). Nevertheless, we show a longer mean fluoroscopy time of 40.6 min (10.7–68.8 min) compared to the extremely low 19.5 min (range 8–44 min) reported by Garnier. This may be partially explained by the higher number of treated lesions per case. However, despite the longer fluoroscopy time, it is important to note that the total and indexed radiation doses are significantly lower than those reported elsewhere. Thus, we consider this a technique with minimal radiation and contrast exposure important in a predominantly paediatric population.

The most significant advantage to the use of fusion imaging technology for embolisation of pulmonary arteriovenous malformations seems to be related to the dose of contrast and radiation. However, we must highlight the importance of using fusion imaging for pre-procedural case planning, to generate angiographic angles and select occlusion devices, which can further decrease the use of contrast and radiation dose as well as optimising efficiency and resource utilisation in these and other patients. We report a contrast and radiation dose far below that previously reported in the literature, likely due to our use of customised low radiation and contrast protocols, which are made feasible by the reliance on overlay fusion imaging. ^{Reference Zablah, Rodriguez, Leahy and Morgan16} The recognition that haemorrhagic telangiectasia patients require recurring ionising radiation-based diagnostic and intervention procedures for various arteriovenous malformations behoves us to minimize contrast and radiation dose to help preserve renal function and decrease lifetime radiation-based complications. ^{Reference Nobre, Oliveira-Santos, Paiva, Costa and Gonçalves6,Reference Goreczny, Morgan, McLennan, Rehman and Zablah7,Reference Garnier, Curado and Grancher9}