Background and Goal of Study: Previously, over a period of three years, we have developed and refined ADAMgel(Aqueous Dietary fibre Antifreeze Mix gel). This material is used as a tissue analogue for ultrasound based proceduraltraining. It is produced by combining Ispagula (psyllium) husk, a commonly used dietary fibre laxative and food thickener,mono ethylene glycol (MEG), a standard antifreeze, and water, then heating it. This resulting material satisfies the criteriafor the ideal ultrasound medium1(IUM). Nevertheless we have continued to seek to improve the characteristics of thismaterial and sought to establish whether other combinations of dietary fibre based laxative/food thickener ADAMgels mighthave similar potential as IUMs.
Materials and methods: We identified Gellan Gum as being a practical alternative to psyllium in that it demonstratessufficient visco-elasticity to support ultrasound probe pressure. Accordingly concentrations of 2,4,6 and 8% were preparedwith water in the ratio MEG 9/1 and tested against the criteria for IUM.
Results and discussion: Gellan based ADAMgel performed favourably against the criteria for IUM. It reproduced high-fidelity haptic human tissue simulation .Targets were clearly visible up to 10cm and stayed fixed in position with clearlyidentifiable needle -target contact. This medium can be cast, moulded, cold-pressed or assembled in layers to createphantoms of varying complexity. It is non-perishable and has shown no deterioration after 6 months' storage at roomtemperature. It can be prepared using basic equipment at €3/kg. Most significantly, it does not sustain needle insertiondamage at gel concentrations < 8%.(Fig1-3). This is of particular relevance to phantom models that are likely to be subjectto multiple reuse.[Figure 1. Gellan based ADAMgel Sonographs]
Conclusion: Gellan based ADAMgel appears to be a useful medium for the basis of construction of regional anaesthesiatraining phantoms.References: Simulators for training in ultrasound guided procedures. 1. S. Sultan, G. Shorten, G Iohom MedicalUltrasonography 2013; 5,(2): 125-131

Beyond Ispagula - exploring alternative antifreeze infused laxative products as ultrasound medium for employment in regional anaesthetic training phantoms