Originally the concept of a team of mould room technicians and Medical Physicists from a Radiotherapy centre in the North of Scotland, the INVAC system is now offered exclusively by dha as a complete storage and maintenance solution for patient positioning vacuum bags.

The basic idea is simple but has never before been realised into a practical, and now heavily patented, device. Instead of just storing vacuum bags during use, INVAC allows the bags to be connected to a common manifold where the level of vacuum in all the bags is constantly monitored.

All plastics allow the slow passage of atmospheric gases into the evacuated volume of the bag in use, over a period of time. This combined with the slow release of gases (mainly water vapour) trapped on the surface of the filling material inside the bag into the vacuum, results in a slow but measurable deterioration of the vacuum inside the bag. These effects are proportional to the surface area of the bag and the volume of filling. As a result, larger bags will tend to deteriorate more quickly. The vacuum monitoring system of INVAC senses when the vacuum in any of the connected bags deteriorates and before any of the bags lose their preset shape and rigidity, switches on the INVAC vacuum pumping system to restore normal levels of vacuum.

The bags supplied by dha for use with the INVAC or any other system, are made from a unique high technology long chain polymer film called Platilon TM. Because of its microscopic structure, the bag has a much lower diffusion rate than many similar plastics, that is the speed at which atmospheric gases diffuse into the internal vacuum.

Another feature of Platilon, which makes it an exceptional choice for use in vacuum bags, is its extremely high puncture and tear resistance for its thickness. The bags are designed with integral support loops for use with the INVAC support frame and custom designed bag hangers shown. The combination of the integral loops and hangers ensures even weight distribution during storage on the support frame. The complete INVAC solution is shown here in use with pre-formed vacuum bags hanging on the support frame. The sensing manifold, which connects to all the bags during storage, is mounted on the lower frame with the vacuum sensor and pumping system just visible behind the bags.

For further information on INVAC or the range of Platilon vacuum bags, which can be manufactured to your specified dimensions and are available exclusively from dha, or to arrange a demonstration of the vacuum bag Life Support System, please contact sales@dha.co.uk or contact our Radiotherapy Sales team using any of our contact numbers.

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