The contrast medium injector Accutron HP-D in the university hospital Würzburg

We have been using the double head injector Accutron HP-D of MEDTRON AG for the injection of contrast medium and physiological sa-line solution in the angiography units of the institute for diagnostic radi-ology at the university hospital Würzburg since August 2009. The use of this new type of injector offers several advantages:

The injector is equipped with high-output rechargeable batteries and thus en-sures a wireless, mains-independent operation during the interventions. More-over, the Bluetooth radio communication of the injector system allows a wireless coupling to the intervention unit. This is very important for us since the wireless flexibility of the device provides more room to move during interventional procedures with anaesthesia, several involved interven-tional radiologists and additionally required ultrasound diagnostics. De-pending on the workload, the mains-independent operation can be maintained continuously for 3 to 4 days. The batteries are usually recharged overnight.

A lasting flexibility of the contrast medium injector is furthermore en-sured by a flexible injection unit which is mounted on a mobile column stand.

The clearly structured operating unit with touch screen allows an easy handling with input of the required protocol parameters. The required parame-ters are contrast medium volume (ml), contrast medium flow rate (ml/s), injec-tion phases, delay (s) between the injection phases, contrast medium concentra-tion, X-ray delay (s) and pressure limit (psi or bar). Depending on the need, sin-gle-phase and multi-phase (max. three phases) examination protocols can be preselected.

Alternatively, these parameters can be selected by the radiologist by means of a sterile packed remote control. Before and during a contrast medium injection the screen shows the injection time (s), the injected contrast medium volume (ml), the time until the adjusted flow rate (s) has been reached and the pressure his-tory in the form of a curve. In total, up to 60 programmes can be edited and saved at the injection unit.

When an optimized high-pressure tube system has been connected to the con-trast medium and NaCl bottle, the syringes can be filled easily with contrast medium or a mixture of contrast medium and physiological saline solu-tion. The double head injector can only be activated after having confirmed the dialogue message “CM-syringe airfree”, and thus provides an additional and important function for the safety of the patient.

The integrated, heated syringe holder guarantees a trouble-free applica-tion even of highly concentrated iodic contrast media.

Like the previous models, the Accutron HP-D double head injector allows the ad-ministration of a NaCl flush bolus after the contrast medium injection. This “NaCl flush” initiates a continuous flow of contrast medium after the injection and the contrast medium bolus itself becomes longer. Thus, the contrast me-dium effects can be used more effectively for imaging. In our subjective opinion, especially the angiographic evaluation of the flow path at the foot in the context of the peripheral artery occlusive disease, and the identification of an active contrast medium extravasation in case of an acute bleeding can benefit from this. Moreover, as a side effect, the NaCl flush bolus contributes to a re-duction of the administered contrast medium volume.

We consider the possibility to set the contrast medium concentration or the mixing ratio of contrast medium and physiological saline solution to be a great advantage. The contrast medium concentration can be selected ac-cording to the patient’s weight by means of the Accutron HP-D. Lighter patients get for example a contrast medium concentration of 50%. Thus, the average amount of administered contrast medium is considerably reduced. Ac-cording to our impressions, the careful preselection of the contrast medium mix-ing ratio often keeps the increase of the renal retention parameters of patients suffering from a restriction of the renal function within accept-able limits.

In our daily routine we now apply to certain patients optimized protocols with a reduced contrast medium concentration, which are also adjusted to the low dose algorithms of our intervention units. There has not been a loss of information in the angiography image so far. As a result, “old” standard protocols are more and more replaced and only maintained for heavy or adipose patients.

By setting high contrast medium flow rates and injection pressures certain pathological changes or vessel alterations, which would have remained masked under normal injections conditions, can be identified in the angiography image.

This applies particularly to the detection of active contrast medium extravasa-tions in the sense of active bleedings, which can especially depend on the injec-tion pressure. In this context, pressure injections with the Accutron HP-D can be perfectly performed using either a diagnostic or a micro catheter.