Syringe Body - Barrel
Figure 1 • Prefilled syringe components.
The correct use of CM injection
systems ensures that the solution is
dispensed at a predefined flow and
volume. Currently, use of CM solutions
in vials is common in several countries.
If the vial is opened by removing the rubber to load the solution in the syringe,
a wide section of the CM solution is
exposed to the external environment.
This increases the risk of airborne
contamination (Figure 2). According to
manufacturers and health authorities, if
the solution is withdrawn by piercing
the rubber cap, it may be pierced only
once when multi-dosing containers
To secure high microbial safety standards for CM solution withdrawn into
a syringe from a container, it would be
useful to use a spike kit, or it would be useful to place a sterilizing disposable filter
(0.22 µm) onto the loading line. Furthermore, the solution should pass through
a three-way valve to further protect the
injection line from any potential risk of
contamination related to manipulation
of the loading tubing.
Some manufacturers offer injector
multi-detector computed tomography
(MDCT) devices, with supporting data,
as safe, with a low risk of contamination.
However, studies have also highlighted a
problem with MDCT devices as the non-return valves cannot guarantee sterility
and prevent cross contamination. 4, 5
The bottle-filled syringe system can
only preserve CM solution sterility when
withdrawn from the bottle. It cannot
guarantee sterility if the tubing and/or
valves are contaminated, and evidence
of this lack of sterility has been seen.
The presence of a one way valve aims
to prevent reflux caused by pump stops
and/or pressure fluctuations, making
it an efficient and reliable mechanical
safety device (Figure 3). It has not, however, been clearly demonstrated that the
valve can act as a biological barrier and
the debate is still ongoing. It should be
noted that contamination can originate
both from patient-to-patient pathogen
transmission and from operator-to-patient transmission. Only a program of
hygiene education and the adoption of
written procedures can solve this issue.
PFS Technology Considerations
The volume of iodinate CM commonly
administered in a CT examination is
about 100 mL in a single bolus, with a
flow rate of 2. 5–5 mL/s depending on
the type of examination. In this case,
the injection pressure can rise up to
300 PSI, especially if the solution is not
pre-warmed. It must be noted that, during CM solution injection, the highest
pressure does not act on the tubing walls
and the tubing is not the critical part.
Instead, as indicated by the Bernoulli
Contrast Media Vial
Figure 2 • Syringe loaded from a vial by removal of the rubber closure.