Keywords:
Embolism / Thrombosis, Contrast agent-intravenous, CT-Angiography, Pulmonary vessels
Authors:
A. S. Menon, J. A. Abdulkarim; Nuneaton/UK
DOI:
10.1594/ecr2018/C-1402
Conclusion
Various past literature have reported on the use of a smaller dose of contrast media in CTPA.
In one study [3],
the feasibility of using a reduced dose of contrast material(75ml) delivered in a higher concentration (350mg iodine/ml Ioversol) compared to the conventional 100ml of 300mg iodine/ml Ioversol was assessed and successfully established.
This finding was also reported in a Randomised Clinical Trial published in the same year [4],
which further established the use of a lower energy tube (80kVp vs 100kVp) for a reduced dose of radiation.
In a different single cohort study [5],
the authors have evaluated the practicality of CTPA with 30ml of contrast medium in patients with renal impairment.
Although it was stated that only one out of 24 scans were nondiagnostic,
the reported average opacification (247HU) in the main pulmonary arteries is below the 250HU threshold that we have used.
The risk of CI-AKI is low in the general population (<2%) but can be as high as 10-40%in selected patient groups with certain risk factors (diabetes,
cardiac failure,
pre-existing renal impairment,
older age and recent exposure to nephrotoxic drugs) [2].
However,,these patients are equally,
if not more,
likely to be at a risk of developing PE.
Since the risk of CI-AKI is known to be dose-dependent [6],
it is desirable to use as small an amount of contrast medium as possible.
Our study utilised a lower dose (45ml) of contrast agent compared to the normal dose (60ml) currently used in clinical practice at our Trust.
The experimental results have shown that a reduction in contrast agent dose can be achieved without adversely affecting pulmonary arterial enhancement in CTPA.
There was a positive correlation with increasing pulmonary artery enhancement with increasing patient’s age (graph1).
This may be attributed to less efficient heart with advancing age thus allowing more time for the contrast to be in the pulmonary circulation.
To conclude reduced dose CTPA can be used for patients,
particularly in the elderly,
who are at greater risk of CI-AKI.Use caution when considering this technique in younger patients.