Evaluating image quality in coronary angiography using diluted contrast agent

Cardiac procedures like coronary angiography (CAG) and percutaneous
intervention (PCI) rely on the use of iodinated intravascular contrast for
vessel and chamber imaging.
Contrast induced nephropathy (CIN) or contrast induced acute kidney injury
(CI-AKI) occurs in 0-25% of patients undergoing CAG or PCI [1]. A subgroup of
patients is at risk for this complication, depending of risk factors in which
pre-procedure renal function is the most important. Outcomes for these patients
may be severe; rehospitalisation, dialysis, renal replacement therapy and
death. A reduction of administered iodine for these patients could lead to a
reduction of complications associated with CI-AKI. Dilution of the contrast
agent is a possibility to reach this reduction.

The purpose of this study is to evaluate image quality by comparing images
acquired using diluted contrast agent and adapted x-ray scan protocols to
images of standard x-ray runs of a CAG procedure in the current clinical
settings

We will perform a single center study, in which patient-x-ray runs obtained
using different degrees of diluted contrast agents and adapted x-ray settings
will be intra-individually compared.
Patient selection will be performed by Isala Heart Centre. Patients that meet
the inclusion criteria, not excluded by the exclusion criteria and have signed
informed consent will undergo a normal clinical CAG procedure. For the purpose
of this study, three extra cine runs are performed with diluted contrast agent
and adapted x-ray settings. There will be randomization for the side (left or
right) for the four extra runs and for the order of the different research runs.
One investigator will analyse the runs quantitatively, while three
cardiologists will give qualitative (visual) judgments.

Additional amount of contrast agent
For the study, approximately 45 ml of contrast agent will be added to the
amount of 120 ml on average (15 ml per run on average, in clinical routine
eight runs are performed and three extra runs are performed for this study).
Because of the dilution of the contrast agent, the iodine load for the patient
raises with approximately 24% compared to the normal procedure.

The extra burden due to the contrast agents for the patient participating in
this study is relatively low. Due to the inclusion and exclusion criteria used
in this study, the 30% increase in administered iodine is unlikely to cause any
renal damage.
In figure 2 of reference article 7 of the study protocol, it is shown that, for
nondiabetic patients with a normal basal creatinine clearance, the expected
creatinine change due to the extra contrast administration, is negligible. So,
in the study population, no harm due to the extra administration of contrast
agent is expected. Furthermore there is a relatively low risk for side effects
and other issues for patients participating in this study.

Additional radiation dose
Derived from the clinical procedure, the value of the dose area product of a
cine run is approximately 0,45 Gy.cm2. The total dose for a clinical CAG
procedure is approximately 21,2 Gy.cm2. The four extra research runs, of which
two are performed with a doubled dose, cause an increase in dose of 3 Gy.cm2.
For calculating the effective dose, a conversion factor of 0,30 mSvGy-1cm-2 can
be used 9. The increase in effective dose due to the research runs, two of
which have a doubled dose, is approximately 0,91 mSv and this means a relative
increase of 14,1%.

According to the international commission on radiological protection (ICRP) the
additional radiation dose as a result of the research runs should be
categorised as IIA.
For this category ICRP states that acquisition of knowledge, resulting in
health benefit should be obtained by a study. In this study the health benefit
that is aimed for, is the decrease in kidney damage due to a reduction of
administered contrast agents for patients with deteriorated renal function.