opTimization of timing Window for 18F-FDG PET/CT In patientS with suspecTED prosthetic heart valve endocarditis

Infective endocarditis (IE) is a serious complication of heart valve
replacement and has been reported in 1%-6% of patients with valve prostheses
within 5 years of implantation. It remains associated with a high mortality
rate. Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission/computed
tomography (PET/CT) imaging was introduced as an additional diagnostic tool in
the most recent European Society of Cardiology (ESC) guidelines on infective
endocarditis and a positive study should be considered a major criterion in
diagnosis. 18F-FDG PET/CT is increasingly utilized for establishment of
diagnosis of IE, especially in difficult and equivocal cases. The standard
PET/CT imaging protocol which is mainly used for oncological imaging starts 60
minutes post-FDG injection. This allows the FDG to distribute within the body
and be taken up by tumour cells. The optimal imaging time after FDG injection
in infectious-in*ammatory disease (including endocarditis) is not clear yet and
may be different. Either earlier or delayed imaging may be beneficial because
infected or inflamed tissue may take up FDG faster or slower, respectively.
Also, dynamic PET-CT imaging (i.e. imaging acquisition during a longer period
of time) may provide information on FDG kinetics in infection and inflammation,
which is crucial in defining the optimal acquisition time point(s) for PET/CT
in patients with (suspected) IE.
Furthermore, cardiac and respiratory motion results in blurring of the PET
images. Cardiac and respiratory gated PET image acquisition (using only image
data obtained during pre-specified parts of the cardiac cycle and respiratory
phase) may result in improved image quality.
There are very limited data available in the literature on the above mentioned
aspects of PET/CT imaging in IE.

Primary objectives of the study are:
1. Defining the optimal image acquisition time window after FDG injection for
PET/CT imaging in patients suspected of endocarditis
2. Assessing the impact of gating (respiratory and ECG) on PET/CT image quality
in patients suspected of endocarditis

Prospective pilot study.

Risk: The proposed PET/CT acquisition protocol is built around the standard
PET/CT acquisition protocol, which includes 18F-FDG injection, followed by
performing whole-body PET/CT at 1 hour after injection. These procedures are
clinically indicated and cause the main radiation exposure of the patient.
The individual patient burden consists of 2 additional low-dose CT scans of the
cardiac area (used for attenuation correction) and a longer period of time (1,5
hours) in the PET-CT scanner. The additional PET images that are acquired do
not expose the patient to additional radiation since the FDG (which is the
source of the radiation used for PET imaging) is injected in the patient and as
such the patient itself is the source of radiation.
The main risk, associated with participation in the study is the additional
radiation dose to the patient from the two additional low-dose CTs of cardiac
area which is estimated to be 1.34 millisievert (mSv). The mentioned radiation
dose is lower than the annual natural background radiation. Please find
attached a report of radiation safety committee.

Benefit for the individual patient:
Whole-body PET/CT is performed in patients suspected of IE as a part of
standard clinical care.
It is not known whether the proposed acquisition protocol leads to better
diagnostic accuracy of this imaging tool, but taking part in the current study
will contribute to the future use of PET/CT as a diagnostic tool in the field
of suspected PVE.

Group related benefit:
The benefit from the gathered data may cause changes in existing PET/CT
acquisition protocols in the field of infection and inflammation. Better and
earlier detection of IE will be of added value in the future evaluation all
FDG-PET studies performed in patients with (suspected) prosthetic heart valve
endocarditis.*