Table 2.

Interpretation of contrast-enhanced CT scans acquired alongside PET/CT imaging in 4Is

Disease	Contrast application	Advantages and scoring methods	Comments
Infective endocarditis and cardiac device infection	++	-Visualization of abscesses -Visualization of thrombi/vegetation on valves/probes -Visualization of septic embolism as infarcts in terminal vessels (e.g., spleen, kidney, brain) -Detailed examination of valves (potentially important in surgical procedures)	Some imaging centers do not deem the administration of contrast medium to be mandatory.
Cardiac sarcoidosis	±	Superior morphological allocation of the PET signal (e.g. myocardial vs. lung uptake; organ involvement)	Contrast agent generally not required if perfusion study (PET and SPECT) is available
Large vessel vasculitis	++	Visualization of the vessels to exclude relevant stenosis and score wall thickness: 0 = no mural thickening 1 = slight mural thickening 2 = mural thickening 3 = long and strong circumferential mural thickening OR as measurement: >2–3 mm	In the presence of a recent angiographic scan (CT/MRT), a low-dose CT is sufficient.
Atherosclerosis	+++	Visualization and quantification of calcium, vascular stenosis and plaque composition -Agatston score in mainly applied for calcium burden and risk assessment in coronary artery disease -Vascular stenosis is evaluated on CTA and categorized as non-obstructive or obstructive	CTA is clinically recommended and aids in the interpretation of the PET scans particularly in the coronary arteries
Vascular graft infection	+++	-Visualization of peri-graft gas and fluid. -Aneurysm expansion/pseudo-aneurysm formation -Detailed examination of vascular graft	The sensitivity and specificity of CT is moderate and variable
Cardiac amyloidosis	–	Assessment of thickness of the left ventricular myocardium	Only patients with a clinical suspicion receive this specific examination (septum thickness usually already available).

^-no contribution, ^±some contribution, ⁺⁺good contribution, ⁺⁺⁺excellent contribution