Table 2.

Head-to-head comparison of different image modalities for assessing renal function.

Imaging Modality	MRI	CT	Ultrasound	PET
Advantages	Allows for precise tissue differentiation 88 Can examine various physiologic aspects of renal function (perfusion, glomerular filtration, interstitial diffusion, tissue oxygenation, tubular transit) 88 MR renography can reliably diagnose renovascular hypertension, urinary obstruction or renal transplant complications 88 Assessment of split-renal function 89 Better arterial input functions and separation in duplicate kidneys relative to PET 89 Can compensate motion (kidneys are prone to motion artefacts given their anatomical localization under the diaphragm) 89	Widely available Various clinical applications, including staging/restaging, obstruction (kidney stones, polycystic kidney disease) Localizing of abscesses Preoperative planning prior to partial nephrectomy 89	Virtually available at every hospital 90 Low costs 90 No need for intravenous iodine contrast adminis-tration 90 Fast read-out of kidneys and adjacent organs, e.g. for renal cyst evaluation	Large variety of renal function can be assessed, e.g. GFR, ERPF, inflammation, RBF or renal PSMA expression 3-dimensional read-out capabilities Assessment of split-renal function 1mSv radiation exposure 89 No pharmalogical effects 89 Can be used in a theranostic setting, e.g, for RCC or to assess organ-organ interactions
Disadvantages	Confined space and loud noises leading to patient discomfort Certain devices, such as pacemakers, are harmful Risk of nephrogenic systemic fibrosis with MRI contrast agents 91 Spatial resolution is limited as only multiple 2D slices are provided 89	Life-threatening contrast-induced nephropathy with CT contrast agents 91 Anaphylactoid reactions CT contrast media may lead to drug-drug interactions, e.g. increasing the retention of metformin leading to lactic acidosis 91 Radiation exposure (up to 8 mSv) 89	Spatial resolution is limited with single 2D slices 89 Does not provide detailed functional information	PET radionuclides emit all the same energy photons at 511keV and therefore, it is not feasible to use multiple PET tracers at the same time 89 No larger clinical trials to date No FDA approval to date for PET radiotracers evaluating renal function

MRI: magnetic resonance imaging, CT: computed tomography, PET: positron emission tomography, GFR: glomerular filtration rate, ERPF: ERPF: effective renal plasma flow, PSMA: prostate-specific membrane antigen, FDA: Food and Drug Administration.