Future Direction of Renal Positron Emission Tomography

Abstract

Positron emission tomography (PET) is perfectly suited for quantitative imaging of the kidneys, and the recent improvements in detector technology, computer hardware, and image processing software add to its appeal. Multiple positron emitting radioisotopes can be used for renal imaging. Some, including carbon-11, nitrogen-13, and oxygen-15, can be used at institutions with an on-site cyclotron. Other radioisotopes that may be even more useful in a clinical setting are those that either can be obtained from radionuclide generators (rubidium-82, copper-62) or have a sufficiently long half-life for transportation (fluorine-18). The clinical use of functional renal PET studies (blood flow, glomerular filtration rate) has been slow, in part because of the success of concurrent technologies, including single-photon emission computed tomography (SPECT) and planar gamma camera imaging. Renal blood flow studies can be performed with O-15-labeled water, N-13-labeled ammonia, rubidium-82, and copper-labeled PTSM. With these tracers, renal blood flow can be quantified using a modified microsphere kinetic model. Glomerular filtration can be imaged and quantified with gallium-68 EDTA or cobalt-55 EDTA. Measurements of renal blood flow with PET have potential applications in renovascular disease, in transplant rejection or acute tubular necrosis, in drug-induced nephropathies, ureteral obstruction, before and after revascularization, and before and after the placement of ureteral stents. The most important clinical application for imaging glomerular function with PET would be renovascular hypertension. Molecular imaging of the kidneys with PET is rather limited. At present, research is focused on the investigation of metabolism (acetate), membrane transporters (organic cation and anion transporters, pepT1 and pepT2, GLUT, SGLT), enzymes (ACE), and receptors (AT1R). Because many nephrological and urological disorders are initiated at the molecular and organelle levels and may remain localized at their origin for an extended period of time, new disease-specific molecular probes for PET studies of the kidneys need to be developed. Future applications of molecular renal imaging are likely to involve studies of tissue hypoxia and apoptosis in renovascular renal disease, renal cancer, and obstructive nephropathy, monitoring the molecular signatures of atherosclerotic plaques, measuring endothelial dysfunction and response to balloon revascularization and restenosis, molecular assessment of the nephrotoxic effects of cyclosporine, anticancer drugs, and radiation therapy. New radioligands will enhance the staging and follow-up of renal and prostate cancer. Methods will be developed for investigation of the kinetics of drug-delivery systems and delivery and deposition of prodrugs, reporter gene technology, delivery of gene therapy (nuclear and mitochondrial), assessment of the delivery of cellular, viral, and nonviral vectors (liposomes, polycations, fusion proteins, electroporation, hematopoietic stems cells). Of particular importance ...

68Ga-EDTA PET/CT Imaging and Plasma Clearance for Glomerular Filtration Rate Quantification: Comparison to Conventional 51Cr-EDTA

“…68 Ga-EDTA PET/CT also has the potential to replace 99m Tc-DTPA renography, including for evaluation of renal tract obstruction given its 3-dimensional dynamic capability, although MAG-3 remains the agent of choice as it is predominantly secreted (31). The short half-life of 68 Ga also makes it ideal for renography before and after angiotensin-converting enzyme inhibition to assess for hemodynamically significant renal artery stenosis (32).…”

Measurement of kidney perfusion in critically ill Patients

“…This method has been used in animal models of renal artery obstruction, occlusion and reperfusion [39]. The second technique makes use of ultra-short-lived tracers, such as oxygen-15-labelled water (half-life of 2 min) [40]. This compound was studied by Juillard et al [41], who showed an excellent correlation with microsphere techniques in an animal model and by Alpert et al [42], who used O-15 water to measure renal blood flow in healthy volunteers.…”

“…This compound was studied by Juillard et al [41], who showed an excellent correlation with microsphere techniques in an animal model and by Alpert et al [42], who used O-15 water to measure renal blood flow in healthy volunteers. Other potential applications include measurements of renal blood flow in renovascular disease, in rejection or in acute tubular necrosis of transplanted organs, in drug-induced nephropathies, ureteral obstruction before and after revascularization and before and after placement of ureteral stents [40]. …”

Measurement of Kidney Perfusion in Critically Ill Patients

“…Th is method has be en used in animal models of renal artery obstruction, occlusion and reperfusion [39]. Th e second techniq ue makes use of ultrashort-lived tracers, such as oxygen-15-label led water (half-life of 2 min) [40]. Th is compound was s tudied by Juillard et al [41], who showed an excell ent correlation with microsphere techniques in an animal model and by Alpert et al [42], who used O-15 water t o measure renal blood fl ow in healthy volunteers.…”

“…Th is compound was s tudied by Juillard et al [41], who showed an excell ent correlation with microsphere techniques in an animal model and by Alpert et al [42], who used O-15 water t o measure renal blood fl ow in healthy volunteers. Other potential applications include measurements of renal blood fl ow in renovascular disease, in rejection or in acute tubular necrosis of transplanted organs, in drug-induced nephropathies, ure teral obstruction before and after revascularization and before and after placement of ureteral stents [40].…”