Edwin J. Baldelomar¹, Scott C. Beeman², Jennifer R. Charlton³, and Kevin M. Bennett^4
1Radiology, Washington University in St. Louis, St. Louis, MO, United States, ²Biomedical Engineering, Arizona State University, Tempe, AZ, United States, ³Pediatrics, University of Virginia, Charlottesville, VA, United States, ⁴Radiology, Washington University in St. Louis, Saint Louis, MO, United States

In this work, we use contrast agents cationic ferritin and gadolinium-DTPA (Gd-DTPA) to visualize dynamics of macromolecules and freely filtering particles in individual nephrons throughout entire perfused rat kidneys. Further, we also look at dynamics in kidneys that received a vasoconstriction agent, angiotension II (AngII). Voxel time courses were fitted with a bi-exponential model for each experiment (Experiment I, CF infusion and Experiment II, Gd-DTPA bolus). From fitting we assess CF uptake rates and measure single nephron glomerular filtration rate (snGFR). CF uptake rates and values of snGFR were mapped spatially and observed to be heterogeneously distributed throughout the kidney.

Joao Santos Periquito¹, Kathleen Cantow², Thomas Gladytz³, Bert Flemming², Dirk Grosenick³, Erdmann Seeliger², Thoralf Niendorf¹, and Andreas Pohlmann^1
1Max Delbrueck Center for Molecular Medicine, Berlin, Germany, ²Institute for Vegetative Physiology, Charité – Universitaetsmedizin Berlin, Berlin, Germany, ³Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany

The measurement of tubular volume fraction changes in the kidney may be valuable as a confounder of T₂*-derived tissue oxygenation and as a potential biomarker. Diffusion weighted imaging provides information about in-vivo water mobility which can be linked to three sources: tissue water diffusion, blood perfusion within intrarenal microvasculature, and tubular fluid. In this work we explore the feasibility of assessing tubular volume fraction changes using the non-negative least squares (NNLS) approach under different physiological conditions.

Soo Hyun Shin¹, Brandon Zhang¹, K. L. Barry Fung¹, Michael F. Wendland², and Moriel H. Vandsburger^1
1Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States, ²Berkeley Preclinical Imaging Core (BPIC),University of California, Berkeley, Berkeley, CA, United States

Urea recycling is a major component of renal tubular function and may provide an in vivo surrogate for tubular dysfunction in renal diseases. We demonstrate an approach of delayed urea differential enhancement CEST (dudeCEST)-MRI, which detects enhanced urea CEST contrast specific to the inner medulla and papilla of the mouse kidney at 20 minutes after urea injection. To enhance quantification while accounting for different T₁ values within the kidney, apparent exchange-dependent relaxation (AREX) correction was applied. The combination of dudeCEST with AREX analysis will be a useful platform for assessment of renal urea recycling as a surrogate for tubular dysfunction. 

Alexander J Daniel¹, Eleanor F Cox¹, Charlotte E Buchanan¹, and Susan T Francis^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom

Renal T₂ mapping is still in its infancy with little consensus on methodology between studies, this leads to a variation in T­₂ measurements between studies. Here four T₂ mapping methods (Spin Echo-Echo Planar Imaging (SE-EPI), Multi-Echo Turbo Spin Echo (ME-TSE), Gradient Spin Echo (GraSE), and Carr-Purcell-Meiboom-Gill T₂ preparation (T₂ prep)) are compared on both a calibrated phantom and in-vivo kidneys. The GraSE technique was found to produce the most accurate maps relative to the phantom and form the clearest maps of the kidneys in-vivo, showing clear differences between cortical and medullary tissues.

Fabio Nery¹, Charlotte Buchanan², Andrew Priest³, João Sousa⁴, Michael Nation⁵, Iosif Mendichovszky³, Steven Sourbron⁶, Susan Francis², and David Thomas^7,8,9
1UCL Great Ormond Street Institute of Child Health, London, United Kingdom, ²Sir Peter Mansfield Imaging Centre, University of Nottingham, University Park, Nottingham, United Kingdom, ³Department of Radiology, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom, ⁴Imaging Biomarkers Group, Department of Biomedical Imaging Sciences, University of Leeds, Leeds, United Kingdom, ⁵Kidney Research UK, Peterborough, United Kingdom, ⁶Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom, ⁷Neuroradiological Academic Unit, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom, ⁸Dementia Research Centre, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom, ⁹Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom

Multicentre validation studies are required to enable clinical translation of renal MRI biomarkers. Here, we report on the feasibility of standardising renal diffusion weighting imaging protocols and on the variability of renal apparent diffusion coefficient across a range of vendors. Results suggest feasibility of implementing near-identical renal diffusion weighted imaging acquisition protocols with product sequences and the potential of the apparent diffusion coefficient as a robust metric to characterise renal microstructure in multi-centre studies.

Florian Siedek¹, Franziska Grundmann², Kilian Weiss¹, Daniel Pinto dos Santos¹, Sita Arjune², Stefan Haneder¹, Thorsten Persigehl¹, Roman-Ulrich Mueller², and Bettina Baessler^1
1Radiology, University of Cologne, Cologne, Germany, ²Department II of Internal Medicine, University of Cologne, Cologne, Germany

Novel biomarkers for a more sensitive and quick assessment of ADPKD patients especially in those cases where kidney function is still preserved and can be maintained is urgently needed. We analyzed in 139 patients and 10 healthy controls if magnetic resonance T2 mapping of the kidneys allows a sufficient differentiation of cyst fraction as a surrogate marker for disease severity. The new biomarker parenchyma-T2 showed the strongest correlation to renal cyst fraction and was faster to determine than the established biomarker htTKV. Consequently, parenchyma-T2 has the potential to serve as a novel predictive biomarker especially in early stages of disease.  

Youzhen Feng¹, Zhongyuan Cheng¹, Xiaoqiao Chen², Xiaoqing Xiong¹, Qiting Lin¹, Dingkun SiTu¹, Long Qian³, Huomei Chen¹, and Xiangran Cai^1
1Medical Imaging Center, First Affiliated Hospital, Jinan University, Guangzhou, Guangdong, China, Guangzhou, China, ²Medical Imaging Center, The Eighth Hospital of Sun Yat-sen University，shenzhen，China., Shenzhen, China, ³MR Research, GE Healthcare., Beijing, China

Diffusional kurtosis imaging (DKI) is an advanced diffusion model and could identify the heterogeneity of cellularity and microstructural complexity. To test whether the DKI could detect the functional changes of kidney in early Diabetic kidney disease (DKD), the STZ-induced diabetic rats were applied in current study. Further, the biochemical and pathological evidences would also be provided to compare with the DKI biomarker.

Jing gang Zhang¹, Wei Xing¹, Jie Chen¹, and Weiqiang Dou^2
1Radiology, Third Affiliated Hospital of Soochow University, Changzhou, China, ²MR Research China, GE Healthcare, Shanghai, China

The purpose was to explore if T2’mapping can assess renal oxygen in the ischemia-reperfusion injury (IRI). IRI models were established according to different ischemia time, followed by injection of furosemide 24 hours after IRI and consecutive MRI scans. Quantitative scores of oxygen were acquired with the hypoxic probe. We found that R2’ values of the inner and outer medulla were statistically significant. R2’ value of the outer medulla was highly correlated with oxygen scores. T2’mapping could serve as a quantitative biomarker to assess the renal oxygen and monitor the treatment in patients with IRI.