title: Morphologic and dynamic renal imaging with assessment of glomerular filtration rate in a pcy-mouse model using a clinical 3.0 Tesla scanner.
abstract: OBJECTIVE Morphologic and dynamic renal imaging is necessary for characterization of kidney function in renal insufficiency. Assessment of renal perfusion and the glomerular filtration rate (GFR) are essential, as the serum creatinine level and urea are not sensitive at an early stage of kidney damage. Currently available GFR estimation methods are time consuming, expensive, and lead to radiation exposure for the patient. Therefore, the aim was to determine the feasibility of morphologic and contrast-enhanced dynamic magnetic resonance imaging for GFR assessment in pcy (polycystic kidneys and fibrosis) mice, using a clinical 3.0 Tesla scanner.
  
  
  METHODS
  Fourteen pcy-mice were anesthetized and an internal jugular vein catheter was implanted to which a dedicated extension tube with a 0.28 mm inner diameter was connected, filled with 1:100 microL diluted gadobutrol (Gadovist Bayer Schering Pharma, Berlin, Germany). Imaging of the mice was performed with a dedicated 8-element mouse coil (Rapid Biomedical, Rimpar, Germany) plugged into a clinical 32-channel 3.0 Tesla magnetic resonance-scanner (Magnetom Verio, Siemens Medical Solution, Erlangen, Germany). In this study, different morphologic sequences comprising a T1-w 3D volume-interpolated breathhold examination, T2-w 2D half-Fourier acquired turbo spin echo (HASTE), T2-w 2D BLADE-TSE with fat saturation, and a T2-w 3D SPACE were acquired. The dynamic sequence performed for assessment of GFR, was a 2D SR-Turbo FLASH sequence. Image analysis and data assessment was performed by 2 radiologists who were experienced in assessment of human kidney disease. A 3-point scale for visual assessment of renal cystic changes in the pcy-mice was applied. The appearance of cysts, considering a detailed demarcation of the cyst with an enhancing rim and a hypointense core, were assessed as detailed: (1) faint (2) and not to be differentiated, (3) findings in the morphologic sequences. Quantitative parameters of renal function (cortex plasma flow mL/100 mL/min, cortex plasma volume mL/100 mL, and PT sec) were fitted to a 2-compartment model and compared with blood samples of creatinine and urea. Histologic progression of cysts and fibrosis in the pcy-mice was analyzed.
  
  
  RESULTS
  The T2-w 3D SPACE and T1-w 3D volume-interpolated breathhold examination sequence post contrast with thinnest slice thickness of 1 to 1.2 mm were well suited for delineation of the kidneys with detailed demarcation of the cysts (image quality score: 1.14 +/- 0.37 and 1.2 +/- 0.70, respectively). The T2-w 2D BLADE-TSE proved feasible, too (image quality score: 1.28 +/- 0.59). The T2-w 2D HASTE sequence with minimally achievable slice thickness of 2 mm was not suitable for morphologic assessment (image quality score: 2.9 +/- 0.37). The HASTE sequence suffered from blurring artifacts which further decreased the conspicuity of small cystic changes. The 2D SR-Turbo FLASH sequence showed the renal first pass of the contrast agent and enabled assessment of GFR. The data after time resolved 2D SR-Turbo FLASH perfusion analysis was used for GFR evaluation and demonstrated better GFR values in the young pcy-mice (0.558 mL/min) compared with the older pcy-mice (0.066 mL/min).
  
  
  CONCLUSIONS
  Application of dedicated coils with a clinical 3.0 Tesla magnetic resonance-scanner have proved feasible for morphologic and dynamic renal imaging with assessment of GFR in pcy-mice.
authors.affiliation: Institute of Clinical Radiology and Nuclear Medicine, University Hospital Mannheim, University of Heidelberg, Mannheim, Germany. maliha.sadick@rad.ma.uni-heidelberg.de
authors.forename: Maliha
authors.initials: M
authors.lastname: Sadick
authors.forename: Daniel
authors.initials: D
authors.lastname: Schock
authors.forename: Bettina
authors.initials: B
authors.lastname: Kraenzlin
authors.forename: Norbert
authors.initials: N
authors.lastname: Gretz
authors.forename: Stefan O
authors.initials: SO
authors.lastname: Schoenberg
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Michaely
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D007690:Polycystic Kidney Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity