Diffusion tensor imaging of the kidney with parallel imaging: initial clinical experience.
OBJECTIVE
To evaluate the clinical feasibility of diffusion tensor imaging (DTI) of the kidney in volunteers and patients with renal diseases.


METHODS
Ten volunteers and 22 patients (mean age, 56 +/- 14.3) with renal masses and renal artery stenosis underwent breath-hold coronal fat-saturated echo-planar DTI (as provided by the manufacturer, 6 diffusion directions, diffusion weightings b = 0 and 300 s/mm2, repetition time 730 ms/echo time 72 ms; 5 slices; slice thickness, 6 mm; inplane resolution, 2.1 x 2.1 mm2; acquisition time, 26 seconds) of the kidneys at 1.5 T (MAGNETOM Avanto, Siemens Medical Solutions, Erlangen, Germany). The parallel imaging technique, generalized autocalibrating partially parallel acquisitions with an acceleration factor 2, was applied. Using the commercially available Syngo DTI task card software, regions of interests were placed in the cortex, medulla, and in renal masses if present. Fractional anisotropy (FA) and apparent diffusion coefficients (ADC) were determined, and tractography was used to visualize the renal diffusion properties. Statistical analysis was performed using the Wilcoxon signed-rank sum test and paired t tests.


RESULTS
In all volunteers, FA was significantly (P < 0.01) higher in the medulla (0.36 +/- 0.03) than in the cortex (0.21 +/- 0.02), whereas the ADC was significantly (P < 0.01) higher in the cortex (2.43 +/- 0.19) than in the medulla (2.16 +/- 0.22). Tractography typically revealed a radial preferred direction of medullary diffusion basically reflecting medullary flow.FA/ADC of simple renal cysts (n = 8) was 0.14 +/- 0.05/2.86 +/- 0.15. Renal cell carcinoma (n = 10) showed a wide FA range from 0.11 to 0.56. Using tractography, the structural organization of renal cell carcinoma such as pseudocapsules could be visualized.In 1 patient with unilateral high-grade renal artery stenosis, the cortical ADC of the affected kidney was lower than on the contralateral side (1.77/2.27) and the FA was increased (0.33/0.18). The FA of the medulla was increased (0.70/0.41) and the ADC decreased (1.43/1.90).


CONCLUSIONS
Using parallel imaging, DTI measurements of the kidneys are feasible within a single breath-hold with good discrimination between cortex and medulla. Parallel imaging allows more slices and a superior resolution. DTI measurements of the kidney allows visualization of medullary flow, in pathology ADC and FA were altered. Further investigations will be required to evaluate the role of DTI for studying and monitoring renal ultrastructure.
Notohamiprodjo
Mike
M
Department of Clinical Radiology, University Hospitals Munich, Campus Grosshadern, Munich, Germany. mike.notohamiprodjo@med.uni-muenchen.de
Glaser
Christian
C
Herrmann
Karin A
KA
Dietrich
Olaf
O
Attenberger
Ulrike I
UI
Reiser
Maximilian F
MF
Schoenberg
Stefan O
SO
Michaely
Henrik J
HJ
D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000473:pathology; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology*; D007672:Kidney Cortex / Q000473:pathology; D007674:Kidney Diseases / Q000175:diagnosis* / Q000473:pathology; D007679:Kidney Medulla / Q000473:pathology; D008297:Male; D008875:Middle Aged