Diffusion tensor MRI of the human kidney

Abstract

This study characterizes the diffusion anisotropy of the human kidney using a diffusion-weighted, single-shot echo planar imaging (EPI) sequence in order to access the full apparent diffusion tensor (ADT) within one breathhold. The fractional anisotropy (FA) of the cortex and the medulla were found to be 0.22 ؎ 0.12 and 0.39 ؎ 0.11, respectively (N ‫؍‬ 10), which emphasizes the need for rotationally invariant diffusion measurements for clinical applications. Additional limitations for clinical diffusion imaging on the kidney are the strong susceptibility variations within the abdomen that restrict the use of imaging techniques employing long echo trains, and the severe motion sensitivity that limits the available imaging time to one breath-hold. To overcome these problems an isotropic, diffusion-weighted, segmented EPI protocol that facilitates the acquisition of high-resolution diffusion-weighted images within a single breath-hold was implemented. Using this method, the apparent diffusion coefficient (ADC) of the cortex and medulla were found to be 2. 89 Index terms: diffusion; magnetic resonance imaging; kidney; EPI; fractional anisotropy WATER TRANSPORT is the predominant phenomenon throughout the kidney due to the kidney's major role in water reabsorption and concentration-dilution functions. These movements are mainly located in the tubular cells and are controlled either by active or passive mechanisms, depending on their location in the nephrons. Consequently, the measurement of the diffusion characteristics of the kidney may provide useful insights into the mechanisms of various renal diseases, including chronic renal failure, renal artery stenosis, and uretral obstruction. However, renal diffusion imaging is very challenging due to the extreme motion sensitivity of diffusion-weighted sequences, and the clinical use of this technique has been hampered by both the severe motion artifacts caused by arterial pulsations and respiratory motion. Diffusion-weighted single-shot-EPI (DW-SSEPI) (1), in conjunction with single breath-hold imaging (2-6) and peripheral pulse unit (PPU) triggering, (7) has been suggested as a possible means of overcoming these problems. However, the restriction of the diffusion experiment to a single breathhold limits the possible spatial resolution and the precision of the diffusion measurement (the number of directions for the diffusion weighting, the number of b-values, and the number of averages). As a result, most studies in the literature have measured the ADC in only one direction (2,4 -7), and hence have implicitly assumed that the diffusion characteristics of the kidney are isotropic. Hydration has been shown to increase global ADC values (3), while renal artery stenosis or ureteral obstruction decreased the values (2,3). In cases of acute or chronic renal failure, the cortical and medullary ADC values were significantly lower than in normal kidneys, and the cortical values were highly correlated with the serum creatinine levels (2).Although some studies have implied that t...

Diffusion‐weighted magnetic resonance imaging with apparent diffusion coefficient (ADC) determination in normal and pathological fetal kidneys

“…This quick sequence can be done during maternal breath holding and can be repeated two or three times until the ADC measurement is obtained. When these technical difficulties have been overcome, Cova et al 17 Adults (n = 10) 1.72 to 2.65 Siegel et al 18 Adults (n = 20) 1.79 to 2.95 Namimoto et al 11 Adults (n = 34) 2.55 (cortex) to 2.84 (medulla) Chow et al 12 Adults (n = 12) 2.58 (cortex) to 2.09 (medulla) Ries et al 13 Adults (n = 10) 2.89 (cortex) to 2.18 (medulla) Jones and Grattan-Smith 8 Children (n = 62) (range, 1 week to 18 years) 1.3 to 2.4 increase with age Witzani et al 7 Fetuses (n = 107) (range, 17-36 weeks) 0.74 to 1.65 Our study Fetuses (n = 50) (range, 23-38 weeks) 1.1 to 1.8 ADC measurements are useful for comparing the twins. The ADC of the donor twin was higher than that of the recipient twin and the difference seemed to be in relation to the severity of the syndrome in our cases.…”

Diagnostic value of diffusion weighted MRI and ADC in differential diagnosis of cavernous hemangioma of the liver

“…DWI is a technique that can be obtained within the time of a single held breath, without requiring contrast material and was originally used in neuroradiology for early diagnosis of stroke [3][4][5] . In the literature, there have been published papers on the application of DWI to abdominal organs [6][7][8][9][10][11][12][13] . These studies calculated the apparent diffusion coefficient of tissue and lesions from diffusion weighted images and have shown that the technique could be used for the differential diagnosis.…”

Diffusion tensor imaging of kidneys with respiratory triggering: Optimization of parameters to demonstrate anisotropic structures on fraction anisotropy maps

“…Most of the protocols use diffusion gradients in three orthogonal directions that are subsequently averaged to minimize the effect of anisotropy. However, considering the radially oriented tubular structure of the kidneys, averaging multiple gradients might also decrease information on anisotropic structures, as suggested by previous studies (3)(4)(5)(6).…”