Quality assurance multicenter comparison of different MR scanners for quantitative diffusion-weighted imaging.

PURPOSE: To propose a magnetic resonance imaging (MRI) quality assurance procedure that can be used for multicenter comparison of different MR scanners for quantitative diffusion-weighted imaging (DWI). MATERIALS AND METHODS: Twenty-six centers (35 MR scanners with field strengths: 1T, 1.5T, and 3T) were enrolled in the study. Two different DWI acquisition series (b-value ranges 0-1000 and 0-3000 s/mm(2) , respectively) were performed for each MR scanner. All DWI acquisitions were performed by using a cylindrical doped water phantom. Mean apparent diffusion coefficient (ADC) values as well as ADC values along each of the three main orthogonal directions of the diffusion gradients (x, y, and z) were calculated. Short-term repeatability of ADC measurement was evaluated for 26 MR scanners. RESULTS: A good agreement was found between the nominal and measured mean ADC over all the centers. More than 80% of mean ADC measurements were within 5% from the nominal value, and the highest deviation and overall standard deviation were 9.3% and 3.5%, respectively. Short-term repeatability of ADC measurement was found <2.5% for all MR scanners. CONCLUSION: A specific and widely accepted protocol for quality controls in DWI is still lacking. The DWI quality assurance protocol proposed in this study can be applied in order to assess the reliability of DWI-derived indices before tackling single- as well as multicenter studies.

Diffusion tensor imaging and tractography of the kidneys: assessment of chronic parenchymal diseases.

OBJECTIVE: To assess renal dysfunction in chronic kidney diseases using diffusion tensor imaging (DTI). METHODS: Forty-seven patients with impaired renal function (study group) and 17 patients without renal diseases (control group) were examined using DTI sequences. Cortical and medullary regions of interest (ROIs) were located to obtain the corresponding values of the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA). The mean values of the ADC and FA, for each ROI site, were obtained in each group and were compared. Furthermore, the correlations between the diffusion parameters and the estimated glomerular filtration rate (eGFR) were determined. RESULTS: In both the normal and affected kidneys, we obtained the cortico-medullary difference of the ADC and the FA values. The FA value in the medulla was significantly lower (P = 0.0149) in patients with renal function impairment as compared to patients with normal renal function. A direct correlation between DTI parameters and the eGFR was not found. Tractography visualised disruption of the regular arrangement of the tracts in patient with renal function alteration. CONCLUSION: DTI could be a useful tool in the evaluation of chronic kidney disease and, in particular, the medullary FA value seems to be the main parameter for assessing renal damage. KEY POINTS: • Magnetic resonance diffusion tensor imaging (MRDTI) provides new information about renal problems. • DTI allows non-invasive repeatable evaluation of the renal parenchyma, without contrast media. • DTI could become useful in the management of chronic parenchymal disease. • DTI seems more appropriate for renal evaluation than diffusion-weighted imaging.