Apparent diffusion coefficient measurements of bilateral kidneys at 3 T MRI: Effects of age, gender, and laterality in healthy adults

Multi-center and multi-vendor evaluation study across 1.5 T and 3 T scanners (part 1): apparent diffusion coefficient standardization in a diffusion MRI phantom

OBJECTIVE

To validate multi-site and multi-vendor ADC measurements using the QIBA/NIST diffusion MRI phantom at room temperature.

MATERIALS AND METHODS

ADC measurements were performed on 12 scanners (evenly split between 1.5 and 3 T) from three vendors at five sites and compared with reference values at room temperature. We adopted Pearson's correlation (r) and accuracy error for comparison with reference values; within scanner coefficient of variation (CVintra%) for intra-session repeatability and inter-scanner for agreement (CVinter%); Bland-Altman plots and precision error for short-term reproducibility; generalized linear mixed models and post-hoc tests ( α =0.05) to compare accuracy, repeatability and precision across field strengths, vendors, and scanners.

RESULTS

Temperature adjusted ADCs were well correlated with NIST reference values (r ≥ 0.997 for 1.5 T, r ≥ 0.996 for 3 T). Median accuracy error was lower than 5% for all scanners. In the renal physiologic range (ADC > 0.83 × 10-3 mm2/s), accuracy error was < 10% and CVintra < 2%. Across all scanners, good short-term reproducibility with limits of agreement < 10% and excellent agreement (median CVinter < 2%) were found.

DISCUSSION

Despite using abdominal receive coils and room temperature measurements, all quantitative parameters were within literature findings. High accuracy, repeatability and precision within the renal physiologic range support the feasibility of scanner evaluation using QIBA standardization process for diffusion measurements in renal studies.

The Influence of Anthropometric Factors on Renal mpMRI: Insights From Regional Analysis

BACKGROUND

Multiparametric MRI (mpMRI) provides detailed insights into renal function, but the impact of anthropometric factors on renal imaging is not fully understood.

PURPOSE

To investigate regional correlations between mpMRI parameters and age, body mass index (BMI), and body surface area (BSA).

STUDY TYPE

Prospective, cross-sectional observational study.

POPULATION

Twenty-nine healthy volunteers (44.5 ± 18.3 years, 18 females) without a history of renal disease.

FIELD STRENGTH/SEQUENCE

3-T, pseudo-continuous arterial spin labeling, multi-echo gradient-recalled echo, diffusion-weighted imaging, T1 and T2 mapping.

ASSESSMENT

Bilateral kidneys were segmented into nine concentric layers (outer cortex to inner regions) and nine equiangular sections (lower to upper pole). Key parameters (renal blood flow [RBF],R 2 * , apparent diffusion coefficient [ADC], T1 and T2 maps) were correlated with age, BMI, and BSA. Differences in parameters between age and BMI groups were also evaluated.

STATISTICAL TESTS

Spearman correlation, Mann-Whitney U test, and rank-biserial correlation coefficient for effect size. A P-value <0.05 was considered statistically significant.

RESULTS

RBF correlated negatively with age in all regions and BMI in inner layers and lower pole. ADC negatively correlated with BMI (significance was not reached in layers 2, 7, 8; P-value = 0.06-0.12) and BSA in layers 1-7. T1 negatively correlated with age in inner regions and lower medial pole. Significant positive correlations were found between age andR 2 * (outermost layer, upper pole), age and T2 (inner and cranial-caudal regions), as well as BMI and T2 (except upper pole; P-value = 0.06). Significant differences between age groups were observed for RBF (all regions),R 2 * (outermost and second innermost layers, central lateral region), T1 (innermost layer), and T2 (upper medial pole). Between BMI groups, ADC (middle layers, upper medial pole) and T2 (outermost and inner layers, lower pole to lateral region) differed significantly.

DATA CONCLUSION

Intrarenal variance of mpMRI parameters correlated with age, BMI, and BSA.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 1.

Diffusion-weighted Imaging of the Abdomen during a Single Breath-hold Using Simultaneous-multislice Echo-planar Imaging

PURPOSE

This multi-scanner study aimed to investigate the validity of single breath-hold (BH) diffusion-weighted imaging (DWI) using simultaneous-multislice (SMS) echo-planar imaging in multiple abdominal organs to enable faster acquisition and reliable quantification of apparent diffusion coefficient (ADC).

METHODS

SNR, geometric distortion (GD), and ADC in a phantom; the ADC in the liver, renal cortex, paraspinal muscle, spleen, and pancreas; and the signal intensity ratio of the portal vein-to-muscle (SIR_PV-M) in healthy volunteers were compared between BH- and respiratory-triggered (RT) DWI with b-values of 0 and 800 s/mm² in two different MRI scanners.

RESULTS

The phantom study showed that the SNR of BH-DWI was significantly lower than that of the RT-DWI (P < 0.05 for both scanners), whereas the GD and ADC of BH-DWI did not differ significantly from those of the RT-DWI (P = 0.09-0.60). In the volunteer study, the scan times were 23 seconds for BH-DWI and 184±33 seconds for RT-DWI, respectively. The ADC of the liver in BH-DWI was significantly lower than that in RT-DWI (P < 0.05 for both scanners), whereas there were no significant differences in the ADCs of the renal cortex, paraspinal muscle, spleen, or pancreas between BH-DWI and RT-DWI (P = 0.07-0.86). The SIR_PV-M in BH-DWI was significantly smaller than in RT-DWI (P < 0.05 for both scanners).

CONCLUSION

The proposed method enables the acquisition of abdominal diffusion-weighted images in a single BH.

Renal Diffusion-Weighted Imaging in Healthy Dogs: Reproducibility, Test-Retest Repeatability, and Selection of the Optimal b-value Combination

Diffusion-weighted imaging (DWI) magnetic resonance imaging can evaluate alterations in the microstructure of the kidney. The purpose of this study was to assess the apparent diffusion coefficient (ADC) and the intravoxel incoherent motion model (IVIM) parameters of a normal kidney in healthy dogs, to evaluate the effect of b-value combinations on the ADC value, and the reproducibility and test-retest repeatability in monoexponential and IVIM analysis. In this experimental study, the ADC, pure diffusion coefficient (D), pseudodiffusion coefficient (D^*), and perfusion fraction (f _p) were measured from both kidneys in nine healthy beagles using nine b-values (b = 0, 50, 70, 100, 150, 200, 500, 800, and 1,000 s/mm²) twice with a 1-week interval between measurements. Interobserver and intraobserver reproducibility, and test-retest repeatability of the measurements were calculated. ADC values were measured using 10 different b-value combinations consisting of three b-values each, and were compared to the ADC obtained from nine b-values. All the ADC, D, D^*, and f _p values measured from the renal cortex, medulla, and the entire kidney had excellent interobserver and intraobserver reproducibility, and test-retest repeatability. The ADC obtained from a b-value combination of 0, 100, and 800 s/mm² had the highest intraclass correlation coefficient with the ADC from nine b-values. The results of this study indicated that DWI MRI using multiple b-values is feasible for the measurement of ADC and IVIM parameters with high reproducibility and repeatability in the kidneys of healthy dogs. A combination of b = 0, 100, and 800 s/mm² can be used for ADC measurements when multiple b-values are not available in dogs.

Non-invasive evaluation of renal structure and function of healthy individuals with multiparametric MRI: Effects of sex and age

Clinically, when applying multiparametric magnetic resonance imaging (MRI) examinations in renal diseases, assessment of renal structure and function has to account for age- and sex-related effects. The aim of this study was to investigate the influence of age and sex on multiparametric MRI assessment of renal structure and function in healthy human beings. Studies on 33 healthy volunteers were performed using multiparametric MRI on a 3.0-Tesla MR scanner, including T1-weighted imaging, blood oxygen level-dependent MRI (BOLD MRI), diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI). Our results revealed that the mean renal cortical thickness (RCT), ratio of cortex to parenchyma (CPR), and cortical R2* values were higher in males than in females. The cortical R2* value was higher in older group than in younger group (18.57 ± 0.99 vs 17.53 ± 0.58, p = 0.001); there was no significant difference in medullary R2* between the older and younger groups (38.18 ± 2.96 vs 36.45 ± 2.47, p = 0.077). The parenchymal thickness (PT) and medullary fractional anisotropy (FA) were lower in older group than in younger group (1.547 ± 0.06 vs 1.604 ± 0.05, p = 0.005 and 0.343 ± 0.03 vs 0.371 ± 0.03, p = 0.016, respectively). Pearson's correlation analysis showed that PT and medullary FA were inversely related with age (r = -0.483, p = 0.004; r = -0.446, p = 0.009) while cortical R2* values was positively related (r = 0.511, p = 0.002, respectively). The medullary apparent diffusion coefficient (ADC) value had a significant association with PT (r = 0.359, p = 0.04). This study indicated that multiparametric renal MRI parameters are age and sex dependent.

Using magnetic resonance diffusion tensor imaging to evaluate renal function changes in diabetic patients with early-stage chronic kidney disease

AIM

To investigate the clinical value of diffusion tensor imaging (DTI) in assessing renal function changes in diabetic patients with early-stage chronic kidney disease (CKD), and the relationship of DTI parameters with estimated glomerular filtration rate (eGFR) and urinary biomarkers.

MATERIALS AND METHODS

Thirty-six patients with diabetes mellitus (DM; 30 CKD stage 1 and 6 CKD stage 2) and 26 healthy control subjects were enrolled. DTI was performed using a clinical 3 T MRI system. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were calculated from the renal cortex and medulla. The correlation of the DTI parameters with eGFR and urinary biomarkers was evaluated.

RESULTS

FA values were significantly reduced in the renal cortex and medulla of DM group compared with the control group (cortical FA, Z=-2.834, p=0.005; medullary FA, t=2.768, p=0.007). In the DM group, FA values in the renal cortex and medulla were positively correlated with eGFR, while FA values in the medulla were negatively correlated with the urinary albumin/creatinine ratio, urinary alpha-1 microglobulin/creatinine ratio, and urinary transferring/creatinine ratio. ADC values in the renal cortex and medulla showed a trend towards an increase in the DM group compared with the control group.

CONCLUSIONS

Renal DTI is a promising method for assessing early renal function changes in DM patients.

Simultaneous Multislice Diffusion-Weighted Imaging of the Kidney: A Systematic Analysis of Image Quality

OBJECTIVES

The aims of this study were to implement a protocol for simultaneous multislice (SMS) accelerated diffusion-weighted imaging (DWI) of the kidneys and to perform a systematic analysis of image quality of the data sets.

MATERIALS AND METHODS

Ten healthy subjects and 5 patients with renal masses underwent DWI of the kidney in this prospective institutional review board-approved study on a 3 T magnetic resonance scanner. Simultaneous multislice DWI echo-planar sequences (acceleration factors [AFs] 2 and 3) were compared with conventional echo-planar DWI as reference standard for each acquisition scheme. The following 3 acquisition schemes were applied: comparison A, with increased number of acquisitions at constant scan time; comparison B, with reduction of acquisition time; and comparison C, with increased slice resolution (constant acquisition time, increasing number of slices). Interreader reliability was analyzed by calculating the intraclass correlation coefficient (ICC). Qualitative image quality features were evaluated by 2 independent radiologists on a 5-point Likert scale. Quantification accuracy of the apparent diffusion coefficients (ADCs) and signal-to-noise ratios (SNRs) were assessed by region of interest analysis. Furthermore, lesion conspicuity in the 5 patients was assessed using a 5-point Likert scale by 2 independent radiologists.

RESULTS

Interreader agreement was substantial with an ICC of 0.68 for the overall image quality and an ICC of 0.73 for the analysis of artifacts. In comparison A, AF2 resulted in increased SNR (P < 0.05) by 21% at stable image quality scores (image quality: P = 0.76, artifacts: P = 0.21). In comparison B, applying AF2, the scan time could be reduced by 46% without significant reduction in qualitative image quality scores (P = 0.059) or SNR (P = 0.126). In comparison C, slice resolution could be improved by 28% using AF2 with stable image quality scores and SNR. In general, AF3 resulted in reduced image quality and SNR. Significantly reduced ADC values were observed for AF3 in comparison C (cortex: P = 0.003; medulla: P = 0.001) compared with the standard echo-planar imaging sequence. The conventional DWI and the SMS DWI with AF2 showed stable lesion conspicuity ([AF1/AF2]: reader 1 [1.8/1.4] and reader 2 [1.8/1.4]). The lesion conspicuity was lower using AF3 (reader 1: 2.2 and reader 2: 1.8).

CONCLUSIONS

In conclusion, SMS DWI of the kidney is a potential tool to substantially reduce scan time without negative effects on SNR, ADC quantification accuracy, and image quality if an AF2 is used. Although AF3 results in even higher scan time reduction, a negative impact on image quality, SNR, ADC quantification accuracy, and lesion conspicuity must be considered.

Evaluation of upper abdominal organs with DWI in patients with familial Mediterranean fever

PURPOSE

To investigate the diagnostic efficiency of diffusion-weighted magnetic resonance imaging (DWI) for the evaluation of functional changes that can occur in upper abdominal organs in patients with familial Mediterranean fever (FMF).

METHODS

The study included 50 controls, 45 patients with FMF, and 14 patients with FMF who had accompanying proteinuria. Measurement of apparent diffusion coefficient (ADC) was performed using DWI sections obtained from liver, spleen, kidney, and pancreas parenchyma with 1.5T MRI using b = 500 and b = 1000 s/mm² values both in patients and control groups. Mean ADC values were compared between patient and control groups.

RESULTS

Renal ADC values were lower in the patient groups compared to the control group. Additionally, renal ADC values showed further decrease in the patient group in the presence of accompanying proteinuria, when compared to the FMF group without proteinuria (p < 0.001). Based on the ROC analysis, calculated cutoff values for the determination of FMF and FMF accompanied by proteinuria were 2.26 × 10^-3 and 2.04 × 10^-3 mm²/s, respectively. Liver, spleen, and pancreas ADC values did not show remarkable change between patient and control groups.

CONCLUSION

Present findings indicate that the presence of FMF and its clinical progression expressed by proteinuria can be differentially determined with renal DWI.

Diffusion-weighted imaging outside the brain: Consensus statement from an ISMRM-sponsored workshop

The significant advances in magnetic resonance imaging (MRI) hardware and software, sequence design, and postprocessing methods have made diffusion-weighted imaging (DWI) an important part of body MRI protocols and have fueled extensive research on quantitative diffusion outside the brain, particularly in the oncologic setting. In this review, we summarize the most up-to-date information on DWI acquisition and clinical applications outside the brain, as discussed in an ISMRM-sponsored symposium held in April 2015. We first introduce recent advances in acquisition, processing, and quality control; then review scientific evidence in major organ systems; and finally describe future directions. J. Magn. Reson. Imaging 2016;44:521-540.