Implementation of Dual-Source RF Excitation in 3 T MR-Scanners Allows for Nearly Identical ADC Values Compared to 1.5 T MR Scanners in the Abdomen

Background: To retrospectively and prospectively compare abdominal apparent diffusion coefficient (ADC) values obtained within in a 1.5 T system and 3 T systems with and without dual-source parallel RF excitation techniques. Methodology/Principal Findings: After IRB approval, diffusion-weighted (DW) images of the abdomen were obtained on three different MR systems (1.5 T, a first generation 3 T, and a second generation 3 T which incorporates dual-source parallel RF excitation) on 150 patients retrospectively and 19 volunteers (57 examinations total) prospectively. Seven regions of interest (ROI) were throughout the abdomen were selected to measure the ADC. Statistical analysis included independent two-sided t-tests, Mann-Whitney U tests and correlation analysis. In the DW images of the abdomen, mean ADC values were nearly identical with nonsignificant differences when comparing the 1.5 T and second generation 3 T systems in all seven anatomical regions in the patient population and six of the seven in the volunteer population (p.0.05 in all distributions). The strength of correlation measured in the volunteer population between the two scanners in the kidneys ranged from r = 0.64–0.88 and in the remaining regions (besides the spleen), r.0.85. In the patient population the first generation 3 T scanner had different mean ADC values with significant differences (p,0.05) compared to the other two scanners in each of the seven distributions. In the volunteer population, the kidneys shared similar ADC mean values in comparison to the other two scanners with nonsignificant differences

Imaging parameters in the three imaging systems used for the volunteer population.

<p>Imaging parameters in the three imaging systems used for the volunteer population.</p

Mean ADC values (×10⁻³ mm²/s) in the volunteer population.

<p>ADC values in bold are significantly different (p<0.05) from the other two values in the same distribution. ADC values with an asterisk are significantly different from each other. There are no significant differences (p≥0.05) between mean ADC values between two values that are not bolded or have an asterisk. The deeper regions, which are susceptible to B₁ inhomogeneity artifacts, are listed in rows 1–3.</p

Comparison of renal ADC-values between all three MR-scanners.

<p>Bland-Altman plot of mean ADC values from the right kidney comparing the 1.5 T system with the (A) first generation 3 T and (B) second generation 3 T MR-scanners in the volunteer population. The mean ADC values are similar amongst all three systems. (x-axis: average/y-axis: difference of ADC at 1.5 T and the corresponding 3 T systems (×10-3 mm³/s)).</p

Representative source data from all three MR-scanners.

<p>Representative source data images taken from the 1.5 T MR scanner (A), the first generation 3 T MR-scanner (B) and the second-generation 3 T MR-scanner (C) show that the second-generation 3 T MR-scanner yields higher signal to noise ratio throughout all b-values which is particularly well appreciated at the higher b-values.</p

Imaging parameters in the three imaging systems used for the patient population.

<p>Imaging parameters in the three imaging systems used for the patient population.</p

Correlation coefficients (r) of mean ADC values between the three systems.

<p>Values of r>0.7 are bolded to illustrate strong correlation, while values that have low correlation (<0.5) are italicized. The deeper regions, which are susceptible to B₁ inhomogeneity artifacts, are shaded in gray.</p

Mean ADC values (×10⁻³ mm²/s) in the patient population.

<p>ADC values in bold are significantly different (p<0.05) from the other two values in the same distribution. There are no significant differences (p≥0.05) between mean ADC values between two values that are not bolded. The deeper regions, which are more susceptible to B₁ inhomogeneity artifacts, are listed in rows 1–3.</p

Comparison of hepatic ADC-values between all three MR-scanners.

<p>Bland-Altman plot of mean ADC values from the left lobe of the liver comparing the 1.5 T system with the (A) first generation 3 T and (B) second generation 3 T scanners in volunteers. Mean ADC values of the first generation 3 T are on average 0.68×10⁻³ mm²/s lower than those measured on the 1.5 T system. Mean ADC values are similar in the 1.5 T and second generation 3 T scanners. (x-axis: average/y-axis: difference of ADC at 1.5 T and the corresponding 3 T systems (×10-3 mm³/s)).</p

Representative ADC-images.

<p>Representative ADC-images positioned at the same level of the left lobe of the liver from the same volunteer in all three scanners (A–C). Inhomogeneous signal is seen particularly in the left lobe of the liver with the first generation 3 T scanner (B).</p