Apparent diffusion coefficient normalization of normal liver: Will it improve the reproducibility of diffusion-weighted imaging at different MR scanners as a new biomarker?

Apparent diffusion coefficient (ADC) measurement in diffusion-weighted imaging (DWI) has been reported to be a helpful biomarker for detection and characterization of lesion. In view of the importance of ADC measurement reproducibility, the aim of this study was to probe the variability of the healthy hepatic ADC values measured at 3 MR scanners from different vendors and with different field strengths, and to investigate the reproducibility of normalized ADC (nADC) value with the spleen as the reference organ. Thirty enrolled healthy volunteers received DWI with GE 1.5T, Siemens 1.5T, and Philips 3.0T magnetic resonance (MR) systems on liver and spleen (session 1) and were imaged again after 10 to 14 days using only GE 1.5T MR and Philips 3.0T MR systems (session 2). Interscan agreement and reproducibility of ADC measurements of liver and the calculated nADC values (ADCliver/ADCspleen) were statistically evaluated between 2 sessions. In session 1, ADC and nADC values of liver were evaluated for the scanner-related variability by 2-way analysis of variance and intraclass correlation coefficients (ICCs). Coefficients of variation (CVs) of ADCs and nADCs of liver were calculated for both 1.5 and 3.0-T MR system. Interscan agreement and reproducibility of ADC measurements of liver and related nADCs between 2 sessions were found to be satisfactory with ICC values of 0.773 to 0.905. In session 1, the liver nADCs obtained from different scanners were consistent (P = 0.112) without any significant difference in multiple comparison (P = 0.117 to >0.99) by using 2-way analysis of variance with post-hoc analysis of Bonferroni method, although the liver ADCs varied significantly (P < 0.001). nADCs measured by 3 scanners were in good interscanner agreements with ICCs of 0.685 to 0.776. The mean CV of nADCs of both 1.5T MR scanners (9.6%) was similar to that of 3.0T MR scanner (8.9%). ADCs measured at 3 MR scanners with different field strengths and vendors could not be compared directly. Normalization of ADCs, however, may provide better reproducibility by overcoming these potential issues.

[Experimental study of the effect of liposome-mediated vascular endothelial growth factor gene on the flap survival in rats].

OBJECTIVE: To investigate the effect of VEGF gene on the random flap survival after pedicle division at different time in rats. METHODS: The random-pattern flaps were formed on the back of the 120 SD rats. PcDNAVEGF165 (gene) wrapped with liposome was injected into the flaps in experimental group (n = 40). The flaps in the two control groups were injected with PcDNA (n = 40) or saline (n = 40). 1, 3, 5, 7 days after injection, 10 rats in each group were randomly selected to performed pedicle division. 7 days after pedicle division, the rats were killed to measure the flap survival rate. The microvessels was studied by histologic examination. The expression of VEGF was assessed by immunohistochemical staining. The flaps were also examined under the electron ultrastructure microscopy. RESULTS: 1) Flap survival rate after pedicle division in experimental group at 1 day, 3 days, 5 days, 7 days after injection, were (45.45 +/- 12.24)%, (82.95 +/- 3.81)%, (85.00 +/- 3.38)%, (85.96 +/- 3.25)%, respectively. The flap survival rates were significant different between experimental group and the control groups at 3, 5, 7 days after injection (P < 0.05), but not at 1 days after injection (P > 0.05). 2) The average microvascular diameter and number in experimental group were significantly higher than those in control groups (P < 0.05). 3) The expression of VEGF in experimental group was significantly higher than that in the two control groups (P < 0.05). 4) Ultrastructure study showed more angiogenesis in experimental group. CONCLUSIONS: Subcutaneous injection of liposome-mediated VEGF gene can increase the survival rate of flap with early pedicle division. It is a simple, efficient, economic, and the relatively safe gene therapy.