Understanding ADC variation by fat content effect using a dual-function MRI phantom.

BACKGROUND: A dual-function phantom designed to quantify the apparent diffusion coefficient (ADC) in different fat contents (FCs) and glass bead densities (GBDs) to simulate the human tissues has not been documented yet. We propose a dual-function phantom to quantify the FC and to measure the ADC at different FCs and different GBDs. METHODS: A fat-containing diffusion phantom comprised by 30 glass-bead-containing fat-water emulsions consisting of six different FCs (0, 10, 20, 30, 40, and 50%) multiplied by five different GBDs (0, 0.1, 0.25, 0.5, and 1.0 g/50 mL). The FC and ADC were measured by the "iterative decomposition of water and fat with echo asymmetry and least squares estimation-IQ," IDEAL-IQ, and single-shot echo-planar diffusion-weighted imaging, SS-EP-DWI, sequences, respectively. Linear regression analysis was used to evaluate the relationship among the fat fraction (FF) measured by IDEAL-IQ, GBD, and ADC. RESULTS: The ADC was significantly, negatively, and linearly associated with the FF (the linear slope ranged from -0.005 to -0.017, R2 = 0.925 to 0.986, all p < 0.001). The slope of the linear relationship between the ADC and the FF, however, varied among different GBDs (the higher the GBD, the lower the slope). ADCs among emulsions across different GBDs and FFs were overlapped. Emulsions with low GBDs plus high FFs shared a same lower ADC range with those with median or high GBDs plus median or lower FFs. CONCLUSIONS: A novel dual-function phantom simulating the human tissues allowed to quantify the influence of FC and GBD on ADC. RELEVANCE STATEMENT: The study developed an innovative dual-function MRI phantom to explore the impact of FC on ADC variation that can affect clinical results. The results revealed the superimposed effect on FF and GBD density on ADC measurements. KEY POINTS: • A dual-function phantom made of glass bead density (GBD) and fat fraction (FF) emulsion has been developed. • Apparent diffusion coefficient (ADC) values are determined by GBD and FF. • The dual-function phantom showed the mutual ADC addition between FF and GBD.

Purification and characterization of a chitosanase from Serratia marcescens TKU011.

A chitosanase was purified from the culture supernatant of Serratia marcescens TKU011 with shrimp shell wastes as the sole carbon/nitrogen source. Zymogram analysis revealed the presence of chitosanolytic activity corresponding to one protein, which was purified by a combination of ion-exchange and gel-filtration chromatography. The molecular weight of the chitosanase was 21 kDa and 18 kDa estimated by SDS-PAGE and gel-filtration, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of the chitosanase were 5, 50 degrees C, pH 4-8, and <50 degrees C, respectively. The chitosanase was inhibited completely by EDTA, Mn(2+), and Fe(2+). The results of peptide mass mapping showed that three tryptic peptides of the chitosanase were identical to a chitin-binding protein Cbp21 from S. marcescens (GenBank accession number gi58177632) with 63% sequence coverage.