Development of a novel method for visualizing restricted diffusion using subtraction of apparent diffusion coefficient values

Abstract

in order to visualize restricted diffusion, the present study developed a novel method called 'apparent diffusion coefficient (ADC) subtraction method (ASM)' and compared it with diffusion kurtosis imaging (DKI). The diffusion-weighted images of physiological saline, in addtion to bio-phatoms of low cell density and the highest cell density were obtained using two sequences with different effective diffusion times. Then, the calculated ADC values were subtracted. The mean values and standard deviations (SD) of the ADC values of physiological saline, low cell density and the highest cell density phantoms were 2.95±0.08x10-3 , 1.90±0.35x10-3 and 0.79±0.05x10-3 mm 2 /sec, respectively. The mean kurtosis values and SD of DKI were 0.04±0.01, 0.44±0.13 and 1.27±0.03, respectively. The ASM and SD values were 0.25±0.20x10 4 , 0.51±0.41x10 4 and 4.80±4.51x10 4 (sec/mm 2) 2 , respectively. Using bio-phantoms, the present study demonstrated that DKI exhibits restricted diffusion in the extracellular space. Similarly, ASM may reflect the extent of restricted diffusion in the extracellular space.

Evaluation of calculation processes of apparent diffusion coefficient subtraction method (ASM) imaging

“…The ASM principle utilizes the difference in the ADC values in an image pair of two ADC maps (ADC b and ADC m ). The subtraction of the two ADC values via ASM, obtained using different EDT, might permit visualization of the diffusion phenomena in a narrow space of 1.0 μm [ 10 ]. ASM visualizes the sum of the signal values of restricted diffusion of hydrogen atoms on a 1.0 μm scale in each pixel with the size of individual pixels determined by the image resolution.…”

“…The difference of ADC values in an image pair of two ADC maps (ADC b and ADC m ) is affected by the error during the imaging of ADC maps. This error becomes amplified when the ADC value increases [ 10 ]. Therefore, resolving this error is necessary for the calculation process of ASM.…”

“…Recently, a novel RD imaging technique named ADC subtraction method (ASM) was developed, which was created basically using the difference between two ADC values taken using two different diffusion times [ 10 ]. To create ASM images for clinical trial testing, an ASM imaging software was created in-house based on the principle of ASM [ 11 ].…”

Development of a novel phantom using polyethylene glycol for the visualization of restricted diffusion in diffusion kurtosis imaging and apparent diffusion coefficient subtraction method

“…In a recent study, ASM was proposed as a new technique for restricted diffusion (8). ASM enables the observation of water-molecule diffusion with a space-separation resolution of 1 µm.…”

“…One example of this is diffusion kurtosis imaging (DKI) (7) which has been developed and has been revealed to be as useful as ADC maps in certain clinical trials. A new technique for imaging restricted diffusion has recently been proposed; the ADC subtraction method (ASM) (8).…”