Apparent Diffusion Coefficient ADC

2 Apparent Diffusion Coefficient (ADC), DWI. Diffusion-weighted magnetic resonance imaging (DWI) with calculation of the apparent diffusion coefficient (ADC) of water is a widely used noninvasive method to measure movement of water from the extracellular to the intracellular compartment during cerebral ischemia. 

A range of liquids suitable as quality control test objects for measuring the accuracy of clinical MRI diffusion sequences (both ADC and tensors) has been identified and characterized. The self-diffusion coefficients for 15 liquids (values at 22 °C range from 0.36 to 2.2 x 10 m s ) were measured at 15-30 °C using an NMR spectrometer. 

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Besides establishing the diagnosis of ischemic stroke, DWI also offers the capability of measuring the approximate age of infarcts. The apparent diffusion coefficient (ADC) of water, a measure of diffusion that can be derived easily from DWI images, follows a typical sequence of changes in evolving infarcts. °" ADC... 

Schlaug G, Siewert B, Benfield A, Edelman RR, Warach S. Time course of the apparent diffusion coefficient (ADC) abnormality in human stroke. Neurology 1997 49 113-119. 

Fig. 4.6. Quantitative maps of the apparent diffusion coefficient (ADC) in cats subjected to 1-h complete cerebrocir-culatory arrest followed by 180 min of recirculation. Each row represents one animal. The pre-ischemic condition is shown by the first left column. Images show a central coronal slice that was measured at six time points per animal. Note the early decline of ADC after onset of ischemia and the rapid post-ischemic normalization in the lower three rows indicating recovery in those animals. The upper two rows depict animals that did not recover during the reperfusion phase. [Reproduced with permission from Hossmann et al. (1994)]...

Fig. 4.13. Lesion evolution in reversible (90-min) middle cerebral artery occlusion (MCAO) in a rat. Upper row, quantitative images of the apparent diffusion coefficient (ADC) lower row, quantitative T2 images as measured serially over 22 days post stroke. Note the transient pseudo-normalization of the diffusion disturbance upon reperfusion and, second, after 7 days when initially reduced ADC values slowly shift to supernormal levels indicating the chronic infarct stage. [Reproduced with permission from Hoehn et al. (2001)]...

Fig. 4.14. Maps of the apparent diffusion coefficient (ADC) measured before and after embolic occlusion of the right middle cerebral artery in an animal without therapy (upper row) and in two animals with thrombolytic treatment initiated 1.5 h (middle row) and 4.5 h (lower row) after onset of ischemia. In the untreated animal, a decline of ADC was observed immediately after MCA occlusion that increased in size over time. Thrombolysis with recombinant tissue-type plasminogen activator (tPA) lead to the partial reversal of the ADC lesion over the first 5 h of therapy if started early. Late-onset thrombolysis at 4.5 h post occlusion did not reverse lesion growth, but was followed by a further lesion enlargement of the ischemic lesion. [Reproduced with permission from Hoehn et al. (2001)]...

Hoehn-Berlage M, Eis M, Back T, Kohno K,Yamashita K (1995a) Changes of relaxation times Tl, T2 and apparent diffusion coefficient ADC after permanent MCA occlusion in the rat ... 

Hossmann KA, Fischer M, Bockhorst K, Hoehn-Berlage M (1994) NMR imaging of the apparent diffusion coefficient (ADC) for the evaluation of metabolic suppression and recovery after prolonged cerebral ischemia. J Cereb Blood FlowMetab 14 723-731... 

Fig. 9.9. FLAIR (left) and T2-weighted (middle) images, and apparent diffusion coefficient (ADC) map (right) of a patient with leukoaraiosis. Multiple small and large focal lesions can be detected better on the FLAIR image than on the T2-weighted image. Lesions appear hyperintense (bright) on the ADC map indicating increased diffusion...

Schlaug G, Siewert B, Benfield A, Edelman RR, Warach S (1997) Time course of the apparent diffusion coefficient (ADC) abnormality in human stroke. Neurology 49 113-119 Takayama H, Mihara B, Kobayashi M et al (2000) Usefulness of diffusion-weighted MRI in the diagnosis of transient ischemic attacks. No To Shinkei 52 919-923 Tievsky AL, Ptak T, Farkas J (1999) Investigation of apparent diffusion coefficient and diffusion tensor anisotrophy in acute and chronic multiple sclerosis lesions. AJNR Am J Neuroradiol 20 1491-1499... 

Fig. 16.3. A 42-year-old man, found comatose after cardiac arrest. On the diffusion-weighted images there is hyperintensity in the motor cortex bilaterally (upper row). These changes are accompanied by decreased apparent diffusion coefficient (ADC) values (lower row)...

In a rat model using adipose-derived MSCs, exosome-treated rats harbored significantly smaller tumors and volume ratios at 20 days posttreatment, higher apparent diffusion coefficient (ADC) and ADC ratios (a measure of tumor microenvironment), more circulating and intratumoral NKT-cells, and low-grade hepatocellular carcinoma compared to the controls (Ko et al., 2015). 

Measurements of lipids in muscle and bone have also been made. Ye et al. found significantly higher levels of intramyocellular lipids (IMCL) in the tibialis anterior muscle of obese mice (Lep° /Lep° ) compared to control mice (Lep° / + heterozygous). Whereas, Xiao et al. have quantified the apparent diffusion coefficients (ADC) for extramyocellular lipids (EMCL) and IMCL in Sprague-Dawley rats along the direction perpendicular to muscle fibre orientation. The ADC for EMCL and IMCL were 13.8 0.9 X 10 and 4.6 0.7 x 10 mm s respectively. In bone. 

The role of DWI has to be determined (Ducreux et al. 2001). The nidus usually has a low signal with a large and homogeneous increase of the apparent diffusion coefficient (ADC). However, to date DWI does not play a major role in AVMs. 

MRI measurement of hyperpolarized gas diffusion is another important source of information about lung morphology and disease. The diffusion of gas is restricted by the microstructure of the lung—its small airways and alveolar walls—making diffusion sensitive to microstructural features on an alveolar distance scale, well below the spatial—resolution limits of conventional MRI. These properties can be quantified as a gas apparent diffusion coefficient (ADC), complementing information about the uniformity of gas transport derived from ventilation images. 

Recently, diffusion-weighted MR sequences has been proposed for the characterisation of focal hepatic lesions by using single-shot echo-planar imaging (EPI) technique with diffusion gradients in three directions and with different b values (Taouli et al. 2003). There is a significant difference between apparent diffusion coefficient (ADC) of cyst, heman-... 

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