Delta-ADC (Apparent Diffusion Coefficient) Analysis in Patients with Idiopathic Normal Pressure Hydrocephalus
We have developed the delta-apparent diffusion coefficient (ADC), a new parameter of the water dynamics of brain tissue using MRI. Delta-ADC is the changes in regional ADC values of the brain during the cardiac cycle. The study included 6 idiopathic norma
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Abstract We have developed the delta-apparent diffusion coefficient (ADC), a new parameter of the water dynamics of brain tissue using MRI. Delta-ADC is the changes in regional ADC values of the brain during the cardiac cycle. The study included 6 idiopathic normal pressure hydrocephalus (iNPH) patients (iNPH group) and 12 healthy volunteers (control group). ECG-triggered single-shot diffusion echo planar imaging (b = 0 and 1,000 s/mm2) was used on a 1.5-T MRI. The delta-ADC image was calculated from the maximum minus the minimum ADC value of all cardiac phase images (20 phases) on a pixel-by-pixel basis. Delta-ADC values in the white matter of the frontal, temporal, and occipital lobe were obtained. Delta-ADC values in the iNPH group were significantly higher than those in the control group in all regions. ADC values in the iNPH were also significantly higher than those in the control group, but the differences in the ADC between the groups in each region were much lower than those for the delta-ADC. Although the changes in the delta-ADC and ADC values were similar, there was no significant correlation between the delta-ADC and the ADC. These results suggest that the ADC and the delta-ADC may reflect different kinds of water dynamics. The ADC depends on the water content in brain tissue. On the other hand, delta-ADC depends on not only the water content, but also on the degree of the fluctuation of the water molecules. Delta-ADC analysis makes it possible to obtain non-invasively new and more detailed information on the regional brain condition in iNPH.
T. Osawa, M. Mase (), K. Demura, and K. Yamada Department of Neurosurgery, Nagoya City University Graduate School of Medical Sciences, 1-Kawasumi, Mizuho-ku, Mizuho-cho, Nagoya, 467-8602, Japan e-mail: [email protected] T. Miyati and H. Kan Faculty of Heath Sciences, Institute of Medical, Pharmaceutical and Health Science, Kanazawa University, 5-11-80, Kadotsuno, Kanazawa, 920-0942, Japan H. Kasai, M. Hara, and Y. Shibamoto Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-ku, Mizuho-cho, Nagoya, 467-8602, Japan
Keywords Idiopathic normal pressure hydrocephalus • Apparent diffusion coefficient (ADC) • Diffusion tensor images of MRI
Introduction There are many unsolved problems in the pathophysiology of idiopathic normal pressure hydrocephalus (iNPH). The diagnosis of iNPH continues to be difficult in some cases and many types of diagnostic examination have been attempted. However, in electing NPH patients for shunt surgery, an unambiguously useful and non-invasive method of examination has not yet been found that can be easily performed, or that is widely accepted in medical centers. It is reported that the ADC of the periventricular white matter increases in patients with hydrocephalus [2, 5, 7, 10]. It is also reported that the ADC of the periventricular white matter decreases after a tap test or a shunt operation [2, 5, 7, 10]. Diffusion-weighted imaging can detect internal and external cellular fluid volume more accurately
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