A new tomographic technique for absolute measurements of white and gray matter blood flow

The integrity of the white matter is as important as that of the gray matter and white matter pathology has commonly been reported in elderly subjects and in patients with organic dementia. The aim of the present study is to develop and evaluate an improved method for reliable tomographic measurements of absolute white and gray matter blood flow. The new tomographic method (modified Xe-SPECT) is based on an extension of the period of 133Xe inhalation from one to eight minutes followed by 22 instead of four minutes of breathing of ambient air. This gives a markedly enhanced signal from the white matter and better basis for correct quantification pf the blood flow. The arrival and clearance of the tracer are recorded by a three head gamma camera system that provides flow maps with a spatial resolution of about one cm. The new method has been evaluated in healthy younger and older (around 70 years) subjects as well as in a group of elderly patients with organic dementia. Our preliminary findings indicate that new and clinically valuable information is obtained by the improved Xe-SPECT method