Purpose: A method for defining image-derived input function (IDIF) has been introduced and evaluated for the quantification of the regional cerebral metabolic rate of glucose in positron emission tomography studies.
Materials and methods: First, a cubic region of interest containing the carotid artery was defined. The useful voxels in this cubic region, whose time-activity curves (TACs) decrease as assessed by linear regression after the initial rapid rise (about 2 min after injection), were selected, and their TACs were averaged to obtain the raw TAC of the IDIF. The IDIF was obtained from the raw TAC after correcting for partial volume and spillover effects using two blood samples. Data from 16 human subjects were used to test the proposed method. The Patlak approach was used to calculate the net ¹⁸F-fluoro-2-deoxyglucose (FDG) clearance with plasma-derived input function and our generated IDIF.
Results: The net FDG clearances calculated with the image-derived input function generated by our approach are consistent with those calculated with plasma-derived input function. The relative error percentages of the net FDG clearances calculated with the image-derived input function and the plasma derived input function are about 5%.
Conclusion: This study proposed a method to obtain the input function from the dynamic positron emission tomography images. The method was accurate and convenient to use.