New Regression Equation for 123I-IMP Non-invasive Cerebral Blood Flow Measurement Using the Graph Plot Method

Area of Science:

• Nuclear Medicine
• Cerebrovascular Physiology
• Quantitative Imaging

Background:

• The graph plot (GP) method using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) offers a non-invasive estimation of quantitative cerebral blood flow (CBF).
• Previous regression equations for the GP method were based solely on resting-state data, potentially leading to underestimation of CBF values in high-flow conditions.

Purpose of the Study:

• To develop a novel regression equation for the GP method by incorporating both resting-state and acetazolamide (ACZ) challenge data.
• To evaluate the accuracy of this new equation in quantifying cerebral blood flow (CBF).

Main Methods:

• Utilized 123I-IMP SPECT and radioisotope-angiography (RIA) data from 26 patients undergoing both resting and ACZ challenge examinations.
• Compared the GP method with the conventional autoradiography (ARG) method, which involves arterial blood sampling.
• Derived a linear regression equation correlating the GP method's input function index with ARG-derived CBF values.

Main Results:

• A strong linear correlation (r=0.78) was achieved between the GP method and ARG for CBF values using data from both resting and ACZ challenge states (y=2.75x+15.1).
• The correlation was weaker (r=0.54) using only resting-state data (y=2.28x+18.4).
• CBF values derived from resting-state data alone were underestimated by approximately 20% in the high-flow range compared to rest+stress data.

Conclusions:

• The newly formulated regression equation for the GP method, incorporating rest and ACZ challenge data, provides a more accurate estimation of quantitative cerebral blood flow (CBF).
• This enhanced GP method is valuable for clinical applications requiring precise CBF measurements, particularly in conditions involving altered cerebral hemodynamics.