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Validity of microsphere model in cerebral blood flow measurement using N ‐isopropyl‐ p ‐(I‐123) iodoamphetamine
Author(s) -
Murase Kenya,
Tanada Shuji,
Mogami Hiroshi,
Kawamura Masashi,
Miyagawa Masao,
Yamada Masafumi,
Higashino Hiroshi,
Iio Atsushi,
Hamamoto Ken
Publication year - 1990
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596531
Subject(s) - microsphere , cerebral blood flow , white matter , blood flow , nuclear medicine , iodine 123 , isopropyl , diffusion , fick's laws of diffusion , biomedical engineering , physics , mathematics , chemistry , medicine , thermodynamics , anesthesia , magnetic resonance imaging , chemical engineering , engineering , radiology , organic chemistry
A microsphere model is sometimes used when calculating cerebral blood flow (CBF) using N ‐isopropyl‐ p ‐[I‐123]iodoamphetamine (IMP), and is based on the assumption that there is essentially no washout of IMP. The validity of a microsphere model was investigated by comparison with the values of CBF obtained by means of a model which takes into consideration the diffusion of IMP from brain tissue to blood (nonmicrosphere model). When calculating CBF by the latter model, the look‐up table method was used with expression of the double integral in the model equation by the recursion relations, a method which is useful for obtaining pixel‐by‐pixel values. The average rate constants for diffusion from brain to blood of gray and white matter were 0.021 and 0.016 min −1 , respectively. The values of CBF obtained by applying a microsphere model to the data acquired from 0 to 3.2 min after IMP injection were overestimated by ∼23% compared with those values obtained using a nonmicrosphere model. This is considered to be due to the effect of the IMP activity in the vascular space. Values obtained using the data acquired from 3.2 to 6.4 min were underestimated by ∼15 %. When the values of CBF obtained by a microsphere model were interpolated, they became nearly equal to those obtained using a nonmicrosphere model at about 4 to 5 min after injection. This is suggested to be the reason why the underestimation due to diffusion from brain to blood is cancelled out by the overestimation due to the IMP in the vascular space. Our preliminary results suggest that it is necessary to take the diffusion of IMP from brain tissue to blood into account for the quantification of CBF using IMP.