Double-injection method for sequentially measuring cerebral blood flow with N-isopropyl-( 123I)p-iodoamphetamine

Kenya Murase, Takeshi Inoue, Hiroyoshi Fujioka, Yuji Yamamoto, Junpei Ikezoe

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

We investigated the accuracy of a double-injection method for sequentially measuring cerebral blood flow (CBF) with N-isopropyl-( 123I)p-iodoamphetamine (IMP) in simulation studies based on patient data and in clinical studies. The unidirectional clearance of IMP from the blood to the brain (K 1; nearly equal to CBF) in the first and second sessions was calculated by means of a microsphere model. The K 1 values in the first session (K 1 I) were calculated from C b(5)/Int_C a I, where C b(5) and Int_C a/ I are values for brain radioactivity 5 min after the first injection and for arterial blood radioactivity obtained by 5-min continuous sampling. The K 1 values in the second session (K 1/ II) were calculated by means of the following four methods. Method 1: [C b(t z + 5) - C b(t z)]/[Int_C a/ II - C a(t z) × 5], where C b(t z+5) and C b(t z) are the brain radioactivity levels 5 min after the second injection and at the time the second session was started (t z), respectively. Int_C a II and C a(t z) are the arterial blood radioactivity levels obtained by 5-min continuous sampling after the second injection and at t z, respectively. Method 2: [C b(t z + 5) - C b(t z)]/[Int_C a/ I × R], where R is the injection dose ratio. Method 3: [C b(t z + 5) - C b(t z × exp(- K 1/ I × 5/λ)]/Int_C a/ II, where λ is the population averaged partition coefficient. Method 4: same as Method 3 except that K 1/ I was replaced by K 1/ II obtained by means of Method 2. Theoretically, Method 4 appeared to be the best of the four methods. The change in K 1 during the second session obtained by Method 1 or 2 largely depended on R and t z, whereas Method 3 or 4 yielded a more reliable estimate than Method 1 or 2, without largely depending on R and t z. Since Method 2 was somewhat superior to other methods in terms of noninvasiveness and simplicity, it also had the potential for routine clinical use. The reproducibility of two sequential measurements of K 1 was investigated with clinical data obtained without any intervention. The response of CBF to acetazolamide challenge was also assessed by the above four methods. The knowledge gained by this study may assist in selecting a method for sequentially measuring CBF with a double injection of IMP.

Original languageEnglish
Pages (from-to)441-452
Number of pages12
JournalAnnals of Nuclear Medicine
Volume14
Issue number6
Publication statusPublished - 2000
Externally publishedYes

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Cerebrovascular Circulation
Iofetamine
Injections
Radioactivity
Brain

Keywords

  • Cerebral blood flow
  • Double-injection method
  • N-isopropyl-( I)p-iodoamphetamine
  • SPECT

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

Double-injection method for sequentially measuring cerebral blood flow with N-isopropyl-( 123I)p-iodoamphetamine. / Murase, Kenya; Inoue, Takeshi; Fujioka, Hiroyoshi; Yamamoto, Yuji; Ikezoe, Junpei.

In: Annals of Nuclear Medicine, Vol. 14, No. 6, 2000, p. 441-452.

Research output: Contribution to journalArticle

Murase, Kenya ; Inoue, Takeshi ; Fujioka, Hiroyoshi ; Yamamoto, Yuji ; Ikezoe, Junpei. / Double-injection method for sequentially measuring cerebral blood flow with N-isopropyl-( 123I)p-iodoamphetamine. In: Annals of Nuclear Medicine. 2000 ; Vol. 14, No. 6. pp. 441-452.
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AU - Yamamoto, Yuji

AU - Ikezoe, Junpei

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N2 - We investigated the accuracy of a double-injection method for sequentially measuring cerebral blood flow (CBF) with N-isopropyl-( 123I)p-iodoamphetamine (IMP) in simulation studies based on patient data and in clinical studies. The unidirectional clearance of IMP from the blood to the brain (K 1; nearly equal to CBF) in the first and second sessions was calculated by means of a microsphere model. The K 1 values in the first session (K 1 I) were calculated from C b(5)/Int_C a I, where C b(5) and Int_C a/ I are values for brain radioactivity 5 min after the first injection and for arterial blood radioactivity obtained by 5-min continuous sampling. The K 1 values in the second session (K 1/ II) were calculated by means of the following four methods. Method 1: [C b(t z + 5) - C b(t z)]/[Int_C a/ II - C a(t z) × 5], where C b(t z+5) and C b(t z) are the brain radioactivity levels 5 min after the second injection and at the time the second session was started (t z), respectively. Int_C a II and C a(t z) are the arterial blood radioactivity levels obtained by 5-min continuous sampling after the second injection and at t z, respectively. Method 2: [C b(t z + 5) - C b(t z)]/[Int_C a/ I × R], where R is the injection dose ratio. Method 3: [C b(t z + 5) - C b(t z × exp(- K 1/ I × 5/λ)]/Int_C a/ II, where λ is the population averaged partition coefficient. Method 4: same as Method 3 except that K 1/ I was replaced by K 1/ II obtained by means of Method 2. Theoretically, Method 4 appeared to be the best of the four methods. The change in K 1 during the second session obtained by Method 1 or 2 largely depended on R and t z, whereas Method 3 or 4 yielded a more reliable estimate than Method 1 or 2, without largely depending on R and t z. Since Method 2 was somewhat superior to other methods in terms of noninvasiveness and simplicity, it also had the potential for routine clinical use. The reproducibility of two sequential measurements of K 1 was investigated with clinical data obtained without any intervention. The response of CBF to acetazolamide challenge was also assessed by the above four methods. The knowledge gained by this study may assist in selecting a method for sequentially measuring CBF with a double injection of IMP.

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