[Evaluation of the product-specific standard input function for the IMP-ARG method].

To confirm the previous reports demonstrating the difference in the octanol extraction fractions between the currently available two N-isopropyl-4-iodoamphetamine (123I) products (IMP(A) and IMP(B)), we newly developed the standard input function for IMP(B) in 19 healthy volunteers and compared it with the established standard input function, which has been originally generated with IMP(A). The octanol extraction fractions of IMP(B) were stable from 5 minutes to 16 minutes post injection and significantly higher than those of IMP(A). The mCBFs calculated with IMP(B) by using the established standard input function for IMP(A) tended to be higher than those with the combination of IMP(A) and the established standard input function though the difference was not significant. When measured with IMP(B) combined with the correspondent standard input function, mCBFs were identical to those calculated with IMP(A) with the established standard input function, suggesting that the appropriate standard input function should be used according to the product used.

[Estimation and optimization of the use of standard arterial input function for split-dose administration of N-isopropyl-p[123I]iodoamphetamine].

UNLABELLED: Use of a standard arterial input function and calibrating it by a single blood sample or a continuous arterial blood sample has been researched for a repeat CBF assessment with split-dose administration of N-isopropyl-p[123I]iodoamphetamine (IMP). METHODS: The study population consisted of 5 normal volunteers and 5 patients with cerebrovascular disease. IMP was injected twice (111 MBq/2 ml each) into the anti-cubital vein at a constant infusion speed for 1 min. The arterial input function was monitored during the study including a continuous measurement of radioactivity concentration of both the whole-blood and the octanol-soluble component (Real-Input Function, RIF). Standard input function was determined, and was calibrated either by a single blood sample or a continuous blood sample to estimate the Estimated-Input Function (EIF). Area-Under-the Curve (AUC) was then compared between RIF and EIF. RESULTS: In case EIF was estimated with a single blood sample, the minimum error of estimated AUC was obtained when calibrated at 7 minutes after either the 1st or 2nd injections. Deviation of AUC for [0, 30] was +/- 6.6%, and +/- 5.0%, respectively. If calibrated with a continuous blood sample, the minimum error of AUC with the continuous blood sampling period of 10 min for [0, 30] and [30, 60] was +/- 5.3% and +/- 4.0%, respectively. CONCLUSIONS: AUC of EIF with either a single or continuous blood sampling appeared to have reasonably small errors, suggesting the validity of the use of standardized input function in the split-dose IMP SPECT.

[Validation and optimization of the use of standardized arterial input function in N-isopropyl-p[123I]iodoamphetamine cerebral blood flow SPECT].

UNLABELLED: Use of a standardized arterial input function and calibrating it by a single blood sample has been proposed to assess quantitatively cerebral blood flow using N-isopropyl-p[123I]iodoamphetamine (IMP) and single-photon emission computed tomography. This study was intended to validate this approach using a larger number of measured arterial radioactivity curves in the clinical setting. METHOD: Arterial input function was measured for 50 patients at rest following the i.v. IMP, and its inter-subject variation was assessed. Difference between smokers and non-smokers in addition to effects of acetazolamide administration were particularly investigated. We also evaluated the accuracy of the calibration procedures by means of either a single blood sample or a continuous arterial blood withdrawal sampling for an early period. RESULTS: Inter-subject variation of the observed arterial input function appeared not to show large variations among the 50 patients, thus suggesting the validity of using the standardized arterial input function for the IMP SPECT study. There was a significant difference in the shape of the arterial input function between the smokers and non-smokers, but the calibration at an optimized sampling time provided the area-under-the curve (AUC) that was not significantly different between the two groups. The arterial input function after the acetazolamide showed no significant difference as compared with the shape at rest. The calibration of the standardized input function by means of the early integration of individual curve did not show better accuracy except for a short period of AUC (i.e., < 20 min) for longer integration period > 10 min. CONCLUSION: Thus, use of the standardized arterial input function has been validated for the IMP SPECT study. The single blood sampling procedure for calibrating the standardized input function has also been validated, and has been shown to provide better accuracy compared with the continuous withdrawal procedure.