Quantitative assessment of rest and acetazolamide CBF using quantitative SPECT reconstruction and sequential administration of (123)I-iodoamphetamine: comparison among data acquired at three institutions

Abstract

Purpose: A recently developed technique which reconstructs quantitative images from original projection data acquired using existing single-photon emission computed tomography (SPECT) devices enabled quantitative assessment of cerebral blood flow (CBF) at rest and after acetazolamide challenge. This study was intended to generate a normal database and to investigate its inter-institutional consistency.

Methods: The three institutions carried out a series of SPECT scanning on 32 healthy volunteers, following a recently proposed method that involved dual administration of (123)I-iodoamphetamine during a single SPECT scan. Intra-institute and inter-institutional variations of regional CBF values were evaluated both at rest and after acetazolamide challenge. Functional images were pooled for both rest and acetazolamide CBF, and inter-institutional difference was evaluated among these images using two independent software programs.

Results: Quantitative assessment of CBF images at rest and after acetazolamide was successfully achieved with the given protocol in all institutions. Intra-institutional variation of CBF values at rest and after acetazolamide was consistent with previously reported values. Quantitative CBF values showed no significant difference among institutions in all regions, except for a posterior cerebral artery region after acetazolamide challenge in one institution which employed SPECT device with lowest spatial resolution. Pooled CBF images at rest and after acetazolamide generated using two software programs showed no institutional differences after equalization of the spatial resolution.

Conclusions: SPECT can provide reproducible images from projection data acquired using different SPECT devices. A common database acquired at different institutions may be shared among institutions, if images are reconstructed using a quantitative reconstruction program, and acquired by following a standardized protocol.

Fig. 1

Scanning protocol flow for the DTARG procedures. ¹²³I-iodoamphetamine (¹²³I-IMP) was injected at 0 min, and 28-min resting dynamic SPECT scan was commenced. Blood sample for calibration of population input function was drawn at 10 min. Acetazolamide was administered at 20 min. CBF values are scaled by last frame (time 24–28 min). Second dynamic SPECT scan followed second injection of ¹²³I-IMP at 30 min

Fig. 2

Regions-of-interest (ROI) semi-automatically defined by the NEURO FLEXER software. ACA anterior cerebral artery, MCA middle cerebral artery, PCA posterior cerebral artery, BG basal ganglia. Hemisphere includes areas of ACA, MCA, PCA, BG, and thalamus

Fig. 3

Example clinical images of quantitative CBF before the spatial resolution equalization, at rest and after acetazolamide challenge. One typical case was selected from each of the three institutions. The same color scale was applied to these quantitative CBF images

Fig. 4

Stereotactic CBF images, normalized and averaged over the subjects at each institution and also for all subjects, at rest (a) and after acetazolamide challenge (b). Calculation was performed on spatial resolution-equalized images using 3D-SSP software. No region showed statistical difference between any combinations of the institutions, after the spatial resolution-equalization procedure

Fig. 5

Comparison of CBF images normalized over the subjects at each institution at rest (a) and after acetazolamide challenge (b). Spatial resolution-equalized CBF images were used for this analysis. Statistical analysis demonstrated that no significance was seen among the three institutions both at rest and after acetazolamide challenge, when the extent threshold of 100 voxels was selected. Note that all images are displayed using the same color scale with the normalized maximum values at each condition