Influence of brain atrophy using semiquantitative analysis in [123I]FP-CIT single-photon emission computed tomography by a Monte Carlo simulation study

Hiroki Nosaka,Masahisa Onoguchi,Ryosuke Murakawa,Ayano Onoma,Satoshi Kurata,Masaya Suda,Hiroyuki Tsushima

doi:10.1038/s41598-021-04078-x

Abstract

The specific binding ratio (SBR) is an objective indicator of N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-[123I] iodophenyl) nortropane ([123I]FP-CIT) single-photon emission computed tomography (SPECT) that could be used for the diagnosis of Parkinson’s disease and Lewy body dementia. One of the issues of the SBR analysis is that the setting position of the volume of interest (VOI) may contain cerebral ventricles and cerebral grooves. These areas may become prominent during the brain atrophy analysis; however, this phenomenon has not been evaluated enough. This study thus used Monte Carlo simulations to examine the effect of brain atrophy on the SBR analysis. The brain atrophy model (BAM) used to simulate the three stages of brain atrophy was made using a morphological operation. Brain atrophy levels were defined in the descending order from 1 to 3, with Level 3 indicating to the most severe damage. Projection data were created based on BAM, and the SPECT reconstruction was performed. The ratio of the striatal to background region accumulation was set to a rate of 8:1, 6:1, and 4:1. The striatal and the reference VOI mean value were decreased as brain atrophy progressed. Additionally, the Bolt’s analysis methods revealed that the reference VOI value was more affected by brain atrophy than the striatal VOI value. Finally, the calculated SBR value was overestimated as brain atrophy progressed, and a similar trend was observed when the ratios of the striatal to background region accumulation were changed. This study thus suggests that the SBR can be overestimated in cases of advanced brain atrophy.

Highlights

Abbreviations specific binding ratio (SBR) Specific binding ratio single-photon emission computed tomography (SPECT) Single-photon emission computed tomography volume of interest (VOI) Volume of interest brain atrophy model (BAM) Brain atrophy model dopamine transporter (DAT) Dopamine transporter PD Parkinson’s disease dementia with Lewy bodies (DLB) Dementia with Lewy bodies VsVOI Striatal VOI volume
It has been known for over three decades that the striatal dopamine transporter (DAT) density is reduced in dopaminergic degenerative disorders such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB)[1,2]
The single-photon emission computed tomography (SPECT) imaging of DAT density with N-ω-fluoropropyl2β-carbomethoxy-3β-(4-[123I]iodophenyl)nortropane ([123I]FP-CIT) is a novel imaging modality commonly used in clinical settings nowadays

Summary

Introduction

Abbreviations SBR Specific binding ratio SPECT Single-photon emission computed tomography VOI Volume of interest BAM Brain atrophy model DAT Dopamine transporter PD Parkinson’s disease DLB Dementia with Lewy bodies VsVOI Striatal VOI volume. Vs Striatal volume Cs Mean counts per volume for striatal VOI Cr Mean counts per volume for reference VOI Cstotal Striatal VOI total counts It has been known for over three decades that the striatal dopamine transporter (DAT) density is reduced in dopaminergic degenerative disorders such as Parkinson’s disease (PD) and dementia with Lewy bodies (DLB)[1,2]. A very common method to evaluate the reduction in DAT density with [123I]FP-CIT SPECT, is to perform semi-quantitative analyses using the specific binding ratio (SBR)[6,7] This ratio could be a prominent index of differential diagnosis, helping clinicians selects the appropriate patient treatment.

Methods

Results

Conclusion