Quantitative Monte Carlo-based brain dopamine transporter SPECT imaging
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ORIGINAL ARTICLE
Quantitative Monte Carlo‑based brain dopamine transporter SPECT imaging Tuija Kangasmaa1 · Eero Hippeläinen2 · Chris Constable3 · Sampsa Turunen2 · Antti Sohlberg3,4 Received: 28 May 2020 / Accepted: 16 September 2020 © The Japanese Society of Nuclear Medicine 2020
Abstract Objective Brain dopamine transporter imaging with I-123-labeled radioligands is technically demanding due to the small size of the imaging target relative to the spatial resolution of most SPECT systems. In addition, I-123 has high-energy peaks which can penetrate or scatter in the collimator and be detected in the imaging energy window. The aim of this study was to implement Monte Carlo (MC)-based full collimator–detector response (CDR) compensation algorithm for I-123 into a third-party commercial SPECT reconstruction software package and to evaluate its effect on the quantitative accuracy of dopaminergic-image analysis compared to a method where only the geometric component of the CDR is compensated. Methods In this work, we utilized a full Monte Carlo collimator–detector model and incorporated it into an iterative SPECT reconstruction algorithm. The full Monte Carlo model reconstruction was compared to standard reconstruction using an anthropomorphic striatal phantom filled with different I-123 striatal/cortex uptake ratios and with clinical I-123 Ioflupane DaTScan studies. Results Reconstruction with the full model yielded higher (13–25%) striatal uptake ratios than the conventional reconstruction, but the uptake ratios were still much lower than the true ratios due to partial volume effect. Visually, images reconstructed with the full Monte Carlo model had better contrast and resolution than the conventional images, with both phantom and patient studies. Conclusions Reconstruction with full Monte Carlo collimator–detector model yields higher quantitative accuracy than conventional reconstruction. Additional work to reduce the partial volume effect related errors would improve the accuracy further. Keywords SPECT · I-123 · Monte Carlo · Full collimator–detector model · Phantom
Introduction
* Tuija Kangasmaa [email protected] 1
Department of Clinical Physiology and Nuclear Medicine, Vaasa Central Hospital, Hietalahdenkatu 2‑4, 65130 Vaasa, Finland
2
Clinical Physiology and Nuclear Medicine, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 4, 00029 Helsinki, Finland
3
HERMES Medical Solutions, Strandbergsgatan 16, 11251 Stockholm, Sweden
4
Laboratory of Clinical Physiology and Nuclear Medicine, Päijät-Häme Central Hospital, Keskussairaalankatu 7, 15850 Lahti, Finland
Parkinson disease is a very common neurodegenerative disorder with symptoms attributed mainly to dopamine deficit [1, 2]. Iodine-123-labeled pharmaceuticals are used in clinical SPECT brain imaging of the dopaminergic system to diagnose Parkinsonian syndromes and they might be useful to monitor disease progression and effects of therapy [3–6]. For objective and more accurate eval
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