Impact of injection dose, post-reconstruction filtering, and collimator choice on image quality of myocardial perfusion SPECT using cadmium-zinc telluride detectors in the rat.
BACKGROUND
The aims of this study were (1) to evaluate the impact of injection dose, post-reconstruction filtering, and collimator choice on image quality of myocardial perfusion single-photon emission computed tomography (SPECT) using cadmium-zinc telluride (CZT) detectors and (2) to determine how these factors affect measured infarct size in the in vivo rat.


METHODS
Twenty-four healthy and eight myocardial infarct (MI) rats underwent myocardial perfusion SPECT imaging after injection of various doses (25 to 200 MBq) of (99m)Tc-tetrofosmin using a standard (STD) five-pinhole collimator and high-sensitivity (HS) five-pinhole collimator. Image quality score, contrast-to-noise ratio, sharpness index, coefficient of variation (CV), and measured defect size were assessed as measures of image quality.


RESULTS
The image quality score increased and CV decreased as a function of injection dose. The contrast-to-noise ratio increased and sharpness index decreased as a function of Gaussian kernel size. When STD and HS were compared, HS tended to show higher image quality score and lower CV than STD. The use of post-reconstruction filter significantly improved image quality score and lessened CV. The reproducibility of defect size measurements, as assessed by intraclass correlation coefficients (ICC), between the collimators was poor-to-moderate (ICC = -0.31~0.57) with low (25 MBq) injection dose and with no or light (1.5-mm kernel size) filtering, whereas it was good-to-excellent (ICC = 0.75~0.97) with high (200 MBq) dose or low dose with heavy (2.5-mm kernel size) filtering. The filtering-related reproducibility was poor (ICC = -0.18~0.17) for STD with low injection dose, whereas it was good-to-excellent (ICC = 0.79~0.89) for HS. Furthermore, there was a filtering-related underestimation of defect size particularly with the use of heavy smoothing.


CONCLUSIONS
Appropriate imaging setting is important to obtain high quality images and thereby reliable measurements using a preclinical myocardial SPECT in the rat. When only a low injection dose (25 MBq) is allowed, we would recommend to use HS with light (1.5-mm kernel size) filtering.
School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan. mizu627@stu.kanazawa-u.ac.jp.
Asuka
A
Mizutani
Clinical Research Department, The Medical and Pharmacological Research Center Foundation, Wo 32, Inoyama, Hakui, Ishikawa, 925-0613, Japan. matsunari@mprcf.or.jp.
Ichiro
I
Matsunari
Wellness Promotion Science Center, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan. kobayasi@mhs.mp.kanazawa-u.ac.jp.
Masato
M
Kobayashi
School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan. koudai@nagasaki-u.ac.jp.|Department of Radioisotope Medicine, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4, Sakamoto, Nagasaki, 852-8523, Japan. koudai@nagasaki-u.ac.jp.
Kodai
K
Nishi
Department of Cardiology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0265, Japan. f-wataru@kanazawa-med.ac.jp.
Wataru
W
Fujita
Clinical Research Department, The Medical and Pharmacological Research Center Foundation, Wo 32, Inoyama, Hakui, Ishikawa, 925-0613, Japan. miyazaki@mprcf.or.jp.
Yoshiharu
Y
Miyazaki
Department of Nuclear Medicine, Technical University Munich, Ismaninger Str., Munich, 81675, Germany. stephan.nekolla@tum.de.
Stephan G
SG
Nekolla
School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan. kei@mhs.mp.kanazawa-u.ac.jp.
Keiichi
K
Kawai
Cadmium-zinc telluride; Collimator; Injection dose; Post-reconstruction filtering; Rat; SPECT