Attenuation correction of myocardial SPECT by scatter-photopeak window method in normal subjects

金沢大学医薬保健研究域Objective: Segmentation with scatter and photopeak window data using attenuation correction (SSPAC) method can provide a patient-specific non-uniform attenuation coefficient map only by using photopeak and scatter images without X-ray computed tomography (CT). The purpose of this study is to evaluate the performance of attenuation correction (AC) by the SSPAC method on normal myocardial perfusion database. Methods: A total of 32 sets of exercise-rest myocardial images with Tc-99 m-sestamibi were acquired in both photopeak (140 keV ± 10%) and scatter (7% of lower side of the photopeak window) energy windows. Myocardial perfusion databases by the SSPAC method and non-AC (NC) were created from 15 female and 17 male subjects with low likelihood of cardiac disease using quantitative perfusion SPECT software. Segmental myocardial counts of a 17-segment model from these databases were compared on the basis of paired t test. Results: AC average myocardial perfusion count was significantly higher than that in NC in the septal and inferior regions (P < 0.02). On the contrary, AC average count was significantly lower in the anterolateral and apical regions (P < 0.01). Coefficient variation of the AC count in the mid, apical and apex regions was lower than that of NC. Conclusions: The SSPAC method can improve average myocardial perfusion uptake in the septal and inferior regions and provide uniform distribution of myocardial perfusion. The SSPAC method could be a practical method of attenuation correction without X-ray CT. © 2009 The Japanese Society of Nuclear Medicine

Correction of I-123 MIBG uptake with multi-window methods for standardization of the heart to mediastinum ratio

金沢大学大学院医学系研究科がん制御

Evaluating performance of a pixel array semiconductor SPECT system

Objectives: Small animal imaging has recently been focused on basic nuclear medicine. We have designed and built a small animal SPECT imaging system using a semiconductor camera and a newly designed collimator. We assess the performance of this system for small object imaging. Methods: We employed an MGC1500 (Acrorad Co.) camera including a CdTe semiconductor. The pixel size was 1.4 mm/pixel. We designed and produced a parallel-hole collimator with 20-mm hole length. Our SPECT system consisted of a semiconductor camera with the subject holder set on an electric rotating stage controlled by a computer. We compared this system with a conventional small animal SPECT system comprising a SPECT-2000H scanner with four Anger type cameras and pinhole collimators. The count rate linearity for estimation of the scatter was evaluated for a piechart phantom containing different concentrations of 99mTc. We measured the FWHM of the 99mTc SPECT line source along with scatter. The system volume sensitivity was examined using a flood source phantom which was 35 mm long with a 32-mm inside diameter. Additionally, an in vivo myocardial perfusion SPECT study was performed with a rat. Results: With regards to energy resolution, the semiconductor camera (5.6%) was superior to the conventional Anger type camera (9.8%). In the count rate linearity evaluation, the regression lines of the SPECT values were y = 0.019x + 0.031 (r2 = 0.999) for our system and y = 0.018x + 0.060 (r2 = 0.997) for the conventional system. Thus, the scatter count using the semiconductor camera was less than that using the conventional camera. FWHMs of our system and the conventional system were 2.9 ± 0.1 and 2.0 ± 0.1 mm, respectively. Moreover, the system volume sensitivity of our system [0.51 kcps/(MBq/ ml)/cm] was superior to that of the conventional system [0.44 kcps/(MBq/ml)/cm]. Our system provided clear images of the rat myocardium, sufficient for practical use in small animal imaging. Conclusions: Our SPECT system, utilizing a semiconductor camera, permits high quantitative analysis by virtue of its low scatter radiation and high sensitivity. Therefore, this system may contribute to molecular imaging of small animals and basic medical research

An ultra-high-energy collimator for small animal imaging in dual-isotope study of 18F and 99mTc

We have developed a pinhole collimator for small animal imaging using dual-isotopes, such as gamma and positron emitters. A lead cylinder containing a pinhole was placed around the subject (a small animal). The cylinder was equipped with a non-collimator gamma camera, and dual-isotope (99mTc-MIBI and 18F-FDG) SPECT was performed on a Wistar King Aptekman/hok (WKAH) rat. System planar sensitivity and Full-Width at Half-Maximum (FWHM) were measured for each radionuclide. System planar sensitivities for 99mTc and 18F SPECT were 2 and 7 cps/MBq, respectively. FWHMs for 99mTc and 18F SPECT were 2.0±0.5 and 2.7±0.5 mm, respectively. The collimator is relatively light (23 kg), and thus SPECT projection data could be acquired by rotating the gamma camera while the object remained stationary. The pinhole collimator can be used with a conventional rotating gamma camera. The present study demonstrated that it is possible to image organs in vivo in sufficient detail using the newly developed pinhole collimator. Further refinements to the experimental procedure may provide simultaneous high-resolution imaging of small animals using positron and gamma emitters with this collimator