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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Asia Oceania Journal of Nuclear Medicine and Biology
- نوع مقاله: Journal Article
- کلمات کلیدی: SPECT/CT,dopamine transporter,fan-beam collimator
- چکیده:
- چکیده انگلیسی: Objective(s): The purpose of this study was to examine the optimal reconstruction parameters for brain dopamine transporter SPECT images obtained with a fan beam collimator and compare the results with those obtained by using parallel-hole collimators.
Methods: Data acquisition was performed using two SPECT/CT devices, namely a Symbia T6 and an Infinia Hawkeye 4 (device A and B) equipped with fan-beam (camera A-1 and B-1), low- and medium-energy general-purpose (camera A-2 and B-2), and low-energy high-resolution (camera A-3 and B-3) collimators. The SPECT images were reconstructed using filtered back projection (FBP) with Chang’s
attenuation correction. However, the scatter correction was not performed. A pool phantom and a three-dimensional (3D) brain phantom were filled with 123I solution to examine the reconstruction parameters. The optimal attenuation coefficient was based on the visual assessment of the profile curve, coefficient of variation (CV) [%], and summed difference from the reference activity of the pool phantom. The optimal Butterworth filter for the 3D-brain phantom was also determined based on a visual assessment. The anthropomorphic striatal phantom was filled with 123I solution at striatum-to-background radioactivity ratios of 8, 6, 4, and 3. The specific binding ratio (SBR) of the striatum (calculated by the CT method) was used to compare the results with those of the parallel-hole collimators.
Results: The optimal attenuation coefficients were 0.09, 0.11, 0.05, 0.05, 0.11, and, 0.10 cm-1 for cameras A-1, A-2, A-3, B-1, B-2, and B-3, respectively. The cutoff frequencies of the Butterworth filter were 0.32, 0.40, and 0.36 cycles/cm for camera A, and 0.46, 0.44, and 0.44 cycles/cm for camera B, respectively. The recovery rates of the SBRmean with camera A were 51.2%, 49.4%, and 45.6%, respectively. The difference was not
statistically significant. The recovery rates of the SBR with camera B were 59.2%, 50.7%, and 50.8%, respectively. Camera B-1 showed significantly high SBR values.
Conclusion: As the findings indicated, the optimal reconstruction parameters differed according to the devices and collimators. The fan beam collimator was found to provide promising results with each device.- انتشار مقاله: 11-07-1396
- نویسندگان: Keishin Morita,Akira Maebatake,Rina Iwasaki,Yuki Shiotsuki,Kazuhiko Himuro,Shingo Baba,Masayuki Sasaki
- مشاهده
- جایگاه : پژوهشی
- مجله: Asia Oceania Journal of Nuclear Medicine and Biology
- نوع مقاله: Journal Article
- کلمات کلیدی: PET,edge artifact,point-spread function
- چکیده:
- چکیده انگلیسی: Objective(s): We evaluated edge artifacts in relation to phantom diameter and reconstruction parameters in point spread function (PSF)-based positron emission tomography (PET) image reconstruction.
Methods: PET data were acquired from an original cone-shaped phantom filled with 18F solution (21.9 kBq/mL) for 10 min using a Biograph mCT scanner. The images were reconstructed using the baseline ordered subsets expectation maximization (OSEM) algorithm and the OSEM with PSF correction model. The reconstruction parameters included a pixel size of 1.0, 2.0, or 3.0 mm, 1-12 iterations, 24 subsets, and a full width at half maximum (FWHM) of the post-filter Gaussian filter of 1.0, 2.0, or 3.0 mm. We compared both the maximum recovery coefficient (RCmax) and the mean recovery coefficient (RCmean) in the phantom at different diameters.
Results: The OSEM images had no edge artifacts, but the OSEM with PSF images had a dense edge delineating the hot phantom at diameters 10 mm or more and a dense spot at the center at diameters of 8 mm or less. The dense edge was clearly observed on images with a small pixel size, a Gaussian filter with a small FWHM, and a high number of iterations. At a phantom diameter of 6-7 mm, the RCmax for the OSEM and OSEM with PSF images was 60% and 140%, respectively (pixel size: 1.0 mm; FWHM of the Gaussian filter: 2.0 mm; iterations: 2). The RCmean of the OSEM with PSF images did not exceed 100%.
Conclusion: PSF-based image reconstruction resulted in edge artifacts, the degree of which depends on the pixel size, number of iterations, FWHM of the Gaussian filter, and object size.- انتشار مقاله: 06-12-1395
- نویسندگان: Yuji Tsutsui,Shinichi Awamoto,Kazuhiko Himuro,Yoshiyuki Umezu,Shingo Baba,Masayuki Sasaki
- مشاهده
- جایگاه : پژوهشی
- مجله: Asia Oceania Journal of Nuclear Medicine and Biology
- نوع مقاله: Journal Article
- کلمات کلیدی: Positron Emission Tomography,FDG-PET/CT,Lung adenocarcinoma,Respiratory gating
- چکیده:
- چکیده انگلیسی: Objective(s): In positron emission tomography (PET) studies, thoracic movement under free-breathing conditions is a cause of image degradation. Respiratory gating (RG) is commonly used to solve this problem. Two different methods, i.e., phase-gating (PG) and amplitude-gating (AG) PET, are available for respiratory gating. It is important to know the strengths and weaknesses of both methods when selecting an RG method
for a given patient. We conducted this study to clarify whether AG or PG is preferable for measuring fluorodeoxyglucose (FDG) accumulation in lung adenocarcinoma and to investigate patient conditions which are most suitable for AG and PG methods.
Methods: A total of 31 patients (11 males, 20 females; average age: 11.6±70.1 yrs) with 44 lung lesions, diagnosed as lung adenocarcinoma between April 2012 and March 2013, were investigated. Whole-body FDG-PET/CT scan was performed with both PG and AG methods in all patients. The maximum standardized uptake value (SUVmax) of PG, AG, and the control data of these two methods were measured, and the increase ratio (IR), calculated as IR(%)= (Post – Pre)/Pre × 100, was calculated. The diameter and position
of lung lesions were also analyzed. We defined an ‘effective lesion’ of PG (or AG) as a lesion which showed a higher IR compared to AG (or PG). 8 (25.8%)
Results: The average SUVmax and average IR were 7.94±8.99 and 25.6±21.4% in PG and 6.70±7.60 and 14.4±4.0% in AG, respectively. Although there was no significant difference between the average SUVmax of PG and AG (P=0.09), the average IR of PG was significantly higher than that of AG (P<0.01). The number of PG- and AG-effective lesions was 32 (72.7%) and 12 (28.3%) , respectively. There was no significant difference in the average diameter or position of the lesions between the PG- and AG-effective lesions.There were 23 (74.2%) PG-effective and 8 (25.8%) AG-effective patients. No significant difference was observed in sex or age between PG- and AG-effective patients.
Conclusion: The PG method was more effective for measuring FDG accumulation of lung lesions under free-breathing conditions in comparison with the AG method.- انتشار مقاله: 29-11-1394
- نویسندگان: Yoshiyuki Kitamura,Shingo Baba,Takuro Isoda,Yasuhiro Maruoka,Satoshi Kawanami,Kazuhiko Himuro,Masayuki Sasaki,Hiroshi Honda
- مشاهده
- جایگاه : پژوهشی
- مجله: Asia Oceania Journal of Nuclear Medicine and Biology
- نوع مقاله: Journal Article
- کلمات کلیدی: SPECT/CT,iterative reconstruction,Attenuation Correction
- چکیده:
- چکیده انگلیسی: Objective(s): The aim of this study was to determine the optimal reconstruction parameters for iterative reconstruction in different devices and collimators for dopamine transporter (DaT) single-photon emission computed tomography (SPECT). The results were compared between filtered back projection (FBP) and different attenuation correction (AC) methods.
Methods: An anthropomorphic striatal phantom was filled with 123I solutions at different striatum-to-background radioactivity ratios. Data were acquired using two SPECT/CT devices, equipped with a low-to-medium-energy general-purpose collimator (cameras A-1 and B-1) and a low-energy high-resolution (LEHR) collimator (cameras A-2 and B-2).
The SPECT images were once reconstructed by FBP using Chang’s AC and once by ordered subset expectation maximization (OSEM) using both CTAC and Chang’s AC; moreover, scatter correction was performed. OSEM on cameras A-1 and A-2 included resolution recovery (RR). The images were analyzed, using the specific binding ratio (SBR). Regions of interest for the background were placed on both frontal and occipital regions.
Results: The optimal number of iterations and subsets was 10i10s on camera A-1, 10i5s on camera A-2, and 7i6s on cameras B-1 and B-2. The optimal full width at half maximum of the Gaussian filter was 2.5 times the pixel size. In the comparison between FBP and OSEM, the quality was superior on OSEM-reconstructed images, although edge artifacts were observed in cameras A-1 and A-2. The SBR recovery of OSEM was higher than that of FBP on cameras A-1 and A-2, while no significant difference was detected on cameras B-1 and B-2. Good linearity of SBR was observed in all cameras. In
the comparison between Chang’s AC and CTAC, a significant correlation was observed on all cameras. The difference in the background region influenced SBR differently in Chang’s AC and CTAC on cameras A-1 and B-1.
Conclusion: Iterative reconstruction improved image quality on all cameras, although edge artifacts were observed in images captured by cameras with RR. The SBR of OSEM with RR was higher than that of FBP, while the SBR of OSEM without RR was equal to that of FBP. Also, the SBR of Chang’s AC varied with different background regions in cameras A-1 and B-1.- انتشار مقاله: 27-11-1394
- نویسندگان: Akira Maebatake,Ayaka Imamura,Yui Kodera,Yasuo Yamashita,Kazuhiko Himuro,Shingo Baba,Kenta Miwa,Masayuki Sasaki
- مشاهده