• The Korean Journal of Nuclear Medicine
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• v.38 no.4
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• pp.318-324
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• 2004

Purpose: Philips GEMINI is a newly introduced whole-body GSO PET/CT scanner. In this study, performance of the scanner including spatial resolution, sensitivity, scatter fraction, noise equivalent count ratio (NECR) was measured utilizing NEMA NU2-2001 standard protocol and compared with performance of LSO, BGO crystal scanner. Methods: GEMINI is composed of the Philips ALLEGRO PET and MX8000 D multi-slice CT scanners. The PET scanner has 28 detector segments which have an array of 29 by 22 GSO crystals ($4{\times}6{\times}20$ mm), covering axial FOV of 18 cm. PET data to measure spatial resolution, sensitivity, scatter fraction, and NECR were acquired in 3D mode according to the NEMA NU2 protocols (coincidence window: 8 ns, energy window: $409[\sim}664$ keV). For the measurement of spatial resolution, images were reconstructed with FBP using ramp filter and an iterative reconstruction algorithm, 3D RAMLA. Data for sensitivity measurement were acquired using NEMA sensitivity phantom filled with F-18 solution and surrounded by $1{\sim}5$ aluminum sleeves after we confirmed that dead time loss did not exceed 1%. To measure NECR and scatter fraction, 1110 MBq of F-18 solution was injected into a NEMA scatter phantom with a length of 70 cm and dynamic scan with 20-min frame duration was acquired for 7 half-lives. Oblique sinograms were collapsed into transaxial slices using single slice rebinning method, and true to background (scatter+random) ratio for each slice and frame was estimated. Scatter fraction was determined by averaging the true to background ratio of last 3 frames in which the dead time loss was below 1%. Results: Transverse and axial resolutions at 1cm radius were (1) 5.3 and 6.5 mm (FBP), (2) 5.1 and 5.9 mm (3D RAMLA). Transverse radial, transverse tangential, and axial resolution at 10 cm were (1) 5.7, 5.7, and 7.0 mm (FBP), (2) 5.4, 5.4, and 6.4 mm (3D RAMLA). Attenuation free values of sensitivity were 3,620 counts/sec/MBq at the center of transaxial FOV and 4,324 counts/sec/MBq at 10 cm offset from the center. Scatter fraction was 40.6%, and peak true count rate and NECR were 88.9 kcps @ 12.9 kBq/mL and 34.3 kcps @ 8.84 kBq/mL. These characteristics are better than that of ECAT EXACT PET scanner with BGO crystal. Conclusion: The results of this field test demonstrate high resolution, sensitivity and count rate performance of the 3D PET/CT scanner with GSO crystal. The data provided here will be useful for the comparative study with other 3D PET/CT scanners using BGO or LSO crystals.

• Journal of Veterinary Clinics
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• v.11 no.2
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• pp.529-537
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• 1994

Sector scanner which has a conical end is used to image through the intercostal space because heart is protected by the ribs. Cardiac data published all around the world were also obtained by sector scanner. Although scanners being used in every small animal practice and animal hospital at college in Korea include convex ape and linear type, linear type is not appropriate f3r cardiac scan because of a wide contact surface. The purpose of this study is to establish ultrasonographic images of normal cardiac structures by measuring shape, size of reflectable cardiac structure according to restraint position in scanning normal heart of the puppies with 6.5 MHz convex scanner(SonoAce 4500, Medison, Korea) used in our veterinary teaching hospital, Seoul national university. Seventeen male and female puppies considered having healthy hear by X-ray and clinical examination are used feom April to July 1994. Scanning point selection of probe head and the distinction of imaged cardiac structures were accomplished by necropsy and cardiac scanning performed through thoracotomy under general anesthesia. At 10 o'clock position of transducer(at an angle of 30$^{\circ}$ between imaginary line from elbow joint to 3rd sternum and probe head, 60$^{\circ}$ from body surface, 4th intercostal space of right thorax) with the marker of scanner toward the head of dogs right atrium, left atrium and left ventricle were observed in 2, 3, 4, 5 intercostal space(2cm from the sternum) of experimental dog positioned ventrodorsally under general anesthesia. Under these conditions, the numerical values of imaged diastolic hear are as follows : the distance from skin to apex(mean$\pm$S.D) 47.53$\pm$6.94mm, thickness of left ventricular wall 6.00$\pm$1.60mm, length of left ventricle 16.27$\pm$5.31mm, width of left ventricle 15,33$\pm$4.25mm, length of left atrium 12.33$\pm$3.82mm, width of left atrium 11. 33$\pm$3.94mm, length of right atrium 1.00$\pm$2.41mm, width of right atrium 11.21$\pm$2.76mm and the area of left ventricle 270.92$\pm$109.81mm$^2$, area of left atrium 98.00$\pm$41.08mm$^2$, area of right atrium 62.75$\pm$21.04mm$^2$.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.12-16
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• 2012

Purpose : In conventional PET image reconstruction, iterative reconstruction methods such as OSEM (Ordered Subsets Expectation Maximization) have now generally replaced traditional analytic methods such as filtered back-projection. This includes improvements in components of the system model geometry, fully 3D scatter and low noise randoms estimates. SharpIR algorithm is to improve PET image contrast to noise by incorporating information about the PET detector response into the 3D iterative reconstruction algorithm. The aim of this study is evaluation of SharpIR reconstruction method in PET/CT. Materials and Methods: For the measurement of detector response for the spatial resolution, a capillary tube was filled with FDG and scanned at varying distances from the iso-center (5, 10, 15, 20 cm). To measure image quality for contrast recovery, the NEMA IEC body phantom (Data Spectrum Corporation, Hillsborough, NC) with diameters of 1, 13, 17 and 22 for simulating hot and 28 and 37 mm for simulating cold lesions. A solution of 5.4 kBq/mL of $^{18}F$-FDG in water was used as a radioactive background obtaining a lesion of background ratio of 4.0. Images were reconstructed with VUE point HD and VUE point HD using SharpIR reconstruction algorithm. For the clinical evaluation, a whole body FDG scan acquired and to demonstrate contrast recovery, ROIs were drawn on a metabolic hot spot and also on a uniform region of the liver. Images were reconstructed with function of varying iteration number (1~10). Results: The result of increases axial distance from iso-center, full width at half maximum (FWHM) is also increasing in VUE point HD reconstruction image. Even showed an increasing distances constant FWHM. VUE point HD with SharpIR than VUE point HD showed improves contrast recovery in phantom and clinical study. Conclusion: By incorporating more information about the detector system response, the SharpIR algorithm improves the accuracy of underlying model used in VUE point HD. SharpIR algorithm improve spatial resolution for a line source in air, and improves contrast recovery at equivalent noise levels in phantoms and clinical studies. Therefore, SharpIR algorithm can be applied as through a longitudinal study will be useful in clinical.

• Korean Journal of Digital Imaging in Medicine
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• v.10 no.1
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• pp.45-50
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• 2008

Recently, MR Cholangiography used mainly bu controlling of patient's breathing. There is breathing hold techniques to get images within shopt time and gating technique adjusted to respiration cycle for high resolution image. In this study, the aim of this experiment is to know on clinical usefulness compared with PACE and RTG thchniques. This study's period is from 2006 in November to 2007 in January. A total of 21 patients investigated at MAGNETOM Sonata 1.5T (SIEMENS Erlangen) with use of 12ch body coil. MR acquisition protocol used 3D turbo spin echo coronal sequence. Scan parameters applied to potimal setting in use as gating techniques, respectively. Analysis of consuming timing evaluated with rapidness. As analysis of quantity, the common bile duct, gall bladder measured in signal intensities, then these data were calculated by signal to noise ratio and contrast to noise ratio. Qualitative analysis, experienced 2radiologists and 3 RTs were evaluated into 3groups about artifact, accuracy of lesions, sharpness of the common bile duct or gall bladder. As a result of analysis, when compared to PACE, consuming time of the RTG took less than PACE, On both CNRs and SNRs, PACE technique was slightly high values than RTG(p<0.05). Qualitative analysis' results, discrimination of lesions in the common bile duct, gall bladder get a significance level in both RTG and PACE techniques but presence's artifact of breathing and pulsation highly demonstrate in PACE techniques. In conclusion, both PACE and RTG methods at MRCP provided prominently clinical information for the common bile duct, gall bladder. If machines have not limitation with performance, induction of breathing holding also will help getting diagnistic quality.

• The Korean Journal of Nuclear Medicine
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• v.35 no.6
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• pp.371-377
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• 2001

Purpose: One or more abnormal vertebrae detected on bone scintigraphy is a common finding in clinical practice, and it could pose a diagnostic dilemma especially in cancer patients. as either metastasis or benign disease may cause scintigraphic abnormality. The purpose of this study was to determine whether additional spine SPECT has a role in differentiating malignant from benign lesions in patients with back pain. Materials and Methods: We reviewed spine SPECT studios obtained over a three-year period in 108 patients. Among them, forty-five patients with abnormal SPECT and clinically followed records were evaluated (20 cancer patients were included). Uptake patterns were classified as follows: 1. Body: diffusely increased uptake, linear increased uptake of end plate, segmental increased uptake, and cold defect, 2. Posterior element: posterior to body (pedicle), posterior to Intervertebral disc space (facet joint), and spinous process. Lesions were correlated with radiological findings and with final diagnosis. Results: Sixty-nine bone lesions were detected on SFECT images, including 18 metastases, 28 degenerative diseases and 21 compression fractures. Cold defect (6) and segmental increased uptake (5) were dominant findings in metastasis; linear increased uptake (12), and facet joint uptake (15) were in degenerative change; and diffuse increased uptake (9), and linear increased uptake (9) were in compression fracture. Conclusion: Cold defect and segmental increased uptake of body were characteristic findings of metastasis, but care should be taken because compression fracture also shows segmental increased uptake in some cases. Degenerative disease was easily diagnosed because of the typical finding of linear increased uptake of end plate and facet joint. Therefore, additional bone SPECT after planar bone scan would be helpful for differentiating metastasis from benign condition in cancer patients.

• Journal of Gastric Cancer
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• v.1 no.3
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• pp.174-179
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• 2001

Purpose: For curative resection of recurrent gastric cancer, it is imperative that there be no unrecognized foci of tumoral disease outside the operation field. PET (positron emission tomography) with FDG (18 fluoro-2 deoxy-D-glucose) is a whole-body imaging technique that exploits the increased rate of glycolysis in tumor cells to detect disease. The authors evaluated the usefulness of FDG-PET in assessing resectability of recurrent gastric cancer. Materials and Methods: Seven patients with recurrent gastric cancer were studied with FDG-PET from December 1998 to October 2000. All FDG-PET images were interpreted in conjunction with conventional diagnostic methods. All imaging results were correlated with the pathological diagnosis and clinical outcome. Results: A final diagnosis of recurrence was obtained at 14 sites in all 7 patients by histology or clinical follow up. Locoregional recurrence, including distant metastasis, developed in 6 of 7 patients and distant recurrence in only one. FDG-PET detected all recurrent sites (5 locoregional and 5 distant) in 5 patients without peritoneal recurrence, but did not detect peritoneal seeding in 2 patients with peritoneal recurrence. The accuracy of FDG-PET in estimating resectability was $71.4\%$ (5/7), and that of CT and PET together was $85.7\%$ (6/7). A curative resection could be performed in three of the recurrent patients (2 locoregional and 1 distant recurrence). Conclusion: Our results suggest that FDG-PET may be useful for detecting locoregional and distant recurrence of gastric cancer and for selecting appropriate treatment. However, considering that FDG-PET was limited in detecting peritoneal seeding and determining the exact anatomical extension of tumor, it should be used in conjunction with other anatomical images.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.1
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• pp.54-60
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• 2010

Purpose: Nuclear medicine manufacturers provide various softwares which shorten imaging time using their own image processing techniques such as UlatraSPECT, ASTONISH, Flash3D, Evolution, and nSPEED. Seoul National University Hospital has introduced softwares from Siemens and Philips, but it was still hard to understand algorithm difference between those two softwares. Thus, the purpose of this study was to figure out the difference of two softwares in planar images and research the possibility of application to images produced with high energy isotopes. Materials and Methods: First, a phantom study was performed to understand the difference of softwares in static studies. Various amounts of count were acquired and the images were analyzed quantitatively after application of PIXON, Siemens and ASTONISH, Philips, respectively. Then, we applied them to some applicable static studies and searched for merits and demerits. And also, they have been applied to images produced with high energy isotopes. Finally, A blind test was conducted by nuclear medicine doctors except phantom images. Results: There was nearly no difference between pre and post processing image with PIXON for FWHM test using capillary source whereas ASTONISH was improved. But, both of standard deviation(SD) and variance were decreased for PIXON while ASTONISH was highly increased. And in background variability comparison test using IEC phantom, PIXON has been decreased over all while ASTONISH has shown to be somewhat increased. Contrast ratio in each spheres has also been increased for both methods. For image scale, window width has been increased for 4~5 times after processing with PIXON while ASTONISH showed nearly no difference. After phantom test analysis, ASTONISH seemed to be applicable for some studies which needs quantitative analysis or high contrast, and PIXON seemed to be applicable for insufficient counts studies or long time studies. Conclusion: Quantitative values used for usual analysis were generally improved after application of the two softwares, however it seems that it's hard to maintain the consistency for all of nuclear medicine studies because result images can not be the same due to the difference of algorithm characteristic rather than the difference of gamma cameras. And also, it's hard to expect high image quality with the time shortening method such as whole body scan. But it will be possible to apply to static studies considering the algorithm characteristic or we can expect a change of image quality through application to high energy isotope images.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.122-127
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• 2010

Purpose: The Xpress3.$cardiac^{TM}$ which is a kind of wide beam reconstruction (WBR) method developed by UltraSPECT (Haifa, Israel) enables the acquisition of at quarter time while maintaining image quality. The purpose of this study is to investigate the usefulness of WBR method for decreasing scan times and to compare to it with filtered back projection (FBP), which is the method routinely used. Materials and Methods: Phantom and clinical studies were performed. The anthropomorphic torso phantom was made on an equality with counts from patient's body. The Tl-201 concentrations in the compartments were 74 kBq (2 ${\mu}Ci$)/cc in myocardium, 11.1 kBq (0.3 ${\mu}Ci$)/cc in soft tissue, and 2.59 kBq (0.07 ${\mu}Ci$)/cc in lung. The non-gated Tl-201 myocardial perfusion SPECT data were acquired with the phantom. The former study was scanned for 50 seconds per frame with FBP method, and the latter study was acquired for 13 seconds per frame with WBR method. Using the Xeleris ver. 2.0551, full width at half maximum (FWHM) and average image contrast were compared. In clinical studies, we analyzed the 30 patients who were examined by Tl-201 gated myocardial perfusion SPECT in department of nuclear medicine at Asan Medical Center from January to April 2010. The patients were imaged at full time (50 second per frame) with FBP algorithm and again quarter-time (13 second per frame) with the WBR algorithm. Using the 4D MSPECT (4DM), Quantitative Perfusion SPECT (QPS), and Quantitative Gated SPECT (QGS) software, the summed stress score (SSS), summed rest score (SRS), summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were analyzed for their correlations and statistical comparison by paired t-test. Results: As a result of the phantom study, the WBR method improved FWHM more than about 30% compared with FBP method (WBR data 5.47 mm, FBP data 7.07 mm). And the WBR method's average image contrast was also higher than FBP method's. However, in result of quantitative indices, SSS, SDS, SRS, EDV, ESV, EF, there were statistically significant differences from WBR and FBP(p<0.01). In the correlation of SSS, SDS, SRS, there were significant differences for WBR and FBP (0.18, 0.34, 0.08). But EDV, ESV, EF showed good correlation with WBR and FBP (0.88, 0.89, 0.71). Conclusion: From phantom study results, we confirmed that the WBR method reduces an acquisition time while improving an image quality compared with FBP method. However, we should consider significant differences in quantitative indices. And it needs to take an evaluation test to apply clinical study to find a cause of differences out between phantom and clinical results.