• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.79-83
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• 2008

As a new standard for performance measurement, NEMA NU2-2001 was presented recently. In this study, I investigated the spatial resolution, sensitivity, scatter fraction, and noise equivalent count ratio (NECR) in order to know the information of physical characteristics and system performance of GE discovery ST using this new standard. Bismuth germinate crystals ($6{\times}6$ array, $6.3mm{\times}6.3mm{\times}30mm$) were used in discovery ST (energy window:375-650 keV, coincidence window:11.7 nsec). To measure the sensitivity, five aluminum sleeves (Data Spectrum Corp., Chapel Hill, NC., USA, thickness:1.25 mm)-NEMA sensitivity phantom- filled with F-18 solution were used. Successive measurements in 2D and 3D acquisition mode were made with a line source at the center of transaxial field of view and 10 cm off from the center until the count was over 500,000. Spatial resolution was estimated using a point source (F-18, 0.1 mCi) at different locations in the FOV. Scatter fraction and NECR was tested using a NEMA scatter phantom. Dynamic data were acquired for 7 half-lives using F-18 solution. And true to background ratio was averaged at last three frames when the random rate was as small as ignorable for the calculation of scatter fraction. We anticipate this overall evaluated results could be used for the quality assurance and optimized image acquisition for clinical research.

• The Korean Journal of Nuclear Medicine Technology
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• v.22 no.1
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• pp.43-45
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• 2018

Purpose In this study, we evaluated image by applying with and without point spread function algorithm(PSF) according to reconstruction type. Materials and Methods Biograph mMR (Siemens, Germany) was used as PET/MR scanner. For phantom study, we used NEMA IEC Body phantom maintaining radioactivity ratio (hotsphere:background = 8:1). To evaluate phantom image quality, percent contrast recovery and signal to noise ratio (SNR) were used by drawing ROI to 4 spheres. In clinical study, the 20 patients who underwent simultaneous PET/MR was selected and set the ROI at liver. we evaluated images as SNR. Results In the phantom results, The percent contrast recovery applying PSF algoritm was high 5 % compared to without PSF algoritm and SNR was also high 11 %. In the clinical study result, we confirmed that The SNR applying PSF algoritm was high 5 % compared to without PSF algoritm. Conclusion We need to simulate a lot of phantom study and clinical analysis to improve image quality for PET/MRI.

• Progress in Medical Physics
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• v.13 no.3
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• pp.139-148
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• 2002

The measured attenuation correction with transmission (Tx) scans produced quantitatively accurate images. However, it was not clear for optimal emission (Ex) and Tx scan time in PET imaging. This study was to evaluate acceptable Ex and Tx scan time by simulating clinical situations using various phantoms. Cylindrical and NEMA phantom were used for $^{18}$ F-PET scan using 2D protocol in GE Advance PETTM scanner. Cylindrical phantom was filled with 136 MBq 18F, and five regions of interests (ROI) were drawn on 23 slices. NEMA phantom had three inserts containing water, air and polytetrafluoro-ethylene (PTFE). Outside of these inserts were filled with 309 MBq of $^{18}$ F, and total 12 ROIs were drawn on 23 slices. Scans were carried out according to five Ex scan times: 2, 5, 10, 15, and 30 min, and nine Tx scan times: 2, 3, 4, 5, 7, 10, 15, 20, and 30 min. Images were reconstructed using measured attenuation correction, and ROI analyses were performed for all images, and mean, standard deviation (SD), coefficient of variation and percent errors were calculated. For cylindrical phantom study, ROI mean and SD were decreased as Ex and Tx time increased. Coefficients of variation were kept constant, when Tx was greater than 10 min. The amount of error decreased for the increment of Ex time from 10 min to 15 min was almost the same to that from 15 min to 30 min. In NEMA phantom Tx 15 min showed the lowest er개r level when the percent errors for three inserts were summed for all of the Ex times. This study suggested that Ex 15 min and Tx 15 min were acceptable as optimal scan time for the scanning protocol and the dose of radiopharmaceuticals used in these phantom study.

• Journal of the Korea Safety Management & Science
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• v.15 no.4
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• pp.427-433
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• 2013

Recently, 18F-FDG PET based CT scan was a critical examination that the after, before plan diagnosis and treatment of tumors. But, due to the distortion of SUV that should be proportional to the metabolic rate of glucose in the tumor, the other measurement methods are being on study. In this study, compared the degree of distortion of SUV that according to the volume of the tumor analysis ROI and VOI using the NEMA IEC Phantom. The results, the SUVmax, mean value are rapidly decreased with threshold value 500 mm2 interval of the ROI analysis, 1500 mm3 interval of the VOI analysis. When compared SUVmax value SUVmean, ROI and VOI analysis VOI measurements was 1.077 times higher SUVmax was 0.981 times highe compared to the value of the ROI measurement. Compare MTV, SUV 2.0 as measured by the volume of the VOI to Volume showed a slightly higher results(Volume / MTV = $93.4 %{\pm}14.8 %$). Considering the above results, Tumor evaluation by 18F-FDG PET / CT scan Consider each threshold value should be analyzed due to larger SUV's Distortion depending on the size of the tumor. VOI analysis is recommended. because it showed the VOI analysis is higher than the ROI analysis SUVmax and lower SUVmean due to VOI analysis than once as a measure of the wider area as measured ROI analysis. MTV (R2 = 0.999), a result close to the actual size of the tumor. but, more research is needed in this regard, because SUV according to the standards of value are affected.

• Journal of the Korean Society of Radiology
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• v.18 no.1
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• pp.45-52
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• 2024

In this study, an AI-based algorithm was developed to prevent image quality deterioration and reading errors due to patient movement in PET/CT examinations that use radioisotopes in medical institutions to test cancer and other diseases. Using the Mothion Free software developed using, we checked the degree of correction of movement due to breathing, evaluated its usefulness, and conducted a study for clinical application. The experimental method was to use an RPM Phantom to inject the radioisotope 18F-FDG into a vacuum vial and a sphere of a NEMA IEC body Phantom of different sizes, and to produce images by directing the movement of the radioisotope into a moving lesion during respiration. The vacuum vial had different degrees of movement at different positions, and the spheres of the NEMA IEC body Phantom of different sizes produced different sizes of lesions. Through the acquired images, the lesion volume, maximum SUV, and average SUV were each measured to quantitatively evaluate the degree of motion correction by Motion Free. The average SUV of vacuum vial A, with a large degree of movement, was reduced by 23.36 %, and the error rate of vacuum vial B, with a small degree of movement, was reduced by 29.3 %. The average SUV error rate at the sphere 37mm and 22mm of the NEMA IEC body Phantom was reduced by 29.3 % and 26.51 %, respectively. The average error rate of the four measurements from which the error rate was calculated decreased by 30.03 %, indicating a more accurate average SUV value. In this study, only two-dimensional movements could be produced, so in order to obtain more accurate data, a Phantom that can embody the actual breathing movement of the human body was used, and if the diversity of the range of movement was configured, a more accurate evaluation of usability could be made.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.236-244
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• 2011

Recently, the number of interventional procedures has increased dramatically as an alternative of invasive surgical procedure. The need for the quality control program of the angiographic units has also increased, because of concerns about the increased patient dose and the importance of image quality of angiographic units for the successful procedures. The purpose of this study was to propose an optimal guideline for the quality control program of the angiographic units. We reviewed domestic and international standards about medical imaging system and we evaluated the quality of 61 angiographic units in Korea with the use of NEMA 21 phantom. According to the results of our study, we propose a guideline for the quality control program of the angiographic units. Quality control program includes tube voltage test, tube current test, HVL test, image-field geometry test, spatial resolution test, low-contrast iodine detectability test, wire resolution test, phantom entrance dose test. Proposed reference levels are as follows: PAE < $\pm$ 10% in tube voltage test, PAE < $\pm$ 15% in tube current test, minimum 2.3 mmAl at 80 kVp in HVL test, minimum 'acceptable' level at image-field geometry test, 0.8 lp/mm for detector size of 34-40cm, 1.0 lp/mm for detector size of 28-33cm, 1.2 lp/mm for detector size of 22-27cm in spatial resolution test, minimum 200mg/cc in low contrast iodine detectability test, phantom entrance dose should be under 10R/min, 0.012 inch wire should be seen at static wire resolution test, and 0.022 inch wire should be seen at moving wire resolution test.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.2
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• pp.30-35
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• 2011

Purpose: The Boramae Hospital are currently using Wide beam reconstruction (WBR: UltraSPECT, Israel) to improve the resolution. The Xact-bone belongs to the WBR. It has been reported that Xact-bone helps us to improve image resolution and contrast. This study will be evaluated clinical usefulness of Xact-bone method. Materials and Methods: The usefulness evaluation of Xact-bone method was analyzed in resolution test and contrast ratio. The resolution test in Planar image were obtained from Full width at half maximum (FWHM) by using capillary tube. And the contrast ratio was obtained from Bone and Soft tissue (B/S) ratio values that were acquired from bone scan study of 50 patients before and after using the Xact-bone method. We prepared the Triple Line Source Phantom, NEMA IEC Body Phantom and Standard Jaszczak Phantom to acquire the FWHM and Contrast Ratio values of Single photon emission computed tomography (SPECT) image. Subsequently we compared among the Filtered backprojection (FBP), Orderd subset expectation maximization (OSEM) and Xact-Bone image. Results: The results of the planar Xact-bone data improved resolution about 20% by using capillary tube. In addition it was improved B/S ratio about 15%. When using Triple Line Source Phantom, SPECT Xact-bone data improved resolution for both FBP, OSEM methods about 20% and 10%, respectively. Contrast ratio in each spheres has also been increased for both methods that using NEMA IEC body Phantom and Standard Jaszczak Phantom. Conclusion: When we were using Xact-bone method, we could see to improve the resolution and Contrast ratio as compared to do not use the Xact-bone method. Accordingly, by using WBR's Xact-bone method is expected to improve the image quality. However, when introducing new software, it is needed to match the characteristics of the hospital protocol and clinical application.

• The Korean Journal of Nuclear Medicine Technology
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• v.20 no.1
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• pp.24-27
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• 2016

Purpose In this study, we evaluated image quality of lesion in the vicinity according filling and empty bladder developing bladder phantom. Materials and Methods Bladder phantom was developed by modifying NEMA IEC body phantom. Air-balloon was described as bladder and 6 insert were set as lesion in the vicinity bladder according to distance. The images were evaluated in terms of % BV, comparison of SUV and peak count rate (Single, Random and True count). Results % BV was decreased far away from bladder. There were different for SUV about $7.8{\pm}3.8%$ between filling and empty bladder. True count rate was decreased about 38 %. Single and random count were increased about 44, 61%. Conclusion When the lesion is close to bladder, noise is increased. That's why prior to PET-CT scan, It is important to urinate. and It helps patient to get the accurate result.

• The Korean Journal of Nuclear Medicine Technology
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• v.21 no.2
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• pp.31-36
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• 2017

Purpose Recently, the performance of PET/CT scanner has been improved and various techniques have been developed to increase the image quality such as Sensitivity and Resolution. The purpose of this study is to evaluate the usefulness of Q.Clear (a fully convergent iterative reconstruction) technique of GE Discovery IQ equipment to enhance the image quality. Materials and Methods All scans were acquired by Discovery IQ (GE Healthcare, MI, USA). In NEMA IEC Body Phantom test, Background to Hot-sphere (10 mm, 13 mm, 17 mm, 22 mm) ratio was 1:4 and scan time was 3 minutes. The images were reconstructed by VPHDs (VUE Point High-Definition + SharpIR) and Q.Clear to evaluate each Contrast. We injected 18F-FDG 187 M㏃ to PET/SPECT Performance Phantom. And then it was scanned for 4 minutes to evaluate Resolution and Uniformity. T-test statistical analysis was performed on SUVmax of small lesions less than 2 cm in 100 clinical patients regardless of disease type. Results In the NEMA IEC Body Phantom, the Contrast was $63.6{\pm}5.7%$ (VPHDs) and $75{\pm}4.8%$ (Q.Clear). In the PET/SPECT Performance Phantom, the Resolution was 9.2 mm (VPHDs) and 7.3 mm (Q.Clear). Uniformity of Q.Clear was 10.8% better than VPHDs. T-test statistic of the clinical patients showed a significant difference of p value of 0.021. Conclusion Both the phantom test and the clinical results showed that the quality of the image was improved in Q.Clear was applied. The SUVmax was highly measured in Q.Clear and the lesions were clearly distinguished visually. Therefore Q.Clear can be useful in various aspects such as dose-reduction, patients evaluation and image analysis.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.67-71
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• 2013

Purpose: The Change of CT exposure condition have a effect on image quality and patient exposure dose. In this study, we evaluated effect CT image quality and SUV when CT parameters (Pitch, Rotation time) were changed. Materials and Methods: Discovery Ste (GE, USA) was used as a PET/CT scanner. Using GE QA Phantom and AAPM CT Performance Phantom for evaluate Noise of CT image. Images are acquired by using 24 combinations that four stages pitch (0.562, 0.938, 1.375, 1.75:1) and six stages X-ray tube rotation time (0.5s-1.0s). PET images are acquired using 1994 NEMA PET Phantom ($^{18}F-FDG$ 5.3 kBq/mL, 2.5 min/frame). For noise test, noise are evaluated by standard deviation of each image's CT numbers. And then we used expectation noise according to change of DLP (Dose Length Product) to experimental noise ratio for index of effectiveness. For spatial resolution test, we confirmed that it is possible to identify to 1.0 mm size of the holes at the AAPM CT Performance Phantom. Finally we evaluated each 24 image's SUV. Results: Noise efficiency were 1.00, 1.03, 1.01, 0.96 and 1.00, 1.04, 1.02, 0.97 when pitch changes at the QA Phantom and AAPM Phantom. In case of X-ray tube rotation time changes, 0.99, 1.02, 1.00, 1.00, 0.99, 0.99 and 1.01, 1.01, 0.99, 1.01, 1.01, 1.01 at the QA Phantom and AAPM Phantom. We could identify 1.0 mm size of the holes all 24 images. Also, there were no significant change of SUV and all image's average SUV were 1.1. Conclusion: 1.75:1 pitch is the most effective value at the CT image evaluation according to pitch change and It doesn't affect to the spatial resolution and SUV. However, the change of rotation time doesn't affect anything. So, we recommend to use the effective pitch like 1.75:1 and adequate X-ray tube rotation time according to patient size.