• The Korean Journal of Nuclear Medicine
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• v.30 no.4
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• pp.548-559
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• 1996

A series of performance measurements of positron emission tomography (PET) were performed following the recommendations of the Computer and Instrumentation Council of the Society of Nuclear Medicine and the National Electrical Manufacturers Association. We investigated the performance of the General Electric $Advance^{TM}$ PET. The measurements include the basic intrinsic tests of spatial resolution, scatter fraction, sensitivity, and count rate losses and randoms. They also include the tests of the accuracy of corrections: count rate linearity correction, uniformity correction, scatter correction and attenuation correction. GE $Advance^{TM}$ PET has bismuth germanate oxide crystals (4.0mm transaxial ${\times}$ 8.1mm axial ${\times}$ 30.0mm radial) in 18 rings, which form 35 imaging planes spaced by 4.25mm. The system has retractable tungsten septa 1mm thick and 12cm long. Transaxial resolution was 4.92mm FWHM in 2D and 5.14mm FWHM in 3D at the center. Average axial resolution in 2D decreased from 3.91mm FWHM at the center to 6.49mm FWHM at R=20cm. Average scatter fraction of direct and cross slices was 9.57%. Dead-time losses of 50% corresponded to a radioactivity concentration of $4.86{\mu}Ci/cc$ and a true count rate of 519 kcps in 2D. The accuracy of count rate linearity correction was 1.84% at the activity of $4.50{\mu}Ci/cc$. Non-uniformity was 2.06% in 2D and 2.93% in 3D. Remnant errors after scatter correction were 0.55% in 2D and 4.12% in 3D. The errors of attenuation correction were 6.21% (air), 0.20% (water), -6.32% (teflon) in 2D and 5.00% (air), 6.94% (water), 3.01% (teflon) in 3D. The results indicate the performance of GE $Advance^{TM}$ PET scanner to be well suited for clinical and research applications.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.89-112
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• 2005

We determine the rotation velocities of 108 spiral and irregular galaxies (XV-Sample) from first-order rotation curves from position-velocity maps, based on short 21-cm observations with the Westerbork Synthesis Radio Telescope (WSRT). To test the usual random motion corrections, we compare the global HI linewidths and the rotation velocities, obtained from kinematical fits to two-dimensional velocity fields for a sample of 28 galaxies (RC-Sample), and find that the most frequently used correction formulae (Tully & Fouque 1985) are not very satisfactory. The rotation velocity parameter (the random-motion corrected HI linewidth: W?), derived with these corrections, may be statistically equal to two times the true rotation velocity, but in individual cases the differences can be large. We analyse, for both RC- and XV-Samples, the dependence of the slope of, and scatter in the Tully-Fisher relation on the definition of the rotation velocity parameters- For the RC-Sample, we find that the scatter in the Tully-Fisher relation can be reduced considerably when the rotation velocities derived from rotation curves are used instead of the random-motion corrected global H I linewidths. No such reduction in the scatter is seen for XV-Sample. We conclude that the reduction of the scatter in the Tully-Fisher relation seems to be related to the use of two-dimensional velocity information: accurate rotation velocity and kinematical inclination.

• The Korean Journal of Nuclear Medicine
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• v.39 no.3
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• pp.191-199
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• 2005

Purpose: In order to obtain better quantitation of kidney uptake, this study is to evaluate a conjugate view method (CVM) using a geometric mean attenuation correction for kidney uptake and to compare it to Gate's method. Materials & Methods: We used a Monte Carlo code, SIMIND and a Zubal phantom, to simulate kidney uptake. SIMIND was both simulated with or without scatter for the Zubal phantom. Also, a real phantom test was carried out using a dual-head gamma camera. The activity of 0.5 mCi was infused into two small cylinder phantoms of 5 cm diameter, and then, they were inserted into a cylinder phantom of 20 cm diameter. The results by the CVM method were compared with ideal data without both of attenuation and scatter and with Gate's method. The CVM was performed with or without scatter correction. The Gate's method was performed without scatter correction and it was evaluated with regards to $0.12cm^{-1}\;and\;0.15cm^{-1}$ attenuation coefficients. Data were analyzed with comparisons of mean counts in the legions of interest (ROI), profiles drawn over kidney images and linear regression. Correlation coefficients were calculated with ideal data, as well. Results: In the case of the computer simulation, mean counts measured from ideal data, the CVM and the Gate's method were (right $998{\pm}209$, left: $896{\pm}249$), (right: $911{\pm}207$, left: $815{\pm}265$), and (right: $1065{\pm}267$, left: $1546{\pm}267$), respectively. The ideal data showed good correlation with the CVM and the correlation coefficients of the CVM, Gate's method were (right: 0.91, left: 0.93) and (right: 0.85, left: 0.90), respectively. Conclusion: The conjugate view method using geometric mean attenuation correction resulted in better accuracy than the Gate's method. In conclusion, the conjugate view method independent of renal depths may provide more accurate kidney uptake.

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.13-21
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• 2009

PET/CT is a machine for imaging in vivo functions or metabolic activities after the administration of radiopharmaceuticals labeled with radioisotope emitting positrons in the body. Recently the number of PET/CT installed in Korean medical institutions is increasing rapidly. In response, the number of PET/CT tests to be used in the diagnosis and treatment of tumors is also increasing every year, and this is increasing the necessity for developing the methods of PET/CT performance evaluation and quality control. Among the test items for the performance evaluation and quality control of PET/CT suggested in NU 2-2007, this study examined spatial resolution test, sensitivity test, image quality, attenuation accuracy & scatter correction test, scatter fraction, count losses and randoms test and accuracy( correction for count losses and randoms).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.2
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• pp.106-111
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• 2001

The applicability of near infrared reflectance spectroscopy(NIRS) was tested to determine the protein and oil contents in ground soybean [Glycine max (L.) Merr.] seeds. A total of 189 soybean calibration samples and 103 validation samples were used for NIRS equation development and validation, respectively. In the NIRS equation of protein, the most accurate equation was obtained at 2, 8, 6, 1(2nd derivative, 8 nm gap, 6 points smoothing and 1 point second smoothing) math treatment condition with SNV-D (Standard Normal Variate and Detrend) scatter correction method and entire spectrum by using MPLS (Modified Partial Least Squares) regression. In the case of oil, the best equation was obtained at 1, 4, 4, 1 condition with SNV-D scatter correction method and near infrared (1100-2500nm) region by using MPLS regression. Validation of these NIRS equations showed very low bias (protein:-0.016%, oil : -0.011 %) and standard error of prediction (SEP, protein: 0.437%, oil: 0.377%) and very high coefficient of determination ($R^2$, protein: 0.985, oil : 0.965). Therefore, these NIRS equation seems reliable for determining the protein and oil content, and NIRS method could be used as a mass screening method of soybean seed.

• Progress in Medical Physics
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• v.6 no.2
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• pp.13-19
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• 1995

The behavior of the correction factor associated with the collimator opening(head-scatter factor) were investigated for the 6MV x-ray beams of medical linear accelerator. The primary photon fluence was measured in air quasi-small fied size. Consideration in this study was given to the effect of head scatter factor with quasi-small fied size, the upper and lower collimator jaw scatter collection factors of quasi-small field (4-10cm) were measured with ion chamber. In general, the wedge factors which are used clinical practics are ignored of dependency on field sizes and depth. In wedge factors for each wedge filter were measured at various depth by using 6MV X-ray. In this present we inverstigated systematically the depth and field sizes dependency to determine the absorbed dose more accurately. Head scatter(upper-lower collimator jaw)appears to be (1) a small effect, less than 5％ over the range of clinical field sizes (2) generated primarily at the flattening filter and therefored influenced most by the upper collimator setting.

• Near Infrared Analysis
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• v.2 no.1
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• pp.29-36
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• 2001

This review paper outlines modern pretreatment methods used in NIR spectroscopy. The pretreatment methods can be divided into four categories. One method in is noise reduction. Smoothing is a representative method for the noise reduction. Another is baseline correction. The second derivative and multiplicative scatter correction (MSC) are most frequently employed for baseline correction. The third is centering and normalization and the last is resolution enhancement. Difference spectra, mean centering and second derivative are used in NIR spectroscopy as resolution enhancement methods. In this paper advantages and drawbacks of pretreatment methods currently used in NIR spectroscopy are discussed with many examples of NIR spectra.

• Proceedings of the Korean Society of Medical Physics Conference
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• 1999.11a
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• pp.126-127
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• 1999

• The Korean Journal of Nuclear Medicine
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• v.39 no.2
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• pp.75-81
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• 2005

Myocardial perfusion and function can be quantified using SPECT and PET. There was controversy over the usefulness of the correction techniques for physical artifacts, such as photon attenuation and scatter, in the quantification of myocardial perfusion using SPECT. However, the cumulated results of many investigations have leaded the consensus on the usefulness of the correction procedures to improve the accuracy and specificity of the myocardial SPECT in the assessment of coronary artery diseases. Although the clinical value of the myocardial perfusion PET has not been preyed yet, the absolute myocardial blood flow and perfusion reserve values quantified using myocardial PET are employed in many basic investigations. In this paper, the methods for the quantitative myocardial SPECT and PET will be reviewed.

• The Korean Journal of Nuclear Medicine
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• v.32 no.6
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• pp.471-481
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• 1998

The goals of developments in nuclear medicine instrumentation are to offer a higher-quality image and to aid diagnosis, prognosis assessment or treatment planning and monitoring. It is necessary for physicists and engineers to improve or design new instrumentation and techniques, and to implement, validate, and apply these new approaches in the practice of nuclear medicine. The researches in physical properties of detectors and crystal materials and advances in image analysis technology have improved quantitative and diagnostic accuracy of nuclear medicine images. This review article presents recent developments in nuclear medicine instrumentation, including scatter and attenuation correction, new detector technology, tomographic image reconstruction methods, 511 keV imaging, dual modality imaging device, small gamma camera, PET developments, image display and analysis methods.