• Journal of radiological science and technology
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• v.33 no.4
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• pp.335-340
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• 2010

This paper is about a projection method to check existence of radius groove penetration of screw after distal radius fracture operation using the T-type plate. Angle of Radius groove was analyzed by fifty one CT images that contains patients' wrist and twenty cases of radius specimens. After making radius phantom by plaster, we set the screw so that it penetrated 2.4 mm depth of radius groove. Then, we projected the phantom by X-ray in change of the elevation and supination angle of distal radius by 5 degree interval on 0~30 degree. The average value of groove angle in the wrist CT images was 14.4 degree and the radius specimens was 16.3 degree. Screws penetrating radius groove of the phantom have different lengths according to elevation angle and supination angle. Consequently, in order to confirm existence and nonexistence of radius groove penetration of the screw in tangential projection after distal radius fracture operation using the T-type plate, we recommend 5 degree of elevation angle and 20 degree of supination angle.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.1
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• pp.161-173
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• 1999

This study was performed to compare the bone mineral densities measured at mandibular premolar area by copper-equivalent image and hydroxyapatite phantom with those measured at radius by dual energy absorptiometry and to evaluate the clinical usefulness of Digital system with slide scanner, copper-equivalent image, and hydroxyapatite phantom. For experiment. intraoral radiograms of 15 normal subjects ranged from 20 years old to 67 old were taken with copper-step wedge at mandibular premolar area and bone mineral densities calculated by conversion equation to bone mineral density of hydroxyapatite were compared with those measured at radius distal 1/3 area by Hologic QDR-1000. Obtained results as follows: 1) The conversion equation was Y=5.97X-0.25 and its determination coefficient was 0.9967. The coefficient of variation in the measurement of copper-equivalent value ranged from 4％ to 8％ and showed high reproducibility. 2) The coefficient of variation in the measurement of bone mineral density by the equation ranged from 7％ to 8％ and showed high reproducibility. 3) The bone mineral densities ranged from 0.35 to 0.79g/cm2 at mandibular premolararea. 4) The correlation coefficient between bone mineral densities at mandibular premolar area and those at radius distal 1/3 area was 0.8965. As summary, digital image analyzing system using copper-equivalent image and hydroxyapatite phantom appeared to be clinically useful to measure the bone mineral density at dental area.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.3-7
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• 2012

Purpose : In myocardial perfusion SPECT, the type of orbit (circular vs. body contouring) that affect the image quality is still on the debate. Presently in the nuclear medicine field, the body contouring orbit acquisition is widely used to improve the image quality on the myocardial perfusion SPECT. But in case of body contouring acquisition using the vertical method with dual detect machine, there is a tendency of increasing the radius. In this research, we compared body contouring orbit acquisition with circular orbit acquisition, so we suggest ideal method that reduces the radius for improving image quality. Materials and Methods : Phantom and clinical studies were performed. The anthropomorphic torso phantom was made on equally with counts from patient's body. The study was performed under six different conditions. To compare image quality according to the radius, we increased radius sequentially per step during circular orbit acquisition. On the other hand, sensors that protect a collision and reduce the radius automatically were used to acquire image during body contouring orbit acquisition. So we compared FWHM value of apex. In clinical studies, we analyzed the 40 patients who were examined by Tl-201 gated myocardial perfusion SPECT in department of nuclear medicine at Asan Medical Center in August 2011. To acknowledge the differences according to the radius, we acquired the results two times using circular orbit acquisition and body contouring orbit acquisition. Results : In phantom study, we analyzed that increase of radius resulted in changes of FWHM value. It was 5.41, 6.24, 6.33, 6.42, 6.93 mm. On the other hand, using the body contouring orbit acquisition, FWHM value was 6.23 mm. In clinical study, difference of average radius between two methods was 2.5 cm (circular orbit acquisition was more close to patients). Conclusion : Through the experiments using Anthropomorphic torso phantom and patients data, we found that FWHM value of circular orbit acquisition was lower than body contouring orbit acquisition. As a result, if the difference of average radius exists approximately 3 cm, circular orbit type acquisition is better than body contouring type acquisition. But clinical investigation is only aimed to average radius, so it needs more investigation in comparison of patient's image.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2935-2940
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• 2023

A polystyrene phantom was developed following the guidance of the International Atomic Energy Association (IAEA) for gamma knife (GK) quality assurance. Its performance was assessed by measuring the absorbed dose rate to water and dose distributions. The phantom was made of polystyrene, which has an electron density (1.0156) similar to that of water. The phantom included one outer phantom and four inner phantoms. Two inner phantoms held PTW T31010 and Exradin A16 ion chambers. One inner phantom held a film in the XY plane of the Leksell coordinate system, and another inner phantom held a film in the YZ or ZX planes. The absorbed dose rate to water and beam profiles of the machine-specific reference (msr) field, namely, the 16 mm collimator field of a GK Perfexion^TM or Icon^TM, were measured at seven GK sites. The measured results were compared to those of an IAEA-recommended solid water (SW) phantom. The radius of the polystyrene phantom was determined to be 7.88 cm by converting the electron density of the plastic, considering a water depth of 8 g/cm². The absorbed dose rates to water measured in both phantoms differed from the treatment planning program by less than 1.1%. Before msr correction, the PTW T31010 dose rates (PTW Freiberg GmbH, New York, NY, USA) in the polystyrene phantom were 0.70 (0.29)% higher on average than those in the SW phantom. The Exradin A16 (Standard Imaging, Middleton, WI, USA) dose rates were 0.76 (0.32)% higher in the polystyrene phantom. After msr correction factors were applied, there were no statistically significant differences in the A16 dose rates measured in the two phantoms; however, the T31010 dose rates were 0.72 (0.29)% higher in the polystyrene phantom. When the full widths at half maximum and penumbras of the msr field were compared, no significant differences between the two phantoms were observed, except for the penumbra in the Y-axis. However, the difference in the penumbra was smaller than variations among different sites. A polystyrene phantom developed for gamma knife dosimetry showed dosimetric performance comparable to that of a commercial SW phantom. In addition to its cost effectiveness, the polystyrene phantom removes air space around the detector. Additional simulations of the msr correction factors of the polystyrene phantom should be performed.

• The Korean Journal of Nuclear Medicine Technology
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• v.15 no.1
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• pp.58-64
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• 2011

Objective: The 3-dimensional reconstruction method with resolution recovery modeling has advantages of high spatial resolution and contrast because of its precise modeling of spatial blurring according to the distance from detector plane. The aim of this study was to evaluate one of the resolution recovery reconstruction methods (Astonish, Philips Medical), compare it to other iterative reconstructions, and verify its clinical usefulness. Materials and Methods: NEMA IEC PET body phantom and Flanges Jaszczak ECT phantom (Data Spectrum Corp., USA) studies were performed using Skylight SPECT (Philips) system under four different conditions; short or long (2 times of short) radius, and half or full (40 kcts/frame) acquisition counts. Astonish reconstruction method was compared with two other iterative reconstructions; MLEM and 3D-OSEM which vendor supplied. For quantitative analysis, the contrast ratios obtained from IEC phantom test were compared. Reconstruction parameters were determined by optimization study using graph of contrast ratio versus background variability. The qualitative comparison was performed with Jaszczak ECT phantom and human myocardial data. Results: The overall contrast ratio was higher with Astonish than the others. For the largest hot sphere of 37 mm diameter, Astonish showed about 27.1% and 17.4% higher contrast ratio than MLEM and 3D-OSEM, in short radius study. For long radius, Astonish showed about 40.5% and 32.6% higher contrast ratio than MLEM and 3D-OSEM. The effect of acquired counts was insignificant. In the qualitative studies with Jaszczak phantom and human myocardial data, Astonish showed the best image quality. Conclusion: In this study, we have found out that Astonish can provide more reliable clinical results by better image quality compared to other iterative reconstruction methods. Although further clinical studies are required, Astonish would be used in clinics with confidence for enhancement of images.

• Korean Journal of Digital Imaging in Medicine
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• v.12 no.2
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• pp.97-101
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• 2010

This experimental study is carried out one of the General Hospital in Kyungbok providence. Abdomen Phantom being located Anterior-posterior(AP) position on portable bed, and the portable X-ray generating device was placed the phantom at $-90^{\circ}$ direction. The experiment were set 65 kVp, 10 mAs, $10{\times}10\;cm^2$, 100 cm(FOD) for the measurement. Digital proportional counting tube survey meter was used for measuring the space scatter dose. Measurement points of horizontal distribution was set up at $30^{\circ}$ interval by increasing 50 cm radius of upside, downside, left and right. Vertical distribution of measurement points were set up for the vertical plane with a radius of at $30^{\circ}$ intervals with 50cm increments. It is concluded that longer distance from the soure of X-ray significantly decrease radiation dose to the patient and use of the radiation protection device should be applied in clinical practice to reduce dose to the patient.

• Progress in Medical Physics
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• v.7 no.2
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• pp.19-28
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• 1996

It is important that the precise decision of the region and the accurate delivery of radiation dose required for treatment in the stereotactic radiosurgery. In this research, radiosurgery was carried with Leksell streotactic frame(LSF) which is especially developed water phantom to verify in experiment. Leksell Gamma Knife and LSF are used in radiosurgery is the spherical water phantom has the thickness of 2 mm, the radius of 160mm. The film for target localization and ionchamber for dose delivery was used in measurement instruments We compare the coordinate of target which is initialized by biplannar film with simple X-ray to the coordinate of film measured directly. The calculated dose by computer simulation and the measured dose by ionization chamber are compared. In this research, the target localization has the range ${\pm}$0.3mm for the acceptable error range and the absolute dose is :${\pm}$0.3mm for the acceptable error range. This research shows that the values measured by using the especially manufactured phantom are included the acceptable error range. Thus, this water phantom will be used continuously in the periodic quality assurance of Gamma Knife Unit and Leksell Stereotactic Frame.

• Journal of Korea Multimedia Society
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• v.19 no.1
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• pp.1-9
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• 2016

In this paper, we propose a method of measuring bone mineral density in a peripheral-type clinical X-ray CT using a phantom, and we propose a method of classifying osteoporosis using bone mineral density and bone structure parameters together. It segments the trabecular bone region and cortical bone region for the six sections of the phantom and calculates the average HU value of the segmented regions. By using these values, it derives an expression converting HU value to bone mineral density. It segments trabecular bone of 1 cm region in the end part of distal radius and extracts the bone mineral density and structural parameters for the trabecular bone region. We extracted bone mineral density and structural parameters for the 18 subjects each of normal and osteoporotic group. We carried out classification experiments using three classification methods; SAD, SVM, ANN. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value, likelihood ratio of the classification was improved in the order of ANN, SVM and SAD. Also, The sensitivity, specificity, accuracy, positive predictive value, negative predictive value, likelihood ratio of the classification was improved when we use the bone mineral density and structural parameters together.

• Progress in Medical Physics
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• v.7 no.1
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• pp.65-77
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• 1996

Using the 2-D and 3-D Hoffman brain phantom, 3-D Jaszczak phantom and Single Photon Emission Computed Tomography, the effects of data acquisition parameter, attenuation, noise, scatter and reconstruction algorithm on image quantitation as well as image quality were studied. For the data acquisition parameters, the images were acquired by changing the increment angle of rotation and the radius. The less increment angle of rotation resulted in superior image quality. Smaller radius from the center of rotation gave better image quality, since the resolution degraded as increasing the distance from detector to object increased. Using the flood data in Jaszczak phantom, the optimal attenuation coefficients were derived as 0.12cm$\^$-1/ for all collimators. Consequently, the all images were corrected for attenuation using the derived attenuation coefficients. It showed concave line profile without attenuation correction and flat line profile with attenuation correction in flood data obtained with jaszczak phantom. And the attenuation correction improved both image qulity and image quantitation. To study the effects of noise, the images were acquired for 1min, 2min, 5min, 10min, and 20min. The 20min image showed much better noise characteristics than 1min image indicating that increasing the counting time reduces the noise characteristics which follow the Poisson distribution. The images were also acquired using dual-energy windows, one for main photopeak and another one for scatter peak. The images were then compared with and without scatter correction. Scatter correction improved image quality so that the cold sphere and bar pattern in Jaszczak phantom were clearly visualized. Scatter correction was also applied to 3-D Hoffman brain phantom and resulted in better image quality. In conclusion, the SPECT images were significantly affected by the factors of data acquisition parameter, attenuation, noise, scatter, and reconstruction algorithm and these factors must be optimized or corrected to obtain the useful SPECT data in clinical applications.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.43-49
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• 2019

Purpose : We apply the Layered Rescanning PBS designed to complement the Pencil Beam Scanning(PBS), which is vulnerable to moving organs with the Moving Phantom, and compare the homogeneity with the single scan PBS. Methods and materials: Matrix X (IBA, Belgium) and Moving Phantom (standard imaging, USA) were used. A dose of 200 cGy was measured in the AP direction on a hypothetical tumor $10{\times}10{\times}5cm$. The plan type was planned as 4 kinds of sinlge scan PBS, rescan number 4, 8, 12 times. Were measured three times for each types. During the measurement, the respiratory cycle of the Moving Phantom was generally set to 4 seconds per cycle, and the movement radius in the S-I direction was set to 2 cm. In addition, beam on time was measured. Results : The mean values of $D_{max}$ in the PTV were $246.47{\pm}18.8cGy$, $223.43{\pm}8.92cGy$, and $222.47{\pm}7.7cGy$, $213.9{\pm}6.11cGy$ and the mean values of $D_{min}$ were $165.53{\pm}4.32cGy$, $173.13{\pm}11.94cGy$, $184.13{\pm}8.04cGy$, $182.67{\pm}4.38cGy$ and the mean values of $D_{mean}$ $192.77{\pm}6.98cGy$, $196.7{\pm}4.01cGy$, $198.17{\pm}4.96cGy$, $195.77{\pm}3.15cGy$ respectively. As the number of rescanning increased, the Homogeneity Index converged to 1. The beam on time was measured as 2:15, 3:15, 4:30, 5:37 on average. In the measurement process, in the low dose layer of the MU, the problem was found that it was not rescanned as many times as the set number of rescan. Conclusions : In the treatment of tumors with long-term movements, the application of layered rescanning PBS showed a more uniform dose distribution than single scan PBS. And as the number of rescan increase, the distribution of homogeneity is uniform. Compared with single scan plan and 12 rescan plan, HI value was improved by 0.32. Further studies are expected to be applicable to patients who can not be treated with respiratory synchronous radiation therapy.