• Journal of radiological science and technology
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• v.44 no.3
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• pp.219-224
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• 2021

The purpose of these experiments is often to scan infected patients with MRI. Therefore, it is to investigate whether the antibacterial film containing silver ions, which is a non-magnetic substance, affects magnetic resonance imaging. In this experiment, the ACR phantom was used, not the patient. The ACR phantom was wrapped in an antibacterial film and the SNR, CNR, sagittal localization image, and geometrical accuracy were compared before and after. The experiment was performed 10 times and the averaged values were compared. There were no significant differences in the results of all experiments. The FDA recommends removing metal and antibacterial film masks during MRI scans. The reason is that there was one case of injury with facial burns. When I touched the antibacterial film to check the fever during the 2 hour experiment, I did not feel any particular fever. In light of the experimental results, it would be helpful to use an antibacterial film when testing an infected patient. The reason is that there isn't a difference before and after the experiment of SNR, CNR, and sagittal localization images.

• Journal of radiological science and technology
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• v.27 no.4
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• pp.49-54
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• 2004

Purpose : To valuate the usefulness of mammographic image by using phantom 1,2 to controls the enhancement of image quality. Procedure : Set up same equipments for experiment (all the qualification must be the same). Control group and 4 other experiment the developing mammographys by using the image system with film/intensifying screen and distribute marks on each test objects of phantom 1, 2. Result : The results of the experiment using phantom 1, 2 on control group and 4 others are : 1. phantom 1's valuation with 3 items. - control group received 29 out of 32 - group A received 25 - group B received 16 - group C received 11.5 - group D received 28.5 The evaluation shows that the system has proved to display excellent image quality except group B and C. 2. Phantom 2's valuation with 4 items. - control group received 38 out of 38 - group A received 30 - group B received 16 - group C received 12.5 - group D received 38 Even with phantom 2, group B and C has displayed poor image quality. Conclusion : Both experiments using phantom 1 and 2 have shown that the most strong factor that control and influence the image quality are the filming equipments. Especially, the developing system has most powerful influence above all.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1289-1294
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• 2018

The present study aims to investigate experimentally and theoretically thermal ablation in soft tissues by using high intensity focused ultrasound (HIFU) to assess tissue damage during HIFU thermotherapy. The HIFU field was calculated by solving the axisymmetric Khokhlov-Zabolotskaya-Kuznetsov equation from the frequency-domain perspective. The temperature field was calculated by solving Pennes' bioheat transfer equation, and the thermal dose required to create a thermal lesion was calculated by using the thermal dose formula based on the thermal dose of a 240-min exposure at $43^{\circ}C$. In order to validate the simulation results, we performed thermal ablation experiments in a tissue-mimicking phantom and ex-vivo porcine liver for two different HIFU source conditions by using a 1.1-MHz, single-element, spherically focused HIFU transducer. The small difference between the measured and the predicted lesion sizes suggests that the implementation of the numerical model used here should be modified to iteratively allow for temperature-dependent changes in the physical properties of tissues.

• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.157-167
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• 2005

In this paper, we propose a new phantom protection method for multi-dimensional index structures. The proposed method uses a hybrid approach of predicate locking and granular locking mechanisms. The proposed mechanism is independent of the types of multi-dimensional index structures, i.e., it can be applied to all types of index structures such as tree-based, file-based and hash-based index structures. Also, it achieves low development cost and high concurrency with low lock overhead. It is shown through various experiments that the proposed method outperforms existing phantom protection methods for multi-dimensional index structures.

• Progress in Medical Physics
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• v.18 no.4
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• pp.194-201
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• 2007

Although Gamma Knife irradiates much more radiation in a single session than conventional radiotherapy, there were only a few studies to measure absolute dose of a Gamma Knife. Especially, there is no report of application of International Atomic Energy Agency (IAEA) TRS-398 which requires to use a water phantom in radiation measurement to Gamma Knife. In this article, the authors reported results of the experiments to measure the absorbed dose to water of a Gamma Knife Model C using the IAEA TRS-398 protocol. The absorbed dose to water of a Gamma Knife model C was measured using a water phantom under conditions as close as possible to the IAEA TRS-398 protocol. The obtained results were compared with values measured using the plastic phantom provided by the Gamma Knife manufacturer. Two Capintec PR-05P mini-chambers and a PTW UNIDOS electrometer were used in measurements. The absorbed dose to water of a Gamma Knife model C inside the water phantom was 1.38% larger than that of the plastic phantom. The current protocol provided by the manufacturer has an intrinsic error stems from the fact that a plastic phantom is used instead of a water phantom. In conclusion, it is not possible to fully apply IAEA TRS-398 to measurement of absorbed dose of a Gamma Knife. Instead, it can be a practical choice to build a new protocol for Gamma Knife or to provide a conversion factor from a water phantom to the plastic phantom. The conversion factor can be obtained in one or two standard laboratories.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.137-143
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• 2013

Purpose: We are to find out the difference of calculated dose of treatment planning system (TPS) and measured dose in case of inhomogeneous organ structure. Materials and Methods: Inhomogeneous phantom is made with solid water phantom and cork plate. CT image of inhomogeneous phantom is acquired. Treatment plan is made with TPS (Pinnacle3 9.2. Royal Philips Electronics, Netherlands) and calculated dose of point of interest is acquired. Treatment plan was delivered in the inhomogeneous phantom by ARTISTE (Siemens AG, Germany) measured dose of each point of interest is obtained with Gafchromic EBT2 film (International Specialty Products, US) in the gap between solid water phantom or cork plate. To simulate lung cancer radiation treatment, artificial tumor target of paraffin is inserted in the cork volume of inhomogeneous phantom. Calculated dose and measured dose are acquired as above. Results: In case of inhomogeneous phantom experiment, dose difference of calculated dose and measured dose is about -8.5% at solid water phantom-cork gap and about -7% lower in measured dose at cork-solid water phantom gap. In case of inhomogeneous phantom inserted paraffin target experiment, dose difference is about 5% lower in measured dose at cork-paraffin gap. There is no significant difference at same material gap in both experiments. Conclusion: Radiation dose at the gap between two organs with different electron density is significantly lower than calculated dose with TPS. Therefore, we must be aware of dose calculation error in TPS and great care is suggested in case of radiation treatment planning on inhomogeneous organ structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5124-5130
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• 2014

Dilution of the contrast agent by analyzing the change in the signal intensity during MR angiography in accordance with the viscosity and osmotic pressure minimizes the side effects, and improves the image quality. The contrast agent molarity changes by the dilution of the contrast agent in the blood, as it is injected, which leads to a change in signal intensity. Based on this principle, a phantom was prepared and experiments were performed. After the phantom experiment, a clinical experiment was conducted using the results of the phantom experiment. From November 2013 to January 2014, a group of patients were classified into diluted contrast agent (30 persons) and undiluted (30 persons), and the signal intensity of the cerebral vessels was compared. The signal intensity of the phantom according to the molarity of the contrast agent increased sharply from 0.0125 mmol, reached a peak at 20 mmol, and achieved equilibrium from 200 mmol. Based on the study results, the signal intensity of the blood vessels in the brain through were compared in a clinical experiment. All the brain vessels in the imaging range with diluting a high content of the gadolinium contrast agent showed high signal intensity. This result supports the phantom experiment and means that using the 500mmol diluted contrast agent is better than using 1000mmol undiluted contrast agent because it is easier to approach the 20mmol level needed to achieve the highest signal intensity. This study has significance in that it can minimize the high viscosity and osmotic pressure, which can cause side effects and improve the image quality using the method of the dilution rate.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.339-346
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• 2003

MRI provides anatomical structure information with superb spatial resolution that can be utilized in clinical surgeries. Advanced image processing techniques in conjunction with the MRI-guided surgery is expected to be of great importance in brain surgeries in the near future. In this paper, we introduce an image-guided surgery technique using the stereo matching method. To perform image-guided biopsy operations, we made MRI markers, camera markers and a detection probe marker. To evaluate the accuracy of the image-guided system. we made a silicone phantom. Using the phantom and markers, we have performed MRI-guided experiments with a 1.5 Tesla MRI system. It has been verified from phantom experiments that our system has a positioning error less than 1.5%. Compared with other image guided surgery system, our system shows better positioning accuracy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.62-69
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• 2014

In this paper, WBAN(Wireless Body Area Network) On-body system using the surface-oriented antenna about the impact of human internal organs were analyzed through experiments. The received signal strength is measured for effect of human using the human model and the phantom of torso. Experiments are performed in anechoic chamber without moving and measured by Vector Network Analyzer. This paper confirms the effect of human body by comparing the human model and the phantom of torso. And also know the human internal organs effect on the antennas loss of received signal strength by measured data.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.35-40
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• 2000

In this paper, the relation between the radiated sound and the vibration due to piezoelectric ESWL(Extracorporeal Shock Wave Lithotripter) is examined and the results of the experiments are represented. Next, the relation between the focal point and the vibration of the objects is examined. The same experiments with the objects that can be broken are done and the relation between the vibration and the break efficiency of the phantom is experimentally investigated. These results show that the relativity between the power of the peak frequency and the break efficiency can be confirmed.