• The Korean Journal of Nuclear Medicine
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• v.39 no.1
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• pp.57-68
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• 2005

Purpose: The objective of this study was to assess attenuation correction algorithms with the $^{137}Cs$ point source for the brain positron omission tomography (PET) imaging process. Materials & Methods: Four different types of phantoms were used in this study for testing various types of the attenuation correction techniques. Transmission data of a $^{137}Cs$ point source were acquired after infusing the emission source into phantoms and then the emission data were subsequently acquired in 3D acquisition mode. Scatter corrections were performed with a background tail-fitting algorithm. Emission data were then reconstructed using iterative reconstruction method with a measured (MAC), elliptical (ELAC), segmented (SAC) and remapping (RAC) attenuation correction, respectively. Reconstructed images were then both qualitatively and quantitatively assessed. In addition, reconstructed images of a normal subject were assessed by nuclear medicine physicians. Subtracted images were also compared. Results: ELEC, SAC, and RAC provided a uniform phantom image with less noise for a cylindrical phantom. In contrast, a decrease in intensity at the central portion of the attenuation map was noticed at the result of the MAC. Reconstructed images of Jaszack and Hoffan phantoms presented better quality with RAC and SAC. The attenuation of a skull on images of the normal subject was clearly noticed and the attenuation correction without considering the attenuation of the skull resulted in artificial defects on images of the brain. Conclusion: the complicated and improved attenuation correction methods were needed to obtain the better accuracy of the quantitative brain PET images.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.2
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• pp.118-126
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• 2006

In oral and maxillofacial surgery, bone graft is very important procedure for functional and esthetic reconstruction. So, many researcher studied about bone graft material like autogenous bone, allograft bone and artificial bone materials. The purpose of this study is to evaluate the quantity of bone generation induced by $Grafton^{(R)}$ graft, human allogenic demineralized bone matrix. Total 24 sites of artificial bony defects prepared using trephin bur(diameter 8 mm) on parietal bone of six adult New Zealand White rabbits. Experimental group had six defect sites which grafted $Grafton^{(R)}$(0.1 cc). Active control group had nine defect sites, into which fresh autogenous bone harvested from own parietal bone was grafted and passive control group had nine defect sites without bone graft. After six weeks postoperatively, the rabbits were sacrificed. The defects and surrounding tissue were harvested and decalcified in 10% EDTA, 10% foamic-acid. Specimens were stained with H&E. New bone area percentage in whole defect area was measured by IMT(VT) image analysis program. Quantity of bone by $Grafton^{(R)}$ graft was smaller than that of autograft and larger than that of empty defects. In histologic view $Grafton^{(R)}$ graft site and autograft site showed similar healing progress but it was observed that newly formed bone in active control group was more mature. In empty defect, quantity and thickness of new bone formation was smaller than in $Grafton^{(R)}$-grafted defect. $Grafton^{(R)}$ is supposed to be a useful bone graft material instead of autogenous bone if proper maintenance for graft material stability and enough healing time were obtained.

• The Journal of Art Theory & Practice
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• no.14
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• pp.7-32
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• 2012

The exhibition was started in 2010 in the New Acropolis Museum of Athens and embarked a journey since 2011 as a travelling exhibition inside Greece and abroad. The main purpose of the exhibition was to draw attention of the general public to the value of the 'rescue excavation' and of cultural heritage of Greece, by presenting the reconstruction bust of a girl whose skull was found in Kerameikos cemetery of ancient Athens. The new Kerameikos excavation was initiated by the construction of Metropolitan Railway lines in the center of Athens between 1992 to 1998. It revealed a pit of a mass burial where about 150 people were inhumed in a very hasty way without proper funeral rites or offerings. These bodies are identified as the victims of the infamous plague of Athens in the first years of the Peloponnesian War(430-426 BC). The epidemic disease killed almost one third of the city population including Pericles, and brought extreme fear and panic to the Athens society. The traditional funerary rites were totally disrupted, and the social decorum and the morality among the citizens became enfeebled. The plague and the civil war were the decisive factors to end the Golden Age of Democratic Athens. However, the exhibition organizers did not focus on the tragic aspect of this disaster and its casualties. Their main concern was to simplify the scholarly works of archaeological excavation and microchemistry analysis so that the exhibition viewers will easily understand and empathize the living value of the scholarly works of ancient Greek civilization. The centripetal element of the exhibition was the vivid face of an 11 years old ancient girl 'Myrtis', which was carefully reconstructed based on both the scientific data and artistic imagination. Also the set up of the exhibition was structured in order to stimuli cognitive and emotional experience of the visitors who witnessed the rebirth of a vibrant human being from an ancient debris. The museologists' continuous efforts to promote projects of contemporary artists, publications, and school programs related to the exhibition indicate that the ulterior motive of this exhibition is the cultural education of the present and future generation through the intimate experiences of ancient Greek life. Also this is the reason why the various museums that held the travelling exhibition try to make the presentation as a gesture of memorial service for an anonymous Athenian girl who deceased circa 2400 years ago. The pragmatic efforts of Greek scholars and museologists through exhibition show us a way to find a solution to the continuous threat of cultural resources by massive construction projects and land development, and to overcome public indifference to the history and cultural heritage.

• The korean journal of orthodontics
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• v.51 no.6
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• pp.366-374
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• 2021

Objective: This study investigated the impact of a single piezocision in the maxillary alveolar process on the speed of tooth movement. The null hypothesis was that the speed of tooth movement will be equal with and without piezocision. Methods: All maxillary molars on one side were moved against the combined incisors in 10 ten-week-old male Wistar rats. Under general anesthesia, a force of 25 cN was applied on either side using a Sentalloy closed coil spring. After placing the orthodontic appliance, vertical corticision was performed using a piezotome under local anesthesia, 2 mm mesial from the mesial root of the first molar on a randomly selected side; the other side served as the control. At the beginning of the treatment, and 2 and 4 weeks later, skull micro-computed tomography was performed. After image reconstruction, the distance between the mesial root of the first molar and the incisive canal, and the length of the mesial root of the first maxillary molar were measured. Moreover, the root resorption score was determined as described by Lu et al. Results: Significantly higher speed of tooth movement was observed on the corticision side; thus, the null hypothesis was rejected. The loss of root length and root resorption score were significantly more pronounced after piezocision than before. A strong correlation was observed between the speed of tooth movement and root resorption on the surgical side, but the control side only showed a weak correlation. Conclusions: Piezocision accelerates orthodontic tooth movement and causes increased root resorption.