Geometric Features Detection of 3D Teeth Models using Approximate Curvatures (근사 곡률을 이용한 3차원 치아 모델의 기하학적 특징 검출)
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- The KIPS Transactions:PartA
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- v.10A no.2
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- pp.149-156
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- 2003
In the latest medical world, the attempt of reconstructing anatomical human body system using computer graphics technology awakes people's interests. Actually, this trial has been made in dentistry too. There are a lot of practicable technology fields using computer graphics in dentistry For example, 3D visualization and measurement of dental data, detection of implant location, surface reconstruction for restoring artificial teeth in prostheses and relocation of teeth in orthodontics can be applied. In this paper, we propose methods for definitely detecting the geometric features of teeth such as cusp, ridge, fissure and pit, which have been used as most important characteristics in dental applications. The proposed methods are based on the approximate curvatures that are measured on a 3D tooth model made by scanning an impression. We also give examples of the geometric features detected by using the proposed methods. Comparing to other traditional methods visually, the methods are very useful in detecting more accurate geometric features.
Purpose: It is generally believed that alopecia is caused by various factors such as scars, stress, genetical factors, androgens, etc. Androgenic alopecia is one of the most common cause of alopecia and found mainly in males. Propecia (Merck & Co., USA) and Minoxidil (McNEIL-PPC, Inc, USA) were the drugs approved from FDA for treatment of androgenic alopecia. Surgical treatments such as flap, tissue expansion, scalp reduction and hair transplantation can be considered if necessary. Hair micrograft techniques were developed for natural hair shapes and minimal adverse effect. There were attempts to measure the length of the forehead of the Korean young adults. However attempts to classify the shape and location of forehead hairline were rare. This study attempted to find out standard hairlines of young adults in their 20s & 30s and the result would be the guideline of the hairline in hair replacement surgery of male patients in their 40s & 50s. Methods: 200 male adults in 20s and 30s were photographed and measured the length of 11 vertical index lines to determine hairline. The indexes are the distances from hairline to intercanthal midpoint (A), to medial canthus (B), to upper eyelid fissure (C), to lower eyelid fissure (D), to lateral canthus (E) and distance from lateral highest point to medial lowest point, if the hairline is M-shape (F). Additionally, we classified the hairlines into 4 groups, M, horizontal, inverted U and irregular shapes. Results: The most common hairline of male adults in their 20s is inverted U-shape (53.3%), followed by horizontal-shape, M-shape, irregular-shape. In their 30s, inverted U-shape (59%) is followed by irregular-shape, M-shape, horizontal-shape. The M-shape is more frequently found in males in 30s than those in 20s. The mean values of the indexes in their 20s are as follows: A (76.14 mm), B (Rt: 75.78 mm, Lt:76.41 mm), C (Rt: 69.43 mm, Lt: 69.92 mm), D (Rt: 76.92 mm, Lt:77.46 mm), E (Rt: 64.16 mm, Lt: 64.73 mm), F (4.09 mm). Those in their 30s are as follows: A (76.13 mm), B (Rt: 76.114 mm, Lt: 76.02 mm), C (Rt: 69.87 mm, Lt: 70.37 mm), D (Rt: 77.37 mm, Lt: 77.58 mm), E (Rt: 69.63 mm, Lt: 69.85 mm), F (6.14 mm). Conclusion: The knowledge about human body measurement is indispensable to plastic surgeons. In this study, inverted U shape is the most common type of hairline in 30s, and similar distribution is found in 20s. The percentage of M shape in their 30s is elevated more than 10% compared to that in their 20s. The study of hairline shapes and 11 indexes of hairlines can be useful for planning of the hair transplantation and postoperative evaluation. This study being based on photogrammetry, there may be differences between actual distance of curved face and projected distance on flat photographs.
It is essential for living donor liver transplantation that surgeon must understand the hepatic vessel structure to improve the success rate of operation. In this paper, we extract the liver boundary without other surrounding structures such as heart, stomach, and spleen using the contrast enhanced MDCT liver image sequence. After that, we extract the major hepatic veins (left, middle, right hepatic vein) with morphological filter after review the basic structure of hepatic vessel which reside in segmented liver image region. The purpose of this study is provide the overall status of transplantation operation with size estimation of resection part which is dissected along with the middle hepatic vein. The method of liver extraction is as follows: firstly, we get rid of background and muscle layer with gray level distribution ratio from sampling process. secondly, the coincident images match with unit mesh image are unified with resulted image using the corse coordinate of liver and body. thirdly, we extract the final liver image after expanding and region filling. Using the segmented liver images, we extract the hepatic vessels with morphological filter and reversed the major hepatic vessels only with a results of ascending order of vessel size. The 3D reconstructed views of hepatic vessel are generated after applying the interpolation to provide the smooth view. These 3D view are used to estimate the dissection line after identify the middle hepatic vein. Finally, the volume of resection region is calculated and we can identify the possibility of successful transplantation operation.
Different biological tissues have different values of electrical resistivity. In EIT (electrical impedance tomography), we try to provide cross-sectional images of a resistivity distribution inside an electrically conducting subject such as the human body mainly for functional imaging. However, it is well known that the image reconstruction problem in EIT is ill-posed and the quality of a reconstructed image highly depends on the measurement error. This requires us to develop a high-performance EIT system. In this paper, we describe the development of a 16-channel digital EIT system including a single constant current source, 16 voltmeters, main controller, and PC. The system was designed and implemented using the FPGA-based digital technology. The current source injects 50KHz sinusoidal current with the THD (total harmonic distortion) of 0.0029% and amplitude stability of 0.022%. The single current source and switching circuit reduce the measurement error associated with imperfect matching of multiple current sources at the expense of a reduced data acquisition time. The digital voltmeter measuring the induced boundary voltage consists of a differential amplifier, ADC, and FPGA (field programmable gate array). The digital phase-sensitive demodulation technique was implemented in the voltmeter to maximize the SNR (signal-to-noise ratio). Experimental results of 16-channel digital voltmeters showed the SNR of 90dB. We used the developed EIT system to reconstruct resistivity images of a saline phantom containing banana objects. Based on the results, we suggest future improvements for a 64-channel muff-frequency EIT system for three-dimensional dynamic imaging of bio-impedance distributions inside the human body.
Purpose: Orbital bone is one of the most complex bones in the human body. When the patient has a fracture of the orbital bone, it is difficult for the surgeon to restore the fractured orbital bone to normal anatomic curvature because the orbital bone has complex curvature. We developed a rapid prototyping model based on a mirror image of the patient's 3D-CT (3 dimensional computed tomography) for accurate reduction of the fractured orbital wall. Methods: A total of 7 cases of large orbital wall fracture recieved absorbable plate prefabrication using rapid prototyping model during surgery and had the manufactured plate inserted in the fracture site. Results: There was no significant postoperative complication. One patient had persistent diplopia, but it was resolved completely after 5 weeks. Enophthalmos was improved in all patients. Conclusion: With long term follow-up, this new method of orbital wall reduction proved to be accurate, efficient and cost-effective, and we recommend this method for difficult large orbital wall fracture operations.
TMJ(TemporoMandibular Joint) is considered as the most important articulation in human body for maintaining the balance. Thus it is one of the main treatment areas in Chiropractic. Instead of Chiropractic treatment, NOSICK, a TMJ balancing device, can be used. As there is no such device to quantify the effect of NOSICK, a system was developed to measure the effect of NOSICK. This system is composed of stereo vision, infrared lights, and infrared through filter, etc. It requires optical markers for the measurement. 8 land markers were selected from the face which will show different displacement as NOSICK is applied. 11 test subjects were measured with the system developed with and without NOSICK applied. Quantifiable displacement of markers before and after applying NOSICK was successfully measured with the system developed.
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70