Dosimetric comparison of different intensity-modulated radiotherapy techniques for whole-breast irradiation of right-breast cancer.

PURPOSE: This study compared the dosimetric parameters of field-in-field forward intensity-modulated radiotherapy (FIF-IMRT) and fixed-field inversely optimized intensity-modulated radiotherapy (FFIO-IMRT) for the whole-breast irradiation of patients undergoing right-breast lumpectomy. MATERIAL AND METHODS: A total of 30 patients with pT1-2N0M0 right-breast invasive ductal carcinoma were enrolled in this study. Two different treatment plans, i.e., FIF-IMRT and FFIO-IMRT, were designed for each patient. The dosimetric parameters of the two treatment plans were compared including ipsilateral lung and heart, conformity index (CI), and the homogeneity index (HI) of the planning target volume (PTV). RESULTS: Fixed-field inversely optimized intensity-modulated radiotherapy was found to significantly improve CI (83.302% vs. 60.146%) and HI (11.837% vs. 19.280%), and significantly reduced V25 (18.038% vs. 19.653%) and V30 (15.790% vs. 18.492%) of the ipsilateral lung. It also significantly increased V5 (69.791% vs. 32.615%) of the ipsilateral lung and V5 (61.579% vs. 3.829%), V10 (14.130% vs. 0.381%), V20 (1.843% vs. 0.051%), and Dmean (5.211Gy vs. 1.870Gy) of the heart. CONCLUSION: Regardless of improving the conformity and homogeneity of PTV and reducing the ipsilateral lung irradiation volume at high doses, FFIO-IMRT significantly raised the ipsilateral lung irradiated volume at low doses, as well as the irradiation volume and mean radiation doses to the heart. This limits its use in patients with early-stage right breast cancer.

Positioning error analysis of the fraxion localization system in the intracranial stereotactic radiotherapy of tumors.

OBJECTIVE: To investigate positioning error analysis of the Fraxion localization system in the intracranial stereotactic radiotherapy of tumors. METHODS: 64 patients were divided into two groups: a control group (36 patients with the standard thermoplastic mask) and a model group (28 patients with the Fraxion localization system). 3D images of the treated position were obtained by cone-beam computed tomography (CBCT). Positioning errors were obtained by, respectively, registering these two sets of CBCT images to planning CT images, using a 6°-freedom robotic patient positioning system (HexaPOD Evo RT System). The changes in positioning errors with the Fraxion localization system and with the standard thermoplastic mask were analyzed. RESULTS: CBCT scan results of the model group showed that the mean of linear error of three directions [superior-inferior (SI), lateral (LAT), and anterior-posterior (AP)] was 0.710 ± 0.676 mm, 0.817 ± 0.687 mm, and 0.710 ± 0.685 mm, respectively. The corresponding PTV was 1.23 mm, 1.26 mm, and 1.36 mm. The differences between the 3D images and the planned CT images were significant (p < 0.001). CONCLUSION: The Fraxion radiotherapy system can not only improve the positioning accuracy and reduce positioning errors but also narrow the PTV margin and reduce the radiated volume of normal tissue.

Serological evidence for exposure to bovine viral diarrhoea virus in sheep co-grazed with beef cattle in New Zealand.

Aims: To determine whether sheep that co-grazed with cattle that were suspected to be positive for bovine viral diarrhoea (BVD) virus had serological evidence of exposure to the virus.Methods: Eighteen commercial farms that routinely co-grazed cattle and sheep in the same paddocks were recruited through purposive sampling. The recruiting veterinarians identified nine farms with cattle herds that were known or highly suspected to be positive for BVD and nine farms that were considered to be free of BVD. Blood samples were taken from 15 ewes aged 1 year on each farm and samples were submitted to a commercial diagnostic laboratory to test for antibodies against pestiviruses using an ELISA. All samples that were positive were then tested using a virus neutralisation test (VNT)for antibodies against BVD virus.Results: Of the 270 blood samples, 17 were positive for pestivirus antibodies by ELISA and these originated from two farms that were known or suspected to have BVD virus-positive cattle. None of the samples from the nine flocks co-grazed with cattle herds that were known or suspected to be BVD virus-negative were positive for pestivirus antibodies. Within the two positive farms, 2/15 samples from the first farm and 15/15 samples from the second farm were antibody-positive. When the 17 positive blood samples were submitted for VNT, all 15 samples from the second farm tested positive for BVD virus antibodies with the highest titre being 1:512.Conclusions and clinical relevance: In this small sample of New Zealand sheep and beef farms with suspected BVD infection in cattle, there was evidence of pestivirus exposure in co-grazed sheep. Although we were unable to confirm the origin of the exposure in these sheep, these findings highlight that farmers who are trying to eradicate BVD from their cattle should be mindful that the infection may also be circulating in sheep, and both populations should be considered a possible risk to each other for generating transient and persistent infections. Further work is needed to estimate the true prevalence of New Zealand sheep flocks that are affected by BVD and the associated economic impacts.

Practices and opinions of New Zealand beef cattle farmers towards bovine viral diarrhoea control in relation to real and perceived herd serological status.

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status.Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control.Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only.Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options.

Assessing the use of diagnostic laboratory accession data to support national bovine viral diarrhoea control in New Zealand.

Aims: To assess the suitability of using existing national diagnostic laboratory testing data to support national bovine viral diarrhoea (BVD) research, surveillance, and control in New Zealand. Methods: Data on laboratory accessions for BVD diagnostic testing in New Zealand from 1 January 2015 to 31 December 2017 were provided by four commercial veterinary diagnostic companies. The data were integrated into a single dataset containing the unique accession number, sample submission date, farm location (territorial authority level), test type (bulk milk antibody-ELISA, bulk milk PCR, serum antibody-ELISA, blood/serum/tissue antigen-ELISA, or blood/serum/tissue PCR), and test results. Estimates for the number of registered cattle farms in each territorial authority were generated from the National Animal Identification and Tracing database. Results were summarised for July 2015 to June 2016 and July 2016 to June 2017. Results: There was a total of 59,007 unique BVD diagnostic test accessions including 39,920 (67.6%) for bulk milk antibody-ELISA, 27,832 (47.2%) for bulk milk PCR, 3,229 (5.5%) for serum antibody-ELISA, 9,132 (15.5%) for blood/serum/tissue antigen-ELISA, and 7,122 (12.1%) for blood/serum/tissue PCR. Of the 17,946 accessions for blood/serum/tissue samples, 4,316 (24.0%) were missing the herd production type and 6,678 (37.2%) were missing the animals age. Approximately 7,000/10,958 (65%) dairy herds and 1,600/43,611 (4%) beef herds were conducting annual BVD screening tests. In 2016/2017, the prevalence of accessions with ≥1 BVD-positive result was 40.6% for bulk milk antibody, 6.4% for bulk milk PCR, 45.6% for serum antibody, and 9.8% for blood/serum/tissue antigen-ELISA or PCR tests. There was substantial regional variation in both the percentage of herds testing for BVD and the prevalence of positive accessions. Following pooled serum antibody-ELISA, only 175/604 (29.0%) beef herds and 177/566 (31.3%) dairy herds had recorded follow-up testing. Conclusions and Clinical Relevance: Laboratory diagnostic accession data has the potential to provide valuable insights about BVD epidemiology in New Zealand, but there are significant limitations in the data collected and discrepancies in the different systems that each laboratory uses to measure, interpret, and record diagnostic data. There is a strong need to develop a more consistent national system for recording and sharing BVD test results to support BVD management at farm and industry levels. Abbreviations: BVD: Bovine viral diarrhoea; Ct: Cycle threshold; NAIT: National Animal Identification and Tracing; NZVP: New Zealand Veterinary Pathology; PI: Persistently infected; S/P: Sample to positive control.

Elimination of bovine viral diarrhoea virus in New Zealand: a review of research progress and future directions.

The major impacts of bovine viral diarrhoea (BVD) on cattle health and production have prompted many countries to embark on national elimination programmes. These programmes typically involve identifying and removing persistently infected (PI) cattle in infected herds and implementing biosecurity measures, such as pre- or post-movement testing. In order to design a systematic national control programme to eliminate BVD in New Zealand, which achieves the greatest benefits to the industries at the lowest cost to individual farmers, an accurate understanding is necessary of the epidemiology, economics and social motivation for BVD control in New Zealand. In this article we briefly review the pathogenesis of BVD, transmission and diagnosis of BVD virus infection, and effectiveness of vaccination. We summarise the current state of knowledge of the prevalence, risk factors for transmission, and financial impacts of BVD in New Zealand. We describe control programmes in Europe and then discuss the challenges that must be addressed to design a cost-effective national control programme to eliminate BVD in New Zealand.

Flow-through microfluidic immunosensors with refractive index-matched silica monoliths as volumetric optical detection elements.

A sensitive and rapid absorbance based immunosensor that utilizes ex situ functionalized porous silica monoliths as volumetric optical detection elements is demonstrated in this study. The porous monolith structure facilitates high capture probe density and short diffusion length scales, enabling sensitive and rapid assays. Silica monoliths, synthesized and functionalized with immunocapture probes off-chip before integration into a sealed thermoplastic microfluidic device, serve to capture target antigens during perfusion through the porous structure. Gold nanoparticle immunoconjugates are combined with silver enhancement to create microscale silver clusters, followed by perfusion of an aqueous sucrose solution to limit light scattering and enhance optical signal. Using this approach, detection limits as low as 1 ng/mL are achieved for a sandwich assay, with a dynamic range of at least 4 logs. The results confirm that the combination of on-chip index matching with functionalized porous silica monoliths can enables simple and practical flow-through immunoassays for the sensitive and rapid detection of target antigens.

Ultra-power-efficient 2 × 2 Si Mach-Zehnder interferometer optical switch based on III-V/Si hybrid MOS phase shifter.

We have demonstrated an ultra-power-efficient 2 × 2 Si Mach-Zehnder interferometer optical switch with III-V/Si hybrid metal-oxide-semiconductor (MOS) phase shifters. The efficient low-loss phase modulation enables low-crosstalk and broadband switching in conjunction with multimode interference couplers consisting of tapered input and output ports. Owing to the negligible gate leakage current in the hybrid MOS capacitor, the power consumption required for switching is 0.18 nW, approximately 107 times smaller than that of a Si thermo-optic phase shifter. We also demonstrated a switching time of less than 20 ns. The III-V/Si hybrid MOS phase shifter is promising for fabricating large-scale Si photonic integrated circuits that require efficient, low-loss, and high-speed optical phase control.

Successful Treatment of a Patient With Diffuse Portosplenomesenteric Thrombosis Using a Pericholedochal Varix for Portal Flow Reconstruction During Deceased Donor Liver Transplantation: A Case Report.

Portal vein thrombosis remains a challenging issue in liver transplantation. When thrombectomy is not feasible due to diffuse portosplenomesenteric thrombosis, other modalities are adapted such as the use of a jump graft or portal tributaries or even multivisceral transplantation. For patients with diffuse thrombosis of the splanchnic venous system, a large pericholedochal varix can be a useful vessel for providing splanchnic blood flow to the graft and for relieving portal hypertension. We report our experience of successfully treating a patient with diffuse portosplenomesenteric thrombosis using a pericholedochal varix for portal flow reconstruction during deceased donor liver transplantation and eventually preventing unnecessary multivisceral transplantation. A 56-year-old man diagnosed with liver cirrhosis due to hepatitis B underwent deceased donor liver transplantation due to refractory ascites. Preoperative imaging revealed diffuse portosplenomesenteric thrombosis with large amount of ascites. During the operation, dissection of the main portal vein was not possible due to the development of multiple large pericholedochal varices and cavernous change of the main portal vein. After outflow reconstruction, portal inflow was restored by anastomosing the graft portal vein to a large pericholedochal varix. Postoperatively, although abdominal computed tomography scan showed stenosis of portal vein anastomosis site, liver function tests improved, and Doppler sonogram revealed no flow disturbance. During follow-up, the patient repeatedly developed hydrothorax and ascites. In addition, stenosis of the portal vein anastomosis and thrombosis of the portomesenteric system still remained. The patient underwent transhepatic portal vein stent insertion. After portal vein stent insertion, hydrothorax and ascites improved and the extent of thrombosis of the portomesenteric system decreased without anticoagulation therapy. In conclusion, enlarged pericholedochal varix in patients with totally obliterated splanchnic veins can be a source of useful inflow to restore portal flow and decrease the extent of thrombosis, thereby preventing unnecessary multivisceral transplantation.

Liquid culture enhances diagnosis of patients with milder forms of non-tuberculous mycobacterial lung disease.

OBJECTIVE: To evaluate the proportion and clinical characteristics of patients with non-tuberculous mycobacteria (NTM) lung disease diagnosed based on positive culture results in liquid medium only. METHODS: We reviewed the medical records of 978 patients diagnosed with NTM lung disease. All clinical samples were cultured in both solid and liquid media. RESULTS: Of the 978 patients, 111 (11.3%) were culture-positive in liquid medium only (liquid culture group), and 867 (88.7%) (solid culture group) on solid medium, regardless of the culture results in liquid medium. At the time of diagnosis, the liquid culture group was less likely than the solid culture group to have haemoptysis (11.7% vs. 20.0%, P = 0.04), positive sputum smear for acid-fast bacilli (14.4% vs. 50.2%, P < 0.001) or the fibrocavitary form of NTM lung disease (3.6% vs. 14.6%, P = 0.001). During the median follow-up period of 28.9 months (interquartile range 19.1-41.6), the proportion of patients requiring antibiotic treatment was lower in the liquid culture group than in the solid culture group (44.1% vs. 61.6%, P < 0.001). CONCLUSIONS: Liquid media culture is helpful in the diagnosis of patients with less severe forms of NTM lung disease.

Factors Delaying Organ Procurement After Declaration of Brain Death in Korea.

BACKGROUND: Organ donation after brain death is a major source for obtaining transplantable organs for patients with end-stage organ disease. However, the time from declaring brain death to organ procurement is often longer than expected. Analyzing factors that delay organ procurement may help to prevent damage to organs from marginal and unstable donors and aid in preparation for recipient operation. The aim of this study was to examine factors associated with the interval between the time of declaring brain death and organ procurement. METHODS: Medical records of patients who underwent organ procurement after brain death from February 2009 to April 2015 were retrospectively reviewed. RESULTS: Of the 77 patients which were scheduled to undergo organ procurement, 68 eventually underwent procurement of ≥1 organ. The average time interval from 1st exam for brain death to organ procurement decreased from 1,248 minutes in 2009 to 910 minutes in 2015. Although not statistically significant, during the 6-year period, the time interval decreased from 1,105 minutes to 1,075 minutes in the latter half of the period (P = .623). Organ procurement was extensively delayed most commonly owing to false negative electroencephalogram (EEG; 62.5%). CONCLUSIONS: With increasing experience in dealing with brain death donors, the time interval from declaring brain death to organ procurement decreased. We suggest that an EEG be performed during the initial stages of examination for brain death to prevent unnecessary preparation of recipient operation owing to a false EEG test.

Voluntary exercise prior to traumatic brain injury alters miRNA expression in the injured mouse cerebral cortex

MicroRNAs (miRNAs) may be important mediators of the profound molecular and cellular changes that occur after traumatic brain injury (TBI). However, the changes and possible roles of miRNAs induced by voluntary exercise prior to TBI are still not known. In this report, the microarray method was used to demonstrate alterations in miRNA expression levels in the cerebral cortex of TBI mice that were pretrained on a running wheel (RW). Voluntary RW exercise prior to TBI: i) significantly decreased the mortality rate and improved the recovery of the righting reflex in TBI mice, and ii) differentially changed the levels of several miRNAs, upregulating some and downregulating others. Furthermore, we revealed global upregulation of miR-21, miR-92a, and miR-874 and downregulation of miR-138, let-7c, and miR-124 expression among the sham-non-runner, TBI-non-runner, and TBI-runner groups. Quantitative reverse transcription polymerase chain reaction data (RT-qPCR) indicated good consistency with the microarray results. Our microarray-based analysis of miRNA expression in mice cerebral cortex after TBI revealed that some miRNAs such as miR-21, miR-92a, miR-874, miR-138, let-7c, and miR-124 could be involved in the prevention and protection afforded by voluntary exercise in a TBI model.

Historical trend in heavy metal pollution in core sediments from the Masan Bay, Korea.

The spatiotemporal distribution and their mass accumulation rate (MAR) of heavy metals were investigated to evaluate the time-dependent historical trends of heavy metal concentration. The three short cores used for this study were collected from the catchment area (MS-PC5, 60cm length), the central part (MS-PC4, 40cm length) and the offshore (MS-PC2, 60cm length) of the Masan Bay, Korea. The concentration of heavy metals (Co, Ni, Cu, Zn, Cr and Pb) in catchment area is as much as 1.5-2 times higher than central part of the Bay, and about 2 times higher than offshore area approximately. In particular, MAR of metals (Cu, Zn and Pb) show clear spatiotemporal variation, so that MAR's of heavy metal may provide more accurate information in evaluating the degree of pollution. Temporally, the heavy metal concentration had been increased since the late 1970s, but it seems to decrease again since the 2004yr in catchment area. This may came from concentrated efforts for the government to reduce industrial waste release.

Tumor cell-activated CARD9 signaling contributes to metastasis-associated macrophage polarization.

Macrophages are critical immune effector cells of the tumor microenvironment that promote seeding, extravasation and persistent growth of tumor cells in primary tumors and metastatic sites. Tumor progression and metastasis are affected by dynamic changes in the specific phenotypes of macrophage subpopulations; however, the mechanisms by which tumor cells modulate macrophage polarization remain incompletely understood. Caspase recruitment domain-containing protein 9 (CARD9) is a central adaptor protein of innate immune responses to extracellular pathogens. We report that increased CARD9 expression is primarily localized in infiltrated macrophages and significantly associated with advanced histopathologic stage and the presence of metastasis. Using CARD9-deficient (CARD9(-/-)) mice, we show that bone marrow-derived CARD9 promotes liver metastasis of colon carcinoma cells. Mechanistic studies reveal that CARD9 contributes to tumor metastasis by promoting metastasis-associated macrophage polarization through activation of the nuclear factor-kappa B signaling pathway. We further demonstrate that tumor cell-secreted vascular endothelial growth factor facilitates spleen tyrosine kinase activation in macrophages, which is necessary for formation of the CARD9-B-cell lymphoma/leukemia 10-mucosa-associated lymphoid tissue lymphoma translocation protein 1 complex. Taken together, our results indicating that CARD9 is a regulator of metastasis-associated macrophages will lead to new insights into evolution of the microenvironments supporting tumor metastasis, thereby providing targets for anticancer therapies.

Bacterial diversity in the indoor air of pharmaceutical environment.

AIMS: To monitor bacterial diversity of ISO Class 8 pharmaceutical clean room environment using conventional culture-based methods and pyrosequencing analysis. METHODS AND RESULTS: Bacterial isolates were obtained through viable particulate air monitoring, passive air monitoring and surface-monitoring procedures. A total of 157 bacterial isolates were obtained and assigned to four different phyla, Actinobacteria, Firmicutes, Proteobacteria and Deinococcus-Thermus, encompassing 52 species of 24 genera based on 16S rRNA gene sequence analysis. The genera Micrococcus and Staphylococcus were found as the main bacterial groups among the isolates. However, a big discrepancy was found between the culture based and pyrosequencing results. A total of 11 409 quality reads were obtained from the pyrosequencing analysis, and the subsequent phylogenetic analysis indicated that Proteobacteria was the most abundant group at phylum level, followed by Actinobacteria and Firmicutes. Bacillus, Propionibacterium and Acinetobacter were identified as the most abundant genera by the pyrosequencing analysis. CONCLUSIONS: The culture-based results were in line with previous reports on the airborne bacterial composition of various environments, but the pyrosequencing analysis revealed a unique diversity of bacteria in this case. No significant pathogens above Riskgroup 2 were found from either culture based or pyrosequencing studies. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of various bacterial taxa including a number of groups, whose presence in air is previously unknown, was confirmed through this analysis. The main source of bacteria in the indoor air environment of pharmaceutical processes is likely human, but no significant primary pathogens were detected. Culture-based analysis may give limited information on the bacterial diversity of air environment.

Investigation of gold-coated bare fiber probe for in situ intra-vitreous coherence domain optical imaging and sensing.

We have investigated the usage of gold-plated bare fiber probes for in situ imaging of retinal layers and surrounding ocular tissues using time-domain common-path optical coherence tomography. The fabricated intra-vitreous gold-plated micro-fiber probe can be fully integrated with surgical tools working in close proximity to the tissue to provide subsurface images having a self-contained reference plane independent to the Fresnel reflection between the distal end of the probe and the following medium for achieving reference in typical common-path optical coherence tomography. We have fully characterized the probe in an aqueous medium equivalent to the vitreous humor in the eye and were able to differentiate various functional retinal tissue layers whose thickness is larger than the system's resolution.

Prevalence of hepatic parasites in Korean wild rats (Rattus norvegicus) and their association with pulmonary arteriolar medial hypertrophy.

C hepatica, an important zoonotic parasite, and C fasciolaris are common parasites in rodents. In rodent livers, C hepatica causes sequential morphologic changes that are designated as early, intermediate, or late phase, and C fasciolaris forms cysts surrounded by fibroplasia and granulomatous inflammation. The present study describes the prevalence of these parasites and associated liver and lung lesions in wild rats (Rattus norvegicus) living around pig farms in South Korea. Selected parenchymal organs, including liver and lung, of 89 wild rats were examined. Of 89 rats, 28 (31.5%) were infected with either C hepatica or C fasciolaris or with both parasites. Severe medial hypertrophy of small arterioles was observed in the lungs of 11 of the 28 parasite-infected rats (P < .01). The pulmonary arteriolar hypertrophy in the rats infected with C hepatica was strongly associated with early and/or intermediate phases (88.8%) of morphologic change in the livers (P < .01). As such, this report is the first to suggest a significant association between parasite-induced hepatitis and pulmonary arteriolar hypertrophy in rodents. Further studies are warranted for the use of C hepatica-infected rats as an animal model to explore the underlying mechanisms of portopulmonary hypertension in humans.

Common path optical coherence tomography with fibre bundle probe.

A simple common path optical coherence tomography using a fibre optic bundle as a probe is demonstrated experimentally. The mechanical lateral scans are accomplished outside the specimen, proximal entrance of the fibre bundle, which eliminated the need for moving parts in the distal end of the probe. This feature allows the probe to be made submillimetre in size and easily integrated into surgical tools for intraoperative imaging. The axial and lateral resolutions of the system, and preliminary images of phantom samples, are reported.

The pattern and prevalence of hypodontia in Koreans.

OBJECTIVE: The objective of this study was to evaluate the pattern and prevalence of hypodontia in the Korean population along with its association with the dental and skeletal polymorphisms. SUBJECTS AND MATERIALS: The diagnostic materials including casts, panoramic radiographs, and lateral cephalograms of 1622 Korean subjects (611 males, 1011 females) were used to evaluate the pattern and prevalence of hypodontia as well as its association with the congenital absence of the third molar. The changes in the tooth size and skeletal characteristics of the hypodontia group were evaluated using cast/cephalometric analysis and compared with the standard values of normal occlusion in Koreans. RESULTS: The prevalence of hypodontia in Koreans was 11.2%. The mandibular lateral incisor and second premolar were the most frequently absent. Congenital absence of the third molar was observed more frequently in the hypodontia group than in the non-hypodontia group. The prevalence of hypodontia in Class III malocclusion was significantly higher than in Class I or Class II malocclusion. CONCLUSION: The pattern and prevalence of hypodontia can vary in different ethnic groups. In Koreans, the special features of hypodontia were its association with a higher level of congenital missing third molars and skeletal Class III malocclusion.