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Perspectives on Acute Hepatitis A Control in Korea
강성희,김문영,백순구 대한의학회 2019 Journal of Korean medical science Vol.34 No.36
Until 1995, the incidence of symptomatic acute hepatitis A was minimal and there were no cases of national outbreak in Korea. However, there was a nationwide outbreak of hepatitis A that peaked in 2009. In 2019, a total of 10,083 cases of acute hepatitis A were reported for seven months of the year according to the Korea Center for Disease Control and Prevention. This may be attributed to the proportion of susceptible subjects in the Korean population, as about 10 years have passed since herd immunity was induced by the epidemic occurring during the late 2000s. Recent studies have shown that the rate of seropositivity for anti- hepatitis A virus antibodies (anti-HAV) is the lowest in adults in their 20s and has not changed much over the past 10 years, and seropositivity of anti-HAV in adults in their 30s has continued to decline from 69.6% in 2005 to 32.4% in 2014. Most young adults who have not yet experienced hepatitis A and are not vaccinated are vulnerable to hepatitis A infection. This year's epidemic of hepatitis A is a predictable outcome for vulnerable populations. Therefore, effective acute hepatitis A control and prevention strategies are needed, particularly for those in their 20s and 30s.
Possibility of Interchanging Patients for Beam-Matched Linear Accelerators from the Same Vendor
강성희,정진범,엄근용,송창훈,김인아,김재성,김연래,강상원,김경현,서태석 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.8
The purpose of this study is to investigate the possibility of interchanging patients on beam-matched linear accelerators (linacs), by evaluating the dosimetric variation and the dose delivery accuracy of volumetric modulated arc therapy (VMAT). Two VitalBeam linacs installed recently in our center were included in this study. For dosimetric data comparison, beam data, such as percentage depth doses (PDDs), beam profiles, output factors, multi-leaf collimator (MLC) leaf transmission factors, and the dosimetric leaf gap (DLG), for 6-MV and 10-MV beams were measured on both linacs. Sixty patients (20 head and neck, 20 lung, and 20 prostate cancers) were selected to evaluate the dosimetric parameters and the delivery accuracy of the VMAT plans created for various treatment sites. All the VMAT plans were generated using the Eclipse treatment planning system (TPS) with the same optimizer algorithm. The dose differences between two beam-matched linacs for planning target volumes (PTVs) and organs at risk (OARs) were recorded and analyzed. Patient-specific dosimetric quality assurance (DQA) using the Electronic Portal Image Device (EPID) were performed, and the measured planar doses were compared with those calculated by using the TPS though absolute dose gamma evaluation using 2%/2 mm and 2%/3 mm criteria. The differences in all dosimetric beam data between the two beam-matched linacs were all within 1% for the 6-MV and the 10-MV beams. For all 60 cases of three treatment sites, no notable differences were observed in the dosimetric comparison and the DVH variation between the beam-matched linacs. The average differences in dosimetric parameters of PTV and OARs were all within 1%. Furthermore, all passing rates of measured doses on the beam-matched linacs were higher than 93% and 97% for the 2%/2 mm and the 2%/3 mm criteria, respectively. Our overall dosimetric variation in beam data and VMAT plans remains within the tolerance of clinical acceptability. Pretreatment verification results were also clinically acceptable, showing good agreement with the calculated doses. Therefore, this study demonstrated the possibility of swapping patients in a VMAT plan without any modification and re-planning between two beam-matched linacs.
The Impact of Sarcopenia and Its Rate of Change on Prognostic Value of Liver Cirrhosi
강성희,김문영,백순구 대한의학회 2018 Journal of Korean medical science Vol.33 No.50
Sarcopenia is a syndrome characterized by skeletal muscle loss with aging, which is prevalent in adults with cancer and those with chronic comorbidities such as liver cirrhosis.1 The prevalence of concomitant sarcopenia is reported to be > 40% in cirrhosis.2 Sarcopenia has emerged as an important and novel prognostic predictor in a variety of clinical conditions. Several studies have reported that sarcopenia is associated with a poor prognosis, as well as reduced survival, before and after liver transplantation. Moreover, the model for end-stage liver disease (MELD)—sarcopenia score, which combines MELD score and the psoas muscle area score, was found to be better than the MELD scores in predicting waiting-list mortality, and its predictive value was found to be superior to that of the MELD score in several studies.3 However, there were few studies that performed repeat skeletal muscle area measurements using serial imaging. Then, it is not known whether the rate of skeletal muscle depletion is associated with a poor prognosis in patients with liver cirrhosis.
강성희,정진범,송창훈,엄근용,김인아,김재성,서태석 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.4
The purpose of this study is to evaluate the performance of a \stealth chamber" as a novel reference detector for measuring the commissioning beam data for a wedge eld. The stealth chamber is a transmission ionization chamber intended to be used as a reference chamber for relative dosimetry. The percentage depth doses (PDDs) and the dose proles of 6-, 8-, and 10-MV photon beams of four wedge lters were measured using the stealth and the CC13 chambers as reference detectors. The PDD and the prole measurements were performed under various eld sizes ranging from 4 4 cm2 to 20 20 cm2. For the evaluate of the performance of the stealth chamber in elds with a physical wedge, all measurement data obtained using the stealth chamber as a reference detector were compared with those measured using two CC13 chambers as both eld and reference detectors. For the PDDs, the dierences in dosimetric parameters such as the depth of maximum dose (dmax) and the PDD at 10 cm (D10) and 5 cm (D5) were analyzed for both reference detectors. In addition, the root-mean-square error (RMSE) was calculated to measure the agreement of the proles at dmax and a 10 cm depth. The percentage dierences in D10 and D5 between both detectors were less than 1% for all energies and elds with four wedges. Furthermore, the RMSEs of the proles at dmax and 10-cm depth in both chambers were within 1% for all energies and elds except for the 60 wedge angle. This study found that the use of a stealth chamber to measure the commissioning beam data for a wedge eld is feasible, although a relatively large dierence in the PDD was observed in the build-up region. However, we recommend careful verication of the PDDs and dose proles for large eld size and wedge angle before clinical use.