Risk factors of emergency reoperations

Background@#Emergency reoperation is considered to be a quality indicator in surgery. We analyzed the risk factors for emergency reoperations. @*Methods@#Patients who underwent emergency operations from January 1, 2017, to December 31, 2017, at our hospital were reviewed in this retrospective study. Multivariate logistic regression was performed for the perioperative risk factors for emergency reoperation. @*Results@#A total of 1,481 patients underwent emergency operations during the study period. Among them, 79 patients received emergency reoperations. The variables related to emergency reoperation included surgeries involving intracranial and intraoral lesions, highest mean arterial pressure ≥ 110 mmHg, highest heart rate ≥ 100 /min, anemia, duration of operation ＞120 min, and arrival from the intensive care unit (ICU). @*Conclusions@#The type of surgery, hemodynamics, hemoglobin values, the duration of surgery, and arrival from ICU were associated with emergency reoperations.

Measurement and Evaluation of Scatter Fractions for Digital Radiography with a Beam-Stop Array / 의학물리

Scatter radiation considerably affects radiographic image quality by reducing image contrast and contributing to a non-uniform background. Images containing a large portion of scatter radiation may result in an incorrect diagnosis. In the past few years, many efforts have been made to reduce the effects of scatter radiation on radiographic images. The purpose of this study is to accurately measure scatter fractions and evaluate the effectiveness of beam-stop arrays. To measure scatter fraction accurately, a beam-stop array and the SFC (Scatter Fraction Calculator) program were developed. Images were obtained using the beam-stop array for both an anti-scatter technique with an anti-scatter grid and an air gap technique. The scatter fractions of the images were measured using the SFC program. Scatter fractions obtained with an anti-scatter grid were evaluated and compared to scatter fractions obtained without an anti-scatter grid. Scatter fractions were also quantitatively measured and evaluated with an air gap technique. The effectiveness of the beam-stop array was demonstrated by quantifying scatter fractions under various conditions. The results showed that a beam-stop array and the SFC program can be used to accurately measure scatter fractions in radiographic images and can be applied for both developing scatter correction methods as well as systems.

Comparison Study of Image Quality of Direct and Indirect Conversion Digital Mammography System / 의학물리

The purpose of this study is to comprehensively compare and evaluate the characteristics of image quality for digital mammography systems which use a direct and indirect conversion detector. Three key metrics of image quality were evaluated for the direct and indirect conversion detector, the modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE), which describe the resolution, noise, and signal to noise performance, respectively. DQE was calculated by using a edge phantom for MTF determination according to IEC 62220-1-2 regulation. The contrast to noise ratio (CNR) was evaluated according to guidelines offered by the Korean Institute for Accreditation of Medical Image (KIAMI). As a result, the higher MTF and DQE was measured with direct conversion detector compared to indirect conversion detector all over spatial frequency. When the average glandular dose (AGD) was the same, direct conversion detector showed higher CNR value. The direct conversion detector which has higher DQE value all over spatial frequency would provide the potential benefits for both improved image quality and lower patient dose in digital mammography system.