• Progress in Medical Physics
• /
• v.17 no.1
• /
• pp.32-39
• /
• 2006

To assess the ability of an extravasation detection accessory (EDA) system to detect clinically important extravascular injection of iodinated contrast material delivered with an automated power injector. Fifty patients referred for contrast material enhanced body computed tomography studied in a prospective, observation study in which the EDA system was used to identify and interrupt any injection associated with clinically Important extravasation. The presence or absence of extravasation was definitively established with multi-detector CT at the injection site (injection rate, $2.0{\sim}2.5$ mL/sec). There were two true positive, extravasation volumes $22{\sim}25$ mL. The EDA system had sensitivity in the detection of clinically important extravasation. The EDA system is easy to use, safe, and accurate In the monitoring of intravenous injections for extravasation, which may prove especially useful in CT applications.

• Journal of radiological science and technology
• /
• v.29 no.1
• /
• pp.13-19
• /
• 2006

The PET scanner can detect the photon pair arriving from the source in phantom. The number of light photons released by the crystal(scintillator-BGO or LSO). In recent scintillation crystals in block structures were incorporated into full ring systems, and their resulted marked improvement in spatial resolution and increase in a sensitivity to annihilations. The uniformity of the crystal sensitivity is very important to makes correct information of abnormal states in organs. These factors influenced by the dection efficiency of the scintillators. We have study about the uniformity of crystals to the annihilation, And study about the standard deviation to average counts. The relative standard deviation in central detector groups more uniformed than circumferenced detector groups. It is caused detected quanta of gamma ray by the geometrical factors of PET detector. PET cameras are available with different geometric arrangement and several parallel rings oriented in the axial direction. The center groups from 7th to 40th groups are comparatively uniform and sensitive. But at the circumferenced detectors decreased the sensitivity and uniformity.

• Journal of Radiation Protection and Research
• /
• v.37 no.2
• /
• pp.84-89
• /
• 2012

The purpose of this study was to compare radiation dose and image quality between low-dose (LDP) and standard-dose protocol (SDP). LDP (120 kVp, 30 mAs, 2-mm thickness) and SDP (120 kVp, 180 mAs, 1.2-mm thickness) images obtained from 61 subjects were retrospectively evaluated at level of carina bifurcation, using multi-detector CT (Brilliance 16, Philips Medical Systems). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated at ascending aorta and infraspinatus muscle, from CT number and back-ground noise. Radiation dose from two protocols measured at 5-point using acrylic-phantom, and CT number and noise measured at 4-point using water-phantom. All statistical analysis were performed using SPSS 19.0 program. LDP images showed significantly more noise and a significantly lower SNR and CNR than did SDP images at ascending aorta and infraspinatus muscle. Noise, SNR and CNR were significantly correlated with body mass index (p<0.001). Radiation dose, SNR and CNR from phantom were significant differences between two protocols. LDP showed a significant reduction of radiation dose with a significant change in SNR and CNR compared with SDP. Therefore, exposure dose on LDP in clinical applications needs resetting highly more considering image quality.

• Imaging Science in Dentistry
• /
• v.43 no.2
• /
• pp.63-69
• /
• 2013

After over one decade development, cone beam computed tomography (CBCT) has been widely accepted for clinical application in almost every field of dentistry. Meanwhile, the radiation dose of CBCT to patient has also caused broad concern. According to the literature, the effective radiation doses of CBCTs in nowadays market fall into a considerably wide range that is from $19{\mu}Sv$ to $1073{\mu}Sv$ and closely related to the imaging detector, field of view, and voxel sizes used for scanning. To deeply understand the potential risk from CBCT, this report also reviewed the effective doses from literatures on intra-oral radiograph, panoramic radiograph, lateral and posteroanterior cephalometric radiograph, multi-slice CT, and so on. The protection effect of thyroid collar and leaded glasses were also reviewed.

• The Korean Journal of Pain
• /
• v.27 no.3
• /
• pp.266-270
• /
• 2014

Background: Knowledge of the anatomical variation of the vertebral artery has clinical importance not only for the performance of interventional or surgical procedures itself but also to ensure their safety. We conducted a study of the anatomical variation by reviewing multi-detector computed tomography (MDCT) images of the cervical spine from 460 Korean patients. Methods: 16-row MDCT data from 460 patients were used in this study. We observed 920 vertebral arteries. Examination points included level of entrance of the artery into the transverse foramen of the cervical vertebra, origin site of the vertebral artery, course of a vertebral artery with aberrant entrance. Result: The vertebral artery in 2 (0.2%) cases in this study entered into the transverse foramen of the 7th cervical vertebra from the left. In 45 (4.9%) cases, the vertebral artery entered into the transverse foramen of the 5th cervical vertebra. Of these, the entrance was on the right in 15 (1.6%) and on the left in 30 (3.3%). We found 17 (1.8%) cases in which the artery entered into the transverse foramen of the 4th cervical vertebra, 10 (1.1%) on the right and 7 (0.7%) on the left side. As is commonly acknowledged, the 6th cervical vertebra was the most common site of entry; the vertebral artery entered the transverse foramen of the 6th cervical vertebra in the remaining 855 (93.0%) cases, on the right in 434 (47.2%) and on the left in 421 (45.8%). Conclusions: In conclusion, the possibility of an atypical course of the vertebral artery in segments V1 and V2 should be evaluated with magnetic resonance imaging (MRI) or CT images before carrying out procedures involving the anterior cervical vertebrae.

• Korean Journal of Digital Imaging in Medicine
• /
• v.12 no.2
• /
• pp.139-143
• /
• 2010

Two-dimensional(2D) images like Multi Planar Reconstruction(MPR) Image or Maximum Intensity Projection(MIP) were used for the purpose of diagnosis, but MPR image's quality were limited due to its superior limit of Z-axis ability to produce permitted radiation exposure virtuous in the permitted time limit from the existing Spiral CT. However, in company with the development of the Multi Detector Computed Tomography(MDCT), we were able to get the Data with the equal amount of Voxel, also get varied reconstructions as in the aspect of our needs. This present study propose a reconstruction technique which is to extract a field using Region of interest(ROI) segmentation method for improvement of the quality of the medical image and after that reconstruct the concerned part using the four-directed symmetry method of the oval, than using the reconstructed data, reorganize the image by using the Curved MPR method. If current proposed method is used, it is highly effective because of its ability to accurately display the disease concerned part, which will reduce the decoding time and also effectively provide information based on the accuracy of the decode.

• Journal of radiological science and technology
• /
• v.40 no.2
• /
• pp.229-235
• /
• 2017

In abdominal Ultrasonography, the fatty liver is diagnosed through hepatic parenchymal echo increased parenchymal density and unclear blood vessel boundary, and according to many studies, abdominal Ultrasonography has 60~90% of sensitivity and 84~95% of specificity in diagnosis of fatty liver, but the result of Ultrasonography is dependent on operators, so there can be difference among operators, and quantitative measurement of fatty infiltration is impossible. Among examinees who same day received abdominal Ultrasonography and chest computed tomography (CT), patients who were diagnosed with a fatty liver in the Ultrasonography were measured with liver Hounsfield Units (HU) of chest CT imaging to analyze the accuracy of the fatty liver diagnosis. Among 720 subject examinees, those who were diagnosed with a fatty liver through abdominal Ultrasonography by family physicians were 448, which is 62.2%. The result of Liver HU measurement in the chest CT imaging of those who were diagnosed with a fatty liver showed that 175 out of 720 had the measured value of less than 40 HU, which is 24.3%, and 173 were included to the 175 among 448 who were diagnosed through Ultrasonography, so 98.9% corresponded. This indicates that the operators' subjective ability has a great impact on diagnosis of lesion in Ultrasonography diagnosis of a fatty liver, and that in check up chest CT, under 40 HU in the measurement of Liver HU can be used for reference materials in diagnosis of a fatty liver.

• Journal of radiological science and technology
• /
• v.38 no.4
• /
• pp.421-427
• /
• 2015

In this study, we have observed the change of the Hounsfield (HU) in the alteration of by changing in size of physical area and setting size of region of interest (ROI) at focus on kVp and mAs. Four-channel multi-detector computed tomography was used to get transverse axial scanning images and HU. Three dimensional printer which is type of fused deposition modeling (FDM) was used to produce the Phantom. The structure of the phantom was designed to be a type of cylinder that contains 33 mm, 24 mm, 19 mm, 16 mm, 9 mm size of circle holes that are symmetrically located. It was charged with mixing iodine contrast agent and distilled water in the holes. The images were gained with changing by 90 kVp, 120 kVp, 140 kVp and 50 mAs, 100 mAs, 150 mAs, respectively. The 'image J' was used to get the HU measurement of gained images of ROI. As a result, it was confirmed that kVp affects to HU more than mAs. And it is suggested that the smaller size of physical area, the more decreasing HU even in material of a uniform density and the smaller setting size of ROI, the more increasing HU. Therefore, it is reason that to set maximum ROI within 5 HU is the best way to minimize in the alteration of by changing in size of physical area and setting size of region of interest.

• Journal of Radiation Protection and Research
• /
• v.32 no.3
• /
• pp.123-133
• /
• 2007

Z-axis automatic tube current modulation technique automatically adjusts tube current based on size of body region scanned. The purpose of the current study was to compare noise, and radiation dose of multi-detector row CT (MDCT) of lower extremity performed with Z-axis modulation technique of automatic tube current modulation with manual selection fixed tube current. Fifty consecutive underwent MDCT venography of lower extremity with use of a MDCT scanner fixed tube current and Z-axis automatic tube current modulation technique (10, 11 and 12 HU noise index, $70{\sim}450\;mA$). Scanning parameters included 120 kVp, 0.5 second gantry rotation time, 1.35:1 beam pitch, and 1 mm reconstructed section thickness. For each subject, images obtained with Z-axis modulation were compared with previous images obtained with fixed tube current (200, 250, 300 mA) and with other parameters identical. Images were compared for noise at five levels: iliac, femoral, popliteal, tibial, and peroneal vein of lower extremity. Tube current and gantry rotation time used for acquisitions at these levels were recorded. All CT examinations of study and control groups were diagnostically acceptable, though objective noise was significantly more with Z-axis automatic tube current modulation. Compared with fixed tube current, 2-axis modulation resulted in reduction of CTDIvol (range, $-6.5%{\sim}-35.6%$) and DLP (range, $-0.2%{\sim}-20.2%$). Compared with manually selected fixed tube current, 2-axis automatic tube current modulation resulted in reduced radiation dose at MDCT of lower extremity venography.

• Progress in Medical Physics
• /
• v.14 no.2
• /
• pp.131-140
• /
• 2003

As the importance of accuracy in measurings of 3-D anatomical structures continues to be stressed, an objective and quantitative of assessing image quality and accuracy of 3-D volume-rendered images is required. The purpose of this study was to evaluate the quantitative accuracy of 3-D rendered images obtained with MDCT, scanned at various scanning parameters (scan modes, slice thicknesses and reconstruction slice thickness). Twelve clinically significant points that play an important role for the craniofacial bone in plastic surgery and dentistry were marked on the surface of a dry human skull. The direct distances between the reference points were defined as gold standards to assess the measuring errors of 3-D images. Then, we scanned the specimen with acquisition parameters of 300 mA, In kVp, and 1.0 sec scan time in axial and helical scan modes (pitch 3:1 and 6:1) at 1,25 mm, 2.50 mm, 3.75 mm and 5.00 mm slice thicknesses. We performed 3-D visualizations and distance measurements with volumetric analysis software and statistically evaluated the quantitative accuracy of distance measurements. The accuracy of distance measurements on the 3-D images acquired with 1.25, 2.50, 3,75 and 5.00 mm slice thickness were 48%, 33%, 23%, 14%, respectively, and those of the reconstructed 1.25 mm were 53%, 41%, 43%, 36% respectively. Meanwhile, there were insignificant statistical differences (P-value<0.05) in the accuracy of the distance measurements of 3-D images reconstructed with 1.25 mm thickness. In conclusion, slice thickness, rather than scan mode, influenced the quantitative accuracy of distance measurements in 3-D rendered images with MDCT. The quantitative analysis of distance measurements may be a useful tool for evaluating the accuracy of 3-D rendered images used in diagnosis, surgical planning, and radiotherapeutic treatment.