OBJECTIVE: To explore the high-risk fault risk of CT simulator and the main causes of the risk, and to put forward effective risk management strategies. METHODS: The failure mode and effect analysis method was used to identify and control the operational fault risk of CT simulator. RESULTS: 5 major fault components, 8 fault failure models and 17 failure causes were analyzed. The top 5 failure causes are:anode target surface burn caused by direct scanning without warming up the tube (590.4), tube failure (518.2), burnout of joints caused by aging of high voltage cables (424.2), motor carbon brush wear (304.8) and belt break (296.4). CONCLUSIONS The failure mode and effect analysis method can effectively identify the risk of equipment failure, and thus specifically formulate risk management and control measures to ensure the normal operation of equipment and the safety of doctors and patients.
Equipment Failure ; statistics & numerical data ; Humans ; Risk Management ; methods ; Tomography, X-Ray Computed ; standards

OBJECTIVE: To determine in vivo efficacy of radiofrequency ablation (RFA) in porcine liver by using 15-gauge Octopus(R) (15-G Octopus(R)) electrodes to create a large coagulation. MATERIALS AND METHODS: A total of 18 coagulations were created by using a 180-W generator and 15-G Octopus(R) electrodes during laparotomy, performed in 14 pigs. Coagulation necrosis was created in the pig livers by the use of one of three RFA protocols: 1) group A, monopolar RFA using a 15-G Octopus(R) electrode with a 5-mm inter-electrode distance (n = 4); 2) group B, monopolar RFA using a 15-G Octopus(R) electrode with a 10-mm inter-electrode distance (n = 6); and 3) group C, switching monopolar RFA using two 15-G Octopus(R) electrodes (n = 8). The energy efficiency, shape, maximum and minimum diameters (Dmx and Dmi), and the volume of the coagulation volume were measured in each group. The Summary statistics were obtained and Mann-Whitney test was were performed. RESULTS: The mean ablated volume of each group was 49.23 cm3 in A, 64.11 cm3 in B, and 72.35 cm3 in C. The mean Dmx and Dmi values were 5.68 cm and 4.58 cm in A and 5.97 cm and 4.97 cm in B, respectively. In group C, the mean diameters of Dmx and Dmi were 6.80 cm and 5.11 cm, respectively. The mean ratios of Dmi/Dmx were 1.25, 1.20, and 1.35 in groups A, B, and C, respectively. There was one animal death during the RFA procedure, the cause of which could not be subsequently determined. However, there were no other significant, procedure-related complications during the seven-hour-delayed CT scans. CONCLUSION: RFA procedures using 15-G Octopus(R) electrodes are useful and safe for creating a large ablation in a single electrode model as well as in the multiple electrodes model.
Animals ; Catheter Ablation/*methods ; Electrocoagulation/*instrumentation ; *Electrodes ; Liver/radiography/*surgery ; Statistics, Nonparametric ; Swine ; Tomography, X-Ray Computed

BACKGROUND AND OBJECTIVES: High Resolution Computed Tomography(HRCT) of the temporal bone is the most accurate diagnostic tool and is popularly used in the chronic otitis media with cholesteatoma. However, the bony dehiscence of tympanic segment of the facial canal may be difficult to evaluate by the conventional HRCT of the temporal bone. This study was undertaken to develop a modified technique of axial CT scan for evaluation of bony dehiscence of tympanic segment of the facial canal. MATERIALS AND METHODS: A prospective study was performed in 33 patients with chronic otitis media with cholesteatoma. These patients had also underwent canal down mastoidectomy from August of 1996 through July of 1997. A correlation study of the CT and surgical findings at 40 degree and 30 degree axial scans was carried out. RESULTS: The sensitivity and specificity of this method for dehiscence of tympanic segment of the facial canal were 88.9% and 95.6%, respectively and the diagnostic predictability was 93.9%. However, the sensitivity, specificity, and diagnostic predictability of the 30 degree axial scan were 77.8%, 83.3%, and 81.8%, respectively. CONCLUSION: We think that the modified technique of axial CT scan of temporal bone is an effective method for detecting the dehiscence of tympanic segment of facial canal.
Cholesteatoma ; Facial Nerve* ; Humans ; Otitis Media ; Prospective Studies ; Sensitivity and Specificity ; Statistics as Topic ; Temporal Bone ; Tomography, X-Ray Computed

OBJECTIVE: We wanted to assess the trends of computed tomography (CT) examinations in a pediatric emergency department (ED). MATERIALS AND METHODS: We searched the medical database to identify the pediatric patients who had visited the ED, and the number of CTs conducted from January 2001 to December 2010. We analyzed the types of CTs, according to the anatomic region, and the patients who underwent CT examinations for multiple regions. Data were stratified, according to the patient age (< 13 years and 13 < or = ages < 18 years). RESULTS: The number of CTs performed per 1000 patients increased by 92% during the 10-year period (per 1000 patients, increased from 50.1 CTs in 2001 to 156.5 CTs in 2006, and then decreased to 96.0 CTs in 2010). Although head CTs were performed most often (74.6% of all CTs), facial bone CTs showed the largest rate of increase (3188%) per 1000 patients, followed by cervical CTs (642%), abdominal CTs (474%), miscellaneous CTs (236%), chest CTs (89%) and head CTs (39%). The number of patients who had CT examinations for multiple regions in the same day showed a similar pattern of increase, to that of overall CT examinations. Increase of CT utilization was more pronounced in adolescents than in pediatric patients younger than 13 years (189% vs. 59%). CONCLUSION: The utilization of CTs increases from 2001 to 2006, and has declined since 2006. The increase of CTs is more pronounced in adolescents, and facial bone CTs prevail in increased number of examination followed by cervical CTs, abdominal CTs, miscellaneous CTs, chest CTs, and head CTs.
Adolescent ; Child ; Child, Preschool ; Emergency Service, Hospital/statistics & numerical data/*trends ; Female ; Humans ; Male ; Multidetector Computed Tomography ; Republic of Korea ; Tertiary Care Centers/statistics & numerical data/*trends ; Tomography, X-Ray Computed/*trends/utilization

OBJECTIVE: We wanted to compare the variability in the longitudinal emphysema index (EI) measurements that were computed with standard and high resolution (HR) reconstruction algorithms (RAs). MATERIALS AND METHODS: We performed a retrospective review of 475 patients who underwent CT for surveillance of lung nodules. From this cohort, 50 patients (28 male) were included in the study. For these patients, the baseline and follow-up scans were acquired on the same multidetector CT scanner and using the same acquisition protocol. The CT scans were reconstructed with HR and standard RAs. We determined the difference in the EI between CT1 and CT2 for the HR and standard RAs, and we compared the variance of these differences. RESULTS: The mean of the variation of the total lung volume was 0.14 L (standard deviation [SD] = 0.13 L) for the standard RA and 0.16 L (SD = 0.15 L) for the HR RA. These differences were not significant. For the standard RA, the mean variation was 0.13% (SD = 0.44%) for EI -970 and 0.4% (SD = 0.88%) for EI -950; for the HR RA, the mean variation was 1.9% (SD = 2.2%) for EI -970 and 3.6% (SD = 3.7%) for EI -950. These differences were significant. CONCLUSION: Using an HR RA appears to increase the variability of the CT measurements of the EI.
Aged ; Algorithms ; Artifacts ; Female ; Humans ; Imaging, Three-Dimensional ; Male ; Pulmonary Emphysema/*radiography ; Radiographic Image Interpretation, Computer-Assisted/*methods ; Retrospective Studies ; Statistics, Nonparametric ; *Tomography, X-Ray Computed

This study was performed to develop and evaluate a semi-automatic seed localization algorithm from magnetic resonance (MR) images for interstitial prostate brachytherapy. The computerized tomography (CT) and MR images (3 mm-slice thickness) of six patients who had received real-time MR imaging-guided interstitial prostate brachytherapy were obtained. An automatic seed localization method was performed on CT images to obtain seed coordinates, and an algorithm for seed localization from MR images of the prostate was developed and tested. The resultant seed distributions from MR images were then compared to CT-derived distribution by matching the same seeds and calculating percent volume receiving 100% of the prescribed dose and the extent of the volume in 3-dimensions. The semiautomatic seed localization method made it possible to extract more than 90% of the seeds with either less than 8% of noises or 3% of missing seeds. The mean volume difference obtained from CT and MR receiving 100% of the prescribed dose was less than 3%. The maximum extent of the volume receiving the prescribed dose were 0.3, 0.6, and 0.2 cm in x, y, and z directions, respectively. These results indicate that the algorithm is very useful in identifying seeds from MR image for post-implant dosimety.
Algorithms ; Brachytherapy/*methods/statistics & numerical data ; Humans ; Iodine Radioisotopes/*administration & dosage ; *Magnetic Resonance Imaging, Interventional/statistics & numerical data ; Male ; Prostatic Neoplasms/*pathology/radiography/*radiotherapy ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Tomography, X-Ray Computed/statistics & numerical data ; Tumor Burden

OBJECTIVE: We evaluated the association between patients' weight and abdominal cross-sectional dimensions and CT image quality. MATERIALS AND METHODS: We prospectively evaluated 39 cancer patients aged more than 65 years with multislice CT scan of abdomen. All patients underwent equilibrium phase contrast-enhanced abdominal CT with 4 slices (from top of the right kidney) obtained at standard tube current (240 280 mA). All other scanning parameters were held constant. Patients' weight was measured just prior to the study. Cross-sectional abdominal dimensions such as circumference, area, average anterior abdominal wall fat thickness and, anteroposterior and transverse diameters were measured in all patients. Two subspecialty radiologists reviewed randomized images for overall image quality of abdominal structures using 5-point scale. Non-parametric correlation analysis was performed to determine the association of image quality with patients' weight and cross-sectional abdominal dimensions. RESULTS: A statistically significant negative linear correlation of 0.46, 0.47, 0.47, 0.58, 0.56, 0.54, and 0.56 between patient weight, anterior abdominal fat thickness, anteroposterior and transverse diameter, circumference, cross-sectional area and image quality at standard scanning parameters was found (p< 0.01). CONCLUSION: There is a significant association between image quality, patients' weight and cross-sectional abdominal dimensions. Maximum transverse diameter of the abdomen has the strongest association with subjective image quality.
Aged ; Aged, 80 and over ; Body Weight/*physiology ; Body Weights and Measures/*statistics & numerical data ; Contrast Media/administration & dosage ; Female ; Human ; Male ; Observer Variation ; Prospective Studies ; Radiation Dosage ; Radiography, Abdominal/*methods ; Statistics, Nonparametric ; Tomography, X-Ray Computed/*methods

OBJECTIVE: We aimed at evaluating the prevalence and CT characteristics of occult coronary artery disease (CAD) in young Korean adults under 40 years of age by performing coronary CT angiography (CCTA). MATERIALS AND METHODS: We retrospectively enrolled 112 consecutive asymptomatic subjects (90 men, mean age: 35.6 +/- 3.7 years) who underwent CCTA as part of a general health evaluation. We classified the subjects into three National Cholesterol Education Program risk categories and we assessed the plaque characteristics on CCTA according to the number of involved vessels, the location and type of plaques and vascular remodeling. RESULTS: Twelve individuals had CAD (11%, 11 men). The prevalence of CAD was significantly higher in the subgroups with moderate (22%) or high (25%) risk than that in the low risk subgroup (5%) (p < 0.05). Nine patients had single-vessel disease and three patients had two-vessel disease. The most common location for plaque was the proximal left anterior descending coronary artery (60%). All the patients had non-significant stenosis and plaque, including the non-calcified (27%), mixed (47%) and calcified (27%) types. Positive vascular remodeling was identified in all the patients with non-calcified or mixed plaques. CONCLUSION: The prevalence of occult CAD was not negligible in the asymptomatic young adults with moderate to high risk, and this suggests the importance of management and risk factor modification in this population. All the patients had non-significant stenosis, and one fourth of the plaques did not show calcification.
Adult ; Chi-Square Distribution ; Contrast Media ; *Coronary Angiography ; Coronary Disease/*epidemiology/*radiography ; Female ; Humans ; Korea/epidemiology ; Male ; Prevalence ; Retrospective Studies ; Risk Assessment ; Risk Factors ; Statistics, Nonparametric ; Tomography, X-Ray Computed/*methods

OBJECTIVE: Clinical presentation and physical signs may be unreliable in the diagnosis of stercoral colitis (SC). This study evaluates the value of computed tomography (CT) in distinguishing fatal from non-fatal SC. MATERIALS AND METHODS: Ten patients diagnosed as SC were obtained from inter-specialist conferences. Additional 13 patients with suspected SC were identified via the Radiology Information System (RIS). These patients were divided into two groups; fatal and non-fatal SCs. Their CT images are reviewed by two board-certified radiologists blinded to the clinical data and radiographic reports. RESULTS: SC occurred in older patients and displayed no gender predisposition. There was significant correlation between fatal SC and CT findings of dense mucosa (p = 0.017), perfusion defects (p = 0.026), ascites (p = 0.023), or abnormal gas (p = 0.033). The sensitivity, specificity, and accuracy of dense mucosa were 71%, 86%, and 81%, respectively. These figures were 75%, 79%, and 77% for perfusion defects; 75%, 80%, and 78% for ascites; and 50%, 93%, and 78% for abnormal gas, respectively. Each CT sign of mucosal sloughing and pericolonic abscess displayed high specificity of 100% and 93% for diagnosing fatal SC, respectively. However, this did not reach statistical significance in diagnosing fatal SC. CONCLUSION: CT appears to be valuable in discriminating fatal from non-fatal SC.
Adult ; Aged ; Aged, 80 and over ; Chi-Square Distribution ; Colitis/mortality/*radiography ; Contrast Media/diagnostic use ; Diagnosis, Differential ; Fecal Impaction/mortality/*radiography ; Female ; Humans ; Male ; Middle Aged ; Retrospective Studies ; Risk Factors ; Sensitivity and Specificity ; Statistics, Nonparametric ; Tomography, X-Ray Computed/*methods

OBJECTIVE: Arsenic trioxide (As2O3) can be used as a possible pharmaceutical alternative that augments radiofrequency (RF) ablation by reducing tumor blood flow. The aim of this study was to assess the effect of intraarterial and intravenous administration of As2O3 on RF-induced ablation in an experimentally induced liver tumor. MATERIALS AND METHODS: VX2 carcinoma was grown in the livers of 30 rabbits. As2O3 (1 mg/kg) was administered through the hepatic artery (n = 10, group A) or ear vein (n = 10, group B), 30 minutes before RF ablation (125 mA +/- 35; 90 +/- 5degrees C). As a control group, 10 rabbits were treated with RF ablation alone (group C). RF was intentionally applied to the peripheral margin of the tumor so that ablation can cover the tumor and adjacent hepatic parenchyma. Ablation areas of the tumor and adjacent parenchymal changes among three groups were compared by the Kruskal-Wallis and Mann-Whitney U test. RESULTS: The overall ablation areas were 156 +/- 28.9 mm2 (group A), 119 +/- 31.7 (group B), and 92 +/- 17.4 (group C, p < 0.04). The ablation area of the tumor was significantly larger in group A (73 +/- 19.7 mm2) than both group B (50 +/- 19.4, p = 0.02) and group C (28 +/- 2.2, p < 0.01). The ratios of the tumoral ablation area to the overall ablation area were larger in group A (47 +/- 10.5%) than that of the other groups (42 +/- 7.3% in group B and 32 +/- 5.6% in group C) (p < 0.03). CONCLUSION: Radiofrequency-induced ablation area can be increased with intraarterial or intravenous administration of As2O3. The intraarterial administration of As2O3 seems to be helpful for the selective ablation of the tumor.
Animals ; Arsenicals/*pharmacology ; Catheter Ablation/*methods ; Combined Modality Therapy ; Contrast Media/diagnostic use ; Disease Models, Animal ; Liver/radiography ; Liver Neoplasms, Experimental/*drug therapy/radiography/*surgery ; Oxides/*pharmacology ; Rabbits ; Statistics, Nonparametric ; Tomography, X-Ray Computed