• Nuclear Medicine and Molecular Imaging
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• v.42 no.5
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• pp.354-361
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• 2008

Purpose: N-13 ammonia uptake and retention in the myocardium is related to perfusion and metabolism. There are several potential advantages of N-13 ammonia positron emission tomography (PET) to detect myocardial ischemia, such as higher spatial resolution, greater counting efficiencies, and robust attenuation correction. But there are few reports comparing Tc-99m myocardial perfusion single photon emission tomography (MPS) and N-13 ammonia PET. We thus compared adenosine stress N-13 ammonia PET/CT and Tc-99m sestamibi MPS in patients with suspected coronary artery stenosis. Materials and Methods: Seventeen patients (male 13 : $63{\pm}11$ years old) underwent adenosine stress N-13 ammonia PET/CT (Discovery ST, GE), Tc-99m sestamibi MPS (dual head gamma camera, Hawkeye, GE) and coronary angiography within 1 week. N-13 ammonia PET/CT and Tc-99m sestamibi MPS images were assessed with a 20-segment model by visual interpretation and quantitative analysis using automatic quantitative software (Myovation, GE). Results: Both sensitivities and specificities of detecting an individual coronary artery stenosis were higher for N-13 ammonia PET/CT than Tc-99m sestamibi MPS (PET/CT: 91%/89% vs MPS: 65%/82%). N-13 ammonia PET/CT showed reversibility in 52% of segments that were considered non-reversibile by Tc-99m sestamibi MPS. In the 110 myocardial segments supplied by the stenotic coronary artery, N-13 ammonia PET/CT showed higher count densities than Tc-99m MPS on rest study (p < 0.01), and the difference of count density between the stress and the rest studies was also larger on N-13 ammonia PET/CT. Conclusion: Adenosine stress N-13 ammonia PET/CT had higher diagnostic sensitivity and specificity, more reversibility of perfusion defects and greater stress/rest uptake differences than Tc-99m sestamibi MPS. Accordingly, N-13 ammonia PET/CT might offer better assessment of myocardial ischemia and viability.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.185-191
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• 2016

The objective of this study was to detect the fragments generated during IV (intravenous) catheter injection of contrast medium and drug administration in a clinical setting and removal was performed by experimentally producing a phantom, and to compare the radiography, ultrasonography, and multi-detector computed tomography (MDCT) imaging and radiation dose. A 1 cm fragment of an 18 gage Teflon$^{(R)}$ IV catheter with saline was inserted into the IV control line. Radiography, CT, and ultrasonography were performed and radiography and CT dose were calculated. CT and ultrasonography showed an IV catheter fragment clinically and radiography showed no visible difference in the ability to provide a useful image of an IV catheter fragment modality (p >.05). Radiography of effective dose ($0.2139mSv{\cdot}Gy^{-1}{\cdot}cm^{-2}$) form DAP DAP ($0.93{\mu}Gy{\cdot}m^2 $), and dose length product (DLP) ($201mGy{\cdot}cm$) to effective dose was calculated as 0.483 mSv. IV catheter fragment were detected of radiography, ultrasonography and CT. These results can be obtained by menas of an excellent IV catheter fragment of detection capability CT. However, CT is followed by radiation exposure. IV catheter fragment confirming the position and information recommend an ultrasonography.

• Journal of radiological science and technology
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• v.42 no.2
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• pp.105-111
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• 2019

A medical personnel could be placed beside a patient together in CT room to do Ambu-bag for a seriously ill patients or emergency patient. At this time, the medical personnel can be exposed indirect radiation unnecessarily. In this case, it is necessary to recognize indirect radiation dose levels and methods to reduce them using actual clinical CT protocols such as Chest, Abdomen, and Brain CT. We researched surface radiation dose with or without radiation protectors such as apron and goggles according to different distances far from gantry using two different CT scanners (Fixed MDCT and mobile CT). As a result, for Chest, Abdomen, and Brain CT with Fixed MDCT, indirect radiation dose on thorax portion were 0.047, 0.089, 0.034 mSv without apron. Also, those with apron were 0.007, 0.012, 0.006 mSv. In case of mobile CT, it was 0.014 mSv without apron and 0.005 mSv with apron. By using protectors and increasing the distance, we could reduce it to 97%. Systematic management is necessary based on the measured data in order to minimize radiation damage due to indirect exposure dose.

• Journal of Radiation Industry
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• v.12 no.4
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• pp.267-276
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• 2018

A Hoffman 3D Brain Phantom was used to evaluate two PET/CT scanners, BIO_40 and D_690, according to the radiation dose of CT (low, medium and high) at a fixed kilo-voltage-peak (kVp) with the tube current(mA) varied in 17~20 stages(Bio_40 PET/CT scanner: the tube voltage was fixed to 120 kVp, the effective tube current(mAs) was increased from 33 mAs to 190 mAs in 10 mAs increments, D_690 PET/CT scanner: the tube voltage was fixed to 140 kVp, tube current(mA) was increased from 10 mAs to 200 mAs in 10 mAs increments). After obtaining the PET image, an attenuation correction was conducted based on the attenuation map, which led to an analysis of the difference in the image. First, the ratio of white to gray matter for each scanner was examined by comparing the coefficient of variation (CV) depending on the average ratio. In addition, a blind test was carried out to evaluate the image. According to the study results, the BIO_40 and D_690 scanners showed a <1% change in CV value due to the tube current conversion. The change in the coefficients of white and gray matter showed that the Z value was negative for both scanners, indicating that the coefficient of gray matter was higher than that of white matter. Moreover, no difference was observed when the images were compared in a blind test.

• Progress in Medical Physics
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• v.21 no.3
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• pp.246-252
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• 2010

The purpose of this study provides measurements of radiation dose from MDCT of head, chest, abdomen and pelvic examinations. A series of dose quantities that are measured of patient weight to compare the dose received during MDCT examinations. Data collected included: weight together with CT dose descriptors, volume CT dose index (CTDIvol) and dose length product (DLP). The effective dose was also estimated and served as collective dose estimation data. Data from 1,774 adult patients attending for a CT examination of the head (n=520) or chest (n=531) or abdomen (n=724) was obtained from spiral CT units using a same CT protocol. Mean values of CTDIvol was a range of 48.6 mGy for head and 6.9, 10.5 mGy for chest, abdomen examinations, respectively. And mean values of DLP was range of 1,604 $mGy{\cdot}cm$ for head, 250 $mGy{\cdot}cm$ for chest, 575 $mGy{\cdot}cm$ for abdomen examinations, respectively. Mean effective dose values for head, chest, abdominal CT were 3.6, 4.2, and 8.6 mSv, respectively. The degree of CTDIvol and DLP was a positive correlation with weight. And there was a positive correlation for weight versus CTDIvol ($r^2$=0.62), DLP ($r^2$=0.694) in chest. And head was also positive correlation with weight versus CTDIvol ($r^2$=0.691), DLP ($r^2$=0.741). We conclude that CTDIvol and DLP is an important determinant of weight within the CT examinations. The results for this study suggest that CT protocol should be tailored according to patient weight.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.233-239
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• 2009

A mixed CT/DT 2-1 cascaded ${\Sigma\Delta}M$ which includes a first stage CT ${\Sigma\Delta}M$ and a second stage mismatch insensitive two-channel time-interleaved DT ${\Sigma\Delta}M$ is proposed. With this approach, the advantages of both CT and DT ${\Sigma\Delta}Ms$ including high speed operation, inherent anti-aliasing filter, and good coefficient matching can be achieved. The two-channel time-interleaved ${\Sigma\Delta}M$ used in the second stage alleviates the speed constraints of the DT ${\Sigma\Delta}M$, whereas enables better matching between the analog and digital filter coefficients compared to CT ${\Sigma\Delta}Ms$.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.7
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• pp.3465-3468
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• 2016

Background: Fluorodeoxyglucose ($^{18}FDG$) PET/CT imaging has become an important component of the management paradigm in oncology. However, the significant imparted radiation exposure is a matter of growing concern especially in younger populations who have better odds of survival. The aim of this study was to estimate the effective dose received by patients having whole body $^{18}F$-FDG PET/CT scanning as per recent dose reducing guidelines at a tertiary care hospital. Materials and Methods: This prospective study covered 63 patients with different cancers who were referred for PET/CT study for various indications. Patients were prepared as per departmental protocol and 18FDG was injected at 3 MBq/Kg and a low dose, non-enhanced CT protocol (LD-NECT) was used. Diagnostic CT studies of specific regions were subsequently performed if required. Effective dose imparted by 18FDG (internal exposure) was calculated by using multiplying injected dose in MBq with coefficient $1.9{\times}10^{-2}mSv/MBq$ according to ICRP publication 106. Effective dose imparted by CT was calculated by multiplying DLP (mGy.cm) with ICRP conversion coefficient "k" 0.015 [mSv / (mG. cm)]. Results: Mean age of patients was $49{\pm}18$ years with a male to female ratio of 35:28 (56%:44%). Median dose of 18FDG given was 194 MBq (range: 139-293). Median CTDIvol was 3.25 (2.4-6.2) and median DLP was 334.95 (246.70 - 576.70). Estimated median effective dose imparted by $^{18}FDG$ was 3.69 mSv (range: 2.85-5.57). Similarly the estimated median effective dose by low dose (non-diagnostic) CT examination was 4.93 mSv (range: 2.14 -10.49). Median total effective dose by whole body 18FDG PET plus low dose non-diagnostic CT study was 8.85 mSv (range: 5.56-13.00). Conclusions: We conclude that the median effective dose from a whole body 18FDG PET/CT in our patients was significantly low. We suggest adhering to recently published dose reducing strategies, use of ToF scanner with CT dose reducing option to achieve the lower if not the lowest effective dose. This would certainly reduce the risk of second primary malignancy in younger patients with higher odds of cure from first primary cancer.

• The Korean Journal of Nuclear Medicine Technology
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• v.25 no.1
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• pp.15-20
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• 2021

Purpose This article studies the relationship between the length of a kidney measured by two scanning methods: Kidney Computed Tomography (CT) and ^99mTc-Dimercaptosuccinic acid (DMSA) renal scan. Kidney CT provides a better anatomic assessment, while ^99mTc-DMSA renal scan is superior in the kidney function test. Materials and Methods From January to December of 2019, two hundred patients who had Kidney CT and Tc^99m-DMSA renal scan were chosen for this study. SPSS17.0 was selected for statistical analysis. Results Due to the effect of the breathing and resolution of ^99mTc-DMSA renal scan, it showed the kidney's relatively longer length than the length of Kidney CT. For the same kidney, the length comparison among different brands' Gamma cameras was negligible. The length difference within the same age group did not show a noticeable discrepancy. However, there was a length difference between the radio technologists. Kidney CT and ^99mTc-DMSA renal scan indicated a strong positive correlation between the length of the left and right kidney. Conclusion It is necessary to establish a standardized measurement method for measuring kidney length using ^99mTc-DMSA renal scan. The kidney's functional changes and length changes are indications of Kidney diseases. Especially, pediatric patients tend to use ^99mTc-DMSA renal scan for assessing the kidney's shape and the function to avoid potential radiation exposure during the Kidney CT. Therefore, it is significant to provide not only the kidney's functional information but also an anatomic analysis, including the kidney's size, length, and location through the ^99mTc-DMSA renal scan.

• Korean Journal of Radiology
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• v.21 no.1
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• pp.68-76
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• 2020

Objective: To survey care providers' willingness to use 2-mSv computed tomography (CT) in their usual practice for adolescents and young adults with suspected appendicitis. Materials and Methods: An ethical committee approved this prospective study. We introduced 2-mSv CT in 20 hospitals through a pragmatic clinical trial. At the final phase of the trial, we invited 698 potentially-involved care providers in the survey regarding their willingness to use 2-mSv CT. Multivariable logistic regression analyses were performed to identify factors associated with willingness. Nine months after the completion of the trial patient recruitment, we surveyed whether the hospitals were using 2-mSv CT in usual practice. Results: The analyses included responses from 579 participants (203 attendings and 376 trainees; 221 radiologists, 196 emergency physicians, and 162 surgeons). Regarding the willingness to immediately change their standard practice to 2-mSv CT, 158 (27.3%), 375 (64.8%), and 46 (7.9%) participants responded as "yes" (consistently), "partly" (selectively), and "no", respectively. Willingness varied considerably across the hospitals, but only slightly across the participants' departments or job titles. Willingness was significantly associated with attendings (p = 0.004), intention to maintain the dedicated appendiceal CT protocol (p < 0.001), belief in compelling evidence on the carcinogenic risk of conventional-dose CT radiation (p = 0.028), and hospitals having more than 1000 beds (p = 0.031). Fourteen of the 20 hospitals kept using 2-mSv appendiceal CT in usual practice after the trial. Conclusion: Despite the extensive efforts over the years of this clinical trial, many care providers were willing to use 2-mSv CT selectively or not willing to use.

• Korean Journal of Radiology
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• v.23 no.4
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• pp.413-425
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• 2022

Objective: We compared appendiceal visualization on 2-mSv CT vs. conventional-dose CT (median 7 mSv) in adolescents and young adults and analyzed the undesirable clinical and diagnostic outcomes that followed appendiceal nonvisualization. Materials and Methods: A total of 3074 patients aged 15-44 years (mean ± standard deviation, 28 ± 9 years; 1672 female) from 20 hospitals were randomized to the 2-mSv CT or conventional-dose CT group (1535 vs. 1539) from December 2013 through August 2016. A total of 161 radiologists from 20 institutions prospectively rated appendiceal visualization (grade 0, not identified; grade 1, unsure or partly visualized; and grade 2, clearly and entirely visualized) and the presence of appendicitis in these patients. The final diagnosis was based on CT imaging and surgical, pathologic, and clinical findings. We analyzed undesirable clinical or diagnostic outcomes, such as negative appendectomy, perforated appendicitis, more extensive than simple appendectomy, delay in patient management, or incorrect CT diagnosis, which followed appendiceal nonvisualization (defined as grade 0 or 1) and compared the outcomes between the two groups. Results: In the 2-mSv CT and conventional-dose CT groups, appendiceal visualization was rated as grade 0 in 41 (2.7%) and 18 (1.2%) patients, respectively; grade 1 in 181 (11.8%) and 81 (5.3%) patients, respectively; and grade 2 in 1304 (85.0%) and 1421 (92.3%) patients, respectively (p < 0.001). Overall, undesirable outcomes were rare in both groups. Compared to the conventional-dose CT group, the 2-mSv CT group had slightly higher rates of perforated appendicitis (1.1% [17] vs. 0.5% [7], p = 0.06) and false-negative diagnoses (0.4% [6] vs. 0.0% [0], p = 0.01) following appendiceal nonvisualization. Otherwise, these two groups were comparable. Conclusion: The use of 2-mSv CT instead of conventional-dose CT impairs appendiceal visualization in more patients. However, appendiceal nonvisualization on 2-mSv CT rarely leads to undesirable clinical or diagnostic outcomes.