• Journal of the Korean Society of Radiology
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• v.5 no.2
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• pp.59-66
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• 2011

There is a difficulty because of classifying the anatomical structure in the neck CT scan by the beam hardening artifact no more than disease and it including the 6, 7 number cervical spine and intervertebral disk. In case of enforcing the neck CT scan cause of the inner diameter of beam artifact tried to be inquired by the image evaluation according to the change of the image evaluation according to the direction of the shoulder joint applying the variation method of a posture and location and Kernel value and it was most appropriate, the lion tax and Kernel value try to be searched for through an experiment. Somatom Sensation 16 (Siemens, Enlarge, Germany) equipment was used in a patient 30 people coming to the hospital for the neck CT scan. A workstation used the AW 4.4 version (GE, USA). According to a direction and location of the shoulder joint, the patient posture gave a change to the direction of the shoulder joint as the group S it gave a change as three postures and placed the both arms comfortably and helps a group N and augmented unipolar left in the wealthy merchant and group P it memorized the both hands and ordered the eversion and drops below to the utmost and enforced a scan. By using a reconstructing method as the second opinion, it gave and reconstructed the Kernel value a change based on scan data with B 10 (very smooth), B 20 (smooth), B 30 (medium smooth), B 40 (medium), B 50 (medium sharp), B 60 (sharp), and B 70 (very sharp). By using image data which gave the change of the examination posture and change of the Kernel value and are obtained, we analyzed through the noise value measurement and image evaluation of. The outside wire eversion orders the both hands and the examination posture is cost in the neck CT scan with the group P it drops below to the utmost. And in case of when reconstructing with B 40 (medium) or B 50 (medium sharp) being most analyzed into the inappropriate posture and Kernel value and applying the Kernel value to a clinical, it is considered to be very useful.

• Journal of Digital Convergence
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• v.10 no.2
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• pp.243-247
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• 2012

Beam hardening artifact happens in the CT image. when a PET/CT is conducted while there is a metallic dental implant. The artifact appears in the CT image can affect the PET image. When the patient with head and neck cancer has a metallic dental implant, Beam hardening artifact which was taken in th CT image can change the PET image and SUV value. Therefore, by Quantitative measure of the SUV according to the change in HU by the metallic dental implant, the appropriacy in the clinical application was assessed. The records of 47 patients with PET/CT August 2011. For the analysis, 2 region of interest were defined in area where CT and PET image. As a result of the experiment, if there in an implant, the HU and the SUV increased and there existed a statistically significant difference(p<0.01). Although this level of increase was not large compared with that in the patient who have no metallic dental implant, when a person has head and neck cancer, it is even more likely to be overestimated when diagnosing the cancer. When conducting PET/CT for the patient who have head and neck cancer, the physical biological parts should be considered in order not to make an error in decoding.

• Imaging Science in Dentistry
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• v.50 no.1
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• pp.1-7
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• 2020

Purpose: This study was performed to evaluate the magnitude of artifacts produced by gutta-percha and metal posts on cone-beam computed tomography (CBCT) scans obtained with different tube currents and with or without metal artifact reduction (MAR). Materials and Methods: A tooth was inserted in a dry human mandible socket, and CBCT scans were acquired after root canal instrumentation, root canal filling, and metal post placement with various tube currents with and without MAR activation. The artifact magnitude was assessed by the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) at the various distances from the tooth. Data were compared using multi-way analysis of variance. Results: At all distances, a current of 4 mA was associated with a higher SD and a lower CNR than 8 mA or 10 mA (P<0.05). For the metal posts without MAR, the artifact magnitude as assessed by SD was greatest at 1.5 cm or less (P<0.05). When MAR was applied, SD values for distances 1.5 cm or closer to the tooth were reduced (P<0.05). MAR usage did not influence the magnitude of artifacts in the control and gutta-percha groups(P>0.05). Conclusion: Increasing the tube current from 4 mA to 8 mA may reduce the magnitude of artifacts from metal posts. The magnitude of artifacts arising from metal posts was significantly higher at distances of 1.5 cm or less than at greater distances. MAR usage improved image quality near the metal post, but had no significant influence farther than 1.5 cm from the tooth.

• Imaging Science in Dentistry
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• v.50 no.2
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• pp.153-159
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• 2020

Purpose: This study was conducted evaluate the influence of reconstruction parameters of micro-computed tomography (micro-CT) images on bone mineral density (BMD) analyses. Materials and Methods: The sample consisted of micro-CT images of the maxillae of 5 Wistar rats, acquired using a SkyScan 1174 unit (Bruker, Kontich, Belgium). Each acquisition was reconstructed following the manufacturer's recommendations(standard protocol; SP) for the application of artifact correction tools(beam hardening correction [BHC], 45%; smoothing filter, degree 2; and ring artifact correction [RAC], level 5). Additionally, images were reconstructed with 36 protocols combining different settings of artifact correction tools (P0 to P35). BMD analysis was performed for each reconstructed image. The BMD values obtained for each protocol were compared to those obtained using the SP through repeated-measures analysis of variance with the Dunnett post hoc test(α=0.05). Results: The BMD values obtained from all protocols that used a BHC of 45% did not significantly differ from those obtained using the SP (P>0.05). The other protocols all yielded significantly different BMD values from the SP(P<0.05). The smoothing and RAC tools did not affect BMD values. Conclusion: BMD values measured on micro-CT images were influenced by the BHC level. Higher levels of BHC induced higher values of BMD.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.110-116
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• 2010

Purpose: The X-ray attenuation coefficient based on CT images is used for attenuation correction in PET/CT. The polychromatic X-ray beam can introduce beam-hardening artifact on CT images. The aims of the study were to evaluate the effect of dental metal prostheses in phantom and patients on apparent tracer activity measured with PET/CT when using CT attenuation correction. Materials and Methods: 40 normal patients (mean age $54{\pm}12$) was scanned between Jan and Feb 2010. NEMA(National Electrical Manufactures Association) PET $Phantom^{TM}$ (NU2-1994) was filled with $^{18}F$-FDG injected into the water that insert implant and metal prostheses dental cast. Region of interest were drawn in non-artifact region, bright steak artifact region and dark streak artifact region on the same transaxial CT and PET slices. Patients and phantom with dental metal prostheses and dental implant were evaluated the change rate of CT Number and $SUV_{mean}$ in PET/CT. A paired t-test was performed to compare the ratio and the difference of the calculated values. Results: In patients with dental metal prostheses, $SUV_{mean}$ was reduced 19.64% (p<0.05) in the non-steak artifact region than the brightstreak artifact region whereas was increased 90.1% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In phantom with dental metal prostheses, $SUV_{mean}$ was reduced 18.1% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 18.0% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In patients with dental implant, $SUV_{mean}$ was increased 19.1% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 96.62% (p>0.05) in the non-steak artifact region than the dark streak artifact region. In phantom with dental implant, $SUV_{mean}$ was increased 14.4% (p<0.05) in the non-steak artifact region than the bright streak artifact region whereas was increased 7.0% (p>0.05) in the non-steak artifact region than the dark streak artifact region. Conclusion: When CT is used for attenuation correction in patients with dental metal prostheses, 19.1% reduced $SUV_{mean}$ is anticipated in the dark streak artifact region on CT images. The dark streak artifacts of CT by dental metal prostheses may cause false negative finding in PET/CT. We recommend that the non-attenuation corrected PET images also be evaluated for clinical use.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.101-108
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• 2016

Purpose : The purpose of this study was to evaluate the Retro recon in SRS planning using BranLAB when stereotactic location error occurs by metal artifact. Materials and Methods : By CT simulator, image were acquired from head phantom(CIRS, PTW, USA). To observe stereotactic location recognizing and beam hardening, CT image were approved by SRS planning system(BrainLAB, Feldkirchen, Germany). In addition, we compared acquisition image(1.25mm slice thickness) and Retro recon image(using for 2.5 mm, 5mm slice thickness). To evaluate these three images quality, the test were performed by AAPM phantom study. In patient, it was verified stereotactic location error. Results : All the location recognizing error did not occur in scanned image of phantom. AAPM phantom scan images all showed the same trend. Contrast resolution and Spatial resolution are under 6.4 mm, 1.0 mm. In case of noise and uniformity, under 11, 5 of HU were measured. In patient, the stereotactic location error was not occurred at reconstructive image. Conclusion : For BrainLAB planning, using Retro recon were corrected stereotactic error at beam hardening. Retro recon may be the preferred modality for radiation treatment planning and approving image quality.

• Journal of Korean Neurosurgical Society
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• v.42 no.2
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• pp.103-111
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• 2007

Objective : We evaluated the accuracy of multislice computerized tomographic angiography (MCTA) in the postoperative evaluation of clipped aneurysms by comparising it with three dimensional digital subtraction angiography (3D-DSA). Methods : Between May 2004 and September 2006, we included patients with ruptured cerebral aneurysm of the anterior circulation that was surgically clipped and evaluated by both postoperative MCTA and postoperative 3D-DSA. We measured the diagnostic performance and calculated the sensitivity and specificity of postoperative MCTA compared to 3D-DSA in the detection of aneurysm remnants. Results : A total of 11 neck remnants among the 92 clipped aneurysms (11.9%) were confirmed by 3D-DSA. According to Sindou's classification of aneurysm remnants, 8.7% of clipped aneurysms (8/92) had only neck remnant on 3D-DSA and 3.2% (3/92 aneurysms) had residuum of the neck and sac on 3D-DSA. There were 12 (13.04%) equivocal cases that were difficult to interpret based on the postoperative MCTA. The reasons for the equivocal cases included multiple clips (6 cases, 50.0%). beam-hardening effect (4 cases, 33.3%), motion artifact (1 case, 8.3%), fenestrated clip (1 case, 8.3%) and other combined causes. The sensitivity and specificity of the postoperative MCTA was 81.8% and 88.9%, respectively by ROC curve (p=0.000). Conclusion : MCTA is an accurate noninvasive imaging method used for the assessment of clipped aneurysms in the anterior circulation. If the image quality of postoperative MCTA is good quality and the patient has been treated with a single titanium clip, except a fenestrated clip, the absence of an aneurysm remnant can be diagnosed by MCTA alone and the need for postoperative DSA can be reduced in a large percentage of cases.

• Journal of Chest Surgery
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• v.32 no.8
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• pp.693-701
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• 1999

Recently non-invasive diagnostic imaging replaced the invasive catheter angiography in the diagnosis of vascular disease. Catheter methods are now almost confined to the purpose of intervention. Coronary artery or coronary artery bypass graft still needs catheter technique because of small diameter and the cardiac motion. The last challenge for radiologists in this domain is to obtain a non-invasive imaging. Electron beam tomography(EBT) for high temporal resolution is able to obtain a coronary arteriogram or coronary artery bypass graft (CABG), of which CABG imaging is quite useful for the evaluation of patency. In our experience as well as others, the accuracy of EBT angiogram in evaluating CABG patency revealed that the accuracy of patency of saphenous vein grafts(SVG) is high due to relatively wide lumen, short and straight course and less influence from cardiac motion. The sensitivity and specificity of patency of SVGs were 92%, 97% respectively in the prospective evaluat on and 100% each in the retrospective evaluation. A false positive and a false negative case are rudimentary errors in the initial learing period. In contrast the analysis of left internal mammary artery(LIMA) graft was difficult due to the inherent small size and the adjacent surgical clips provoking beam-hardening artifact; therefore, the method of combining 3 dimensional reconstruction and flow mode study was important in improving the accuracy of LIMA patency. The sensitivity and specificity of LIMA patency were 100% and 80% in both prospective and retrospective evaluation. Therefore, EBT angiography is an accurate non-invasive diagnostic modality for evaluating the patency of CABG, particularly in SVGs. The accuracy can be improved with the improvement of the EBT and the development of the image reconstruction software.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.44-49
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• 2012

Purpose: In the whole body PET/CT scan, it is natural to lift the patient's arm for its quality improvement. However, when the lesion is located in head and neck, the arms should be located lower. This study was designed to compare the CT effective dose for each arm position applying Automatic Exposure Control (AEC). Materials and Methods: 45 patients who had $^{18}F$-FDG whole body PET/CT scan were studied with Biograph Truepoint 40 (SIEMENS, GERMANY), Biograph Sensation 16 (SIEMENS, GERMANY), Discovery STe 8 (GE healthcare, USA). The CT effective dose of 15 patients for each equipment was measured and comparatively analyzed in both arm-lifted position and lower-arm position. ImPACT v1.0 program was used as the method of measurement for CT effective dose. For the statistics analysis, Paired t-test which paired with SPSS 18.0 statistic program was applied. Results: In the case of arm-lifted, it was measured as $6.33{\pm}0.93mSv$ for Biograph Sensation 16, $8.01{\pm}1.34mSv$ for Biograph Truepoint 40, and $9.69{\pm}2.32mSv$ for Discovery STe 8. When arms are located lower position, it was measure as $6.97{\pm}0.76mSv$, $8.95{\pm}1.85mSv$, $13.07{\pm}2.87mSv$ for each. CT effective dose according to the arm position was 9.2% for Biograph Truepoint 40, 10.5% for Biograph Sensation 16, and 25.9% for Discovery Ste 8. The statistics analysis showed the meaningful difference ($p$<0.05). Conclusion: For the whole body PET/CT case, CT effective dose applying AEC was decreased the radiation exposure of the patients when the arm was lifted for 15.2% of average value. The patient who has no lesion in head and neck would decrease the artifact occurrence in objective part and lower the CT effective dose. Also, for the patient who had lesion in head and neck, the artifact in objective part can be lower by putting the arms down, the fact that CT effective dose increases should be concerned in its whole body PET/CT scan.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.110-114
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• 2017

Because the arm can't be sutured due to fracture during a elbow CT scan, a CT scan is proceeded in a state of abdomen and L-spire are overlapped which beam hardening artifact is done many times, and it often lowers the quality of elbow CT images. So there are many difficulties in reading and due to increase in radiation dose from it, the number of patient's exposure keeps increasing. In this research, it plans to improve the quality of the images by avoiding overlap with abdomen, and increasing the number of photon overlapped with lung field which the line attenuation is relatively small. The way of experiment is based on patient's right elbow and place him as head first position, then place his elbow at L2-3 level in supine position, turn about 30 degrees to the left in non-control breathing and in supine position, and compared with full inspiration after overlapping with lung. After figuring out the average value and standard deviation data using Image J program 5 times each for 16, 128 channels, the evaluation is proceeded by measuring each of CNR, MSR are statistically analyzed using SPSS program. Therefore, through positioning and inspiration during elbow CT scan, the way of inspection minimized the exposure radiation dose, and seems to be meaningful in a way to improve the quality of the images.