The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments
Purpose: To determine the effect of patient’s vertical off-centering and scout direction on the function of automatic tube voltage selection (ATVS) and tube current modulation (TCM) in chest computed tomography (CT). Methods: Chest phantom was scanned with Siemens and GE CT systems using three clini...
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| Format: | Article |
| Language: | English |
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Elsevier
2019-01-01
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| Series: | European Journal of Radiology Open |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352047718301035 |
| _version_ | 1818083658371694592 |
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| author | Touko Kaasalainen Teemu Mäkelä Mika Kortesniemi |
| author_facet | Touko Kaasalainen Teemu Mäkelä Mika Kortesniemi |
| author_sort | Touko Kaasalainen |
| collection | DOAJ |
| description | Purpose: To determine the effect of patient’s vertical off-centering and scout direction on the function of automatic tube voltage selection (ATVS) and tube current modulation (TCM) in chest computed tomography (CT). Methods: Chest phantom was scanned with Siemens and GE CT systems using three clinical chest CT protocols exploiting ATVS and a fixed 120 kVp chest protocol. The scans were performed at five vertical positions of the phantom (−6 to +6 cm from the scanner isocenter). The effects of scout direction (posterior-to-anterior, anterior-to-posterior, and lateral) and vertical off-centering on the function of ATVS and TCM were studied by examining changes in selected voltage, radiation dose (volume CT dose index, CTDIvol), and image noise and contrast. Results: Both scout direction and vertical off-centering affected ATVS. The effect differed between the vendors for the studied geometry, demonstrating differences in technical approaches. The greatest observed increase in CTDIvol due to off-centering was 91%. Anterior-to-posterior scout produced highest doses at the uppermost table position, whereas posterior-to-anterior scout produced highest doses at the lowermost table position. Dose varied least using lateral scouts. Vertical off-centering impacted image noise and contrast due to the combined effect of ATVS, TCM, structural noise, and bowtie filters. Conclusions: Patient vertical off-centering and scout direction affected substantially the CTDIvol and image quality in chest CT examinations. Vertical off-centering caused variation also in the selected tube voltage. The function of ATVS and TCM methods differ significantly between the CT vendors, resulting in differences in CTDIvol and image noise characteristics. Keywords: Automatic tube voltage selection, Image quality, Patient centering, Tube current modulation |
| first_indexed | 2024-12-10T19:41:30Z |
| format | Article |
| id | doaj.art-46594e65096f470cb9aadf3ce1d9ffa0 |
| institution | Directory Open Access Journal |
| issn | 2352-0477 |
| language | English |
| last_indexed | 2024-12-10T19:41:30Z |
| publishDate | 2019-01-01 |
| publisher | Elsevier |
| record_format | Article |
| series | European Journal of Radiology Open |
| spelling | doaj.art-46594e65096f470cb9aadf3ce1d9ffa02022-12-22T01:35:59ZengElsevierEuropean Journal of Radiology Open2352-04772019-01-0162432The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipmentsTouko Kaasalainen0Teemu Mäkelä1Mika Kortesniemi2HUS Medical Imaging Center, Helsinki University Central Hospital, Finland; Department of Physics, University of Helsinki, Finland; Corresponding author at: HUS Medical Imaging Center, Helsinki University Hospital, P.O. Box 340 (Haartmaninkatu 4), 00290, Helsinki, Finland.HUS Medical Imaging Center, Helsinki University Central Hospital, Finland; Department of Physics, University of Helsinki, FinlandHUS Medical Imaging Center, Helsinki University Central Hospital, Finland; Department of Physics, University of Helsinki, FinlandPurpose: To determine the effect of patient’s vertical off-centering and scout direction on the function of automatic tube voltage selection (ATVS) and tube current modulation (TCM) in chest computed tomography (CT). Methods: Chest phantom was scanned with Siemens and GE CT systems using three clinical chest CT protocols exploiting ATVS and a fixed 120 kVp chest protocol. The scans were performed at five vertical positions of the phantom (−6 to +6 cm from the scanner isocenter). The effects of scout direction (posterior-to-anterior, anterior-to-posterior, and lateral) and vertical off-centering on the function of ATVS and TCM were studied by examining changes in selected voltage, radiation dose (volume CT dose index, CTDIvol), and image noise and contrast. Results: Both scout direction and vertical off-centering affected ATVS. The effect differed between the vendors for the studied geometry, demonstrating differences in technical approaches. The greatest observed increase in CTDIvol due to off-centering was 91%. Anterior-to-posterior scout produced highest doses at the uppermost table position, whereas posterior-to-anterior scout produced highest doses at the lowermost table position. Dose varied least using lateral scouts. Vertical off-centering impacted image noise and contrast due to the combined effect of ATVS, TCM, structural noise, and bowtie filters. Conclusions: Patient vertical off-centering and scout direction affected substantially the CTDIvol and image quality in chest CT examinations. Vertical off-centering caused variation also in the selected tube voltage. The function of ATVS and TCM methods differ significantly between the CT vendors, resulting in differences in CTDIvol and image noise characteristics. Keywords: Automatic tube voltage selection, Image quality, Patient centering, Tube current modulationhttp://www.sciencedirect.com/science/article/pii/S2352047718301035 |
| spellingShingle | Touko Kaasalainen Teemu Mäkelä Mika Kortesniemi The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments European Journal of Radiology Open |
| title | The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments |
| title_full | The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments |
| title_fullStr | The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments |
| title_full_unstemmed | The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments |
| title_short | The effect of vertical centering and scout direction on automatic tube voltage selection in chest CT: a preliminary phantom study on two different CT equipments |
| title_sort | effect of vertical centering and scout direction on automatic tube voltage selection in chest ct a preliminary phantom study on two different ct equipments |
| url | http://www.sciencedirect.com/science/article/pii/S2352047718301035 |
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