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The effect of patient body habitus and modulation strength on radiation dose and image quality in CT examinations using automatic tube current modulation
Abstracts / Physica Medica 30 (2014) e45ee74
THE ACDS PILOT: SUMMARY OF OUTCOMES FROM A BESPOKE NATIONAL AUDITING SERVICE Williams Ivan a, f, Lye Jessica a, f, Lehmann Joerg b, f, Kenny John a, c, f, Dunn Leon a, f, Alves Andrew a, f, Cole Andrew a, f, Johnston Peter d, f, Kron Tomas e, f. a Australian Clinical Dosimetry Service, 619 Lower Plenty Rd, Yallambie, Australia, 3085. [Presenter]; b Institute of Medical Physics, School of Physics, University of Sydney, Australia, 2006; c Radiation Oncology Queensland, Toowoomba, Australia, 4350; d Olivia Newton-John Cancer and Wellness Centre, Heidelburg, Australia, 3084; e Australian Radiation and Nuclear Safety Agency, 619 Lower Plenty Rd, Yallambie, Australia, 3085; f Peter MacCallum Cancer Centre, East Melbourne, Australia, 8006 Background: The Australian pilot of a national dosimetry audit program has completed the originally contracted three years of operation. The Australian Clinical Dosimetry Service, (ACDS) was a pilot program to enable the Australian Government to determine whether the bespoke design was suitable for an on-going Australian service. The outcomes from the three years of operations will be presented and discussed with an analysis of whether the pilot requirements were met and why. Materials and methods: Designed over 2010/11 by experts drawn from the three professions in consultation with the national Department of Health, a list of outcomes required over a three year time frame was formulated. These outcomes were central to a Memorandum of Understanding, (MoU) between Health and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) which hosted the ACDS. The MoU defined the operational and reporting requirements for the ACDS and the need for external advisors drawn from the hospitals: the Clinical Advisory Group, (CAG). Results: The ACDS has achieved all the MoU requirements. The staff within the ACDS engaged with the professional clinical workforce and provided a successful and functioning audit service. External review of the ACDS during its third year of operation identified strengths and weaknesses within the MoU and the ACDS structure and how the ACDS resolved a number of conflicting issues. The report identified the successes within the ACDS and how these were achieved. Analysis of the ACDS design and operation will provide assistance and advise those seeking to design or modify national or regional auditing programs. Finally the paper reviews the potential future for the ACDS. Discussion: The raw number of audits and outcomes indicate that the ACDS has met the MoU auditing requirements. The reasons for the ACDS’ success are highly dependent on: attracting quality staff who can respond with agility to changing situations, a high level of communication with the professional community, and a high level of engagement by the community. The Australian Clinical Dosimetry Service is a joint initiative between the Department of Health and Ageing and the Australian Radiation Protection and Nuclear Safety Agency.
THE EFFECT OF PATIENT BODY HABITUS AND MODULATION STRENGTH ON RADIATION DOSE AND IMAGE QUALITY IN CT EXAMINATIONS USING AUTOMATIC TUBE CURRENT MODULATION Antonios E. Papadakis a, Kostas Perisinakis b, John Damilakis b. a University Hospital of Heraklion, Medical Physics Department, Heraklion, Crete, Greece; b University of Crete, Medical School, Medical Physics Department, Heraklion, Crete, Greece Background: The aim of this study was to investigate the effect of patient body habitus and modulation strength on radiation dose and image quality in CT examinations using automatic tube current modulation (ATCM). Materials and methods: Ten physical anthropomorphic phantoms that simulate the average individual as neonate, 1-, 5-, and 10-year-old and adult were employed. The 10-year-old and adult anthropomorphic phantoms were appropriately devised using custom made bolus material to simulate overweight and obese patients. Head, neck, thorax, and abdomen/pelvis helical acquisitions were performed in all phantoms using the standard pediatric and adult examination protocols specified for each
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anatomical region. Acquisitions were performed using a sixteen-slice CT scanner, which was equipped with an angular and z-axis ATCM system. CT acquisitions were performed at fixed tube current and with the ATCM system activated at three different modulation strength settings i.e. weak, average, and strong. Image noise was measured as the average standard deviation of the Hounsfield unit across regions of interest, which were drawn over uniform tissue equivalent areas. Results: The modulated mAs recorded for neonate compared to 10-yearold increased by 30%, 14%, 6%, and 53% for head, neck, thorax and abdomen/pelvis, respectively, (P<0.05). Fixed tube current and ATCMactivated acquisitions provided images of similar noise at a significant reduction of the modulated mAs with the exception of the 10-year-old phantom. In pediatric and adult phantoms, the modulated mAs ranged from 44 and 53 for weak to 117 and 93 for strong modulation strength, respectively. At the same exposure parameters image noise increased with body size (P<0.05). Discussion: The ATCM system investigated herein can effectively reduce patient radiation dose in adult individuals regardless their body habitus. However, ATCM may increase patient radiation dose in trunk CT examinations of children older than 5-year-old. Care should be taken when implementing ATCM protocols to ensure that image quality is maintained. AUTOMATIC QUANTIFICATION OF CONTRAST ENHANCED ULTRASOUND LIVER IMAGING Elias Gatos a, Stavros Tsantis a,b, Aikaterini Skouroliakou c, Ioannis Theotokas d, Pavlos S. Zoumpoulis d, George C. Kagadis a. a Department of Medical Physics, School of Medicine, University of Patras, GR 26504, Rion; b Department of Biomedical Engineering, Technological Educational Institute of Athens, GR 12210, Egaleo; c Department of Energy Technology Engineering, Technological Educational Institute of Athens, GR 12210, Egaleo; d Diagnostic Echotomography SA, 317C Kifissias Ave., GR 14561, Kifissia Background: Ultrasound contrast agent imaging (CEUS) has overcome the major limitation of classic Liver B-Mode and Doppler Ultrasound, and provided the ability to depict the parenchyma microvasculature. The enhancement pattern of Focal Liver lesions (FLLs) can be studied and evaluated in real time throughout all vascular phases (arterial, portal venous, late and postvascular phases). FLL characterization is currently performed either by means of visual inspection or by built-in software packages that provide low quality time-intensity curves without quantitative assessment. A new automatic method is proposed that initially detects an FLL and then provides time-intensity curves towards its characterization. Materials and methods: Twelve (12) CEUS image series of 12 patients with FLLs disease have been subjected for quantification into the proposed algorithm. A specifically designed detection algorithm was implemented to detect the FLL across frames and extract its contour. This particular lesion region represents the region of interest on CEUS images, from which the enhancement pattern and its type can be derived. The algorithm is based on unsupervised segmentation, utilizing the Markov Random Field model (MRF) and Continuous Wavelet Transform (CWT) employing the ‘Mexican Hat’ wavelet filter. The proposed algorithm employs textural and multi-scale wavelet coefficient information provided by CWT analysis. Wavelet analysis produces the initial clusters into the MRF procedure to minimize the number of iteration steps and to enhance the clustering speed. Results: Compared with manual segmentation by an expert physician, the lesion detected had an average overlap value of 0.92±0.02 for all CEUS videos included in the study. Following the lesion detection procedure time-intensity curves are computed and plotted from lesion and reference areas (Figure). In addition, several parameters are computed such as Area Under the Curve, Mean Transit Time, Perfusion Index, Rise Time and Time to Peak to strengthen the evaluation procedure. Discussion: A new promising tool has been implemented towards FLL detection and time Intensity curves analysis in CEUS data. After lesion detection, the degree and phase of lesion enhancement relative to the parenchyma is computed and visualized to evaluate the lesion character.
THE ACDS PILOT: SUMMARY OF OUTCOMES FROM A BESPOKE NATIONAL AUDITING SERVICE Williams Ivan a, f, Lye Jessica a, f, Lehmann Joerg b, f, Kenny John a, c, f, Dunn Leon a, f, Alves Andrew a, f, Cole Andrew a, f, Johnston Peter d, f, Kron Tomas e, f. a Australian Clinical Dosimetry Service, 619 Lower Plenty Rd, Yallambie, Australia, 3085. [Presenter]; b Institute of Medical Physics, School of Physics, University of Sydney, Australia, 2006; c Radiation Oncology Queensland, Toowoomba, Australia, 4350; d Olivia Newton-John Cancer and Wellness Centre, Heidelburg, Australia, 3084; e Australian Radiation and Nuclear Safety Agency, 619 Lower Plenty Rd, Yallambie, Australia, 3085; f Peter MacCallum Cancer Centre, East Melbourne, Australia, 8006 Background: The Australian pilot of a national dosimetry audit program has completed the originally contracted three years of operation. The Australian Clinical Dosimetry Service, (ACDS) was a pilot program to enable the Australian Government to determine whether the bespoke design was suitable for an on-going Australian service. The outcomes from the three years of operations will be presented and discussed with an analysis of whether the pilot requirements were met and why. Materials and methods: Designed over 2010/11 by experts drawn from the three professions in consultation with the national Department of Health, a list of outcomes required over a three year time frame was formulated. These outcomes were central to a Memorandum of Understanding, (MoU) between Health and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) which hosted the ACDS. The MoU defined the operational and reporting requirements for the ACDS and the need for external advisors drawn from the hospitals: the Clinical Advisory Group, (CAG). Results: The ACDS has achieved all the MoU requirements. The staff within the ACDS engaged with the professional clinical workforce and provided a successful and functioning audit service. External review of the ACDS during its third year of operation identified strengths and weaknesses within the MoU and the ACDS structure and how the ACDS resolved a number of conflicting issues. The report identified the successes within the ACDS and how these were achieved. Analysis of the ACDS design and operation will provide assistance and advise those seeking to design or modify national or regional auditing programs. Finally the paper reviews the potential future for the ACDS. Discussion: The raw number of audits and outcomes indicate that the ACDS has met the MoU auditing requirements. The reasons for the ACDS’ success are highly dependent on: attracting quality staff who can respond with agility to changing situations, a high level of communication with the professional community, and a high level of engagement by the community. The Australian Clinical Dosimetry Service is a joint initiative between the Department of Health and Ageing and the Australian Radiation Protection and Nuclear Safety Agency.
THE EFFECT OF PATIENT BODY HABITUS AND MODULATION STRENGTH ON RADIATION DOSE AND IMAGE QUALITY IN CT EXAMINATIONS USING AUTOMATIC TUBE CURRENT MODULATION Antonios E. Papadakis a, Kostas Perisinakis b, John Damilakis b. a University Hospital of Heraklion, Medical Physics Department, Heraklion, Crete, Greece; b University of Crete, Medical School, Medical Physics Department, Heraklion, Crete, Greece Background: The aim of this study was to investigate the effect of patient body habitus and modulation strength on radiation dose and image quality in CT examinations using automatic tube current modulation (ATCM). Materials and methods: Ten physical anthropomorphic phantoms that simulate the average individual as neonate, 1-, 5-, and 10-year-old and adult were employed. The 10-year-old and adult anthropomorphic phantoms were appropriately devised using custom made bolus material to simulate overweight and obese patients. Head, neck, thorax, and abdomen/pelvis helical acquisitions were performed in all phantoms using the standard pediatric and adult examination protocols specified for each
e53
anatomical region. Acquisitions were performed using a sixteen-slice CT scanner, which was equipped with an angular and z-axis ATCM system. CT acquisitions were performed at fixed tube current and with the ATCM system activated at three different modulation strength settings i.e. weak, average, and strong. Image noise was measured as the average standard deviation of the Hounsfield unit across regions of interest, which were drawn over uniform tissue equivalent areas. Results: The modulated mAs recorded for neonate compared to 10-yearold increased by 30%, 14%, 6%, and 53% for head, neck, thorax and abdomen/pelvis, respectively, (P<0.05). Fixed tube current and ATCMactivated acquisitions provided images of similar noise at a significant reduction of the modulated mAs with the exception of the 10-year-old phantom. In pediatric and adult phantoms, the modulated mAs ranged from 44 and 53 for weak to 117 and 93 for strong modulation strength, respectively. At the same exposure parameters image noise increased with body size (P<0.05). Discussion: The ATCM system investigated herein can effectively reduce patient radiation dose in adult individuals regardless their body habitus. However, ATCM may increase patient radiation dose in trunk CT examinations of children older than 5-year-old. Care should be taken when implementing ATCM protocols to ensure that image quality is maintained. AUTOMATIC QUANTIFICATION OF CONTRAST ENHANCED ULTRASOUND LIVER IMAGING Elias Gatos a, Stavros Tsantis a,b, Aikaterini Skouroliakou c, Ioannis Theotokas d, Pavlos S. Zoumpoulis d, George C. Kagadis a. a Department of Medical Physics, School of Medicine, University of Patras, GR 26504, Rion; b Department of Biomedical Engineering, Technological Educational Institute of Athens, GR 12210, Egaleo; c Department of Energy Technology Engineering, Technological Educational Institute of Athens, GR 12210, Egaleo; d Diagnostic Echotomography SA, 317C Kifissias Ave., GR 14561, Kifissia Background: Ultrasound contrast agent imaging (CEUS) has overcome the major limitation of classic Liver B-Mode and Doppler Ultrasound, and provided the ability to depict the parenchyma microvasculature. The enhancement pattern of Focal Liver lesions (FLLs) can be studied and evaluated in real time throughout all vascular phases (arterial, portal venous, late and postvascular phases). FLL characterization is currently performed either by means of visual inspection or by built-in software packages that provide low quality time-intensity curves without quantitative assessment. A new automatic method is proposed that initially detects an FLL and then provides time-intensity curves towards its characterization. Materials and methods: Twelve (12) CEUS image series of 12 patients with FLLs disease have been subjected for quantification into the proposed algorithm. A specifically designed detection algorithm was implemented to detect the FLL across frames and extract its contour. This particular lesion region represents the region of interest on CEUS images, from which the enhancement pattern and its type can be derived. The algorithm is based on unsupervised segmentation, utilizing the Markov Random Field model (MRF) and Continuous Wavelet Transform (CWT) employing the ‘Mexican Hat’ wavelet filter. The proposed algorithm employs textural and multi-scale wavelet coefficient information provided by CWT analysis. Wavelet analysis produces the initial clusters into the MRF procedure to minimize the number of iteration steps and to enhance the clustering speed. Results: Compared with manual segmentation by an expert physician, the lesion detected had an average overlap value of 0.92±0.02 for all CEUS videos included in the study. Following the lesion detection procedure time-intensity curves are computed and plotted from lesion and reference areas (Figure). In addition, several parameters are computed such as Area Under the Curve, Mean Transit Time, Perfusion Index, Rise Time and Time to Peak to strengthen the evaluation procedure. Discussion: A new promising tool has been implemented towards FLL detection and time Intensity curves analysis in CEUS data. After lesion detection, the degree and phase of lesion enhancement relative to the parenchyma is computed and visualized to evaluate the lesion character.