Clinical Radiology xxx (2015) 1e10
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Low-dose CT angiography of the abdominal aorta and reduced contrast medium volume: Assessment of image quality and radiation dose W.H. Nijhof a, c, *, E.J.M. Baltussen a, I.M.J. Kant a, G.J. Jager b, C.H. Slump c, M.J.C.M. Rutten b a
MIRA-Institute for Biomedical Technology and Technical Medicine, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, The Netherlands b Department of Radiology, Jeroen Bosch Hospital, Henri Dunantstraat 1, 5223 GZ, ‘s-Hertogenbosch, The Netherlands c Signals and Systems, Department of Electrical Engineering, University of Twente, 7500 AE, Enschede, The Netherlands
art icl e i nformat ion Article history: Received 16 March 2015 Received in revised form 8 September 2015 Accepted 5 October 2015
AIM: To determine the effect of using 80 kV tube voltage and a reduced amount of contrast medium on the image quality and radiation dose of computed tomography angiography (CTA) of the abdominal aorta. MATERIALS AND METHODS: Patients who were referred for a CTA examination of the abdominal aorta were included in this technical efficacy study. Thirty patients were divided randomly into two groups. Fifteen patients underwent a dual-energy CT (DECT) protocol (Group A). Fifteen patients were scanned with the use of an automated tube potential selection algorithm tool (Group B). In both protocols, a test bolus injection of 10 ml ioversol (350 mg iodine/ml) was used, followed by 20 ml of 1:1 saline-diluted contrast medium. Quantitative analysis comprised determination of the mean attenuation and contrast-to-noise ratio. Qualitative image analysis was performed independently by five radiologists. The estimated radiation dose in terms of CT dose index and effective dose was recorded and compared with a standard 120 kV protocol. RESULTS: In Group B, six patients underwent CTA at 80 kV, seven patients underwent CTA at 100 kV and two patients underwent CTA at 120 kV. The mean contrast-enhancement values of Group A (80 kV) and the 80 kV subgroup of Group B were 16.5% and 27.6% higher compared to the 100 kV subgroup of Group B, these differences were, however, not significant. There were no significant differences in mean image quality between groups. In patients undergoing CTA at 80 kV the effective dose decreased by up to 51.3% compared to a conventional 120 kV CTA protocol. CONCLUSIONS: The findings of this study support the hypothesis that 80 kV in CTA of the abdominal aorta can reliably be used with only 30 ml contrast medium in total and a 50% reduction in radiation dose. The overall image quality was diagnostically adequate; however, it appeared to be suboptimal in patients with a BMI above 28 kg/m2. Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
* Guarantor and correspondent: W. H. Nijhof, University of Twente, MIRAInstitute for Biomedical Technology and Technical Medicine, P.O. Box 21, 7500 AE, Enschede, The Netherlands. Tel.: þ31 642731212. E-mail address: [email protected] (W.H. Nijhof). http://dx.doi.org/10.1016/j.crad.2015.10.007 0009-9260/Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Nijhof WH, et al., Low-dose CT angiography of the abdominal aorta and reduced contrast medium volume: Assessment of image quality and radiation dose, Clinical Radiology (2015), http://dx.doi.org/10.1016/j.crad.2015.10.007
2
W.H. Nijhof et al. / Clinical Radiology xxx (2015) 1e10
Introduction Over the past decade, there has been dramatic growth worldwide in contrast-enhanced computed tomography (CT) examinations, such as CT angiography (CTA).1 Concerns have been raised regarding the potential risk of radiationinduced cancer from CT examinations,2 and the risk of contrast-induced nephropathy (CIN) after intravascular administration of iodinated contrast medium (CM).3 Over the last few years, various techniques and patientbased strategies have been developed to reduce the radiation dose delivered during CT examinations. These techniques include lowering of the tube voltage (kV),4e6 the use of automated tube current modulation,7 high-pitch CT,8 and iterative reconstruction algorithms.9,10 A recent study showed that lowering the tube voltage to 80 kV for CTA of the body resulted in an average dose reduction of 40% compared to the standard protocol employing 120 kV.11 Sigal-Cinqualbre et al.12 were the first to hypothesise that low kilo-voltage scanning might facilitate the reduction in iodine load by increasing vasculature enhancement due to the lower effective energy closer to the K-edge (33.2 keV) of iodine. Lowering the tube voltage is, therefore, capable of reducing the radiation dose and iodine load while maintaining diagnostic image quality.6 The disadvantage of low tube voltage CT is the nonlinear increase in image noise,13 and therefore, the decrease in image quality. To determine whether image quality is still adequate when the tube voltage is lowered, the present abdominal aorta CTA study was conducted in which an 80 kV protocol was used with a total volume of 30 ml CM. The purpose of the study was to determine the effect of using 80 kV tube voltage and a reduced amount of CM volume on the image quality and radiation dose of CTA of the abdominal aorta.
Materials and methods Study design A prospective, technical efficacy study in patients referred for CTA of the abdominal aorta was performed. The study protocol was approved by the institutional ethical review board. Indications for referral were preoperative work-up in abdominal aortic aneurysm (AAA), postoperative AAA control, and imaging of the renal and gastrointestinal arteries. General exclusion criteria included allergy to CM, mental incompetence, known arrhythmias or other heart disorders, impaired renal function (estimated glomerular rate
Contents lists available at ScienceDirect
Clinical Radiology journal homepage: www.clinicalradiologyonline.net
Low-dose CT angiography of the abdominal aorta and reduced contrast medium volume: Assessment of image quality and radiation dose W.H. Nijhof a, c, *, E.J.M. Baltussen a, I.M.J. Kant a, G.J. Jager b, C.H. Slump c, M.J.C.M. Rutten b a
MIRA-Institute for Biomedical Technology and Technical Medicine, University of Twente, Drienerlolaan 5, 7522 NB, Enschede, The Netherlands b Department of Radiology, Jeroen Bosch Hospital, Henri Dunantstraat 1, 5223 GZ, ‘s-Hertogenbosch, The Netherlands c Signals and Systems, Department of Electrical Engineering, University of Twente, 7500 AE, Enschede, The Netherlands
art icl e i nformat ion Article history: Received 16 March 2015 Received in revised form 8 September 2015 Accepted 5 October 2015
AIM: To determine the effect of using 80 kV tube voltage and a reduced amount of contrast medium on the image quality and radiation dose of computed tomography angiography (CTA) of the abdominal aorta. MATERIALS AND METHODS: Patients who were referred for a CTA examination of the abdominal aorta were included in this technical efficacy study. Thirty patients were divided randomly into two groups. Fifteen patients underwent a dual-energy CT (DECT) protocol (Group A). Fifteen patients were scanned with the use of an automated tube potential selection algorithm tool (Group B). In both protocols, a test bolus injection of 10 ml ioversol (350 mg iodine/ml) was used, followed by 20 ml of 1:1 saline-diluted contrast medium. Quantitative analysis comprised determination of the mean attenuation and contrast-to-noise ratio. Qualitative image analysis was performed independently by five radiologists. The estimated radiation dose in terms of CT dose index and effective dose was recorded and compared with a standard 120 kV protocol. RESULTS: In Group B, six patients underwent CTA at 80 kV, seven patients underwent CTA at 100 kV and two patients underwent CTA at 120 kV. The mean contrast-enhancement values of Group A (80 kV) and the 80 kV subgroup of Group B were 16.5% and 27.6% higher compared to the 100 kV subgroup of Group B, these differences were, however, not significant. There were no significant differences in mean image quality between groups. In patients undergoing CTA at 80 kV the effective dose decreased by up to 51.3% compared to a conventional 120 kV CTA protocol. CONCLUSIONS: The findings of this study support the hypothesis that 80 kV in CTA of the abdominal aorta can reliably be used with only 30 ml contrast medium in total and a 50% reduction in radiation dose. The overall image quality was diagnostically adequate; however, it appeared to be suboptimal in patients with a BMI above 28 kg/m2. Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
* Guarantor and correspondent: W. H. Nijhof, University of Twente, MIRAInstitute for Biomedical Technology and Technical Medicine, P.O. Box 21, 7500 AE, Enschede, The Netherlands. Tel.: þ31 642731212. E-mail address: [email protected] (W.H. Nijhof). http://dx.doi.org/10.1016/j.crad.2015.10.007 0009-9260/Ó 2015 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Nijhof WH, et al., Low-dose CT angiography of the abdominal aorta and reduced contrast medium volume: Assessment of image quality and radiation dose, Clinical Radiology (2015), http://dx.doi.org/10.1016/j.crad.2015.10.007
2
W.H. Nijhof et al. / Clinical Radiology xxx (2015) 1e10
Introduction Over the past decade, there has been dramatic growth worldwide in contrast-enhanced computed tomography (CT) examinations, such as CT angiography (CTA).1 Concerns have been raised regarding the potential risk of radiationinduced cancer from CT examinations,2 and the risk of contrast-induced nephropathy (CIN) after intravascular administration of iodinated contrast medium (CM).3 Over the last few years, various techniques and patientbased strategies have been developed to reduce the radiation dose delivered during CT examinations. These techniques include lowering of the tube voltage (kV),4e6 the use of automated tube current modulation,7 high-pitch CT,8 and iterative reconstruction algorithms.9,10 A recent study showed that lowering the tube voltage to 80 kV for CTA of the body resulted in an average dose reduction of 40% compared to the standard protocol employing 120 kV.11 Sigal-Cinqualbre et al.12 were the first to hypothesise that low kilo-voltage scanning might facilitate the reduction in iodine load by increasing vasculature enhancement due to the lower effective energy closer to the K-edge (33.2 keV) of iodine. Lowering the tube voltage is, therefore, capable of reducing the radiation dose and iodine load while maintaining diagnostic image quality.6 The disadvantage of low tube voltage CT is the nonlinear increase in image noise,13 and therefore, the decrease in image quality. To determine whether image quality is still adequate when the tube voltage is lowered, the present abdominal aorta CTA study was conducted in which an 80 kV protocol was used with a total volume of 30 ml CM. The purpose of the study was to determine the effect of using 80 kV tube voltage and a reduced amount of CM volume on the image quality and radiation dose of CTA of the abdominal aorta.
Materials and methods Study design A prospective, technical efficacy study in patients referred for CTA of the abdominal aorta was performed. The study protocol was approved by the institutional ethical review board. Indications for referral were preoperative work-up in abdominal aortic aneurysm (AAA), postoperative AAA control, and imaging of the renal and gastrointestinal arteries. General exclusion criteria included allergy to CM, mental incompetence, known arrhythmias or other heart disorders, impaired renal function (estimated glomerular rate
