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Reply: REPLY: In conclusion, DECT is a promising technique, but its role in spot sign identification is still unclear. e thank Drs Vargas and Lovblad for their interest and com- Wments on our article investigating the influence of CTA REFERENCES tube current on spot sign detection and prediction of intracere- 1. Gupta R, Phan CM, Leidecker C, et al. Evaluation of dual-energy bral hemorrhage expansion. The role of dual-energy CT (DECT) CT for differentiating intracerebral hemorrhage from iodinated contrast material staining. Radiology 2010;257:205–11 CrossRef in spot sign identification has not been extensively and systemat- Medline ically investigated, to our knowledge, and we agree that more 2. Phan CM, Yoo AJ, Hirsch JA, et al. Differentiation of hemorrhage research on the use of this technique is needed. DECT can distin- from iodinated contrast in different intracranial compartments us- guish different types of materials with high sensitivity and speci- ing dual-energy head CT. AJNR Am J Neuroradiol 2012;33:1088–94 1,2 ficity. As shown in the figure provided by Drs Vargas and CrossRef Medline 3. Huynh TJ, Demchuk AM, Dowlatshahi D, et al; PREDICT/Sunny- Lovblad, DECT can remove spots of iodine extraction from the brook ICH CTA Study Group. Spot sign number is the most impor- virtual noncontrast images and map them to the iodine-overlay tant spot sign characteristic for predicting hematoma expansion images. The degree to which this separation is effective and the using first-pass computed tomography angiography: analysis from minimum concentration of extravasated iodine separable from the PREDICT study. Stroke 2013;44:972–77 CrossRef Medline hematoma, in situ, are currently unknown. Therefore, how the 4. Brouwers HB, Goldstein JN, Romero JM, et al. Clinical applications of the computed tomography angiography spot sign in acute intra- single-energy CT spot sign should be translated in the context of cerebral hemorrhage: a review. Stroke 2012;43:3427–32 CrossRef dual-energy remains a topic of research. For example, it is not Medline clear whether one should be counting the number of spots on the 5. Ciura VA, Brouwers HB, Pizzolato R, et al. Spot sign on 90-second iodine-overlay images or computing the total amount of extrav- delayed computed tomography angiography improves sensitivity asated iodine in the iodine-overlay images. We would like to high- for hematoma expansion and mortality: prospective study. Stroke 2014;45:3293–97 CrossRef Medline light the following additional points: 6. Du F, Jiang R, Gu M, et al. The accuracy of spot sign in predicting 1) There is great heterogeneity in the CTA acquisition proto- hematoma expansion after intracerebral hemorrhage: a systematic col, and several factors such as the time from stroke onset to CTA review and meta-analysis. PLoS One 2014;9:e115777 CrossRef 4,5 and acquisition of delayed images can influence the rate of spot Medline sign identification and its ability to identify patients at high risk of 7. Postma AA, Das M, Stadler AA, et al. Dual-energy CT: what the neuroradiologist should know. Curr Radiol Rep 2015;3:16 CrossRef hematoma expansion. Therefore, the relatively low sensitivity 6 Medline (53%) reported by Du et al in a recent meta-analysis cannot be 8. Gazzola S, Aviv RI, Gladstone DJ, et al. Vascular and nonvascular directly attributed to the use of DECT. mimics of the CT angiography “spot sign” in patients with second- 2) It is difficult to compare the frequency and diagnostic per- ary intracerebral hemorrhage. Stroke 2008;39:1177–83 CrossRef formance of the spot sign across different studies because several Medline 9. Smith AB, Dillon WP, Gould R, et al. Radiation dose-reduction definitions of spot sign and hematoma expansion have been re- 4 strategies for neuroradiology CT protocols. AJNR Am J Neuroradiol ported and used in clinical practice. 2007;28:1628–32 CrossRef Medline 3) DECT has the ability to reduce artifacts and to remodel the X A. Morotti signal-to-noise ratio and may therefore provide an additional Department of Clinical and Experimental Sciences, Neurology Clinic University of Brescia, Brescia, Italy diagnostic value in case of poor-quality scans. J. P. Kistler Stroke Research Center 4) Vascular and nonvascular cerebral lesions like aneurysms or Massachusetts General Hospital, Harvard Medical School calcifications can mimic the spot sign, and DECT appears supe- Boston, Massachusetts X J.M. Romero rior to conventional CTA in the identification of these mimics. X R. Gupta 5) There are multiple implementations of DECT, and not all of Neuroradiology Service, Department of Radiology them are dose-neutral compared with a single-energy CT scan. In Massachusetts General Hospital, Harvard Medical School Boston, Massachusetts general, the advantages of DECT use need to be balanced against X J.N. Goldstein the risk of increased radiation delivery. J. P. Kistler Stroke Research Center Department of Emergency Medicine Massachusetts General Hospital, Harvard Medical School http://dx.doi.org/10.3174/ajnr.A4887 Boston, Massachusetts E64 Letters Oct 2016 www.ajnr.org http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png American Journal of Neuroradiology American Journal of Neuroradiology

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Publisher
American Journal of Neuroradiology
Copyright
© 2016 by American Journal of Neuroradiology
ISSN
0195-6108
eISSN
1936-959X
DOI
10.3174/ajnr.A4887
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Abstract

REPLY: In conclusion, DECT is a promising technique, but its role in spot sign identification is still unclear. e thank Drs Vargas and Lovblad for their interest and com- Wments on our article investigating the influence of CTA REFERENCES tube current on spot sign detection and prediction of intracere- 1. Gupta R, Phan CM, Leidecker C, et al. Evaluation of dual-energy bral hemorrhage expansion. The role of dual-energy CT (DECT) CT for differentiating intracerebral hemorrhage from iodinated contrast material staining. Radiology 2010;257:205–11 CrossRef in spot sign identification has not been extensively and systemat- Medline ically investigated, to our knowledge, and we agree that more 2. Phan CM, Yoo AJ, Hirsch JA, et al. Differentiation of hemorrhage research on the use of this technique is needed. DECT can distin- from iodinated contrast in different intracranial compartments us- guish different types of materials with high sensitivity and speci- ing dual-energy head CT. AJNR Am J Neuroradiol 2012;33:1088–94 1,2 ficity. As shown in the figure provided by Drs Vargas and CrossRef Medline 3. Huynh TJ, Demchuk AM, Dowlatshahi D, et al; PREDICT/Sunny- Lovblad, DECT can remove spots of iodine extraction from the brook ICH CTA Study Group. Spot sign number is the most impor- virtual noncontrast images and map them to the iodine-overlay tant spot sign characteristic for predicting hematoma expansion images. The degree to which this separation is effective and the using first-pass computed tomography angiography: analysis from minimum concentration of extravasated iodine separable from the PREDICT study. Stroke 2013;44:972–77 CrossRef Medline hematoma, in situ, are currently unknown. Therefore, how the 4. Brouwers HB, Goldstein JN, Romero JM, et al. Clinical applications of the computed tomography angiography spot sign in acute intra- single-energy CT spot sign should be translated in the context of cerebral hemorrhage: a review. Stroke 2012;43:3427–32 CrossRef dual-energy remains a topic of research. For example, it is not Medline clear whether one should be counting the number of spots on the 5. Ciura VA, Brouwers HB, Pizzolato R, et al. Spot sign on 90-second iodine-overlay images or computing the total amount of extrav- delayed computed tomography angiography improves sensitivity asated iodine in the iodine-overlay images. We would like to high- for hematoma expansion and mortality: prospective study. Stroke 2014;45:3293–97 CrossRef Medline light the following additional points: 6. Du F, Jiang R, Gu M, et al. The accuracy of spot sign in predicting 1) There is great heterogeneity in the CTA acquisition proto- hematoma expansion after intracerebral hemorrhage: a systematic col, and several factors such as the time from stroke onset to CTA review and meta-analysis. PLoS One 2014;9:e115777 CrossRef 4,5 and acquisition of delayed images can influence the rate of spot Medline sign identification and its ability to identify patients at high risk of 7. Postma AA, Das M, Stadler AA, et al. Dual-energy CT: what the neuroradiologist should know. Curr Radiol Rep 2015;3:16 CrossRef hematoma expansion. Therefore, the relatively low sensitivity 6 Medline (53%) reported by Du et al in a recent meta-analysis cannot be 8. Gazzola S, Aviv RI, Gladstone DJ, et al. Vascular and nonvascular directly attributed to the use of DECT. mimics of the CT angiography “spot sign” in patients with second- 2) It is difficult to compare the frequency and diagnostic per- ary intracerebral hemorrhage. Stroke 2008;39:1177–83 CrossRef formance of the spot sign across different studies because several Medline 9. Smith AB, Dillon WP, Gould R, et al. Radiation dose-reduction definitions of spot sign and hematoma expansion have been re- 4 strategies for neuroradiology CT protocols. AJNR Am J Neuroradiol ported and used in clinical practice. 2007;28:1628–32 CrossRef Medline 3) DECT has the ability to reduce artifacts and to remodel the X A. Morotti signal-to-noise ratio and may therefore provide an additional Department of Clinical and Experimental Sciences, Neurology Clinic University of Brescia, Brescia, Italy diagnostic value in case of poor-quality scans. J. P. Kistler Stroke Research Center 4) Vascular and nonvascular cerebral lesions like aneurysms or Massachusetts General Hospital, Harvard Medical School calcifications can mimic the spot sign, and DECT appears supe- Boston, Massachusetts X J.M. Romero rior to conventional CTA in the identification of these mimics. X R. Gupta 5) There are multiple implementations of DECT, and not all of Neuroradiology Service, Department of Radiology them are dose-neutral compared with a single-energy CT scan. In Massachusetts General Hospital, Harvard Medical School Boston, Massachusetts general, the advantages of DECT use need to be balanced against X J.N. Goldstein the risk of increased radiation delivery. J. P. Kistler Stroke Research Center Department of Emergency Medicine Massachusetts General Hospital, Harvard Medical School http://dx.doi.org/10.3174/ajnr.A4887 Boston, Massachusetts E64 Letters Oct 2016 www.ajnr.org

Journal

American Journal of Neuroradiology – American Journal of Neuroradiology

Published: Oct 1, 2016

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