Phantom-based standardization of CT angiography images for spot sign detection

Andrea Morotti^{1

2}, Javier M Romero^{3

4

5}, Michael J Jessel⁴, Andrew M Hernandez⁶, Anastasia Vashkevich⁴, Kristin Schwab⁴, Joseph D Burns⁷, Qaisar A Shah⁸, Thomas A Bergman⁹, M Fareed K Suri¹⁰, Mustapha Ezzeddine¹¹, Jawad F Kirmani¹², Sachin Agarwal¹³, Angela Hays Shapshak¹⁴, Steven R Messe¹⁵, Chitra Venkatasubramanian¹⁶, Katherine Palmieri¹⁷, Christopher Lewandowski¹⁸, Tiffany R Chang¹⁹, Ira Chang²⁰, David Z Rose²¹, Wade Smith²², Chung Y Hsu²³, Chun-Lin Liu²³, Li-Ming Lien²⁴, Chen-Yu Hsiao²⁴, Toru Iwama²⁵, Mohammad Rauf Afzal²⁶, Christy Cassarly²⁷, Steven M Greenberg⁴, Renee' Hebert Martin²⁷, Adnan I Qureshi²⁶, Jonathan Rosand^{3

4}, John M Boone⁶, Joshua N Goldstein^{3

4

28}; ATACH-II and NETT Investigators

Affiliations

¹ Division of Neurocritical Care and Emergency Neurology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA. a.morotti@ymail.com.
² J. P. Kistler Stroke Research Center, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge Street, Suite 300, Boston, MA, 02114, USA. a.morotti@ymail.com.
³ Division of Neurocritical Care and Emergency Neurology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
⁴ J. P. Kistler Stroke Research Center, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge Street, Suite 300, Boston, MA, 02114, USA.
⁵ Neuroradiology Service, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
⁶ Department of Radiology, University of California Davis, Sacramento, CA, USA.
⁷ Department of Neurology, Lahey Hospital and Medical Center, Burlington, MA, USA.
⁸ Abington Memorial Hospital, Abington, PA, USA.
⁹ Hennepin County Medical Center, Minneapolis, MN, USA.
¹⁰ St. Cloud Hospital, St. Cloud, MN, USA.
¹¹ University of Minnesota, Minneapolis, MN, USA.
¹² Stroke & Neurovascular Center, JFK Medical Center, Edison, NJ, USA.
¹³ Columbia University Medical Center, New York, NY, USA.
¹⁴ University of Alabama at Birmingham, Birmingham, AL, USA.
¹⁵ University of Pennsylvania, Philadelphia, PA, USA.
¹⁶ Stanford University, Stanford, CA, USA.
¹⁷ The University of Kansas Health System, Kansas City, KS, USA.
¹⁸ Henry Ford Hospital, Detroit, MI, USA.
¹⁹ University of Texas Medical School, Houston, TX, USA.
²⁰ Colorado Neurological Institute, Swedish Medical Center, Englewood, CO, USA.
²¹ Tampa General Hospital, University of South Florida College of Medicine, Tampa, FL, USA.
²² UCSF Medical Center, San Francisco, CA, USA.
²³ China Medical University Hospital, Taichung, Taiwan.
²⁴ Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
²⁵ Gifu University Hospital, Gifu, Japan.
²⁶ Zeenat Qureshi Stroke Research Center, University of Minnesota, Minneapolis, MN, USA.
²⁷ Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC, USA.
²⁸ Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.

PMID: 28730267
PMCID: PMC5700841
DOI: 10.1007/s00234-017-1857-4

Multicenter Study

Phantom-based standardization of CT angiography images for spot sign detection

Andrea Morotti et al. Neuroradiology. 2017 Sep.

. 2017 Sep;59(9):839-844.

doi: 10.1007/s00234-017-1857-4. Epub 2017 Jul 20.

Authors

Affiliations

¹ Division of Neurocritical Care and Emergency Neurology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA. a.morotti@ymail.com.
² J. P. Kistler Stroke Research Center, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge Street, Suite 300, Boston, MA, 02114, USA. a.morotti@ymail.com.
³ Division of Neurocritical Care and Emergency Neurology, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, 02114, USA.
⁴ J. P. Kistler Stroke Research Center, Massachusetts General Hospital, Harvard Medical School, 175 Cambridge Street, Suite 300, Boston, MA, 02114, USA.
⁵ Neuroradiology Service, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
⁶ Department of Radiology, University of California Davis, Sacramento, CA, USA.
⁷ Department of Neurology, Lahey Hospital and Medical Center, Burlington, MA, USA.
⁸ Abington Memorial Hospital, Abington, PA, USA.
⁹ Hennepin County Medical Center, Minneapolis, MN, USA.
¹⁰ St. Cloud Hospital, St. Cloud, MN, USA.
¹¹ University of Minnesota, Minneapolis, MN, USA.
¹² Stroke & Neurovascular Center, JFK Medical Center, Edison, NJ, USA.
¹³ Columbia University Medical Center, New York, NY, USA.
¹⁴ University of Alabama at Birmingham, Birmingham, AL, USA.
¹⁵ University of Pennsylvania, Philadelphia, PA, USA.
¹⁶ Stanford University, Stanford, CA, USA.
¹⁷ The University of Kansas Health System, Kansas City, KS, USA.
¹⁸ Henry Ford Hospital, Detroit, MI, USA.
¹⁹ University of Texas Medical School, Houston, TX, USA.
²⁰ Colorado Neurological Institute, Swedish Medical Center, Englewood, CO, USA.
²¹ Tampa General Hospital, University of South Florida College of Medicine, Tampa, FL, USA.
²² UCSF Medical Center, San Francisco, CA, USA.
²³ China Medical University Hospital, Taichung, Taiwan.
²⁴ Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
²⁵ Gifu University Hospital, Gifu, Japan.
²⁶ Zeenat Qureshi Stroke Research Center, University of Minnesota, Minneapolis, MN, USA.
²⁷ Department of Public Health Sciences, Medical University of South Carolina, Charleston, SC, USA.
²⁸ Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.

PMID: 28730267
PMCID: PMC5700841
DOI: 10.1007/s00234-017-1857-4

Abstract

Purpose: The CT angiography (CTA) spot sign is a strong predictor of hematoma expansion in intracerebral hemorrhage (ICH). However, CTA parameters vary widely across centers and may negatively impact spot sign accuracy in predicting ICH expansion. We developed a CT iodine calibration phantom that was scanned at different institutions in a large multicenter ICH clinical trial to determine the effect of image standardization on spot sign detection and performance.

Methods: A custom phantom containing known concentrations of iodine was designed and scanned using the stroke CT protocol at each institution. Custom software was developed to read the CT volume datasets and calculate the Hounsfield unit as a function of iodine concentration for each phantom scan. CTA images obtained within 8 h from symptom onset were analyzed by two trained readers comparing the calibrated vs. uncalibrated density cutoffs for spot sign identification. ICH expansion was defined as hematoma volume growth >33%.

Results: A total of 90 subjects qualified for the study, of whom 17/83 (20.5%) experienced ICH expansion. The number of spot sign positive scans was higher in the calibrated analysis (67.8 vs 38.9% p < 0.001). All spot signs identified in the non-calibrated analysis remained positive after calibration. Calibrated CTA images had higher sensitivity for ICH expansion (76 vs 52%) but inferior specificity (35 vs 63%) compared with uncalibrated images.

Conclusion: Normalization of CTA images using phantom data is a feasible strategy to obtain consistent image quantification for spot sign analysis across different sites and may improve sensitivity for identification of ICH expansion.

Keywords: CT angiography; Intracerebral hemorrhage; Phantom standardization; Spot sign.

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Figures

**Figure 1. Custom Phantom for CTA calibration**
A) Phantom containing a rod with six specific sections with different iodine concentrations; B) CT coronal images of the phantom; C) Calibration curve (linear relationship between iodine concentration and HU values). CTA indicates CT angiography; HU, Hounsfield Units.

**Figure 2. Comparison between calibrated vs non-calibrated spot sign analysis**
A) Baseline NCCT scan, ICH volume = 11 mL; B) CTA with 114 HU spot sign (negative with standard 120 HU threshold – positive with calibrated 100 HU threshold); C) Follow-up NCCT scan showing hematoma expansion, ICH volume = 36 mL. NCCT indicates non-contrast CT; CTA, CT angiography; HU, Hounsfield Units.

See this image and copyright information in PMC

References

1. Demchuk AM, Dowlatshahi D, Rodriguez-Luna D, et al. Prediction of haematoma growth and outcome in patients with intracerebral haemorrhage using the CT-angiography spot sign (PREDICT): A prospective observational study. Lancet Neurol. 2012;11:307–314. - PubMed
1. Goldstein JN, Fazen LE, Snider R, et al. Contrast extravasation on CT angiography predicts hematoma expansion in intracerebral hemorrhage. Neurology. 2007;68:889–94. - PubMed
1. Brouwers HB, Battey TWK, Musial HH, et al. Rate of Contrast Extravasation on Computed Tomographic Angiography Predicts Hematoma Expansion and Mortality in Primary Intracerebral Hemorrhage. Stroke. 2015;46:2498–2503. - PMC - PubMed
1. Brouwers HB, Raffeld MR, van Nieuwenhuizen KM, et al. CT angiography spot sign in intracerebral hemorrhage predicts active bleeding during surgery. Neurology. 2014;83:883–9. - PMC - PubMed
1. Burkhardt J-K, Neidert MC, Stienen MN, et al. Computed tomography angiography spot sign predicts intraprocedural aneurysm rupture in subarachnoid hemorrhage. Acta Neurochir (Wien) 2017 - PubMed

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Phantom-based standardization of CT angiography images for spot sign detection

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Phantom-based standardization of CT angiography images for spot sign detection

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