1. Utility of Virtual Non-Contrast Images in Assessment of Acute Intracranial Pathology
Mohammed F. Mohammed, Olivia Marais, Adam Min, Rawan Abu Mughli, Shamir Rai, Tim O’Connell, Axel Rohr, Savvas Nicolaou
University of British Columbia, Faculty of Medicine, Department of Radiology
RSNA 2017, “Emergency Radiology: Neuroradiology”, SSJ06, Room N22B , November 28th, 2017
Take out infarct stuff
“originally included detection of infarct.. But we modified this study to focus just on hemorrhage as infarct stuff was published in an IR study last year”.

2. Disclosures
None

3. CT imaging for stroke triage
Parenchyma - NCCT
Pipes - CTA
Perfusion - CTP
Penumbra - CTP
- The 4 P’s of stroke imaging
- A standard comprehensive stroke imaging protocol for triage
Dorn et al Neuroradiology (2012)

4. Dual Energy CT
A virtual non-contrast CT image can be reconstructed from DECT angiogram data using a three-material decomposition algorithm
May obviate need for an unenhanced CT in acute stroke protocols allowing for more rapid stroke diagnosis and therapy
Holy Grail: A single DECTA study that could provide data currently obtained with NCCT, CTA, and CTP acquisitions

5. Objective
Can DECTA-derived VNC images accurately detect INTRACRANIAL HEMORRHAGE in patients presenting to the Emergency Department with signs and symptoms of acute stroke?

6. Materials and Methods Retrospective, IRB-approved study
56 consecutive patients labelled as “Stroke Code Activations”
All <4h since symptom onset
All patients received a NCCT head and a DECT angiogram arch-vertex with Tube A: 90kV ; Tube B: 150kV with tin filter

7. VNC NCCT Datasets post-processed on syngo.via platform
3 material decomposition performed with base materials CSF, blood, and iodine
Iodine subtracted to create VNC image
Quantitative analysis of the TNC and VNC images performed using ROIs centered on the basal ganglia, internal capsule, and superior sagittal sinus of the unaffected hemisphere
Mean Hounsfield Units was calculated based on the three measurements

8. Mean attenuation values (HU)
VNC
NCCT
P-value
Basal ganglia
35.6
38.6
>0.1
Internal capsule
30.5
30.3
Superior sagittal sinus
56.2
56.5
And in fact we saw No significant difference in attenuation values
No significant difference in mean attenuation between VNC and NCCT images

9. Materials and Methods
Two radiologists – blinded to all patient data except side of symptoms – retrospectively interpreted VNC and NCCT images
Sensitivity and specificity of VNC compared to NCCT for detecting acute intracranial hemorrhage
Initially, also aimed to compare accuracy for detecting infarct
However, “Gariani et al. J Neurointerv Surg (2016)”
Modified our study to examine VNC for ICH only

10. A side-by-side comparison of TNC and VNC images
Here, a patient with obvious intra parenchymal hemorrhage
Clearly visible on the VNC image

11. NCCT VNC A side-by-side comparison of TNC and VNC images
Here, a patient with obvious intra parenchymal hemorrhage
Clearly visible on the VNC image

12. NCCT VNC A side-by-side comparison of TNC and VNC images
Here, a patient with obvious intra parenchymal hemorrhage
Clearly visible on the VNC image

13. A side-by-side comparison of TNC and VNC images
Here, a patient with obvious intra parenchymal hemorrhage
Clearly visible on the VNC image

16. VNC vs NCCT: Acute Intracranial Hemorrhage Bleed NCCT No Bleed NCCT
Bleed VNC 15
No Bleed VNC 41 56
Table comparing VNC to TNC for detecting intracranial hemorrhage
0s in these two boxes are good.
– VNC and TNC images correlated perfectly for ruling in or ruling out acute ICH
Perfect agreement between VNC and NCCT in detecting acute hemorrhage

17. Limitations
Small cohort
Retrospective study
No MRI as gold standard

18. Conclusions
VNC images were as reliable as NCCT images at ruling out intracranial hemorrhage in patients presenting to the ED with acute stroke symptoms.
Further study of VNC applied in head trauma to identify intracranial hemorrhage
Use of VNC in acute stroke imaging protocols may obviate the need for NCCT in acute stroke imaging protocols, thereby facilitating more rapid stroke diagnosis and therapy.
Vargas – Diagnosis of acute sichemia using dual energy CT after mechanical thrombectomy
Ours were not optimized to the other study… these are different parameters.. Not to decrease GWD in order to increase brain edema conspicuity
Focus on hem less on infarct
“if these images were used to detect infarct, they would be inferior”
Some evidence to go straight to CTA “skip, NCCT” – look up these studies
Cta as good as MRI - quote the investigative radiology paper in our recent paper
- Comparison of CT and CT angiography source images with diffusion-weighted imaging in patients with acute stroke within 6 hours after onset.Schramm P, Schellinger PD, Fiebach JB, Heiland S, Jansen O, Knauth M, Hacke W, Sartor K
Stroke Oct; 33(10):
- Comparison of perfusion computed tomography and computed tomography angiography source images with perfusion-weighted imaging and diffusion-weighted imaging in patients with acute stroke of less than 6 hours' duration.Schramm P, Schellinger PD, Klotz E, Kallenberg K, Fiebach JB, Külkens S, Heiland S, Knauth M, Sartor K
Stroke Jul; 35(7):
Add some slides with future directions – for trauma patients
Trauma: NCCT, CTA arch to vertex, CT Spine, Contrast chest and pelvis
Just skip the NCCT… go to contrast study....
However, we did not optimize DE application parameters for this purpose. Optimized VNC images were shown to actually increase conspicuity of acute infarct compared to NCCT in another study1
Gariani et al. J Neurointerv Surg (2016)

19. Thank you!

20. Conclusions
VNC images were as reliable as NCCT images at ruling out intracranial hemorrhage in patients presenting to the ED with acute stroke symptoms.
VNC was not as accurate as NCCT in detecting acute infarct.
Did not optimize DE parameters for this purpose
Gariani et al - Optimized VNC images increased conspicuity of acute infarct compared to NCCT1
Further study of VNC in head trauma
Use of VNC in acute stroke imaging protocols may obviate the need for NCCT in acute stroke imaging protocols, thereby facilitating more rapid stroke diagnosis and therapy.
Vargas – Diagnosis of acute sichemia using dual energy CT after mechanical thrombectomy
Ours were not optimized to the other study… these are different parameters.. Not to decrease GWD in order to increase brain edema conspicuity
Focus on hem less on infarct
“if these images were used to detect infarct, they would be inferior”
Some evidence to go straight to CTA “skip, NCCT” – look up these studies
Cta as good as MRI - quote the investigative radiology paper in our recent paper
- Comparison of CT and CT angiography source images with diffusion-weighted imaging in patients with acute stroke within 6 hours after onset.Schramm P, Schellinger PD, Fiebach JB, Heiland S, Jansen O, Knauth M, Hacke W, Sartor K
Stroke Oct; 33(10):
- Comparison of perfusion computed tomography and computed tomography angiography source images with perfusion-weighted imaging and diffusion-weighted imaging in patients with acute stroke of less than 6 hours' duration.Schramm P, Schellinger PD, Klotz E, Kallenberg K, Fiebach JB, Külkens S, Heiland S, Knauth M, Sartor K
Stroke Jul; 35(7):
Add some slides with future directions – for trauma patients
Trauma: NCCT, CTA arch to vertex, CT Spine, Contrast chest and pelvis
Just skip the NCCT… go to contrast study....
However, we did not optimize DE application parameters for this purpose. Optimized VNC images were shown to actually increase conspicuity of acute infarct compared to NCCT in another study1
Gariani et al. J Neurointerv Surg (2016)

21. Infarct NCCT No Infarct NCCT Infarct VNC 13 No Infarct VNC 21 22 43 34
VNC vs NCCT: Infarct
Infarct NCCT
No Infarct NCCT
Infarct VNC 13
No Infarct VNC 21 22 43 34 56
VNC vs NCCT: Hyperdense Vessel
VNC inferior to NCCT in detecting acute infarct
HDV NCCT
No HDV NCCT
HDV VNC 20 7 27
No HDV VNC 5 24 29 25 31 56
Same idea, but detecting acute infarct.
VNC lacked sensitivity in picking up infarct compared to TNC
21 of 56 patients, infarct would have been missed if VNC was used instead of TNC

22. This is an example of acute infarct that was visible on both TNC and VNC
rigth insula/ caudate head

24. Results Sensitivity and specificity of VNC images Sensitivity
Hemorrhage
100%
Infarction
38.2%
Hyperdense-vessel
80%
77.4%
- VNC was as accurate as TNC in picking up ICH, but lacked acurracy in detecting Infa

25. Results
VNC showed similar mean attenuation values compared to TNC in the basal ganglia, internal capsule, and superior sagittal sinus.
VNC images were:
As reliable as TNC images for detecting hemorrhage
Inferior to TNC for detecting acute infarction and hyperdense-vessel sign.

26. Materials and Methods
Two radiologists – blinded to all patient data except side of symptoms – retrospectively interpreted VNC and TNC images
Sensitivity and specificity of VNC compared to TNC for detecting:
Intracranial hemorrhage
Infarction
Hyperdense Vessel Sign
VNCs were rated on Likert Scale for diagnostic acceptability
1 = Non-diagnostic
5 = Strongly diagnosic

27. VNC for detecting acute infarct
Hypothesis for why we didn’t see infarct
VNC cannot replace TNC to diagnose acute infarct
However, CTA shows extent and distribution of infarct
In our study, VNC performed as well as TNC images at detecting hemorrhage
Lot of artifact along the bone…
Unoptimized, default settings.
Sadia

28. NCCT
VNC
This is an example of acute infarct that was visible on both TNC and VNC
rigth insula/ caudate head

29. A Dual-Energy CT protocol for acute stroke?
Conventional CT
DECT
Parenchyma
(Hemorrhage)
NCCT
DECTA (VNC)
Pipes
CTA
DECTA
Perfusion
(Core)
CTP
DECTA (Iodine Map)
Penumbra

30. TNC VNC Called a hyperdense left ICA on TNC
Difficult to appreciate on VNC

31. TNC VNC Another good example of VNC
On TNC, loss of GWD along right insular border, and hypoattenuation of the lentiform nucleus
Also appreciable on VNC

32. TNC VNC An example where it was more difficult to see on VNC
- On TNC, loss of Grey-white differentiation along right insula
- subtle on the VNC – hard to appreciate normal GWD on Left