1. Neuro Best Contrast Filter for Head CT
XIX Symposium Neuroradiologicum
Evaluation of
Neuro Best Contrast Filter
for Head CT
Z. Rumboldt, S. Tipnis, D. Vincent,
M.V. Spampinato, G. Goldsberry, W. Huda
Medical University of South Carolina
Charleston, SC, USA

2. Background CT images traditionally reconstructed
using filtered back projection techniques
(FBP)
FBP limitations: geometry,
data completeness, radiation dose
Increased spatial resolution is directly
correlated with increased image noise

3. Facts Analysis Diagnostic value of CT images is limited
by the available contrast-to-noise ratio (CNR)
CNR is small particularly for soft tissue
(with low contrast)
CNR improvement by higher dose is undesirable
Analysis
Image noise is dominated by high spatial frequencies
Soft tissue representation (low contrast detectability) mainly depends on medium/low frequencies
 Image enhancement by frequency band-selective processing

4. noise divided by contrast
spatial frequency
noise divided by contrast
high freq. band
low freq. band
details with high contrast (vessels, bone, …)
soft tissue
contrast

5. Decomposition into Frequency Bands
high pass
sharp details and major part of noise
complementary filters
low pass
smooth content, but little noise

6. Multiband Image Enhancement (MBE) I
small details
high pass
complementary filters +
low pass
non-linear look-up
original image
enhanced image
contrast enhancement without substantial increase of noise

7. original image
NBC image

8. MBE improves CNR of specific image features
Head: gray/white matter differentiation
(CNR gain up to ~40%)
CNR improvement can be translated into radiation dose reduction
30% less dose demonstrated in example
realistic in general: 20% (further clinical studies needed)

9. Background

10. Purpose NBC Evaluation in a Clinical Setting
Novel Methodology for lesion detection
Comparison with normal scans with
the same filter,
not the same scan with different filters
side by side

11. Materials and Methods Part 1 5 consecutive Head CT scans with FBP
7 consecutive Head CT scans with NBC
HU measurements – circular ROI
Part 2
Novel Methodology for lesion detection

12. Materials and Methods Total screened 228
Age range selected 25 through 85
Both genders
24 abnormal subjects - 30 lesions:
21 hypointense
7 hyperintense
1 mixed
1 isointense
12 normal subjects selected to match

13. Materials and Methods In house software (MUSC, Matthew Daniels,
website accessible on campus network)
Displayed pairs of single slice CT - Abnormal on Left
Location and description of lesion given
Rating scale 1 to 10 1 = Barely discernable
10 = Definitely see lesion
PATHOLOGY COMPARED TO THE NORMAL
3 sets for each pair: FBP, NBC, IRIS

14. Materials and Methods Analysis Ratios of obtained values: NBC/FBP
Every reader trained on practice set prior to study
Individual randomization for every reader
Every reader trained on practice set prior to study
Individual randomization for every reader
Materials and Methods
Every reader trained on practice set prior to study
Individual randomization for every reader
Analysis
Ratios of obtained values: NBC/FBP
IRIS/FBP

15. Materials and Methods
FBP
IRIS
NBC

16. Materials and Methods
FBP

17. Materials and Methods
IRIS

18. Materials and Methods
NBC

19. Results FBP Part 1 CSF FAT BONE GM WM 39.83 32.30 42.71 34.62 40.49
10.72
-91.52
1166
39.83
32.30
11.7
-2.6
1158
42.71
34.62
10.14
-73.01
1124
40.49
32.41
8.511
-62.14
938
38.55
31.97
10.85
-98
734
39.68
33.37
8.45
-101
1005
37.28
32.73
6.68
-80.71
849.9
38.15
32.45
9.5787
1.7583
1.7829
0.8987

20. Results NBC CSF FAT BONE GM WM 5.1 -107 901 37.00 26.00 4.3 -81.9 1009
37.42
26.62
0.05
-99.33
963.4
34.13
24.61
5.2
-84.98
917
38.46
30.80
4.9
-90.66
1019
36.90
27.80
2.8
-76
1219
37.40
24.11
1.53
-64.48
869
33.54
21.61
5.9
-82
763
37.69
26.48
3.77
-105
738.2
36.71
26.21

21. Results GM WM 39.53 32.84 FBP 36.58 26.03 NBC CSF FAT BONE 9.5787
39.53
32.84
1.7583
1.7829
0.8987
FBP
3.7277
36.58
26.03
1.8162
1.5522
2.3969
NBC

22. Results mean difference in HU between GM and WM:
6.69 with standard FBP
10.55 using NBC
Avg. increase 3.86 HU
NBC
FBP

23. NBC/FBP lesion detection ratio
Part 2
NBC/FBP lesion detection ratio
AVG. HYPO RATIO
1.34
1.69
1.07
SD HYPO RATIO
0.77
2.13
0.43
AVG. HYPER RATIO
1.51
1.12
1.02
SD HYPER RATIO
0.72
0.48
0.18
AVG. RATIO
1.45
1.54
1.09
SD RATIO
0.82
1.82
0.41
Rater 1
Rater 2
Rater 3

24. Pooled Results – all 3 raters
NBC/FBP
Pooled Avg. Hypo
1.37
Pooled Std.Dev. Hypo
1.34
Pooled Avg. Hyper
1.22
Pooled Std.Dev. Hyper
0.53
Pooled Average
1.36
Pooled Std. Dev
1.18

25. Conclusion NBC filter provides increased contrast
between GM and WM on Head CT scans,
which seems to improve lesion detection
Alternatively, it may allow for
a decrease in radiation dose