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Improved Conspicuity of Abdominal Improved Conspicuity of Abdominal Lesions with Lesions with
Single-Source Dual-Energy MDCTSingle-Source Dual-Energy MDCT
Hadassah Hebrew University Medical CenterJerusalem, Israel
Ruth Eliahou MD, Jacob Sosna, MD
AFIIM 2008
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1972 – First single slice CT 20052005 – – Single-SourceSingle-Source
Dual-Energy MDCTDual-Energy MDCT
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3
KV
Intensity
Pre-patient Beam filtration
Low-Energy X-ray radiation
High-Energy X-ray radiation
Spectrum Decomposition Principle: Spectrum Decomposition Principle: Photons in the x ray beam of the CT scanner have
different energies
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X-Rays
SCINT2
SCINT1E1
E2
64 detectors
PHILIPS Brilliance CT Prototype
32 detectors for low energy
32 detectors for high energy
Dual-Energy CTDual-Energy CT
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low energy imagelow energy image
high energy imagehigh energy image
combined imagecombined image
Each scan creates 3 types of images:Each scan creates 3 types of images:
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Every pixel has 2 HU values – for high & low energyEvery pixel has 2 HU values – for high & low energy
-986/1003-986/1003
+23/+35+23/+35
+197/236+197/236
-106/-135-106/-135
+191/215+191/215+329/389+329/389
+119/147+119/147
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Dual-Energy CT main advantages:
Separation
Contrast
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A separation line can be calculated
each material has a different separation lineeach material has a different separation line
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Materials Separation
1. Iodine
2, Oil
3. 20% oil
5. Calcium4. Barium
6. Gadolinium
7. Cis Platinum
8. Water1. IodineAvg: 319
2, OilAvg: -102
3. 20% oilAvg: -16
5. CalciumAvg 306 4. Barium
Avg 4886. Gadoliniu
m Avg 3627. Cis Platinum
Avg 26.6
8. WaterAvg 1.3
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Dual-Energy CT main advantages:
Separation
Contrast
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CT density of tissues is the result of interactions between x-ray photons and tissues:
Compton scattering Photoelectric effect
Dual-Energy Imaging
At Low Voltage: At Low Voltage:
Photoelectric effectPhotoelectric effect is increased is increased
Compton scatteringCompton scattering is decreased is decreased
ContrastContrast is improved is improved
higher attenuation readings of iodine are obtainedhigher attenuation readings of iodine are obtained
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Purpose
To quantitatively and qualitatively evaluate
lesion conspicuity & Contrast to Noise ratio
of abdominal lesions with DECT.
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Materials and Methods
A prospective study (9 / 2006 – 2 / 2008)
Each patient signed an informed consent All studies were clinically indicated Study population: 23 patients Average age 58 years (range 36-86)
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Materials and Methods
CT parameters 2-3mm slice thickness 1-1.5 mm increment 140 kVp 250-300 mAs 100 cc of nonionic contrast 1.5-2 cc/sec
Regions-of-interest (ROI) were drawn on the lesion evaluated and the adjacent organ
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Contrast-to-Noise Ratio
CNR was defined as the difference
in attenuation between the lesion
and the organ, divided by the air
SD for both the low-energy and
regular CT images (for fixed ROI)
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HU lesion – HU organ
SD airCNR =
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Lesion Contrast Qualitative Assessment
Low energy and regular CT images were visually compared using the same window
Lesion conspicuity was graded on a predetermined scale No difference = 0 Significant change = 3
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Results
37 lesions 27 solid 10 cystic
Organs 14 kidney 12 liver 5 ovary 4 lymph nodes 2 fluid collections
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Results
Improved CNR was noted for both lesion types
Solid lesion CNR 2.11 (SD=0.4) with low energy 1.76 (SD=0.26) for regular CT (p<0.01)
Cystic lesion CNR 8.24 (SD=0.64) with low energy
7.58 (SD=0.46) for regular CT (p<0.03)
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Results
On visual inspection
Low energy 2.1 for conspicuity & lesion-to-organ contrast, solid lesions
2.4 for cystic lesions
Regular CT 1.8 for conspicuity & lesion-to-organ contrast, solid lesions
2.05 for cystic lesions
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Results
Combined Low Energy
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Results
Combined Low Energy
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So, If better lesion conspicuity
Why not scan with low kV all the time?
Noisy image, Data may be lost!
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Conclusions
Improved conspicuity of solid and cystic abdominal and pelvic lesions on low energy images obtained using single-source dual-energy MDCT
May enable earlier detection of small lesions and improved diagnosis of neoplastic processes
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Work in Progress
Digital Subtraction (electronic cleansing) of tagged stool in computed tomographic
colonography based on the Dual energy imaging separation capabilities
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Our CTC Study:
Aim: To compare prep- less dual energy CTC with OC for evaluation of colorectal polyps
Hypothesis: Dual Energy prep- less CTC can: reliably detect polyps ≥ 10 mm Superior digital cleansing
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Electronic cleansingwith dual-energy analysis
Electronic cleansingwith high and low HU thresholds only
The colon is partially filled with stool and both Iodine contrastand Barium contrast
Electronic cleansing: dual-energy analysis vs. HU thresholdsIntake of both Iodine and Barium
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Study design:
100 high risk patients Will be referred by gastroenterologists to
research fellow for preparation guidelines CTC will be performed and analyzed 3 wks later, OC with video taping will be
performed with segmental unblinding as a gold standard