Improved Conspicuity of Abdominal Lesions with Single-Source Dual-Energy MDCT Ruth Eliahou MD, Jacob Sosna, MD AFIIM 2008 Hadassah Hebrew University Medical Center Jerusalem, Israel
1972 – First single slice CT 2005 – Single-Source Dual-Energy MDCT
Spectrum Decomposition Principle: Photons in the x ray beam of the CT scanner have different energies Intensity Pre-patient Beam filtration Low-Energy X-ray radiation High-Energy X-ray radiation KV 3
Dual-Energy CT X-Rays E 1 SCINT 1 § 64 detectors § PHILIPS Brilliance CT Prototype § 32 detectors for low energy E 2 § 32 detectors for high energy SCINT 2
Each scan creates 3 types of images: combined image high energy image low energy image
Every pixel has 2 HU values – for high & low energy -106/-135 -986/1003 +23/+35 +119/147 +197/236 +329/389 +191/215
Dual-Energy CT main advantages: § Separation § Contrast
A separation line can be calculated each material has a different separation line
Materials Separation 5. Calcium 6. Gadolinium 4. Barium 6. Gadolinium Avg 362 3. 20% oil Cis Platinum 7. Avg 26. 6 7. Cis Platinum 2, Oil 8. Water 1. Iodine 5. Calcium Avg 306 4. Barium Avg 488 3. 20% oil Avg: -16 8. Water Avg 1. 3 1. Iodine Avg: 319 2, Oil Avg: -102
Dual-Energy CT main advantages: § Separation § Contrast
Dual-Energy Imaging CT density of tissues is the result of interactions between x-ray photons and tissues: §Compton scattering §Photoelectric effect At Low Voltage: Photoelectric effect is increased Compton scattering is decreased Contrast is improved higher attenuation readings of iodine are obtained
Purpose § To quantitatively and qualitatively evaluate lesion conspicuity & Contrast to Noise ratio of abdominal lesions with DECT.
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 58 years (range 36 -86)
Materials and Methods § CT parameters § § § 2 -3 mm slice thickness 1 -1. 5 mm increment 140 k. Vp 250 -300 m. As 100 cc of nonionic contrast 1. 5 -2 cc/sec § Regions-of-interest (ROI) were drawn on the lesion evaluated and the adjacent organ
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)
CNR = HU lesion – HU organ SD air
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
Results § 37 lesions § 27 solid § 10 cystic § Organs § § § 14 kidney 12 liver 5 ovary 4 lymph nodes 2 fluid collections
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)
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
Results Combined Low Energy
Results Combined Low Energy
So, If better lesion conspicuity Why not scan with low k. V all the time? Noisy image, Data may be lost!
Conclusions § Improved conspicuity of solid and cystic abdominal and pelvic lesions on low energy images obtained usingle-source dual-energy MDCT § May enable earlier detection of small lesions and improved diagnosis of neoplastic processes
Work in Progress Digital Subtraction (electronic cleansing) of tagged stool in computed tomographic colonography based on the Dual energy imaging separation capabilities
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
Study design: § 100 high risk patients § Will be referred by gastroenterologists to research fellow for preparation guidelines § CTC will be performed analyzed § 3 wks later, OC with video taping will be performed with segmental unblinding as a gold standard
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