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AFIIM 2008 PARIS Potential Applications of Single Source Dual-Energy MDCT in the Diagnosis of Cancer Jacob Sosna, MD Department of Radiology Hadassah Hebrew University Medical Center, Jerusalem, Israel Harvard Medical School, Boston, MA • The radiological community in Israel has been involved in CT development since its early days • 1975 – Elscint CT founded • 1978 – 1st commercial scanner • 1979 - High resolution CT • 1992 – 1st spiral scanner (CT Twin) Beta sites in Israeli Radiology Departments Haifa Plant – CT History 2007 Br iCT 128 channels, 256 slices, 0.27s 2005 Br 64-Slice 2003 Br 40-slice 2001 1st 16-slice 0.42 sec CT 1998 1st 4-slice 0.5 sec CT 1995 World’s smallest whole-body CT 1995 Gated multiphase cardiac imaging 1994 Isotropic resolution 2x0.5mm 1992 1st spiral (dual slice) scanner (CT Twin) 1986 XRT DFS technology 1979 Highest resolution (13 lp/cm) 1978 1st Elscint CT (905 scanner) 1975 Elscint CT founded Cardiac CT Revolution Development of subsequent CT scanners was largely driven by the prerequisites for cardiac imaging: Faster scans Greater coverage Increased spatial and temporal resolution Cardiac CT scanners iCT iCT Br-64 IDT Dual Quad slice IDT slice 16 16 Br-40 Br-64 Br-40 MDCT WHAT IS MISSING? Are we really good at? • Separation between calcification and Iodine in CTA • Bone-removal in CTA (Cage Removal, Skull Removal etc.) • Soft plaque separation • Bone mineral & bone density assessment • Low contrast resolution (soft tissues) • Tracking drug delivery Are we really good at? • Early detection of cancer • Reliable measurements of tumors in a reproducible way • Still need for high dose of contrast in repetitive manner • Drug tracking • Tumor vascular studies- e.g. perfusion DUAL ENERGY Imaging CT But different elements can have same CT #…!! CT today …It’s all about Hounsfield units ( HU or CT# ) Spectrum Decomposition Principle Intensity Pre-patient Beam filtration Low-Energy X-ray radiation High-Energy X-ray radiation KV Dual-Energy Imaging • Dual-energy imaging takes advantage of differences in the degree to which body tissues attenuate low- and highenergy photons • These differences are used to generate tissue-selective images Dual Energy Imaging • Two types of dual-energy systems » Single-exposure system – Two detection systems one above the other » Dual-exposure system – Two sequential images are obtained at 2 energy levels with a subsecond delay between the two exposures – This can create misregistration artifacts due to slight offsets in the alignment of body structures caused by cardiac, respiratory, bowel, and patient motion Simultaneous Multi-Energy Detector (SMED) X-Rays Photons 100% ~50% SCINT1 SCINT2 Low Energy Raw data ~50% E1 image + High Energy Raw data E2 image ---------------------------------------- = Weighted combined Raw data CT image Combined Inner Outer Non-enhanced Combined Inner Outer Enhanced It’s All About the PIXEL -106/-135 -986/1003 +23/+35 +119/147 +197/236 +329/389 +191/215 Main Pathways The SC Benefits over conventional 64 MDCT • Separation • Contrast Main Pathways The SC Benefits over conventional 64 MDCT • Separation • Contrast Preliminary Phantom Tests 140 kV, 400 mAs Iodine Iodine Calcification pins of various concentrations and radii Calcium pins ~250 HU at 120 kV Saline 2D histogram separation Ca-I Differentiation – Calcified Aneurysm Iodine OR Calcium Images • Single click bone detection/ removal • Virtual angiography • Virtually cleansed bowel in CTC (iodine/ barium/fat) » Major benefit in CRC screening • Virtual Non enhanced CT Probabilistic Separation of Iodine: VNC Imaging Non-Binary Probabilistic Separation Defining a model that generate the noisy data (Instead of defining separation line) 500 E1 (HU) 3 x1 0 5 2.5 450 2 1.5 For each voxel build a Probabilistic Mixture Model over the neighbor in the E1-E2 plane and over the volume neighbor. 1 E1 400 0.5 0 0 20 40 60 80 350 10 0 12 0 14 0 16 0 18 0 20 0 300 For each voxel we can calculate the probability to be calcium and probability to be iodine. E2 (HU) 250 100 150 200 E2 250 300 350 400 Probabilistic Separation 550 500 450 400 350 300 250 200 150 100 0 The color intensity is proportional to the probability 100 200 300 400 500 Purpose To evaluate the ability to generate virtually non enhanced CT images from enhanced clinical CT studies and to compare image parameters to regular non-enhanced and contrast enhanced CT Materials and Methods • Spectral separation » Enhanced phase (C+) » Virtually non enhanced CT using a probabilistic mixture model (VNC) » Regular non-enhanced CT (C-) Materials and Methods • ROI of various organs and vessels including » » » » » Liver Spleen Aorta PV Muscle • 2 experienced radiologists in consensus assessed the visibility of calcified areas in the infra-renal aorta and artifacts Results • All 22 VNC studies could be obtained • Average change from C+ to VNC » Aorta -114.12 (SD 1.2) » RA -135.4 (SD 16) » PV -7.6 (SD 2.34) » IVC -1.73 (SD 1.99) Results • Average change from VNC to C» Aorta 38.03 (SD 0.6) » RA 37.8 (SD 2.8) » PV 21.8 (SD 1.93) » IVC 12.2 (SD 0.63) Results • Average change from C+ to VNC for solid tissues » Muscle 0.40HU (SD 0.19) » Liver 3.5HU (SD 1.15) » Spleen 9.2 (SD 3.15) Results • Average change from VNC to C- for solid tissues » Muscle 3.29HU (SD 0.53) » Liver 5.79HU (SD 0.28) » Spleen 22.2 (SD 1.72) Results • Total of 213 calcifications in C» 196 (92%) calcifications visualized in VNC • “Deleted” calcifications were mainly small areas 1-2 mm in size • Specific artifacts » Edge enhancement » Metallic clips diminished Scan without iodine With iodine Scan without iodine VNC Scan without iodine Scan with iodine Scan without iodine VNC Scan without iodine Scan with iodine Scan without iodine VNC Conclusions • Diagnostic virtually non-enhanced images can be obtained with single source dual energy CT • Iodine is “deleted” mainly from vessels and does not affect solid organs • Majority of calcifications are preserved • It may obviate the need for regular non-enhanced phase in multi-phasic MDCT especially for CTA studies Potential Applications in Oncology • No need for non –enhanced phase? • Better visualization of nodules • Benefit in adrenal imaging Electronic cleansing: dual-energy analysis vs. HU thresholds Intake of both Iodine and Barium The colon is partially filled with stool and both Iodine contrast and Barium contrast Electronic cleansing with dual-energy analysis Electronic cleansing with high and low HU thresholds only 1 Materials 1. Water 2. Calcium 0.35-0.04gr/ml diluted in water. 3. IntraLipid 20%-5% diluted in water. 4. Iodine (Meglumine Ioxitalamate ): 30 – 3mg/ml diluted in saline. 5. Gadolinium (gadoteric acid): 0.125-0.025mmole/ml diluted in saline 6. Cis-platinume 1mg/1ml (DOTAREM- Guerbet, France). 7. Barium Sulfate suspension 0.02-0.08gr/ml diluted in saline 8. soy bean oil (92%) 9. Bovine Liver 10. Chicken breast Results Calcium and Gadolinium are on the same separation line Barium and Iodine are on the same separation line We are not sensitive to lipids concentrations <20%(shall be further tested) Cis platinum not detected reliabley Further interest in drug detection with specific absorption patterns CT numbers 5. Calcium Avg 306 6. Gadolinium Avg 362 7. Cis Platinum Avg 26.6 4. Barium Avg 488 3. 20% oil Avg: -16 8. Water Avg 1.3 2, Oil Avg: -102 1. Iodine Avg: 319 Materials Separation 5. Calcium 4. Barium 6. Gadolinium 3. 20% oil 7. Cis Platinum 2, Oil 8. Water 1. Iodine Main Pathways The SC Benefits over conventional 64 MDCT • Separation • Contrast Attenuation of different materials 2 10 1 0.06 0.05 Attenuation 10 Iodine shows higher signal Iodine shows lower signal 0 10 Calcium Calcium K 0.04 -1 10 0.03 Iodine solution Iodine solution Tube 0.02 0.01 -2 0 10 0 20 20 40 40 60 60 80 80 100 100 120 120 140 kev reduction in tube voltage leads to an increase in attenuation of iodinated contrast material Iodine Augmentation in vivo • 18 patients 61 measurements (CTA) » Average increase of 33.4% in density in CTA • 30 patients 81 measurements (non CTA) » Average increase of 32.0% in density in cases CTA Results Regular Low Image energy 3 cc 228 320 5 cc 324 471 7 cc 483 720 28.5% contrast dose reduction Regular Low Low dose Regular Low Medium dose Regular Low Medium dose Regular High dose Low Human Applications • In adults 33% augmentation in density observed with low energy imaging • The difference may be explained by smaller size of rabbits (3.5 kg) • Expected similar change in density in low energy imaging in infants » Not performed yet due to IRB regulations Application in Oncology Patients • Significant iodine density augmentation can be obtained using the low energy layer versus the clinical image • A reduction in contrast volume may be feasible with similar densities at CT studies Contrast • Oncological imaging –Lesion conspicuity (liver, kidney, breast) –Improved CAD The Future in Oncology Imaging Abdominal CT DE Abdominal CT C- needed Not needed C+ needed Needed but with reduced contrast Drug tracking Not possible possible Lesion detection good improved 6 'מלכים ב' טז ". עַ ד ַהיֹום ַהזֶּ ה, ַוי ְֵׁשבּו ָּשם, בָּ אּו אֵ ילַ ת....." Hosting AFIIM Hotel Dan Eilat (on the Red Sea) 29-31 October 2008 Lectures and presentations in English