Applications of Low KeV Imaging in Abdomen

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1 Applications of Low KeV Imaging in Abdomen Dushyant Sahani, M.D Director of CT Associate Professor of Radiology Massachusetts General Hospital Harvard Medical School

2 Disclosure Research Grant Support GE Healthcare BD Consultant, Bracco Diagnostics

3 Low kv imaging: Exploiting the k-edge of Iodine Indication 140 kv 100 kv Stiller W. Eur J Radiol Perisinakis K. Br J Radiol Utsunomiya D. Eur Radiol Marin D. Radiology Marin D. Radiology Kim JE, AJR Hunsaker AR. AJR Godoy MC. Eur J Radiol Feuchtner GM. Eur J Radiol Sahani DV. AJR 2007 Kalva S. J Comput Assist Tomogr. 2006

4 Photon energy Challenges with Single Energy CT Tissue characterization Lesion detection (small lesion) Image noise and quality at low kv scanning Complex scanning protocols (multi-phase imaging) Radiation Dose kvp define upper limit for Polychromatic X ray kv 140 kv spectrum

5 FEATURES DS DECT SS DECT X Ray tube Two Tube mounted at 90 degrees Single X-ray tube & Gemstone detector with fast processing speed Tube potential Two Tube A (140kV, 50cm FOV) & Tube B (80/100kV, only 33cm FOV). Single X-ray tube with 50cm FOV capable of ultrafast kv switching between 80 and 140kV. ma ma on each tube can be controlled ma is fixed for both 80 and 140kV acquisition cycle. Reconstruction technique Post processing of data Image space based Three material decomposition Soft tissue, fat, Iodine Iodine map and virtual non contrast DE data (80/100kV kv) water, uric acid, calcium Stone analysis Monochromatic Images ( kev) Contrast exploitation from Lower kev images Projection space based Monochromatic Images ( kev) Contrast exploitation from Lower kev images DE data (80kV + 140kV) Material density images from two material decomposition Allows separation of different material/tissue Effective Z image Distinguishing tissues based on effective atomic number

6 Flux Polychromatic vs Monochromatic images 70 kev MONOchromatic Xray beam 70 kev Polychromatic Xray beam 80 kvp 140 kvp Energ y kvp kev specifies defines the the upper photon limit energy x-ray for a polychromatic monochromatic Xray x-ray beam source 80 kvp 140 kvp kvp ~ KeV

7 cm 2 /g Monochromatic Image Generation Water (mg/ml) Iodine (mg/ml) p ( E) d ( E) d Monochromatic iodine E 70 kev (HU) water kev

8 Virtual Monochromatic Imaging 80 kvp 140 kvp 70 KeV 100 KeV Matsumoto K. Radiology 2011

9 Low kev: Image Quality 70keV Image 120kVp Image

10 V-keV: Enhancements 120 kvp kev 70keV kev

11 Low kev: Improved Detection 140 kv 70 kev 50 kev 50keV Mono MD Iodine

12 Low kev: Improved Detection Indication Liver perfusion abnormality 70 kev 50 kev MD Iodine Differential enhancement better seen on MD Iodine image CT Enterography MD Iodine and lower kev MC images accentuates bowel wall enhancement

13 Improved Enhancement Hematuria Renal donor RCC 70 kev 50 kev

14 Low KeV images : Renal Trauma 50 kev 70 kev Catheter angio

15 Indication Better Endoleak detection on lower kev images (CTA study done with only 40ml IV contrast) MC 70 kev Vascular Imaging MC 60 kev MC 50 kev 120 kv Arterial MC 50 kev Better Endoleak detection on lower kev images On delayed phase acquisition, 50 kev MC image provide enhancement and attenuation values similar to arterial phase 120 kv Arterial MC 70 kev 1 min delay MC 50 kev 1 min dela HU HU HU - 287

16 Low kev: Improved Contrast Enhancement- 40 ml CM MC 70 kev Iodine(Water) Status of Stent Patency - I/W images were of added benefit in increasing confidence level for commenting on stent patency

17 Summary From the DECT data virtual monochromatic images of a desired kev can be processed Improved detection of iodine-containing substances on low Kev images. 50 kev for vascular imaging 70 kev for solid viscera These capabilities are promising for improved detection and characterization Evaluation of vascular structures. Reduce iodinated contrast material dose Further research is needed to validate the accuracy of some of these techniques