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CT colonography


									                                                                             Procedures of CTC

           CT colonography
    Technique & Interpretation                                                   Patient preparation

                                                                                   Colonic distention
              Seung Soo Lee, MD
                                                                                       CT scanning

   Department of Radiology and Research Institute of Radiology                        Interpretation
   University of Ulsan College of Medicine Asan Medical Center

                    Technique                                                 Bowel preparation
                                                                 Wet preparation
                                                                 ▶ PEG solution (colonlyte) 4L
                                                                     – Large residual fluid, intolerance

                                                                 Dry preparation
                                                                 ▶ Sodium phosphate (phosphosoda) 45mL or 90 mL
                                                                     – Electrolyte imbalance
                                                                 ▶ Magnesium citrate (Macrol) 250 mL
                                                                 Minimal prep or prepless
                                                                 ▶ Fecal tagging (±) Bisacodyl (Dulcorax)

                 Fecal tagging                                                     Fecal tagging
Can reduce cathartic bowel preparation                           Solid stool tagging                  Fluid tagging
Differentiation of residual feces from polyp

             Tagging agent

                   Ingested food

                      Tagged stool


            Fecal tagging agent                                                   AMC protocol
                                                              Standard prep protocol             Minimal prep protocol
▶ Tagitol V (E-Z-EM, Westbury, NY, USA)
    – 45% w/v barium 20 mL x 3                                 D-2
                                                               D-2    ••Low residue diet
                                                                         Low residue diet         D-2
                                                                                                  D-2      ••Low residue diet
                                                                                                              Low residue diet
▶ Easy CT 4.6 (Taejoon Pharmaceutical, Seoul, Korea )
                                                               D-1    ••아침 (미음)                   D-1
                                                                                                  D-1      ••아침 (미음)
    – 4.6% wv barium 200 mL x 3                                          아침 (미음)                              아침 (미음)
                                                                      ••12:00점심 (미음)
                                                                         12:00점심 (미음)                      ••12:00점심 (미음)
                                                                                                              12:00점심 (미음)
                                                                      ••18:00저녁 (미음)
                                                                         18:00저녁 (미음)                      ••18:00저녁 (미음)
                                                                                                              18:00저녁 (미음)
                                                                      ••19:00 Macrol 250cc                 ••21:00 Dulcorax 2T
▶ Diatrizoate meglumine and diatrizoate sodium 100 – 200 mL              19:00 Macrol 250cc                   21:00 Dulcorax 2T
                                                                      ••21:00 Dulcorax 2T
▶ Bowel cleansing effect                                                 21:00 Dulcorax 2T
                                                                                                  D0       ••Dulcorax 2T
                                                                                                             Dulcorax 2T
▶ More suitable for fluid tagging than barium                   D0
                                                                D0    ••물 이외 금식
                                                                        물 이외 금식                            ••물 이외 금식
                                                                                                             물 이외 금식

                                                                      = Easy CT 4.6 200 mL           = Gastrografin 30 mL

               Colonic distention                                            Colonic distention
                                                               Manual insufflation of room air
                                                               Automatic CO2 insuflation
                                                                ▶Pressure setting 25 mmHg
                                                                ▶Signs of full distention
                                                                                                                    Rectal pressure

                                                                     – Patients’ intolerance
                                                                     – Approximately 2L
                                                                     – Pressure consistently
                                                                       > 25 mmHg
         Poor distention
         Poor distention            Good distention
                                    Good distention                                                            Pressure control

               Colonic distention                                            Colonic distention
Procedure                                                       Automated CO2 insufflation: trouble shooting
                                                                ▶ Check the extension tube: blockage, compression, or
▶Left lateral decubitus position                                     kink
▶Pressure setting of 25 mmHg                                    ▶    Avoid occlusion of the tip against the rectal wall
                                                                ▶    Manual pulling of rectal tube
▶Turn to supine after insufflation of 1-1.5 L                   ▶    Knee and hip joints in a slightly flexed position
▶Scout view                                                     ▶    Gentle manual palpation of the abdomen to distribute
                                                                     the CO2
▶Continuous insufflation (15-25 mmHg) while                     ▶    Additional positional changes
   scanning                                                     ▶    Disconnect the tube for 3 seconds then reinitiate
                                                                ▶    Cushion under lower chest during prone position

                      CT scanning                                                                   AMC protocol
Supine & prone scanning                                                            Supine and prone scan
Thin slice (about 1 mm) image with overlap                                         16-MDCT (16 x 0.75 mm)
                                                                                   Beam pitch, 1
▶1.25 x 4 (4ch MDCT)/ 0.75 x 16 (16ch MDCT)
Low dose technique
                                                                                   Slice thickness, 1 mm/ interval, 0.7 mm
                        Male           Female                                      120 kVp and 30 mAseffe
  150 mAs x 120 kVp    8.1 x 2         10 x 2
  50 mAs x 120 kVp     2.6 x 2         3.4 x 2
                                                                                   No routine use of buscopan or IV contrast
  30 mAs x 120 kVp     1.6 x 2         2x2
                                                                                   IV contrast for diagnostic exams
  10 mAs x 140 kVp     0.9 x 2         1.2 x 2
    Barium enema                 5-7                                                ▶Supine (nonenhance)/ prone (72 sec delay)

                      Interpretation                                                       Interpretation: 2D vs. 3D

                                                                                           ≥ 5 mm   ≥ 6 mm   ≥ 7 mm   ≥ 8 mm   ≥ 9 mm   ≥ 10 mm

                                                                             Sensitivity    65%      78%      84%      87%      90%      90%

                                                                             Specificity    89%      88%      87%      87%      86%      86%

                                                                             PPV            45%      40%      35%      31%      25%      23%

                                                                             NPV            95%      98%      99%      99%      99%      99%

                                                                                            59%      70%      75%      80%      82%      84%

                                                                                   Performance: 2D = 3D, Reading time: 3D > 2D

                      Interpretation                                                                Polyp vs. Stool
Primary 2D (axial stack view)                       Primary 3D
                                                 (endoluminal fly-through)         Fecal tagging
                                                                                    ▶Practical & fundamental solution
                                                                                   In cases of untagged stool
                                                                                    ▶Internal attenuation
Primary 3D review                                                                   ▶Morphology
▶More intuitive, less reader-intensive

                Polyp vs. stool                                     Polyp vs. stool
Mobility                                               Mobility of stool


   F              P         3

       F                           P
            P                           F
           6                                                                      Macari, M. et al. Radiographics 2003;23:1073-1091

         Supine                        Prone

                Polyp vs. stool                                     Polyp vs. stool
Mobility of polyp                                      Mobility of colon itself

                                                                                                        AdenoCa in
                                                                                                         AdenoCa in
                                                                                                     villous adenoma
                                                                                                     villous adenoma

                                                       Mobility of colonic segments with long attached
                                                       mesocolon can mimick mobility of a suspected
                                                       lesion: cecum, transverse colon, and sigmoid colon.

                Polyp vs. stool                                     Polyp vs. stool
Internal attenuation                                   Stool: heterogeneous attenuation
   – Homogeneous attenuation
   – Heterogeneous attenuation in large lesions
   – Heterogeneous
   – Air-bubble/ingested high-attenuated material

           Polyp mimickers                                 Polyp mimickers
Bulbous & compound haustral fold: 2D > 3D   IC valve

                                                    Labial type                      Papillary type

           Polyp mimickers                                 Polyp mimickers
IC valve

                                                                  Diverticulum (3D)

              Lipomatous IC valve

                                                                   Air bubble (3D)

           Polyp mimickers                         Pitfalls in interpretation
Appendectomy stump (2D & 3D)                Flat lesions

      Pitfalls in interpretation                            Pitfalls in interpretation
Flat lesion                                          Distal rectum: lesion compressed by balloon

      Pitfalls in interpretation                         New 3D visualization tools
Distal rectum: internal hemorrhoid mimicking polyp

        New 3D review mode                                    New 3D review mode
Virtual dissection (GE)                              Filet view (Philips)

                                                                                                   Courtesy of
                                                                                                   Kim SH

        New 3D review mode                                New 3D review mode
Radial ray casting review mode (Lucion/Infinitt)   Panoramic view (GE)       Unfolded cube view

        New 3D review mode                                   Acknowledgement
Color coding of tagged stool (Siemens,             Seong Ho Park, MD, Department of Radiology
Lucion)                                            and Research Institute of Radiology University of
                                                   Ulsan College of Medicine Asan Medical Center,
                                                   for his providing materials for this presentation.

 Thank You for your


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