CT Colonography: Image interpretation Beth G. McFarland, MD
Part III CTC Overview of different morphologic types:» Focal polyp vs stool» Sessile lesion and flat lesions» Pedunculated lesion» Cancer vs collapse or muscular hypertrophy
Part III CTC Clinical case reviews» Systematic/ efficient review - 3D + 2D» How to evaluate a focal lesion- TP vs FP» Reporting of cases (C-RADS)
Basic principles 3 3 steps to identify a focal lesion 1 2
To evaluate a focal finding 1. Shape» TP- smooth margins» FP- angular margins 2. Density (check 2D)» TP-soft tissue density, ** +/- linear coating with tagging» FP- high density or low density (fat, air) 3. Location (find on other view)- *most time consuming» coronal can be helpful for orientation» new software now gives more automated registration between supine and prone
Reading tips Bookmarking of lesions» Mark TP or FP with arrow as you go (won t redo later)» Take images and build report page / lesion» Allows easier dictation and concise report for referring MD
CASE 1 Screening case Very good image quality
Systematic review of case 3D as primary review:» Use 3D as primary detection» Use 2D MPR to further characterize» Density, location in colon 2D as primary review:» Use 2D as primary detection» Use 3D to further characterize» (eg) nodular fold or polyp on a fold
Systematic review of case: 3D as primary review - Quick coronal overview to assess image quality and anatomy - Three 3D fly-through paths: 1. Supine- retrograde from rectum to cecum 2. Supine- antegrade from cecum to rectum 3. Prone- retrograde from rectum to cecum - Quick axial 2D review to assess mural lesions (400/10 W/L)
CASE 2 Stool and fluid tagging
Tagging techniques Tagging with barium and/or iodine is widely being used: - Densely tags the stool to decrease FP - Coats the surface of polyps - Tags the fluid Lefere P, Radiology 2002;224:393-403
2019 ** Linear coating of polyps with tagging Tagging with barium and/or iodine is widely being used: - Densely tags the stool to decrease FP - Coats the surface of polyps - Tags the fluid OConnor et al, JCAT 2006:30:51-57
Partial coating of polyps with tagging Oral contrast does coat the surface of polyps» Thin linear surface coating» Adherent drops of contrast In 216 patients, 46% of 312 polyps had adherent contrast» Increased with villous histology O Connor, et al. JCAT 2006;30:51-57
2066 Tagging techniques supine Tagging with barium and/or iodine is widely being used: - Densely tags the stool to decrease FP - Coats the surface of polyps - Tags the fluid to increase sensitivity of submerged polyps prone
SAM #3 3. What is true about stool tagging? a) Densely coats residual stool to decrease false positives b) Can coat the surface of polyps, in a linear or globular fashion c) Can tag the fluid with high density to increase detection of submerged polyps d) Does not always coat stool e) All of the above
CASE 3 Superficially elevated lesion
Morphological types Polypoid» Pedunculated» Sessile Non-polypoid» Superficially elevated» Flat» Depressed
Superficial lesions Soetikno, JAMA 2008
Superficial lesions Soetikno, JAMA 2008 Courtesy of Andrea Laghi, Rome
CASE 4 Nonpolypoid, Depressed lesion
Superficial lesions Soetikno, JAMA 2008
SAM #4 4. What is true about sessile and flat lesions? a) Sessile and flat are terms incorrectly used as synonyms b) Sessile lesions are defined as polyps with height < ½ their length c) Nonpolypoid morphologies include superficial elevated, flat and depressed d) None of the above e) A, B and C above
CASE 5 Cancer + adenomatous polyp (post IV contrast)
SAM #5 5. What is most accurate about use of IV contrast in CTC? a) Most polyps enhance following administration of IV contrast b) The degree of enhancement can differentiate between benign and malignant polyps c) All cancers enhance with contrast d) Retained stool can have variable enhancement e) If a lesion enhances, it is highly specific for a colorectal neoplasm
Summary Develop consistent integrated 2D/3D evaluation» 3D fly-through in at least one view» All get 2D (400/10) for mural lesions (+ ECF) Develop consistent reporting structure (C-RADS)» Colorectal findings (C scores)» Extra-colonic findings (E scores)» Key images of lesions, along with 3D roadmap