Virtual Colonoscopy In Colorectal Cancer Screening

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  • Francis Alenghat, HMS IIIGillian Lieberman, MD

    Virtual Colonoscopy in colorectal cancer screening

    Francis Alenghat, Harvard Medical School Year IIIGillian Lieberman, MD

    Date of RotationNovember 2003

  • 2

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Patient AA

    78 year-old female Iron-deficiency anemia Scheduled for upper GI endoscopy and

    colonoscopy but cancelled due to apprehension

    Episodic rectal bleeding Agreed to undergo virtual colonoscopy

    with conventional colonoscopy follow-up

  • 3

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Occult or Lower GI Bleeding Occult:

    Upper GI bleed (varices, gums) Peptic Ulcers Angiodysplasia Benign Polyps Colorectal Cancer etc.

    Lower GI Bleed Colorectal Cancer Diverticula Ischemic Bowel Angiodysplasia Benign Polyps Hemorrhoids

  • 4

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Colorectal Cancer

    2nd most common cause of cancer-related death in US

    everyone > 50 years should be screened only

  • 5

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Screening Options Fecal occult blood testing 3 serial samples done at

    home and sent away for analysis Double contrast barium enema Sigmoidoscopy half the colon, misses 50% of

    neoplasms Colonoscopy currently gold standard for screening

    with high sensitivity and specificity

    Stool-based molecular screening Virtual colonoscopy

  • 6

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep2. Air insufflation of colon3. Ensure full length insufflation with scout CT4. Supine uninterrupted volume of data through

    abdomen 32 second breath hold. Thin slices ~ 1-2.5 mm.

    5. Postprocessing 3D reconstruction with surface, volume and/or perspective rendering

  • 7

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Scout CT

    After air insufflation After a little more airCourtesy Dr. Morrin

  • 8

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep2. Air insufflation of colon3. Ensure full length insufflation with scout CT4. Supine uninterrupted volume of data through

    abdomen 32 second breath hold. Thin slices ~ 1-2.5 mm.

    5. Postprocessing 3D reconstruction with surface, volume and/or perspective rendering

  • 9

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Axial CT

    Polyp

    Cecum

    SigmoidColon

    Courtesy Dr. Morrin

  • 10

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Axial CT

    Polyp

    Ascending Colon

    Transverse Colon

    Descending Colon

    Courtesy Dr. Morrin

  • 11

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep2. Air insufflation of colon3. Ensure full length insufflation with scout CT4. Supine uninterrupted volume of data through

    abdomen 32 second breath hold. Thin slices ~ 1-2.5 mm.

    5. Postprocessing 3D reconstruction with surface, volume and/or perspective rendering

  • 12

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    3D reconstruction

    Polyp

    Frontal cutaway

    Air-soft tissue interface surface

    rendering

    Courtesy Dr. Morrin

  • 13

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Endoluminal Perspective

    Polyp

    Haustra

    Courtesy Dr. Morrin

  • 14

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Endoluminal Navigation

    Courtesy Dr. Morrin

    1 2 3 4 5

    6 7 8 9 10

    Frames from fly-through sequence showing polyp (arrow)

  • 15

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Follow-up on same-day Optical Colonoscopy

    Courtesy Dr. Morrin

  • 16

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    A less subtle diagnosis...

    Courtesy Dr. Morrin

    3.6 cm polyp

  • 17

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    A less subtle diagnosis...

    Courtesy Dr. Morrin

    Multiple adenomas

    - familial adenomatous polyposis

    3.6 cm polyp

  • 18

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Virtual Colonoscopy pros and cons

    Visualization of entire colon Explore beyond colonic obstruction and both sides of haustral folds

    Reduced patient discomfort and anxiety Non-invasive Fast and does not require sedation

    Lower risk of procedural complications Sensitivity > 90% (in many studies even better than

    conventional colonoscopy)

    Specificity was low (until now), due to residual bowel fluid, fecal residue

    Still requires bowel prep Not therapeutic Ionizing Radiation Cost

  • 19

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Screening in High Risk Patients

    Clearly established as an effective alternative when compared to conventional colonoscopy:

    Sensitivity for polyps > 10 mm: 89-92% in studies with > 100 patients. (using same-day conventional colonoscopy as gold standard)

    Sensitivity for patients with polyps: 92-100%Specificity for patients with polyps: 72-97% but high prevalence of polyps in this population keeps PPV high

    Personal or family history of Colorectal Cancer

    Current symptoms

    iron-deficiency anemia

    heme positive stool

    hematochezia

    Prior occurrence of polyps

  • 20

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    False Positive Main culprits are residual fecal material and fluid due

    to incomplete bowel prep

    Scanning both supine and prone: exclusion of shifting material

    IV contrast: exclusion of non-enhancing material

    Fecal tagging: exclusion of enhancing material

    Techniques to reduce false positives:

  • 21

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    False Positive Main culprits are residual fecal material and fluid due

    to incomplete bowel prep

    Stool shift -

    not a polyp!

    Courtesy Dr. Morrin

    supine

    prone

  • 22

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    size, size, size 50% > 50yrs have polyps - so whats the screening

    threshold? > 1.0 cm polyps have majority of malignant potential detection of polyps 5-10 mm may be useful as

    clusters of small polyps also have increase potential sensitivity for these polyps in high risk cohorts: 70-82%

    flat adenomatous lesions also have malignant potential

    thinner slices: 1 - 3 mm IV contrast: enhance smaller lesions in background of

    residual fluid

    Techniques to increase sensitivity for small polyps:

  • 23

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    IV Contrast for Increased Sensitivity

    IV contrast

    Courtesy Dr. Morrin

    Submerged polyp seen with contrast on prone scan.

  • 24

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Screening in Average Risk Patients 1233 patients in prospective multicenter trial with

    same-day conventional colonoscopy as standard high risk patients excluded 24 hour bowel prep with phosphosoda, bisacodyl, barium,

    diatrizoate meglumine 1.25 - 2.5 mm collimation, supine and prone 3D endoluminal display read prior to conventional colonoscopy stool tagging and digital fluid subtraction

    Sensitivity by patient: 10mm -- 93.8% Specificity by patient: 10mm -- 96% Conventional colonoscopy sensitivity:

    87.5% (prior to unblinding)

    Conclusion: VC more sensitive than conventional colonoscopy, with high specificity: threshold of 8mm for f/u therapeutic endoscopy

    Pickhardt et al 2003 (NEJM in press) as reported at 4th Intern. Symp. on VC

  • 25

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Modifications and Frontiers

    IV contrast

    Fecal tagging

    MRI virtual colonoscopy

    Computer aided detection

    Prepless or minimal prep procedures

  • 26

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    References Barish MA, Soto J, Ferruci JT. Virtual Colonoscopy: Fourth International Symposium

    (Syllabus) Boston 2003. Dachman AH, Yoshida H. Virtual Colonoscopy: past, present, and future. Radiol Clin

    North Am 2003; 41: 377-93. Fenlon HM, Nunes MB, Schroy PC, Barish MA, Clarke PD, Ferrucci JT. A comparison

    of virtual and conventional colonoscopy for the detection of colorectal polyps. N Engl J Med 1999; 341: 1496-1503.

    Ferrucci JT. Virtual Colonoscopy for Colon Cancer Screening: Further reflections on polyps and politics. Am J Roentgenology 2003; 181: 795-7.

    Karlson B-M, Ekbom A, Lindgren PG, Kallskog V, Rastad J. Abdominal US for diagnosis of pancreatic tumor: prospective cohort analysis. Radiology 1999; 213: 107- 11.

    Morrin MM, Raptopoulos V. Contrast-Enhanced CT Colonography. Semin Ultrasound CT MR 2001; 22: 420-424.

    Ransohoff DF, Sandler RS. Screening for Colorectal Cancer. N Engl J Med 2002; 346: 40-44.

    Rosewicz S, Wiedenmann B. Pancreatic carcinoma. Lancet 1997; 349: 483-89. Walsh JME, Terdiman JP. Colorectal Cancer Screening. JAMA 2003; 289: 1288-1302.

  • 27

    Francis Alenghat, HMS IIIGillian Lieberman, MD

    Acknowledgements

    Thank you!! Martina Morrin, MD

    Larry Barbaras Gillian Lieberman, MD Pamela Lepkowski

    Virtual Colonoscopyin colorectal cancer screeningPatient AAOccult or Lower GI BleedingColorectal CancerScreening OptionsVirtual Colonoscopy Basic TechniqueScout CTVirtual Colonoscopy Basic TechniqueAxial CTAxial CTVirtual Colonoscopy Basic Technique3D reconstructionEndoluminal PerspectiveEndolumina

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