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Apr 04, 2018

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Virtual Colonoscopyin colorectal cancer screening

    Francis Alenghat, Harvard Medical School Year III

    Gillian Lieberman, MD

    Date of RotationNovember 2003

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Patient AA

    78 year-old female Iron-deficiency anemia

    Scheduled for upper GI endoscopy andcolonoscopy but cancelled due toapprehension

    Episodic rectal bleeding Agreed to undergo virtual colonoscopy

    with conventional colonoscopy follow-up

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    Francis Alenghat, HMS III

    Gillian 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

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Colorectal Cancer

    2nd most common cause of cancer-related death in

    US

    everyone > 50 years should be screened

    only

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    Francis Alenghat, HMS III

    Gillian 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 screeningwith high sensitivity and specificity

    Stool-based molecular screening

    Virtual colonoscopy

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep

    2. Air insufflation of colon

    3. Ensure full length insufflation with scout CT

    4. Supine uninterrupted volume of data throughabdomen 32 second breath hold.

    Thin slices ~ 1-2.5 mm.

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

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Scout CT

    After air insufflation After a little more airCourtesy Dr. Morrin

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep

    2. Air insufflation of colon

    3. Ensure full length insufflation with scout CT

    4. Supine uninterrupted volume of data throughabdomen 32 second breath hold.

    Thin slices ~ 1-2.5 mm.

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

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Axial CT

    Polyp

    Cecum

    Sigmoid

    Colon

    Courtesy Dr. Morrin

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Axial CT

    Polyp

    Ascending

    Colon

    Transverse

    Colon

    Descending

    Colon

    Courtesy Dr. Morrin

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Virtual Colonoscopy Basic Technique

    1. Bowel prep

    2. Air insufflation of colon

    3. Ensure full length insufflation with scout CT

    4. Supine uninterrupted volume of data throughabdomen 32 second breath hold.

    Thin slices ~ 1-2.5 mm.

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

    F i Al h t HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    3D reconstruction

    Polyp

    Frontal cutaway

    Air-soft tissue

    interface surface

    rendering

    Courtesy Dr. Morrin

    F i Al h t HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Endoluminal Perspective

    Polyp

    Haustra

    Courtesy Dr. Morrin

    F i Al h t HMS III

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    Francis Alenghat, HMS III

    Gillian 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)

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Follow-up on same-day

    Optical Colonoscopy

    Courtesy Dr. Morrin

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    A less subtle diagnosis...

    Courtesy Dr. Morrin

    3.6 cm polyp

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    A less subtle diagnosis...

    Courtesy Dr. Morrin

    Multiple adenomas

    - familial adenomatouspolyposis

    3.6 cm polyp

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian 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 thanconventional colonoscopy)

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

    Still requires bowel prep

    Not therapeutic

    Ionizing Radiation

    Cost

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian Lieberman, MD

    Screening in High Risk Patients

    Clearly established as an effective alternative when compared toconventional colonoscopy:

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

    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

    Francis Alenghat HMS III

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    Francis Alenghat, HMS III

    Gillian 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:

    Francis Alenghat, HMS III

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    Francis Alenghat, HMS III

    Gillian 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

    Francis Alenghat, HMS III

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    Francis Alenghat, HMS III

    Gillian 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:

    Francis Alenghat, HMS III

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    g ,

    Gillian Lieberman, MD

    IV Contrast for Increased Sensitivity

    IV contrast

    Courtesy Dr. Morrin

    Submerged polyp

    seen with contraston prone scan.

    Francis Alenghat, HMS III

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    g ,

    Gillian Lieberman, MD

    Screening in Average Risk Patients

    1233 patients in prospective multicenter trial withsame-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 endoscopyPickhardt et al 2003 (NEJ M in press)as reported at 4th Intern. Symp. on VC

    Francis Alenghat, HMS III

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    g

    Gillian Lieberman, MD

    Modifications and Frontiers

    IV contrast

    Fecal tagging

    MRI virtual colonoscopy

    Computer aided detection

    Prepless or minimal prep procedures

    Francis Alenghat, HMS III

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    Gillian 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 ClinNorth 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 Med1999; 341: 1496-1503.

    Ferrucci JT. Virtual Colonoscopy for Colon Cancer Screening: Further reflections on

    polyps and politics.Am J Roentgenology2003; 181: 795-7.

    Karlson B-M, Ekbom A, Lindgren PG, Kallskog V, Rastad J. Abdominal US for

    diagnosis of pancreatic tumor: prospective cohort analysis. Radiology1999; 213: 107-

    11.

    Morrin MM, Raptopoulos V. Contrast-Enhanced CT Colonography. Semin Ultrasound

    CT MR2001; 22: 420-424.

    Ransohoff DF, Sandler RS. Screening for Colorectal Cancer. N Engl J Med2002; 346:

    40-44.

    Rosewicz S, Wiedenmann B. Pancreatic carcinoma. Lancet1997; 349: 483-89.

    Walsh JME, Terdiman JP. Colorectal Cancer Screening. JAMA 2003; 289: 1288-1302.

    Francis Alenghat, HMS III

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    Gillian Lieberman, MD

    Acknowledgements

    Thank you!! Martina Morrin, MD

    Larry Barbaras

    Gillian Lieberman, MD

    Pamela Lepkowski