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CROHN DESEASE
New Imaging
BEN ROMDHANE MH
• role cross-sectional imaging expanded
• CT and MRI allow rapid acquisition of
high-resolution images of the intestines.
• Protocoles necessary to acquire images
of diagnostic quality
• Sensitivity (CT and MR I ) of over 95% for
the detection of CD
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Chronic granulomatous GI tract inflammation
peak between 15 and 25 years of age
tendency toward remission and relapse
affect any part of the GI tract
often multiple discontinuous sites
Small intestine 80% of cases,
terminal ileum most commonly
Colon affected with (50% of cases) or without
(15%–20%) involvement of the small intestine
• Earliest change in the submucosa with
lymphoid hyperplasia and lymphedema
• Early stage: subtle elevations and aphthoid
ulcers.
• Transmurally extension to serosa (transmural
stage) and
• Extension to mesentery and adjacent organs
(extramural stage).
• Aphthoid ulcers develop into linear ulcers and
fissures to produce an ulceronodular or
“cobblestone” appearance.
• bowel wall thickened by fibrosis and / or
inflammatory infiltrates
• common complications of advanced disease:
Bowel obstruction, strictures, abscesses or
phlegmon, fistulas, and sinus tracts
• not common, toxic megacolon and neoplasms
(lymphoma and carcinoma)
• Endoscopy and barium studies limited in
demonstrating the transmural or extramural
extent or extraintestinal complications
• Cross-sectional imaging may not detect subtle
mucosal lesions
• but reveals pathologic changes of the intestinal
mucosa
• help compensate for the limitations of
conventional imaging
• CT currently the cross-sectional imaging
modality of choice at most institutions
• MRI has also proved highly effective
• CT and MRI allow rapid acquisition of highresolution images of the intestines during a
breath-hold examination.
• CT and MRI provide useful information in the
diagnosis and in treatment planning
• limited spatial resolution of CT and MRI
compared with enteroclysis studies results in
lower rates of depiction of early disease
manifestations
• Detection and characterization of intestinal
lesions require appropriate preparation and
scanning techniques.
• GI tract should be empty and clean, with the
lumen distended
• review preparations, contrast agents, and
scanning techniques
• illustrate the characteristic imaging
appearances of CD
• Review findings that indicate the presence of
inflammatory lesion activity
• discuss advantages, limitations and role of
cross-sectional imaging
• Fast for 6 H prior examination (decreases
the alimentary residue
• Collapsed bowel loops may mimic a
segment with wall thickening, an abscess,
or enlarged lymph nodes
• Administration of large amount of
intraluminal contrast distends bowel
loops for better visualisation of anatomie
and morphologic changes
• IV contrast demonstrate the presence of
lesions and help assess their inflammatory
activity
Advantages of cross-sectional imaging
• demonstrate :
transmural extent of inflammation,
skip lesions beyond severe luminal stenoses,
intraperitoneal or extraintestinal complications
• provide three-dimensional information
• and, vascular information with use of contrast
material
Entéroscanner
• Ingestion soluté
hyperosmolaire/ Sonde
entéroclyse sous scopie
dans D3
• Antispasmodique IV
• Scanner sans et après
injection IV produit de
contraste
• The contrast agent should allow imaging with
- homogeneous luminal enhancement
-high contrast between lumen and bowel wall
-minimal mucosal absorption
- absence of artifact formation
- no significant adverse effects
• To minimize bowel movement or contraction
and motion artifact from intestinal peristalsis:
- Antiperistaltic agents prior to scanning
- short scanning time
• Intravenous contrast medium indicated for :
- better visualization of the bowel wall
extraintestinal structures, and lesions
- precise evaluation of the degree of
inflammatory activity
Computed Tomography
• Various types of intraluminal contrast media are
used to provide positive or negative contrast
between the bowel lumen and surrounding
structures
• Positive contrast agent with high attenuation at
CT aids in differentiating bowel loops from
enlarged lymph nodes or an extramural fluid
collection such as an abscess.
• The presence of small bowel obstruction or
fistulas is also well appreciated.
• with the use of positive intraluminal contrast
material, mural enhancement after iv injection
may obscure subtle Crohn lesions.
• The use of negative intraluminal contrast
agents with low attenuation facilitates depiction
of the wall of normal and diseased bowel
segments, particularly after iv contrast material
administration
• technique for intraluminal contrast material
administration is common to both CT and MRI
• Between 1,500 and 2,000 mL of contrast
material administered orally 45–90 minutes
prior to the examination
• To provide adequate and uniform distention of
the bowel loops, patients are asked to steadily
ingest the contrast material over a 20–60minutes period
• The contrast material may be administered
through a nasojejunal catheter at a rate of
100–250 mL/min with the help of a roller
pump
• CT or MR imaging performed with this
technique is called CT or MR enteroclysis
• Use of a nasojejunal catheter allows better
luminal distention but causes patient
discomfort
• If necessary, 300– 1,000 mL of contrast
agent can be administered transrectal
• CT scans with the patient in the prone
position is recommended to disperse the
small bowel loops
• With multi–detector row CT scanners,
thinner collimation (0.5–2.5 mm) is
possible. Sections with a 5–7-mm
thickness or thinner sections, overlapping
reconstructed images, or multiplanar
reformatted images
• IV administration of iodinated contrast
essential, 100–150 ml at a rate of 2.5–4ml
/sec with a delay time of 40–70 sec
MR Imaging
• Various kinds of intraluminal contrast agents
positive, negative, or biphasic
• Positive agents produce high intraluminal signal
• Negative agents produce little or no intraluminal
signal
• Biphasic contrast agents may produce either
high or low signal depending on the pulse
sequence used, usually demonstrating low
signal intensity on T1 and high signal on T2
• Negative or biphasic agents more suitable
• An antiperistaltic agent injected to
minimize potential artifact of bowel
movement or contraction
• Prone position recommended for
separating bowel loops and decreasing
the scanning volume. This position is also
safe for patients should they vomit
• To increase the signal-to-noise ratio, use of
abdominal phased array radiofrequency coils
• Coronal images obtained with a 4–7-mm
section thickness, a 128–256 256 matrix, and
a field of view of 350 mm or more
• Thicker sections to monitor the infusion
process ( 70–180 mm)
• Acquisition of axial, sagittal, or multiplanar
images may be necessary for precise
evaluation
• Protocol should include both T1- and T2- to
detect and characterize each lesion
• T1-weighted imaging with iv contrast essential
for assessing inflammatory lesion activity.
• True fast imaging with a steady precession
(FISP),
• half-Fourier acquired single shot fast spin-echo,
• T2-weighted turbo spin-echo,
• combination of these sequences recommended
Gadolinium enhanced fat-suppressed
spoiled gradient-echo T1 2D ou 3D
• excellent visualization of the enhancing bowel
wall ( contrasts with the low signal mesenteric
fat and negativ intraluminal contrast material)
• Morphologic features and degree of
enhancement both aid in assessing CD activity
• Images covering the bowel loops in their
entirety can be obtained within 30 sec
• Scanning is performed after a bolus iv injection
of 0.1–0.2 mmol/kg of gadopentetate
dimeglumine with a delay time of 40–80 sec
CT and MR Imaging Findings in CD
In proved or suspected CD
images analyzed specifically for :
- altered bowel segment(wall thickness,
attenuation , degree of enhancement, length of
involvement)
- stenosis and prestenotic dilatation
- skip lesions, fistulas, abscess, fibrofatty
proliferation, increased vascularity of the vasa
recta (comb sign), mesenteric adenopathy, and
other extra-intestinal disease involvement
• Normal thickness of the wall of the small
intestine1–2 mm and colon 3 mm when
lumen is distended
• Any portion of the bowel wall that exceeds 4–
5 mm is considered abnormal
• Bowel wall thickening, usually ranging from
1–2 cm, is the most consistent feature of CD
Paroi
• number of lesions and extent of Involvement
• involved segment homogeneous or stratified
appearance (alternating layers of higher or
lower attenuation or signal intensity) CT / MRI
• Mural stratification (“target” or “double halo”
appearance) often seen in active lesions
after iv contrast
• inflamed bowel wall demonstrates marked
enhancement after iv contrast
• intensity of enhancement correlates with
degree of inflammatory lesion activity
Activité
• normal small intestine lumen less
than 2.5 cm
• Luminal narrowing and associated
prestenotic dilatation easily recognized
• Deformity of bowel loops such as pseudodiverticulum formation caused by
asymmetric involvement by longitudinal
ulcers and ulcer scars is well demonstrated
on both axial and coronal images.
• early-stage lesions such as enlarged
lymph follicles, slight distortion of the
bowel folds, and tiny aphtae are not
consistently visible at either CT or MRI
due to inadequate spatial resolution
• Fibrofatty proliferation of the mesentery is
commonly seen adjacent to involved
bowel segment in CD
• CT and MRI demonstrate fibrofatty
proliferation,
• which has slightly increased CT
attenuation and
• slightly decreased MRI signal intensity
compared with normal fat separating the
bowel loops.
Signes extrapariétaux: graisse et
vaisseaux
• Abscess and phlegmon well demonstrated at
CT and fat-saturated T2-MRI
• can occur in small bowel mesentery abdominal
wall psoas muscle or around the anus
• Fistulas and sinus tracts are also depicted
• MRI sensitivity for depicting sinus tracts is
50%–75% /conventional enteroclysis
• Mesenteric lymphadenopathy ranging from 3
to 8 mm in size depicted at CT and MRI
• When lymph nodes larger than 10 mm,
lymphoma and carcinoma must be excluded.
Inflammatory activity
• well appreciated at CT and MR imaging
• Findings include :
thickened bowel wall
with marked contrast enhancement,
mural stratification,
pericolic or perienteric hypervascularity
(comb sign)
hyperintensity T 2 of the bowel wall
lymph node enlargement,
extramural complications: phlegmon abscess
• CT sensitivity 94%–100% specificity 95%
• Sensitivity increases to 98% in the
diagnosis of transmural or extramural
• only 70% for early-stage disease.
• multiplanar images with axial images
significantly improves observer confidence
• Sensitivity of MRI 96%–100%
• sensitivity on a per lesion 85 % and 100%
when superficial lesions excluded
• MRI role similar to that of CT with
High soft-tissue contrast
absence of ionizing radiation exposure
more time consuming,
less readily available,
more expensive
• Advantages of CT over MR imaging
greater availability, shorter examination
times, flexibility in choosing imaging
thickness and planes after acquisition
higher spatial resolution.
Conclusion
• Appropriate treatment planning in CD requires
correct assessment of the severity, extent, and
inflammatory activity of lesions and of the
presence of extraintestinal complications
• CT and MRI with intraluminal and intravenous
contrast material provide excellent visualization
of most intestinal lesions and demonstrate
mural and extramural extent, and complications
• Disease activity well appreciated( CT and MRI)
• Aid in selecting appropriate treatment options