Pseudolesion of the Bile Duct Caused by Flow Effect: A Diagnostic Pitfall of MR Cholangiopancreatography
Reiji Sugita1,
Eriko Sugimura1,
Michiaki Itoh1,
Toshihiro Ohisa1,
Syouki Takahashi2 and
Naotaka Fujita3
1 Department of Radiology, Nippon Telephone and Telegraph East Tohoku Hospital,
2-29-1, Yamatomachi, Wakabayashi-ku, Sendai City, Miyagi Prefecture,
Japan.
2 Department of Radiology, Tohoku University School of Medicine, 1-1, Seiryocho,
Aoba-ku, Sendai City, Miyagi Prefecture, Japan.
3 Department of Gastroenterology, Sendai City Medical Center, 5-22-1, Turugaya,
Miyagino-ku, Sendai City, Miyagi Prefecture, Japan.
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Fig. 1A. —Drawings of phantom tubes used to represent biliary system in
experiments. In first model type, straight tubes with no change in diameter
were used throughout entire length of phantom. Straight tubes with 2-, 4-, 8-,
and 12-mm diameters were used, and decreased signal in arbitrarily selected
area was measured. D = diameter.
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Fig. 1B. —Drawings of phantom tubes used to represent biliary system in
experiments. Upstream inlet portion (I) of second model type was fitted with
various diameters of 2, 4, 8, and 12 mm to simulate bile duct sizes, ranging
from normal to dilated. Diameter of narrower outlet portion (O) was fixed at 2
mm, which was assumed to be diameter of papilla of Vater. Signal was measured
upstream (asterisk) from narrower outlet. Ratio between inlet and
outlet diameters was 1:1, 1:2, 1:4, and 1:6.
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Fig. 1C. —Drawings of phantom tubes used to represent biliary system in
experiments. Two tubes were used to simulate biliary system disease. Phantom
in C represents 50% stenosis; phantom in D represents bile duct
with stone. Difference between diameter of bile duct and bile stone was set at
50%. We used stone that had been obtained as surgical specimen. Signal
intensity (asterisks) was measured on both sides of
"diseased" portions of phantom. D = 10-mm diameter.
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Fig. 1D. —Drawings of phantom tubes used to represent biliary system in
experiments. Two tubes were used to simulate biliary system disease. Phantom
in C represents 50% stenosis; phantom in D represents bile duct
with stone. Difference between diameter of bile duct and bile stone was set at
50%. We used stone that had been obtained as surgical specimen. Signal
intensity (asterisks) was measured on both sides of
"diseased" portions of phantom. D = 10-mm diameter.
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Fig. 2. —Schema depicts flow in phantom model of bile duct. Steady
flow of water was initiated using autoinjector. Fluid flowed through phantom
into reservoir at flow velocity set between 1.0-20.0 mm/sec.
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Fig. 3. —Graph shows relationship between flow velocity and relative
signal ratio (between relative signal intensity in simulated bile duct and
that in control phantom). As flow rate increased, signal intensity in straight
tube phantom model showed diffuse decrease regardless of tube diameter and
reached plateau at approximately 5.0 mm/sec.
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Fig. 4. —Single-section MR cholangiopancreatogram of phantom shows
flow artifact—linear defect (short arrows)—parallel to
phantom wall. Ratio between inlet (single asterisks) and outlet
(double asterisks) diameters was 1:4. Signal intensity was measured
upstream (long arrows) from narrower outlet. C = solution of cupric
sulfate.
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Fig. 5. —Photograph of dye injection experiment. Ratio between inlet
(single asterisks) and outlet (double asterisks) diameters
was 1:4, and flow rate was 10 mm/sec. Linear flow head (short arrows)
was sharply pointed and ran parallel to wall of phantom. Signal in phantom was
measured upstream (long arrows) from narrower outlet.
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Fig. 6. —Coronal MR image (TR/effective TE, infinite, 90) of
73-year-old man with autoimmune-disease-related pancreatitis shows
pseudo-filling defect of common bile duct resulting from flow artifact. Linear
defect (arrows) is seen parallel to wall of bile duct.
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Fig. 7A. —Diagrams of shapes of flow artifact. Signal loss occurs
throughout whole bile duct in straight tubes (A, showing plug-shaped
flow, and B, showing laminar flow).
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Fig. 7B. —Diagrams of shapes of flow artifact. Signal loss occurs
throughout whole bile duct in straight tubes (A, showing plug-shaped
flow, and B, showing laminar flow).
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Fig. 7C. —Diagrams of shapes of flow artifact. When ratio between inlet
and outlet diameters was 1:4 or greater, flow head was extremely sharp, a
condition that can induce linear decrease in signal intensity parallel to bile
duct wall near outlet.
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Copyright © 2003 by the American Roentgen Ray Society.
