Pitfalls in abdominal diffusion-weighted imaging: how predictive is restricted water diffusion for malignancy.
OBJECTIVE
As diffusion-weighted imaging is increasingly implemented into routine protocols of abdominal MRI, abnormal findings in expected and unexpected locations become more common. The aim of our retrospective study was to investigate the specificity of restricted diffusion in differentiation of benign from malignant abdominal disease.


METHODS
Two hundred thirty consecutively registered patients underwent abdominal MRI including diffusion-weighted imaging (single-shot spin-echo echo-planar sequence) with b values of 0, 150, 500, and 1,000 s/mm(2). Lesions were detected by two blinded readers using only the images with a b value of 1,000 s/mm(2), and representative apparent diffusion coefficients were measured. Lymph nodes were not documented.


RESULTS
Fifty-two of the 230 patients had a total of 55 lesions with restricted diffusion (23.9%). The mean apparent diffusion coefficient was 809 mm(2)/s. Forty-three lesions (78.2%) were malignant. The 12 benign lesions were liver hemangioma, liver adenoma, autoimmune pancreatitis, pancreatic teratoma, two abscesses, three cases of inflammatory bowel wall thickening due to Crohn's disease, Bartholin cyst, hemorrhagic ovarian cyst, and renal Rosai-Dorfman disease.


CONCLUSIONS
Restricted diffusion is generally considered to be associated with malignant tumors because of the high cellularity of these tumors. However, in interpretation of diffusion-weighted images, it should be kept in mind that a number of benign lesions, as many as 22% in our cohort, can exhibit restricted diffusion on images with high b values, thus mimicking malignant lesions.
Feuerlein
Sebastian
S
Department of Diagnostic and Interventional Radiology, University of Ulm, Steinhoevelstrasse 9, 89075 Ulm, Germany. sfeuerlein@yahoo.com
Pauls
Sandra
S
Juchems
Markus S
MS
Stuber
Tina
T
Hoffmann
Martin H K
MH
Brambs
Hans-Juergen
HJ
Ernst
Andrea S
AS
D000008:Abdominal Neoplasms / Q000175:diagnosis*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001834:Body Water / Q000378:metabolism; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult