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BACKGROUND
Diagnosis of osteomyelitis by imaging can be challenging. The
feasibility of diffusion-weighted imaging (DWI) as ancillary
sequence was evaluated in this study.
PURPOSE
To evaluate DWI for differentiation between osteomyelitis, bone
marrow edema, and healthy bone on forefoot magnetic resonance
imaging (MRI).
STUDY TYPE
Prospective.
SUBJECTS
A total of 60 consecutive patients undergoing forefoot MRI divided
into three study groups (20 subjects each): osteomyelitis, bone
marrow edema, and healthy bone.
FIELD STRENGTH/SEQUENCE
A 1.5T and 3T MRI scanners; readout-segmented multishot echo planar
DWI.
ASSESSMENT
Two independent radiologists measured apparent diffusion coefficient
(ADC) values within abnormal or healthy bone.
STATISTICAL TESTS
ADC values were compared between groups (pairwise t-test with
Bonferroni-Holm correction for multiple testing). Intraclass
correlation coefficient (ICC) was calculated to assess inter-reader
agreement. Threshold ADC values were determined as the cutoffs that
maximized the sum of sensitivity and specificity. Receiver operating
characteristic (ROC) analysis was performed with statistical
threshold of P < 0.05.
RESULTS
Inter-reader agreement was 0.92 in the healthy bone group and 0.78
in both the edema and osteomyelitis groups. Average ADC values were
significantly different between groups:
1432 ± 222 × 10 mm /sec
(osteomyelitis),
1071 ± 196 × 10 mm /sec
(bone marrow edema), and
277 ± 89 × 10 mm /sec
(healthy bone). A threshold ADC value of 534 × 10
mm /sec distinguishes between healthy and abnormal bone with
specificity and sensitivity of 100% each. For distinction between
osteomyelitis and bone marrow edema, two cutoff values were
determined: a 95%-specificity cutoff indicating osteomyelitis
(>1320 × 10 mm /sec) and a
95%-sensitivity cutoff indicating bone marrow edema
(<1155 × 10 mm /sec). Diagnostic accuracy
of 95% was achieved for 73% (29/40) of the subjects.
DATA CONCLUSION
DWI with ADC maps distinguishes between healthy and abnormal bone on
forefoot MRI. Calculated cutoff values allow confirmation or
exclusion of osteomyelitis in a high proportion of subjects.
EVIDENCE LEVEL
2 TECHNICAL EFFICACY: Stage 2.
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