Optimization of b value in diffusion-weighted MRI for the differential diagnosis of benign and malignant vertebral fractures.
OBJECTIVE
The objective was to explore the optimal b value in diffusion-weighted imaging (DWI) of MRI for differential diagnosis of benign and malignant vertebral fractures.


METHODS
Thirty-four consecutive patients with vertebral compression fractures underwent sagittal diffusion-weighted imaging (DWI) with different b values. The group included 14 patients with 18 benign vertebral fractures due to osteoporosis and/or trauma and 20 patients with 27 malignant vertebral fractures due to malignancy. The quality of the images was analyzed qualitatively on a three-point scale and quantitatively by measurement of the signal-to-noise ratio (SNR). Apparent diffusion coefficient (ADC) values were also calculated.


RESULTS
Smaller b values correlated with better DW image quality. We found significant differences in the qualitative points values among the DW images with different b values (F=302.18, p<0.001). The mean SNR of the images ranged from 21.75+/-3.64 at a b value of 0 s/mm2 to 5.31+/-3.17 at a b value of 800 s/mm2. The SNR of DWI with a b value of 300 s/mm2 (18.62+/-2.47) was significantly different from that with other b values (p<0.01). The mean combined ADC values of malignant fractures were significantly lower than those of benign ones on DWI with a b value of 300 s/mm2 (t=9.097, p<0.01). Four cases of benign vertebral fractures were misdiagnosed as being malignant when b values of 0 s/mm2 and 100 s/mm2 were used.


CONCLUSIONS
When DWI with multiple b values is used to differentiate benign from malignant vertebral compression fractures, b values within the range of around 300 s/mm2 are recommended, taking into account both SNR and diffusion weighting of water molecules.
Tang
Guangyu
G
Department of Radiology, Affiliated Tenth People's Hospital of Tongji University, Shanghai 200072, China. guangyutang@tom.com
Liu
Yong
Y
Li
Wei
W
Yao
Jiping
J
Li
Baoping
B
Li
Peng
P
D000328:Adult; D000368:Aged; D016477:Artifacts; D002277:Carcinoma / Q000556:secondary; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D050815:Fractures, Compression / Q000175:diagnosis* / Q000209:etiology; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications / Q000175:diagnosis; D011446:Prospective Studies; D016103:Spinal Fractures / Q000175:diagnosis* / Q000209:etiology; D013124:Spinal Injuries / Q000150:complications / Q000175:diagnosis; D013125:Spinal Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000556:secondary