Comparative Evaluation Of The Normal And Degenerative Lumbar Spine Disks With MR Apparent Diffusion Coefficients

PURPOSE: The spinal disks are rich in water and without blood supply, and the nutritional materials are sent to the disks by mean of diffusion. MR diffusion weighted imaging (DWI) is the method of reflecting the water diffusion status in human body. Apparent diffusion coefficient (ADC) is a quantitative parameter in detecting the water diffusion motion. The purpose of this study is to prospectively determine the diffusibility of water in normal lumbar disks in adults by using mean ADC and to determine the relationship between disk ADC and MR findings of degenerative disks.MATERIALS AND METHODS: DWI of the lumbar spine was performed in 20 patients (all man, age range 35-62 years, mean 48 years) and five volunteers (all man, age range 35-55 years, mean 45 years) from Oct 2004 to Jun 2005. 10 patients had unilateral or bilateral radiating pain of lower extremities, 4 with lower limb weakness, and 2 with traumatic history. None of 5 volunteers had any clinic symptoms. A 1.5 T MR scanner was used and sagittal TIWI, T2WI, and transverse T2WI parallel to the disk spaces were scanned. DWI was obtained in sagittal plane by using SE-EPI sequence. The disk changes on T2WI were independently assessed by two radiologists blind to diagnosis. The criteria included: (a) disks height, (b) disks signal intensity, (c) distinctness of the intranuclear cleft. The presence of any one abnormal changes of the 3 above-mentioned criteria indicated degenerative disk changes, while the others were determined as normal disks, thus, dividing the disks into two groups, i.e. degenerative group and normal group. ADC map was obtained by using Functool software, and ROIs were placed at L1-S1 disk levels and ADC values were measured. Correlation study was performed between normal ADC values and disk location, and the difference of ADC values between degenerative group andnormal group was compared.RESULTS: ADC values of the disks in the normal group decreased as theanatomic location descended, and ADC values of the degenerative disks decreasedmore prominently. The mean ADC value was (1.82±0.58)xl0~3mm2/sec in normalgroup and (1.64±0.47)xl0~~3mm2/sec in degenerative group (9% reductioncompared with that of normal group, P=0.006).CONCLUSION: ADC value decreases as the location descends in normal lumbarspinal disks. The degenerative disks on T2WI showed more evident ADCdropdown. As a quantitative study method, the measurement of ADC valueprovides us a more objective way in evaluating degenerative disk changes of thelumbar spine.