Apparent diffusion coefficient in normal and abnormal pattern of intervertebral lumbar discs: initial experience

Abstract

The aim of the present study was to compare the relationship of morphologically defined non-bulging/herniated, bulging and herniated intervertebral lumbar discs with quantitative apparent diffusion coefficient (ADC). Thirty-two healthy volunteers and 28 patients with back pain or sciatica were examined by MRI. All intervertebral lumbar discs from L1 to S1 were classified according to morphological abnormality and degenerated grades. The ADC values of nucleus pulposus (NP) were measured and recorded. The significant differences about mean ADC values of NP were found between non-bulging/herniated discs and bulging discs as well as herniated discs (P < 0.05), whereas there were no significant differences in ADC values between bulging and herniated discs (P > 0.05). Moreover, statistically significant relationship was found in the mean ADC values of NP between "non-bulging/herniated and non-degenerated discs" and "non-bulging/herniated degenerated discs" as well as herniated discs (P < 0.05). Linear regression analysis between ADC value and disc level revealed an inverse correlation (r = -0.18). The ADC map of the NP is a potentially useful tool for the quantitative assessment of componential and molecular alterations accompanied with lumbar disc abnormalities.

Keywords: apparent diffusion coefficient; disc bulging; disc herniation; intervertebral lumbar disc.

Fig. 1. Different classifications of intervertebral disk.

The rows show the classification of abnormality and the columns show classification of disc degerceration.

Fig. 2. The elliptic ROIs with red dotted line were manually delineated in T₂-weighted image (T₂WI) at the center of lumbar disks to cover nucleus pulposus from L1 to L5.

The irregular ROIs for L5-S1 were selected by the operator according to the expected location of inner portion of lumbar disks. Then these ROIs in T₂WI were copied to the ADC maps, and ADC values measured. A: T₂WI. B: ADC map. C: ROI setting.

Fig. 3. Comparison of the corresponding disc percentages of the different groups among non-bulging/herniated, bulging, and herniated discs.

Fig.4. The bars for non-bulging/herniated, bulging and herniated discs represent the corresponding disc percentages of different disc levels.

Fig.5. Lumbar disc level correlated with the apparent diffusion csefficient (ADC) values of the nucleus pulposus.

ADC values for the nucleus pulposus region of all discs in each individual are illustrated. The solid line represents the regression line. r = -0.18, P = 0.002

Fig.6. Comparison of the mean apparent diffusion coefficient (ADC) values of the nucleus pulposus (NP) among non-bulging/herniated, bulging, and herniated discs.

The vertical bars represent the standard deviation from the mean with dark dots.*P < 0.05

Fig.7. Relationship between apparent diffusion coefficient (ADC) values of the nucleus pulposus (NP) and different categorizations.

The mean ADC value of NP in different lumbar disc categorizations is shown by clustered graph. The vertical bars represent the standard deviation, *P < 0.05.