Radiation effects in the rat spinal cord: evaluation with apparent diffusion coefficient versus T2 at serial MR...

Area of Science:

• Biomedical imaging
• Radiology
• Neuroscience

Background:

• Radiation therapy can cause spinal cord injury.
• Early detection of radiation-induced changes is crucial for managing side effects.
• Magnetic resonance (MR) imaging techniques like diffusion-weighted imaging and T2-weighted imaging are used to assess tissue changes.

Purpose of the Study:

• To compare the sensitivity of apparent diffusion coefficients (ADCs) and T2 relaxation times in detecting radiation-induced changes in the rat spinal cord.
• To investigate the spatiotemporal evolution of radiation-induced lesions in white matter (WM) and gray matter (GM).

Main Methods:

• Prospective study involving six rats irradiated with 36 Gy to the thoracolumbar spinal cord.
• Serial 7.0-T MR imaging (diffusion-weighted imaging and spin-echo sequences) performed for 3-6 months post-irradiation.
• Calculation of ADC and T2 values, semiautomated lesion detection, and comparison with histologic findings.
• Six age-matched rats served as controls.

Main Results:

• Radiation effects in WM initially appeared as lesions with low ADC and normal or high T2 values.
• High T2 in WM lesions correlated with confluent necrosis; normal T2 correlated with focal necrosis and demyelination.
• GM lesions showed diffusely high T2, attributed to edema.
• T2 changes in GM preceded both T2 and ADC changes in WM.

Conclusions:

• Longitudinal ADC is more sensitive than T2 for detecting radiation damage in the spinal cord white matter.
• T2 relaxation times are more sensitive for detecting radiation damage in the spinal cord gray matter.
• Differential sensitivity of ADC and T2 highlights their complementary roles in monitoring radiation-induced spinal cord injury.