Radiation-induced changes in MR signal intensity and contrast enhancement of lumbosacral vertebrae: do changes occur only inside the radiation therapy field?

PURPOSE

To evaluate temporal changes in signal intensity (SI) and degree of contrast enhancement (CE) of bone marrow in lumbosacral vertebrae inside and outside the radiation therapy (RT) field.

MATERIALS AND METHODS

Twenty-three patients with advanced uterine cervical cancer who were treated with RT were prospectively evaluated. Each patient underwent four dynamic magnetic resonance (MR) studies: before RT, 2 and 4 weeks after initiation of RT, and 4 weeks after completion of RT. SI and CE were calculated in all four studies of each patient.

RESULTS

Bone marrow inside the RT field showed steady and marked increase in precontrast SI and early and transient increase in CE at 2 weeks after initiation of RT followed by progressive and marked decrease in CE at 4 weeks after initiation of RT and 4 weeks after completion of RT. Bone marrow outside the RT field showed slight increase in precontrast SI and steady and moderate decrease in CE to a lesser degree without early increase as seen in bone marrow inside the RT field.

CONCLUSION

RT causes an increase in precontrast SI predominantly in bone marrow inside the RT field. However, a decrease in CE is seen in bone marrow not only inside but also outside the RT field.