Case report: Exploring chemoradiotherapy-induced leukoencephalopathy with 7T imaging and quantitative susceptibility mapping

Abstract

Chemotherapy and radiotherapy are widely used in the treatment of central nervous system tumors and acute lymphocytic leukemia even in the pediatric population. However, such treatments run the risk of a broad spectrum of cognitive and neurological deficits. Even though the correlation with cognitive decline is still not clear, neuroradiological defects linked to white matter injury and vasculopathies may be identified. Thanks to the use of 7T MRI it is possible to better define the vascular pattern of the brain lesions with the added advantage of identifying their characteristics and anatomical localization, which, however, are not evident with a conventional brain scan. Moreover, the use of Quantitative Susceptibility Mapping (QSM) makes it possible to discriminate between calcium deposits on vessels (chemo-radiation-induced) and hemoglobin deposition in radio-induced cavernomas, speculating, as a result, about the pathophysiology of iatrogenic brain damage. We describe the case of a 9 year-old boy with a T-type acute lymphoid leukemia who had previously been treated with polychemotherapy and high-dose RT. To better define the child's neuroradiological pattern, 7T MRI and QSM were performed in addition to conventional imaging examinations. Our case report suggests the potential usefulness of a QSM study to distinguish radio-induced vascular malformations from mineralizing microangiopathy.

Keywords: 7 Tesla; brain damage; chemoradiotherapy; leukoencephalopathy; neurotoxicity; ultra-high field MRI.

Figure 1

Magnetic susceptibility dependent axial images acquired at 1.5T and 7T and Quantitative Susceptibility (χ) Mapping analysis. While in the 1.5T images the foci of deposition (hypointense in all sequences) appear to be located at the cortico medullary junction, it is worth noting that in 7T images they appeared located in intracortical area as confirmed in images detail (panel on the right).

Figure 2

Magnetic susceptibility dependent sequence Quantitative Susceptibility (χ) Mapping (QSM) at 1.5T and 7T. Several focal hypointense formations are visible at the cortico-medullary junction in the two cerebral hemispheres (white circles), more numerous and evident in 7T images. Some of them (red circles) are hyperintense in the QSM images in in relation to the presence of material with high magnetic susceptibility, thus probably referring to radio-induced cryptic vascular malformations (cavernomas, capillary telangiectasias). Others (blue circles) remain hypointense in QSM images due to the prevailing presence of diamagnetic material, thus probably referring to parenchymal calcifications as a complication of multimodal chemo-radiotherapy treatment.