DTI assessment of the brainstem white matter tracts in pediatric BSG before and after therapy: a report from the Pediatric Brain Tumor Consortium.
OBJECTIVE
To assess changes in apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values in brainstem gliomas (BSG) in children and to observe the temporal evolution of changes in the white matter tracts following therapy using diffusion tensor imaging (DTI) analysis.


METHODS
Serial ADC and FA measurements were obtained in three patients with newly diagnosed BSG on two approved treatment protocols. Values were compared with a set of normative ADC, FA, and eigenvalues of age-matched children of the corticospinal, transverse pontine and medial lemniscal tracts. Fiber tracking of the tracts coursing through the brainstem was performed using standard diffusion tractography analysis.


RESULTS
We found increased ADC values within tumor at baseline compared to age-matched controls, with subsequent drop following treatment and subsequent increase with recurrence. Correspondingly, FA values were reduced at presentation, but transiently recovered during the phase of tumor response to treatment, and finally decreased significantly during tumor progression. These changes were concordant with the tractography analysis of white matter tracts in the brainstem. Based on these results, we suggest that initial changes in ADC and FA values reflects tract infiltration by tumor, but not complete disruption, whereas tumor progression results in complete loss of anisotropy possibly due to tract disruption.


CONCLUSIONS
Serial changes in ADC and FA values and tractography data in pediatric BSG suggest initial tumor infiltration, with transient improvement on treatment and subsequent loss of tract anisotropy during tumor progression. This technique may have potential use in assessing response to treatment regimens for pediatric BSG.
Department of Radiology, Harvard Medical School, Children's Hospital Boston, 300 Longwood Ave., Boston, MA 02115, USA. sanjay.prabhu@childrens.harvard.edu
Sanjay P
SP
Prabhu
Sarah
S
Ng
Sridhar
S
Vajapeyam
Mark W
MW
Kieran
Ian F
IF
Pollack
Russell
R
Geyer
Daphne
D
Haas-Kogan
James M
JM
Boyett
Larry
L
Kun
Tina Young
TY
Poussaint
D000293:Adolescent; D016880:Anisotropy; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001933:Brain Stem / Q000473:pathology*; D020295:Brain Stem Neoplasms / Q000473:pathology* / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D017322:Clinical Trials, Phase II as Topic; D003131:Combined Modality Therapy; D056324:Diffusion Tensor Imaging; D000077156:Gefitinib; D005910:Glioma / Q000473:pathology* / Q000628:therapy; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D011799:Quinazolines / Q000627:therapeutic use; D015363:Quinolones / Q000627:therapeutic use; D011878:Radiotherapy
D000970:Antineoplastic Agents; D011799:Quinazolines; D015363:Quinolones; C402769:tipifarnib; D000077156:Gefitinib