Amide Proton Transfer weighted imaging reveals a rolandic tumor in a pediatric patient

Introduction

Discovery of a right parietal lesion in a five-year-old child with local meningeal extension following a convulsive seizure.

Medical history

The young patient presented a first hyperthermic convulsive seizure. One month later, he presented another tonic-clonic episode with left hemicorporeal seizure lasting less than 5 minutes. Another month later, he had a tonic-clonic seizure again, without fever but complicated by status epilepticus. Afterwards, a CT scan showed a right parietal lesion, and he was transferred to the Necker- Enfants Malades hospital for a brain and spinal-cord MRI. The spinal-cord MRI did not reveal any metastases.

A lesionectomy was performed. A postoperative remnant and a local meningeal infiltration were shown on brain MRI.

Anatomical pathology indicated a right parietal atypical teratoid rhabdoid tumor (ATRT), which is an embryonal tumor proliferation, INI1 deficient.

The young patient had a first course of chemotherapy with doxorubicin followed by radiotherapy (from 3 months to 4 months after surgery).

Image acquisition and analysis

Examinations were acquired on 3T MRI (GE Milwaukee, MR750W) at different timelines: pre-operative, post-operative (48 hours, 6 weeks and 10 weeks) after neurosurgery.

For each timeline, 3D gradient echo (GRE) T1-weighted, 3D fast spin echo (FSE) T2-weighted, 3D FSE FLAIR, Diffusion-weighted (12 directions), Susceptibility Weighted Imaging (SWI) and post-contrast 3D FSE T1-weighted sequences were acquired. Pseudo continuous arterial spin labelling (pCASL) sequences were performed to measure Cerebral Blood Flow (CBF) in post-operative MRI.

3D FSE Amide Proton Transfer weighted (APTw) sequence was performed in post-operative 6-week timeline in the framework of a clinical research study (see Additional Information).

Apparent Diffusion Coefficient (ADC) and CBF maps were computed by the scanner software, while Spillover-corrected APTw (S.C. APTw) maps were processed in Olea Sphere 3.0, to correct for movement, noise, field inhomogeneities and artefacts from fluid compartments.

Examinations were reviewed in consensus by two senior pediatric neuroradiologists.

Follow-up

6 weeks after the surgery. The MRI protocol showed persistence of leptomeningeal contrast enhancement. A contrast-enhanced lesion with no diffusion restriction and with a decreased CBF was observed in the right rolandic sulcus. FLAIR hypersignal was persistent in the operated area and at the rolandic level. However, at this rolandic level, the APTw map revealed a marked relative increase in signal intensity. Mobile proteins and peptides are the main contributors of APTw contrast, known to increase in neoplastic tissue. Therefore, S.C. APTw suspected a rolandic tumor, whereas ADC and CBF maps missed revealing such finding (Figure 1).