Extended Data Fig. 3: Images of a representative patient.

Enrollment Images: a) Axial MRI T1 fat-saturated image post contrast shows an enhancing right retropharyngeal mass with white line indicating maximum transverse diameter. b) Axial ¹²³I-MIBG SPECT CT fused image shows marked MIGB uptake in the mass (white arrow). Imaging six months after the initiation of therapy: c) Axial MRI T1 fat-saturated image post contrast shows an enhancing right retropharyngeal mass with white line indicating no significant change in maximum transverse diameter consistent with stable disease by RECIST 1.1 criteria. d) Axial ¹²³I-MIBG SPECT CT fused image shows resolution of MIBG uptake in the mass (white arrow). Normal salivary gland uptake of ¹²³I-MIBG bilaterally is seen.