Patient 22.90 Y radioembolization of part of a segment III HCC via the terminal branch of the right internal mammary artery (RIMA). (a, b) Pre-therapy 99mTc MAA SPECT/CT demonstrates non-target activity in the right lower anterior chest wall (arrows), shunted from proximal branches of the RIMA. (c, d)90Y PET/CT depicts in high-resolution, non-target activity conforming to the anatomy of the right lower anterior chest wall, concordant with 99mTc MAA SPECT/CT. The slight dissimilarity in chest wall activity biodistribution between 90Y PET/CT versus 99mTc MAA SPECT/CT is due to local arterial flow changes after prophylactic bland embolization of proximal branches of the RIMA (images not shown). (e, f)90Y bremsstrahlung SPECT/CT was unable to detect any non-target activity in the chest wall due to its low image resolution.