Theranostic Imaging of Yttrium-90

Figure 2

Imaging ⁹⁰Y bremsstrahlung and internal pair production following ⁹⁰Y microsphere RE therapy. This patient underwent intra-arterial administration of 1.74 GBq of ⁹⁰Y-labeled glass microspheres to the left hepatic lobe for the treatment of colorectal metastases. Post-RE therapy imaging included ⁹⁰Y bremsstrahlung planar and SPECT/CT imaging as well as ⁹⁰Y internal pair production PET/CT imaging. Bremsstrahlung planar and SPECT/CT imaging was obtained using the Symbia T16 system with medium-energy collimation (Siemens Healthcare). Bremsstrahlung photons were imaged using an energy window of 111–150 keV and were reconstructed using FLASH3D (8 iterations, 4 subsets). Internal pair production PET/CT imaging was obtained with the Gemini 64 Time-of-Flight system (Philips Healthcare). PET data were reconstructed using a 3D line-of-response TOF blob-based algorithm (3 iterations, 33 subsets). (a) Two-dimensional planar bremsstrahlung image of the abdomen (anterior view) which demonstrates intense bremsstrahlung activity corresponding to left hepatic lobe region as well as the presence of scattered photons in the field of view emanating from the treated left hepatic lobe. (b) Three-dimensional bremsstrahlung SPECT/CT image of the abdomen (fused SPECT/CT in the coronal plane) again demonstrates bremsstrahlung activity corresponding to the left hepatic lobe. Like the planar image, the fused SPECT/CT image demonstrates the presence of additional scattered photons and this additional scatter activity overlies several adjacent soft tissues and organs (e.g., heart, chest wall, right hepatic lobe, gallbladder, and bowel). (c) Three-dimensional internal pair production PET/CT image of the abdomen (fused PET/CT in the coronal plane) demonstrates ⁹⁰Y activity within the left hepatic lobe with more precise delineation of the ⁹⁰Y activity within the liver and greatly improved ⁹⁰Y-to-background contrast in the adjacent soft tissues and organs.

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