PET-Enabled Dual-Energy CT in Multiple Myeloma

This is a single-institution, prospective pilot study evaluating PET-enabled dual-energy CT (DECT) for quantitative bone marrow imaging. The study will enroll adults with multiple myeloma who are scheduled to receive CAR T-cell therapy and healthy adult participants for comparison. PET-enabled DECT is an imaging method that uses data from a standard time-of-flight PET/CT scan to generate a high-energy attenuation image. This image is combined with the standard X-ray CT image to create a dual-energy image pair. The goal is to measure tissue composition, including bone fraction and soft-tissue fraction, without requiring dedicated dual-energy PET/CT hardware. All participants will undergo research imaging with dynamic 18F-FDG PET/CT and X-ray DECT. Participants with multiple myeloma will undergo baseline imaging before CAR T-cell therapy and follow-up imaging after therapy. Healthy participants will undergo one imaging visit. Multiple myeloma participants will also have bone marrow measurable residual disease (MRD), treatment response, and CAR T-cell therapy toxicity data collected from standard clinical care or related clinical assessments. The primary objective is to develop and validate the new DECT method for quantitatively measuring tissue compositions of bone marrow regions in multiple myeloma and healthy participants using X-ray DECT as the reference. Secondary objectives include: To determine whether bone fraction in bone marrow differs between MM patients and healthy participants and whether PET-enabled DECT can accurately estimate bone fraction for correcting PET-based bone-marrow metabolic measurements; and, to evaluate relationships between corrected PET measures and bone marrow MRD and treatment response and toxicities of CAR T-cell therapy in MM patients This study is exploratory and is designed to collect preliminary data to support future larger studies. The research imaging is not intended to guide clinical care, and participants are not expected to receive direct medical benefit from participation. The information learned may help improve quantitative PET/CT imaging methods for future cancer evaluation and treatment monitoring.