A method and apparatus for the integration of an ultrasound transducer with a SPECT imaging system is disclosed. The ultrasound transducer allows the delivery of particle-born drug therapies or thermally active therapies at the same site detected with SPECT imaging. The system includes a SPECT imaging subsystem; an ultrasound transducer for producing a signal representative of applied ultrasound and signally coupled to the SPECT imaging subsystem; and co-registering means for co-registering the signal representative of applied ultrasound in a coordinate system of SPECT imaging subsystem. The SPECT subsystem may be replaced with a SPECT/CT combined system to provide morphology that allows for treatment planning. In another embodiment, the ultrasound transducer can be used intermittently with the sequential gathering of SPECT images for tracking time-varying properties of the binding of specific SPECT contrast agents to biomarkers of disease. In this way, the ultrasound and SPECT imaging devices form a novel combination to improve patient care through improved spatial registration, therapy planning, and workflow.