title: Dual-modality imaging of cancer with SPECT/CT.
abstract: Dual-modality imaging is an in vivo diagnostic technique that obtains structural and functional information directly from patient studies in a way that cannot be achieved with separate imaging systems alone. Dual-modality imaging systems are configured by combining computed tomography (CT) with radionuclide imaging (using positron emission tomography (PET) or single-photon emission computed tomography (SPECT)) on a single gantry which allows both functional and structural imaging to be performed during a single imaging session without having the patient leave the imaging system. A SPECT/CT system developed at UCSF is being used in a study to determine if dual-modality imaging offers advantages for assessment of patients with prostate cancer using (111)In-ProstaScint, a radiolabeled antibody for the prostate-specific membrane antigen. (111)In-ProstaScint images are reconstructed using an iterative maximum-likelihood expectation-maximization (ML-EM) algorithm with correction for photon attenuation using a patient-specific map of attenuation coefficients derived from CT. The ML-EM algorithm accounts for the dual-photon nature of the 111In-labeled radionuclide, and incorporates correction for the geometric response of the radionuclide collimator. The radionuclide image then can be coregistered and overlaid in color on a grayscale CT image for improved localization of the functional information from SPECT. Radionuclide images obtained with SPECT/CT and reconstructed using ML-EM with correction for photon attenuation and collimator response improve image quality in comparison to conventional radionuclide images obtained with filtered backprojection reconstruction. These results illustrate the potential advantages of dual-modality imaging for improving the quality and the localization of radionuclide uptake for staging disease, planning treatment, and monitoring therapeutic response in patients with cancer.
authors.affiliation: UCSF Physics Research Laboratory, 389 Oyster Point Blvd, Suite 1, South San Francisco, CA 94080, USA. bruceh@itsa.ucsf.edu
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Hasegawa
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Wong
authors.forename: Koji
authors.initials: K
authors.lastname: Iwata
authors.forename: William C
authors.initials: WC
authors.lastname: Barber
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Hwang
authors.forename: Anne E
authors.initials: AE
authors.lastname: Sakdinawat
authors.forename: Mohan
authors.initials: M
authors.lastname: Ramaswamy
authors.forename: David C
authors.initials: DC
authors.lastname: Price
authors.forename: Randall A
authors.initials: RA
authors.lastname: Hawkins
mesh_terms: D000465:Algorithms; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*