Multi-centre evaluation of accuracy and reproducibility of planar and SPECT image quantification: An IAEA phantom study.
Accurate quantitation of activity provides the basis for internal dosimetry of targeted radionuclide therapies. This study investigated quantitative imaging capabilities at sites with a variety of experience and equipment and assessed levels of errors in activity quantitation in Single-Photon Emission Computed Tomography (SPECT) and planar imaging. Participants from 9 countries took part in a comparison in which planar, SPECT and SPECT with X ray computed tomography (SPECT-CT) imaging were used to quantify activities of four epoxy-filled cylinders containing133Ba, which was chosen as a surrogate for131I. The sources, with nominal volumes of 2, 4, 6 and 23mL, were calibrated for133Ba activity by the National Institute of Standards and Technology, but the activity was initially unknown to the participants. Imaging was performed in a cylindrical phantom filled with water. Two trials were carried out in which the participants first estimated the activities using their local standard protocols, and then repeated the measurements using a standardized acquisition and analysis protocol. Finally, processing of the imaging data from the second trial was repeated by a single centre using a fixed protocol. In the first trial, the activities were underestimated by about 15% with planar imaging. SPECT with Chang's first order attenuation correction (Chang-AC) and SPECT-CT overestimated the activity by about 10%. The second trial showed moderate improvements in accuracy and variability. Planar imaging was subject to methodological errors, e.g., in the use of a transmission scan for attenuation correction. The use of Chang-AC was subject to variability from the definition of phantom contours. The project demonstrated the need for training and standardized protocols to achieve good levels of quantitative accuracy and precision in a multicentre setting. Absolute quantification of simple objects with no background was possible with the strictest protocol to about 6% with planar imaging and SPECT (with Chang-AC) and within 2% for SPECT-CT.
National Institute of Standards and Technology, Gaithersburg, MD, USA. Electronic address: bez@nist.gov.
Brian E
BE
Zimmerman
University Hospital Centre Zagreb, Zagreb, Croatia.
Darko
D
Grošev
Service Hospitalier Frédéric Joliot, Paris, France.
Irène
I
Buvat
Medscan Concepción, Concepción, Chile.
Marco A
MA
Coca Pérez
Johns Hopkins University, Baltimore, USA.
Eric C
EC
Frey
National Physical Laboratory, Teddington, UK.
Alan
A
Green
Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Anchali
A
Krisanachinda
University Würzburg, Würzburg, Germany.
Michael
M
Lassmann
Lund University, Lund, Sweden.
Michael
M
Ljungberg
Institute of Energy and Nuclear Research, São Paulo, Brazil.
Lorena
L
Pozzo
National Institute of Nuclear Medicine & Allied Sciences, Dhaka, Bangladesh.
Kamila Afroj
KA
Quadir
Universidad de la República, Montevideo, Uruguay.
Mariella A
MA
Terán Gretter
University of the Free State, Bloemfontein, South Africa.
Johann
J
Van Staden
International Atomic Energy Agency, Vienna, Austria.
Gian Luca
GL
Poli
D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging / Q000592:standards*; D011874:Radiometry; D015203:Reproducibility of Results; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods / Q000592:standards*
Comparison; SPECT; Vergleichsstudie; planar; quantitative Bildgebung; quantitative imaging