Absolute quantification in SPECT

Abstract

Single-photon emission computed tomography (SPECT) allows the three-dimensional visualization of radioactivity within the human body and is widely used for clinical purposes. In SPECT, image quality is compromised by several factors including photon attenuation, photon scatter, the partial volume effect, and motion artefacts. These variables also confound the capacity of SPECT to quantify the concentration of radioactivity within given volumes of interest in absolute units, e.g. as kilobecquerels per cubic centimetre. In the last decade, considerable technical progress has been achieved in SPECT image reconstruction, involving, in particular, the development of iterative image reconstruction techniques. Furthermore, hybrid cameras integrating a SPECT camera with an X-ray CT scanner have become commercially available. These systems allow the acquisition of SPECT and CT datasets registered to each other with a high anatomical accuracy. First studies have shown that iterative SPECT image reconstruction techniques incorporating information from SPECT/CT image datasets greatly increase the accuracy of SPECT in quantifying radioactivity concentrations in phantoms and also in humans. This new potential of SPECT may improve not only diagnostic accuracy, but also dosimetry for internal radiotherapy.

Impact of a commercial 3D OSEM reconstruction algorithm on the 177Lu activity quantification of SPECT/CT imaging in a Molecular Radiotherapy trial

“…As regards clinical SPECT quantification [14], iterative reconstruction algorithms [15] are the state of the art and they are generally recommended. They are critical in the SPECT/CT image formation chain, and together with target VOIs and quantification protocols, they represent the three main components in activity quantification in SPECT/CT systems.…”

The Use of Anatomical Information for Molecular Image Reconstruction Algorithms: Attenuation/Scatter Correction, Motion Compensation, and Noise Reduction

“…Novel software such as new iterative image reconstruction algorithms and various artifact correction methods are also key factors for improving the image quality of nuclear medicine [11,12]. Using accurate statistical models for image reconstruction algorithms has brought significant improvement in image quality.…”

“…Iterative image reconstruction methods for emission tomography were comprehensively reviewed in [18]. Well-aligned anatomical information from hybrid scanners enabled advances of various correction methods such as attenuation corrections [19] and scatter corrections [20,21] for better quantitative and qualitative imaging [12].…”

Matched pairs for radionuclide-based imaging and therapy

“…However, there has been recent progress in this field for SPECT. The current state of SPECT quantification is described in the paper by Ritt et al [14].…”