New SPECT technology: potential and challenges

Abstract

Potential Major advances in organ-specific imagingThe article by Bocher et al. in this issue [1] reports on the performance of a novel SPECT system specifically designed for cardiac imaging based on the use of a set of pinhole collimators in combination with cadmium zinc telluride (CZT) detectors. The system is inspired by earlier work on multipinhole imaging [2] and the conceptual design has previously been demonstrated in simulation studies [3]. Also early clinical validation studies have appeared recently [4,5]. The described system (available from GE Healthcare) joins a range of novel organ-specific commercial systems that have recently been introduced to the consumer with reported improvement in resolution and sensitivity (usually reported as potential for reduced acquisition time; see recent reviews [6,7]). Specific examples are the D-SPECT from Spectrum Dynamics [8,9] and the Cardius from Digirad [10]. Clinical validation studies for these systems are now also appearing (e.g. [11,12]). The developers of these systems deserve congratulations for introducing innovations that undoubtedly yield the largest advance in SPECT performance since the introduction of the rotating gamma camera, which has dominated clinical use for several decades. Until recently the development in SPECT performance has been incremental, mainly involving refinement rather than major changes in system design, perhaps mainly due to the clinical demand for systems that offer flexibility in application. The recent innovation has been inspired at least partly by the rapid developments in preclinical imaging systems where ultrahigh resolution and relatively high sensitivity have been demonstrated. Bringing new designs to fruition has only been possible due to the combination of several factors: the improved reliability of alternative detector materials, the development of fast electronics, the development of efficient reconstruction algorithms and, not least, the demand for organ-specific systems where optimization for a specific purpose rather than flexibility in application is indicated. CZT: pros and consCentral to the design of both the GE Healthcare system and the D-SPECT is the use of CZT. Although not a new detector material, it is only recently that the reliability and performance of CZT at room temperature have been sufficiently improved to make clinical use a possibility. The cost of CZT remains relatively high and places a constraint on the possible designs. But the appeal is not just the much improved energy resolution (typically 5-6%) but particularly the small size that facilitates novel compact designs, which are very much appealing for use in organspecific imaging. There are alternative approaches to achieving compact designs based on conventional scintillation detectors coupled to optical readout systems other than conventional photomultiplier tubes (e.g. avalanche photodiode or silicon photomultiplier), which may have a cost advantage (see [13] for a useful overview). We can anticipate increasing use of new technology in f...

Review on the characteristics of radiation detectors for dosimetry and imaging

“…In single-photon emission computed tomography (SPECT), recent improvements in the reliability and performance of cadmium zinc telluride (CZT, see section 4.3.4) detectors have not only allowed improvements in energy resolution (CZT energy resolution typically 5-6%), but also the construction of compact and novel detector geometries (Hutton 2010). The improved energy resolution can not only improve image quality with better scatter rejection, but also allow dual radionuclide imaging -for example, the use of 99m Tc and 201 Tl for simultaneous rest/stress myocardial perfusion imaging (Ben-Haim et al 2010).…”

Rapid additive manufacturing of MR compatible multipinhole collimators with selective laser melting of tungsten powder

“…The expected pinhole resolution [formula (3)] and the expected number of detections [formula (6)] were calculated using the ideal pinhole diameters (500 μm) and using the measured pinhole diameters (see Sec. II.D.2).…”

“…For the majority of studies, a parallel hole collimator is used, but there is an increased use and need for more complex shaped collimators for imaging specific organs (heart, brain 2, 3 ) or small objects (mice, rats). Especially in cardiac [4][5][6] and small animal imaging, 7,8 systems with complex collimator geometries have been designed. These systems often have a high number of pinholes (e.g., 75 pinholes in the U-SPECT II system, 9 300 pinholes in the VECTor system 10 ).…”

Dual-layer collimator for improved spatial resolution in SPECT with CZT camera: an analytical and Monte Carlo study

“…Compared to monolithic NaI-PMTs tandem, CZT detectors have a better energy resolution, are more robust, their performances are not altered by aging as such as for the PMTs and they do not require a large outer dead area. This last property allows setting several compact detectors close together according to a geometry which focuses on a narrow region of interest which increases the sensitivity on this region (Hutton 2010, Germano et al 2013. Nine swiveling vertical columns equipped with a one hole matching pixel detector (1HMPD) configuration has been developed by Spectrum Dynamics for the DSPECT system (Erlandsson et al 2009).…”