Simultaneous Tc-99m and I-123 dual-radionuclide imaging with a solid-state detector-based brain-SPECT system and energy-based scatter correction

Abstract

BackgroundA brain single-photon emission computed tomography (SPECT) system using cadmium telluride (CdTe) solid-state detectors was previously developed. This CdTe-SPECT system is suitable for simultaneous dual-radionuclide imaging due to its fine energy resolution (6.6 %). However, the problems of down-scatter and low-energy tail due to the spectral characteristics of a pixelated solid-state detector should be addressed. The objective of this work was to develop a system for simultaneous Tc-99m and I-123 brain studies and evaluate its accuracy.MethodsA scatter correction method using five energy windows (FiveEWs) was developed. The windows are Tc-lower, Tc-main, shared sub-window of Tc-upper and I-lower, I-main, and I-upper. This FiveEW method uses pre-measured responses for primary gamma rays from each radionuclide to compensate for the overestimation of scatter by the triple-energy window method that is used. Two phantom experiments and a healthy volunteer experiment were conducted using the CdTe-SPECT system. A cylindrical phantom and a six-compartment phantom with five different mixtures of Tc-99m and I-123 and a cold one were scanned. The quantitative accuracy was evaluated using 18 regions of interest for each phantom. In the volunteer study, five healthy volunteers were injected with Tc-99m human serum albumin diethylene triamine pentaacetic acid (HSA-D) and scanned (single acquisition). They were then injected with I-123 N-isopropyl-4-iodoamphetamine hydrochloride (IMP) and scanned again (dual acquisition). The counts of the Tc-99m images for the single and dual acquisitions were compared.ResultsIn the cylindrical phantom experiments, the percentage difference (PD) between the single and dual acquisitions was 5.7 ± 4.0 % (mean ± standard deviation). In the six-compartment phantom experiment, the PDs between measured and injected activity for Tc-99m and I-123 were 14.4 ± 11.0 and 2.3 ± 1.8 %, respectively. In the volunteer study, the PD between the single and dual acquisitions was 4.5 ± 3.4 %.ConclusionsThis CdTe-SPECT system using the FiveEW method can provide accurate simultaneous dual-radionuclide imaging. A solid-state detector SPECT system using the FiveEW method will permit quantitative simultaneous Tc-99m and I-123 study to become clinically applicable.

Crosstalk Reduction Using a Dual Energy Window Scatter Correction in Compton Imaging

“…Multi-tracer imaging is still at an early stage of development; however, it has the potential for clinical and molecular application in many areas [11][12][13][14]. In simultaneous imaging, crosstalk artifacts reduce the power of the test and quantitative capability [17,18].…”

“…In particular, Compton cameras can simultaneously image multi-tracers, including single-photon emission computed tomography (SPECT) and positron-emission tomography (PET) tracers [5][6][7][8][9][10]. Simultaneous imaging has the potential for clinical and molecular application in many areas [11][12][13][14]. For example, hypoxia would be observed more precisely if blood flow and hypoxia could be observed simultaneously [15].…”

Attenuation correction in single-photon emission computed tomography for NURBS-based cardiac-torso phantom using dual-energy acquisition

“…In addition, some radioactive substances emit several levels of gamma-ray energy and the amount of counting and the attenuation coefficient vary at each energy level. [ 23 24 25 ]…”

Multiplexed imaging for diagnosis and therapy

“…Simultaneous imaging of SPECT tracers labelled with different isotopes is feasible on the basis of the distinct gamma energies. However, because of crosstalk between energy spectra and scatter, non-trivial correction methods must be applied, and the energy resolution of scanners is continuously sought to improve this outcome 166,167 . Despite this limitation, dual-tracer SPECT imaging is feasible using 201 Tl or 111 In in healthy volunteers and in diverse disease settings, and including brain imaging, cardiac imaging and cancer imaging 166,[168][169][170][171] .…”

“…However, because of crosstalk between energy spectra and scatter, non-trivial correction methods must be applied, and the energy resolution of scanners is continuously sought to improve this outcome 166,167 . Despite this limitation, dual-tracer SPECT imaging is feasible using 201 Tl or 111 In in healthy volunteers and in diverse disease settings, and including brain imaging, cardiac imaging and cancer imaging 166,[168][169][170][171] . Improved scanner technology 172 and kinetic analysis also promulgate simultaneous dual-isotope imaging in PET, as demonstrated for single-scan dual-tracer (staggered injection of FDG and FLT; 120 min of scan time) studies in patients with primary brain tumours 173 .…”