A Neck-Thyroid Phantom with Small Sizes of Thyroid Remnants for Postsurgical I-123 and I-131 SPECT/CT Imaging

Abstract

Post-surgical I-123 and I-131 SPECT/CT imaging can provide information on the presence and sizes of thyroid remnants and/or metastasis for an accurate re-staging of disease to apply an individualized radioiodine therapy. The purpose of this study was to develop and validate a neck–thyroid phantom with small sizes of thyroid remnants to be utilized for the optimization of post-surgical SPECT/CT imaging. 3D printing and molding techniques were used to develop the hollow human-shaped and -sized phantom which enclosed the trachea, esophagus, cervical spine, clavicle, and multiple detachable sections with different sizes of thyroid remnant in clinically relevant positions. CT images were acquired to evaluate the morphology of the phantom and the sizes of remnants. Triple-energy window scattered and attenuation corrected SPECT images were acquired for this phantom and for a modified RS-542 commercial solid neck–thyroid phantom. The response and sensitivity of the SPECT modality for different administered I-123 and I-131 activities within the equal-size remnants of both phantoms were calculated. When we compared the phantoms, using the same radiopharmaceutical and similar activities, we found that the measured sensitivities were comparable. In all cases, the I-123 counting rate was higher than the I-131 one. This phantom with capabilities to insert different small sizes of remnants and simulate different background-to-remnants activity ratios can be utilized to evaluate postsurgical thyroid SPECT/CT imaging procedures.

The Impact of Dual and Triple Energy Window Scatter Correction on I-123 Postsurgical Thyroid SPECT/CT Imaging Using a Phantom with Small Sizes of Thyroid Remnants

“…Figure 4 shows the measured counts by drawing line profiles in the lateral direction of slices with a uniform background (R bkg of 5% and 10%) from the NSC, DEW and TEW scatter-corrected SPECT/CT images. The selected slices were located between the trachea and the remnants of the phantom [26]. The average background counts, the standard deviation (noise) and the %COV from these slices are shown in Table 3.…”

“…I-123 SPECT/CT images from a neck-thyroid phantom with thyroid remnants were utilized. The phantom was specifically designed for postsurgical thyroid imaging and was developed using 3D printing and moulding techniques [26]. The phantom can accommodate remnants of various small sizes, at clinically relevant positions, and can simulate different background-to-remnant activity ratios.…”

“…Three different sections, with two rem nants in each section of specific sizes and locations, were used for these acquisitions (F ure 1). Any section could be easily attached to the phantom to study different sizes remnants [26]. All images were acquired using the dual-head GE Infinia Hawkeye 4 SPECT/4-slice-CT hybrid scanner (GE Healthcare, Milwaukee, WI, USA) at the Bank of Cyprus Oncology Centre following the clinical protocols.…”

“…Three different sections, with two remnants in each section of specific sizes and locations, were used for these acquisitions (Figure 1). Any section could be easily attached to the phantom to study different sizes of remnants [26].…”