Dataset Information

Quantitative ¹⁶⁶Ho-microspheres SPECT derived from a dual-isotope acquisition with ^99mTc-colloid is clinically feasible.

ABSTRACT:

Purpose

Accurate dosimetry is essential in radioembolization. To this purpose, an automatic protocol for healthy liver dosimetry based on dual isotope (DI) SPECT imaging, combining holmium-166 (¹⁶⁶Ho)-microspheres, and technetium-99?m (^99mTc)-colloid was developed: ¹⁶⁶Ho-microspheres used as scout and therapeutic particles, and ^99mTc-colloid to identify the healthy liver. DI SPECT allows for an automatic and accurate estimation of absorbed doses, introducing true personalized dosimetry. However, photon crosstalk between isotopes can compromise image quality. This study investigates the effect of ^99mTc downscatter on ¹⁶⁶Ho dosimetry, by comparing ¹⁶⁶Ho-SPECT reconstructions of patient scans acquired before (¹⁶⁶Ho-only) and after additional administration of ^99mTc-colloid (¹⁶⁶Ho-DI).

Methods

The ¹⁶⁶Ho-only and ¹⁶⁶Ho-DI scans were performed in short succession by injecting ^99mTc-colloid on the scanner table. To compensate for ^99mTc downscatter, its influence was accounted for in the DI image reconstruction using energy window-based scatter correction methods. The qualitative assessment was performed by independent blinded comparison by two nuclear medicine physicians assessing 65 pairs of SPECT/CT. Inter-observer agreement was tested by Cohen's kappa coefficient. For the quantitative analysis, two volumes of interest within the liver, VOI_TUMOR, and VOI_HEALTHY were manually delineated on the ¹⁶⁶Ho-only reconstruction and transferred to the co-registered ¹⁶⁶Ho-DI reconstruction. Absorbed dose within the resulting VOIs, and in the lungs (VOI_LUNGS), was calculated based on the administered therapeutic activity.

Results

The qualitative assessment showed no distinct clinical preference for either ¹⁶⁶Ho-only or ¹⁶⁶Ho-DI SPECT (kappa = 0.093). Quantitative analysis indicated that the mean absorbed dose difference between ¹⁶⁶Ho-DI and ¹⁶⁶Ho-only was - 2.00 ± 2.84?Gy (median 27?Gy; p value < 0.00001), - 5.27 ± 8.99?Gy (median 116?Gy; p value = 0.00035), and 0.80 ± 1.08?Gy (median 3?Gy; p value < 0.00001) for VOI_HEALTHY, VOI_TUMOR, and VOI_LUNGS, respectively. The corresponding Pearson's correlation coefficient between ¹⁶⁶Ho-only and ¹⁶⁶Ho-DI for absorbed dose was 0.97, 0.99, and 0.82, respectively.

Conclusion

The DI protocol enables automatic dosimetry with undiminished image quality and accuracy.

Clinical trials

The clinical study mentioned is registered with Clinicaltrials.gov (NCT02067988) on 20 February 2014.

SUBMITTER: Stella M

PROVIDER: S-EPMC7359973 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Publications

Quantitative 166Ho-microspheres SPECT derived from a dual-isotope acquisition with 99mTc-colloid is clinically feasible.

Stella M M Braat Ajat A Lam Mgeh M de Jong Hwam H van Rooij R R

EJNMMI physics 20200714 1

<h4>Purpose</h4>Accurate dosimetry is essential in radioembolization. To this purpose, an automatic protocol for healthy liver dosimetry based on dual isotope (DI) SPECT imaging, combining holmium-166 (166Ho)-microspheres, and technetium-99 m (99mTc)-colloid was developed: 166Ho-microspheres used as scout and therapeutic particles, and 99mTc-colloid to identify the healthy liver. DI SPECT allows for an automatic and accurate estimation of absorbed dose ...[more]

PMID: 32666401

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