Quantitative 166Ho-microspheres SPECT derived from a dual-isotope acquisition with 99mTc-colloid is clinically feasible
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-99m (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, VOITUMOR and VOIHEALTHY, 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 (VOILUNGS), 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 VOIHEALTHY, VOITUMOR and VOILUNGS 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.
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Posted 15 Jun, 2020
On 14 Jul, 2020
On 02 Jul, 2020
Received 30 Jun, 2020
On 25 Jun, 2020
Received 21 Jun, 2020
On 10 Jun, 2020
Invitations sent on 10 Jun, 2020
On 10 Jun, 2020
On 09 Jun, 2020
On 09 Jun, 2020
On 29 May, 2020
Received 25 May, 2020
On 22 May, 2020
Received 10 May, 2020
On 22 Apr, 2020
Invitations sent on 21 Apr, 2020
On 21 Apr, 2020
On 07 Apr, 2020
On 06 Apr, 2020
On 03 Apr, 2020
On 02 Apr, 2020
Quantitative 166Ho-microspheres SPECT derived from a dual-isotope acquisition with 99mTc-colloid is clinically feasible
Posted 15 Jun, 2020
On 14 Jul, 2020
On 02 Jul, 2020
Received 30 Jun, 2020
On 25 Jun, 2020
Received 21 Jun, 2020
On 10 Jun, 2020
Invitations sent on 10 Jun, 2020
On 10 Jun, 2020
On 09 Jun, 2020
On 09 Jun, 2020
On 29 May, 2020
Received 25 May, 2020
On 22 May, 2020
Received 10 May, 2020
On 22 Apr, 2020
Invitations sent on 21 Apr, 2020
On 21 Apr, 2020
On 07 Apr, 2020
On 06 Apr, 2020
On 03 Apr, 2020
On 02 Apr, 2020
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-99m (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, VOITUMOR and VOIHEALTHY, 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 (VOILUNGS), 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 VOIHEALTHY, VOITUMOR and VOILUNGS 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.
Figure 1
Figure 2
Figure 3
Figure 4