Comparison of the ⁹⁰Y-labelled glass microspheres liver radioembolisation dosimetry with the estimated dosimetry obtained from pre-treatment ^99mTc-MAA SPECT images reconstructed with and without attenuation correction

ABSTRACT

⁹⁰Y-labelled glass microspheres liver radioembolisation is an effective treatment for unresectable hepatic tumours. Its treatment planning is based on ^99mTc-macro-aggregated albumin (MAA) single photon emission computed tomography (SPECT) imaging. However, photons interaction with human tissues may significantly compromise the accuracy of radioactivity quantification in nuclear medicine. The aim of this work is to evaluate the impact of a patient-specific attenuation correction on pre-treatment ^99mTc-MAA SPECT images and, consequently, on the estimation of radioembolisation dosimetry. The methodology developed for attenuation correction was firstly validated on phantom models. Following this, a data set of eight patients was retrospectively selected from our database and the pre-treatment images were reconstructed with and without attenuation correction. Then, the liver dosimetry maps were estimated and compared with the liver dosimetry maps estimated from the post-treatment ⁹⁰Y positron emission tomography images. Results show that the attenuation corrected phantom images were greatly improved, originating higher contrast, signal-to-noise ratio and contrast-to-noise ratio comparatively to non-attenuation corrected images. Attenuation corrected clinical pre-treatment images significantly increase the agreement, measured with the intraclass correlation coefficient, between predictive and post-treatment dosimetry maps comparatively to the non-attenuation corrected ones (Wilcoxon test, p = 0.008). In conclusion, a statistically significant increase in the agreement was achieved; however, poor correlation is still observed at the single-voxel level in some patients. Thus, future research should be addressed to investigate the reasons of this and manage to optimise the agreement between the predictive and post-treatment dosimetry.

KEYWORDS:

• Hepatic tumours
• ⁹⁰Y liver radioembolisation
• ^99mTc-MAA SPECT imaging
• CT-based attenuation correction
• patient-specific radionuclide dosimetry

Acknowledgments

We gratefully thank professors Lidia S. Ferreira, Enrico Maglione and M. Gabriella Signorini for their sincere advice during these months. Moreover, we wish to sincerely acknowledge all the technical staff at the Nuclear Medicine Radiopharmacology Department, Champalimaud Center for the Unknown, Champalimaud Foundation, Lisbon, for their dedication and passion, without whom all data would have not been possible to be acquired.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics

All patients attending the Champalimaud Centre for the Unknown signed informed written consent as per local Ethics Committee guidelines. The retrospective analysis was completely blind of patient identification.