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Improving quantitative dosimetry in 177Lu-DOTATATE SPECT by energy window-based scatter corrections

de Nijs, Robina; Lagerburg, Verab,c; Klausen, Thomas L.a; Holm, Sørena

Nuclear Medicine Communications: May 2014 - Volume 35 - Issue 5 - p 522–533
doi: 10.1097/MNM.0000000000000079
Original Articles

Purpose Patient-specific dosimetry of lutetium-177 (177Lu)-DOTATATE treatment in neuroendocrine tumours is important, because uptake differs across patients. Single photon emission computer tomography (SPECT)-based dosimetry requires a conversion factor between the obtained counts and the activity, which depends on the collimator type, the utilized energy windows and the applied scatter correction techniques. In this study, energy window subtraction-based scatter correction methods are compared experimentally and quantitatively.

Materials and methods 177Lu SPECT images of a phantom with known activity concentration ratio between the uniform background and filled hollow spheres were acquired for three different collimators: low-energy high resolution (LEHR), low-energy general purpose (LEGP) and medium-energy general purpose (MEGP). Counts were collected in several energy windows, and scatter correction was performed by applying different methods such as effective scatter source estimation (ESSE), triple-energy and dual-energy window, double-photopeak window and downscatter correction. The intensity ratio between the spheres and the background was measured and corrected for the partial volume effect and used to compare the performance of the methods.

Results Low-energy collimators combined with 208 keV energy windows give rise to artefacts. For the 113 keV energy window, large differences were observed in the ratios for the spheres. For MEGP collimators with the ESSE correction technique, the measured ratio was close to the real ratio, and the differences between spheres were small.

Conclusion For quantitative 177Lu imaging MEGP collimators are advised. Both energy peaks can be utilized when the ESSE correction technique is applied. The difference between the calculated and the real ratio is less than 10% for both energy windows.

aDepartment of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

bDepartment of Clinical Physics, Spaarne Hospital, Hoofddorp

cDepartment of Medical Physics, Catharina Hospital, Eindhoven, The Netherlands

Correspondence to Robin de Nijs, MSc, PhD, Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen University Hospital, Section 4.01.2, Blegdamsvej 9, DK-2100 Copenhagen, Denmark Tel: +45 3545 4011; fax: +45 3545 4015; e-mail: robin.de.nijs@regionh.dk

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License, where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially. http://creativecommons.org/licenses/by-nc-nd/3.0.

Received November 11, 2013

Accepted December 18, 2013

© 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins