MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

Abstract

The accuracy of absorbed dose calculations in personalized internal radionuclide therapy is directly related to the accuracy of the activity (or activity concentration) estimates obtained at each of the imaging time points. MIRD Pamphlet no. 23 presented a general overview of methods that are required for quantitative SPECT imaging. The present document is next in a series of isotope-specific guidelines and recommendations that follow the general information that was provided in MIRD 23. This paper focuses on 177 Lu (lutetium) and its application in radiopharmaceutical therapy. Theradi onuclide 177 Lu (lutetium) has been proven useful in several targeted radionuclide therapies because of its favorable decay characteristics and the possibility of reliable labeling of biomolecules used for tumor targeting. Initially, 177 Lu was used in a colloidal form for interstitial injections for sterilization of peritumoral lymph nodes (1). A second important clinical application of 177 Lu has been for peptide receptor radionuclide therapy (PRRT) with 177 Lu-DOTATATE and other structurally related peptides. The PRRT use in treatment of neuroendocrine tumors (NETs) is motivated by the fact that the carrier peptide, octreotate, shows highaffinity binding to somatostatin receptors, which are overexpressed on the cell surface of many NETs (2-6). Furthermore, 177 Lu has been used in radioimmunotherapy clinical trials to label different kinds of monoclonal antibodies (7-15).There is a growing body of evidence that radionuclide therapy should follow patient-specific planning protocols, similar to those that are being routinely used in external-beam radiation therapy. Recent literature reviews show correlations between absorbed dose and tumor response as well as normal-tissue toxicity (16). Such correlations indicate that treatments should be based on personalized dosimetry, aiming to deliver therapeutically effective absorbed doses to tumors, while keeping doses to organs at risk below the threshold levels for deterministic adverse effects. In clinical PRRT studies, the primary adverse effects have been mainly renal and hematologic toxicities (2,6).Although several studies have reported estimates of absorbed doses (4,7-9,12) for 177 Lu-DOTATATE PRRT and 177 Lu radioimmunotherapy, most of these estimates have been based on planar imaging and conjugate-view activity quantification. Planar imaging, however, is known to have inherent limitations regarding the accuracy of activity quantification (17). As a result, an increasing number of clinical dosimetry protocols currently include 177 Lu SPECT/CT imaging studies (15,(17)(18)(19) because of their superior accuracy. Comparisons of renal dose estimates in 177 Lu-DOTATATE PRRT based on planar imaging and SPECT/CT, for example, have been reported (17,20) and are summarized in Cremonesi et al. (21).This document presents a set of guidelines outlining data acquisition protocols and image reconstruction techniques that are recommended for quantitative 177 Lu SPECT imaging. The guidelines are...

Impact of a commercial 3D OSEM reconstruction algorithm on the 177Lu activity quantification of SPECT/CT imaging in a Molecular Radiotherapy trial

“…Zoom of 1, circular radius of rotation of 330 mm (around the phantom surface) and image matrix of 128x128 pixels were set, resulting in a 4.8 mm pixel size image. In acquisition, the energy windows of the two dominant photopeaks of 177 Lu [4] were set at 113keV ± 7.5% and 208.4keV ± 7.5%, as also described in Grassi et al [30]. As regards the lower energy photopeak, the TEW scatter correction was employed and the lower scatter window was set in the range from 87.58keV to 104.53keV (using a default window weight of 0.5), while the upper scatter window from 121.47keV to 130.51keV (using a default window weight of 0.9375).…”

“…Several investigations have been reported on the performance of such algorithm on radionuclides frequently used in nuclear medicine, for patient imaging as well as patient specific dosimetry. Some of the more pertinent publications include improvements in correction techniques for quantification in SPECT [4,[17][18][19][20], evaluations of the accuracy of quantitative image reconstruction techniques [21][22][23][24][25] and comparisons of resolution between SPECT/CT systems using machine-specific reconstruction algorithms [26][27][28]. In these studies, the OSEM reconstruction parameters (i.e.…”

Design and Fabrication of Kidney Phantoms for Internal Radiation Dosimetry Using 3D Printing Technology

“…From the results of this work, it can be concluded that PLA-based FDM 3D printing along with an epoxy coating enables the production of chemically stable, fillable phantoms that are sufficiently durable for SPECT/CT calibration studies. Although no significant differences in partial-volume effects were found between the kidney-shaped and the spherically shaped single-compartment phantoms, this conclusion will have to be reevaluated for more realistic kidney geometries, in which a low-activity inner region is typically surrounded by a ring of higher activity (5).…”

Individualized Dosimetry for Theranostics: Necessary, Nice to Have, or Counterproductive?

“…Peritherapeutic dosimetry in molecular radiotherapies with 177 Lu-labeled compounds, although sometimes limited by the availability of patients for late-time-point measurements, can be easily performed with limited technical difficulties (54). Most importantly, the demonstration of a tumor dose-response relationship (42) and the observation of minimal differences between cycles (12,41) indicate that posttherapeutic dosimetry after a first treatment cycle predicts the absorbed doses in further cycles.…”