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...

Cross sections for the reactions Mn(n, p), Fe(n, p), and Ni(n, p) have been measured at an incident energy of 198 MeV, with protons observed over a range of energies corresponding to excitations of up to about 35 MeV in the residual nuclei Cr, Mn, and Co, respectively. Measurements were carried out at center-of-mass angles between 1. 6' and 19. 9'. A multipole analysis of the results yielded the distribution of Gamow-Teller (GT) and spin-dipole strength for each target. The total GT strength below an excitation energy of 8.5 MeV was 1.? units for Mn, 2.9 units for Fe, and 3.8 units for Ni. Shell model calculations of the GT strength distribution, carried out in a restricted vector space, show fair to good agreement with the data up to an excitation energy of 8.5 MeV, but overestimate the total strength by a factor of between 3 and 4.

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The goal of this study was to determine the quantitative accuracy of our OSEM-APDI reconstruction method based on SPECT/CT imaging for Tc-99m, In-111, I-123, and I-131 isotopes. Phantom studies were performed on a SPECT/low-dose multislice CT system (Infinia-Hawkeye-4 slice, GE Healthcare) using clinical acquisition protocols. Two radioactive sources were centrally and peripherally placed inside an anthropometric Thorax phantom filled with non-radioactive water. Corrections for attenuation, scatter, collimator blurring and collimator septal penetration were applied and their contribution to the overall accuracy of the reconstruction was evaluated. Reconstruction with the most comprehensive set of corrections resulted in activity estimation with error levels of 3-5% for all the isotopes.

In this work is presented a method for analytically cdculating the distribution of photons detected in SPECT projections. The technique is appLicabIe to sources in homogeneous and non-homogeneous media. The photon distribution (primary, first and second order Compton scatter, and first order Rayleigh scatter) is computed using precdculated camera-dependent lookup tables in conjunction with an attenuation map of the scattering object aad a map of the activity distribution.The resdts of the technique are in excellent agreement with those of Monte Carlo simulation and experimental phantom studies. It has b e n validated with respect to sources in both homogeneous and noa-homogeneous media.Compared with a similar andyticd technique, it offers a factor of 40-60 decrease in the cdculation time for higher order Compton scatter distributions. For small sources, it improves on computation tirne required by Monte Carlo simulators by a factor of 20-150.Finally, this method has been applied to the problem of correcting for cross-taik in 1231-99mT~ dual-isotope SPECT studies. It has demonstrated the ability to accurately reproduce the shape of the cross-talk distribution and to reproduce the absolute activity of the sources to within 7%, dowing accurate removai of cross-talk contamination. Abstract. . 11

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Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and ¹⁰⁰Mo(p,2n)(99m)Tc reaction has been considered. In this context, the production yields of (99m)Tc and various other radioactive and stable isotopes which will be created in the process have to be investigated, as these may affect the diagnostic outcome and radiation dosimetry in human studies. Reaction conditions (beam and target characteristics, and irradiation and cooling times) need to be optimized in order to maximize the amount of (99m)Tc and minimize impurities. Although ultimately careful experimental verification of these conditions must be performed, theoretical calculations can provide the initial guidance allowing for extensive investigations at little cost. We report the results of theoretically determined reaction yields for (99m)Tc and other radioactive isotopes created when natural and enriched molybdenum targets are irradiated by protons. The cross-section calculations were performed using a computer program EMPIRE for the proton energy range 6-30 MeV. A computer graphical user interface for automatic calculation of production yields taking into account various reaction channels leading to the same final product has been created. The proposed approach allows us to theoretically estimate the amount of (99m)Tc and its ratio relative to (99g)Tc and other radioisotopes which must be considered reaction contaminants, potentially contributing to additional patient dose in diagnostic studies.

The (n, p) reaction has been studied on the nuclei V and Co at an energy of 198 MeV. Spectra were measured at laboratory angles of 0, 4, 8', l2', 16', and 20' up to an excitation energy of 35 MeV in the Anal nuclei Ti and Fe. A multipole analysis of the data up to 30 MeV was carried out to identify Gamow-Teller (GT) (AL = 0, AJ = 1+) and spin-dipole (AL = 1, AJ = 0, 1,2 ) strengths. GT strength is concentrated in a resonance with centroid energy of 5.2 MeV in Ti and 4.1 MeV in Fe. The spin-dipole strength appears as a broad resonance with centroid energy about 16 MeV in both nuclei. Shell model calculations of the GT strength reproduce the energy distribution reasonably well, but the calculated strength exceeds the measurement by a factor of about 4.