{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T00:49:46Z","timestamp":1760057386600,"version":"build-2065373602"},"reference-count":18,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,2,5]],"date-time":"2025-02-05T00:00:00Z","timestamp":1738713600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Applied Sciences"],"abstract":"<jats:p>Background: Accurate reconstruction and quantification in the post-therapy SPECT\/CT imaging of 166Ho microspheres for hepatic malignancies is crucial for treatment evaluation. This present study aimed to explore the impact of the OSEM reconstruction parameters on SPECT\/CT image features for dose distribution determination, using Hybrid Recon\u2122 (Hermes Medical Solutions AB) and full Monte Carlo (MC) collimator modeling. Methods: Image quality and activity quantification were assessed through two acquisitions of the Jaszczak phantom using a Siemens Symbia Intevo Bold SPECT\/CT system. The datasets were reconstructed using the OSEM method, with variations in the number of iterations for 15 and 8 subsets, both with and without full MC collimator modeling. Contrast recovery coefficient (QH), coefficient of variation (CV), contrast-to-noise ratio (CNR), calibration factor (CF), and activity recovery coefficient (ARC) were calculated and used to evaluate image quality and activity quantification. Results: Reconstructions with 5 iterations and 15 subsets, as well as 10 iterations and 8 subsets, were selected as the most suitable for 166Ho imaging, as they provided higher QH and ARCs. Incorporating full MC collimator modeling in both reconstructions led to significant improvements in image quality and activity recovery. The CFs remained consistent for a fixed value of 15 and 8 subsets, with values of (14.9 \u00b1 0.5) cps\/MBq and (14.6 \u00b1 0.5) cps\/MBq, respectively. However, when applying full collimator modeling, the CF values decreased to a range between 10.9 and 12.1 cps\/MBq. Conclusions: For 166Ho SPECT\/CT imaging, OSEM (with either 5 iterations and 15 subsets or 10 iterations and 8 subsets) combined with full MC collimator modeling yielded superior image quality and quantification results.<\/jats:p>","DOI":"10.3390\/app15031589","type":"journal-article","created":{"date-parts":[[2025,2,5]],"date-time":"2025-02-05T04:15:41Z","timestamp":1738728941000},"page":"1589","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Effect of OSEM Reconstruction Iteration Number and Monte Carlo Collimator Modeling on 166Ho Activity Quantification in SPECT\/CT"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-3211-9501","authenticated-orcid":false,"given":"Rita","family":"Albergueiro","sequence":"first","affiliation":[{"name":"Department of Physics and Astronomy, Faculty of Sciences of University of Porto (FCUP), Rua do Campo Alegre 1021 1055, 4169-007 Porto, Portugal"},{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center, Portuguese Oncology Institute of Porto, Rua Dr. Ant\u00f3nio Bernardino de Almeida, 4200-072 Porto, Portugal"},{"name":"Department of Nuclear Medicine, S\u00e3o Jo\u00e3o University Hospital Center, Alameda Prof. Hern\u00e2ni Monteiro, 4200-319 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7195-8791","authenticated-orcid":false,"given":"Vera","family":"Antunes","sequence":"additional","affiliation":[{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center, Portuguese Oncology Institute of Porto, Rua Dr. Ant\u00f3nio Bernardino de Almeida, 4200-072 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2465-5143","authenticated-orcid":false,"given":"Jo\u00e3o","family":"Santos","sequence":"additional","affiliation":[{"name":"Department of Physics and Astronomy, Faculty of Sciences of University of Porto (FCUP), Rua do Campo Alegre 1021 1055, 4169-007 Porto, Portugal"},{"name":"Medical Physics, Radiobiology and Radiation Protection Group, IPO Porto Research Center, Portuguese Oncology Institute of Porto, Rua Dr. Ant\u00f3nio Bernardino de Almeida, 4200-072 Porto, Portugal"},{"name":"Department of Nuclear Medicine, Santo Ant\u00f3nio University Hospital Center, Largo Prof. Abel Salazar, 4099-001 Porto, Portugal"},{"name":"Instituto de Ci\u00eancias Biom\u00e9dicas Abel Salazar (ICBAS), Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1053\/j.semnuclmed.2019.01.008","article-title":"Holmium-166 Microsphere Radioembolization of Hepatic Malignancies","volume":"49","author":"Reinders","year":"2019","journal-title":"Semin. Nucl. Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1186\/s40658-021-00372-9","article-title":"Gamma camera characterization at high holmium-166 activity in liver radioembolization","volume":"8","author":"Stella","year":"2021","journal-title":"EJNMMI Phys."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1634","DOI":"10.1007\/s00270-022-03187-y","article-title":"Holmium-166 Radioembolization: Current Status and Future Prospective","volume":"45","author":"Stella","year":"2022","journal-title":"Cardiovasc. Interv. Radiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2093","DOI":"10.2967\/jnumed.113.119768","article-title":"In vivo dosimetry based on SPECT and MR imaging of 166Ho-microspheres for treatment of liver malignancies","volume":"54","author":"Smits","year":"2013","journal-title":"J. Nucl. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"4773","DOI":"10.1088\/0031-9155\/51\/19\/004","article-title":"Hybrid scatter correction applied to quantitative holmium-166 SPECT","volume":"51","author":"Wit","year":"2006","journal-title":"Phys. Med. Biol."},{"key":"ref_6","unstructured":"Bonutti, F., Avolio, M., Magro, G., Cecotti, A., Schiava, E.D., Do, E.D., Longo, F., Herassi, Y., Bentayeb, F., and Rossi, M. (2015). Optimization of the image contrast in SPECT-CT bremsstrahlung imaging for Selective Internal Radiation Therapy of liver malignancies with Y-90 microspheres. arXiv."},{"key":"ref_7","unstructured":"Salvat, F., Fern\u00e1ndez-Varea, J.M., Bar\u00f3, J., and Sempau, J. (2024, February 13). PENELOPE, an Algorithm and Computer Code for Monte Carlo Simulation of Electron-Photon Showers, Available online: https:\/\/www.osti.gov\/etdeweb\/servlets\/purl\/20930131."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1186\/s13550-018-0361-0","article-title":"Phantom and clinical evaluation of the effect of full Monte Carlo collimator modelling in post-SIRT yttrium-90 Bremsstrahlung SPECT imaging","volume":"8","author":"Porter","year":"2018","journal-title":"EJNMMI Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"103166","DOI":"10.1016\/j.ejmp.2023.103166","article-title":"EFOMP policy statement NO. 19: Dosimetry in nuclear medicine therapy \u2013 Molecular radiotherapy","volume":"116","author":"Flux","year":"2023","journal-title":"Phys. Med."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Danieli, R., Milano, A., Gallo, S., Veronese, I., Lascialfari, A., Indovina, L., Botta, F., Ferrari, M., Cicchetti, A., and Raspanti, D. (2022). Personalized Dosimetry in Targeted Radiation Therapy: A Look to Methods, Tools and Critical Aspects. J. Pers. Med., 12.","DOI":"10.3390\/jpm12020205"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1186\/s40658-021-00365-8","article-title":"The effect of calibration factors and recovery coefficients on 177Lu SPECT activity quantification accuracy: A Monte Carlo study","volume":"8","author":"Ramonaheng","year":"2021","journal-title":"EJNMMI Phys."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1186\/s40658-019-0268-5","article-title":"Towards standardization of absolute SPECT\/CT quantification: A multi-center and multi-vendor phantom study","volume":"6","author":"Peters","year":"2019","journal-title":"EJNMMI Phys."},{"key":"ref_13","unstructured":"(2023, September 16). Emission Computed Tomography (ECT) Phantoms. Available online: http:\/\/www.orion-france.com\/pdf\/catalogues\/Orion_Data_Spectrum.pdf."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Elschot, M., Vermolen, B.J., Lam, M.G., de Keizer, B., van den Bosch, M.A., and de Jong, H.W. (2013). Quantitative Comparison of PET and Bremsstrahlung SPECT for Imaging the In Vivo Yttrium-90 Microsphere Distribution after Liver Radioembolization. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0055742"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"e13528","DOI":"10.1002\/acm2.13528","article-title":"Optimization of 99mTc whole-body SPECT\/CT image quality: A phantom study","volume":"23","author":"Alqahtani","year":"2022","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Cherry, S., Sorenson, J., and Phelps, M. (2012). Physics in Nuclear Medicine, Elsevier.","DOI":"10.1016\/B978-1-4160-5198-5.00001-0"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2456","DOI":"10.1007\/s00259-018-4136-7","article-title":"EANM practical guidance on uncertainty analysis for molecular radiotherapy absorbed dose calculations","volume":"45","author":"Gear","year":"2018","journal-title":"Eur. J. Nucl. Med. Mol. Imaging"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"268","DOI":"10.2967\/jnmt.113.131904","article-title":"Effect of varying number of OSEM subsets on PET lesion detectability","volume":"41","author":"Morey","year":"2013","journal-title":"J. Nucl. Med. Technol."}],"container-title":["Applied Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-3417\/15\/3\/1589\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T16:26:58Z","timestamp":1760027218000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-3417\/15\/3\/1589"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,2,5]]},"references-count":18,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,2]]}},"alternative-id":["app15031589"],"URL":"https:\/\/doi.org\/10.3390\/app15031589","relation":{},"ISSN":["2076-3417"],"issn-type":[{"type":"electronic","value":"2076-3417"}],"subject":[],"published":{"date-parts":[[2025,2,5]]}}}