Pair production tomography enables imaging of MeV-scale gamma-emitting theranostic radionuclides

Pair production tomography enables imaging of MeV-scale gamma-emitting theranostic radionuclides | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Pair production tomography enables imaging of MeV-scale gamma-emitting theranostic radionuclides Youngho Seo, Biswajit Das, Robin Peter This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9349692/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract High-energy gamma-emissions significantly degrade image quality when imaging theranostic cancer radiopharmaceuticals with conventional SPECT scanners, especially at low activities used in targeted alpha therapy. PET imaging offers sensitivity and energy discrimination benefits, but is conventionally limited to positron-emitting isotopes. Pair production tomography (PPT) addresses this limitation by enabling localization of high-energy γ rays: when a γ ray with energy ≥ 2mec2 (1.022 MeV) undergoes pair production, it generates an e+e− pair, and the positron subsequently annihilates, emitting two coincident 511 keV photons that can be detected for tomographic reconstruction. In this work, we present the first experimental demonstration of PPT in the context of 212Pb targeted alpha therapy, using 2.617 MeV γ rays emitted from its decay daughter 208Tl. 212Pb-filled phantoms were successfully imaged through PPT using time-of-flight clinical and non-time-of-flight preclinical PET systems, with SPECT images acquired for comparison. Monte Carlo simulations further support the experimental data and PPT mechanism. These findings establish the feasibility of PPT imaging for high-energy γ-emitters and motivate improvements in timing, reconstruction, and detector technologies for novel radiopharmaceutical imaging. Physical sciences/Physics/Nuclear physics/Experimental nuclear physics Health sciences/Medical research/Translational research High energy γ and pair-production pair-production tomography targeted alpha therapy 212Pb daughter imaging PET imaging Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9349692","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":630602872,"identity":"d8e0a27b-af75-4d45-b27f-5c27d59b08d3","order_by":0,"name":"Youngho Seo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYLACxgYI9QBI8AOxAdFamEFKJRtI0cImQZQWg+M9Zg+/7rBhkG9vPlbNU1MnwcDevE0Cr5YzZ8yNZc+kARnH0m7zHDsswcBzrAy/lhs5ZtKSbYcZDCRyzG7zNhyoYwAyiNMiP/+NWTFvA9Bh8m8Ia5H8CNTCcIPHjJm3gVmCQYIHvxbJM8fKpBnb0ngMzqQlS84B+oWNJ63YAp8WvuPN2yR/ttnIybcfPvjhDTDE+NkPb7yBT4vCAWAU8jAw8MBF2PApBwH5BmBM/iCkahSMglEwCkY2AACqXUO0Nr1awQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-5908-6636","institution":"University of California, San Francisco","correspondingAuthor":true,"prefix":"","firstName":"Youngho","middleName":"","lastName":"Seo","suffix":""},{"id":630602873,"identity":"42ba124a-3df9-46d6-b342-78e4e4f6f2b9","order_by":1,"name":"Biswajit Das","email":"","orcid":"","institution":"University of California, San Francisco","correspondingAuthor":false,"prefix":"","firstName":"Biswajit","middleName":"","lastName":"Das","suffix":""},{"id":630602874,"identity":"4ff4bf11-880e-4830-a45a-0e4e11aa1b27","order_by":2,"name":"Robin Peter","email":"","orcid":"","institution":"University of California, San Francisco","correspondingAuthor":false,"prefix":"","firstName":"Robin","middleName":"","lastName":"Peter","suffix":""}],"badges":[],"createdAt":"2026-04-07 23:00:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9349692/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9349692/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108379811,"identity":"9e527c86-b125-4435-94ee-d49e94642dad","added_by":"auto","created_at":"2026-05-04 04:26:47","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3673499,"visible":true,"origin":"","legend":"Article File","description":"","filename":"BDRPYSP2T208Pbimgv3.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9349692/v1_covered_ed149c87-ff43-4221-be95-f101f23930bb.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Pair production tomography enables imaging of MeV-scale gamma-emitting theranostic radionuclides","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"High energy γ and pair-production, pair-production tomography, targeted alpha therapy, 212Pb daughter imaging, PET imaging","lastPublishedDoi":"10.21203/rs.3.rs-9349692/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9349692/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"High-energy gamma-emissions significantly degrade image quality when imaging theranostic cancer radiopharmaceuticals with conventional SPECT scanners, especially at low activities used in targeted alpha therapy. 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