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This study aimed to evaluate whether quantitative magnetic resonance imaging (qMRI) can characterize collagen-rich PF-associated pathways using histology as a structural ground truth.<\/jats:p>\n <\/jats:sec>\n \n Materials and methods<\/jats:title>\n \n Ex vivo<\/jats:italic>\n porcine left ventricular specimens were imaged at 3\u2009T using relaxation-based mapping techniques, including\n T<\/jats:italic>\n RAFF<\/jats:sub>\n ,\n T<\/jats:italic>\n 1\u03c1<\/jats:sub>\n ,\n T<\/jats:italic>\n 2<\/jats:sub>\n and\n T<\/jats:italic>\n 1<\/jats:sub>\n mapping. Corresponding Masson\u2019s trichrome sections were processed into optical density maps to segment myocardium, collagen and PF-associated regions. Histology-defined regions of interest were used to identify collagen-enriched PF-associated pathways and remote myocardium. Relaxation time contrast was quantified using relative relaxation time difference (RRTD). Statistical comparisons were performed using paired\n t<\/jats:italic>\n -tests with Benjamini\u2013Hochberg correction.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Histology confirmed collagen-enriched PF-associated pathways within subendocardial tissue and false tendons. Optical density-based segmentation reliably differentiated tissue components with low inter-section variability. Collagen-rich PF-associated regions showed significantly higher\n T<\/jats:italic>\n RAFF<\/jats:sub>\n ,\n T<\/jats:italic>\n 1\u03c1<\/jats:sub>\n ,\n T<\/jats:italic>\n 2<\/jats:sub>\n , and\n T<\/jats:italic>\n 1<\/jats:sub>\n values compared with remote myocardium. RRTD analysis indicated that\n T<\/jats:italic>\n RAFF<\/jats:sub>\n and\n T<\/jats:italic>\n 1\u03c1<\/jats:sub>\n provided the strongest relative contrast among the evaluated parameters.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n Histology-validated qMRI enables characterization of collagen-rich PF-associated pathways in the\n ex vivo<\/jats:italic>\n porcine heart. These findings demonstrate the sensitivity of relaxation-based MRI techniques to collagen-rich PF-associated pathways and support further investigation of cardiac conduction system imaging.\n <\/jats:p>\n <\/jats:sec>\n \n Key points<\/jats:title>\n \n \n \n \n \n Question<\/jats:italic>\n <\/jats:bold>\n Noninvasive MRI characterization of collagen-rich PF-associated pathways remains challenging because these small conduction structures are difficult to identify.\n <\/jats:p>\n <\/jats:list-item>\n \n \n \n Findings<\/jats:italic>\n <\/jats:bold>\n Histology-referenced MRI differentiated collagen-rich PF-associated pathways from those of the remote myocardium, with rotating-frame relaxation methods providing the strongest contrast.\n <\/jats:p>\n <\/jats:list-item>\n \n \n \n Relevance statement<\/jats:italic>\n <\/jats:bold>\n qMRI relaxation mapping enables histology-validated characterization of collagen-rich PF-associated pathways, supporting the development of noninvasive imaging approaches for studying cardiac conduction system microstructure.\n <\/jats:p>\n <\/jats:list-item>\n <\/jats:list>\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1186\/s41747-026-00793-0","type":"journal-article","created":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T14:36:23Z","timestamp":1789482983000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Histology-validated quantitative MRI characterization of collagen-rich Purkinje fiber-associated pathways in the ex vivo porcine heart"],"prefix":"10.1186","volume":"10","author":[{"given":"Yi","family":"Li","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Victor","family":"Casula","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manu","family":"Pradeep","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7472-9900","authenticated-orcid":false,"given":"Timo","family":"Liimatainen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,9,15]]},"reference":[{"key":"793_CR1","doi-asserted-by":"publisher","first-page":"99","DOI":"10.1002\/ca.20700","volume":"22","author":"RH Anderson","year":"2009","unstructured":"Anderson RH, Yanni J, Boyett MR et al (2009) The anatomy of the cardiac conduction system. 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