{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,3]],"date-time":"2026-03-03T06:52:17Z","timestamp":1772520737654,"version":"3.50.1"},"reference-count":24,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,2,25]],"date-time":"2026-02-25T00:00:00Z","timestamp":1771977600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Assessing human embryo quality is a critical step in in vitro fertilization (IVF), yet traditional manual grading remains subjective and physically limited by the shallow depth-of-field in conventional microscopy. This study develops a novel \u201csoft optical sensor\u201d architecture that transforms standard optical microscopy into an automated, high-precision instrument for embryo quality assessment. The proposed system integrates two key computational innovations: (1) a multi-focal image fusion module that reconstructs lost morphological details from Z-stack focal planes, effectively creating a 3D-aware representation from 2D inputs; and (2) a retrieval-augmented generation (RAG) framework coupled with a Swin Transformer to provide both high-accuracy classification and explainable clinical rationales. Validated on a large-scale clinical dataset of 102,308 images (prior to augmentation), the system achieves a diagnostic accuracy of 94.11%. This performance surpasses standard single-plane analysis methods by 9.43%, demonstrating the critical importance of fusing multi-focal data. Furthermore, the RAG module successfully grounds model predictions in standard ESHRE consensus guidelines, generating natural language explanations. The results demonstrate that this soft sensor approach significantly reduces inter-observer variability and offers a robust tool for standardized morphological assessment, though prospective validation against live birth outcomes remains essential for clinical adoption.<\/jats:p>","DOI":"10.3390\/s26051441","type":"journal-article","created":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T09:31:32Z","timestamp":1772098292000},"page":"1441","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Soft Optical Sensor for Embryo Quality Evaluation Based on Multi-Focal Image Fusion and RAG-Enhanced Vision Transformers"],"prefix":"10.3390","volume":"26","author":[{"given":"Domas","family":"Jonaitis","sequence":"first","affiliation":[{"name":"Automation Department, Kaunas University of Technology, 51367 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vidas","family":"Raudonis","sequence":"additional","affiliation":[{"name":"Automation Department, Kaunas University of Technology, 51367 Kaunas, Lithuania"},{"name":"SustAInLivWork Center of Excellence, Kaunas University of Technology, 51367 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Egle","family":"Drejeriene","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology, Lithuanian University of Health Sciences, 51367 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-2114-1126","authenticated-orcid":false,"given":"Agne","family":"Kozlovskaja-Gumbriene","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynaecology, Lithuanian University of Health Sciences, 51367 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1251-8160","authenticated-orcid":false,"given":"Andres","family":"Salumets","sequence":"additional","affiliation":[{"name":"Celvia CC AS, 50411 Tartu, Estonia"},{"name":"Institute of Clinical Medicine, Department of Obstetrics and Gynecology, Tartu University, 50406 Tartu, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,25]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2023). 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