{"id":"56332952-00b8-4e49-9139-bce69c413463","arxiv_id":"2412.14047","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":0,"one_line_summary":"A single microscope setup adds full-field OCT to a light-sheet fluorescence microscope, letting it capture co-registered fluorescence and structural images in living zebrafish.","lead":"Researchers combined two microscope techniques, light sheet fluorescence and full-field optical coherence tomography, so one instrument gives both labeled fluorescence and label-free structural images of living zebrafish. The two modes share the same camera path, which makes aligning the two image types straightforward.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Two-phase FF-OCT retrieves A cos(phi0), not |A|; without a phase-robustness check, the structural images could contain phase-dependent artifacts that undermine the claimed anatomical context.","rationale":"The central claim is a working combined system producing co-registered fluorescence and structure; the most load-bearing condition is that the FF-OCT channel yields faithful structural contrast. The 2-phase scheme is the least secure part of that chain, and the manuscript itself flags it in Section 2.2. The reader's weakest assumption hits exactly this point, so I agree. I do not think the paper should be rejected: the resolution measurements are plausible, the expected anatomy is visible, and the authors are transparent about the 2-phase limitation. The missing piece is a quantitative demonstration that A cos(phi0) is not phase-dominated. The proposed PZT/4-phase experiment settles it directly, so the appropriate disposition remains conditional on that check. Other concerns (co-registration accuracy, shared data) are secondary because a shared detection path makes pixel registration nearly automatic and the lack of code does not invalidate the instrument claim.","tokens_in":7650,"tokens_out":6288,"duration_ms":62468,"concrete_test":"Mount a PZT on the reference mirror and, on the same zebrafish trunk plane as Fig. 4(a), acquire 2-phase and 4-phase FF-OCT data at the same reference position. Reconstruct amplitude A(x,y) and phase phi0 from the 4-phase data, then compute the 2-phase output B = A cos(phi0). Report the fraction of pixels in the spinal cord/notochord/muscle regions where sign(B) differs from sign(A) or |B| < 0.1 A. If this fraction is substantial (e.g., >5%), the 2-phase images are phase-contaminated; if it is negligible, the 'sufficient' claim is supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 2.2 is the load-bearing point. The implementation uses 2-phase shifting: the retrieved image is (I(phi0) - I(phi0+pi))/2 = A(x,y) cos(phi0). The authors acknowledge this cannot decouple amplitude and phase, yet assert it is 'sufficient for retrieving 2D structural information.' This assertion is exactly what the central claim depends on: the FF-OCT images are presented as structural context co-registered with SPIM. In FF-OCT, phi0 is the sub-wavelength optical path difference between reference and sample at each pixel; for a tissue volume it varies laterally with surface tilt and internal scatterer distribution. Where cos(phi0) is near zero or negative, a true backscattering structure will be suppressed or sign-inverted; conversely, phase can create apparent contrast. Without a quantitative comparison to an N>=3 phase-shifting reconstruction or to phase-cycled 2-phase acquisitions, the structural images in Figs. 3-5 could contain phase artifacts rather than pure reflectivity. The visible anatomy is reassuring, but it does not establish that the 2-phase approximation is reliable across the FOV. This is a correctness risk for the main functional claim, not merely a stylistic concern.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents a combined selective plane illumination microscopy (SPIM) and full-field optical coherence tomography (FF-OCT) system that shares a single detection path, allowing co-registered fluorescence and label-free structural imaging without sample rotation or complex reconstruction. The SPIM arm uses a standard light-sheet configuration with a 20× detection objective, while the FF-OCT arm uses a 565 nm LED with a 104 nm bandwidth and a 2-phase shifting algorithm. The authors characterize lateral resolution (0.75 µm), SPIM axial resolution (4.07 µm), and FF-OCT axial resolution (2.0 µm in air, 1.5 µm in water), and demonstrate the system on live zebrafish larvae at 2 dpf and 4 dpf, showing optical sectioning and anatomical context (spinal cord, notochord, muscle, finfold) with fluorescence labels of neurons.","tokens_in":7915,"tokens_out":3087,"duration_ms":28803,"significance":"If the technical claims hold, the system offers a practical way to add structural context to SPIM without the sample rotation and computational reconstruction required by optical tomography or multi-view bright-field methods, and with better lateral resolution than swept-source OCT implementations. The shared detection path is an elegant design that makes co-registration conceptually straightforward. The in vivo zebrafish images illustrate the value of combining fluorescence with label-free structural information. The paper is a proof-of-principle, not a full quantitative validation; its main weaknesses are the reliance on a 2-phase FF-OCT algorithm without phase-robustness evidence, and the absence of quantitative co-registration verification and measurement statistics.","major_comments":[{"comment":"The 2-phase shifting method retrieves (I(x,y,φ0) − I(x,y,φ0+π))/2 = A(x,y) cos φ0, which depends on the sub-wavelength phase φ0. The paper asserts this is 'sufficient for retrieving 2D structural information,' but provides no quantitative validation. Because φ0 varies across the field of view due to surface tilt and internal scatterer distribution, regions with cos φ0 near zero or negative could suppress or invert true backscattering contrast, producing phase-dependent artifacts. To support the central claim that FF-OCT provides reliable structural context, please compare the 2-phase result with a standard N≥3 phase-shifting algorithm on the same sample, or acquire 2-phase images at multiple phase offsets and show that the structural features are consistent.","section":"§2.2"},{"comment":"The claim of 'seamless and efficient co-registration' through the shared detection path is plausible but not quantified. No measurement of registration accuracy (e.g., a target with features visible in both SPIM and FF-OCT, or a distortion assessment) is provided. Since SPIM and FF-OCT use different illumination arms and the sample is scanned axially, residual misalignment or chromatic effects could degrade the overlay shown in Figs. 3–5. Please report a co-registration error metric (in pixels or µm) for a test target, and state whether the overlay in the figure panels is obtained by a simple global shift or by an affine/warping transform.","section":"§2.1, §2.2, §3.2"},{"comment":"The resolution values are reported without error bars or replicate counts. The lateral resolution is the FWHM of a single 0.5 µm bead (Fig. 2a), the SPIM axial resolution is from one beam-waist scan (Fig. 2b), and the FF-OCT axial resolution is from one autocorrelation fit (Fig. 2c). Given fitting uncertainty and pixelation, a single measurement is insufficient to claim these as system resolutions. Please provide N, mean, and standard deviation for each measurement, and specify the fitting procedure (e.g., Gaussian fit) and the number of beads or scans used.","section":"§3.1"},{"comment":"The FF-OCT images in Fig. 3a show saturated, uninformative regions in highly pigmented areas (white arrows). The paper acknowledges this as a camera limitation, but it affects the in vivo demonstration: the anatomical context is missing exactly where the sample is most opaque, which is a relevant scenario for biological imaging. If the goal is to demonstrate structural context in live zebrafish, this limitation should be addressed or at least systematically characterized (e.g., dynamic range, percentage of saturated pixels). The discussion of future camera upgrades is reasonable, but a quantitative statement of the current limitation would strengthen the paper.","section":"§3.2"}],"minor_comments":[{"comment":"The mathematical expression for the 2-phase result is missing parentheses and is not explicitly numbered. Please number the equation and write it as (I(x,y,φ0) − I(x,y,φ0+π))/2 = A(x,y) cos φ0, and define A(x,y) and φ0 in the text.","section":"§2.2"},{"comment":"The claim that the measured 0.75 µm lateral resolution applies to both SPIM and FF-OCT because the fluorescence emission wavelength (≈520 nm) is close to the LED center wavelength (565 nm) is reasonable for a diffraction-limited system, but it assumes the same effective NA in both modalities. Please state the detection NA and the expected diffraction-limited spot size explicitly.","section":"§3.1"},{"comment":"The field of view is given as 244.8 µm × 183.6 µm for a 1440×1080 camera, but the scale bar in Fig. 3(d) is labeled 50 µm. Please verify that the scale bar and the stated FOV are consistent, and specify the pixel size used in the calculations.","section":"§3.2"},{"comment":"The sentence 'the retrieved 2D image at a certain depth (I(x,y,φ0)−I(x,y,φ0+π))/2 is a contribution of amplitude and phase' is grammatically awkward. Please rewrite for clarity.","section":"§2.2"},{"comment":"The abstract and introduction state that the system is built 'without requiring modifications to the existing SPIM setup,' but adding the FF-OCT reference arm and beamsplitter does require optical access. Please clarify that the SPIM illumination and detection paths remain unchanged, while FF-OCT components are added externally.","section":"§1"}],"recommendation":"major_revision","confidential_remarks":"The paper fits the scope of the journal and presents a useful proof-of-principle. The main technical risk is the 2-phase FF-OCT reconstruction, which the authors acknowledge but do not validate; this is an appropriate topic for a major revision. The requested experiments (phase-robustness check, co-registration error, replicate measurements) are all feasible within the reported setup and would substantially strengthen the claims."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Right off the bat: this is a solid, useful instrument paper. The specific combination—time-domain FF-OCT bolted onto a SPIM with a shared detection path—is not in the prior art they cite, and the in vivo zebrafish data show it works well enough to see spinal cord, notochord, and muscle alongside GFP-labeled neurons. The resolution numbers are credible (0.75 µm lateral, 4.07 µm SPIM axial, 1.5 µm FF-OCT axial in water), and the authors are honest about the current camera limits and the need for heavy averaging.\n\nThe main soft spot is the one they acknowledge in Section 2.2: the 2-phase shifting method recovers A(x,y) cos(phi0), not the amplitude, so phase can suppress or invert real reflectivity contrast. They assert it is 'sufficient for retrieving 2D structural information' without a quantitative check against a 3- or 4-phase reconstruction. The anatomical images are reassuring, but they don't demonstrate that the contrast is free of phase artifacts across the FOV. A revision should include at least a comparison on a test target or a phase-cycled acquisition. This is a genuine caveat, not a reason to reject.\n\nOther soft spots are minor: co-registration accuracy is not quantified, no error bars on the resolution measurements, and the claim that no modification to the SPIM setup is required is a bit of an overstatement—they added a beamsplitter, reference arm, and flippable filter. Also, data and code are not shared.\n\nOverall, this is a practical integration that a microscopy lab could reproduce and build on. It deserves serious peer review, and the 2-phase issue should be addressed. I'd take it to a reading group if multimodal imaging is on the agenda.","headline":"Credible SPIM+FF-OCT integration with a real but fixable 2-phase phase-artifact caveat.","tokens_in":8381,"tokens_out":1981,"would_cite":true,"duration_ms":18177,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"By sharing one detection path, SPIM and FF-OCT produce co-registered fluorescence and anatomical images in live zebrafish.","keywords":["selective plane illumination microscopy","full-field optical coherence tomography","multimodal imaging","in vivo imaging","co-registration","optical sectioning","zebrafish larvae","label-free structural imaging"],"falsifier":"Image the same zebrafish trunk plane with the current two-step FF-OCT protocol and with a three-step or five-step phase-shifting protocol; if structures such as thin muscle septa or notochord boundaries appear in the higher-order retrieval but are absent or contrast-inverted in the two-step image, the assumption that $A(x,y)\\cos\\varphi_0$ suffices is disproven.","tokens_in":7483,"feed_emoji":"🔬","tokens_out":10778,"duration_ms":88460,"temperature":0.7,"pith_summary":"This paper shows how to add label-free structural imaging to a light-sheet fluorescence microscope by integrating full-field optical coherence tomography (FF-OCT) into the same detection path. Because SPIM and FF-OCT share the detection objective, tube lens, and camera, the fluorescence and structural images are naturally co-registered, and no sample rotation or tomographic reconstruction is required. The authors report a lateral resolution of about 0.75 µm for both channels, a SPIM axial resolution of about 4.07 µm, and an FF-OCT axial resolution of about 1.5 µm in water, then demonstrate the system on live zebrafish larvae. The central claim is that existing SPIM setups can gain a high-resolution anatomical context channel simply and at low cost.","feed_headline":"One shared path captures fluorescence and structure in live zebrafish","feed_subtitle":"The same optics image fluorescent neurons and surrounding tissue in live larvae, no rotation or reconstruction needed.","key_machinery":"The key mechanism is the shared detection path: a single 20× objective, tube lens, and CMOS camera serve both modalities, with only a flippable quadband emission filter switched in for SPIM. FF-OCT is implemented as an epi-Köhler low-coherence interferometer using a 565 nm, 104 nm bandwidth LED; a non-polarizing beamsplitter divides the light between the sample arm and a reference arm that contains a matched objective and an OD 6.0 mirror, and the depth-resolved structural image is recovered from two phase-shifted frames via $\\frac{I(x,y,\\varphi_0)-I(x,y,\\varphi_0+\\pi)}{2}=A(x,y)\\cos\\varphi_0$. The short coherence length of the LED is what gives FF-OCT its ~1.5 µm axial sectioning in water, and because these optics are added on the illumination side, the SPIM arrangement itself is unchanged.","core_discovery":"Using live zebrafish larvae carrying GFP-labeled neurons, the combined SPIM-FF-OCT system captures fluorescence images and label-free structural images from the same plane, allowing spinal cord, notochord, muscle, and median finfold to be distinguished in the structural channel while the fluorescent channel shows the neuronal pattern. The structural channel is produced by time-domain FF-OCT with a 565 nm LED and a two-phase-shifting interferometric retrieval, and the shared detection path makes the two image types registered by construction. The reported resolutions are 0.75 µm lateral (set by the fluorescent beads for both modalities), a 4.07 µm light-sheet waist for SPIM axial sectioning, and a 2.0 µm coherence envelope for FF-OCT in air, corresponding to 1.5 µm in water. Depth scans with 5-10 µm intervals show that both channels section through the larval trunk, with structural features changing from the finfold to the notochord.","pith_inferences":["The two-step structural retrieval leaves the image proportional to the backscattered amplitude times the cosine of the phase; structures whose phase is near a zero crossing could drop out, so a three-step or five-step phase protocol would test whether the current channel is missing tissue boundaries.","Because the mount needs no sample rotation, the same larva could be imaged repeatedly over hours without re-registration; this follows from the design even though the paper does not claim it.","The shared detection path means camera upgrades improve both channels together, so field of view, bit depth, and signal-to-noise ratio will scale simultaneously as the hardware evolves.","The authors' proposed dynamic FF-OCT extension is directly testable on this setup, since the low-coherence LED and the absence of beam steering already provide the illumination conditions needed for motility-based contrast."],"forward_implications":["Any existing SPIM system can gain a label-free structural channel by adding the FF-OCT illumination and reference arm, with no change to the established light-sheet detection path.","Fluorescence and structural images are co-registered by construction, removing the need for computational alignment when linking labeled cells to surrounding anatomy.","The FF-OCT channel's sub-2 µm axial resolution distinguishes tissue layers such as spinal cord, notochord, and muscle in live zebrafish, providing anatomical context for fluorescence.","Upgrading the camera to a higher bit-depth, cooled CMOS would shorten acquisition by an estimated factor of 2-3 and, with image stitching, make whole-body time-lapse imaging practical.","Integrating dynamic FF-OCT analysis into the same shared path could add subcellular structural contrast based on intracellular motility and metabolic activity."],"supporting_citations":[{"why":"Introduces SPIM as a low-phototoxicity optical-sectioning method for live embryos, the base modality the combined system extends.","marker":"[1]"},{"why":"Describes optical tomography, a structural complement to SPIM that requires spiral sample rotation and back-projection reconstruction, which this system avoids.","marker":"[7]"},{"why":"Describes three-dimensional bright-field microscopy, another multi-angle reconstruction approach that motivates a simpler no-rotation structural channel.","marker":"[8]"},{"why":"Reports a prior SPIM plus swept-source OCT combination whose lateral resolution is about 14.9 µm and requires swept-source hardware, the comparison this system improves on.","marker":"[9]"},{"why":"Supplies the FF-OCT technique and its dynamic multimodal variant that are integrated into the SPIM detection path.","marker":"[10,11]"},{"why":"Provides the open-access light-sheet microscope optics used to build the SPIM illumination and shared detection path.","marker":"[12,13]"},{"why":"Defines the transgenic zebrafish line with GFP-labeled neurons used for the in vivo demonstration of co-registered imaging.","marker":"[17]"}],"fun_headline_variants":["SPIM and FF-OCT join forces for live zebrafish imaging","Same optics, two views: fluorescence and structure in vivo","Multimodal imaging: light sheet plus OCT on one path","No modifications: SPIM gains structural imaging via FF-OCT","Live zebrafish: fluorescence and anatomy from one shared path"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The weakest point is the two-step phase-shifting retrieval for FF-OCT, which leaves the structural image proportional to a product of the backscattered amplitude and the cosine of its phase; the paper assumes this mixed quantity is still enough to reveal the anatomy.","fun_headline_variants_meta":{"raw":{"variants":["SPIM and FF-OCT join forces for live zebrafish imaging","Same optics, two views: fluorescence and structure in vivo","Multimodal imaging: light sheet plus OCT on one path","No modifications: SPIM gains structural imaging via FF-OCT","Live zebrafish: fluorescence and anatomy from one shared path"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000421,"raw_usage":{"total_tokens":2120,"prompt_tokens":859,"completion_tokens":1261,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":475,"completion_tokens_details":{"reasoning_tokens":1178}},"tokens_in":475,"tokens_out":1261,"duration_ms":8256,"temperature":1.0,"reasoning_tokens":1178,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T12:31:15.330825+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Image the same zebrafish trunk plane with the current two-step FF-OCT protocol and with a three-step or five-step phase-shifting protocol; if structures such as thin muscle septa or notochord boundaries appear in the higher-order retrieval but are absent or contrast-inverted in the two-step image, the assumption that $A(x,y)\\cos\\varphi_0$ suffices is disproven.","supporting_citations":[{"cited_title":"Optical tomography complements light sheet microscopy for in toto imaging of zebrafish development,","cited_arxiv_id":null,"evidence_quote":"Describes optical tomography, a structural complement to SPIM that requires spiral sample rotation and back-projection reconstruction, which this system avoids."},{"cited_title":"Optical Sectioning Deep Inside Live Embryos by Selective Plane Illumination Microscopy,","cited_arxiv_id":null,"evidence_quote":"Introduces SPIM as a low-phototoxicity optical-sectioning method for live embryos, the base modality the combined system extends."},{"cited_title":"Three-dimensional bright-field microscopy with isotropic resolution based on multi-view acquisition and image fusion reconstruction,","cited_arxiv_id":null,"evidence_quote":"Describes three-dimensional bright-field microscopy, another multi-angle reconstruction approach that motivates a simpler no-rotation structural channel."},{"cited_title":"Multimodal high-resolution embryonic imaging with light sheet fluorescence microscopy and optical coherence tomography,","cited_arxiv_id":null,"evidence_quote":"Reports a prior SPIM plus swept-source OCT combination whose lateral resolution is about 14.9 µm and requires swept-source hardware, the comparison this system improves on."},{"cited_title":"Small leucine-rich proteoglycans inhibit CNS regeneration by modifying the structural and mechanical properties of the lesion environment,","cited_arxiv_id":null,"evidence_quote":"Defines the transgenic zebrafish line with GFP-labeled neurons used for the in vivo demonstration of co-registered imaging."}],"review_version":1}