The Spectros T-Stat™ 303 Microvascular Tissue Oximeter is intended for use as an adjunct monitor of the localized hemoglobin oxygen saturation of blood in the microvascular tissue spaces (StO2%) in infants, children, or adults at risk for reduced-flow and no-flow ischemic states. The prospective clinical value of measurements made with the T-Stat™ Oximeter has not been demonstrated in disease states. The T-Stat™ Oximeter should not be used as the sole basis for diagnosis or therapy.
Device Story
T-Stat™ 303 is a broadband, multiwavelength Visible Light Spectroscopy (VLS) monitoring system. Input: reflected visible light captured from tissue via disposable sensor probe. Operation: system illuminates tissue with LED light; reflected light returned to monitor; StO2% calculated using differential optical diffuse reflectance spectroscopy and fitting for background scattering. Output: real-time StO2% and relative hemoglobin values displayed on monitor. Used in clinical settings by healthcare providers to monitor microvascular tissue oxygenation. Provides adjunct data for assessing tissue perfusion; helps identify reduced-flow or no-flow ischemic states. Benefits patient by providing localized oxygenation status to assist clinical decision-making.
Clinical Evidence
Bench testing and peer-reviewed animal/human studies. In vitro: accurately measured hemoglobin spectra and desaturation binding curves. In vivo: VLS StO2% unbiased compared to NIRS (Bias -1% ± 5%, p=N.S.); VLS demonstrated tighter normal ranges (62-75% vs 48-88%, p<0.001). Sensitive to reduced-flow and no-flow ischemic states (p<0.001).
Technological Characteristics
Broadband VLS monitoring system. Uses non-laser LED light source. Disposable sensor probe with detachable monitor connection. Measures 2,048 wavelengths. Principle: diffuse reflectance spectroscopy. Software-driven electronic monitor for data collection, analysis, and display. Class II device.
Indications for Use
Indicated for infants, children, and adults at risk for reduced-flow and no-flow ischemic states to monitor localized microvascular hemoglobin oxygen saturation (StO2%). Not for use as sole basis for diagnosis or therapy.
Regulatory Classification
Identification
An oximeter is a device used to transmit radiation at a known wavelength(s) through blood and to measure the blood oxygen saturation based on the amount of reflected or scattered radiation. It may be used alone or in conjunction with a fiberoptic oximeter catheter.
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# Spectros Corporation
NOV - 5 2004 4370 Alpine Road #108, Portola Valley CA 94028-7927 Phone 650.851.4040 Fax 650.851.4099
> David A. Benaron, M.D. e-mail: dbenaron@spectros.com
# Section 40 - 510(k) Summary
[This section supersedes and replaces Section 29 of the Application]
# I. Applicant Information
| A. Date of Summary: | October 28, 2004 |
|----------------------|-------------------------------------------------------------------------------------------------------------------------------|
| B. Manufacturer | Spectros Corporation<br>4370 Alpine Road, Suite 108<br>Portola Valley CA 94028 |
| C. Official Contact: | David A. Benaron, MD<br>CEO and President<br>Spectros Corporation<br>Suite 108<br>4370 Alpine Road<br>Portola Valley CA 94028 |
| D. Contact Info: | Phone: (650) 851-4040<br>Fax: (650) 851-4099<br>E-mail: dbenaron@spectros.com |
### II. Device Information
- A. Proprietary Name: T-Stat™ 303 Microvascular Tissue Oximeter B. Common Name: Tissue Oximeter C. Classification Name: Oximeter, Tissue (870.2700) D. Product Code: MUD E. Regulatory Class: Class II F. Panel: Cardiovascular
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### III. Predicate Devices
The following devices are cited as predicates:
#### Exhibit 40-1 Predicate Tissue Oximeter Devices Summaries
| # | Predicate Feature | Manufacturer | Device | K-Number |
|----|----------------------|--------------|-------------------------------|----------|
| 1. | Tissue Oximeter | Hutchinson | InSpectra 325 | K023938 |
| 2. | Tissue Oximeter | Somanetics | Invos 5100 | K001842 |
| 3. | Relative Hemoglobin | Nellcor | N-395 | K991823 |
| 4. | Site-Specific: Oral | Olympus | XENF-DP | K011869 |
| 5. | Site-Specific: Colon | Olympus | LF-DP | K002231 |
| 6. | Site-Specific: Endo | Olympus | Thoracoscope /<br>Laparoscope | K915857 |
### IV. General Description
The Spectros T-Stat™ 303 Tissue Oximeter is a broadband, multiwavelength, Visible Light Spectroscopy (VLS) monitoring system for measuring the saturation of hemoglobin with oxygen in the microvascular tissue spaces (StQ2%).
The complete system consists of a disposable sensor probe connected to a software-driven electronic monitor. Data collection, analysis, and display functions are provided by the monitor. Illumination of the tissue is provided by a visible light source in the sensor probe placed near, on, or into the target tissue to be studied. Reflected light is captured and returned to the monitor via a detachable connection at the monitor end of the patient probe. StO2% is estimated using differential optical diffuse reflectance spectroscopy and fitting for background scattering over a range of reflected visible wavelengths.
#### V. Indications
The Spectros T-Stat™ 303 Microvascular Tissue Oximeter is intended for use as an adjunct monitor of the localized hemoglobin oxygen saturation of blood in the microvascular tissue spaces (StO2%) in infants, children, or adults at risk for reduced-flow and no-flow ischemic states.
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The prospective clinical value of measurements made with the T-Stat™ Oximeter has not been demonstrated in disease states. The T-Stat™ Oximeter should not be used as the sole basis for diagnosis or therapy.
KO40684
6.315
# VI. In Vitro and In Vivo Test Data
In studies of T-StatTM:
- T-Stat™ accurately measured hemoglobin spectra and desaturation binding curves in peer-reviewed in vitro studies.
- T-Stat™ StO2% determined using VLS was unbiased in comparison to StO2% determined using NIRS predicates (StO2% Bias = - 1% ± 5%, p=N.S.), but VLS demonstrated significantly tighter ranges of normal in peer-reviewed animal and human studies (VLS normal range 62-75% vs. NIRS reported at 48-88%, p<0.001).
- T-Stat™ VLS tissue oximetry was demonstrated sensitive to reduced-flow and no-flow ischemic states in peer-reviewed animal and human studies (p<0.001).
- T-Stat™ VLS tissue oximetry provides readings in low and no flow -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------ischemic states in human clinical studies.
### VI. Comparison to Predicate Devices
#### A. Similarities
Both T-Stat™ and the predicate tissue oximeters:
- Use the same fundamental optical operating principle, called diffuse । reflectance spectroscopy.
- Use light from an LED to probe a cross-section of the microvasculature of tissue (arterioles, capillaries, and venuole).
- -Analyze light returning from tissue, after having passed through the tissue, for hemoglobin in its oxygenated and deoxygenated forms in the optically sampled region.
- -Calculate StO2%, a value reflecting the percentage saturation of hemoglobin with oxygen in the microvascular capillary spaces
Both T-Stat™ and the predicate pulse oximeters:
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Use the same fundamental optical operating principle, called diffuse reflectance spectroscopy.
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- -Analyze light returning from tissue, after having passed through the tissue. for hemoglobin in its oxygenated and deoxygenated forms in the optically sampled region.
- | Calculate and display a relative hemoglobin value used for assessment of device functionality, proper probe placement, and system operation.
Both the T-Stat™ and the endoscope predicates:
- Emit visible light into the tissues and detect a portion of the light backscattered from tissues in the oral cavity, colon, endoscopic procedures.
- । Use low power light that does not adversely influence the physiology of the target tissue.
#### B. Differences
—
T-Stat™ and the predicate Tissue Oximeters differ in the following nonsignificant ways:
- 2048 vs. 4 Wavelengths: T-Stat™ measures light at 2,048 wavelengths; the । predicate devices use 4 or fewer wavelengths. An increase in the number of wavelengths used increases the robustness of the matrix solutions by which StO2% is calculated. This is because the solution becomes statistically overdetermined at such large wavelength counts (number of measurements is very much greater than the number of unknowns in the equation).
- VLS US NIRS: T-Stat™ uses only visible light (VLS); the predicates use ו both visible and near-infrared light (NIRS). Both methods involve diffuse reflectance spectroscopy; only the wavelength range has changed. Laboratory and clinical values are not changed by the adoption of VLS in favor of NIRS; In vivo, mean VLS StO2% was unbiased compared to NIRS.
- -Laser us, Non-Laser LED: T-Stat™ uses a non-laser LED; the predicates use laser LED's. LED choice does not affect the underlying technology of the measurement. The energies emitted by the T-Stat™ non-laser LED and the predicate laser LED's are comparable.
T-Stat™ and the predicate pulse oximeter differ in the following non-significant ways:
- Tissue Oximetry: Pulse oximeters estimate arterial saturation, rather than | tissue hemoglobin saturation; however, the predicate for tissue oximetry is
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other tissue oximeters, not pulse oximetry, and therefore this difference is not significant.
T-Stat™ and the predicate endoscopes differ in the following non-significant ways:
- -Analysis: Endoscopes typically do not provide spectral analysis; however, the predicate for spectroscopic analysis for hemoglobin saturation is tissue and pulse oximetry, not endoscopy, and therefore this difference is not significant.
- C. Result of Comparison
The Spectros T-Stat™ 303 Microvascular Tissue Oximeter is substantially equivalent to the predicate devices.
> File Source and Version: T-Stat 510(k) Ch 40 -- Summary (Rev 04.10.28a).doc
## [End of Section 40]
[Remainder of This Page Blank]
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Image /page/5/Picture/1 description: The image shows the seal of the Department of Health & Human Services (HHS) of the United States. The seal features a stylized eagle with three lines forming its body and wings, symbolizing health, hope, and well-being. The words "DEPARTMENT OF HEALTH & HUMAN SERVICES - USA" are arranged in a circular pattern around the eagle.
Food and Drug Administration 9200 Corporate Boulevard Rockville MD 20850
NOV - 5 2004
Spectros Corporation c/o David A. Benaron, M.D. CEO & President 4370 Alpine Road, Suite 108 Portola Valley, CA 94028
Re: K040684
K04064
Trade Name: Spectros T-Stat™ 303 Microvascular Tissue Oximeter Regulation Number: 21 CFR 870.2700 Regulation Name: Oximeter Regulatory Class: Class II (two) Product Code: MUD Dated: July 30, 2004 Received: August 9, 2004
Dear Dr. Benaron:
We have reviewed your Section 510(k) premarket notification of intent to market the indication We have reviewed your Section 510(x) prematic is substantially equivalent (for the indications
referenced above and have determined the device is substantially interstate referenced above and have determined the devices marketed in interstate for use stated in the enclosure) to legally manced product and Device Amendments, or to
commerce prior to May 28, 1976, the enactment date of the Federal Food. Drug commerce prior to May 28, 1970, the chactinence with the provisions of the Federal Food. Drug, devices that have been reclassified in accordance while approval application (PMA).
and Cosmetic Act (Act) that do not require approval as provisions of the Act The and Cosmetic Act (Act) that do not require upprovine spension provisions of the Act. The Act. The Act. The You may, therefore, market the device, subject to the genirents for annual registration, listing of
general controls provisions of the Act include required misbranding and general controls provisions of the 7tet merade requirements of the management misbranding and adulteration.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it If your device is classified (see above) mis class a control states on the news can a may be subject to such additional controlis. Existing may on 898. In addition, FDA may
be found in the Code of Federal Regulations, Title 21, Parts 800 to 898 In addition be lound in the Code of I ederal Regarders on the Federal Register.
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Page 2 - Dr. David Benaron
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050. This letter will allow you to begin marketing your device as described in your Section 510(k) premarket notification. The FDA finding of substantial equivalence of your device to a legally marketed predicate device results in a classification for your device and thus, permits your device to proceed to the market.
If you desire specific advice for your device on our labeling regulation (21 CFR Part 801), please contact the Office of Compliance at (301) 594-4648. Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21CFR Part 807.97). You may obtain other general information on your responsibilities under the Act from the Division of Small Manufacturers, International and Consumer Assistance at its toll-free number (800) 638-2041 or (301) 443-6597 or at its Internet address http://www.fda.gov/cdrh/dsma/dsmamain.html
Sincerely yours,
Bhimmar for
Bram D. Zuckerman, M.D. Director Division of Cardiovascular Devices Office of Device Evaluation Center for Devices and Radiological Health
Enclosure
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# Indications for Use
510(k) Number (if known): K 040684
Device Name: Spectros T-Stat™ 303 Microvascular Tissue Oximeter
Indications For Use: Spectros T-Stat™ 303 Microvascular The Tissue Oximeter is intended for use as an adjunct monitor of the localized hemoglobin oxygen saturation of blood in the microvascular tissue spaces (StO2%) in infants, children, or adults at risk for reduced-flow and no-flow ischemic states.
> The prospective clinical value of measurements made with the T-Stat™ Oximeter has not been demonstrated in disease states. The T-Stat™ Oximeter should not be used as the sole basis for diagnosis or therapy.
Prescription Use XXX (Part 21 CFR 801 Subpart D) AND/OR
Over-The-Counter Use (21 CFR 807 Subpart C)
(PLEASE DO NOT WRITE BELOW THIS LINE-CONTINUE ON ANOTHER PAGE IF NEEDED)
Concurrence of CDRH, Office of Device Evaluation (ODE)
Bhimlame
(Division Sign-Off) Division of Cardiovascular Devices neloux 4 510(k) Number
Page 1 of 1
Two short videos show you everything — or skip straight to the written tutorial if you'd rather read. You can reopen this any time from the Tutorial button in the top bar.
Part 1 — Search, results, and everyday workflows 16 min
Part 2 — Embeddings: the galaxy map 3 min
1. Search: exact and fuzzy
Type a phrase like "coronary artery calcification" into the search box. You get two kinds of results. Exact results match the literal phrase — prefix searches work ("coronary artery calcificati") but suffix searches do not. Fuzzy results match on the meaning and intent of your phrase rather than the exact words, and are sorted by relevance score. Hover over the Exact or Fuzzy badge on any row to see exactly why it matched.
Use the checkboxes above the results to narrow: SaMD keeps only software-only devices, AI / ML keeps only devices with AI.
Exact vs. fuzzy search: what's the difference?
Exact matches on the literal phrase (prefix search works, suffix does not). Fuzzy matches on the meaning and intent of the phrase rather than the exact words. Hover over the badge on any row to see why it matched.
You search "coronary artery calcification" and want only software devices with AI. What two filters do you apply?
Narrow by SaMD (software-only devices), then narrow by AI/ML (devices with AI).
2. The results table
Scroll right in the results table. The intended use is extracted for you — no need to open the PDF. The device story gives a high-level snapshot of what the device does and how it's used. The AI Performance sub-table shows each output name, acceptance criteria, observed values, and development/test dataset descriptions — the same format Innolitics uses for regulatory strategy outputs, and the fastest high-level fingerprint of an AI device. It is AI-generated but has been very reliable in practice.
Where do you find a device's intended use without opening the PDF?
Scroll right in the search results table. The intended use column is extracted for you; no need to dig into the 510(k) summary PDF.
What does the AI Performance sub-table show, and why is it useful?
Output name, acceptance criteria, observed values, development dataset description, and test dataset description. It's the same format we use for regulatory strategy output and Fast 510(k) input, and the fastest high-level fingerprint of an AI device. AI-generated but reliable in practice.
3. Judging fuzzy relevance
Fuzzy results trail off in relevance as you scroll. Use three signals to decide how far down to go: the fuzzy badge explanations, the intended use column, and whether your target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, you're past the relevant zone. A top hit with a low score (~0.4) and a stretched explanation is a hint the closest predicates are far away — the project may be headed for De Novo. Note the fuzzy search is a pattern match: it doesn't handle negation ("not") well, and hardware devices can appear — filter by SaMD/AI ML to cut them.
How do you judge how far down fuzzy search results to go?
Use the relevancy signals: the fuzzy badge explanations, the intended use column, and whether the target output (e.g., Cobb angle) still appears in the AI Performance sub-table. Once it stops appearing, results are trailing off in relevancy.
4. Device detail page: chat and citations
Click a device name to open its detail page: device facts on the left, a chat window on the right. Ask something like "Describe the training data". The answer carries little citation bubbles — click one to jump to the highlighted passage in the source PDF, so you can verify every AI answer against the document. There's also a Download PDF button for sharing.
How do you verify an AI chat answer on the device detail page?
Click the citation bubbles to jump to the relevant highlight in the source document.
Reading rule for every project: how many summaries do you read in full?
At least the three most relevant 510(k) or De Novo summaries, in full. After that, use targeted chat questions to confirm your memory quickly. The tool supports this professional habit — it doesn't replace it.
5. Side-by-side comparison
Select multiple rows in the results table (aim for under ~10), then open the PDF Viewer tab. Ask one question — it goes to all selected devices in parallel, each with citations. This is the fastest way to compare and contrast devices: training data, PCCP scope, how they handled adding new scanners, and so on.
What does the side-by-side PDF viewer mode do?
Select multiple devices, open the PDF viewer tab, and ask one question (e.g., "Describe the training data"). It queries all selected devices simultaneously with citations, so you can compare and contrast quickly.
6. Collections
With rows selected, go to the Collections tab and create a labeled collection (e.g., "Cobb Angle Project"). Reload that selection any time — before a client call, pull up the collection and ask questions across all of its devices at once.
How do you save a set of selected devices for later use?
Select the rows, go to the Collections tab, and create a labeled collection (e.g., "Cobb Angle Project"). You can reload the selection anytime and carry it into the PDF viewer and other tabs that support selections.
7. Product codes and the regulations tree
Click a product code in the results to jump to it in the regulations tree — identification text, sibling product codes, and devices you can open in a PDF viewer on the right. Click a regulation number to see its identification, special controls, and related product codes. You can also search by product code or regulation number at the top of the tree. Always read the special controls if any exist for your device — it broadens your search and sharpens pre-kickoff research.
What can you do from the regulations tree view?
Browse product codes and regulation numbers, read the identification text and special controls, browse sibling product codes, open device PDFs on the right, and search by product code or regulation number at the top of the tree.
8. Chart view
Click Show Chart and segment by regulation number (or product code) to see which regulations dominate your result set. Clicking a regulation takes you into the regulations tree. Great for spotting that most matches are, say, hardware laparoscopic devices — a cue to go back and filter.
How do you see which regulations dominate a search result set?
Click "Show Chart" and segment by Regulation Number. Clicking a regulation takes you to the regulations tree.
9. The predicate graph
Open the Predicates tab for a family-tree view of predicate relationships. Click a node to trace its parents and children; selections from search carry over pre-selected. Commonly predicated devices are worth reading — a lot of people predicated them for a reason. The visual lineage is also handy on client calls, e.g. to show how a predicate family evolved and justify why your predicate still holds.
In the predicate graph, why are commonly predicated devices worth reading?
A lot of people predicated them for a reason. Clicking a node traces parents and children, and selections from search carry over pre-selected.
10. Embeddings: the galaxy map
The Embeddings tab plots every matching document in a 2-D "galaxy map" where semantically similar devices cluster together. Hover or click clusters to explore, and let AI label the clusters for you. Embeddings beat product codes for grouping: two devices can carry different product codes (LLZ vs. QIH) yet do the same thing — the embedding captures the meaning of the intended use and device story. This is also exactly how retrieval-augmented generation (RAG) works under the hood, and it makes a great visual on client calls.
Try it yourself
Head to the search page and work through a few of these AI/ML fuzzy searches to build intuition: perivascular fat on CT · aortic valve calcification opportunistic screening on noncontrast CT · breast cancer prediction on digital pathology slides · autism detection · gestational age prediction · a hearing aid that can also detect a pulse · foundation model based analysis of ECG · large language models · penetration test. Watch how the relevance scores, intended use, and AI Performance tables tell you when results stop being meaningful.