Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA.
Harvard Medical School, Boston, Massachusetts, USA.
Lasers Surg Med. 2022 Sep;54(7):935-944. doi: 10.1002/lsm.23576. Epub 2022 Jun 16.
BACKGROUND/OBJECTIVES: Optical coherence tomography (OCT) uses low coherence interferometry to obtain depth-resolved tissue reflectivity profiles (M-mode) and transverse beam scanning to create images of two-dimensional tissue morphology (B-mode). Endoscopic OCT imaging probes typically employ proximal or distal mechanical beam scanning mechanisms that increase cost, complexity, and size. Here, we demonstrate in the gastrointestinal (GI) tracts of unsedated human patients, that a passive, single-fiber probe can be used to guide device placement, conduct device-tissue physical contact sensing, and obtain two-dimensional OCT images via M-to-B-mode conversion.
We designed and developed ultrasmall, manually scannable, side- and forward-viewing single fiber-optic probes that can capture M-mode OCT data. Side-viewing M-mode OCT probes were incorporated into brush biopsy devices designed to harvest the microbiome and forward-viewing M-mode OCT probes were integrated into devices that measure intestinal potential difference (IPD). The M-mode OCT probe-coupled devices were utilized in the GI tract in six unsedated patients in vivo. M-mode data were converted into B-mode images using an M-to-B-mode conversion algorithm. The effectiveness of physical contact sensing by the M-mode OCT probes was assessed by comparing the variances of the IPD values when the probe was in physical contact with the tissue versus when it was not. The capacity of forward- and side-viewing M-mode OCT probes to produce high-quality B-mode images was compared by computing the percentages of the M-to-B-mode images that showed close contact between the probe and the luminal surface. Passively scanned M-to-B-mode images were qualitatively compared to B-mode images obtained by mechanical scanning OCT tethered capsule endomicroscopy (TCE) imaging devices.
The incorporation of M-mode OCT probes in these nonendoscopic GI devices safely and effectively enabled M-mode OCT imaging, facilitating real-time device placement guidance and contact sensing in vivo. Results showed that M-mode OCT contact sensing improved the variance of IPD measurements threefold and side-viewing probes increased M-to-B-mode image visibility by 10%. Images of the esophagus, stomach, and duodenum generated by the passively scanned probes and M-to-B-mode conversion were qualitatively superior to B-mode images obtained by mechanically scanning OCT TCE devices.
These results show that passive, single optical fiber OCT probes can be effectively utilized for nonendoscopic device placement guidance, device contact sensing, and two-dimensional morphologic imaging in the human GI tract in vivo. Due to their small size, lower cost, and reduced complexity, these M-mode OCT probes may provide an easier avenue for the incorporation of OCT functionality into endoscopic/nonendoscopic devices.
背景/目的：光学相干断层扫描（OCT）使用低相干干涉测量法获取深度分辨的组织反射率剖面（M 模式），并进行横向光束扫描以创建二维组织形态图像（B 模式）。内窥镜 OCT 成像探头通常采用近端或远端机械光束扫描机制，这会增加成本、复杂性和尺寸。在这里，我们在未镇静的人类患者的胃肠道（GI）中证明，被动式单光纤探头可用于引导器械放置、进行器械-组织物理接触感测，并通过 M 到 B 模式转换获得二维 OCT 图像。
我们设计并开发了超小型、手动可扫描、侧视和前视单光纤探头，可获取 M 模式 OCT 数据。侧视 M 模式 OCT 探头被整合到设计用于采集微生物组的刷子活检设备中，而前视 M 模式 OCT 探头则被整合到用于测量肠道潜在差异（IPD）的设备中。在六名未镇静的患者体内的 GI 中使用了配备 M 模式 OCT 探头的设备。使用 M 到 B 模式转换算法将 M 模式数据转换为 B 模式图像。通过比较探头与组织物理接触和不接触时 IPD 值的方差来评估 M 模式 OCT 探头物理接触感测的有效性。通过计算显示探头与腔道表面紧密接触的 M 到 B 模式图像的百分比来比较前视和侧视 M 模式 OCT 探头生成高质量 B 模式图像的能力。被动扫描的 M 到 B 模式图像与机械扫描 OCT tethered capsule endomicroscopy（TCE）成像设备获得的 B 模式图像进行定性比较。
将 M 模式 OCT 探头整合到这些非内窥镜 GI 设备中，可安全有效地实现 M 模式 OCT 成像，从而实现实时设备放置引导和体内接触感测。结果表明，M 模式 OCT 接触感测将 IPD 测量的方差提高了三倍，侧视探头将 M 到 B 模式图像的可见度提高了 10%。通过被动扫描探头和 M 到 B 模式转换生成的食管、胃和十二指肠图像的质量明显优于机械扫描 OCT TCE 设备获得的 B 模式图像。
这些结果表明，被动式单光纤 OCT 探头可有效用于非内窥镜设备的放置引导、设备接触感测和人体 GI 道内的二维形态成像。由于其尺寸小、成本低、复杂性降低，这些 M 模式 OCT 探头可能为将 OCT 功能纳入内窥镜/非内窥镜设备提供更容易的途径。
