This work consists of three original articles and is focused on the overall question: How can hyperspectral imaging contribute to patient safety and improve outcomes during abdominal surgery? The hypothesis was that HSI is suitable for the intraoperative assessment of tissue structures and decision support in routine clinical use. Spectral imaging was performed with the TIVITA Tissue for open surgery or TIVITA Mini system for laparoscopic HSI from Diaspective Vision GmbH (Am Salzhaff-Pepelow, Germany). Both HSI systems use pushbroom mode and
provide 100 spectral channels in the visible and near-infrared spectral range from 500 - 1000 nm. The Number of Effective Pixels is at least 640 × 480 (x-, y-axis), while the field of view and spatial resolution depend on the measurement distance and the used focal length of the objective. Illumination is done by halogen spots for open surgery and broadband LED in the laparoscopic system.
The first part of this work aimed to evaluate HSI for the measurement of ischemic conditioning effects of the gastric conduit during esophagectomy. Ischemic preconditioning by dividing major blood vessels of the stomach prior to gastric pull-up is performed to improve the perfusion at the later esophagogastric anastomosis to reduce the risk of leaks. Intraoperative hyperspectral records of the gastric tube were acquired from 22 patients through the mini-thoracotomy. Fourteen of them underwent ischemic conditioning of the stomach several days before the two-step transthoracic esophagectomy and gastric pull-up with intrathoracic anastomosis was performed. The tip of the gastric tube (later esophago-gastric anastomosis) was measured with HSI. These in vivo records showed that the tissue oxygenation of the gastric conduit was significantly higher in patients who underwent ischemic conditioning (78% vs. 66%; p = 0.03).
In the second part of this work, a novel hyperspectral imaging system for MIS is described and evaluated to address the requirements for clinical use and high-resolution spectral imaging. Reference objects and resected human tissue were used to show spectral conformity with the approved HSI device for open surgery. Furthermore, varying object distances were investigated and the signal-to-noise ratio (SNR) for different light sources were measured. Measurements with both systems were performed on a human tissue resectate and compared quantitatively. It was shown that the handheld design of the laparoscopic HSI system enables the processing and visualization of spectral data in parallel during acquisition within a few seconds. The obtained measurements from both spectral imaging devices were consistent and a mean SNR of 30 to 43 dB (500 to 950 nm) was found using a standard rigid laparoscope in combination with a broadband LED light source.
Finally, in the third part of this work, different image registration methods were investigated to compensate for small movements of the laparoscope and tissue deformations. The obtained image transformation is used to augment the laparoscopic color video with the static HSI data to support intraoperative localization. Multiple feature-based algorithms and a pre-trained deep homography neural network (DH-NN) were evaluated for the estimation of appropriate image transformations (single and multi-homography). The methods were validated with a ground truth dataset of 750 annotated laparoscopic images, that was created during this work, and in vivo data from the TIVITA Mini system. All feature-based single homography methods outperformed the fine-tuned DH-NN in terms of reprojection error, Structural Similarity Index Measure (SSIM), and processing time. The feature detector and descriptor ORB1000 enabled video-rate registration of laparoscopic images on standard hardware with submillimeter accuracy.
Therefore, all initially stated research questions could be confirmed with the applied methods. Although technical limitations have been identified, the non-invasive and contact-free measurement principle makes HSI attractive for a variety of surgical disciplines.:1 Introduction
1.1 Interaction of light and biological tissue
1.2 Spectral imaging systems
1.3 Medical applications of spectral imaging
1.4 Intraoperative visualization of spectral data
2 Original Articles
2.1 Evaluation of hyperspectral imaging (HSI) for the measurement of ischemic conditioning effects of the gastric conduit during esophagectomy
2.2 Laparoscopic system for simultaneous high-resolution video and rapid hyperspectral imaging in the visible and near-infrared spectral range
2.3 Comparison of image registration methods for combining laparoscopic video and spectral image data
3 Summary
3.1 Conclusions and Outlook
4 References
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:91118 |
| Date | 30 April 2024 |
| Creators | Köhler, Hannes |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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