Intraoperative Real-Time Visualization of the Lymphatic Vessels Using Microscope-Integrated Laser Tomography

Imaging in reconstructive microsurgery - current standards and latest trends

In microsurgery, many different imaging techniques are available in both flap and lymphatic surgery that all come with their own advantages and disadvantages. In flap surgery, CT angiography is considered as the gold standard. Among others, Doppler ultrasound, color Doppler ultrasound, ICG, and smartphone-based thermal cameras are valuable imaging techniques. In lymphatic surgery, photoacoustic imaging, laser tomography, contrast-enhanced magnetic resonance imaging, and high frequency ultrasound stand available to surgeons next to the current standard of lymphoscintigraphy. It is crucial to know the advantages and disadvantages to various techniques and highly adviced to microsurgeons be capable of using a variety of them.

Imaging Modalities for Evaluating Lymphedema

Lymphedema is a progressive condition. Its therapy aims to reduce edema, prevent its progression, and provide psychosocial aid. Nonsurgical treatment in advanced stages is mostly insufficient. Therefore-in many cases-surgical procedures, such as to restore lymph flow or excise lymphedema tissues, are the only ways to improve patients' quality of life. Imaging modalities: Lymphoscintigraphy (LS), near-infrared fluorescent (NIRF) imaging-also termed indocyanine green (ICG) lymphography (ICG-L)-ultrasonography (US), magnetic resonance lymphangiography (MRL), computed tomography (CT), photoacoustic imaging (PAI), and optical coherence tomography (OCT) are standardized techniques, which can be utilized in lymphedema diagnosis, staging, treatment, and follow-up. Conclusions: The combined use of these imaging modalities and self-assessment questionnaires deliver objective parameters for choosing the most suitable surgical therapy and achieving the best possible postoperative outcome.

The significance of the microlymphangiogenesis, microangiogenesis, and combined detection of programmed cell death-1 protein (PD-1)/ki67 in gastric cancer tissues

PURPOSE

To investigate the relationship between the microlymphangiogenesis, microangiogenesis, and combined detection of the programmed cell death-1 protein (PD-1)/ki67 in patients with gastric cancer as well as the disease prognosis.

METHODS

Immunohistochemistry was used to detect the microlymphatic density (MLD) and microvessel density (MVD) in the central and peripheral zones in 92 cases of gastric cancer, along with the number of PD-1- and ki67-positive tumor cells.

RESULTS

The central zone of the gastric cancer tissue contained fewer atretic cord-like lymphatic vessels than the peripheral zone, while the peripheral zone contained an increased number of lymphatic vessels compared with the central zone. In most cases, the lumen was also dilated. Compared with the MLD in the peripheral zone, the MLD in central zone was significantly decreased. Compared with the number of PD-1-positive cells in the peripheral zone, the number of PD-1-positive cells in the central zone was significantly decreased, and compared with the number of ki67-positive cells in the peripheral zone. The differences in the microlymphangiogenesis, microangiogenesis, and the number of PD-1- and ki67-positive cells among the different histological types were not statistically significant. The microlymphangiogenesis, microangiogenesis, and PD-1- and ki67-positive cells were significantly decreased in the gastric cancer tissues from the patients in stages T1 and T2 compared with the gastric cancer tissues from the patients in stages T3 and T4.

CONCLUSIONS

The detection of the MLD and MVD as well as the positive expression of PD-1 and ki67 in gastric cancer tissue are important reference indicators for judging the prognosis of gastric cancer.

Office-Based Lymphatic Supermicrosurgery: Supermicrosurgical Lymphaticovenular Anastomosis at an Outpatient Clinic

BACKGROUND

 Supermicrosurgical lymphaticovenular anastomosis (LVA) has become popular for the treatment of compression-refractory lymphedema. With advancement of navigation tools, LVA can be performed with more ease and safety, allowing office-based LVA at an outpatient clinic.

METHODS

 Office-based LVA was performed on patients with compression-refractory secondary extremity lymphedema by a well-experienced supermicrosurgeon (T.Y.) under local infiltration anesthesia. Indocyanine green (ICG) lymphography and vein visualizer were used to localize vessels preoperatively. A stereoscopic microscope (Leica S6E, Leica Microsystems, Germany) or a relatively small operative microscope (OPMI pico, Carl Zeiss, Germany) was used for LVA. Operative records and postoperative results were reviewed to evaluate feasibility of office-based LVA.

RESULTS

 LVAs were performed on 27 arms and 42 legs, which resulted in 131 anastomoses via 117 incisions. ICG lymphography stage included stage II in 47 limbs, and stage III in 22 limbs. Time required for one LVA procedure (from skin incision to skin closure in one surgical field) ranged from 13 to 37 minutes (average, 24.9 minutes). One year after LVA, all cases showed significant volume reduction (lymphedematous volume reduction; 0.5-23.6%, average 13.23%). No postoperative complication was observed.

CONCLUSION

 LVA can be performed with safety and effectiveness outside an operation theater. Patient selection, precise preoperative mapping, and experience of a surgeon are key to successful office-based LVA.

Comparative Analysis of Preoperative High Frequency Color Doppler Ultrasound versus MR Lymphangiography versus ICG Lymphography of Lymphatic Vessels in Lymphovenous Anastomosis

BACKGROUND

 Despite the extensive use of various imaging modalities, there is limited literature on comparing the reliability between indocyanine green (ICG) lymphography, MR Lymphangiogram (MRL), and high frequency color Doppler ultrasound (HFCDU) to identify lymphatic vessels.

METHOD

 In this study of 124 patients, the correlation between preoperative image findings to the actual lymphatic vessel leading to lymphovenous anastomosis (LVA) was evaluated. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and simple detection were calculated. Subgroup analysis was also performed according to the severity of lymphedema.

RESULTS

 Total of 328 LVAs were performed. The HFCDU overall had significantly higher sensitivity for identifying lymphatic vessels (99%) over MRL (83.5%) and ICG lymphography (82.3%)(p < 0.0001). Both ICG lymphography and HFCDU had 100% specificity and PPV. The NPV was 3.6%, 6.5% and 57.1% respectively for MRL, ICG lymphography, and HFCDU. All modalities showed high sensitivity for early stage 2 lymphedema while HFCDU showed a significantly higher sensitivity for late stage 2 (MRL:79.7%, ICG:83.1%, HFCDU:97%) and stage 3 (MRL:79.7%, ICG:79.7%, HFCDU:100%) over the other two modalities (p < 0.0001).

CONCLUSION

 This study demonstrated while all three modalities are able to provide good information, the sensitivity may alter as the severity of lymphedema progresses. The HFCDU will provide the best detection for lymphatic vessels throughout all stages of lymphedema. However, as each modality provides different and unique information, combining and evaluating the data according to the stage of lymphedema will be able to maximize the chance for a successful surgical outcome.

Preoperative Mapping of Lymphatic Vessels by Multispectral Optoacoustic Tomography

Background: In lymphatic reconstructive surgery, visualization of lymph vessels is of paramount importance. Indocyanine green (ICG) lymphography is the current gold standard in preoperative lymphatic imaging. However, visualization of lymph vessels is often limited by an overlying dermal backflow of ICG, becoming particularly prominent in advanced lymphedema stages. Multispectral optoacoustic tomography (MSOT) has recently been introduced as a promising noninvasive tool for lymphatic imaging. Methods and Results: A single-center proof-of-concept study with a prospective observational design was conducted at the Department of Plastic Surgery and Hand Surgery of the University Hospital Zurich. Between February 2021 and August 2021, seven patients with different grades of lymphedema were analyzed by the MSOT Acuity system before undergoing lymphovenous anastomosis (LVA). Conventional ICG lymphography served as comparison. MSOT succeeded to accurately depict blood and lymphatic vessels at different locations in six patients, including areas of dermal backflow. The MSOT signal of lymph vessels further correlated well with their macroscopic appearance. Conclusion: We could successfully visualize lymphatic vessels in patients with lymphedema by MSOT and establish the new method for preoperative mapping and selection of incision sites for LVA. Regardless of dermal backflow patterns, MSOT proved to be a valuable approach for identifying and clearly discerning between lymphatic and blood vessels.

Long-term Use of Ultrasound for Locating Optimal LVA Sites: A Descriptive Data Analysis

BACKGROUND

 Preoperative mapping of lymphatic vessels for lymphovenous anastomosis (LVA) surgery is frequently performed by indocyanine green (ICG) lymphography solely; however, other imaging modalities, such as ultrasound (US), might be more efficient, particularly for Caucasian patients. We present our preoperative assessment protocol, experience, and approach of using US for locating optimal LVA sites.

MATERIAL AND METHODS

 Fifty-six (16 males) lymphedema patients who underwent LVA surgery were included in this study, 5 of whom received two LVA operations. In total, 61 LVA procedures with 233 dissected lymphatic vessels were evaluated. Preoperative US was performed by the author S.M. 2 days before intraoperative ICG lymphography. Fluid-predominant lymphedema regions were scanned more profoundly. Skin incisions followed preoperative US and ICG lymphography markings. Detection of lymphatic vessels was compared between ICG lymphography and the US by using the intraoperative verification under the microscope with 20 to 50x magnification as the reference standard.

RESULTS

 Among the dissected lymphatic vessels, 83.3% could be localized by US, and 70% were detectable exclusively by it. In all, 7.2% of US-detected lymphatic vessels could not be found and verified intraoperatively. Among the lymphatic vessels found by US, only 16% were apparent with ICG before skin incision. In total, 23.2% of the dissected lymphatic vessels could be visualized with ICG lymphography preoperatively. Only 9.9% of the lymphatic vessels could be found by ICG alone.

CONCLUSION

 High-frequency US mapping accurately finds functional lymphatic vessels and matching veins. It locates fluid-predominant regions for targeted LVA surgeries. It reveals 3.6 times as many lymphatic vessels as ICG lymphography. In our practice, it has an integral role in planning LVA procedures.

Recipient Venule Selection and Anastomosis Configuration for Lymphaticovenular Anastomosis in Extremity Lymphedema: Algorithm Based on 1,000 Lymphaticovenular Anastomosis

BACKGROUND

 The lymphaticovenular anastomosis (LVA) has three components, lymphatics, venules, and anastomosis, and all of them influence the anastomotic pressure gradient. Although it has been demonstrated that venule flow dynamics has an independent impact on the outcomes regardless the degeneration status of lymphatic vessels, recipient venules (RV) have been mainly neglected in literature.

PATIENTS AND METHODS

 From January 2016 to February 2020, 232 nonconsecutive patients affected by extremity lymphedema underwent LVA, for a total of 1,000 LVAs. Only patients with normal-to-ectasic lymphatic collectors were included to focus the evaluation on the RV only. The preoperative collected data included the location, diameter, and continence of the selected venules, the expected number, the anastomoses configuration, and their flow dynamics according to BSO classification.

RESULTS

 The 232 patients included 117 upper limb lymphedema (ULL) and 115 lower limb lymphedema (LLL). The average size of RV was 0.81 ± 0.32 mm in end-to-end (E-E), 114 ± 0.17 mm in end-to-side (E-S), 0.39 ± 0.22 mm in side-to-end (S-E), and 0.76 ± 0.38 mm in side-to-side (S-S) anastomoses. According to the BSO classification, on a total of 732 RV, 105(14%) were backflow venules, 136 (19%) were slack, and 491 (67%) were outlet venules. Also, 824 (82%) were E-E, 107 (11%) were E-S, 51 (5%) were S-E, and 18 (2%) were S-S anastomoses.

CONCLUSION

 Based on 1,000 LVAs with similar lymphatic characteristics, we propose our algorithm that may aid the lymphatic microsurgeon in the selection of RV and the consequent anastomosis configuration, in order of obtain the best flow dynamic through the LVA. This therapeutic study reflects level of evidence IV.

The application of indocyanine green (ICG) and near-infrared (NIR) fluorescence imaging for assessment of the lymphatic system in reconstructive lymphaticovenular anastomosis surgery

INTRODUCTION

Lymphedema has traditionally been managed through noninvasive means with complete decongestive therapy. However, complete decongestive therapy is an intensive program that requires lifelong adherence by patients with lymphedema. More recently, reconstructive surgical procedures have shown promise in improving lymphedema by physiologically restoring lymphatic function. One of these types of procedures, lymphaticovenular anastomosis, relies on technological advances in imaging, particularly indocyanine green lymphangiography.

AREAS COVERED

This article reviews indocyanine green and near-infrared fluorescence imaging. In addition, this article discusses the application of this imaging to the preoperative, intraoperative, and postoperative assessment of the lymphatic system in the setting of lymphaticovenular anastomosis surgery.

EXPERT OPINION

Indocyanine green lymphangiography offers significant advantages over other types of imaging of the lymphatic system. In the future, it is hopeful that additional options for these imaging devices will become available which may increase their accessibility by centers interested in performing reconstructive lymphatic surgery, including in relation to cost. Finally, more studies with higher levels of evidence are needed to better define the long-term outcomes associated with lymphatic surgery including LVA. In this regard, practitioners should fully harness the information conferred by ICG lymphangiography as both a clinical and research tool.