1) Experimental investigation
After we were convinced that our device worked, we tested its usability on a pig's heart for the first time. A coronary artery of a commercially available porcine heart was cannulated and then filled with ICG solution. With the help of our camera, the ICG filled vessel could be visualized perfectly. (Figure 1-c)
2) Breast surgery
During breast tumor surgery, the identification and removal of the sentinel lymph node for histological examination is a critical issue. In practice, blue dye and isotopic labeling are used for this. In recent years, the use of ICG for the detection of lymphatic vessels and lymph nodes has become widespread [3]. During our study, a 50-year-old female patient underwent surgery for a breast tumor (ductal in situ carcinoma). To mark the sentinel lymph nodes, the surgeon routinely used double marking (blue dye + 99mTc radiopharmaceutical), which was supplemented with ICG administered next to the areola immediately before the operation. During the breast excision and sentinel lymph node biopsy, the lymphatic vessels leading to the axillary region could be easily followed with the help of our camera and the lymph nodes could also be identified. After the operation, the specimen was also examined separately, where we found that a lymph node that did not accumulate either blue dye or the isotope was also stained with ICG. (Figure 1-d) Later, our results were confirmed by the histological examination.
3) Liver surgery
There are several different methods for the use of ICG during liver surgeries. Tumorous lesions of the liver accumulate ICG as a positive contrast agent. For this, it is necessary to administer the dye intravenously to the patient at least one day before the operation. The other option can be used for anatomical resections, where we actually perform angiography with ICG administered during surgery. The part of the liver to be resected is excluded from the circulation even before the administration of ICG, and thus the part of the liver perfused and not perfused with ICG becomes clearly visible, i.e. the resection border [4]. In our own operation, a 54-year-old male patient operated on for hepatocellular carcinoma was given 25 mg of ICG intravenously the day before the operation, according to literature data. The following day, during the open liver surgery, in addition to the intraoperative ultrasound examination, we were also able to clearly identify the tumorous liver with our own camera. We could detect a fluorescent ring around the tumor, which is a typical sign for liver tumors. (Figure 1-e) During examination of the specimen, the non-fluorescent liver edge could also be reliably identified, the later histological examination also confirmed tumor-free resection margins.
4) Examination of intestinal perfusion
Due to the initial successes, our camera was also used in acute surgical operations. It was known to us from the literature that ICG angiography can help in the more accurate detection of bowel necrosis [5]. A 29-year-old female patient with type 1 diabetes and severe vasculitis affecting the abdominal vessels had to undergo acute surgery due to extensive intestinal necrosis. Intravenously administered ICG during the exploration clearly outlined the patchy loss of circulation affecting the entire small intestine section, which had already led to definitive intestinal necrosis in many places. However, with the help of ICG angiography, the lack of circulation could be clearly seen even in areas that looked macroscopically healthy to the naked eye. The ICG findings also confirmed the fact that surgical therapy was no longer possible for the patient.
5) Parathyroid surgery
One area where ICG fluorescence has been most extensively researched is parathyroid surgery. During surgeries, it is often difficult to identify small parathyroid glands that are not clearly separated from their surroundings. During the operation, a few seconds after the administration of ICG, the fluorescent "flash" of the parathyroid glands can be observed, which can help in identification [6]. We tested our camera during several parathyroid surgeries due to hyperparathyroidism and registered good results. With this technique, it is important to administer the ICG intravenously before the parathyroid gland is completely dissected, which can easily reach the gland due to the intact blood supply.
6) Examination of the kidney before transplantation
Adequate perfusion of the transplanted kidney is of particular importance during kidney transplants. During organ donation, problems with perfusion may arise, especially in the case of multiple renal arteries. ICG is suitable for checking adequate perfusion before transplantation and can also predict delayed graft function. In addition to all this, it is also an excellent opportunity to map the blood supply of the ureter [7]. With our own camera, before a kidney transplant, during the back table preparation phase, we injected a minimal amount (2.5 mg) of Verdye into the one-liter perfusion solution. The kidney was perfused with the solution prepared in this way, and the perfusion of the entire organ and the tissues around the ureter were also examined. Based on the obtained image the perfusion of the kidneys that are about to be transplanted can be evaluated excellently. (Figure1-f)