Clinical Application of Fluorescence Imaging Technology in Hepatobiliary Surgery

During liver tumor removal or treatment of spread cancer in the liver, glowing pictures help guide choices in the operating room - no matter if the cut is small or large. Light gets soaked up by special dyes, then given off again as a different shade, visible through tech eyes. A camera catches this glow, showing it live on screen for the team to see. Indocyanine green, often called ICG, marks tissues this way during operations. Made by various producers across the globe, it first entered medical use back in May 1960, mainly checking how well livers work. What started decades ago still shapes decisions today inside hospitals. ICG soaks up light best around 800 to 810 nanometers when it's in blood. Its glow shows up strongest at 835 nanometers. Because of this, the dye reaches about a centimeter into tissue, though clear signals come from depths under 8 millimeters. Once pushed into a vein, ICG sticks quickly to proteins floating in plasma. Liver cells grab hold of it soon after. Then it leaves the body through bile pathways. Most of the substance clears from circulation in roughly two and a half to three minutes. Older kids and grown-ups should get no more than 2 milligrams per kilogram of their weight. After being injected into loose tissue, ICG moves into the lymph pathways. It gathers in lymph nodes first, then flows toward the thoracic duct and blood channels, finally leaving through bile. Light emission from ICG in these structures lasts beyond a day. This method shows clearer results than scans done with technetium-99m when tracking lymph node locations.

 

Section 1 Fluorescence Cholangiography

When removing a gallbladder through small incisions, glowing pictures may show how bile tubes outside the liver are arranged. These visuals might catch unusual tube layouts early. Sometimes, extra bile channels appear that aren't typical. Seeing them helps avoid problems. Medical guidelines support this method strongly. Proof from studies backs its usefulness clearly.

Section 2 Tumor Imaging

Bright glow from ICG helps spot cancer with strong precision. Though unseen before surgery, growths on or inside the liver show up - like HCC, bile duct cancers, or spread from other organs. Yet nearly two out of five glowing spots aren't cancer at all, so any fresh finding mid-surgery needs extra scans to verify (Class IIa; Level II-3). While removing deeper tumors, the light signal guides clean edges, keeping tools from slicing into diseased tissue during removal for mets or HCC (Class IIa; Level II-3).

Section 3 Fluorescence Guided Liver Resection Anatomy

Fluorescence imaging helps mark segment borders during open and laparoscopic liver surgery. At the same time, doctors rely on ultrasound inside the operating room to spot the portal vein after it takes up ICG - backed by Class IIb guidelines and Level II-2 proof.

Section 4 ICG Fluorescence Used in Liver Surgery for Transplants

During donor liver removal, glowing markers might show the area near the bile duct branches. This glow guides where to cut safely. Experts agree it's useful, though proof comes from moderate-quality studies. The method has earned a second-tier rating based on current data.

 

 

Section 1: Fluorescence Cholangiography

A. What role does fluorescence play in laparoscopic cholecystectomy?

Back in 2008, Ishizawa's team tried something new - injecting ICG into patients' veins to light up the bile system during gallbladder removal. Over time, glowing signals from ICG began showing up more often in operations involving the liver and bile pathways, especially when machines helped surgeons operate or livers were replaced. Instead of just relying on standard imaging, doctors started using these fluorescent cues to map out duct structures outside the liver.

B. Can the extrahepatic bile ducts be clearly visualized and identified using ICG fluorescence?

ICG glow makes bile duct shapes easier to spot when removing a gallbladder. This helps avoid harming those tubes, especially ones shaped unusually or hidden until now. Sometimes what looks like the main duct isn't - lighting changes perception. Research shows glowing views beat standard light most times. One major study in 2019 tracked 639 people at eight sites worldwide. More than half saw benefits under special imaging. Exact numbers appear nearby below. Once more, the numbers point clearly toward fluorescence cholangiography being better at spotting outside-the-liver bile passages. Yet here's a catch - light used in this method barely slips through ten millimeters of body matter. So when dense layers hide those ducts - say, weblike fibers near Calot's area - it might stay hidden. This blocking effect shows up most when people carry extra weight or battle intense gallbladder swelling.

C. Can accessory hepatic ducts be clearly identified?

During surgery, fluorescent imaging shows unusual liver ducts as they appear. Ishizawa's team found this method spotted every atypical duct outside the liver before cutting. A controlled experiment revealed rare duct forms showed up in 4.1 percent of cases before removal, then rose to 6.2 percent afterward - figures exceeding those seen with standard lighting.

D. Sure thing. Here's your rewritten version: Got a look at those bile duct stones yet?

One stone in the bile duct slipped past fluorescence cholangiography, probably hidden by glowing bile that collected nearby. Not every blockage shows up clear - some vanish under bright fluid shadows. Behind the pancreas head, where the duct runs tight, problems often stay out of sight. Every cystic duct stone lit up without fail during Ishizawa's scan. Brightness meant visibility - but sometimes too much light conceals instead.

E. Can bile leakage be detected?

Few details exist about this, yet some scattered accounts mention glow effects spotting bile leaks at the liver's severed edge when part is removed. While coverage stays thin, a handful of instances highlight light signals catching fluid escape during surgery. Not much has been written, still, rare records show luminescence revealing leak paths where tissue was cut. Though information trails off, occasional notes describe bright markers exposing seepage from incisions made into the organ.

F. Can the intrahepatic biliary tree be delineated by fluorescence?

Few layers deep is where near-infrared light can reach, so seeing liver bile passages usually needs a bit of tissue moved aside. Fluorescence cholangiography struggles here, blocked by how shallow the glow travels through body matter.

G. Can fluorescence cholangiography replace traditional cholangiography?

Picture showing bile ducts using glowing dye might work better than X-ray methods during surgery. Right away, it skips radiation by giving live views, making things quicker and simpler for the team. Instead of threading tubes that risk harming ducts, this method avoids those moves entirely. Around the main channels, nearby tissues stand out more sharply through the glow effect. Still, fluorescence cholangiography misses bile duct stones along with details inside the liver's bile pathways. Because of that gap, standard imaging holds ground it can't fully take over.

H. What is the appropriate dose and timing of ICG injection?

Thirty minutes to an hour prior to the procedure, ICG may go into a vein. Its exit through bile takes anywhere from several minutes up to twenty hours. A full amount could measure just 2.5 mg, or scaled by body weight at 0.05 mg per kilogram. Injection straight into the bile passage is another path. That route uses a weaker mix - each milliliter holds only 0.025 mg of ICG.

 

Section 2: Tumor Imaging

A. Under a glow, how much dye works best when cutting out growths in the liver?

Timing matters - when should it be given before surgery? Which method lights up problem spots most clearly? Instead of guessing, could clearer signals come from adjusting camera settings mid-procedure?

Some areas look suspicious but aren't cancer - how do teams tell the difference? Maybe less confusion happens if surgeons compare real-time color shifts with pre-op scans. Could repeating imaging at different angles lower mistakes? Not every bright patch means disease - experience might help sort noise from truth. What if the light fades too fast - does that hide deeper tissue issues? Fewer errors may follow when protocols include second looks during operation.

B. How does glowing light help show cancer during surgery?

At first, spotting HCC under fluorescence came by surprise while doing cholangiography. This glow might happen because tumors miss typical bile pathways - either broken function or messy layout - or they squeeze nearby ducts. After injecting ICG before surgery, the cancer grabs the dye yet struggles to flush it out, making the mass stand out from healthy liver tissue. Sometimes, when cancer invades the portal vein or forms clots, the affected part of the liver lights up more intensely. Most times, the test lit up when cancer showed up - 273 out of 276 confirmed cases caught it right. Sixteen spots triggered alarms without being cancer. Those came from healed liver areas, odd cell growths, extra bile paths, even dead bits inside tissues. After adjusting for those, about 94 out of every 100 flagged results were truly cancer.

Could fluorescence look different in HCC compared to its spread outside the liver, alongside colon cancer spots in the liver, bile duct growths inside the liver, or unrelated masses? Might these show unique glows under scan? What if lighting patterns shift across tumor types? Does color behavior change when disease moves beyond the original site? Can we tell one mass from another by how it shines? Would bile-related cancers reflect differently than others? Is light response distinct even within liver tissue? How do secondary tumors compare to primary ones visually? Might detection rely on such visual contrasts? Could each type alter glow intensity in its own way?

Faint glow seen in liver scans splits into three kinds when spotting cancer spots

Fluorescence shows the whole tumor clearly set apart from nearby tissue.

Some parts of the tumor glow under special light

A glow appears at the edge of the mass - not within it - where healthy liver tissue lights up in a circular pattern nearby. This rim-like shine comes from untouched areas surrounding the growth, showing activity only in normal cells bordering the abnormal spot. The lesion itself stays dark while neighboring regions emit light, outlining its shape indirectly through contrast.

Some liver cancers glow under certain light, depending on how abnormal they look. Not every tumor lights up the same way - some shine fully, others only partly. Poorer quality tumors often show a ring-like glow, especially when blood vessels are involved. Spots outside the liver might become visible too, since cancer cells there still grab a special dye from the blood. But these spots cannot drain it, so the color stays trapped inside. When scientists sent the dye through a specific vein, they saw clumps in major blood pathways light up. Hidden spread areas, missed by scans before surgery, may stand out this way. That hint came after watching real-time coloring during operations. Rim glow appears often in CRLM, probably because the growth presses nearby healthy bile paths, making ICG leak oddly. Inside that glowing edge, what you see under the lens isn't quite like the outline seen in low-grade HCC. According to Ishizawa's team, when spotting CRLM on the liver's outer layer, ICG lighting never missed it - perfect accuracy every time. Spotting tumors just 3 mm wide? Surgery-time sound scans along with light signals beat CT before surgery followed by scans during. Even after strong prep drugs shrink tumors, faint glimmers still catch hidden morsels of disease, maybe lowering how often cancer returns where the organ meets open space.

C. What are the limitations of fluorescence imaging for tumor identification?

Close to the surface, near-infrared light helps spot tumors up to 8 mm deep in the liver. Beyond that depth, it loses effectiveness. Instead, surgeons turn to ultrasound during surgery. This method finds growths hidden farther inside tissue. When cutting into the liver, any abnormal area within 8 mm of the fresh edge can still show up with light-based scans. Deeper ones stay invisible without sound waves guiding the way.

D. How often does fluorescence mistakenly spot a tumor when there isnt one, also how frequently does it miss a real one?

Even though fluorescence imaging picks up tiny details well and often points to real issues, mistakes happen - up to four out of ten findings might be wrong. Things like scarred liver tissue, unusual but harmless growths, injecting ICG dye too close to surgery time - say less than one day before - plus abnormal bile duct growth, dead cells, fluid-filled sacs or blood vessel clusters, and odd-looking benign spots can confuse results. When a new spot lights up during surgery, doctors must check it more closely using looks, touch, or sound waves inside the body. Sometimes cancerous liver tumors do not show up at all under this method. This tends to slip through when too much time passes after giving ICG - especially beyond twenty-four days.

E. Can ICG fluorescence ensure safe surgical margins?

Glowing spots inside a tumor, or a ring of glow around it, help guide surgery. When light shows up on the newly cut edge, there could be cancer cells exposed. Instead of stopping, keep cutting beyond the bright zone so everything comes out cleanly. Sometimes small dots of glow appear on the liver's outer layer - that hints at deeper spread through blood pathways nearby. Because of this, taking more tissue around those points increases chances of full removal. When dealing with HCC or liver adenoma, cutting just outside the glowing edge tends to remove all cancer cells. Still, in cases of liver metastases, results aren't so clear - they hinge on how much the tumor squeezes nearby bile ducts. The precision of the imaging tools matters too, plus how wide the lit-up zone appears; that glow rarely stretches past 5 millimeters because light penetration limits it. Right now, there's a gap - research hasn't yet confirmed if slicing right at that bright outline leaves enough healthy tissue behind. Yet evidence leans toward stepping 1 centimeter past the fluorescent line as a safer bet for clean edges.

F. When should ICG be given, plus how much works best for spotting tumors?

Experts still aren't sure about the best amount of ICG or when exactly to give it. Earlier work suggested 0.5 mg/kg given two weeks before surgery helps show tumors during operations. That particular plan started out aiming to check how well the liver functions, not to spot cancer. When looking only for tumors, doctors might cut the dose down to 0.2 mg/kg, using it just one or two days ahead instead. If someone has cirrhosis or damaged liver from chemo, skipping ICG the day prior makes sense - too much glow in healthy tissue could hide tumors or create misleading signals.

 

Section 3: Anatomical Liver Resection

A. What is the role of fluorescence in anatomical liver resection?

Back in 2008, Aoki spotted something new - liver parts could glow when stained with fluorescence. Instead of mixing dyes broadly, he pushed 1 mL of ICG (at 5 mg/mL) straight into a branch of the portal vein, lighting up only the area fed by that route. When used during open procedures, it worked more than 90 percent of the time. By 2012, Ishizawa took that method further, testing two fresh approaches based on Aoki's work - "positive staining" and its counterpart, "negative staining." Compared to old-school methylene blue, ICG-guided marking stands out through clearer contrast and fewer side effects

a. Deep inside the liver, glowing patterns appear just as clearly as they do on the outer edges. Where tissue is sliced open, bright lines trace each section apart. Light reveals boundaries below the surface, not merely those seen at the top. Inside the organ, after cutting, these markers stay visible across layers. Each area separates under glow, both above and within. What shows up on skin also appears where the knife passed through.

b. Second, it provides three-dimensional visualization of liver segments.

Right away, once ICG goes into a vein, the glowing view shows up. This happens without delay. As the liver tissue gets divided, guidance unfolds continuously. The process moves step by step, supported by live feedback. Right there, the image helps track progress.

c. Staining works well whether the procedure is done through small incisions or larger ones. It doesn't matter if tools are inserted via scope or by hand - results stay consistent. With either method, clarity remains strong. Even when techniques differ, outcomes hold steady. Through tiny cuts or wide openings, visibility stays clear.

B. What is positive staining?

With live imaging from a tiny internal camera, doctors inject a glowing dye into the blood vessel feeding the part of the liver holding the tumor. As the dye spreads, it colors that section, showing a sharp edge where tissue changes on the organ's outer and inner surfaces. One drawback? Painting the area this way takes precise control - expertise in scanning during surgery plus accurate needle placement are must-haves. Because hitting those marks consistently proves tough, certain surgeons opt instead to guide needles through the skin before surgery, marking the zone with dye ahead of time. Then they proceed with minimally invasive removal of the defined portion, achieving outcomes just as good.

C. What is negative staining?

Once the portal branch feeding the tumor area is clamped, ICG dye goes into a vein. The glowing color spreads through healthy parts of the liver but skips the blocked section. That part stays dark while everything else lights up. Instead of lighting up the target zone directly, skipping it makes things less complex. It works better when reaching branches outside the liver is straightforward - like on the left side (segments II and III) or central-right areas close to major ducts (IVb, V, VI). When cutting out just one small piece during an open procedure, making the target glow clearly tends to be preferred. Starting off different than negative staining, this method lets you tweak how dark the stain gets plus where it shows up. Liver section edges turn out sharper, easier to see. Resecting those upper back parts - segments seven and eight - goes smoother somehow. Trouble kicks in when trying to poke the portal vein; that part takes serious practice. Surgeons spend ages getting steady with it. When removing multiple sections or half the liver, the older technique fits better. Down below there's a chart helping pick which approach works for each liver zone.