Fluorescence navigation with indocyanine green for detecting sentinel lymph nodes in breast cancer

Indocyanine green fluorescence-navigated sentinel node biopsy showed higher sensitivity than the radioisotope or blue dye method, which may help to reduce false-negative cases in skin cancer

BACKGROUND AND OBJECTIVES

Although sentinel lymph node (SLN) biopsy using radioisotope (RI) and blue dye (BD) achieved a high detection rate, approximately 5% of melanomas with negative SLNs develop nodal metastasis. We tested a new lymphatic navigation method using indocyanine green fluorescence imaging (ICG-FI) to detect such "occult" SLNs.

METHODS

Thirty-four skin cancer patients received SLN biopsy with the following three methods: RI (99Tc-tin colloid), BD (2% patent blue), and ICG (0.5% indocyanine green). Lymph nodes detected by any of the three methods were counted as SLNs.

RESULTS

ICG-FI detected more SLNs in 8 out of the 34 cases (24%). The average numbers of SLNs detected by ICG-FI, RI, and BD were 2.18, 1.76, and 1.73, respectively. Interestingly, ICG-FI not only detected more SLNs in one basin (ICG-FI: 1.64, RI: 1.50, and BD: 1.51 SLNs per basin), but also detected additional SLNs in other basins (ICG-FI: 1.32, RI: 1.18, and BD: 1.15 basins per case).

CONCLUSION

ICG-FI detected SLNs more efficiently than did the conventional methods, and these "occult" SLNs may offer an explanation for some false-negative cases. We recommend using ICG-FI in addition to a conventional method to reduce the risk of overlooking these "occult" SLNs.

Indocyanine green (ICG)-based fluorescence navigation system for discrimination of kidney cancer from normal parenchyma: application during partial nephrectomy

PURPOSE

To determine the definite border between normal and tumor kidney tissues during partial nephrectomy (PN) procedures using intraoperative indocyanine green (ICG)-based fluorescence imaging.

METHODS

Sixteen potential candidates for PN with organ-confined, small renal masses treated between July 2008 and June 2011 at Shimane University Hospital were enrolled. An ICG-based fluorescence navigation (FN) system was used to evaluate the border between the tumor and normal kidney parenchyma (step 1), the cavity following tumor excision (step 2), and the negative surgical margin of resected tissues (step 3). The R.E.N.A.L nephrometry score (RNS) was applied to evaluate the correlation between tumor anatomy and ICG-based fluorescence imaging.

RESULTS

In step 1, in vivo probing revealed 14 tumors with a mean RNS of 7 points that showed quite low ICG fluorescence signals in the tumor mass as compared with normal kidney parenchyma. In step 2, in vivo probing around the bed revealed highly fluorescent signals with no remnant tumor residing in 10 cases with a mean RNS of 6 points. In step 3, ex vivo probing revealed cancer tissues involving normal parenchyma that were completely excised with minimum amounts of normal parenchyma in all 16 resected specimens.

CONCLUSIONS

ICG-based FN system was very helpful for confirming negative margin status in even the most complex cases. Further evaluations may open the door for widespread use of this ICG-based FN system as a feasible and attractive alternative during a PN procedure.

The role of lymphatics in cancer as assessed by near-infrared fluorescence imaging

The lymphatic system is the secondary circulatory system responsible for fluid homeostasis and protein transport in the body. In addition, because the lymphatic system provides a primary pathway for cancer metastasis, lymph node involvement is routinely used as a determinant in cancer staging. Despite their importance, the lymphatics remain poorly understood, in part because of the historic lack of imaging modalities with sufficient spatial and/or temporal resolution to visualize the fine lymphatic structure and subtle contractile function. In recent years, near-infrared fluorescence (NIRF) imaging has emerged as a new imaging modality to non-invasively visualize the lymphatics and assess contractile lymphatic function in humans following administration of microdose amounts of a NIRF contrast agent. In this contribution, we first review NIRF imaging and its clinical application in sentinel lymph node mapping, intraoperative guidance, and assessing the architecture and contractile function of the lymphatics in health and in cancer-related lymphedema. We then present recent NIRF lymphatic imaging for non-invasive assessment of lymphatics both in preclinical melanoma models and in human subjects with melanoma.

Sentinel lymph node biopsy for breast cancer patients using fluorescence navigation with indocyanine green

BACKGROUND

There are various methods for detecting sentinel lymph nodes in breast cancer. Sentinel lymph node biopsy (SLNB) using a vital dye is a convenient and safe, intraoperatively preparative method to assess lymph node status. However, the disadvantage of the dye method is that the success rate of sentinel lymph node detection depend on the surgeon's skills and preoperative mapping of the sentinel lymph node is not feasible. Currently, a vital dye, radioisotope, or a combination of both is used to detect sentinel nodes. Many surgeons have reported successful results using either method. In this study we have analyzed breast lymphatic drainage pathways using indocyanine green (ICG) fluorescence imaging.

METHODS

We examined the lymphatic courses, or lymphatic vessels, in the breast using ICG fluorescence imaging, and applied this method to SLNB in patients who underwent their first operative treatment for breast cancer between May 2006 and April 2008. Fluorescence images were obtained using a charge coupled device camera with a cut filter used as a detector, and light emitting diodes at 760 nm as a light source. When ICG was injected into the subareola and periareola, subcutaneous lymphatic vessels from the areola to the axilla became visible by fluorescence within a few minutes. The sentinel lymph node was then dissected with the help of fluorescence imaging navigation.

RESULTS

The detection rate of sentinel nodes was 100%. 0 to 4 states of lymphatic drainage pathways from the areola were observed. The number of sentinel nodes was 3.41 on average.

CONCLUSIONS

This method using indocyanine green (ICG) fluorescence imaging may possibly improve the detection rate of sentinel lymph nodes with high sensitivity and compensates for the deficiencies of other methods. The ICG fluorescence imaging technique enables observation of breast lymph vessels running in multiple directions and easily and accurately identification of sentinel lymph nodes. Thus, this technique can be considered useful.

Breast cancer sentinel lymph node mapping using near infrared guided indocyanine green and indocyanine green--human serum albumin in comparison with gamma emitting radioactive colloid tracer

AIMS

Recently, a novel method of using near infrared (NIR) guided indocyanine green (ICG) and ICG conjugated with human serum albumin (ICG:HSA) for sentinel lymph node biopsy (SLNB) of breast cancer patients has shown true potential. The aim of this study was to compare the usefulness of NIR guided ICG and ICG:HSA against the gamma emitting radiocolloid (RC).

METHODS

A group of 49 consecutive breast cancer patients underwent SLNB using RC. From this group, the first 28 patients were compared against ICG, while the next 21 patients were compared against ICG:HSA. The number of patients with visible fluorescent path was recorded. Furthermore, the number of SLNs detected by fluorophores percutaneously and total number of intraoperative SLNs detected by fluorophores and/or RC was noted.

RESULTS

NIR guided real time lymphatic flow was observed in 47/49 patients (96%). In all cases except one, SLNs detected by the RC tracer were also detected by their respective fluorophore. Additionally, ICG detected 10 additional SLNs in 8 patients, while 3 additional SLNs were detected by ICG:HSA in 3 patients. Statistical analysis revealed no difference between the number of SLNs detected between ICG versus ICG:HSA and RC versus ICG:HSA. However, a significant statistical difference was observed between RC and ICG (p=0.0117), as well as between the combined NIR guided and RC method (p=0.0033).

CONCLUSIONS

In conclusion, the use of either ICG or ICG:HSA with RC to obtain SLNB seems to be an effective alternative. Compared to RC alone, the use of ICG:HSA, more so than ICG alone, may provide additional benefits.

Identification of lymphatic pathway involved in the spreading of prostate cancer by fluorescence navigation approach with intraoperatively injected indocyanine green

OBJECTIVE

: The objective of this study was to identify lymphatic vessels draining from the prostate by using a fluorescence navigation (FN) system.

METHODS

: Fourteen subjects were candidates for radical retropubic prostatectomy (RRP) and pelvic lymph node dissection (PLND). After an indocyanine green solution was injected into the prostate during RRP, lymphatic vessels draining from the prostate were analyzed using a FN system. After PLND based on lymphatic mapping by the FN system (in vivo probing) was performed in the external iliac, obturator and internal iliac regions; the fluorescence of the removed lymph nodes (LNs) was analyzed on the bench (ex vivo probing).

RESULTS

: Under in vivo and ex vivo probing, the fluorescence intensity of internal iliac nodes was greater than that of external iliac or obturator nodes.

CONCLUSION

: The current study suggests that using a FN system after injecting indocyanine green is a safe and rational approach for detecting the lymphatic channel draining from the prostate. The major lymphatic pathway involved in the spreading of prostate cancer appears to relate to internal iliac LNs, which would mean that the standard PLND covering external iliac and obturator regions would not keep the cancer from spreading.

Translation of near-infrared fluorescence imaging technologies: emerging clinical applications

Technical developments in near-infrared fluorescence (NIRF) imaging and tomography have enabled recent translation into investigational human studies. Noninvasive imaging of the lymphatic vasculature for diagnosis and assessment of function has been uniquely accomplished with NIR using indocyanine green (ICG), a nonspecific dye that has comparatively poor fluorescent properties compared to emerging dyes. Adjunct use of NIRF-ICG for (a) intraoperative sentinel lymph node mapping for cancer staging, (b) video-angiography during surgery, and (c) discrimination of malignant from benign breast lesions detected by mammography and ultrasongraphy also evidences the clinical utility of NIRF. Future NIRF imaging agents that consist of bright fluorescent dyes conjugated to disease-targeting moieties promise molecular imaging and image-guided surgery. In this review, emerging NIRF imaging is described within the context of nuclear imaging technologies that remain the "gold standard" of molecular imaging.

Noninvasive detection of breast cancer lymph node metastasis using carbonic anhydrases IX and XII targeted imaging probes

PURPOSE

To develop targeted molecular imaging probes for the noninvasive detection of breast cancer lymph node metastasis.

EXPERIMENTAL DESIGN

Six cell surface or secreted markers were identified by expression profiling and from the literature as being highly expressed in breast cancer lymph node metastases. Two of these markers were cell surface carbonic anhydrase isozymes (CAIX and/or CAXII) and were validated for protein expression by immunohistochemistry of patient tissue samples on a breast cancer tissue microarray containing 47 normal breast tissue samples, 42 ductal carcinoma in situ, 43 invasive ductal carcinomas without metastasis, 46 invasive ductal carcinomas with metastasis, and 49 lymph node macrometastases of breast carcinoma. Targeted probes were developed by conjugation of CAIX- and CAXII-specific monoclonal antibodies to a near-infrared fluorescent dye.

RESULTS

Together, these two markers were expressed in 100% of the lymph node metastases surveyed. Selectivity of the imaging probes were confirmed by intravenous injection into nude mice-bearing mammary fat pad tumors of marker-expressing cells and nonexpressing cells or by preinjection of unlabeled antibody. Imaging of lymph node metastases showed that peritumorally injected probes detected nodes harboring metastatic tumor cells. As few as 1,000 cells were detected, as determined by implanting, under ultrasound guidance, a range in number of CAIX- and CAXII-expressing cells into the axillary lymph nodes.

CONCLUSION

These imaging probes have potential for noninvasive staging of breast cancer in the clinic and elimination of unneeded surgery, which is costly and associated with morbidities.

Assessing intraoperative blood flow in cardiovascular surgery

Off-pump coronary arterial bypass grafting and new surgical apparatus and techniques have decreased the mortality rate associated with this procedure to approximately 1.5%. If we could detect problems in the constructed coronary anastomoses by an alternative imaging system to coronary angiography during surgery, decisions to revise the surgical procedure could be made without hesitation. Meanwhile, the intraoperative direct evaluation of intestinal blood flow during abdominal aortic aneurysmal surgery is required to prevent ischemic colitis, which is a devastating complication. Indocyanine green (ICG) has recently improved ophthalmic angiography and the navigation systems of oncological surgery. The fluorescence illumination of ICG with a near-infrared light is captured on camera. In coronary arterial surgery, the ICG imaging system is also becoming increasingly useful. A new ICG imaging system, the HyperEye Medical System (HEMS), provides a clear view of the blood flow and ischemic area with color visualization. Furthermore, its combination with a quantitative blood flow assessment tool such as transit time flow measurement could improve the accuracy of intraoperative examination. In this review, we evaluate the current strategies of assessing blood flow intraoperatively with an ICG imaging system in cardiovascular surgery.

The clinical use of indocyanine green as a near-infrared fluorescent contrast agent for image-guided oncologic surgery

Optical imaging using near-infrared (NIR) fluorescence provides new prospects for general and oncologic surgery. ICG is currently utilised in NIR fluorescence cancer-related surgery for three indications: sentinel lymph node (SLN) mapping, intraoperative identification of solid tumours, and angiography during reconstructive surgery. Therefore, understanding its advantages and limitations is of significant importance. Although non-targeted and non-conjugatable, ICG appears to be laying the foundation for more widespread use of NIR fluorescence-guided surgery.

High rate of solitary sentinel node metastases identification by fluorescence-guided lymphatic imaging in breast cancer

BACKGROUND

The lymph node status was shown to be an important prognostic factor for breast cancer, but controversial issues remain. There has been increased focus on optimizing the visualization of lymph nodes for an accurate and selective approach to axillary lymph nodes. Fluorescence-guided lymphatic imaging is a potential candidate for further research on remaining controversies.

METHODS

Forty-seven patients were subject to injection of indocyanine green for navigation to the SLN based on fluorescent dye retention detection. In two groups, patients either received intended axillary lymph node dissection (ALND) and sentinel lymph node biopsy (SLNB) for superstaging or isolated SLNB for minimal-invasive staging. The prospective study was designed to evaluate the technical feasibility with focus on solitary positive SLN.

RESULTS

Visualization of lymphatic vessels with bright fluorescence of the SLN was feasible in 46 of 47 patients. Eighteen of 19 nodal positive patients were correctly identified with a sensitivity of 94.7% in all patients after ALND. After immunohistochemistry, in 19 of 25 overall nodal positive patients (76%) the SLN was the only positive lymph node.

CONCLUSION

Fluorescence-guided imaging using fluorescence retention detection allows transcutaneous navigation with a high rate of solitary positive SLN identification as an alternative technique for further research.

Development of membrane type-1 matrix metalloproteinase-specific activatable fluorescent probe for malignant tumor detection

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a protease that activates pro-MMP-2 and pro-MMP13, which are related to tumor malignancy. Therefore, probes that specifically image MT1-MMP would be useful for malignant tumor diagnosis. In the present study, we prepared rhodamine X-conjugated anti-MT1- MMP antibody (anti-MT1-MMP mAb-ROX) as an activatable fluorescent probe and evaluated its usefulness for MT1-MMP-specific imaging. Anti-MT1-MMP mAb-ROX was obtained in a quenched form with approximately three ROX molecules per mAb. Its fluorescence intensity increased approximately 14-fold in the presence of detergent, which is suitable for activatable systems. C6 glioma cells and MCF-7 human breast adenocarcinoma cells were used as MT1-MMP-positive and MT1-MMP-negative models, respectively. The fluorescence intensity of C6 cells treated with anti-MT1-MMP mAb-ROX, but not ROX-conjugated isotype control antibody (NC Ab-ROX), increased with time and was significantly higher than that of MCF-7 cells at 6 h (P < 0.001). The fluorescence intensity of cells treated with anti-MT1-MMP mAb-ROX was also suppressed by pre-treatment with a MT1-MMP endocytosis inhibitor (P < 0.05). Furthermore, the probes were intravenously administered to C6 and MCF-7 xenografted mice. The tumor-to-muscle (T/M) ratio of the anti-MT1-MMP mAb-ROX group was 15.1 ± 3.2 at 48 h and was significantly higher than that of the NC Ab-ROX group (T/M ratio = 4.6 ± 3.0, P < 0.05) in C6 xenografted mice, while the T/M ratio of the anti-MT1-MMP mAb-ROX and NC Ab-ROX groups was not different in MCF-7 xenografted mice. These findings suggest that anti-MT1-MMP mAb-ROX is a promising probe for specifically detecting MT1-MMP-expressing tumors.

Usefulness of Tc-99m-GSA scintigraphy for liver surgery

Postoperative mortality remains high after hepatectomy compared with other types of surgery in patients who have cirrhosis or chronic hepatitis. Although there are several useful perioperative indicators of liver dysfunction, no standard markers are available to predict postoperative liver failure in patients with hepatocellular carcinoma (HCC) undergoing hepatectomy. The best preoperative method for evaluating the hepatic functional reserve of patients with HCC remains unclear, but technetium-99m diethylenetriamine pentaacetic acid galactosyl human serum albumin ((99m)Tc-GSA) scintigraphy is a candidate. (99m)Tc-GSA is a liver scintigraphy agent that binds to the asialoglycoprotein receptor, and can be used to assess the functional hepatocyte mass and thus determine the hepatic functional reserve in various physiological and pathological states. The maximum removal rate of (99m) Tc-GSA (GSA-Rmax) calculated by using a radiopharmacokinetic model is correlated with the severity of liver disease. There is also a significant difference of GSA-Rmax between patients with chronic hepatitis and persons with normal liver function. Regeneration of the remnant liver and recurrence of hepatitis C virus infection in the donor organ after living donor liver transplantation have also been investigated by (99m)Tc-GSA scintigraphy. This review discusses the usefulness of (99m)Tc-GSA scintigraphy for liver surgery.

Sentinel lymph node biopsy using intraoperative indocyanine green fluorescence imaging navigated with preoperative CT lymphography for superficial esophageal cancer

BACKGROUND

The sentinel lymph node (SLN) concept has been gaining attention for gastrointestinal neoplasms but remains controversial for esophageal cancer. This study evaluated the feasibility of SLN identification using intraoperative indocyanine green (ICG) fluorescence imaging (IGFI) navigated by preoperative computed tomographic lymphography (CTLG) to treat superficial esophageal cancer.

METHODS

Subjects comprised 20 patients clinically diagnosed with superficial esophageal cancer. Five minutes after endoscopic submucosal injection of iopamidol around the primary lesion using a four-quadrant injection pattern with a 23-gauge endoscopic injection sclerotherapy needle, three-dimensional multidetector computed tomography was performed to identify SLNs and lymphatic routes. ICG solution was injected intraoperatively around the tumor. Fluorescence imaging was obtained by infrared ray electronic endoscopy. Thoracoscope-assisted standard radical esophagectomy with lymphadenectomy was performed to confirm fluorescent lymph nodes detected by CTLG.

RESULTS

Lymphatic vessels and SLNs were identified preoperatively using CTLG in all cases. Intraoperative detection rates were 100% using CTLG and 95% using IGFI. Lymph node metastases were found in four cases, including one false-negative case with SLNs occupied by bulky metastatic tumor that were not enhanced with both methods. The other 19 cases, including three cases of metastatic lymph nodes, were accurately identified by both procedures.

CONCLUSIONS

Preoperative CTLG visualized the correct number and site of SLNs in surrounding anatomy during routine computed tomography to evaluate distant metastases. Referring to CTLG, SLNs were identified using IGFI, resulting in successful SLN navigation and saving time and cost. This method appears clinically applicable as a less-invasive method for treating superficial esophageal cancer.

Indocyanine green fluorescence monitoring of perineal wound contamination in abdominoperineal resection: a preliminary report

PURPOSE

Surgical site infections (SSI) in an abdominoperineal resection (APR) occur more frequently than in other types of operations for patients with colorectal cancer. Perineal wounds are the most vulnerable sites, and they may be caused by stool contamination. Indocyanine green (ICG) fluorescence imaging, by which sensitive detection was possible, was used as a marker of perineal wound contamination.

METHOD

Indocyanine green was transanally injected to the rectum before operation, and fluorescence images were obtained during the operation in three patients who underwent APR.

RESULTS

One subject, in whom gross contamination was not visible, had an SSI, and a trace of ICG fluorescence was detectable in the perianal skin. The other two subjects, in whom skin preparation was completely performed until ICG contamination was eliminated, were free from SSI.

CONCLUSIONS

Our results suggested that a trace of stool contamination remained in the perineal skin field even after the usual antiseptic skin preparation. Furthermore, meticulous skin preparation is required to minimize stool contamination in APR patients.

Transcutaneous detection and direct approach to the sentinel node using axillary compression technique in ICG fluorescence-navigated sentinel node biopsy for breast cancer

BACKGROUND

Indocyanine green (ICG) fluorescence navigation is a useful option in sentinel node biopsy (SNB) for breast cancer. However, several technical difficulties still exist. Since the sentinel node (SN) cannot be recognized over the skin, subcutaneous lymphatic vessels (LVs) must be carefully dissected without injury. In addition, the dissecting procedures are often interrupted by turning off the operating light during fluorescence observation. In this report, we introduce a new approach using the axillary compression technique to overcome these problems.

MATERIALS AND METHODS

In the original procedure of the ICG fluorescence method, the subcutaneous lymphatic drainage pathway from the breast to the axilla was observed in fluorescence images, but no signal could be obtained in the axilla. When the axillary skin was compressed against the chest wall using a plastic device, the signals from the deeper lymphatic structures could be observed. By tracing the compression-inducible fluorescence signal towards the axilla, transcutaneous detection and direct approach to the SN were achieved. The benefit of this approach is that there is no risk of injury of LVs, and the procedures are interrupted less frequently by fluorescence observation. The axillary compression technique was used in 50 patients with early breast cancer.

RESULTS

SNs were successfully removed in all patients. Transcutaneous detection and direct approach were possible in 47 patients. This approach was also effective in obese patients.

CONCLUSIONS

Axillary compression technique is a simple way to facilitate the surgical procedures of ICG fluorescence-navigated SNB for breast cancer.

Near infrared fluorescence-guided real-time endoscopic detection of peritoneal ovarian cancer nodules using intravenously injected indocyanine green

Near infrared fluorescence-guidance can be used for the detection of small cancer metastases and can aid in the endoscopic management of cancer. Indocyanine green (ICG) is a Food and Drug Administration (FDA)-approved fluorescence agent. Through non-specific interactions with serum proteins, ICG achieves enhanced permeability and retention (EPR) effects. Yet, ICG demonstrates rapid clearance from the circulation. Therefore, ICG may be an ideal contrast agent for real-time fluorescence imaging of tumors. To evaluate the usefulness of real-time dual fluorescence and white light endoscopic optical imaging to detect tumor implants using the contrast agent ICG, fluorescence-guided laparoscopic procedures were performed in mouse models of peritoneally disseminated ovarian cancers. Animals were administered intravenous ICG or a control contrast agent, IR800-conjugated to albumin. The ability to detect small ovarian cancer implants was then compared. Using the dual view microendoscope, ICG clearly enabled visualization of peritoneal ovarian cancer metastatic nodules derived from SHIN3 and OVCAR5 cells at 6 and 24 hr after injection with significantly higher tumor-to-background ratio than the control agent, IR800-albumin (p < 0.001). In conclusion, ICG has the desirable properties of having both EPR effects and rapid clearance for the real-time endoscopic detection of tiny ovarian cancer peritoneal implants compared to a control macromolecular agent with theoretically better EPR effects but longer circulatory retention. Given that ICG is already FDA-approved and has a long track record of human use, this method could be easily translated to the clinic as a robust tool for fluorescence-guided endoscopic procedures for the management and treatment of cancer.

Enhancement of the photostability and retention time of indocyanine green in sentinel lymph node mapping by anionic polyelectrolytes

Sentinel lymph node (SLN) biopsy techniques have been widely used in the diagnosis of cancer metastasis because lymph node metastasis is one of the most important prognostic signs. Indocyanine green (ICG) has potential application as a molecular imaging probe for SLN mapping due to its fluorescent properties emitting in the near-infrared (NIR) region, where light transmission through biological tissue is maximized. However, its low photostability in an aqueous solution at the physiological temperature and its rapid diffusion behavior through SLN into the second lymph node have limited its wide use in real clinical fields. In this study, we developed a new NIR imaging contrast system consisting of ICG and poly (γ-glutamic acid) (γ-PGA) polymers for efficient sentinel lymph node mapping. By a combination of clinically used ICG and the biocompatible anionic polyelectrolyte, γ-PGA, the photostabilities of aqueous ICG solutions at room and body temperatures were drastically enhanced. When the ICG/γ-PGA complex was injected subcutaneously into the front paw of a mouse, it entered the lymphatics and migrated to the axillary sentinel lymph node (SLN) within 2 min. Furthermore, the NIR fluorescent signal intensity and retention time of ICG/γ-PGA complex in lymph node were superior to those of ICG only. In addition, a histofluorescentstudy of the SLN resected under NIR imaging revealed that ICG and γ-PGA were co-localized in the lymph node.Taken together, the experimental results on the enhanced photostability and retention time of the ICG/γ-PGA complex provide strong evidence that it has promising potential for improved sentinel lymph node mapping.

A novel approach for sentinel lymph node identification using fluorescence imaging and image overlay navigation surgery in patients with breast cancer

BACKGROUND

We reported a novel technique of sentinel lymph node (SLN) identification using fluorescence imaging of indocyanine green injection. Furthermore, to obtain safe and accurate identification of SLN during surgery, we introduce the image overlay navigation surgery and evaluate its efficacy.

METHODS

This study enrolled 50 patients with a tumors <2 cm in diameter. Initially, we obtained three-dimensional (3-D) imaging from multidetector-row computed tomography (MD-CT) by volume rendering. It was projected on the patient's operative field with the clear visualization of lymph node (LN) through projector. Then, the dye of indocyanine green (ICG) was injected subdermally in the areola. Subcutaneous lymphatic channels draining from the areola to the axilla were visible by fluorescence imaging immediately. Lymphatic flow was reached after LN revealed on 3-D imaging. After incising the axillary skin on the point of LN mapping, SLN was then dissected under the guidance of fluorescence imaging with adequate adjustment of sensitivity and 3-D imaging.

RESULTS

Lymphatic channels and SLN were successfully identified by Photodynamic eye (PDE) in all patients. And the sites of skin incision also were identical with the LN being demonstrated by 3-D imaging in all patients. The mean number of SLN was 3.7. The image overlay navigation surgery was visually easy to identify the location of SLN from the axillary skin. There were no intra- or postoperative complications associated with SLN identification.

CONCLUSIONS

This combined navigations of fluorescence and 3-D imaging revealed more easy and effective to detect SLN intraoperatively than fluorescence imaging alone.

Randomized, double-blind comparison of indocyanine green with or without albumin premixing for near-infrared fluorescence imaging of sentinel lymph nodes in breast cancer patients

Near-infrared (NIR) fluorescence imaging has the potential to improve sentinel lymph node (SLN) mapping in breast cancer. Indocyanine green (ICG) is currently the only clinically available fluorophore that can be used for SLN mapping. Preclinically, ICG adsorbed to human serum albumin (ICG:HSA) improves its performance as a lymphatic tracer in some anatomical sites. The benefit of ICG:HSA for SLN mapping of breast cancer has not yet been assessed in a clinical trial. We performed a double-blind, randomized study to determine if ICG:HSA has advantages over ICG alone. The primary endpoint was the fluorescence brightness, defined as the signal-to-background ratio (SBR), of identified SLNs. Clinical trial subjects were 18 consecutive breast cancer patients scheduled to undergo SLN biopsy. All patients received standard of care using (99m)Technetium-nanocolloid and patent blue. Patients were randomly assigned to receive 1.6 ml of 500 μM ICG:HSA or ICG that was injected periareolarly directly after patent blue. The Mini-Fluorescence-Assisted Resection and Exploration (Mini-FLARE) imaging system was used for NIR fluorescence detection and quantitation. SLN mapping was successful in all patients. Patient, tumor, and treatment characteristics were equally distributed over the treatment groups. No significant difference was found in SBR between the ICG:HSA group and the ICG alone group (8.4 vs. 11.3, respectively, P = 0.18). In both groups, the average number of detected SLNs was 1.4 ± 0.5 SLNs per patient (P = 0.74). This study shows that there is no direct benefit of premixing ICG with HSA prior to injection for SLN mapping in breast cancer patients, thereby reducing the cost and complexity of the procedure. With these optimized parameters that eliminate the necessity of HSA, larger trials can now be performed to determine patient benefit.

Current trends and emerging future of indocyanine green usage in surgery and oncology: a literature review

Ever since Kitai first performed fluorescent navigation of sentinel lymph nodes (SLNs) using indocyanine green (ICG) dye with a charge-couple device and light emitting diodes, the intraoperative use of near infrared fluorescence has served a critical role in increasing our understanding in various fields of surgical oncology. Here the authors review the emerging role of the ICG fluorophore in the development of our comprehension of the lymphatic system and its use in SLN mapping and biopsy in various cancers. In addition, they introduce the novel role of ICG-guided video angiography as a new intraoperative method of assessing microvascular circulation. The authors attempt to discuss the promising potential in addition to assessing several challenges and limitations in the context of specific surgical procedures and ICG as a whole. PubMed and Medline literature databases were searched for ICG use in clinical surgical settings. Despite ICG's significant impact in various fields of surgical oncology, ICG is still in its nascent stages, and more in-depth studies need to be carried out to fully evaluate its potential and limitations.

Sentinel node biopsy in breast cancer using infrared laser system first experience with PDE camera

BACKGROUND

Sentinel node biopsy (SNB) is a gold standard in staging of early breast cancer. Nowadays, routine mapping of lymphatic tract is based on two tracers: human albumin with radioactive technetium, with or without blue dye. Recent years have seen a search for new tracers to examine sentinel node as well as lymphatic network. One of them is indocyanine green (ICG) visible in infrared light.

AIM

The aim of this study is to evaluate clinical usage of ICG in comparison with standard tracer, i.e. nanocoll, in SNB of breast cancer patients.

MATERIALS AND METHODS

In the 1st Department of Surgical Oncology and General Surgery, Greater Poland Cancer Centre, Poznań, 13 female breast cancer patients have benn operated since September 2010. All these patients had sentinel node biopsy with nanocoll (human albumin with radioactive technetium), and with indocyanine green. The feasibility of this new method was assessed in comparison with the standard nanocoll.

RESULTS

A lymphatic network between the place of injection of ICG and sentinel node was seen in infrared light. An area where a sentinel node was possibly located was confirmed by gamma probe. Sensitivity of this method was 100%.

CONCLUSION

SNB using ICG is a new, promising diagnostics technique. This procedure is not without drawbacks; nevertheless it opens new horizons in lymphatic network diagnostics.

Identifying gaps in the locoregional management of early breast cancer: highlights from the Kyoto Consensus Conference

A consensus conference was held to investigate issues related to the local management of early breast cancer. Here, we highlight the major topics discussed at the conference and propose ideas for future studies. Regarding axillary management, we examined three major issues. First, we discussed whether the use of axillary reverse mapping could clarify the lymphatic system of breast and whether the ipsilateral arm might help avoid lymphedema. Second, the use of an indocyanine green fluorescent navigation system was discussed for intraoperative lymphatic mapping. These new issues should be examined further in practice. Finally, some agreement was reached on the importance of "four-node diagnosis" to aid in the diagnostic accuracy of sentinel nodes. Regarding breast treatment, there was general agreement that the clinical value of surgical margins in predicting local failure was dependent on the tumor's intrinsic biology and subtypes. For patients treated with preoperative chemotherapy, less extensive excision may be feasible in those who respond to systemic therapy in an acceptable manner. Most trials of preoperative chemotherapy lack outcome data on local recurrence. Therefore, there is a need for such data for overview analysis. We also agreed that radiation after mastectomy may be beneficial in node-positive cases where more than four nodes are involved. Throughout the discussions for both invasive and noninvasive disease, the investigation of nomograms was justified for major issues in the decision-making process, such as the presence or absence of microinvasion and the involvement of nonsentinel nodes in sentinel node-positive patients.

Tracer agents for the detection of sentinel lymph nodes in breast cancer: current concerns and directions for the future

Tracer agents play a central role in axillary lymphatic mapping for sentinel node identification during breast cancer surgery. This article reviews the data concerning safety, efficacy, and availability of tracers currently in use. Alternate tracer materials are introduced, with review of the current literature.

Toward optimization of imaging system and lymphatic tracer for near-infrared fluorescent sentinel lymph node mapping in breast cancer

Background

Near-infrared (NIR) fluorescent sentinel lymph node (SLN) mapping in breast cancer requires optimized imaging systems and lymphatic tracers.

Materials and Methods

A small, portable version of the FLARE imaging system, termed Mini-FLARE, was developed for capturing color video and two semi-independent channels of NIR fluorescence (700 and 800 nm) in real time. Initial optimization of lymphatic tracer dose was performed using 35-kg Yorkshire pigs and a 6-patient pilot clinical trial. More refined optimization was performed in 24 consecutive breast cancer patients. All patients received the standard of care using ^99mTechnetium-nanocolloid and patent blue. In addition, 1.6 ml of indocyanine green adsorbed to human serum albumin (ICG:HSA) was injected directly after patent blue at the same location. Patients were allocated to 1 of 8 escalating ICG:HSA concentration groups from 50 to 1000 μM.

Results

The Mini-FLARE system was positioned easily in the operating room and could be used up to 13 in. from the patient. Mini-FLARE enabled visualization of lymphatic channels and SLNs in all patients. A total of 35 SLNs (mean = 1.45, range 1–3) were detected: 35 radioactive (100%), 30 blue (86%), and 35 NIR fluorescent (100%). Contrast agent quenching at the injection site and dilution within lymphatic channels were major contributors to signal strength of the SLN. Optimal injection dose of ICG:HSA ranged between 400 and 800 μM. No adverse reactions were observed.

Conclusions

We describe the clinical translation of a new NIR fluorescence imaging system and define the optimal ICG:HSA dose range for SLN mapping in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1245/s10434-011-1566-x) contains supplementary material, which is available to authorized users.

Single-dose intravenous toxicity study of IRDye 800CW in Sprague-Dawley rats

Objective

Fluorophore-labeled contrast imaging agents are moving toward clinical use for a number of applications. The near-infrared dye IRDye 800CW is frequently used in its N-hydroxysuccinamide (NHS) ester form for labeling these agents. Following conjugation or breakdown of a labeled ligand, excess NHS ester is converted to the carboxylate form. To prepare for clinical use as a near-infrared fluorophore, a toxicity study was conducted on IRDye 800CW carboxylate.

Methods

Male and female Sprague–Dawley rats were given a single intravenous or intradermal administration of IRDye 800CW carboxylate; Indocyanine Green was used as a comparative control. Animals were injected with varying doses of the test and control articles and observed for up to 14 days. Clinical chemistry, hematological, and pharmacokinetic analyses were performed on subgroups of animals. Organs were analyzed for content of the test article. Tissues were analyzed microscopically for pathological changes.

Results

Based on hematologic, clinical chemistry, and histopathologic evaluation, single administration of IRDye 800CW carboxylate intravenously at dose levels of 1, 5, and 20 mg/kg or 20 mg/kg intradermally produced no pathological evidence of toxicity.

Conclusion

A dose of 20 mg/kg was identified as the no observed adverse effect level following IV or ID routes of administration of IRDye 800CW.

Electronic supplementary material

The online version of this article (doi:10.1007/s11307-010-0317-x) contains supplementary material, which is available to authorized users.

Feasibility of ICG fluorescence-guided sentinel node biopsy in animal models using the HyperEye Medical System

BACKGROUND

The sentinel lymph node (SLN) concept is accepted for several types of cancers. Current methods for sentinel node detection involve radioisotopes and blue dye. They have shown good results, but some drawbacks remain. Indocyanine green (ICG) fluorescence using the HyperEye Medical System (HEMS) was evaluated as a new method.

METHODS

This was a prospective, nonrandomized, experimental study in four Japanese white rabbits and six Yorkshire pigs. ICG and indigo carmine were injected into the tongue, larynx, or hypopharynx, and ICG fluorescence detection was evaluated using both transcutaneous visualization of lymphatic vessels and intraoperative identification of SLNs.

RESULTS

The SLNs appeared as shining fluorescent spots with HEMS transcutaneously in rabbits, but no SLNs were detected transcutaneously in pigs. Eleven procedures identified SLNs, but one did not due to a technical problem.

CONCLUSIONS

HEMS could become useful for predicting lymph node metastasis during surgery for head and neck cancer.

Indocyanine green fluorescence imaging system for sentinel lymph node biopsies in early breast cancer patients

PURPOSE

This study presents a new method that enables the detection of sentinel lymph nodes (SLN) with high sensitivity using indocyanine green (ICG) fluorescence imaging.

METHODS

This study enrolled 128 patients with clinically node-negative breast cancer. Fluorescence imaging was obtained after ICG was injected into the areola. Subcutaneous lymphatic channels were immediately visible.

RESULTS

Lymphatic channels and SLN were successfully visualized in all patients. One lymphatic channel was 60%, two channels were 24%, and three channels were 16%. The number of fluorescence SLN ranged from 1 to 6, and blue-dyed SLN ranged from 0 to 3. In the latter, SLN were not identified in 44 patients. Nineteen patients had pathologically identified lymph node metastases. All of them were recognized by fluorescence imaging, but 8 patients had lymph nodes with metastases were not identified by dye method.

CONCLUSION

This ICG fluorescence imaging technique is feasible and safe for detecting SLN in a less invasive manner than conventional mapping, with real-time observations.

Usefulness of blood supply visualization by indocyanine green fluorescence for reconstruction during esophagectomy

BACKGROUND: Adequate blood supply for the reconstructed organ is important for safe esophagogastric anastomosis during esophagectomy. Recently, indocyanine green (ICG) has been used for visualization of the blood supply when anastomosis is performed in vascular surgery. To visualize the blood supply for reconstruction, we employed ICG fluorescence during esophagectomy. METHODS: From August 2008, 40 patients received cervical or thoracic esophagectomy. They consisted of 33 patients having esophagectomy for thoracic esophageal cancer, 3 being treated for cervical esophageal cancer, and 4 with double cancer of the thoracic and cervical regions. Before and after pulling up the reconstructed organ, 2.5 mg of ICG was injected as a bolus. Then ICG fluorescence was detected by a camera and recorded. RESULTS: ICG fluorescence was easily detected in all patients at 1 min after injection. The vascular network was well visualized in the gastric wall, colonic grafts, and free jejunal grafts. In five patients, we also performed anastomosis between the short gastric vein and the external cervical vein or superficial cervical vein. The intraoperative and postoperative course of all patients was uneventful apart from three anastomotic leakages. CONCLUSIONS: ICG fluorescence can be employed to evaluate the blood supply to reconstructed organs and can be useful in selecting the patients who do not need additional vessel anastomosis. However, anastomotic leakage was not reduced, so the microcirculation detected by ICG fluorescence did not necessarily provide appropriate blood supply for a viable anastomosis.

New fluorescence endoscope for use in twin-twin transfusion syndrome: in vivo visualization of placental blood vessels

Twin-twin transfusion syndrome (TTTS) is a condition in which twins share blood disproportionately by the communicating vessels in the shared placenta, resulting in high fetal and perinatal mortality. Fetoscopic laser photocoagulation is performed to interrupt these communicating vessels; however, small vessels are often missed due to the poor image obtained with a fetoscope. We have developed a fluorescence endoscope capable of visualizing very small vessels, even in amniotic fluid, and we investigated its feasibility for in vivo visualization of placental vessels. Indocyanine green (ICG) was given at single doses of 0.5, 1.0, and 1.5 mg/kg, respectively, into the maternal circulation of pregnant rabbits, and the endoscope was used to identify the placental vessels. The vessels were detected within 15s after ICG injection for about 10 min. The brightness difference between the intervillous space and the umbilical vessels was significantly smaller after administration of 0.5 mg/kg than after 1.0 mg/kg (p=0.02) or 1.5 mg/kg (p=0.01). Even very small vessels (0.2mm in diameter) were detected. In conclusion, our new endoscope successfully provided a detailed view of the placental vessels in vivo. The results are promising for future TTTS laser surgery.

(Non-targeted) radioactive/fluorescent nanoparticles and their potential in combined pre- and intraoperative imaging during sentinel lymph node resection

One clinical precedent for the use of nanosized imaging agents is the localization of the tumor draining sentinel lymph nodes. In this application, radiocolloids such as (99m)Tc-NanoColl are currently used to plan the surgical procedure and to provide acoustic guidance during the intervention. Additional injections of dyes are common to provide optical surgical guidance. Bimodal imaging agents, which are both radioactive and fluorescent, have the potential to be used for both surgical planning and intraoperative fluorescence guidance towards the sentinel lymph nodes. This review provides an overview of the radioactive, fluorescent, and size properties of (non-targeted) bimodal nanoparticles, and their (potential) value in sentinel lymph node detection.

Clinical translation of ex vivo sentinel lymph node mapping for colorectal cancer using invisible near-infrared fluorescence light

Background

Sentinel lymph node (SLN) mapping in colorectal cancer may have prognostic and therapeutic significance; however, currently available techniques are not optimal. We hypothesized that the combination of invisible near-infrared (NIR) fluorescent light and ex vivo injection could solve remaining problems of SLN mapping in colorectal cancer.

Methods

The FLARE imaging system was used for real-time identification of SLNs after injection of the NIR lymphatic tracer HSA800 in the colon and rectum of (n = 4) pigs. A total of 32 SLN mappings were performed in vivo and ex vivo after oncologic resection using an identical injection technique. Guided by these results, SLN mappings were performed in ex vivo tissue specimens of 24 consecutive colorectal cancer patients undergoing resection.

Results

Lymph flow could be followed in real-time from the injection site to the SLN using NIR fluorescence. In pigs, the SLN was identified in 32 of 32 (100%) of SLN mappings under both in vivo and ex vivo conditions. Clinically, SLNs were identified in all patients (n = 24) using the ex vivo strategy within 5 min after injection of fluorescent tracer. Also, 9 patients showed lymph node involvement (N1 disease). In 1 patient, a 3-mm mesenteric metastasis was found adjacent to a tumor-negative SLN.

Conclusions

The current pilot study shows proof of principle that ex vivo NIR fluorescence-guided SLN mapping can provide high-sensitivity, rapid, and accurate identification of SLNs in colon and rectum. This creates an experimental platform to test optimized, non-FDA-approved NIR fluorescent lymphatic tracers in a clinical setting.

Intraoperative near-infrared fluorescence imaging for sentinel lymph node detection in vulvar cancer: first clinical results

OBJECTIVE

Disadvantages of the combined sentinel lymph node (SLN) procedure with radiocolloid and blue dye in vulvar cancer are the preoperative injections of radioactive tracer in the vulva, posing a painful burden on the patient. Intraoperative transcutaneous imaging of a peritumorally injected fluorescent tracer may lead to a one-step procedure, while maintaining high sensitivity. Aim of this pilot study was to investigate the applicability of intraoperative fluorescence imaging for SLN detection and transcutaneous lymphatic mapping in vulvar cancer.

METHODS

Ten patients with early stage squamous cell carcinoma of the vulva underwent the standard SLN procedure. Additionally, a mixture of 1 mL patent blue and 1 mL indocyanin green (ICG; 0.5 mg/mL) was injected immediately prior to surgery, with the patient under anesthesia. Color and fluorescence images and videos of lymph flow were acquired using a custom-made intraoperative fluorescence camera system. The distance between skin and femoral artery was determined on preoperative CT-scan as a measure for subcutaneous adipose tissue.

RESULTS

In 10 patients, SLNs were detected in 16 groins (4 unilateral; 6 midline tumors). Transcutaneous lymphatic mapping was possible in five patients (5 of 16 groins), and was limited to lean patients, with a maximal distance between femoral artery and skin of 24 mm, as determined on CT. In total, 29 SLNs were detected by radiocolloid, of which 26 were also detected by fluorescence and 21 were blue.

CONCLUSIONS

These first clinical results indicate that intraoperative transcutaneous lymphatic mapping using fluorescence is technically feasible in a subgroup of lean vulvar cancer patients.

Laparoscopic detection of sentinel node in gastric cancer surgery by indocyanine green fluorescence imaging

BACKGROUND

Indocyanine green (ICG) fluorescence imaging is a promising technique for detection of sentinel node (SN) as it avoids unnecessary resection. However, the ICG fluorescence imaging system cannot be used in laparoscopic surgery because of technological difficulties.

METHODS

A prototype laparoscopic detection system comprising an electron multiplier charge-coupled device (EM-CCD) as the detector and a xenon lamp as the light source was developed. The CCD camera head was attached to the end of a specially designed laparoscope that could transmit ICG fluorescence. The system allows visualization of both color and fluorescence images. Laparoscopic surgery in ten patients with gastric cancer included SN biopsy using ICG dye, ICG fluorescence images using our system, and laparoscopy-assisted gastrectomy (LAG) with lymphadenectomy. SNs were sliced into 2-mm sections for histological examination and imprint cytology.

RESULTS

Immediately after intraoperative ICG injection by endoscopy, the laparoscopic ICG fluorescence imaging system allowed easy visualization of the lymphatic vessels draining from the primary gastric tumor toward the lymph nodes and traced the moving injected dye, whereas lymph vessels and nodes were hardly recognized by ICG green color through a standard laparoscope. Surgeons could confirm the removed lymph nodes stained with ICG by fluorescent imaging. SNs were successfully detected in all patients. Three patients had suspicious metastases in the SNs; two patients had lymph node metastases only in the SNs.

CONCLUSIONS

Our newly developed laparoscopic ICG fluorescence imaging system is promising in the detection of SNs in laparoscopic gastric cancer surgery. The preliminary results suggest an easier and shorter learning curve of dye-guided SN biopsy in laparoscopic gastric surgery.

Image-guided tumor resection using real-time near-infrared fluorescence in a syngeneic rat model of primary breast cancer

Tumor involvement of resection margins is found in a large proportion of patients who undergo breast-conserving surgery. Near-infrared (NIR) fluorescence imaging is an experimental technique to visualize cancer cells during surgery. To determine the accuracy of real-time NIR fluorescence imaging in obtaining tumor-free resection margins, a protease-activatable NIR fluorescence probe and an intraoperative camera system were used in the EMR86 orthotopic syngeneic breast cancer rat model. Influence of concentration, timing and number of tumor cells were tested in the MCR86 rat breast cancer cell line. These variables were significantly associated with NIR fluorescence probe activation. Dosing and tumor size were also significantly associated with fluorescence intensity in the EMR86 rat model, whereas time of imaging was not. Real-time NIR fluorescence guidance of tumor resection resulted in a complete resection of 17 out of 17 tumors with minimal excision of normal healthy tissue (mean minimum and a mean maximum tumor-free margin of 0.2 ± 0.2 mm and 1.3 ± 0.6 mm, respectively). Moreover, the technique enabled identification of remnant tumor tissue in the surgical cavity. Histological analysis revealed that the NIR fluorescence signal was highest at the invasive tumor border and in the stromal compartment of the tumor. In conclusion, NIR fluorescence detection of breast tumor margins was successful in a rat model. This study suggests that clinical introduction of intraoperative NIR fluorescence imaging has the potential to increase the number of complete tumor resections in breast cancer patients undergoing breast-conserving surgery.

A self-assembled multimodal complex for combined pre- and intraoperative imaging of the sentinel lymph node

Specific removal of the sentinel lymph node (SLN) during breast cancer surgery presents physicians with the opportunity to detect early metastatic disease. To increase the accuracy of intraoperative SLN detection, new methods with higher sensitivity and specificity are required. We have quantitatively compared conventional preoperative lymphoscintigraphy with albumin radiocolloids ((99m)Tc-NanoColl) with optical intraoperative guidance using the near infrared dye indocyanine green (ICG) in an orthotopic mouse model for metastatic breast cancer. Furthermore, we have applied a self-assembled multimodal complex, in which ICG is non-covalently bound to the albumin radiocolloid, to attain identical dynamics of the radioactive and optical components. The SLN specificity of the multimodal complex is similar to conventional lymphoscintigraphy, while the fluorescent signal-to-noise ratio is improved by 86% compared to ICG alone. In addition, the multimodal complex permits scintigraphic validation of the fluorescent findings. The multimodal ICG-(99m)Tc-NanoColl complex can be used both for lymphoscintigraphy by preoperative single photon emission computed tomography/computed tomography and for surgical navigation by intraoperative fluorescence imaging.

Tumor bracketing and safety margin estimation using multimodal marker seeds: a proof of concept

Accurate tumor excision is crucial in the locoregional treatment of cancer, and for this purpose, surgeons often rely on guide wires or radioactive markers for guidance toward the lesion. Further improvement may be obtained by adding optical guidance to currently used methods, in the form of intra-operative fluorescence imaging. To achieve such a multimodal approach, we have generated markers that can be used in a pre-, intra-, and post-operative setting, based on a cocktail of a dual-emissive inorganic dye, lipids, and pertechnetate. Phantom experiments demonstrate that these seeds can be placed accurately around a surrogate tumor using ultrasound. Three-dimensional bracketing provides delineation of the entire lesion. Combined with the multimodal nature, this provides the opportunity to predetermine the resection margins by validating the placement accuracy using multiple imaging modalities (namely, x ray, MRI, SPECT/CT, and ultrasound). The dual-emissive fluorescent properties of the dye provide the unique opportunity to intra-operatively estimate the depth of the seed in the tissue via multispectral imaging: emission green λmax=520 nm≤5 mm penetration versus emission red λmax=660 nm≤12 mm penetration. By using particles with different colors, the original geographic orientation of the excised tissue can be determined.

Visualized sclerotherapy of varicose veins

BACKGROUND

The spread and movement of sclerosant after injection during sclerotherapy is difficult to monitor.

OBJECTIVE

To develop a new visualization method that allows monitoring of sclerosant dosage and flow during sclerotherapy.

METHODS

We used a photodynamic eye (PDE) to perform indocyanine green (ICG) imaging. ICG produces strong fluorescence detectable using PDE and allows monitoring of sclerosant spread through blood vessels in real time. We performed visualized sclerotherapy on 50 limbs, comprising high ligation and sclerotherapy (35 limbs), stripping and sclerotherapy (10 limbs), and sclerotherapy alone (5 limbs).

RESULTS

In all cases, fluorescence imaging of the injected sclerosant was possible. No complications resulted from combining ICG and polidocanol in any of the patients, all of whom received follow-up evaluations at 1 week, 1 month, and 3 months after treatment.

CONCLUSIONS

Our new method not only avoids the risk of radiation exposure, but also allows for simple observation of sclerosant range of access, determination of the dosage for each lesion, and accurate administration of therapy to target lesions. This method will contribute to further advances in sclerotherapy, given that it allows administration of sclerosant and visual confirmation of optimal injection dosage, speed, and movement of sclerosant after injection. The authors have indicated no significant interest with commercial supporters.

Sentinel lymph nodes in the rat: noninvasive photoacoustic and US imaging with a clinical US system

PURPOSE

To evaluate in vivo sentinel lymph node (SLN) mapping by using photoacoustic and ultrasonographic (US) imaging with a modified clinical US imaging system.

MATERIALS AND METHODS

Animal protocols were approved by the Animal Studies Committee. Methylene blue dye accumulation in axillary lymph nodes of seven healthy Sprague-Dawley rats was imaged by using a photoacoustic imaging system adapted from a clinical US imaging system. To investigate clinical translation, the imaging depth was extended up to 2.5 cm by adding chicken or turkey breast on top of the rat skin surface. Three-dimensional photoacoustic images were acquired by mechanically scanning the US transducer and light delivery fiber bundle along the elevational direction.

RESULTS

Photoacoustic images of rat SLNs clearly help visualization of methylene blue accumulation, whereas coregistered photoacoustic/US images depict lymph node positions relative to surrounding anatomy. Twenty minutes following methylene blue injection, photoacoustic signals from SLN regions increased nearly 33-fold from baseline signals in preinjection images, and mean contrast between SLNs and background tissue was 76.0 +/- 23.7 (standard deviation). Methylene blue accumulation in SLNs was confirmed photoacoustically by using the optical absorption spectrum of the dye. Three-dimensional photoacoustic images demonstrate dynamic accumulation of methylene blue in SLNs after traveling through lymph vessels.

CONCLUSION

In vivo photoacoustic and US mapping of SLNs was successfully demonstrated with a modified clinical US scanner. These results raise confidence that photoacoustic and US imaging can be used clinically for accurate, noninvasive imaging of SLNs for axillary lymph node staging in breast cancer patients.

Real-time optical imaging using quantum dot and related nanocrystals

Biomedical optical imaging is rapidly evolving because of its desirable features of rapid frame rates, high sensitivity, low cost, portability and lack of radiation. Quantum dots are attractive as imaging agents owing to their high brightness, and photo- and bio-stability. Here, the current status of in vitro and in vivo real-time optical imaging with quantum dots is reviewed. In addition, we consider related nanocrystals based on solid-state semiconductors, including upconverting nanoparticles and bioluminescence resonance energy transfer quantum dots. These particles can improve the signal-to-background ratio for real-time imaging largely by suppressing background signal. Although toxicity and biodistribution of quantum dots and their close relatives remain prime concerns for translation to human imaging, these agents have many desirable features that should be explored for medical purposes.