Intraoperative near-infrared fluorescence imaging and spectroscopy identifies residual tumor cells in wounds

Use of near-infrared fluorescence angiography with indocyanine green to evaluate direct cutaneous arteries used for canine axial pattern flaps

OBJECTIVE

To describe the use of near-infrared angiography (NIRFA) to identify the vascularization of three canine axial pattern flaps (APFs) omocervical (OMO), thoracodorsal (THO), and caudal superficial epigastric (CSE); to establish a vascular fluorescence pattern (VFP) grading system; and to evaluate the effect of NIRFA on surgeon flap dimension planning compared to traditional landmark palpation (LP) and visualization assessments.

STUDY DESIGN

Experimental study.

ANIMALS

A total of 15 healthy, client-owned dogs.

METHODS

Dogs were sedated and flap sites were clipped. LP-based margins were drawn and preinjection images were recorded. Indocyanine green (ICG) was administered and VFP images were recorded. VFP scores were determined by five surgeons. Margin alterations were performed based on NIRFA-ICG images. Altered measurements were compared between LP and NIRFA-ICG images.

RESULTS

Vascularization of the CSE flap was most visible with NIRFA with VFP scores 4/4 for 13/15 dogs. Intersurgeon agreement for VFP grades was poorest for THO (ICC = 0.35) and intermediate for OMO (ICC = 0.49) flaps. Surgeons were more likely to adjust dimensions for CSE flaps relative to OMO (OR 17.3, 95% CI: 6.2, 47.8) or THO (25.5; 8.6, 75.7).

CONCLUSION

Using a grading system, we demonstrated that the CSE flap was most visible. Surgeons were more likely to adjust the LP-CSE flap margins based on fluorescence patterns and were more likely to rely on LP when visualization scores were low.

CLINICAL SIGNIFICANCE

NIRFA has possible applications identifying some direct cutaneous arteries of APFs and their associated angiosomes in real-time. Further investigation is indicated to study NIRFA's potential to improve patient specific APF planning.

Mechanisms of delayed indocyanine green fluorescence and applications to clinical disease processes

BACKGROUND

Delayed indocyanine green fluorescence imaging is under investigation in various clinical disease processes. Understanding the mechanisms of indocyanine green accumulation and retention is essential to correctly interpreting and analyzing imaging data. The purpose of this scoping review was to synthesize what is known about the mechanism of indocyanine green retention at the cellular level to better understand the clinical nuances of delayed indocyanine green imaging and identify critical gaps in our knowledge to guide future studies.

METHODS

We performed a scoping review of 7,087 citations after performing database searches of PubMed, Scopus, the Cochrane Library, and the Web of Science Core Collection electronic databases. Studies were eligible for inclusion if they were peer-reviewed original research discussing the mechanism of indocyanine green retention in the results section in disease processes involving inflammation and/or necrosis, including cancer, and were available in English. Data were extracted using Covidence software.

RESULTS

Eighty-nine studies were included in the final analysis. Several features of indocyanine green retention were identified.

CONCLUSION

We identified several mechanistic features involved in indocyanine green accumulation in diseased tissue that overall had distinct mechanisms of indocyanine green retention in tumors, nontumor inflammation, and necrosis. Our study also reveals new insights on how inflammatory infiltrate influences indocyanine green fluorescence imaging. These findings are noteworthy because they add to our understanding of how fluorescence-guided surgery may be optimized based on the pathology of interest via specific indocyanine green dosing and timing of image acquisition.

What is the diagnostic accuracy of fluorescence-guided surgery for margin assessment in appendicular bone and soft tissue tumors? - A systematic review of clinical studies

BACKGROUND

Fluorescence-guided surgery (FGS) is a novel technique to successfully assess surgical margins intraoperatively. Investigation and adoption of this technique in orthopaedic oncology remains limited.

METHODS

The PRISMA guidelines were followed for this manuscript. Our study was registered on PROSPERO (380520). Studies describing the use of FGS for resection of bone and soft tissue sarcomas (STS) on humans were included. Diagnostic performance metrics (sensitivity, specificity, positive predictive value [PPV], negative predictive value [NPV] and accuracy) and margin positivity rate were the outcomes assessed.

RESULTS

Critical appraisal using the Joanna Brigs Institute checklists showed significant concerns for study quality. Sensitivity of FGS ranged from 22.2 % to 100 % in three of the four studies assessing his metrics; one study in appendicular tumors in the pediatric population reported 0 % sensitivity in the three cases included. Specificity ranged from 9.38 % to 100 %. PPV ranged from 14.6 % to 70 % while NPV was between 53.3 % and 100 %. The diagnostic accuracy ranged from 21.62 % to 92.31 %. Margin positivity rate ranged from 2 % to 50 %, with six of the seven studies reporting values between 20 % and 50 %.

CONCLUSIONS

FSG is a feasible technique to assess tumor margins in bone and STS. Reported performance metrics and margin positivity rates vary widely between studies due to low study quality and high heterogeneity in dying protocols.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Feasibility of indocyanine green-guided localization of pulmonary nodules in children with solid tumors

BACKGROUND

Clearing all pulmonary metastases is essential for curing pediatric solid tumors. However, intraoperative localization of such pulmonary nodules can be challenging. Therefore, an intraoperative tool that localizes pulmonary metastases is needed to improve diagnostic and therapeutic resections. Indocyanine green (ICG) real-time fluorescence imaging is used for this purpose in adult solid tumors, but its utility in pediatric solid tumors has not been determined.

METHODS

A single-center, open-label, nonrandomized, prospective clinical trial (NCT04084067) was conducted to assess the ability of ICG to localize pulmonary metastases of pediatric solid tumors. Patients with pulmonary lesions who required resection, either for therapeutic or diagnostic intent, were included. Patients received a 15-minute intravenous infusion of ICG (1.5 mg/kg), and pulmonary metastasectomy was performed the following day. A near-infrared spectroscopy iridium system was optimized to detect ICG, and all procedures were photo-documented and recorded.

RESULTS

ICG-guided pulmonary metastasectomies were performed in 12 patients (median age: 10.5 years). A total of 79 nodules were visualized, 13 of which were not detected by preoperative imaging. Histologic examination confirmed the following histologies: hepatoblastoma (n = 3), osteosarcoma (n = 2), and one each of rhabdomyosarcoma, Ewing sarcoma, inflammatory myofibroblastic tumor, atypical cartilaginous tumor, neuroblastoma, adrenocortical carcinoma, and papillary thyroid carcinoma. ICG guidance failed to localize pulmonary metastases in five (42%) patients who had inflammatory myofibroblastic tumor, atypical cartilaginous tumor, neuroblastoma, adrenocortical carcinoma, or papillary thyroid carcinoma.

CONCLUSIONS

ICG-guided identification of pulmonary nodules is not feasible for all pediatric solid tumors. However, it may localize most metastatic hepatic tumors and high-grade sarcomas in children.

Impact of Surgical Lights on the Performance of Fluorescence-Guided Surgery Systems: A Pilot Study

Fluorescence-guided surgery can aid in the intraoperative visualization of target tissues, with promising applications in human and veterinary surgical oncology. The aim of this study was to evaluate the performances of two fluoresce camera systems, IC-Flow^TM and Visionsense^TM VS3 Iridum, for the detection of two non-targeted (ICG and IRDye-800) and two targeted fluorophores (Angiostamp^TM and FAP-Cyan) under different room light conditions, including ambient light, new generation LED, and halogen artificial light sources, which are commonly used in operating theaters. Six dilutions of the fluorophores were imaged in phantom kits using the two camera systems. The limit of detection (LOD) and mean signal-to-background ratio (mSBR) were determined. The highest values of mSBR and a lower LOD were obtained in dark conditions for both systems. Under room lights, the capabilities decreased, but the mSBR remained greater than 3 (=clearly detectable signal). LOD and mSBR worsened under surgical lights for both camera systems, with a greater impact from halogen bulbs on Visionsense^TM VS3 Iridium and of the LED lights on IC-Flow due to a contribution of these lights in the near-infrared spectrum. When considering implementing FGS into the clinical routine, surgeons should cautiously evaluate the spectral contribution of the lights in the operating theater.

Defining the relevance of surgical margins. Part two: Strategies to improve prediction of recurrence risk

Due to the complex nature of tumour biology and the integration between host tissues and molecular processes of the tumour cells, a continued reliance on the status of the microscopic cellular margin should not remain our only determinant of the success of a curative-intent surgery for patients with cancer. Based on current evidence, relying on a purely cellular focus to provide a binary indication of treatment success can provide an incomplete interpretation of potential outcome. A more holistic analysis of the cancer margin may be required. If we are to move ahead from our current situation - and allow treatment plans to be more intelligently tailored to meet the requirements of each individual tumour - we need to improve our utilisation of techniques that either improve recognition of residual tumour cells within the surgical field or enable a more comprehensive interrogation of tumour biology that identifies a risk of recurrence. In the second article in this series on defining the relevance of surgical margins, the authors discuss possible alternative strategies for margin assessment and evaluation in the canine and feline cancer patient. These strategies include considering adoption of the residual tumour classification scheme; intra-operative imaging systems including fluorescence-guided surgery, optical coherence tomography and Raman spectroscopy; molecular analysis and whole transcriptome analysis of tissues; and the development of a biologic index (nomogram). These techniques may allow evaluation of individual tumour biology and the status of the resection margin in ways that are different to our current techniques. Ultimately, these techniques seek to better define the risk of tumour recurrence following surgery and provide the surgeon and patient with more confidence in margin assessment.

Intraoperative Evaluation of Soft Tissue Sarcoma Surgical Margins with Indocyanine Green Fluorescence Imaging

Soft tissue sarcomas (STS) are rare malignant tumors often associated with poor outcomes and high local recurrence rates. Current tools for intraoperative and definitive margin assessment include intraoperative frozen section and permanent pathology, respectively. Indocyanine green dye (ICG) is a historically safe fluorophore dye that has demonstrated efficacy for intraoperative margin assessment in the surgical management of both breast and gastrointestinal cancers. The utility of ICG in the surgical management of sarcoma surgery has primarily been studied in pre-clinical mouse models and warrants further investigation as a potential adjunct to achieving negative margins. This study is a prospective, non-randomized clinical study conducted on patients with confirmed or suspected STS. Patients younger than 18 years, with a prior adverse reaction to iodine or fluorescein, or with renal disease were excluded from the study. Intravenous ICG was infused approximately three hours prior to surgery at a dosage of 2.0-2.5 mg/kg, and following tumor resection, the excised tumor and tumor bed were imaged for fluorescence intensity. When scanning the tumor bed, a threshold of 77% calibrated to the region of maximum intensity in the resected tumor was defined as a positive ICG margin, according to published protocols from the breast cancer literature. ICG results were then compared with the surgeon's clinical impression of margin status and permanent pathology results. Out of 26 subjects recruited for the original study, 18 soft tissue sarcomas (STS) were included for analysis. Three subjects were excluded for having bone sarcomas, and five subjects were excluded due to final pathology, which was ultimately inconsistent with sarcoma. The average age of patients was 64.1 years old (range: 28-83), with an average ICG dose of 201.8 mg. In 56% (10/18) of patients, ICG margins were consistent with the permanent pathology margins, with 89% specificity. The use of ICG as an intraoperative adjunct to obtaining negative margins in soft tissue sarcoma surgery is promising. However, studies with larger sample sizes are warranted to further delineate the accuracy, optimal dosage, timing, and types of sarcoma in which this diagnostic tool may be most useful.

Algorithms and instrumentation for rapid spatial frequency domain fluorescence diffuse optical imaging

SIGNIFICANCE

Rapid estimation of the depth and margins of fluorescence targets buried below the tissue surface could improve upon current image-guided surgery techniques for tumor resection.

AIM

We describe algorithms and instrumentation that permit rapid estimation of the depth and transverse margins of fluorescence target(s) in turbid media; the work aims to introduce, experimentally demonstrate, and characterize the methodology.

APPROACH

Spatial frequency domain fluorescence diffuse optical tomography (SFD-FDOT) technique is adapted for rapid and computationally inexpensive estimation of fluorophore target depth and lateral margins. The algorithm utilizes the variation of diffuse fluorescence intensity with respect to spatial-modulation-frequency to compute target depth. The lateral margins are determined via analytical inversion of the data using depth information obtained from the first step. We characterize method performance using fluorescent contrast targets embedded in tissue-simulating phantoms.

RESULTS

Single and multiple targets with significant lateral size were imaged at varying depths as deep as 1 cm. Phantom data analysis showed good depth-sensitivity, and the reconstructed transverse margins were mostly within ∼30 % error from true margins.

CONCLUSIONS

The study suggests that the rapid SFD-FDOT approach could be useful in resection surgery and, more broadly, as a first step in more rigorous SFD-FDOT reconstructions. The experiments permit evaluation of current limitations.

Second window ICG predicts gross-total resection and progression-free survival during brain metastasis surgery

OBJECTIVE

Metastases are the most common intracranial malignancies and complete resection can provide relief of neurological symptoms and reduce recurrence. The authors' prospective pilot study in 2017 demonstrated promising results for the application of high-dose, delayed imaging of indocyanine green (ICG), known as second window ICG (SWIG), in patients undergoing surgery for brain metastases. In this prospective cohort study, the authors evaluated intraoperative imaging and clinical outcomes of treatment using SWIG.

METHODS

Patients were prospectively enrolled in an approved study of high-dose, delayed ICG (SWIG) and received 5 mg/kg (2014-2018) or 2.5 mg/kg (2018-2019) ICG 24 hours preoperatively. Intraoperatively, near-infrared (NIR) imaging was performed using a dedicated NIR exoscope. NIR images were analyzed and the signal-to-background ratio (SBR) was calculated to quantify fluorescence. Residual fluorescence on the postresection NIR view was compared and correlated to the residual gadolinium enhancement on postoperative MRI. Patient survival and predictive factors were analyzed.

RESULTS

In total, 51 intracranial metastases were surgically treated in 47 patients in this cohort. All 51 metastatic tumors demonstrated strong NIR fluorescence (mean SBR 4.9). In tumors ≤ 10 mm from the cortical surface, SWIG with 5 mg/kg ICG produced enhanced transdural tumor visibility (91.3%) compared to 2.5 mg/kg (52.9%; p = 0.0047). Neoplastic margin detection using NIR fluorescence compared to white light improved sensitivity, albeit lowered specificity; however, increasing the SBR cutoff for positive fluorescence significantly improved specificity without sacrificing sensitivity, increasing the overall accuracy from 57.5% to 72.5%. A lack of residual NIR fluorescence after resection was closely correlated with a lack of residual enhancement on postoperative MRI (p = 0.007). Among the 16 patients in whom tumor recurred at the site of surgery, postoperative MRI successfully predicted 8 cases, whereas the postresection NIR view predicted 12 cases. Progression-free survival rate at 12 months was greater for patients without residual NIR fluorescence (38%) than for those without residual enhancement on postoperative MRI (29%).

CONCLUSIONS

The current study demonstrates the clinical benefits of the SWIG technique in surgery for patients with brain metastases. Specifically, this technique allows for dose-dependent, transdural localization of neoplasms and improved sensitivity in neoplastic margin detection. Postresection residual fluorescence can be a powerful tool to evaluate extent of resection in conjunction with MRI, and it may guide decisions on brain metastasis management.

Intraoperative assessment of canine soft tissue sarcoma by deep learning enhanced optical coherence tomography

Soft tissue sarcoma (STS) is a locally aggressive and infiltrative tumour in dogs. Surgical resection is the treatment of choice for local tumour control. Currently, post-operative pathology is performed for surgical margin assessment. Spectral-domain optical coherence tomography (OCT) has recently been evaluated for its value for surgical margin assessment in some tumour types in dogs. The purpose of this study was to develop an automatic diagnosis system that can assist clinicians in real-time for OCT image interpretation of tissues at surgical margins. We utilized a ResNet-50 network to classify healthy and cancerous tissues. A patch-based approach was adopted to achieve accurate classification with limited training data (80 cancer images, 80 normal images) and the validation set (20 cancer images, 20 normal images). The proposed method achieved an average accuracy of 97.1% with an excellent sensitivity of 94.3% on the validation set; the quadratic weighted κ was 0.94 for the STS diagnosis. In an independent test data set of 20 OCT images (10 cancer images, 10 normal images), the proposed method correctly differentiated all the STS images. Furthermore, we proposed a diagnostic curve, which could be evaluated in real-time to assist clinicians in detecting the specific location of a lesion. In short, the proposed method is accurate, operates in real-time and is non-invasive, which could be helpful for future surgical guidance.

Diagnostic accuracy of optical coherence tomography for assessing surgical margins of canine soft tissue sarcomas in observers of different specialties

OBJECTIVE

To determine the diagnostic accuracy of optical coherence tomography (OCT) to assess surgical margins of canine soft tissue sarcoma (STS) and determine the influence of observer specialty and training.

STUDY DESIGN

Blinded clinical prospective study.

ANIMALS

Twenty-five dogs undergoing surgical excision of STS.

METHODS

In vivo and ex vivo surgical margins were imaged with OCT after tumor resection. Representative images and videos were used to generate a training presentation and data sets. These were completed by 16 observers of four specialties (surgery, radiology, pathology, and OCT researchers). Images and videos from data sets were classified as cancerous or noncancerous.

RESULTS

The overall sensitivity and specificity were 88.2% and 92.8%, respectively, for in vivo tissues and 82.5% and 93.3%, respectively, for ex vivo specimens. The overall accurate classification for all specimens was 91.4% in vivo and 89.5% ex vivo. There was no difference in accuracy of interpretation of OCT imaging by observers of different specialties or experience levels.

CONCLUSION

Use of OCT to accurately assess surgical margins after STS excision was associated with a high sensitivity and specificity among various specialties. Personnel of all specialties and experience levels could effectively be trained to interpret OCT imaging.

CLINICAL SIGNIFICANCE

Optical coherence tomography can be used by personnel of different specialty experience levels and from various specialties to accurately identify canine STS in vivo and ex vivo after a short training session. These encouraging results provide evidence to justify further research to assess the ability of OCT to provide real-time assessments of surgical margins and its applicability to other neoplasms.

Sources of widefield fluorescence from the brain

Widefield fluorescence microscopy is used to monitor the spiking of populations of neurons in the brain. Widefield fluorescence can originate from indicator molecules at all depths in cortex and the relative contributions from somata, dendrites, and axons are often unknown. Here, I simulate widefield illumination and fluorescence collection and determine the main sources of fluorescence for several GCaMP mouse lines. Scattering strongly affects illumination and collection. One consequence is that illumination intensity is greatest ~300-400 µm below the pia, not at the brain surface. Another is that fluorescence from a source deep in cortex may extend across a diameter of 3-4 mm at the brain surface, severely limiting lateral resolution. In many mouse lines, the volume of tissue contributing to fluorescence extends through the full depth of cortex and fluorescence at most surface locations is a weighted average across multiple cortical columns and often more than one cortical area.

The feasibility and utility of optical coherence tomography directed histopathology for surgical margin assessment of canine mast cell tumours

Histopathologic surgical margin assessment in veterinary patients is an imprecise science with assessment limited to a small proportion of the surgical margin due to time and finances. Incomplete excision of canine mast cell tumours (MCTs) alters treatment recommendations and prognosis. Optical coherence tomography (OCT) is a novel imaging modality that has been reported in a single veterinary study for surgical margin assessment. Twenty-five dogs with 34 MCTs were enrolled in a prospective pilot-study to assess the imaging characteristics of canine MCTs with OCT and to evaluate the feasibility and utility of OCT-guided histopathology. All dogs underwent routine surgical excision of MCTs. OCT imaging was used to assess the entire surgical margin prior to placement in formalin. Either normal areas or areas suspected of incomplete MCT excision were inked. Standard histopathologic sectioning and tangential sectioning of inked areas were performed and compared to OCT results. OCT identified MCT near the surgical margin in 10 of 26 specimens (38.4%). Four specimens suspicious for incomplete margins on OCT had incomplete MCT excision that was missed on standard histopathologic sectioning. Six specimens had OCT-guided sections taken as suspicious, which did not show MCT on histopathology. OCT-guided pathology sections were able to detect incompletely excised MCT near the surgical margin with a sensitivity of 90% and specificity of 56.2% in this preliminary study. OCT imaging shows promise for guiding pathologists to areas of interest to improve the diagnostic accuracy of surgical margin assessment in excised canine MCTs.

Dual-agent fluorescent labeling of soft-tissue sarcomas improves the contrast based upon targeting both interstitial and cellular components of the tumor milieu

BACKGROUND

Current practices for fluorescence-guided cancer surgery utilize a single fluorescent agent, but homogeneous distribution throughout the tumor is difficult to achieve. We hypothesize that administering a perfusion and a molecular-targeted agent at their optimal administration-to-imaging time will improve whole-tumor contrast.

EXPERIMENTAL DESIGN

Mice bearing subcutaneous xenograft human synovial sarcomas were administered indocyanine green (ICG) (3 mg/kg) or ABY-029 (48.7 μg/kg)-an epidermal growth factor receptor-targeted Affibody molecule-alone or in combination. Fluorescence contrast and signal distribution were compared between treatment groups. Two commercial fluorescence imaging systems were tested for simultaneous imaging of ICG and ABY-029.

RESULTS

ABY-029 has a moderate positive correlation with viable tumor (ρ = 0.2 ± 0.4), while ICG demonstrated a strong negative correlation (ρ = -0.6 ± 0.1). The contrast-to-variance ratio was highest in the ABY-029 +ICG (2.5 ± 0.8), compared to animals that received ABY-029 (2.3 ± 0.8) or ICG (2.0 ± 0.5) alone. Moreover, the combination of ABY-029 + ICG minimizes the correlation between viable tumor and fluorescence intensity (ρ = -0.1 ± 0.2) indicating the fluorescence signal distribution is more homogeneous throughout the tumor milieu.

CONCLUSION

Dual-agent imaging utilizing a single channel in a commercial fluorescence-guided imaging system tailored for IRDye 800CW is a promising method to increase tumor contrast in a clinical setting.

Intraoperative near-infrared imaging can identify canine mammary tumors, a spontaneously occurring, large animal model of human breast cancer

Introduction

Current methods of intraoperative margin assessment in breast conserving surgery are impractical, unreliable, or time consuming. We hypothesized that intraoperative near-infrared (NIR) imaging with an FDA-approved NIR optical contrast agent could identify canine mammary tumors, a spontaneous large animal model of human breast cancer, during surgery.

Methods

Dogs with mammary tumors underwent a standard of care lumpectomy or mastectomy with wide surgical margins 20 hours after indocyanine green administration (3 mg/kg IV). During surgery, NIR imaging was performed on tumors and wound margins in situ and tumors and lymph nodes ex vivo. Following resection, the wound bed was examined for residual fluorescence. Fluorescence intensity was determined by signal-to-background ratio (SBR). All tumors, areas of residual fluorescence, and lymph nodes underwent histopathologic analysis.

Results

There were 41 mammary tumors in 16 female dogs. Twenty tumors were malignant and 21 were benign. Twenty-eight tumors were fluorescent (mean SBR 1.5±0.2). Sensitivity of fluorescence for all malignant tumors was 80% (16/20) and 93.3% (14/15) for malignant tumors > 2 cm. Specificity for malignancy was low (< 2cm = 55%; > 2cm = 30%). Tumors > 2 cm were more likely to be fluorescent (OR 6.05, 95% CI 1.50–24.44, P = 0.011) but not more likely to be malignant (OR 3.09, 95% CI 0.86–11.14, P = 0.085) than tumors ≤ 2 cm. Four out of seven inguinal lymph nodes excised in the mastectomy specimen fluoresced. All four drained malignant tumors; however only 2/4 contained metastatic disease.

Conclusion

Systemic ICG accumulates reliably in malignant canine mammary tumors > 2 cm. Although no tumor margins fluoresced, a wider margin of normal tissue is removed in canine mastectomy, making direct comparisons with breast conserving surgery difficult. Targeted NIR imaging agents are likely required to improve detection of smaller tumors and improve the specificity of NIR imaging for residual disease and metastatic lymph node detection.

Technology for Intraoperative Margin Assessment in Breast Cancer

BACKGROUND

As breast-conserving surgery (BCS) has become standard for treatment of breast cancer, the need for new technology to improve intraoperative margin assessment (IMA) has become clear. Close or positive margins during BCS lead to additional surgeries, treatment delay, additional stress for patients, and healthcare cost. Academia and industry have developed a diverse field of new technologies to allow surgeons to assess margins in the operating room. These technologies aim to reduce current rates of positive margins on final pathology.

METHODS

We selected recently developed IMA technologies, some of which have undergone large clinical trials and others that are still in early stage development. Technologies were categorized based on underlying methodology to differentiate malignant and normal tissue: spectroscopy, electrical properties, optical imaging and molecular imaging. Additionally, this review details clinical investigations, relevant statistical analysis as well as strengths and weaknesses of the various technologies.

CONCLUSION

Numerous technical innovations are being implemented to diminish rates of positive margins at breast tumor resection. Close collaboration among cross-disciplinary teams to further develop many of these technologies as well as completion of larger scale clinical studies are required to define an optimal approach. Development with an eye toward prioritizing sensitivity/specificity as well as healthcare cost containment has the potential to make a significant impact on this ongoing clinical need in breast cancer surgery.

Fluorescence-guided surgery using indocyanine green in dogs with superficial solid tumours

BACKGROUND

Near-infrared fluorescence (NIRF) imaging is a relatively novel technique that can aid surgeons during intraoperative tumour identification.

METHODS

Nine canine oncology patients (five mammary gland tumours, three mast cell tumours and one melanoma) received intravenous indocyanine green (ICG). After 24 hours, tumours were resected and fluorescence intensities of tumours and surroundings were evaluated. Additional wound bed tissue was resected if residual fluorescence was present after tumour resection. Ex vivo, fluorescence-guided dissection was performed to separate tumour from surrounding tissue.

RESULTS

Intraoperative NIRF-guided tumour delineation was feasible in four out of nine dogs. Wound bed imaging after tumour removal identified nine additional fluorescent lesions, of which four contained tumour tissue. One of these four true positive in vivo lesions was missed by standard-of-care inspection. Ex vivo fluorescence-guided tumour dissection showed a sensitivity of 72 per cent and a specificity of 80 per cent in discriminating between tumour and surrounding tissue.

CONCLUSION

The value of ICG for intraoperative tumour delineation seems more limited than originally thought. Although NIRF imaging using ICG did identify remaining tumour tissue in the wound bed, a high false positive rate was also observed.

Effect of preoperative cancer treatment on epidermal growth factor receptor (EGFR) receptor expression level in ABY-029 guided sarcoma surgery

Surgical excision via wide local excision (WLE) of the primary sarcoma tumor is a mainstay of treatment due to the limited effectiveness of chemotherapy and radiation. Even with attempts at WLE, 22-34% of the patient will be diagnosed with a positive margin by the pathologist, necessitating additional radiation or surgery. Recent studies have demonstrated reduced local recurrence when using fluorescence-guided surgery (FGS) to detect residual sarcoma following attempted WLE. ABY-029 is an anti-EGFR Affibody® molecule labeled with IRDye800CW that is currently under Phase 0 human trial for FGS. To date, several studies have been performed to evaluate ABY-029 signal intensity in untreated human sarcoma xenografts; however, many patients undergoing cancer surgery have received pre-operative radiation and/or chemotherapy, which can affect tissue properties and tumor molecule expression level. Determining the effects of radiation and chemotherapy exposure on fluorophore binding in sarcomas may influence best practices in implementing FGS for sarcoma. In this project, fluorophore signal intensities in tumor and surrounding tissue were measured and compared to the receptor concentration determined by immunohistochemistry. Here, we report the result for one EGFR positive synovial sarcoma cell lines, SW982. Four groups of human dose equivalent therapies - control, radiation, chemotherapy (Doxorubicin) and radiation followed by chemotherapy - were given to the tumor-bearing mice. The difference between groups can be used to determine the effects of preoperative sarcoma therapies on EGFR expression, ABY-029 uptake, and optical properties of tissues.

Advanced Cancer Imaging Applied in the Comparative Setting

The potential for companion (pet) species with spontaneously arising tumors to act as surrogates for preclinical development of advanced cancer imaging technologies has become more apparent in the last decade. The utility of the companion model specifically centers around issues related to body size (including spatial target/normal anatomic characteristics), physical size and spatial distribution of metastasis, tumor heterogeneity, the presence of an intact syngeneic immune system and a syngeneic tumor microenvironment shaped by the natural evolution of the cancer. Companion species size allows the use of similar equipment, hardware setup, software, and scan protocols which provide the opportunity for standardization and harmonization of imaging operating procedures and quality assurance across imaging protocols, imaging hardware, and the imaged species. Murine models generally do not replicate the size and spatial distribution of human metastatic cancer and these factors strongly influence image resolution and dosimetry. The following review will discuss several aspects of comparative cancer imaging in more detail while providing several illustrative examples of investigational approaches performed or currently under exploration at our institutions. Topics addressed include a discussion on interested consortia; image quality assurance and harmonization; image-based biomarker development and validation; contrast agent and radionuclide tracer development; advanced imaging to assess and predict response to cytotoxic and immunomodulatory anticancer agents; imaging of the tumor microenvironment; development of novel theranostic approaches; cell trafficking assessment via non-invasive imaging; and intraoperative imaging to inform surgical oncology decision making. Taken in totality, these comparative opportunities predict that safety, diagnostic and efficacy data generated in companion species with naturally developing and progressing cancers would better recapitulate the human cancer condition than that of artificial models in small rodent systems and ultimately accelerate the integration of novel imaging technologies into clinical practice. It is our hope that the examples presented should serve to provide those involved in cancer investigations who are unfamiliar with available comparative methodologies an understanding of the potential utility of this approach.

Near-infrared imaging and optical coherence tomography for intraoperative visualization of tumors

Surgical excision is the foundation of treatment for early-stage solid tumors in man and companion animals. Complete excision with appropriate margins of surrounding tumor-free tissue is crucial to survival. Intraoperative imaging allows real-time visualization of tumors, assessment of surgical margins, and, potentially, lymph nodes and satellite metastatic lesions, allowing surgeons to perform complete tumor resections while sparing surrounding vital anatomic structures. This Review will focus on the use of near-infrared imaging and optical coherence tomography for intraoperative tumor visualization.

Review of clinical trials in intraoperative molecular imaging during cancer surgery

Most solid cancers are treated by surgical resections to reduce the burden of disease. Surgeons often face the challenge of detecting small areas of residual neoplasm after resection or finding small primary tumors for the initial resection. Intraoperative molecular imaging (IMI) is an emerging technology with the potential to dramatically improve cancer surgery operations by allowing surgeons to better visualize areas of neoplasm using fluorescence imaging. Over the last two years, two molecular optical contrast agents received U.S. Food and Drug Administration approval, and several more drugs are now on the horizon. Thus a conference was organized at the University of Pennsylvania to bring together oncologic surgeons from different specialties to discuss the current clinical status of IMI trials with a specific focus on phase 2 and phase 3 studies. In addition, phase 1 and experimental trials were also discussed briefly, to highlight other novel techniques. Our review summarizes the discussions from the conference and delves into the types of cancers discussed, different contrast agents in human trials, and the clinical value being studied.

Measuring microdose ABY-029 fluorescence signal in a primary human soft-tissue sarcoma resection

Microdose administration of ABY-029, an anti-epidermal growth factor receptor Affibody molecule conjugated to IRDye 800CW, is being studied in a Phase 0 trial for resection of soft-tissue sarcomas. The excised tissue of a single patient in the microdose administration group was imaged with both a wide-field fluorescence surgical system and a flat-bed scanning fluorescence imaging system. Here the resultant fluorescence from a breadloaf section of the primary tumor specimen and six region-specific tissue samples collected from that breadloaf are compared using these two imaging systems - a flatbed, black-box, fluorescence scanning system, the Odyssey CLx, and a open-air, wide-field, pre-clinical surgical imaging system, the Solaris. Florescence signal is compared using a variety of methods including: mean, standard deviation, variance, tumor-to-background ratio, biological-variance ratio, and contrast-to-noise ratio. The images produced from the Odyssey scanner have higher signal variance but more accurately represent the EGFR expression in small tissue sections. The Solaris system has higher depth sensitivity and volume averaging, and as such has lower signal variation and higher contrast-to-noise ratio.

Evaluation of Aminolevulinic Acid-Derived Tumor Fluorescence Yields Disparate Results in Murine and Spontaneous Large Animal Models of Lung Cancer

Fluorescence guided surgery is an emerging technology that may improve accuracy of pulmonary resection for non-small cell lung cancer (NSCLC). Herein we explore optical imaging for NSCLC surgery using the well-studied protoporphyrin IX (PPIX)/5-aminiolevulinic acid (5-ALA) system. More specifically, we evaluate fluorescent patterns observed when using (1) commonly utilized in vitro and murine NSCLC models and with (2) spontaneous canine NSCLCs, which closely mimic human disease. Using flow cytometry and fluorescent microscopy, we confirmed that NSCLC models fluoresce after exposure to 5-ALA in vitro. High levels of fluorescence were similarly observed in murine tumors within 2 hours of systemic 5-ALA delivery. When evaluating this approach in spontaneous canine NSCLC, tumor fluorescence was observed in 6 of 7 canines. Tumor fluorescence, however, was heterogenous owing to intratumoral variations in cellularity and necrosis. Margin and lymph node detection was inaccurate. These data demonstrate the importance of incorporating reliable cancer models into preclinical evaluations of optical agents. Utilization of spontaneous large animal models of cancer may further provide an important intermediate in the path to human translation of optical contrast agents.

Preclinical imaging of epidermal growth factor receptor with ABY-029 in soft-tissue sarcoma for fluorescence-guided surgery and tumor detection

BACKGROUND AND OBJECTIVES

Fluorescence-guided surgery using epidermal growth factor receptor (EGFR) targeting has been performed successfully in clinical trials using a variety of fluorescent agents. We investigate ABY-029 (anti-EGFR Affibody^® molecule labeled with IRDye 800CW) compared with a small-molecule perfusion agent, IRDye 700DX carboxylate, in a panel of soft-tissue sarcomas with varying levels of EGFR expression and vascularization.

METHODS

Five xenograft soft-tissue sarcoma cell lines were implanted into immunosuppressed mice. ABY-029 and IRDye 700DX were each administered at 4.98 μM. Fluorescence from in vivo and ex vivo (fresh and formalin-fixed) fixed tissues were compared. The performance of three fluorescence imaging systems was assessed for ex vivo tissues.

RESULTS

ABY-029 is retained longer within tumor tissue and achieves higher tumor-to-background ratios both in vivo and ex vivo than IRDye 700DX. ABY-029 fluorescence is less susceptible to formalin fixation than IRDye 700DX, but both agents have disproportional signal loss in a variety of tissues. The Pearl Impulse provides the highest contrast-to-noise ratio, but all systems have individual advantages.

CONCLUSIONS

ABY-029 demonstrates promise to assist in wide local excision of soft-tissue sarcomas. Further clinical evaluation of in situ or freshly excised ex vivo tissues using fluorescence imaging systems is warranted.

Optimization of Second Window Indocyanine Green for Intraoperative Near-Infrared Imaging of Thoracic Malignancy

BACKGROUND

Near-infrared (NIR) imaging using the second time window of indocyanine green (ICG) allows localization of pulmonary, pleural, and mediastinal malignancies during surgery. Based on empirical evidence, we hypothesized that different histologic tumor types fluoresce optimally at different ICG doses.

STUDY DESIGN

Patients with thoracic tumors biopsy-proven or suspicious for malignancy were enrolled in an NIR imaging clinical trial. Patients received a range of ICG doses 1 day before surgery: 1 mg/kg (n = 8), 2 mg/kg (n = 8), 3 mg/kg (n = 13), 4 mg/kg (n = 8), and 5 mg/kg (n = 8). Intraoperatively, NIR imaging was performed. The endpoint was to identify the highest tumor-to-background fluorescence ratio (TBR) for each tumor type at each dose. Final pathology confirmed tumor histology.

RESULTS

Of 45 patients, 41 had malignancies (18 non-small cell lung cancers [NSCLC], 3 pulmonary neuroendocrine tumors, 13 thoracic metastases, 4 thymomas, 3 mesotheliomas). At doses of 4 to 5 mg/kg, the TBR from primary NSCLC vs other malignancies was no different (2.70 vs 3.21, p = 1.00). At doses of 1 to 3 mg/kg, the TBR was greater for the NSCLCs (3.19 vs 1.49, p = 0.0006). Background fluorescence from the heart or ribs was observed in 1 of 16 cases at 1 to 2 mg/kg, 5 of 13 cases at 3 mg/kg, and 14 of 16 cases at 4 to 5 mg/kg; this was a major determinant of dose optimization.

CONCLUSIONS

This is the first study to demonstrate that the optimal NIR contrast agent dose varies by tumor histology. Lower dose ICG (2 to 3 mg/kg) is superior for nonprimary lung cancers, and high dose ICG (4 to 5 mg/kg) is superior for lung cancers. This will have major implications as more intraoperative imaging trials surface in other specialties, will significantly reduce costs and may facilitate wider application.

Intraoperative fluorescence imaging in thoracic surgery

Intraoperative fluorescence imaging (IFI) can improve real-time identification of cancer cells during an operation. Phase I clinical trials in thoracic surgery have demonstrated that IFI with second window indocyanine green (TumorGlow^® ) can identify subcentimeter pulmonary nodules, anterior mediastinal masses, and mesothelioma, while the use of a folate receptor-targeted near-infrared agent, OTL38, can improve the specificity for diagnosing tumors with folate receptor expression. Here, we review the existing preclinical and clinical data on IFI in thoracic surgery.

Advances in Monte Carlo Simulation for Light Propagation in Tissue

Monte Carlo (MC) simulation for light propagation in tissue is the gold standard for studying the light propagation in biological tissue and has been used for years. Interaction of photons with a medium is simulated based on its optical properties. New simulation geometries, tissue-light interaction methods, and recording techniques recently have been designed. Applications, such as whole mouse body simulations for fluorescence imaging, eye modeling for blood vessel imaging, skin modeling for terahertz imaging, and human head modeling for sinus imaging, have emerged. Here, we review the technical advances and recent applications of MC simulation.

Intraoperative near-infrared imaging of mesothelioma

Though difficult to achieve, complete resection of malignant pleural mesothelioma is paramount to improving patient survival. Surgeons have traditionally been limited to using visual inspection and manual palpation to locate and remove cancerous tissue. However, intraoperative molecular imaging (IMI) is a promising new technology in surgery. Molecular imaging utilizes a fluorescent tracer that selectively accumulates in cancer cells. An imaging device is then used to detect and augment the fluorescent signal emitted from the fluorescent cancer cells. Our group and others have demonstrated that molecular imaging with either indocyanine green (ICG) or a folate receptor alpha (FRα) targeted fluorophore can accurately identify a number of intrathoracic malignancies. Early studies of intraoperative imaging have suggested its efficacy for malignant pleural mesothelioma. In a murine model of mesothelioma, intraoperative imaging was found to have sensitivity of 87% and specificity of 83%. In a pilot human study, eight patients with biopsy-proven epithelial malignant pleural mesothelioma were administered 5 mg/kg of intravenous ICG injection 24 h prior to resection. The following day, a near-infrared (NIR) imaging device was used to detect tumor fluorescence intraoperatively. After what was believed to be complete tumor excision, the wound bed was re-imaged for residual fluorescence indicative of retained tumor. When residual fluorescence was detected, additional tissue was resected, if feasible, and specimens were sent for pathologic correlation. In all cases, intraoperative fluorescence localized to mesothelioma deposits which were confirmed on final pathology. Following resection, fluorescence was confirmed ex vivo with a mean tumor-to-background ratio (TBR) of 3.2 (IQR: 2.9-3.4). It is hoped that this technology will improve outcomes for mesothelioma patients by allowing for a more complete oncologic resection.

Intraoperative molecular imaging to identify lung adenocarcinomas

Intraoperative molecular imaging is a promising new technology with numerous applications in lung cancer surgery. Accurate identification of small nodules and assessment of tumor margins are two challenges in pulmonary resections for cancer, particularly with increasing use of video-assisted thoracoscopic surgery (VATS). One potential solution to these problems is intraoperative use of a fluorescent contrast agent to improve detection of cancer cells. This technology requires both a targeted fluorescent dye that will selectively accumulate in cancer cells and a specialized imaging system to detect the cells. In several studies, we have shown that intraoperative imaging with indocyanine green (ICG) can be used to accurately identify indeterminate pulmonary nodules. The use of a folate-tagged fluorescent molecule targeted to the folate receptor-α (FRα) further improves the sensitivity and specificity of detecting lung adenocarcinomas. We have demonstrated this technology can be used as an "optical biopsy" to differentiate adenocarcinoma versus other histological subtypes of pulmonary nodules. This strategy has potential applications in assessing bronchial stump margins, identifying synchronous or metachronous lesions, and rapidly assessing lymph nodes for lung adenocarcinoma.

Lasing in blood

Indocyanine green (ICG) is the only near-infrared dye approved by the U.S. Food and Drug Administration for clinical use. When injected in blood, ICG binds primarily to plasma proteins and lipoproteins, resulting in enhanced fluorescence. Recently, the optofluidic laser has emerged as a novel tool in bio-analysis. Laser emission has advantages over fluorescence in signal amplification, narrow linewidth, and strong intensity, leading to orders of magnitude increase in detection sensitivity and imaging contrast. Here we successfully demonstrate, to the best of our knowledge, the first ICG lasing in human serum and whole blood with the clinical ICG concentrations and the pump intensity far below the clinically permissible level. Furthermore, we systematically study ICG laser emission within each major serological component (albumins, globulins, and lipoproteins) and reveal the critical elements and conditions responsible for lasing. Our work marks a critical step toward eventual clinical and biomedical applications of optofluidic lasers using FDA approved fluorophores, which may complement or even supersede conventional fluorescence-based sensing and imaging.

Identification of breast cancer margins using intraoperative near-infrared imaging

BACKGROUND AND OBJECTIVES

Current methods of intraoperative breast cancer margin assessment are labor intensive, not fully reliable, and time consuming; therefore novel strategies are necessary. We hypothesized that near infrared (NIR) intraoperative molecular imaging using systemic indocyanine green (ICG) would be helpful in discerning tumor margins.

METHODS

A mammary cancer cell line, 4T1, was used to establish tumors in mouse flanks (n = 60). Tumors were excised 24 hr after intravenous ICG. Assessment of residual tumor in the wound bed was performed using a combination of NIR imaging and traditional method (by visual inspection and palpation) versus traditional method alone. Next we performed a clinical trial to evaluate the role of NIR imaging after systemic ICG for the margin assessment of 12 patients undergoing breast-conserving surgery.

RESULTS

Traditional margin assessment identified 30% of positive margins while NIR imaging identified 90% of positive margins. In our clinical trial, all tumors were detected by NIR imaging and there was fluorescent evidence of residual tumor in the tumor bed in 6 of the 12 patients. None of these patients had positive margins on pathology.

CONCLUSIONS

Systemic ICG reliably accumulates in breast cancers in murine models as well as human breast cancer. While NIR imaging is helpful for detection of retained tumor margins in our animal model, intraoperative imaging for precise margin detection will need further refinement before clinical value can be obtained. J. Surg. Oncol. 2016;113:508-514. © 2016 Wiley Periodicals, Inc.

Hybrid polymeric nano-capsules loaded with gold nanoclusters and indocyanine green for dual-modal imaging and photothermal therapy

Currently there is a great need to design nano-carriers which enable multi-modal imaging of tumors and administration of therapeutics with high efficacy simultaneously. Herein we report a facile and robust approach to fabricate multifunctional nano-capsules based on double emulsions. The hybrid nano-capsules were loaded with BSA capped gold nanoclusters (AuNCs) and indocyanine green (ICG) for dual-modal imaging and effective photothermal therapy. RGD peptides were conjugated onto the surface of the hybrid nano-capsules to target cells overexpressing integrin α_νβ₃. We demonstrated that the as-prepared nano-capsules can be used for both one-photon and two-photon fluorescence imaging of tumor cells, and subsequent photothermal ablation with high effectiveness. The background noise of tissue autofluorescence was dramatically suppressed in the two-photon imaging mode. Therefore, it assisted a great deal to acquire images with a high signal-to-noise ratio using the hybrid nano-capsules. Due to a unique combination of the one-photon/two-photon fluorescence imaging and highly-effective photothermal properties, the hybrid nano-capsules may find broad biomedical applications as attractive theranostic nanomaterials.