Lymphoscintigraphy, the sentinel node concept, and the intraoperative gamma probe in melanoma, breast cancer, and other potential cancers

Innovations in dedicated PET instrumentation: from the operating room to specimen imaging

This review casts a spotlight on intraoperative positron emission tomography (PET) scanners and the distinctive challenges they confront. Specifically, these systems contend with the necessity of partial coverage geometry, essential for ensuring adequate access to the patient. This inherently leans them towards limited-angle PET imaging, bringing along its array of reconstruction and geometrical sensitivity challenges. Compounding this, the need for real-time imaging in navigation systems mandates rapid acquisition and reconstruction times. For these systems, the emphasis is on dependable PET image reconstruction (without significant artefacts) while rapid processing takes precedence over the spatial resolution of the system. In contrast, specimen PET imagers are unburdened by the geometrical sensitivity challenges, thanks to their ability to leverage full coverage PET imaging geometries. For these devices, the focus shifts: high spatial resolution imaging takes precedence over rapid image reconstruction. This review concurrently probes into the technical complexities of both intraoperative and specimen PET imaging, shedding light on their recent designs, inherent challenges, and technological advancements.

Revolutionizing lymph node metastasis imaging: the role of drug delivery systems and future perspectives

The deployment of imaging examinations has evolved into a robust approach for the diagnosis of lymph node metastasis (LNM). The advancement of technology, coupled with the introduction of innovative imaging drugs, has led to the incorporation of an increasingly diverse array of imaging techniques into clinical practice. Nonetheless, conventional methods of administering imaging agents persist in presenting certain drawbacks and side effects. The employment of controlled drug delivery systems (DDSs) as a conduit for transporting imaging agents offers a promising solution to ameliorate these limitations intrinsic to metastatic lymph node (LN) imaging, thereby augmenting diagnostic precision. Within the scope of this review, we elucidate the historical context of LN imaging and encapsulate the frequently employed DDSs in conjunction with a variety of imaging techniques, specifically for metastatic LN imaging. Moreover, we engage in a discourse on the conceptualization and practical application of fusing diagnosis and treatment by employing DDSs. Finally, we venture into prospective applications of DDSs in the realm of LNM imaging and share our perspective on the potential trajectory of DDS development.

Clinical relevance of sentinel lymph node biopsy in early ovarian cancer

The first-line treatment for early ovarian cancer typically involves primary debulking surgery aimed at maximal cytoreduction, alongside adjuvant chemotherapy if clinically indicated. Nodal assessment involving pelvic and para-aortic lymph node dissection is typically performed during the primary debulking surgery. However, the survival benefit of lymphadenectomy in patients with early ovarian cancer has not been well established, and the procedure is associated with longer operation time and higher perioperative complications. With the emergence of minimally invasive surgery as a potential alternative to laparotomy for early ovarian cancer, sentinel lymph node biopsy has been evaluated in this setting. In this review, we summarized the current literature regarding sentinel lymph node biopsy in patients with early ovarian cancer, focusing on the clinical relevance of this method, including its detection rate and diagnostic accuracy. Additionally, we discuss the current status of clinical trials investigating sentinel lymph node biopsy in early ovarian cancer cases.

Surface-Enhanced Raman Scattering Bioimaging with an Ultrahigh Signal-to-Background Ratio under Ambient Light

Surface-enhanced Raman scattering (SERS) nanoprobes have attracted particular interests in the field of bioimaging owing to their high sensitivity and specificity of the fingerprint spectrum. However, the limited signal-to-background ratio (SBR) in SERS imaging and the requirement to perform imaging in a dark environment have largely hindered its biomedical application. To circumvent this, we have developed a type of bio-orthogonal nanoprobes for SERS imaging with an ultrahigh SBR and ambient light anti-interference ability. The core-shell nanoprobes exhibit strongly enhanced Raman signals and depress the background from photoluminescence of metallic nanoparticles by off-resonance excitation and from the Raman scattering and auto-fluorescence of tissues by near-infrared laser excitation. Such nanoprobes have achieved an SBR of over 100 in SERS bioimaging, 5 times higher than the traditional on-resonant nanoprobes, and their bio-orthogonal signal in the Raman-silent region renders the anti-interference capability under ambient light. The development of these SERS probes opens up a new era for the future applications of Raman imaging in clinical medicine.

Radioactive polymeric nanoparticles for biomedical application

Nowadays, emerging radiolabeled nanosystems are revolutionizing medicine in terms of diagnostics, treatment, and theranostics. These radionuclides include polymeric nanoparticles (NPs), liposomal carriers, dendrimers, magnetic iron oxide NPs, silica NPs, carbon nanotubes, and inorganic metal-based nanoformulations. Between these nano-platforms, polymeric NPs have gained attention in the biomedical field due to their excellent properties, such as their surface to mass ratio, quantum properties, biodegradability, low toxicity, and ability to absorb and carry other molecules. In addition, NPs are capable of carrying high payloads of radionuclides which can be used for diagnostic, treatment, and theranostics depending on the radioactive material linked. The radiolabeling process of nanoparticles can be performed by direct or indirect labeling process. In both cases, the most appropriate must be selected in order to keep the targeting properties as preserved as possible. In addition, radionuclide therapy has the advantage of delivering a highly concentrated absorbed dose to the targeted tissue while sparing the surrounding healthy tissues. Said another way, radioactive polymeric NPs represent a promising prospect in the treatment and diagnostics of cardiovascular diseases such as cardiac ischemia, infectious diseases such as tuberculosis, and other type of cancer cells or tumors.

Development and characterization of an all-in-one gamma probe with auto-peak detection for sentinel lymph node biopsy based on NEMA NU3-2004 standard

Background

A gamma probe is a handheld device used for intraoperative interventions following interstitial injection of a radiotracer to locate regional lymph nodes through the external detection of radiation. This work reports on the design and performance evaluation of a novel fully integrated gamma probe (GammaPen), recently developed by our group.

Materials and methods

GammaPen is an all-in-one pocket gamma probe with low weight and adequate dimensions, consisting of a detector, a control unit and output all together. The detector module consists of a cylindrical Thallium-activated Cesium Iodide [CsI (Tl)] crystal optically coupled to a Silicon photomultiplier (SiPM), shielded using Tungsten housing on side and back faces. The electronics of the probe consists of two small boards to handle signal processing and analog peak detection tasks. A number of parameters, including probe sensitivity in air/water, spatial resolution in air/water, angular resolution in air/water, and side and back shielding effectiveness, were measured to evaluate the performance of the probe based on NEMA NU3-2004 standards.

Results

The sensitivity of the probe in air at distances of 10, 30, and 50 mm is 18784, 3500, and 1575 cps/MBq. The sensitivity in scattering medium was also measured at distances of 10, 30, and 50 mm as 17,680, 3050, and 1104 cps/MBq. The spatial and angular resolutions in scattering medium were 47 mm and 87 degree at 30 mm distance from the probe, while they were 40 mm and 77 degree in air. The detector shielding effectiveness and leakage sensitivity are 99.91% and 0.09%, respectively.

Conclusion

The performance characterization showed that GammaPen can be used effectively for sentinel lymph node localization. The probe was successfully used in several surgical interventions by an experienced surgeon confirming its suitability in a clinical setting.

In Vivo Dual-Modal Photoacoustic and Ultrasound Imaging of Sentinel Lymph Nodes Using a Solid-State Dye Laser System

Photoacoustic imaging (PAI) is being actively investigated as a non-invasive and non-radioactive imaging technique for sentinel lymph node (SLN) biopsy. By taking advantage of optical and ultrasound imaging, PAI probes SLNs non-invasively with methylene blue (MB) in both live animals and breast cancer patients. However, these PAI systems have limitations for widespread use in clinics and commercial marketplaces because the lasers used by the PAI systems, e.g., tunable liquid dye laser systems and optical parametric oscillator (OPO) lasers, are bulky in size, not economical, and use risky flammable and toxic liquid dyes. To overcome these limitations, we are proposing a novel dual-modal photoacoustic and ultrasound imaging system based on a solid-state dye laser (SD-PAUSI), which is compact, convenient, and carries far less risk of flammability and toxicity. Using a solid-state dye handpiece that generates 650-nm wavelength, we successfully imaged the MB tube positioned deeply (~3.9 cm) in chicken breast tissue. The SLNs were also photoacoustically detected in the in vivo rats beneath a 2.2-cm-thick layer of chicken breast, which is deeper than the typical depth of SLNs in humans (1.2 ± 0.5 cm). Furthermore, we showed the multispectral capability of the PAI by switching the dye handpiece, in which the MB-dyed SLN was selectively highlighted from the surrounding vasculature. These results demonstrated the great potential of the SD-PAUSI as an easy but effective modality for SLN detection.

Technetium-Radiolabeled Mannose-Functionalized Gold Nanoparticles as Nanoprobes for Sentinel Lymph Node Detection

Gold nanoparticles (AuNPs) are considered valuable nanomaterials for the design of radiolabeled nanoprobes for single-photon emission computed tomography (SPECT) imaging. Radiolabeled and functionalized AuNPs could improve lymphatic mapping by enhancing the radioactive signaling of individual particles in the sentinel node. In this study, an alternative method for functionalizing commercial AuNps with mannose is described. The chemical derivatization and biofunctionalization of AuNPs were performed with lipoic acid and mannose, respectively. Several levels of mannose were tested; the thiolate hydrazinonicotinamide-glycine-glycine-cysteine (HYNIC) molecule was also used for ^99mTc radiolabeling. Physicochemical characterization of this system includes U-V spectroscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, and transmission electron microscopy. The most stable nanoprobe, in terms of the aggregation, radiolabeling efficiency, and purity, was tested in a sentinel lymph node model in a rat by microSPECT/computed tomography (CT) imaging. The SPECT images revealed that ^99mTc-radiolabeled AuNPs functionalized with mannose can track and accumulate in lymph nodes in a similar way to the commercial ^99mTc-Sulfur colloid, commonly used in clinical practice for sentinel lymph node detection. These promising results support the idea that ^99mTc-AuNPs-mannose could be used as a SPECT contrast agent for lymphatic mapping.

Effect of delay between nuclear medicine scanning and sentinel node biopsy on outcome in patients with cutaneous melanoma

BACKGROUND

Sentinel lymph node biopsy (SLNB) is an important staging tool for the management of melanoma. A multicentre study was done to validate previous findings that the timing of lymphoscintigraphy influences the accuracy of SLNB and patient outcomes, particularly survival.

METHODS

Data were reviewed on patients undergoing SLNB for melanoma at three centres in the UK and Sweden, examining the effect of timing of SLNB after nuclear medicine scanning. Kaplan-Meier survival analysis was used to assess overall (OS), disease-specific (DSS) and progression-free (PFS) survival, stratified by timing of lymphoscintigraphy. Independent risk factors for survival were identified by Cox multivariable regression analysis.

RESULTS

A total of 2270 patients were identified. Median follow-up was 56 months. Univariable analysis showed a 4·2 per cent absolute and 35·5 per cent relative benefit in DSS (hazard ratio 1·36, 95 per cent c.i. 1·05 to 1·74; P = 0·018) for 863 patients whose SLNB was performed up to 12 h after lymphoscintigraphy compared with 1407 patients who had surgery after more than 12 h. There were similar OS and PFS benefits (P = 0·036 and P = 0·022 respectively). Multivariable analysis identified timing of lymphoscintigraphy as an independent predictor of OS (P = 0·017) and DSS (P = 0·030). There was an excess of nodal recurrences as first site of recurrence in the group with delayed surgery (4·5 versus 2·5 per cent; P = 0·008).

CONCLUSION

Delaying SLNB beyond 12 h after lymphoscintigraphy with ⁹⁹ Tc-labelled nanocolloid has a significant negative survival impact in patients with melanoma.

Survival outcomes and interval between lymphoscintigraphy and SLNB in cutaneous melanoma- findings of a large prospective cohort study

INTRODUCTION

Sentinel lymph node biopsy (SLNB) in cutaneous melanoma (CM) is performed to identify patient at risk of regional and distant relapse. We hypothesized that timing of lymphoscintigraphy may influence the accuracy of SLNB and patient outcomes.

METHODS

We reviewed prospective data on patients undergoing SLNB for CM at a large university cancer-center between 2008 and 2015, examining patient and tumor demographics and time between lymphoscintigraphy (LS) and SLNB. Kaplan-Meier survival analysis assessed disease-specific (DSS) and overall-survival (OS), stratified by timing of LS. Cox multivariate regression analysis assessed independent risk factors for survival.

RESULTS

We identified 1015 patients. Median follow-up was 45 months (IQR 26-68 months). Univariate analysis showed a 6.8% absolute DSS (HR 1.6 [1.03-2.48], p = 0.04) benefit and a 10.7% absolute OS (HR 1.64 [1.13-2.38], p = 0.01) benefit for patients whose SLNB was performed < 12 h of LS (n = 363) compared to those performed >12 h (n = 652). Multivariate analysis identified timing of LS as an independent predictor of OS (p = 0.007) and DSS (p = 0.016) when competing with age, sex, Breslow thickness (BT) and SLN status. No difference in nodal relapse rates (5.2% v 4.6%; p = 0.67) was seen. Both groups were matched for age, sex, BT and SLN status.

CONCLUSION

These data have significant implications for SLNB services, suggesting delaying SLNB >12 h after LS using a Tc99-labelled nanocolloid has a significant negative survival impact for patients and should be avoided. We hypothesise that temporal tracer migration is the underlying cause and advocate further trials investigating alternative, 'stable' tracer-agents.

Sentinel Node Study in Early Breast Cancer

Since October 1997 60 patients with early breast cancer (T <3 cm) were studied. All patients underwent lymphoscintigraphy with two types of colloid: the first (17 pts) with a particle size <1000 nm; the second (43 pts) with a particle size <80 nm. The standard procedure consists of injection, on the day before surgery, of 70 MBq of the smaller nanocolloid in 0.4 cc saline divided over four sites, around the lesion or subdermally around the surgical scar. We utilize a low-energy, high-resolution LFOV camera for scintigraphy and a probe specific for the sentinel node during surgery. In 56/60 patients (93.3%) lymphoscintigraphy showed the sentinel node (SN). In two cases the SN was not detected presumably because of lymphatic interruption by an old surgical scar; in the other two cases the sites of injection were too close to the SN, thus masking it. In five cases (9%) the SN was not visualized with the surgical probe but in two of these drainage to the internal mammary chain was observed. The apparently lower sensitivity of intraoperative localization was due to the extra-axillary lymphatic drainage or to the vicinity of the SN to the primary lesion. The SN proved to be metastatic in 12 cases. No false-negative SNs were found. In five cases (10%) the radiolabeled lymph node was the only node containing tumor cells (micrometastases): this result depends on the combined use of hematoxylin-eosin and rapid cytokeratin staining. The application of blue dye was useful for easier identification of the SN but did not allow detection of more SNs. Our preliminary results are extremely encouraging. Considering that at the early stages of breast cancer the likelihood of lymph node metastases is low (20% in our series) and no false negative were reported in this study, we conclude that with SN biopsy axillary lymph node dissection can be avoided, making surgery less aggressive but maintaining accuracy.

Translational radionanomedicine: a clinical perspective

Many nanomaterials were developed for the anticipated in vivo theranostic use exploiting their unique characteristics as a multifunctional platform. Nevertheless, only a few nanomaterials are under investigation for human use, most of which have not entered clinical trials yet. Radionanomedicine, a convergent discipline of radiotracer technology and use of nanomaterials in vivo, can facilitate clinical nanomedicine because of its advantages of radionuclide imaging and internal radiation therapy. In this review, we focuse on how radionanomedicine would impact profoundly on clinical translation of nanomaterial theranostics. Up-to-date advances and future challenges are critically reviewed regarding the issues of how to radiolabel and engineer radionanomaterials, in vivo behavior tracing of radionanomaterials and then the desired clinical radiation dosimetry. Radiolabeled extracellular vesicles were further discussed as endogenous nanomaterials radiolabeled for possible clinical use.

Nuclear molecular imaging with nanoparticles: radiochemistry, applications and translation

Molecular imaging provides considerable insight into biological processes for greater understanding of health and disease. Numerous advances in medical physics, chemistry and biology have driven the growth of this field in the past two decades. With exquisite sensitivity, depth of detection and potential for theranostics, radioactive imaging approaches have played a major role in the emergence of molecular imaging. At the same time, developments in materials science, characterization and synthesis have led to explosive progress in the nanoparticle (NP) sciences. NPs are generally defined as particles with a diameter in the nanometre size range. Unique physical, chemical and biological properties arise at this scale, stimulating interest for applications as diverse as energy production and storage, chemical catalysis and electronics. In biomedicine, NPs have generated perhaps the greatest attention. These materials directly interface with life at the subcellular scale of nucleic acids, membranes and proteins. In this review, we will detail the advances made in combining radioactive imaging and NPs. First, we provide an overview of the NP platforms and their properties. This is followed by a look at methods for radiolabelling NPs with gamma-emitting radionuclides for use in single photon emission CT and planar scintigraphy. Next, utilization of positron-emitting radionuclides for positron emission tomography is considered. Finally, recent advances for multimodal nuclear imaging with NPs and efforts for clinical translation and ongoing trials are discussed.

Underscoring the influence of inorganic chemistry on nuclear imaging with radiometals

Over the past several decades, radionuclides have matured from largely esoteric and experimental technologies to indispensible components of medical diagnostics. Driving this transition, in part, have been mutually necessary advances in biomedical engineering, nuclear medicine, and cancer biology. Somewhat unsung has been the seminal role of inorganic chemistry in fostering the development of new radiotracers. In this regard, the purpose of this Forum Article is to more visibly highlight the significant contributions of inorganic chemistry to nuclear imaging by detailing the development of five metal-based imaging agents: (64)Cu-ATSM, (68)Ga-DOTATOC, (89)Zr-transferrin, (99m)Tc-sestamibi, and (99m)Tc-colloids. In a concluding section, several unmet needs both in and out of the laboratory will be discussed to stimulate conversation between inorganic chemists and the imaging community.

Long-term multimodal imaging of tumor draining sentinel lymph nodes using mesoporous silica-based nanoprobes

The imaging of sentinel lymph nodes (SLNs), the first defense against primary tumor metastasis, has been considered as an important strategy for noninvasive tracking tumor metastasis in clinics. In this study, we report the development and application of mesoporous silica-based triple-modal nanoprobes that integrate multiple functional moieties to facilitate near-infrared optical, magnetic resonance (MR) and positron emission tomography (PET) imaging. After embedding near-infrared dye ZW800, the nanoprobe was labeled with T(1) contrast agent Gd(3+) and radionuclide (64)Cu through chelating reactions. High stability and long intracellular retention time of the nanoprobes was confirmed by in vitro characterization, which facilitate long-term in vivo imaging. Longitudinal multimodal imaging was subsequently achieved to visualize tumor draining SLNs up to 3 weeks in a 4T1 tumor metastatic model. Obvious differences in uptake rate, amount of particles, and contrast between metastatic and contra-lateral sentinel lymph nodes were observed. These findings provide very helpful guidance for the design of robust multifunctional nanomaterials in SLNs' mapping and tumor metastasis diagnosis.

In vivo quantitative evaluation of the transport kinetics of gold nanocages in a lymphatic system by noninvasive photoacoustic tomography

Sentinel lymph node (SLN) biopsy has emerged as a preferred method for axillary lymph node staging of breast cancer, and imaging the SLN in three-dimensional space is a prerequisite for the biopsy. Conventional SLN mapping techniques based on the injection of an organic dye or a suspension of radioactive colloids suffer from invasive surgical operation for visual detection of the dye or hazardous radioactive components and low spatial resolution of Geiger counters in detecting the radioactive colloids. This work systematically investigates the use of gold nanocages (AuNCs) as a novel class of optical tracers for noninvasive SLN imaging by photoacoustic (PA) tomography in a rat model. The transport of AuNCs in a lymphatic system and uptake by the SLN were evaluated by PA tomography on the axillary region of a rat. Quantification of AuNCs accumulated in the lymph node was achieved by correlating the data from PA imaging with the results from inductively coupled plasma mass spectrometry. Several parameters were systematically evaluated and optimized, including the concentration, size, and surface charge of the AuNCs. These results are critical to the further development of this AuNC-based PA tomography system for noninvasive SLN imaging, providing valuable information for metastatic cancer staging.

Guidelines for lymphoscintigraphy and F18 FDG PET scans in melanoma

Melanoma has a high potential to develop metastases. Accurate staging is essential for appropriate management. Sentinel node (SN) status is a powerful prognostic factor in early stage melanoma. Staging is assisted by SN biopsy after lymphoscintigraphy to locate all true SNs prior to biopsy. PET using F18-FDG can detect metastases and is used to restage patients with AJCC Stages III and IV disease before planning surgery with curative intent.

Nuclear probes and intraoperative gamma cameras

Gamma probes are now an important, well-established technology in the management of cancer, particularly in the detection of sentinel lymph nodes. Intraoperative sentinel lymph node as well as tumor detection may be improved under some circumstances by the use of beta (negatron or positron), rather than gamma detection, because the very short range (∼ 1 mm or less) of such particulate radiations eliminates the contribution of confounding counts from activity other than in the immediate vicinity of the detector. This has led to the development of intraoperative beta probes. Gamma camera imaging also benefits from short source-to-detector distances and minimal overlying tissue, and intraoperative small field-of-view gamma cameras have therefore been developed as well. Radiation detectors for intraoperative probes can generally be characterized as either scintillation or ionization detectors. Scintillators used in scintillation-detector probes include thallium-doped sodium iodide, thallium- and sodium-doped cesium iodide, and cerium-doped lutecium orthooxysilicate. Alternatives to inorganic scintillators are plastic scintillators, solutions of organic scintillation compounds dissolved in an organic solvent that is subsequently polymerized to form a solid. Their combined high counting efficiency for beta particles and low counting efficiency for 511-keV annihilation γ-rays make plastic scintillators well-suited as intraoperative beta probes in general and positron probes in particular Semiconductors used in ionization-detector probes include cadmium telluride, cadmium zinc telluride, and mercuric iodide. Clinical studies directly comparing scintillation and semiconductor intraoperative probes have not provided a clear choice between scintillation and ionization detector-based probes. The earliest small field-of-view intraoperative gamma camera systems were hand-held devices having fields of view of only 1.5-2.5 cm in diameter that used conventional thallium-doped sodium iodide or sodium-doped cesium iodide scintillation detectors. Later units used 2-dimensional arrays (mosaics) of scintillation crystals connected to a position-sensitive photomultiplier tube and, more recently, semiconductors such as cadmium telluride or cadmium zinc telluride. The main problems with the early units were their very small fields of view and the resulting large number of images required to interrogate the surgical field and the difficulty in holding the device sufficiently still for the duration (up to 1 min) of the image acquisition. More recently, larger field-of-view (up to 5 × 5 cm) devices have developed which are attached to an articulating arm for easy and stable positioning. These systems are nonetheless fully portable and small enough overall to be accommodated in typical surgical suites.

[Evaluation of the sentinel lymph node combining SPECT/CT with the planar image and its importance for the surgical act]

The sentinel node biopsy procedure is based on the hypothesis of the existence of an orderly and predictable pattern of lymphatic drainage to a regional lymph node basin. This results in the consideration of all lymph nodes with direct drainage from the primary tumor as sentinel nodes. The sentinel node is not necessarily the hottest or the most nearby node, although this is often the case. Lymphoscintigraphy has been an essential component for preoperative sentinel node identification. With the new generation of multimodality gamma cameras, SPECT/CT has been incorporated into the sentinel node procedure. The resulting SPECT/CT fused images depict sentinel nodes in an anatomical landscape providing a helpful roadmap for surgeons. Therefore, it is necessary to define the role of SPECT/CT in relation to the classical planar lymphoscintigraphy for the identification of sentinel nodes. To understand the combined use of lymphoscintigraphy and SPECT/CT, the criteria for sentinel node identification on preoperative images must be specified. The authors, based on their experience in this field, present tentative criteria to identify lymph nodes as sentinel nodes both in planar and SPECT/CT images and classify them into different categories. The use of these scintigraphic categories to characterize radioactive lymph nodes is also helpful for surgical decision making.

Mapping of lymphatic drainage from the prostate using filtered 99mTc-sulfur nanocolloid and SPECT/CT

We have developed a practice procedure for prostate lymphoscintigraphy using SPECT/CT and filtered (99m)Tc-sulfur nanocolloid, as an alternative to the proprietary product (99m)Tc-Nanocoll, which is not approved in the United States.

METHODS

Ten patients were enrolled for this study, and all received radiotracer prepared using a 100-nm membrane filter at a commercial radiopharmacy. Whole-body scans and SPECT/CT studies were performed within 1.5-3 h after the radiotracer had been administered directly into 6 locations of the prostate gland under transrectal ultrasound guidance. The radiation dose was estimated from the first 3 patients. Lymphatic drainage mapping was performed, and lymph nodes were identified.

RESULTS

The estimated radiation dose ranged from 3.9 to 5.2 mSv/MBq. The locations of lymph nodes draining the prostate gland were similar to those found using the proprietary product.

CONCLUSION

When the proprietary radiolabeled nanocolloid indicated for lymphoscintigraphy is not available, prostate lymph node mapping and identification are still feasible using filtered (99m)Tc-sulfur nanocolloid.

Animal models and molecular imaging tools to investigate lymph node metastases

Lymph node metastasis is a strong predictor of poor outcome in cancer patients. Animal studies of lymph node metastasis are constrained by difficulties in the establishment of appropriate animal models, limitations in the noninvasive monitoring of lymph node metastasis progression, and challenges in the pathologic confirmation of lymph node metastases. In this comprehensive review, we summarize available preclinical animal cancer models for noninvasive imaging and identification of lymph node metastases of non-hematogenous cancers. Furthermore, we discuss the strengths and weaknesses of common noninvasive imaging modalities used to identify tumor-bearing lymph nodes and provide guidelines for their pathological confirmation.

Sentinel lymph node identification with radiopharmaceuticals in patients with breast cancer: a comparison of 99mTc-tin colloid and 99mTc-phytate efficiency

Sentinel lymph node biopsy with lymphoscintigraphy has become the standard method for the detection of axillary lymph node metastasis in breast cancer patients. However, there is no standardized radiopharmaceutical. For the detection of axillary lymph node metastasis by lymphoscintigraphy and sentinel node biopsy in patients with breast cancer, we compared the results between subareolar injection of (99m)Tc-tin colloid and injection of (99m)Tc-phytate. This study included 516 breast cancer patients who underwent surgery between 2001 and 2010. Among the 516 patients, (99m)Tc-tin colloid (37-185 MBq) was administered to 412 patients by subareolar injection, and (99m)Tc-phytate (37-185 MBq) was injected in 104 patients. Lymphoscintigraphy was performed with the patients in the supine position, and sentinel node identification was performed by hand-held gamma probe during surgery. Among 412 patients with (99m)Tc-tin colloid, the sentinel node was identified by lymphoscintigraphy in 364 cases (88.3%) and by a gamma probe in 369 cases (89.6%). Among 104 patients with (99m)Tc-phytate, 101 cases (97.1%) were identified by lymphoscintigraphy and 101 cases (97.1%) were identified by a gamma probe. The identification rates by lymphoscintigraphy and gamma probe were superior with (99m)Tc-phytate, as compared with (99m)Tc-tin colloid, with a statistically significant difference (P < 0.05 for both methods). (99m)Tc-phytate is a better choice than (99m)Tc-tin colloid for identification of the sentinel node in breast cancer patients.

Therapeutic sentinel lymph node imaging

Improving existing means of sentinel lymph node identification in non-small cell lung cancer will allow for molecular detection of occult micrometastases that may cause recurrence in early stage non-small cell lung cancer. Furthermore, targeted application of chemical and biological cytotoxic agents can potentially improve outcomes in patients with lymph node (LN) metastases. "Therapeutic Sentinel Lymph Node Imaging" incorporates these modalities into a single agent thereby identifying which LNs harbor tumor cells and simultaneously eradicating metastatic disease. In this review, we summarize the novel preclinical agents for identification and treatment of tumor bearing LNs and discuss their potential for clinical translation.

SPECT/CT for preoperative sentinel node localization

The value of SPECT/CT for detection and localization of sentinel nodes is reviewed. SPECT/CT depicts extra sentinel nodes and identifies non-nodal tracer accumulation. SPECT/CT is indicated in patients with complex lymphatic drainage as often present in patients with head, neck and scapular melanoma, breast cancer patients with extra-axillary sentinel nodes and patients with tumors draining to pelvic nodes. SPECT/CT also clarifies the drainage pattern of inconclusive conventional images (non-visualization or unclear location of the nodes).

EANM-EORTC general recommendations for sentinel node diagnostics in melanoma

The accurate diagnosis of a sentinel node in melanoma includes a sequence of procedures from different medical specialities (nuclear medicine, surgery, oncology, and pathology). The items covered are presented in 11 sections and a reference list: (1) definition of a sentinel node, (2) clinical indications, (3) radiopharmaceuticals and activity injected, (4) dosimetry, (5) injection technique, (6) image acquisition and interpretation, (7) report and display, (8) use of dye, (9) gamma probe detection, (10) surgical techniques in sentinel node biopsy, and (11) pathological evaluation of melanoma-draining sentinel lymph nodes. If specific recommendations given cannot be based on evidence from original, scientific studies, referral is given to "general consensus" and similar expressions. The recommendations are designed to assist in the practice of referral to, performance, interpretation and reporting of all steps of the sentinel node procedure in the hope of setting state-of-the-art standards for good-quality evaluation of possible spread to the lymphatic system in intermediate-to-high risk melanoma without clinical signs of dissemination.

The use of fluorescent dyes and probes in surgical oncology

AIMS AND BACKGROUND

Improved visualization of surgical targets inside of the patient helps to improve radical resection of the tumor while sparing healthy surrounding tissue. In order to achieve an image, optical contrast must be generated by properties intrinsic to the tissue, or require the attachment of special visualization labels to the tumor. In this overview the current status of the clinical use of fluorescent dyes and probes are reviewed.

METHODS

In this review, all experimental and clinical studies concerning fluorescent imaging were included. In addition, in the search for the optimal fluorescent imaging modality, all characteristics of a fluorescent dye were described.

FINDINGS AND CONCLUSIONS

Although the technique of imaging through fluorescence sounds promising and several animal models show efficacy, official approval of these agents for further clinical evaluation, is eagerly awaited.

Stability of the mixture of technetium-99m human serum albumin and lidocaine hydrochloride for clinical application

AIM

To evaluate the stability of the mixture of technetium-99m (99mTc) human serum albumin (HSA) with the local anesthetic lidocaine hydrochloride.

MATERIALS AND METHODS

We assessed three preparations of the radiotracer, 99mTc-HSA, filtered 99mTc-HSA, and a mixture of 99mTc-HSA with lidocaine hydrochloride and then filtered. Time sequence evaluation was performed on all the specimens (n= 10) at 0, 30, 60, 90, 120, 150, and 180 min after preparation. Measurements of radiochemical purity as labeling stability and pH value change were conducted for each group of specimens.

RESULTS

We found no definite difference in the stability before and after the filtering procedure for 99mTc-HSA. However, we showed a decline of stability in the mixture of 99mTc-HSA with lidocaine. The filtered specimens showed a relatively higher pH value, towards a more neutral status, as compared with the unfiltered specimens.

CONCLUSION

Though pain relief for the patient receiving sentinel lymph node mapping is important, a preparation of a mixture of 99mTc-HSA and lidocaine may cause radiolabeling instability. Furthermore, compared with the filtered 99mTc-sulfur colloid, a filtering procedure does not change the labeling stability of the 99mTc-HSA. On the contrary, the filtered preparation was neutralized closer to the physiologic condition. For lymphoscintigraphic studies,our results suggested that pretreatment with local anesthesia followed by subdermal injection of a filtered 99mTc-HSA rather than a pre-mixture with lidocaine is appropriate for clinical application.

Noninvasive in vivo spectroscopic nanorod-contrast photoacoustic mapping of sentinel lymph nodes

Sentinel lymph node (SLN) biopsy has increasingly become important in axillary staging of breast cancer patients since SLN biopsy alleviates the postoperative complications of previously practiced axillary lymph node dissections. Nevertheless, the procedures of SLN biopsy using blue dye and radioactive substance are still intraoperative, and the latter methods are also ionizing. In this pilot study, we have proposed noninvasive in vivo spectroscopic photoacoustic (PA) SLN mapping using gold nanorods as lymph node tracers in a rat model. Gold nanorods have biocompatibility, high optical absorption, and easily tuned surface plasmon resonance peak wavelength.

Lymphatic mapping with 99mTc-Evans Blue dye in sheep

OBJECTIVE

99mTc-Evans Blue (EB) is an agent that contains both radioactive and color signals in a single dose. Earlier studies in animal models have suggested that this agent when compared with the dual-injection technique of radiocolloid/blue dye can successfully discriminate the sentinel lymph node. The aim of this study was to investigate the potential of 99mTc-EB as an agent to map the lymphatic system in an ovine model.

METHODS

Doses of 99mTc-EB (23 MBq) containing EB dye (4 mg) were administered intradermally to the limbs of four anesthetized sheep, and they were then imaged over 20-30 min using a gamma camera. The study protocol was repeated using 99mTc-antimony trisulfide colloid (ATC) and Patent Blue V dye. The lymph nodes (popliteal, inguinal, and iliac for hind limbs or prescapular for fore limbs) were identified with a gamma probe during the operative exposure, then dissected and counted in a large volume counter.

RESULTS

Simple and complex (dual) drainage patterns were visible on the scans, and the sentinel node was more radioactive than higher tier nodes in a chain, for both radiotracers. For 99mTc-EB, maximum radioactive uptake was achieved at 3-6 min for popliteal lymph nodes, 12-14 min for iliac nodes, and 13-14 min for prescapular nodes. 99mTc-ATC resulted in maximum radioactive uptake at 4-6 min for popliteal lymph nodes, 13 min for an inguinal node, 13-20 min for iliac nodes, and 18 min for a prescapular node. Following 99mTc-EB injection, 15/15 lymph nodes harvested were all radioactive and blue. For 99mTc-radiocolloid/Patent Blue V injection, 8/14 nodes were radioactive and blue, and 6/14 nodes were radioactive only.

CONCLUSIONS

The soluble radiotracer 99mTc-EB appeared to be a useful lymphoscintigraphic agent in sheep, in which radioactive counts from superficial lymphatic channels and lymph nodes were sufficient for planar imaging. In comparison with 99mTc-antimony trisulfide colloid, both tracers discriminated the sentinel lymph node up to 50 min after administration; however, 99mTc-EB had the advantage of providing radioactive (gamma probe) and color signals simultaneously during the operative exposure.

Differential receptor targeting of liver cells using 99mTc-neoglycosylated human serum albumins

Neolactosyl human serum albumin (LSA) targets asialoglycoprotein receptor and shows high liver uptake due to accumulation in hepatocytes. Although neomannosyl human serum albumin (MSA) also shows high liver uptake, it has been reported to be taken up by Kupffer cells and endothelial cells. We compared the biological properties of LSA and MSA. 99mTc-LSA and 99mTc-MSA biodistribution in mice were investigated after intravenous injection. In vivo localization of rhodaminisothiocyanate (RITC)-LSA and fluoresceineisothiocyanate (FITC)-MSA were investigated in mouse liver. Excretion routes of 99mTc-LSA and 99mTc-MSA metabolites were examined. Both 99mTc-LSA and 99mTc-MSA showed high liver uptakes. RITC-LSA was taken up by hepatocytes whereas FITC-MSA was taken up by Kupffer cells and endothelial cells. 99mTc-MSA showed higher spleen and kidney uptakes than 99mTc-LSA. 99mTc-LSA metabolites excreted in urine and feces accounted for 44.4 and 50.0% of 99mTc-LSA injected, respectively, while 99mTc-MSA metabolites accounted for 51.5 and 10.3%, respectively. In conclusion, LSA is specifically taken up by hepatcytes while MSA by Kupffer cells and endothelial cells. After taken up by the liver, LSA is metabolized by the hepatocytes and then excreted through both the hepatobiliary tract and kidney, whereas MSA is metabolized by Kupffer cells and endoghelial cells and then excreted mainly through the kidney.

Preoperative lymphoscintigraphy predicts the successful identification but is not necessary in sentinel lymph nodes biopsy in breast cancer

BACKGROUND

Although preoperative lymphoscintigraphy in sentinel lymph node biopsy (SLNB) for breast cancer patients is undergone commonly, its clinical significance remains controversial.

METHODS

We retrospectively analyzed our database that contained 636 consecutive breast cancer patients who received preoperative lymphoscintigraphy before SLNB.

RESULTS

The sentinel lymph nodes (SLNs) of 86.5% of patients were well imaged by lymphoscintigraphy, and SLN were located extra-axilla in 5.3% patients. The visualization of SLN in lymphoscintigraphy was not associated with histopathologic type, location, and stage of primary tumor, as well as the time interval from injection of radiocolloid to surgery. The negative lymphoscintigraphy results were associated with excision ;biopsy before injection of radiocolloid and positive axillary node statues. The SLN was successfully detected in 625 (98.3%) enrolled patients. Failure of surgical identification of axillary SLN was associated with whether hot spot was imaged by lymphoscintigraphy. However, we identified axillary SLN in 90 (90.9%) out of 99 patients with negative axillary findings in lymphoscintigram. The false negative rate of SLNB in our study was 16.0% (15 of 94) among patients of training group, and there was no significant difference in the false negative rate between patients who had axillary hot spot in lymphoscintigram and those who had not (P = .273).

CONCLUSIONS

Visualization of SLN in preoperative lymphoscintigraphy predicted the successful SLN identification. However, it was less informative for the location of SLN during operation. Considering the complexity, time consumed, and cost, lymphoscintigraphy should at present be undergone for investigation purposes only.

Validation and application of the sentinel lymph node concept in malignant vulvar tumours

PURPOSE

Inguinal lymphadenectomy, unilateral or bilateral, is widely used in cases of vulvar squamous cell carcinoma and melanoma but has a high morbidity. Sentinel lymph node (SLN) biopsy may be used in the management of these patients. The aims of this study were firstly to determine the reliability of SLN biopsy in predicting regional lymph node status and secondly to apply this technique in the routine clinical setting.

METHODS

We prospectively studied 70 women with vulvar malignancies. The first 50 cases were of squamous vulvar cancer and were used to validate the SLN technique in this clinical setting (validation group). Once a satisfactory success rate had been achieved in the validation group, the SLN technique was applied to a further 20 patients with vulvar malignancies, i.e. squamous cell carcinoma (n=12) and melanomas (n=8) (application group). Dynamic and static images were acquired after the injection of 74-148 MBq of a colloidal albumin, and continued until SLN identification. Fifteen minutes before surgery, blue dye injection was administered in a similar manner to the radiocolloid. After incision, a hand-held gamma probe was used to find the SLN. In the validation group, dissection of the SLN was always followed by lymphadenectomy. In the application group, this procedure was only performed if the SLN was positive for metastases. For pathological staging, samples were evaluated using haematoxylin and eosin and immunohistochemistry.

RESULTS

In the validation group, lymphoscintigraphy allowed SLN detection in 49/50 patients (98%). Blue dye detected the SLN in 40/50 patients (80%). In 16 patients (33%), the SLN showed metastases in the pathology study. All 33 patients with negative SLN had regional lymph nodes negative for metastases (negative predictive value 100%). In the application group, lymphoscintigraphy showed drainage to an SLN in 19 out of 20 patients (95%) and blue dye demonstrated a stained SLN in 17/20 patients (85%). Seven of the 19 SLN-identified nodes (37%) were positive for metastases.

CONCLUSION

SLN identification permits the accurate pathological study of regional nodes and could reduce the high morbidity of current surgical treatment in vulvar tumour patients if the technique were to be adopted on a routine clinical basis.

The Role of Lymphoscintigraphy in the Detection of Lymph Node Drainage in Melanoma

Lymphatic drainage of the skin cannot be predicted based on clinical guidelines developed more than 100 years ago. Approximately 30% of patients experience drainage from the skin to unexpected lymph node sites rather than those specified by these guidelines, and therefore these outdated assumptions should no longer be used to plan surgery. A possible survival benefit has been shown for the early detection and surgical removal of metastatic disease in the draining lymph nodes, and therefore, clinicians must obtain accurate lymphatic mapping for each patient who has intermediate thickness melanoma to plan appropriate surgical therapy. Lymphoscintigraphy can be used to accurately define the precise position of each true sentinel node in every patient, whether these nodes lie in a standard node field or in an unusual location. In this way, lymphoscintigraphy has a direct beneficial impact on the surgical management of patients who have melanoma.

Sentinel lymph node mapping of the gastrointestinal tract by using invisible light

BACKGROUND

Because many gastrointestinal (GI) tumors spread by way of lymphatics, histological assessment of the first draining lymph nodes has both prognostic and therapeutic significance. However, sentinel lymph node mapping of the GI tract by using available techniques is limited by unpredictable drainage patterns, high background signal, and the inability to image lymphatic tracers relative to surgical anatomy in real time. Our goal was to develop a method for patient-specific intraoperative sentinel lymph node mapping of the GI tract by using invisible near-infrared light.

METHODS

We developed an intraoperative near-infrared fluorescence imaging system that simultaneously displays surgical anatomy and otherwise invisible near-infrared fluorescence images of the surgical field. Near-infrared fluorescent quantum dots were injected intraparenchymally into the stomach, small bowel, and colon, and draining lymphatic channels and sentinel lymph nodes were visualized. Dissection was performed under real-time image guidance.

RESULTS

In 10 adult pigs, we demonstrated that 200 pmol of quantum dots quickly and accurately map lymphatic drainage and sentinel lymph nodes. Injection into the mid jejunum and colon results in fluorescence of a single lymph node at the root of the bowel mesentery. Injection into the stomach resulted in identification of a retrogastric node. Histological analysis in all cases confirmed the presence of nodal tissue.

CONCLUSIONS

We report the use of invisible near-infrared light for intraoperative sentinel lymph node mapping of the GI tract. This technology overcomes the limitations of currently available methods, permits patient-specific imaging of lymphatic flow and sentinel nodes, and provides highly sensitive, real-time image-guided dissection.

Lymphatic mapping in management of patients with primary cutaneous melanoma

In patients with primary cutaneous melanoma, knowledge of regional lymph-node status provides important information on outlook. Evidence suggests that early removal of nodes that contain metastatic disease improves survival outcome. Lymphatic drainage occurs first to sentinel nodes, which are therefore the nodes most likely to contain metastatic disease. Lymphatic mapping with lymphoscintigraphy is important to identify reliably sentinel nodes for removal and thus establish the status of regional nodes. Mapping studies in patients with melanoma have provided new insights into lymphatic anatomy and have shown previously unsuspected drainage pathways, which have important implications for accurate identification and removal of sentinel nodes. Because it is impossible to predict the site or sites of sentinel nodes clinically in individual patients, routine preoperative lymphoscintigraphy is a prerequisite if reliable results are to be obtained from sentinel-node biopsy.

Intraoperative sentinel lymph node mapping of the lung using near-infrared fluorescent quantum dots

BACKGROUND

The presence of lymph node metastases is an important prognostic marker with regard to non-small-cell lung cancer (NSCLC). Assessment of the sentinel lymph node (SLN) for the presence of tumor may improve staging. Our objective was to develop an optical noninvasive imaging tool that would permit intraoperative SLN mapping and provide real-time visual feedback for image-guided localization and resection.

METHODS

Invisible near-infrared (NIR) light penetrates relatively deeply into tissue and background autofluorescence is low. We have developed a NIR fluorescence imaging system that simultaneously displays color video and NIR images of the surgical field. We recently engineered 15 nm nonradioactive NIR fluorescent quantum dots (QDs) as optimal lymphotrophic optical probes. The introduction of these QDs into lung tissue allows real-time visualization of draining lymphatic channels and nodes.

RESULTS

In 12 Yorkshire pigs (mean weight 35 kg) we demonstrated that 200 pmol of NIR QDs injected into lobar parenchyma accurately maps lymphatic drainage and the SLN. All SLNs were strongly fluorescent and easily visualized within 5 minutes of injection. In 14 separate injections QDs localized to a mediastinal node, whereas in 2 injections QDs localized to a hilar intraparenchymal node. Histologic analysis in all cases confirmed the presence of nodal tissue.

CONCLUSIONS

We report a highly sensitive rapid technique for SLN mapping of the lung. This technique permits precise real-time imaging and therefore overcomes many limitations of currently available techniques.

Value of nodal drainage patterns and tumor location from lymphoscintigraphic mapping in detecting axillary sentinel lymph node status in breast cancer: experience at Kaohsiung Medical University Hospital

Sentinel lymph node (SLN) biopsy is an alternative to axillary node dissection for staging breast cancer treatment. In this article, we investigated nodal drainage patterns and tumor location using lymphoscintigraphy to predict the axillary sentinel lymph node status. We enrolled 88 patients with clinically suspicious or biopsy-proven breast cancer from March 2001 to October 2002. The average age of subjects was 48 +/- 4 years and the clinical stage was T(1-2)N0Mx. Tc-99m sulfur colloid was used in a hybrid combination of subdermal and perilesional injections around the selected comers of the tumor or biopsy site. Sentinel lymphoscintigraphy was performed 16-20 hours before surgery. Sentinel nodes were marked on the skin. An intraoperative gamma probe was used to confirm the sentinel lymph node location before biopsy. Most primary tumors were in the outer upper quadrant (52.3%), followed by the inner upper quadrant (17.0%), outer inferior quadrant (12.5%), central areolar area (11.4%), and inner inferior quadrant (6.8%). The nodal drainage patterns on 2-hour lymphoscintigraphy were as follows: axillary alone (76.1%), internal mammary nodes alone (1.1%), both axillary and internal mammary nodes (11.4%), and no drainage (11.4%). Internal mammary lymphatic drainage is related to tumor location in the inner quadrants of the breast. About 11.4% of all patients had poorly identified SLNs on lymphoscintigraphy within a 2-hour period, but there was improvement in the overall detection rate up to 95% by intraoperative gamma probe the next day. Preoperative lymphoscintigraphic mapping has value in providing individual lymphatic drainage patterns and tumor location that are important in the interpretation of the results of SLN biopsy during surgery.