Multimodal hybrid imaging agents for sentinel node mapping as a means to (re)connect nuclear medicine to advances made in robot-assisted surgery

A new bimodal approach for sentinel lymph node imaging in prostate cancer using a magnetic and fluorescent hybrid tracer

PURPOSE

To obtain initial data on sentinel lymph node (SLN) visualisation by pre-operative magnetic resonance imaging (MRI) and intra-operative bimodal SLN identification using a new magnetic fluorescent hybrid tracer in prostate cancer (PCa) patients.

METHODS

Ten patients at > 5% risk for lymph node (LN) invasion were included. The day before surgery, a magnetic fluorescent hybrid tracer consisting of superparamagnetic iron oxide nanoparticles (SPION) and indocyanine green was transrectally injected into the prostate. Five hours after injection, transversal pelvic MRI scans were recorded and T2*-weighed images were screened for pelvic LNs with SPION uptake. Intra-operatively, magnetically active and/or fluorescent SLNs were detected by a handheld magnetometer and near-infrared fluorescence imaging (FI). Extended pelvic lymph node dissection (PLND) and radical prostatectomy completed the surgery. All resected specimens were checked ex situ for magnetic activity and fluorescence and were histopathologically examined.

RESULTS

Pre-operative MRI identified 145 pelvic LNs with SPION uptake. In total, 75 (median 6, range 3‒13) magnetically active SLNs were resected, including 14 SLNs not seen on MRI. FI identified 89 fluorescent LNs (median 8.5, range 4‒13) of which 15 LNs were not magnetically active. Concordance of the different techniques was 70% for pre-operative MRI vs. magnetometer-guided PLND and 88% for magnetic vs. fluorescent SLN detection.

CONCLUSION

These are the first promising results of bimodal, magnetic fluorescent SLN detection in PCa patients. Our magnetic fluorescent hybrid approach provides the surgeon a pre-operative lymphatic roadmap by using MRI and intra-operative visual guidance through the application of a fluorescent lymphatic agent. The diagnostic accuracy of our new hybrid approach has to be evaluated in further studies.

TRIAL REGISTRATION

DRKS00032808. Registered 04 October 2023, retrospectively registered.

A Systematic Review of New Imaging Technologies for Robotic Prostatectomy: From Molecular Imaging to Augmented Reality

New imaging technologies play a pivotal role in the current management of patients with prostate cancer. Robotic assisted radical prostatectomy (RARP) is a standard of care for localized disease and through the already imaging-based console subject of research towards combinations of imaging technologies and RARP as well as their impact on surgical outcomes. Therefore, we aimed to provide a comprehensive analysis of the currently available literature for new imaging technologies for RARP. On 24 January 2023, we performed a systematic review of the current literature on Pubmed, Scopus and Web of Science according to the PRISMA guidelines and Oxford levels of evidence. A total of 46 studies were identified of which 19 studies focus on imaging of the primary tumor, 12 studies on the intraoperative tumor detection of lymph nodes and 15 studies on the training of surgeons. While the feasibility of combined approaches using new imaging technologies including MRI, PSMA-PET CT or intraoperatively applied radioactive and fluorescent dyes has been demonstrated, the prospective confirmation of improvements in surgical outcomes is currently ongoing.

A hybrid radioactive and fluorescence approach is more than the sum of its parts; outcome of a phase II randomized sentinel node trial in prostate cancer patients

OBJECTIVE

To determine the diagnostic accuracy of the hybrid tracer indocyanine green (ICG)-Technetium-99 m(99mTc)-nanocolloid compared to sequential tracers of 99mTc-nanocolloid and free-ICG in detecting tumor-positive lymph nodes (LN) during primary surgery in prostate cancer (PCa) patients.

INTRODUCTION

Image-guided surgery strategies can help visualize individual lymphatic drainage patterns and sentinel lymph nodes (SLNs) in PCa patients. For lymphatic mapping radioactive, fluorescent and hybrid tracers are being clinically exploited. In this prospective randomized phase II trial, we made a head-to-head comparison between ICG-99mTc-nanocolloid (hybrid group) and 99mTc-nanocolloid and subsequent free-ICG injection (sequential group).

METHODS

PCa patients with a  >5% risk of lymphatic involvement according to the 2012 Briganti nomogram and planned for prostatectomy were included and randomized (1:1) between ultrasound-guided intraprostatic tracer administration of ICG-99mTc-nanocolloid (n = 69) or 99mTc-nanocolloid (n = 69) 5 h before surgery. Preoperative lymphoscintigraphy and SPECT/CT were performed to define the locations of the SLNs. Additionally, all participants in the sequential group received an injection of free-ICG at time of surgery. Subsequently, all (S)LNs were dissected using fluorescence guidance followed by an extended pelvic lymph node dissection (ePLND). The primary outcome was the total number of surgically removed (S)LNs and tumor-positive (S)LNs.

RESULTS

The total number of surgically removed (S)LN packages was 701 and 733 in the hybrid and sequential groups, respectively (p = 0.727). The total number of fluorescent LNs retrieved was 310 and 665 nodes in the hybrid and sequential groups, respectively (p < 0.001). However, no statistically significant difference was observed in the corresponding number of tumor-positive nodes among the groups (44 vs. 33; p = 0.470). Consequently, the rate of tumor-positive fluorescent LNs was higher in the hybrid group (7.4%) compared to the sequential group (2.6%; p = 0.002), indicating an enhanced positive predictive value for the hybrid approach. There was no difference in complications within 90 days after surgery (p = 0.78).

CONCLUSIONS

The hybrid tracer ICG-99mTc-nanocolloid improved the positive predictive value for tumor-bearing LNs while minimizing the number of fluorescent nodes compared to the sequential tracer approach. Consequently, the hybrid tracer ICG-99mTc-nanocolloid enables the most reliable and minimal invasive method for LN staging in PCa patients.

Quantifying the Impact of Signal-to-background Ratios on Surgical Discrimination of Fluorescent Lesions

PURPOSE

Surgical fluorescence guidance has gained popularity in various settings, e.g., minimally invasive robot-assisted laparoscopic surgery. In pursuit of novel receptor-targeted tracers, the field of fluorescence-guided surgery is currently moving toward increasingly lower signal intensities. This highlights the importance of understanding the impact of low fluorescence intensities on clinical decision making. This study uses kinematics to investigate the impact of signal-to-background ratios (SBR) on surgical performance.

METHODS

Using a custom grid exercise containing hidden fluorescent targets, a da Vinci Xi robot with Firefly fluorescence endoscope and ProGrasp and Maryland forceps instruments, we studied how the participants' (N = 16) actions were influenced by the fluorescent SBR. To monitor the surgeon's actions, the surgical instrument tip was tracked using a custom video-based tracking framework. The digitized instrument tracks were then subjected to multi-parametric kinematic analysis, allowing for the isolation of various metrics (e.g., velocity, jerkiness, tortuosity). These were incorporated in scores for dexterity (Dx), decision making (DM), overall performance (PS) and proficiency. All were related to the SBR values.

RESULTS

Multi-parametric analysis showed that task completion time, time spent in fluorescence-imaging mode and total pathlength are metrics that are directly related to the SBR. Below SBR 1.5, these values substantially increased, and handling errors became more frequent. The difference in Dx and DM between the targets that gave SBR < 1.50 and SBR > 1.50, indicates that the latter group generally yields a 2.5-fold higher Dx value and a threefold higher DM value. As these values provide the basis for the PS score, proficiency could only be achieved at SBR > 1.55.

CONCLUSION

By tracking the surgical instruments we were able to, for the first time, quantitatively and objectively assess how the instrument positioning is impacted by fluorescent SBR. Our findings suggest that in ideal situations a minimum SBR of 1.5 is required to discriminate fluorescent lesions, a substantially lower value than the SBR 2 often reported in literature.

The application of indocyanine green in guiding prostate cancer treatment

Objective

Indocyanine green (ICG) with near-infrared fluorescence absorption is approved by the United States Food and Drug Administration for clinical applications in angiography, blood flow evaluation, and liver function assessment. It has strong optical absorption in the near-infrared region, where light can penetrate deepest into biological tissue. We sought to review its value in guiding prostate cancer treatment.

Methods

All related literature at PubMed from January 2000 to December 2020 were reviewed.

Results

Multiple preclinical studies have demonstrated the usefulness of ICG in identifying prostate cancer by using different engineering techniques. Clinical studies have demonstrated the usefulness of ICG in guiding sentinel node dissection during radical prostatectomy, and possible better preservation of neurovascular bundle by identifying landmark prostatic arteries. New techniques such as adding fluorescein in additional to ICG were tested in a limited number of patients with encouraging result. In addition, the use of the ICG was shown to be safe. Even though there are encouraging results, it does not carry sufficient sensitivity and specificity in replacing extended pelvic lymph node dissection during radical prostatectomy.

Conclusion

Multiple preclinical and clinical studies have shown the usefulness of ICG in identifying and guiding treatment for prostate cancer. Larger randomized prospective studies are warranted to further test its usefulness and find new modified approaches.

The impact of drainage pathways on the detection of nodal metastases in prostate cancer: a phase II randomized comparison of intratumoral vs intraprostatic tracer injection for sentinel node detection

INTRODUCTION

Previous studies indicated that location and amount of detected sentinel lymph nodes (SLNs) in prostate cancer (PCa) are influenced where SLN-tracer is deposited within the prostate. To validate whether intratumoral (IT) tracer injection helps to increase identification of tumor-positive lymph nodes (LNs) better than intraprostatic (IP) tracer injection, a prospective randomized phase II trial was performed.

METHODS

PCa patients with a > 5% risk of lymphatic involvement were randomized between ultrasound-guided transrectal injection of indocyanine green-[^99mTc]Tc-nanocolloid in 2 depots of 1 mL in the tumor (n = 55, IT-group) or in 4 depots of 0.5 mL in the peripheral zone of the prostate (n = 58, IP-group). Preoperative lymphoscintigraphy and SPECT/CT were used to define the location of the SLNs. SLNs were dissected using combination of radio- and fluorescence-guidance, followed by extended pelvic LN dissection and robot-assisted radical prostatectomy. Outcome measurements were number of tumor-bearing SNs, tumor-bearing LNs, removed nodes, number of patients with nodal metastases, and metastasis-free survival (MFS) of 4-7-year follow-up data.

RESULTS

IT-injection did not result in significant difference of removed SLNs (5.0 vs 6.0, p = 0.317) and histologically positive SLNs (28 vs 22, p = 0.571). However, in IT-group, the SLN-positive nodes were 73.7% of total positive nodes compared to 37.3% in IP-group (p = 0.015). Moreover, significantly more node-positive patients were found in IT-group (42% vs 24%, p = 0.045), which did not result in worse MFS. In two patients (3.6%) from whom the IT-tracer injection only partly covered intraprostatic tumor spread, nodal metastases in ePLND without tumor-positive SNs were yielded.

CONCLUSIONS

The percentage-positive SLNs found after IT-injection were significantly higher compared to IP-injection. Significantly more node-positive patients were found using IT-injection, which did not affect MFS. IT-injection failed to detect nodal metastases from non-index satellite lesions. Therefore, we suggest to combine IT- and IP-tracer injections in men with visible tumor on imaging.

Diagnostic Value, Oncologic Outcomes, and Safety Profile of Image-Guided Surgery Technologies During Robot-Assisted Lymph Node Dissection with Sentinel Node Biopsy for Prostate Cancer

Despite good sensitivity and a good negative predictive value, the implementation of sentinel node biopsy (SNB) in robot-assisted radical prostatectomy with extended pelvic lymph node dissection (ePLND) for prostate cancer is still controversial. For this reason, we aimed to define the added value of SNB (with different tracer modalities) to ePLND in the identification of nodal metastases. Complication rates and oncologic outcomes were also assessed. Methods: From January 2006 to December 2019, prospectively collected data were retrospectively analyzed from a single-institution database regarding prostate cancer patients treated with robot-assisted radical prostatectomy and ePLND with or without additional use of SNB, either with the hybrid tracer indocyanine green (ICG)-99mTc-nanocolloid or with free ICG. Multivariable logistic and Cox regression models tested the impact of adding SNB (either with the hybrid tracer or with free ICG) on lymph nodal invasion detection, complications, and oncologic outcomes. Results: Overall, 1,680 patients were included in the final analysis: 1,168 (69.5%) in the non-SNB group, 161 (9.6%) in the ICG-SNB group, and 351 (20.9%) in the hybrid-SNB group. The hybrid-SNB group (odds ratio, 1.61; 95%CI, 1.18-2.20; P = 0.002) was an independent predictor of nodal involvement, whereas the ICG-SNB group did not reach independent predictor status when compared with the non-SNB group (odds ratio, 1.35; 95%CI, 0.89-2.03; P = 0.1). SNB techniques were not associated with higher rates of complications. Lastly, use of hybrid SNB was associated with lower rates of biochemical recurrence (0.79; 95%CI, 0.63-0.98) and of clinical recurrence (hazard ratio, 0.76, P = 0.035) than were seen in the non-SNB group. Conclusion: The implementation of hybrid-SNB technique with ICG-99mTc-nanocolloid in prostate cancer improves detection of positive nodes and potentially lowers recurrence rates with subsequent optimization of patient management, without harming patient safety.

Rational Linker Design to Accelerate Excretion and Reduce Background Uptake of Peptidomimetic PSMA-Targeting Hybrid Molecules

The evolution of peptidomimetic hybrid molecules for preoperative imaging and guided surgery targeting the prostate-specific membrane antigen (PSMA) significantly progressed over the past few years, and some approaches are currently being evaluated for further clinical translation. However, accumulation in nonmalignant tissue such as kidney, bladder, spleen, or liver might limit tumor-to-background contrast for precise lesion delineation, particularly in a surgical setting. To overcome these limitations, a rational linker design aims at the development of a second generation of PSMA-11-based hybrid molecules with an enhanced pharmacokinetic profile and improved imaging contrast. Methods: A selection of rationally designed linkers was introduced to the PSMA-targeting hybrid molecule Glu-urea-Lys-HBED-CC-IRDye800CW, resulting in a second-generation peptidomimetic hybrid molecule library. The biologic properties were investigated in cell-based assays. In a preclinical proof-of-concept study with the radionuclide 68Ga, the impact of the modifications was evaluated by determination of specific tumor uptake, pharmacokinetics, and fluorescence imaging in tumor-bearing mice. Results: The modified hybrid molecules carrying various selected linkers revealed high PSMA-specific binding affinity and effective internalization. The highest tumor-to-background contrast of all modifications investigated was identified for the introduction of a histidine- (H) and glutamic acid (E)-containing linker ((HE)3-linker) between the PSMA-binding motif and the chelator. In comparison to the parental core structure, uptake in nonmalignant tissue was significantly reduced to a minimum, as exemplified by an 11-fold reduced spleen uptake from 38.12 ± 14.62 percentage injected dose (%ID)/g to 3.47 ± 1.39 %ID/g (1 h after injection). The specific tumor uptake of this compound (7.59 ± 0.95 %ID/g, 1 h after injection) was detected to be significantly higher than that of the parental tracer PSMA-11. These findings confirmed by PET and fluorescence imaging are accompanied by an enhanced pharmacokinetic profile with accelerated background clearance at early time points after injection. Conclusion: The novel generation of PSMA-targeting hybrid molecules reveals fast elimination, reduced background organ enrichment, and high PSMA-specific tumor uptake meeting the key demands for potent tracers in nuclear medicine and fluorescence-guided surgery. The approach's efficacy in improving the pharmacokinetic profile highlights the strengths of rational linker design as a powerful tool in strategic hybrid-molecule development.

A DROP-IN Gamma Probe for Robot-assisted Radioguided Surgery of Lymph Nodes During Radical Prostatectomy

BACKGROUND

The DROP-IN gamma probe was introduced to overcome the restricted manoeuvrability of traditional laparoscopic gamma probes. Through enhanced manoeuvrability and surgical autonomy, the DROP-IN promotes the implementation of radioguided surgery in the robotic setting.

OBJECTIVE

To confirm the utility and safety profile of the DROP-IN gamma probe and to perform a comparison with the traditional laparoscopic gamma probe and fluorescence guidance.

DESIGN, SETTING, AND PARTICIPANTS

Twenty-five prostate cancer patients were scheduled for a robot-assisted sentinel lymph node (SN) procedure, extended pelvic lymph node dissection, and prostatectomy at a single European centre.

SURGICAL PROCEDURE

After intraprostatic injection of indocyanine green (ICG)-^99mTc-nanocolloid (n = 12) or ^99mTc-nanocolloid + ICG (n = 13), SN locations were defined using preoperative imaging. Surgical excision of SNs was performed under image guidance using the DROP-IN gamma probe, the traditional laparoscopic gamma probe, and fluorescence imaging.

MEASUREMENTS

Intraoperative SN detection was assessed for the different modalities and related to anatomical locations. Patient follow-up was included (a median of 18 mo).

RESULTS AND LIMITATIONS

Overall, 47 SNs were pursued in vivo by the DROP-IN gamma probe, of which 100% were identified. No adverse events related to its use were observed. In vivo fluorescence imaging identified 91% of these SNs. The laparoscopic gamma probe identified only 76% of these SNs, where the detection inaccuracies appeared to be related to specific anatomical regions.

CONCLUSIONS

Owing to improved manoeuvrability, the DROP-IN probe yielded improved SN detection rates compared with the traditional gamma probe and fluorescence imaging. These findings underline that the DROP-IN technology provides a valuable tool for radioguided surgery in the robotic setting.

PATIENT SUMMARY

Radioguided robot-assisted surgery with the novel DROP-IN gamma probe is feasible and safe. It enables more efficient intraoperative identification of sentinel lymph nodes than can be achieved with a traditional laparoscopic gamma probe. The use of the DROP-IN probe in combination with fluorescence imaging allows for a complementary optical confirmation of node localisations.

Recent advances in nuclear and hybrid detection modalities for image-guided surgery

Introduction: Radioguided surgery is an ever-evolving part of nuclear medicine. In fact, this nuclear medicine sub-discipline actively bridges non-invasive molecular imaging with surgical care. Next to relying on the availability of radio- and bimodal-tracers, the success of radioguided surgery is for a large part dependent on the imaging modalities and imaging concepts available for the surgical setting. With this review, we have aimed to provide a comprehensive update of the most recent advances in the field. Areas covered: We have made an attempt to cover all aspects of radioguided surgery: 1) the use of radioisotopes that emit γ, β⁺, and/or β^- radiation, 2) hardware developments ranging from probes to 2D cameras and even the use of advanced 3D interventional imaging solutions, and 3) multiplexing solutions such as dual-isotope detection or combined radionuclear and optical detection. Expert opinion: Technical refinements in the field of radioguided surgery should continue to focus on supporting its implementation in the increasingly complex minimally invasive surgical setting, e.g. by accommodating robot-assisted laparoscopic surgery. In addition, hybrid concepts that integrate the use of radioisotopes with other image-guided surgery modalities such as fluorescence or ultrasound are likely to expand in the future.

Best practices in near-infrared fluorescence imaging with indocyanine green (NIRF/ICG)-guided robotic urologic surgery: a systematic review-based expert consensus

PURPOSE

The aim of the present study is to investigate the impact of the near-infrared (NIRF) technology with indocyanine green (ICG) in robotic urologic surgery by performing a systematic literature review and to provide evidence-based expert recommendations on best practices in this field.

METHODS

All English language publications on NIRF/ICG-guided robotic urologic procedures were evaluated. We followed the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) statement to evaluate PubMed^®, Scopus^® and Web of Science™ databases (up to April 2019). Experts in the field provided detailed pictures and intraoperative video-clips of different NIRF/ICG-guided robotic surgeries with recommendations for each procedure. A unique QRcode was generated and linked to each underlying video-clip. This new exclusive feature makes the present the first "dynamic paper" that merges text and figure description with their own video providing readers an innovative, immersive, high-quality and user-friendly experience.

RESULTS

Our electronic search identified a total of 576 papers. Of these, 36 studies included in the present systematic review reporting the use of NIRF/ICG in robotic partial nephrectomy (n = 13), robotic radical prostatectomy and lymphadenectomy (n = 7), robotic ureteral re-implantation and reconstruction (n = 5), robotic adrenalectomy (n = 4), robotic radical cystectomy (n = 3), penectomy and robotic inguinal lymphadenectomy (n = 2), robotic simple prostatectomy (n = 1), robotic kidney transplantation (n = 1) and robotic sacrocolpopexy (n = 1).

CONCLUSION

NIRF/ICG technology has now emerged as a safe, feasible and useful tool that may facilitate urologic robotic surgery. It has been shown to improve the identification of key anatomical landmarks and pathological structures for oncological and non-oncological procedures. Level of evidence is predominantly low. Larger series with longer follow-up are needed, especially in assessing the quality of the nodal dissection and the feasibility of the identification of sentinel nodes and the impact of these novel technologies on long-term oncological and functional outcomes.

Three-Dimensional Tumor Margin Demarcation Using the Hybrid Tracer Indocyanine Green-99mTc-Nanocolloid: A Proof-of-Concept Study in Tongue Cancer Patients Scheduled for Sentinel Node Biopsy

For radical resection of squamous cell carcinoma of the oral cavity, a tumor-free margin of at least 5 mm is required. Unfortunately, establishing in-depth margins is a surgical conundrum. Knowing that the hybrid sentinel node (SN) tracer indocyanine green (ICG)-^99mTc-nanocolloid generates temporary tattoolike markings at the site of administration, we studied the ability to apply this tracer for tumor margin demarcation combined with SN biopsy. Methods: Nineteen patients with clinical T1-T2 oral tongue tumors received the traditional superficial 3 or 4 deposits of ICG-^99mTc-nanocolloid (0.1 mL each), and in 12 patients additional deposits were placed deeply using ultrasound guidance (total of 6; 0.07 mL each). SN mapping was performed using lymphoscintigraphy and SPECT/CT. Before and directly after tumor excision, fluorescence imaging was performed to monitor the tracer deposits in the patient (fluorescent deposits were not used to guide the surgical excision). At pathologic examination, primary tumor samples were studied in detail. Results: The number of tracer depositions did not induce a significant difference in the number of SNs visualized (P = 0.836). Reproducible and deep tracer deposition proved to be challenging. The fluorescent nature of ICG-^99mTc-nanocolloid supported in vivo and ex vivo identification of the tracer deposits surrounding the tumor. Pathologic examination indicated that in 66.7% (8/12), all fluorescence was observed within the resection margins. Conclusion: This study indicates that tumor margin demarcation combined with SN identification has potential but that some practical challenges need to be overcome if this technique is to mature as a surgical guidance concept. Future studies need to define whether the technology can improve the radical nature of the resections.

Synthesis and Preclinical Characterization of the PSMA-Targeted Hybrid Tracer PSMA-I&F for Nuclear and Fluorescence Imaging of Prostate Cancer

The prostate-specific membrane antigen (PSMA)–targeted radiotracers ⁶⁸Ga/¹⁷⁷Lu-PSMA-I&T and ^99mTc-PSMA-I&S (for imaging and surgery) are currently successfully used for clinical PET imaging, radionuclide therapy, and radioguided surgery of metastatic prostate cancer. To additionally exploit the high sensitivity and spatial resolution of fluorescence imaging for improved surgical guidance, a PSMA-I&T–based hybrid tracer, PSMA-I&F (DOTAGA-k(Sulfo-Cy5)-y-nal-k-Sub-KuE), has been developed and evaluated. Methods: The in vitro PSMA-targeting efficiency of PSMA-I&F, the reference PSMA-I&T, and their corresponding ^natGa-/⁶⁸Ga- and ^natLu/¹⁷⁷Lu counterparts was determined in LNCaP cells via competitive binding assays (IC₅₀) and dual-tracer radioligand and fluorescence internalization studies. Biodistribution and small-animal PET imaging studies were performed in CB17 SCID and LNCaP xenograft–bearing SHO mice, respectively, and complemented by intraoperative far-red fluorescence imaging using a clinical laparoscope. Additionally, fully automated serial cryosectioning and fluorescence imaging of 1 tumor-bearing animal as well as PSMA immunohistochemistry and fluorescence microscopy of organ cryosections (tumor, kidney, spleen) were also performed. Results: Compared with the parent PSMA-I&T analogs, the PSMA affinities of PSMA-I&F and its ^natGa-/^natLu-complexes remained high and unaffected by dye conjugation (7.9 < IC₅₀ < 10.5 nM for all ligands). The same was observed for the internalization of ⁶⁸Ga- and ¹⁷⁷Lu-PSMA-I&F. In vivo, blood clearance of ⁶⁸Ga- and ¹⁷⁷Lu-PSMA-I&F was only slightly delayed by high plasma protein binding (94%–95%), and very low accumulation in nontarget organs was observed already at 1 h after injection. Dynamic PET imaging confirmed PSMA-specific (as demonstrated by coinjection of 2-PMPA) uptake into the LNCaP xenograft (4.5% ± 1.8 percentage injected dose per gram) and the kidneys (106% ± 23 percentage injected dose per gram). Tumor-to-background ratios of 2.1, 5.2, 9.6, and 9.6 for blood, liver, intestines, and muscle, respectively, at 1 h after injection led to excellent imaging contrast in ⁶⁸Ga-PSMA-I&F PET and in intraoperative fluorescence imaging. Furthermore, fluorescence imaging of tissue cryosections allowed high-resolution visualization of intraorgan PSMA-I&F distribution in vivo and its correlation with PSMA expression as determined by immunohistochemistry. Conclusion: Thus, with its high PSMA-targeting efficiency and favorable pharmacokinetic profile, ⁶⁸Ga/¹⁷⁷Lu-PSMA-I&F serves as an excellent proof-of-concept compound for the general feasibility of PSMA-I&T–based hybrid imaging. The PSMA-I&T scaffold represents a versatile PSMA-targeted lead structure, allowing relatively straightforward adaptation to the different structural requirements of dedicated nuclear or hybrid imaging agents.

Robot-assisted laparoscopic surgery using DROP-IN radioguidance: first-in-human translation

Purpose

Radioguided surgery has been widely used for clinical procedures such as sentinel node resections. In the (robot-assisted) laparoscopic setting radioguidance is realized using laparoscopic gamma probes, which have limited maneuverability. To increase the rotational freedom, a tethered DROP-IN gamma probe was designed. Here we present the first in vivo feasibility study of this technology in prostate cancer patients.

Methods

Ten patients scheduled for a sentinel node procedure received four injections into the prostate with (indocyanine green-)^99mTechnetium-nanocolloid and underwent preoperative imaging (lymphoscintigraphy and SPECT/CT). The DROP-IN probe was inserted via the assistant port, still permitting the insertion and usage of additional laparoscopic tools.

Results

The sentinel nodes were resected using the da Vinci® Si robot under guidance of DROP-IN gamma tracing and fluorescence imaging. The surgeon was able to independently maneuver the DROP-IN probe using the ProGrasp® forceps of the da Vinci® robot and distinguish sentinel nodes from background signal (such as the injection site).

Conclusions

Overall the DROP-IN design proves to be a valuable tool for robot-assisted radioguided surgery approaches.

A practical guide for the use of indocyanine green and methylene blue in fluorescence-guided abdominal surgery

Near-infrared (NIR) fluorescence imaging is gaining clinical acceptance over the last years and has been used for detection of lymph nodes, several tumor types, vital structures and tissue perfusion. This review focuses on NIR fluorescence imaging with indocyanine green and methylene blue for different clinical applications in abdominal surgery with an emphasis on oncology, based on a systematic literature search. Furthermore, practical information on doses, injection times, and intraoperative use are provided.

Fluorescence-supported lymphography and extended pelvic lymph node dissection in robot-assisted radical prostatectomy: a prospective, randomized trial

PURPOSE

To demonstrate the benefits of fluorescence-supported extended pelvic lymph node dissection (ePLND) compared to regular ePLND in robot-assisted radical prostatectomy.

METHODS

120 patients with intermediate- or high-risk prostate cancer were prospectively randomized (1:1): in the intervention group, indocyanine green (ICG) was injected transrectally into the prostate before docking of the robot. In both groups, ePLND was performed including additional dissection of fluorescent lymph nodes (LN) in the ICG group.

RESULTS

After drop-out of two patients, 59 patients were allocated to the control (A) and intervention group (B) with a median PSA of 8,6 ng/ml. Median console time was 159 (A) vs. 168 (B) min (p = 0.20) with a longer time for ICG-ePLND: 43 (A) vs. 55 min (B) (p = 0.001). 2609 LN were found with significantly more LN after ICG-supported ePLND with a median of 25 vs. 17 LN in A (p < 0.001). Nodal metastases were detected in 6 patients in A (25 cancerous LN) vs. 9 patients in B (62 positive LN) (p = 0.40). In seven of nine patients, ICG-ePLND identified at least one cancer-positive LN (sensitivity 78%), 27 of 62 cancerous LN were fluorescent. Symptomatic lymphocele occurred in one patient in a and in three patients in b (p = 0.62). After a median follow-up of 22.9 months, PSA levels were similar.

CONCLUSIONS

While ICG-ePLND seems to be beneficial for a better understanding of the lymphatic drainage and a more meticulous diagnostic approach, the sensitivity is not sufficient to recommend stand-alone ICG lymph node dissection.

Updated Nomogram Incorporating Percentage of Positive Cores to Predict Probability of Lymph Node Invasion in Prostate Cancer Patients Undergoing Sentinel Lymph Node Dissection

Objectives: To update the first sentinel nomogram predicting the presence of lymph node invasion (LNI) in prostate cancer patients undergoing sentinel lymph node dissection (sPLND), taking into account the percentage of positive cores. Patients and Methods: Analysis included 1,870 prostate cancer patients who underwent radioisotope-guided sPLND and retropubic radical prostatectomy. Prostate-specific antigen (PSA), clinical T category, primary and secondary biopsy Gleason grade, and percentage of positive cores were included in univariate and multivariate logistic regression models predicting LNI, and constituted the basis for the regression coefficient-based nomogram. Bootstrapping was applied to generate 95% confidence intervals for predicted probabilities. The area under the receiver operator characteristic curve (AUC) was obtained to quantify accuracy. Results: Median PSA was 7.68 ng/ml (interquartile range (IQR) 5.5-12.3). The number of lymph nodes removed was 10 (IQR 7-13). Overall, 352 patients (18.8%) had LNI. All preoperative prostate cancer characteristics differed significantly between LNI-positive and LNI-negative patients (P<0.001). In univariate accuracy analyses, the proportion of positive cores was the foremost predictor of LNI (AUC, 77%) followed by PSA (71.1%), clinical T category (69.9%), and primary and secondary Gleason grade (66.6% and 61.3%, respectively). For multivariate logistic regression models, all parameters were independent predictors of LNI (P<0.001). The nomogram exhibited a high predictive accuracy (AUC, 83.5%). Conclusion: The first update of the only available sentinel nomogram predicting LNI in prostate cancer patients demonstrates even better predictive accuracy and improved calibration. As an additional factor, the percentage of positive cores represents the leading predictor of LNI. This updated sentinel model should be externally validated and compared with results of extended PLND-based nomograms.

Intraoperative near-infrared fluorescent imaging during robotic operations

The intraoperative identification of certain anatomical structures because they are small or visually occult may be challenging. The development of minimally invasive surgery brought additional difficulties to identify these structures due to the lack of complete tactile sensitivity. A number of different forms of intraoperative mapping have been tried. Recently, the near-infrared fluorescence imaging technology with indocyanine green has been added to robotic platforms. In addition, this technology has been tested in several types of operations, and has advantages such as safety, low cost and good results. Disadvantages are linked to contrast distribution in certain clinical scenarios. The intraoperative near-infrared fluorescent imaging is new and promising addition to robotic surgery. Several reports show the utility of this technology in several different procedures. The ideal dose, time and site for dye injection are not well defined. No high quality evidence-based comparative studies and long-term follow-up outcomes have been published so far. Initial results, however, are good and safe. RESUMO A identificação intraoperatória de certas estruturas anatômicas, por seu tamanho ou por elas serem ocultas à visão, pode ser desafiadora. O desenvolvimento da cirurgia minimamente invasiva trouxe dificuldades adicionais, pela falta da sensibilidade tátil completa. Diversas formas de detecção intraoperatória destas estruturas têm sido tentadas. Recentemente, a tecnologia de fluorescência infravermelha com verde de indocianina foi associada às plataformas robóticas. Além disso, essa tecnologia tem sido testada em uma variedade de cirurgias, e suas vantagens parecem estar ligadas a baixo custo, segurança e bons resultados. As desvantagens estão associadas à má distribuição do contraste em determinados cenários. A imagem intraoperatória por fluorescência infravermelha é uma nova e promissora adição à cirurgia robótica. Diversas séries mostram a utilidade da tecnologia em diferentes procedimentos. Dose ideal, local e tempo da injeção do corante ainda não estão bem estabelecidos. Estudos comparativos de alta qualidade epidemiológica baseados em evidência ainda não estão disponíveis. No entanto, os resultados iniciais são bons e seguros.

Role of ICG-99mTc-nanocolloid for sentinel lymph node detection in cervical cancer: a pilot study

PURPOSE

Sentinel lymph node biopsy (SLNB) can be used for nodal staging in early cervical cancer. For this purpose, the tracers most commonly used are radiotracers based on technetium. For the last decade, indocyanine green (ICG) has been used as a tracer for SLNB in other malignancies with excellent results and, more recently, a combination of ICG and a radiotracer has been shown to have the advantages of both tracers. The aim of this study was to evaluate the role of ICG-^99mTc-nanocolloid in SLN detection in patients with cervical cancer.

METHODS

This prospective study included 16 patients with cervical cancer. The hybrid tracer was injected the day (19-21 h) before surgery for planar and SPECT/CT lymphoscintigraphy. Blue dye was administered periorificially in 14 patients. SLNs were removed according to their distribution on lymphoscintigraphy and when radioactive, fluorescent and/or stained with blue dye. Nodal specimens were pathologically analysed for metastases including by immunochemistry.

RESULTS

Lymphoscintigraphy and SPECT/CT showed drainage in all patients. A total of 69 SLNs were removed, of which 66 were detected by their radioactivity signal and 67 by their fluorescence signal. Blue dye identified only 35 SLNs in 12 of the 14 patients (85.7%). All patients showed bilateral pelvic drainage. Micrometastases were diagnosed in two patients, and were the only lymphatic nodes involved.

CONCLUSIONS

SLNB with ICG-^99mTc-nanocolloid is feasible and safe in patients with early cervical cancer. This hybrid tracer provided bilateral SLN detection in all patients and a higher detection rate than blue dye, so it could become an alternative to the combined technique.

Beyond the Briganti nomogram: Individualisation of lymphadenectomy using selective sentinel node biopsy during radical prostatectomy for prostate cancer

OBJECTIVE

To validate the technique of selective sentinel node biopsy for diagnosing and staging intermediate to high-risk prostate cancer by comparing the technique with conventional extended lymphadenectomy (eLFD) in a prospective, longitudinal comparative study.

METHODS

We applied the technique to 45 patients. After an intraprostatic injection of ^99mTc-nanocolloid and preoperative single-photon emission computed tomography (SPECT/CT), we extracted the sentinel lymph nodes, guided by a portable Sentinella® gamma camera and a laparoscopic gamma-ray detection probe. The eLFD was completed to establish the negative predictive value of the technique.

RESULTS

SPECT/CT showed radiotracer deposits outside the eLFD territory in 73% of the patients and the laparoscopic gamma probe in 60%. The mean number of active foci per patient was 4.3 in the SPECT/CT and 3.2 in the laparoscopic gamma probe. The mean number of extracted sentinel lymph nodes was 4.3 (0-14), with 26% outside the eLFD territory. The lymph nodes were metastatic in 10 patients (22%), 6/40 (15%) when the prostatectomy was the primary treatment. In all cases with metastatic lymph nodes, there was at least one positive sentinel node. Metastatic sentinel lymph nodes were found outside the eLFD territory in 3/10 patients (30%). The sensitivity was 100%, the specificity was 94.73%, the positive predictive value was 81.81%, and the negative predictive value was 100%.

CONCLUSION

Selective sentinel node biopsy is superior to eLFD for diagnosing lymph node involvement and can avoid eLFD when metastatic sentinel lymph nodes are not found (85%), with the consequent functional advantages.

Sentinel Lymph Node Biopsy in Cutaneous Melanoma: Standard and New Technical Procedures and Clinical Advances. A Systematic Review of the Literature

Melanoma is an important public health problem, and its incidence is increasing worldwide. The disease status of regional lymph nodes is the most important prognostic factor in early-stage melanoma patients. Sentinel lymph node biopsy (SLNB) was introduced in the early 1990s as a less invasive procedure than complete lymph node dissection to allow histopathologic evaluation of the "sentinel lymph node" (SLN), which is the first node along the lymphatic pathway from a primary tumor. Sentinel lymph node biopsy has minimal complication risks compared with standard complete lymph node dissection. Currently, SLNB is the accepted method for staging patients with clinically node-negative cutaneous melanoma and provides the most powerful prognostic information by evaluating the nodal basin status. The current practice of SLNB consists of the injection of Tc-labeled radiopharmaceutical, preoperative lymphoscintigraphy with the possibility of using the SPECT/CT hybrid imaging, and intraoperative SLN localization using a handheld gamma probe with or without the use of blue dye. Recently, the SLN localization and detection have been enhanced with the use of new tracers and new intraoperative devices, which have demonstrated to be particularly useful in melanomas of the head and neck region and in area of complex anatomy. Despite these important advances in the technology and the increasing experience in SLN mapping, major research centers have reported a false-negative rate higher than 15%. This relatively high false-negative rate, greater than those reported in the initial validation studies, points out the importance for the nuclear medicine community to continuously improve their knowledge on the biological behavior of melanoma and to improve the technical aspects that may allow more precise staging. For the SLNB procedure to be accurate, it is of critical importance that all "true" SLNs are identified and removed for examination. The aim of this article is to provide general information about the SLNB procedure in clinical practice highlighting the importance of standardization and accuracy of SLN identification in the light of the most recent technical innovations.

Radioguided surgery and the GOSTT concept: From pre-operative image and intraoperative navigation to image-assisted excision

Radio-guided surgery has been developed for application in those disease scheduled for surgical management, particularly in areas of complex anatomy. This is based on the use of pre-operative scintigraphic planar, tomographic and fused SPECT/CT images, and the possibility of 3D reconstruction for the subsequent intraoperative locating of active lesions using handheld devices (detection probes, gamma cameras, etc.). New tracers and technologies have also been incorporated into these surgical procedures. The combination of visual and acoustic signals during the intraoperative procedure has become possible with new portable imaging modalities. In daily practice, the images offered by these techniques and devices combine perioperative nuclear medicine imaging with the superior resolution of additional optical guidance in the operating room. In many ways they provide real-time images, allowing accurate guidance during surgery, a reduction in the time required for tissue location and an anatomical environment for surgical recognition. All these approaches have been included in the concept known as (radio) Guided intraOperative Scintigraphic Tumour Targeting (GOSTT). This article offers a general view of different nuclear medicine and allied technologies used for several GOSTT procedures, and illustrates the crossing of technological frontiers in radio-guided surgery.

Sentinel lymph node detection during radical prostatectomy for prostate cancer: current evidence and results of our experience

PURPOSE

A sentinel lymph node (SNL) is the primary landing zone of cancer cells that spreads through the lymphatic vessels. The rational of the detection of sentinel node (SLN) during radical prostatectomy (RP) for prostate cancer (PCa) is the removal of the first nodal stations to provide a restriction of the template of node dissection. A review of the outcomes of SNL detection during RP for PCa was performed.

MATERIALS AND METHODS

A systematic review of the literature was conducted, searching on PubMed and Web of Science, using the following keywords: lymph node dissection, prostatic neoplasm, sentinel node.

RESULTS

Twenty articles were selected and analyzed including over 2000 PCa patients. Although promising and technically feasible, many points remain to be clarified before clinical application can be recommended.

CONCLUSIONS

The technique of SNL detection is feasible and provides a higher sensitivity and detection rate than standard lymphadenectomy, especially for organ-confined tumors. Larger series and long-term follow-up data are mandatory to assess the oncologic effectiveness of the detection of SNL for PCa.

Highlights lecture EANM 2015: the search for nuclear medicine's superheroes

The EANM 2015 Annual Congress, held from October 10th to 14th in Hamburg, Germany, was outstanding in many respects. With 5550 participants, this was by far the largest European congress concerning nuclear medicine. More than 1750 scientific presentations were submitted, with more than 250 abstracts from young scientists, indicating that the future success of our discipline is fuelled by a high number of young individuals becoming involved in a multitude of scientific activities. Significant improvements have been made in molecular imaging of cancer, particularly in prostate cancer. PSMA-directed PET/CT appears to become a new gold standard for staging and restaging purposes. Novel tumour specific compounds have shown their potential for target identification also in other solid neoplasms and further our understanding of tumour biology and heterogeneity. In addition, a variety of nuclear imaging techniques guiding surgical interventions have been introduced. A particular focus of the congress was put on targeted, radionuclide based therapies. Novel theranostic concepts addressing also tumour entities with high incidence rates such as prostate cancer, melanoma, and lymphoma, have shown effective anti-tumour activity. Strategies have been presented to improve further already established therapeutic regimens such as somatostatin receptor based radio receptor therapy for treating advanced neuroendocrine tumours. Significant contributions were presented also in the neurosciences track. An increasing number of target structures of high interest in neurology and psychiatry are now available for PET and SPECT imaging, facilitating specific imaging of different subtypes of dementia and movement disorders as well as neuroinflammation. Major contributions in the cardiovascular track focused on further optimization of cardiac perfusion imaging by reducing radiation exposure, reducing scanning time, and improving motion correction. Besides coronary artery disease, many contributions focused on cardiac inflammation, cardiac sarcoidosis, and specific imaging of large vessel vasculitis. The physics and instrumentation track included many highlights such as novel, high resolution scanners. The most noteworthy news and developments of this meeting were summarized in the highlights lecture. Only 55 scientific contributions were mentioned, and hence they represent only a brief summary, which is outlined in this article. For a more detailed view, all presentations can be accessed by the online version of the European Journal of Nuclear Medicine and Molecular Imaging (Volume 42, Supplement 1).

Navigation of a robot-integrated fluorescence laparoscope in preoperative SPECT/CT and intraoperative freehand SPECT imaging data: a phantom study

Robot-assisted laparoscopic surgery is becoming an established technique for prostatectomy and is increasingly being explored for other types of cancer. Linking intraoperative imaging techniques, such as fluorescence guidance, with the three-dimensional insights provided by preoperative imaging remains a challenge. Navigation technologies may provide a solution, especially when directly linked to both the robotic setup and the fluorescence laparoscope. We evaluated the feasibility of such a setup. Preoperative single-photon emission computed tomography/X-ray computed tomography (SPECT/CT) or intraoperative freehand SPECT (fhSPECT) scans were used to navigate an optically tracked robot-integrated fluorescence laparoscope via an augmented reality overlay in the laparoscopic video feed. The navigation accuracy was evaluated in soft tissue phantoms, followed by studies in a human-like torso phantom. Navigation accuracies found for SPECT/CT-based navigation were 2.25 mm (coronal) and 2.08 mm (sagittal). For fhSPECT-based navigation, these were 1.92 mm (coronal) and 2.83 mm (sagittal). All errors remained below the <1-cm detection limit for fluorescence imaging, allowing refinement of the navigation process using fluorescence findings. The phantom experiments performed suggest that SPECT-based navigation of the robot-integrated fluorescence laparoscope is feasible and may aid fluorescence-guided surgery procedures.

The sentinel node approach in gynaecological malignancies

This review discusses the state-of-the-art of sentinel lymph node mapping in gynaecological malignancies, including cervical cancer, endometrial cancer, and vulvar cancer, with an emphasis on new technological advances. For this objective, PubMed/MEDLINE was searched for relevant studies about the sentinel lymph node procedure in gynaecology. In particular, the use of preoperative lymphatic mapping with lymphoscintigraphy and single photon emission tomography/computed tomography (SPECT/CT) was identified in 18 studies. Other recent advances as hybrid tracers (e.g. ICG-^99mTc-nanocolloid) and intraoperative tools (portable γ-camera and 3D navigation devices) appear to also represent a useful guide for the surgeon during the operation. Concerning vulvar and cervical cancers, the sentinel lymph node procedure has been incorporated to the current guidelines in Europe and North America, whereas for endometrial cancer it is considered investigative.