R.A. Valdés-Olmos

Image navigation as a means to expand the boundaries of fluorescence-guided surgery

Hybrid tracers that are both radioactive and fluorescent help extend the use of fluorescence-guided surgery to deeper structures. Such hybrid tracers facilitate preoperative surgical planning using (3D) scintigraphic images and enable synchronous intraoperative radio- and fluorescence guidance. Nevertheless, we previously found that improved orientation during laparoscopic surgery remains desirable. Here we illustrate how intraoperative navigation based on optical tracking of a fluorescence endoscope may help further improve the accuracy of hybrid surgical guidance. After feeding SPECT/CT images with an optical fiducial as a reference target to the navigation system, optical tracking could be used to position the tip of the fluorescence endoscope relative to the preoperative 3D imaging data. This hybrid navigation approach allowed us to accurately identify marker seeds in a phantom setup. The multispectral nature of the fluorescence endoscope enabled stepwise visualization of the two clinically approved fluorescent dyes, fluorescein and indocyanine green. In addition, the approach was used to navigate toward the prostate in a patient undergoing robot-assisted prostatectomy. Navigation of the tracked fluorescence endoscope toward the target identified on SPECT/CT resulted in real-time gradual visualization of the fluorescent signal in the prostate, thus providing an intraoperative confirmation of the navigation accuracy.

Valoración del ganglio centinela combinando SPECT/TAC con la imagen planar y su importancia para el acto quirúrgico

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.

Sentinel Lymph Node Biopsy for Prostate Cancer: A Hybrid Approach

To provide surgeons with optimal guidance during interventions, it is crucial that the molecular imaging data generated in the diagnostic departments finds its way to the operating room. Sentinel lymph node (SLN) biopsy provides a textbook example in which molecular imaging data acquired in the department of nuclear medicine guides the surgical management of patients. For prostate cancer, in which SLNs are generally located deep in the pelvis, procedures are preferably performed via a (robot-assisted) laparoscopic approach. Unfortunately, in the laparoscopic setting the senses of the surgeon are reduced. This topical review discusses technologic innovations that can help improve surgical guidance during SLN biopsy procedures.

Colaboración especialValoración del ganglio centinela combinando SPECT/TAC con la imagen planar y su importancia para el acto quirúrgicoEvaluation 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.

Results of a Prospective Multicenter International Atomic Energy Agency Sentinel Node Trial on the Value of SPECT/CT Over Planar Imaging in Various Malignancies

We aimed to assess the additional value of SPECT/CT over planar lymphoscintigraphy (PI) in sentinel node (SN) detection in malignancies with different lymphatic drainage such as breast cancer, melanoma, and pelvic tumors. Methods: From 2010 to 2013, 1,508 patients were recruited in a multicenter study: 1,182 breast cancer, 262 melanoma, and 64 pelvic malignancies (prostate, cervix, penis, vulva). PI was followed by SPECT/CT 1–3 h after injection of 99mTc-colloid particles. Surgery was performed the same or next day. Results: Significantly more SNs were detected by SPECT/CT for breast cancer (2,165 vs. 1,892), melanoma (602 vs. 532), and pelvic cancer (195 vs. 138), all P < 0.001. The drainage basin mismatch between PI and SPECT/CT was 16.5% for breast cancer, 11.1% for melanoma, and 51.6% for pelvic cancers. Surgical adjustment was 17% for breast cancer, 37% for melanoma, and 65.6% for pelvic cancer. Conclusion: SPECT/CT detected more SNs and changed the drainage territory, leading to surgical adjustments in a considerable number of patients in all malignancies studied but especially in the pelvic cancer group because of this groups deep lymphatic drainage. We recommend SPECT/CT in all breast cancer patients with no SN visualized on PI, all patients with melanoma of the head and neck or trunk, all patients with pelvic malignancies, and those breast cancer and melanoma patients with unexpected drainage on PI.

Added value of prone position technique for PET-TAC in breast cancer patients

Abstract Aim This study has aimed to assess if the prone position shows significant differences in regards to the supine position in PET/CT studies in breast cancer patients and to determine which modality offers better evaluation of the images. Method A total of 30 patients were included from October 2009 to February 2010 prior to beginning neoadjuvant chemotherapy. An intravenous 18 F-FDG dose ranging from 180 to 240 MBq was administered. Image acquisition was begun 60±10 min after injection. First of all, a thorax scan was performed with the patient in prone position, followed by a whole body study with the patient in supine position. Results Uptake in tumor lesions was observed in all of the patients. Twenty-four patients (80%) had the same number of lesions with both techniques. Five patients (17%) had a different amount of axillary lymph nodes. One patient (3.3%) had a different number of lesions. The prone position lesions had a mean SUVmax 8.89±4.18 compared to 7.67±4.34 in supine position. The areas of the primary breast lesions were higher in the prone position (8.59±7.80 compared with 7.81±7.39). Mean SUVmax of axillary nodes was 5.97±4.02 in prone and 4.41±3.10 in supine. Conclusion The hanging breast technique can achieve higher lesion visualization as well as higher semiquantitative values in comparison with standard procedure. This supports its inclusion in acquisition guidelines of PET/CT imaging in breast cancer patients.

An innovative multimodality approach for sentinel node mapping and biopsy in head and neck malignancies

PURPOSE Recent innovations such as preoperative SPECT/CT, intraoperative imaging using portable devices and a hybrid tracer were evaluated in a multimodality approach for sentinel node (SN) mapping and biopsy in head and neck malignancies. MATERIAL AND METHODS The evaluation included 25 consecutive patients with head and neck malignancies (16 melanomas and 9 oral cavity squamous cell carcinomas). Patients were peritumorally injected with the hybrid tracer ICG-(99m)Tc-nanocolloid. SNs were initially identified with lymphoscintigraphy followed by single photon emission computed tomography (SPECT/CT) 2 hours after tracer administration. During surgery a portable gamma camera in combination with a near-infrared fluorescence camera was used in addition to a handheld gamma ray detection probe to locate the SNs. RESULTS In all patients the use of conventional lymphoscintigraphy, SPECT/CT and the additional help of the portable gamma camera in one case were able to depict a total of 67 SNs (55 of them visualized on planar images, 11 additional on SPECT/CT and 1 additional with the portable gamma camera). A total of 67 of the preoperatively defined SNs together with 22 additional SNs were removed intraoperatively; 12 out of the 22 additional SNs found during operation were located in the vicinity of the injection site in anatomical areas such as the periauricular or submental regions. The other 10 additional SNs were found by radioguided post-resection control of the excision SN site. CONCLUSION In the present series 26% additional SNs were found using the multimodal approach, that incorporates SPECT/CT and intraoperative imaging to the conventional procedure. This approach appears to be useful in malignancies located close to the area of lymphatic drainage such as the periauricular area and the oral cavity.

Lymphatic Drainage in Prostate Carcinoma assessed by Lymphoscintigraphy and SPECT/CT: Its importance for the Sentinel Node Procedure

PURPOSE The goal was to evaluate the sentinel node procedure in relation to different pathways of lymphatic drainage and the areas of pelvic lymphadenectomy in patients with prostate cancer assessed by lymphoscintigraphy and SPECT/CT study. METHODS Eighteen patients with prostate cancer of intermediate prognosis were injected with 240 MBq of (99m)Tc-nanocolloid in the peripheral zone of each quadrant of the prostate, guided by transrectal ultrasonography. Tracer administration was also controlled with a portable gamma camera to assure that there was no diffusion outside the prostate. The injection was followed by planar imaging at 15 min. and 2 h, performing a SPECT/CT study at 2 h. with 2 mm slices. On the same day, a laparoscopic sentinel node lymphadenectomy assisted by a gamma probe and a portable gamma camera was performed. RESULTS A total of 55 sentinel lymph nodes (SLNs) were visualized. In 17/18 of patients (94%) SLNs were observed outside the obturator region. Twenty SLNs (36%) were observed along the external iliac artery, 14 in the obturator fossa (25.4%), 6 in internal iliac area (11%) and 4 in common iliac region (7.2%). Three SLNs were visualized in presacral (5.4%), paraaortic (5.4%), and pararectal areas (5.4%) and two in paravesical region (3.6%). SLN metastases were found in 6 patients (33%), and in one of them, a SLN located along the common iliac artery, was the only one with metastases. CONCLUSION Lymphatic drainage from the prostate has high individual variability, and direct drainage outside the pelvic area is observed frequently. With the SLN procedure, SLNs outside the routine area of lymphadenectomy can also be sampled to stage the patient more accurately.

Decisive role of SPECT/CT in localization of unusual periscapular sentinel nodes in patients with posterior trunk melanoma: three illustrative cases and a review of the literature.

Sentinel node mapping is widely applied in patients with melanoma. Although this type of skin cancer usually drains to the standard regional nodal basins, some patients have drainage to an unpredicted site. Nodes lying along a lymphatic channel, between the primary melanoma site and a common basin, are often called interval, in-transit, ectopic, intercalated, or aberrant nodes. They must be considered sentinel lymph nodes because they receive direct lymphatic drainage from a primary tumor site. Most investigators agree that interval sentinel nodes should be harvested; however, the management of melanoma patients with an involved interval sentinel node without established metastasis in the regional basin downstream is controversial. New and innovating technologies have improved nuclear medicine images, including single-photon emission computed tomography/computed tomography (SPECT/CT), a multimodal technique that fuses the radioactivity distribution detected by SPECT with the anatomic information harvested by CT. SPECT/CT does not replace the conventional planar images; it should be considered as a complementary modality for the search of sentinel lymph nodes. We report three illustrative cases that underline the decisive role of SPECT/CT with two-dimensional and three-dimensional reconstruction images to localize the uncommon periscapular sentinel nodes in patients with melanoma of the posterior trunk. The use of this image fusion technique on these patients leads to improved preoperative visualization of the sentinel nodes, may help identify additional periscapular interval sentinel nodes, and enables precise localization of the nodes with their surrounding anatomic structures. The cases are discussed together with a review of the literature.

Multimodal imaging in radioguided surgery

Radioguided surgery (RGS) utilizes radiolabeled tracers that accumulate in the lesion of interest following local or systemic administration. RGS is an expanding surgical guidance technology, but unfortunately most currently available radiotracers are unable to provide intraoperative optical information regarding the location of the lesion. In 2011, a new hybrid tracer (both radioactive and fluorescent) was introduced for sentinel lymph node detection. This hybrid tracer (indocyanine green-99mTc-nanocolloid) has helped to generate a new hybrid surgical guidance concept, thereby expanding the traditional RGS-based approach. Based on its radioactive signature a hybrid tracer is able to preserve the “traditional” role for RGS. Furthermore, as an additional tool in the operating room, a hybrid tracer provides optical information via fluorescence guidance. This review discusses the most common RGS approaches. Different clinically used radioactive tracers and their potential hybrid derivatives are also discussed. Furthermore, the various imaging devices designed for radioactivity-based detection are reviewed in the context of generating hybrid-imaging modalities.