Lymphoscintigraphic sentinel node identification in patients with breast cancer: the role of SPECT-CT

Tumor Contact With Internal Mammary Perforator Vessels as Risk Factor for Gross Internal Mammary Lymph Node Involvement in Patients With Breast Cancer

PURPOSE

The identification of internal mammary lymph node metastases and the assessment of associated risk factors are crucial for adjuvant regional lymph node irradiation in patients with breast cancer. The current study aims to investigate whether tumor contact with internal mammary perforator vessels is associated with gross internal mammary lymph node involvement.

METHODS AND MATERIALS

We included 297 patients with primary breast cancer and gross internal mammary (IMN+) and/or axillary metastases as well as 230 patients without lymph node metastases. Based on pretreatment dynamic contrast-enhanced magnetic resonance imaging, we assessed contact of the tumor with the internal mammary perforating vessels (IMPV).

RESULTS

A total of 59 patients had ipsilateral IMN+ (iIMN+), 10 patients had contralateral IMN+ (cIMN+), and 228 patients had ipsilateral axillary metastases without IMN; 230 patients had node-negative breast cancer. In patients with iIMN+, 100% of tumors had contact with ipsilateral IMPV, with 94.9% (n = 56) classified as major contact. In iIMN- patients, major IMPV contact was observed in only 25.3% (n = 116), and 36.2% (n = 166) had no IMPV contact at all. Receiver operating characteristic analysis revealed that "major IMPV contact" was more accurate in predicting iIMN+ (area under the curve, 0.85) compared with a multivariate model combining grade of differentiation, tumor site, size, and molecular subtype (area under the curve, 0.65). Strikingly, among patients with cIMN+, 100% of tumors had contact with a crossing contralateral IMPV, whereas in cIMN- patients, IMPVs to the contralateral side were observed in only 53.4% (iIMN+) and 24.8% (iIMN-), respectively.

CONCLUSIONS

Tumor contact with the IMPV is highly associated with risk of gross IMN involvement. Further studies are warranted to investigate whether this identified risk factor is also associated with microscopic IMN involvement and whether it can assist in the selection of patients with breast cancer for irradiation of the internal mammary lymph nodes.

Methods of Sentinel Lymph Node Detection and Management in Urinary Bladder Cancer—A Narrative Review

Introduction: Detection of lymph node status in bladder cancer significantly impacts clinical decisions regarding its management. There is a wide range of detection modalities for this task, including lymphoscintigraphy, computed tomography, magnetic resonance imaging, single-photon emission computed tomography, positron emission tomography, and fluoroscopy. We aimed to study the pre- and intraoperative detection modalities of sentinel lymph nodes in urinary bladder cancer. Method: This narrative review was performed by searching the PubMed and EMBASE libraries using the following search terms: (“Transitional cell carcinoma of the bladder” OR “urothelial cancer” OR “urinary bladder cancer” OR “bladder cancer”) AND ((“sentinel lymph node”) OR (“lymphatic mapping”) OR (“lymphoscintigraphy”) OR (“lymphangiography”) OR (“lymph node metastases”)). Studies analysing the effectiveness and outcomes of sentinel lymph node detection in bladder cancer were included, while non-English language, duplicates, and non-article studies were excluded. After analysing the libraries and a further manual search of bibliographies, 31 studies were included in this paper. We followed the RAMESES publication standard for narrative reviews to produce this paper. Results: Of the 31 studies included, 7 studies included multiple detection methods; 5 studies included lymphoscintigraphy; 5 studies included computed tomography and/or single-photon emission computed tomography; 5 studies included fluoroscopy; 4 studies included magnetic resonance imaging; and 5 studies included positron emission tomography. Discussion: Anatomical, radioactive, and functional detection modalities have been studied independently and in combination. The consensus is that preoperative detection with imaging helps guide surgical management and intraoperative detection methods help capture any lymph nodes that may have been missed. Each of these types of detection represent their own set of benefits and drawbacks, but there is currently limited evidence to support any change in overall practice to replace conventional staging.

The bright future of nanotechnology in lymphatic system imaging and imaging-guided surgery

Lymphatic system is identified the second vascular system after the blood circulation in mammalian species, however the research on lymphatic system has long been hampered by the lack of comprehensive imaging modality. Nanomaterials have shown the potential to enhance the quality of lymphatic imaging due to the unparalleled advantages such as the specific passive targeting and efficient co-delivery of cocktail to peripheral lymphatic system, ease molecular engineering for precise active targeting and prolonged retention in the lymphatic system of interest. Multimodal lymphatic imaging based on nanotechnology provides a complementary means to understand the kinetics of lymphoid tissues and quantify its function. In this review, we introduce the established approaches of lymphatic imaging used in clinic and summarize their strengths and weaknesses, and list the critical influence factors on lymphatic imaging. Meanwhile, the recent developments in the field of pre-clinical lymphatic imaging are discussed to shed new lights on the design of new imaging agents, the improvement of delivery methods and imaging-guided surgery strategies.

Artificial intelligence in single photon emission computed tomography (SPECT) imaging: a narrative review

Artificial intelligence (AI) has been widely applied to medical imaging. The use of AI for emission computed tomography, particularly single-photon emission computed tomography (SPECT) emerged nearly 30 years ago but has been accelerated in recent years due to the development of AI technology. In this review, we will describe and discuss the progress of AI technology in SPECT imaging. The applications of AI are dispersed in disease prediction and diagnosis, post-reconstruction image denoising, attenuation map generation, and image reconstruction. These applications are relevant to many disease categories such as the neurological disorders, kidney failure, cancer, heart disease, etc. This review summarizes these applications so that SPECT researchers can have a reference overview of the role of AI in current SPECT studies. For each application, we followed the timeline to present the evolution of AI’s usage and offered insights on how AI was combined with the knowledge of underlying physics as well as traditional non-learning techniques. Ultimately, AI applications are critical to the progress of modern SPECT technology because they provide compensations for many deficiencies in conventional SPECT imaging methods and demonstrate unparalleled success. Nonetheless, AI also has its own challenges and limitations in the medical field, including SPECT imaging. These fundamental questions are discussed, and possible future directions and countermeasures are suggested.

Hybrid (2D/3D) Dosimetry of Radiolabeled Gold Nanoparticles for Sentinel Lymph Node Detection in Patients with Breast Cancer

Previously, we reported the preparation and preclinical studies of ^99mTc-labeled gold nanoparticles-mannose (^99mTc-AuNP-mannose) with potential for sentinel lymph node (SLN) detection by using nuclear medicine procedures. This study aimed to evaluate the biokinetics and hybrid (2D/3D) dosimetry of ^99mTc-AuNP-mannose in five patients with breast cancer under a sentinel lymph node detection protocol. Anterior and posterior whole-body planar images (2D, at 0.5, 2, 6, and 24 h) and single-photon emission computed tomography (3D at 6.5 h)/computed tomography (SPECT/CT) images were acquired after ^99mTc-AuNP-mannose administration (37 MBq). Through a hybrid quantification method, activity in tissues of interest at the different acquisition times was determined and integrated over time to obtain the total nuclear transformations (N), as well as the mean residence time, in each tissue. N values and the OLINDA code were used for estimating the internal radiation absorbed doses. Results demonstrated that ^99mTc-AuNP-mannose successfully accumulates and remains up to 24 h in the sentinel lymph node without detectable migration to other lymph nodes and no side effects on patients. Negligible absorption of the radiolabeled nanoparticles into the circulatory system was observed, from which the radio-nanosystem is rapidly eliminated by kidneys. Hybrid (2D/3D) dosimetry evaluations showed equivalent doses to SLN, breast, and kidneys of 172.34, 5.32, and 0.08 mSv/37 MBq, respectively, with an effective dose of 2.05E - 03 mSv/MBq. The mean effective residence time in SLN was 0.92 h. This preliminary study indicates that the use of ^99mTc-AuNP-mannose for successful SLN detection in patients is safe, producing an effective dose at the level recommended for diagnostic studies (<10 mSv).

Comparison between planar, SPECT and SPECT/computed tomography systems in 99mTc- nanocolloid sentinel lymph node imaging: phantom design and clinical investigations

PURPOSE

It was aimed to examine the performance of planar, SPECT and SPECT/CT in lymph nodes detection of breast cancer.

MATERIALS AND METHODS

In-house made phantom was immersed in water-filled container. Disparate activities were injected into spheres emulating breast tumour (1.5 cm), and adjacent lymph nodes (1, 0.5 and 0.25 cm). Planar, SPECT and SPECT/CT scans were made at depths of 1, 3, 5, 7 and 9 cm. Rose Criteria was employed to investigate the detectability in planar imaging, and contrast to noise ratios (CNRs) were used in SPECT and SPECT/CT images. SPECT and SPECT/CT of 20 patients were randomly incorporated in the current study.

RESULTS

CNR values from planar images at 1 cm depth for the simulated nodes of 1, 0.5and 0.25 cm were 36, 18 and 17, respectively. Whereas, those from SPECT/CT were 94.5, 63.3 and 20.9, repectively. CNRs from SPECT were lower than SPECT/CT in order of 60.1, 41.8 and 17.1 at the same depth. At 9 cm, CNR values of 1, 0.5 and 0.25 cm from the planar images were 14, 6 and 5, respectively. While CNR values from SPECT were higher as 53.6, 38.0, and 14.9, respectively, and the greatest CNRs were in SPECT/CT as 85.7, 55.8, and 19.1, repectively.

CONCLUSION

The CNR values in SPECT/CT were 1.5- and 3.5-folds higher than SPECT and planar imaging at depth range 1-9 cm. The patients study exhibited larger SPECT/CT CNRs over SPECT as great as 1.6-fold.

Comparison between single photon emission computed tomography with computed tomography and planar scintigraphy in sentinel node biopsy in breast cancer patients

Objective

Radio-guided sentinel node (SN) biopsy is a standard method used in the treatment of early breast cancer. Single photon emission computed tomography with computed tomography (SPECT/CT) has been commonly used for SN detection. SPECT/CT adds precise anatomical information of SN sites, and it is reported that more SNs may be detectable on SPECT/CT than on planar imaging. We here investigate which breast cancer patients have benefited from SPECT/CT over planar imaging.

Methods

A total of 273 breast cancer patients including 80 with ipsilateral breast tumor relapse (IBTR) underwent both multiple-view planar imaging and SPECT/CT for SN detection. The number of SNs, the patients who had benefitted from SPECT/CT, and the SN procedure failure rate were compared between SPECT/CT and planar imaging. Factors influencing the visualization of para-sternal and ipsilateral level II, III nodes, and contralateral axillary nodes were also analyzed using logistic regression analysis.

Results

The number of hot spots did not differ between SPECT/CT and multiple-view planar imaging. Eight contaminated patients and 52 patients with visualized extra-level I axillary nodes benefited from identifying precise anatomical sites. Even though radioactive nodes could be harvested in most (192/193) of the non-IBTR patients (7/8 in non-SN visible patients), no radioactive nodes could be found during surgery in 11 of 80 IBTR patients. Axillary surgery (dissection) increased the visualization of para-sternal and level II, III axillary nodes, and previous irradiation increased the visualization of contralateral axillary nodes.

Conclusion

Multiple-view planar imaging was equivalent to SPECT/CT for depicting hot nodes for radio-guided SN detection in breast cancer. SPECT/CT was useful when precise anatomical information was necessary, especially regarding sentinel lymph nodes other than ipsilateral axilla. Logistic regression analysis revealed that axillary surgery (dissection) increased the visualization of para-sternal and level II, III axillary nodes, and the only relevant factor influencing visualization of contralateral axillary SNs was previous radiation to the breast.

Hybrid 99mTc-magnetite tracer for dual modality sentinel lymph node mapping

Accuracy of sentinel lymph node identification using radioactive tracers in non-superficial cancers can be limited by radiation shine through and low spatial resolution of detection systems such as intraoperative gamma probes. By utilising a dual radioactive/magnetic tracer, sensitive lymphoscintigraphy can be paired with high spatial resolution intraoperative magnetometer probes to improve the accuracy of sentinel node detection in cancers with complex multidirectional lymphatic drainage. Dextran-coated magnetite nanoparticles (33 nm mean hydrodynamic diameter) were labelled with ^99mTc and applied as a lymphotropic tracer in small and large animal models. The dual tracer could be radiolabelled with 98 ± 2% efficiency after 10 min of incubation at room temperature. Biodistribution studies of the tracer were conducted in normal rats (subdermal and intravenous tail delivery, n = 3) and swine (subdermal hind limb delivery, n = 5). In rats the dual tracer migrated through four tiers of lymph node, 20 min after subdermal injection. Results from intravenous biodistribution test for radiocolloids demonstrated no aggregation in vivo, however indicated the presence of some lower-molecular weight radioactive impurities (^99mTc-dextran). In swine, the dual tracer could be effectively used to map lymphatic drainage from hind hoof to popliteal and inguinal basins using intraoperative gamma and magnetometer probes. Of the eight primary nodes excised, eight were positively identified by gamma probe and seven by magnetometer probe. The high-purity dual tracer shows early promise for sentinel node identification in complex lymphatic environments by combining sensitive preoperative lymphoscintigraphy with a high-resolution intraoperative magnetometer probe.

Selective Sentinel Lymph Node Biopsy and Primary Systemic Therapy in Breast Cancer

Aims and background

Sentinel lymph node biopsy has become an ordinary method for breast cancer staging. Neoadjuvant chemotherapy has been considered one of the contraindications for sentinel lymph node biopsy due to potential secondary fibrosis and lymphatic distortion. Timing and influence on sentinel lymph node biopsy result by primary systemic therapy are current and controversial topics.

Methods and study design

The experience in the medical literature is reviewed. A search was performed in the following databases: Medline (through Pubmed), EMBASE, Tripdatabase and Cochrane Library, between January 1998 and December 2008.

Results and conclusions

After analyzing the conclusions from 42 series and waiting for the end of related prospective trials, it could be concluded that sentinel lymph node biopsy is a useful diagnostic tool that should be integrated in the algorithm for the management of breast cancer patients when primary systemic therapy is needed.

Value and efficiency of sentinel lymph node diagnostics in patients with penile carcinoma with palpable inguinal lymph nodes as a new multimodal, minimally invasive approach

PURPOSE

The international guidelines recommend sentinel lymph node biopsy (SLNB) for lymph node staging in penile cancer with non-palpable inguinal lymph nodes (LN) but it is not recommended with palpable inguinal LN. The aim of this study was to evaluate the reliability and morbidity of SLNB in combination with an ultrasound-guided resection of suspect inguinal LNs as a new multimodal, minimally invasive staging approach in these patients.

METHODS

We performed SLNB in 26 penile cancer patients with 42 palpable inguinal LNs. Prior to the combined staging procedures the patients underwent an ultrasound examination of the groins as well as planar lymphatic drainage scintigraphy and SPECT/CT scans. During the surgical procedure, the radioactive-labelled sentinel lymph nodes and, in addition, sonographically suspect LNs, were resected under ultrasound guidance. Follow-up screening was done by ultrasound examination of the groins according to the guidelines of the European Association of Urology.

RESULTS

Nineteen groins of 42 preoperatively palpable inguinal findings were histologically tumor-positive. SLNB alone showed lymphogenic metastases in 14 groins. Sonography revealed five further metastatic groins, which would not have been detected during SLNB due to a tumor-related blockage of lymphatic drainage or a so-called re-routing of the tracer. During follow-up, none of the 28 groins with tumor-negative LN status showed any LN recurrence in this combined investigation technique. The median follow-up period was 46 (24 to 92) months. Morbidity of this procedure was low at 4.76 % in relation to the number of groins resp. 7.69 % in relation to the number of patients.

CONCLUSIONS

The results show that this combined procedure is a reliable multimodal diagnostic approach for treatment of penile cancer patients with palpable inguinal LNs. It is associated with low morbidity rates. SLNB alone would lead to a significantly higher false-negative rate in these patients. The encouraging results of this work can extend the range of indications for nuclear medicine in the form of SLNB using radioactive tracers in this patient group.

SPECT-CT-Guided Thoracoscopic Biopsy of Sentinel Lymph Nodes in the Internal Mammary Chain in Patients With Breast Cancer: A Pilot Study

OBJECTIVE

The objective of this study was to determine the impact of the use of single-photon emission computed tomography fused with computed tomography (SPECT-CT) on thoracoscopic biopsy of sentinel lymph nodes (SLNs) in the internal mammary chain in patients with breast cancer by evaluating resultant changes in staging and their clinical implications.

METHODS

Between September 2010 and January 2014, we performed lymphoscintigraphy-assisted thoracoscopic biopsy of the internal mammary chain SLN in 20 patients with breast cancer. Single-photon emission computed tomography fused with computed tomography was also used in 13 of these patients. The sentinel nodes were surgically identified with the aid of a gamma probe.

RESULTS

Sentinel lymph nodes were identified surgically in 19 of 20 patients. In the 13 patients in whom SPECT-CT was used, it readily identified SLNs, especially when they were located over an intercostal space. Change of staging occurred in three patients (15%), two of whom accordingly received adjuvant radiotherapy to the internal thoracic chain.

CONCLUSIONS

Compared with lymphoscintigraphy alone, the use of SPECT-CT improves localization of the SLN in the internal mammary chain, allowing more accurate planning of each individual's treatment.

Role of SPECT-CT in breast cancer sentinel node biopsy when internal mammary chain drainage is observed

INTRODUCTION

SPECT-CT in the detection of the sentinel lymph node (SLN) of breast cancer offers known advantages over conventional planar lymphoscintigraphy. Sometimes, it shows atypical findings like mediastinal lymphatic drainage. We have evaluated these atypical findings showed by SPECT-CT performed in patients with migration to the internal mammary chain (IMC) and their roles in the management of the patients.

MATERIALS AND METHODS

We reviewed the 56 lymphoscintigraphies (planar and SPECT-CT) of 56 women (average age: 55 years) diagnosed with breast cancer with IMC migration observed in the planar images. We compared the two techniques, obtaining the number of depicted nodes, atypical locations, their exact anatomical location and their role in the management of the patient.

RESULTS

Planar images showed a total number of 81 IMC nodes. SPECT-CT showed 74 nodes in the IMC territory and 14 mediastinal lymphatic nodes in 6 patients. Out of the 81 IMC nodes reported by planar images, seven corresponded to mediastinal nodes. Planar and hybrid images showed 110 and 130 axillary nodes, respectively. SPECT-CT showed additional findings in five patients: three infraclavicular and two supraclavicular nodes that were exactly located. One intramammary node was discarded by the SPECT-CT as a focal skin contamination.

CONCLUSION

Mediastinal nodes are unexpected, but not uncommon findings that are important in the planning of SLN biopsy. SPECT-CT found more nodes than planar images, being able to separate mediastinal and IMC nodes, helping to exactly depict the SLN and its relations with anatomical structures.

SPECT/CT for SLN dissection in vulvar cancer: Improved SLN detection and dissection by preoperative three-dimensional anatomical localisation

OBJECTIVE

In this study, we assessed the feasibility and clinical advantages of single photon emission computed tomography with CT (SPECT/CT) for sentinel lymph node (SLN) detection in vulvar cancer.

METHODS

This is a unicentric prospective trial. Vulvar cancer patients underwent preoperative SLN marking (10MBq Technetium (TC)-99m-nanocolloid) and subsequent planar lymphoscintigraphy (LSG) and SPECT/CT for SLN visualization. Directly before surgery, a patent blue dye was injected. We assessed detection rates of SPECT/CT and those of planar LSG and intraoperative detection. We analyzed the sensitivity, negative predictive value and false negative rate.

RESULTS

At Hannover Medical School, 40 vulvar cancer patients underwent SLN dissection after preoperative LSG and SPECT/CT. The mean diameter of all tumors in final histology was 2.23 (0.1-10.5) cm with a mean tissue infiltration of 3.93 (0.25-11) mm. In preoperative imaging, SPECT/CT identified significantly more SLNs (mean 8.7 (1-35) LNs per patient) compared to LSG (mean 5.9 (0-22) LNs, p<0.01). In addition, SPECT/CT led to a high spatial resolution and anatomical localization of SLNs. Thus, SPECT/CT identified aberrant lymphatic drainage in 7/40 (17.5%) patients. There were no significant differences, but significant correlation was found between SPECT/CT and intraoperative SLN identification. Regarding inguino-femoral LNs, for all patients who underwent complete groin dissection, sensitivity was 100%, NPV was 100% and false negative rate was 0%.

CONCLUSION

SPECT/CT leads to higher SLN identification compared to LSG in vulvar cancer. Due to its higher spatial resolution and three-dimensional anatomical localisation of SLNs, SPECT/CT provides the surgeon with important additional information, facilitates intraoperative SLN detection and predicts aberrant lymphatic drainage.

Role of SPECT/CT in sentinel lymph node detection in patients with breast cancer

AIM

The purpose of this study was to conduct a systematic review of the published literature to assess the role (indications, advantages, and limitations) of SPECT/CT for the detection of sentinel lymph node (SLN) in breast cancer.

METHODS

The authors searched PubMed for published literature in English addressing this topic.

RESULTS

Eleven studies, published since 2006, focused on the role and value of SPECT/CT for SLN detection (SLND). They showed that SPECT/CT improved sentinel node detection and anatomical localization. One study suggested that SPECT/CT may provide a more accurate staging. Limitations for SLND with SPECT/CT include extra time and inconvenience for the patient and additional radiation dose.

CONCLUSIONS

SPECT/CT is a valuable tool for SLND, especially in difficult cases, when planar lymphoscintigraphy shows no SLN or unexpected lymphatic drainage.

Risk of node metastasis of sentinel lymph nodes detected in level II/III of the axilla by single-photon emission computed tomography/computed tomography

In breast cancer, single-photon emission computed tomography/computed tomography (SPECT/CT) shows the exact anatomical location of sentinel nodes (SN). SPECT/CT mainly exposes axilla and partly exposes atypical sites of extra-axillary lymphatic drainage. The mechanism of how the atypical hot nodes are involved in lymphatic metastasis was retrospectively investigated in the present study, particularly at the level II/III region. SPECT/CT was performed in 92 clinical stage 0-IIA breast cancer patients. Sentinel lymph nodes are depicted as hot nodes in SPECT/CT. Patients were divided into two groups: With or without hot node in level II/III on SPECT/CT. The existence of metastasis in level II/III was investigated and the risk factors were identified. A total of 12 patients were sentinel lymph node biopsy metastasis positive and axillary lymph node dissection (ALND) was performed. These patients were divided into two groups: With and without SN in level II/III, and nodes in level II/III were pathologically proven. In 11 of the 92 patients, hot nodes were detected in level II/III. There was a significant difference in node metastasis depending on whether there were hot nodes in level II/III (P=0.0319). Multivariate analysis indicated that the hot nodes in level II/III and lymphatic invasion were independent factors associated with node metastasis. There were 12 SN-positive patients followed by ALND. In four of the 12 patients, hot nodes were observed in level II/III. Two of the four patients with hot nodes depicted by SPECT/CT and metastatic nodes were pathologically evident in the same lesion. Therefore, the present study indicated that the hot node in level II/III as depicted by SPECT/CT may be a risk of SN metastasis, including deeper nodes.

Breast cancer patient with an uncommon lymphatic drainage evidenced by SPECT/CT

SPECT/CT reinforces the role of lymphoscintigraphy in breast cancer by solving some cases with difficult reading on planar scintigraphy. An 80-year-old woman was referred to our institution for management of a screen-detected, nonpalpable, invasive lobular carcinoma of lower inner quadrant of the left breast. Lymphoscintigraphy was performed before surgery. Planar images showed an axillary sentinel node and 2 medially located hot spots. SPECT/CT allowed determining that one of the extra-axillary drainage sites was to the internal mammary basin, while the second corresponded to a mediastinal lymph node. Although this drainage was unexpected, mediastinum is a common site of breast cancer recurrence.

Improved detection of sentinel lymph nodes in SPECT/CT images acquired using a low- to medium-energy general-purpose collimator

PURPOSE

The use of the low-energy high-resolution (LEHR) collimator for lymphoscintigraphy causes the appearance of star-shaped artifacts at injection sites. The aim of this study was to confirm whether the lower resolution of the low- to medium-energy general-purpose (LMEGP) collimator is compensated by decrease in the degree of septal penetration and the reduction in star-shaped artifacts.

METHODS

A total of 106 female patients with breast cancer, diagnosed by biopsy, were enrolled in this study. Tc phytate (37 MBq, 1 mCi) was injected around the tumor, and planar and SPECT/CT images were obtained after 3 to 4 hours. When sentinel lymph nodes (SLNs) could not be identified from planar and SPECT/CT images by using the LEHR collimator, we repeated the study with the LMEGP collimator.

RESULTS

Planar imaging performed using the LEHR and LEHR + LMEGP collimators positively identified SLNs in 96.2% (102/106) and 99.1% (105/106) of the patients, respectively. Using combination of planar and SPECT/CT imaging with the LEHR and LEHR + LMEGP collimators, SLNs were positively identified in 97.2% (103/106) and 100% (106/106) of the patients, respectively.

CONCLUSIONS

The LMEGP collimator provided better results than the LEHR collimator because of the lower degree of septal penetration. The use of the LMEGP collimator improved SLN detection.

Status of sentinel lymph node for breast cancer

Long-awaited results from randomized clinical trials designed to test the validity of sentinel lymph node biopsy (SLNB) as replacement of axillary lymph node dissection (ALND) in management of early breast cancer have recently been published. All the trials conclude SLNB has survival rates comparable to those of ALND (up to 10 years in one study) and conclude SLNB has less morbidity than ALND. All the trials support replacing ALND with SLNB for staging in early breast cancer; all support SLNB as the standard of care for such cancer. The SLNB protocols used in the trials varied, and no consensus that would suggest a standard protocol exists. The results of the trials and of other peer-reviewed research do, however, suggest a framework for including some specific methodologies in accepted practice. This article highlights the overall survival and disease-free survival data as reported from the clinical trials. This article also reviews the status of SLN procedures and the following: male breast cancer, the roles of various imaging modalities (single-photon emission computed tomography/computed tomography, positron emission tomography/computed tomography, and ultrasound), ductal carcinoma in situ, extra-axillary SLNs, SLNB after neoadjuvant chemotherapy, radiation exposure to patients and medical personnel, and a new radiotracer that is the first to label SLNs not by particle trapping but by specific macrophage receptor binding. The proper Current Procedural Terminology (CPT) code for lymphoscintigraphy and SLN localization prior to surgery is 78195.

Molecular imaging agents for SPECT (and SPECT/CT)

The development of hybrid single photon emission computed tomography/computed tomography (SPECT/CT) cameras has increased the diagnostic value of many existing single photon radiopharmaceuticals. Precise anatomical localization of lesions greatly increases diagnostic confidence in bone imaging of the extremities, infection imaging, sentinel lymph node localization, and imaging in other areas. Accurate anatomical localization is particularly important prior to surgery, especially involving the parathyroid glands and sentinel lymph node procedures. SPECT/CT plays a role in characterization of lesions, particularly in bone scintigraphy and radioiodine imaging of metastatic thyroid cancer. In the development of novel tracers, SPECT/CT is particularly important in monitoring response to therapies that do not result in an early change in lesion size. Preclinical SPECT/CT devices, which actually have spatial resolution superior to PET/CT devices, have become essential in characterization of the biodistribution and tissue kinetics of novel tracers, allowing coregistration of serial studies within the same animals, which serves both to reduce biological variability and reduce the number of animals required. In conclusion, SPECT/CT increases the utility of existing radiopharmaceuticals and plays a pivotal role in the evaluation of novel tracers.

SPECT/CT and tumour imaging

Scintigraphic techniques are sensitive imaging modalities in the diagnosis and follow-up of cancer patients providing the functional and metabolic activity characteristics of the tumour. Hybrid SPECT/CT improves the diagnostic accuracy of these well-established imaging techniques by precise anatomical localization and characterization of morphological findings, differentiation between foci of physiological and pathological tracer uptake, resulting in a significant impact on patient management and more definitive interpretations. The use of SPECT/CT has been studied in a variety of applications in tumour imaging which are reviewed in this article. By combining functional and anatomical information in a single imaging session, SPECT/CT has become a one-stop cancer imaging modality.

Lymphoscintigraphy with single-photon emission computed tomography/computed tomography is useful for determining the site of chyle leakage after esophagectomy

We describe the case of chylothorax after esophagectomy for esophageal carcinoma. Lymphoscintigraphy with Tc-99m-human serum albumin-diethylenetriaminepentaacetic acid showed an abnormal radioisotope accumulation on the left side of the thoracic duct. Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) revealed a hot spot directly on the site at, which the thoracic duct was ligated during surgery, which was the suggested site of chyle leakage. We emphasize that lymphoscintigraphy with SPECT/CT is very useful tool for accurately identifying the site of the chyle leakage.

SPECT/CT in sentinel node imaging

Sentinel node lymphoscintigraphy and biopsy has become standard practice for lymphatic staging in early-stage breast cancer and melanoma. More recently, sentinel node lymphoscintigraphy has also been used in head and neck squamous cell cancers and other solid tumours. Single photon emission computed tomography/computed tomography (SPECT/CT) is a new tool and this article reviews its potential application in sentinel node imaging. SPECT/CT provides complementary functional and anatomical information and has been shown to be superior to planar imaging in a number of indications. The advantages include more accurate anatomical localization, identification of false positives (due to contamination or spillover from the injection site), reduction in the number of false negatives (visualization of nodes not seen on planar imaging) and alteration of the surgical approach. We thus believe that sentinel lymph node SPECT/CT can provide valuable information before sentinel lymph node biopsy and advocate its use in a range of tumours such as truncal and head and neck melanomas.

The role of hybrid SPECT/CT for lymphatic mapping in patients with melanoma

INTRODUCTION

Lymphoscintigraphy in melanoma provides important information on the dynamic drainage of the primary tumour and the location of the sentinel lymph node (SLN). Unfortunately these images lack anatomical detail. Single positron emission computed tomography/computed tomography (SPECT/CT) provides extremely detailed information on the location of the SLN and its relationship with surrounding structures and it is the aim of this study to report our initial experience with this technology.

METHODS

Thirty-two patients undergoing sentinel lymph node biopsy (SLNB) at our unit between October 2010 and October 2011 were included in this study. In each case, conventional planar lymphoscintigraphy (PL) was followed by SPECT/CT. Images of each patient were reviewed by the operating consultant plastic surgeon and a consultant radiologist. A joint opinion was issued on the number of lymph nodes identified by each imaging modality and whether SPECT/CT influenced surgical approach.

RESULTS

Both PL and SPECT/CT detected the SLN in 31/32 patients. There was no significant difference between the number of SLN identified by PL and SPECT (p = 0.69). In relation to the true number of SLNs identified intra-operatively by gamma probing and blue dye, there was no statistically significant difference in accuracy between SPECT/CT and PL (p = 0.50). SPECT/CT was judged to provide useful anatomical information in all cases. Surgical approach was altered in 12/32 patients and contributed to the detection of SLNs that were positive for metastases.

CONCLUSIONS

In relation to true SLN number, SPECT/CT was not significantly more accurate than PL. The detailed anatomical information provided by SPECT/CT improved confidence and pre-operative planning in all patients. In select cases, particularly in the head and neck, SPECT/CT overcame the limitations of PL and facilitated the detection and sampling of metastatic nodes.

Detection of Sentinel Lymph Nodes in Gynecologic Tumours by Planar Scintigraphy and SPECT/CT

Objective: Assess the role of planar lymphoscintigraphy and fusion imaging of SPECT/CT in sentinel lymph node (SLN) detection in patients with gynecologic tumours.

Material and Methods: Planar scintigraphy and hybrid modality SPECT/CT were performed in 64 consecutive women with gynecologic tumours (mean age 53.6 with range 30-77 years): 36 pts with cervical cancer (Group A), 21 pts with endometrial cancer (Group B), 7 pts with vulvar carcinoma (Group C). Planar and SPECT/CT images were interpreted separately by two nuclear medicine physicians. Efficacy of these two techniques to image SLN were compared.

Results: Planar scintigraphy did not image SLN in 7 patients (10.9%), SPECT/CT was negative in 4 patients (6.3%). In 35 (54.7%) patients the number of SLNs captured on SPECT/CT was higher than on planar imaging. Differences in detection of SLN between planar and SPECT/CT imaging in the group of all 64 patients are statistically significant (p<0.05). Three foci of uptake (1.7% from totally visible 177 foci on planar images) in 2 patients interpreted on planar images as hot LNs were found to be false positive non-nodal sites of uptake when further assessed on SPECT/CT. SPECT/CT showed the exact anatomical location of all visualised sentinel nodes.

Conclusion: In some patients with gynecologic cancers SPECT/CT improves detection of sentinel lymph nodes. It can image nodes not visible on planar scintigrams, exclude false positive uptake and exactly localise pelvic and paraaortal SLNs. It improves anatomic localization of SLNs.

Conflict of interest:None declared.

Hybrid imaging in planar scintigraphy: new implementations and historical precedents

Fusion of tomographic radionuclide studies with anatomical examinations has become standard practice in positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging. Nonetheless, fusion of planar scintigraphic images with an anatomical modality remains distinctly uncommon, although methods to do so have appeared sporadically in the literature during the past 2 decades. In this article we review several techniques that have been used to combine planar scintigraphic images with radiographs and visual (photographic) images. Rigid or affine transformations have been performed to co-register the planar images with each other using custom, commercial, or public domain software. Display of the hybrid images has been achieved primarily with nonselective color-fusion methods. Promising efforts are underway to develop a technique of fusing planar lymphoscintigraphic images with CT topograms (scout images) obtained on the SPECT-CT camera in a manner that compensates for position-dependent variation in magnification that affects the CT scout. An advantage of this approach is that both of the component images are acquired on the same gantry, without need for repositioning of the patient. It is instructive to note that techniques of fusing rectilinear scans with radiographic and visual images were first developed more than 50 years ago. The revisiting of these methods after many decades reflects a fundamental need for spatial orientation in nuclear medicine that fusion imaging can also bring to planar scintigraphic studies.

Diffusion-weighted magnetic resonance imaging in patients selected for radical cystectomy: detection rate of pelvic lymph node metastases

OBJECTIVE

To evaluate whether DW-MRI improves the detection of pelvic lymph nodes metastates in patients with bladder cancer undergoing radical cystectomy.

PATIENTS AND METHODS

36 patients with CT scan negative for nodal metastates underwent DW-MRI before surgery. Diagnostic accuracy of DW-MRI was compared with histopathological findings.

RESULTS

Mean ADC value was 0.85 × 10(-3) mm(3)/s in the nodal metastatic group and 1 × 10(-3) mm(3)/s in the nodal non-metastatic group (P = 0.02). The ADC cut-off value, obtained by the ROC curve was 0.86 × 10(-3) mm(3)/s. Patient-based sensitivity, specificity and positive and negative predictive values were 76.4%, 89.4%, 26.6%, and 71.4%, respectively.

CONCLUSION

DW-MRI may be used to differentiate metastatic from non-metastatic lymph nodes in patients with high-grade bladder cancer.

Automated lymph node detection and classification on breast and prostate cancer SPECT-CT images

We present a novel detection and classification method to process SPECT-CT images representing breast and prostate lymph nodes. Lymph nodes are those nodes that are near the primer tumor and may become cancerous in time, hence their early detection is a key factor for the successful treatment of the patient. Prior methods focus on the visual aid to manually detect the lymph nodes which still makes the process time-consuming. Other solutions segment the lymph nodes only on CT, where the small lymph nodes may not be located accurately. Our solution processed both SPECT and CT data to provide an accurate classification of all SPECT hot spots. The method has been validated on a huge amount of medical data. Results show that our method is a very effective tool to support physicians working with related images in the field of nuclear medicine.

Hybrid Modality Fusion of Planar Scintigrams and CT Topograms to Localize Sentinel Lymph Nodes in Breast Lymphoscintigraphy: Technical Description and Phantom Studies

Lymphoscintigraphy is a nuclear medicine procedure that is used to detect sentinel lymph nodes (SLNs). This project sought to investigate fusion of planar scintigrams with CT topograms as a means of improving the anatomic reference for the SLN localization. Heretofore, the most common lymphoscintigraphy localization method has been backlighting with a (57)Co sheet source. Currently, the most precise method of localization through hybrid SPECT/CT increases the patient absorbed dose by a factor of 34 to 585 (depending on the specific CT technique factors) over the conventional (57)Co backlighting. The new approach described herein also uses a SPECT/CT scanner, which provides mechanically aligned planar scintigram and CT topogram data sets, but only increases the dose by a factor of two over that from (57)Co backlighting. Planar nuclear medicine image fusion with CT topograms has been proven feasible and offers a clinically suitable compromise between improved anatomic details and minimally increased radiation dose.

Hybrid imaging (SPECT/CT and PET/CT)--improving the diagnostic accuracy of functional/metabolic and anatomic imaging

In-line combined systems, single-photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT, allow an instant generation of fused images of scintigraphy and CT data. The accumulated clinical data on the use of these systems in various clinical scenarios indicate that this hybrid technology improves the diagnostic accuracy as compared to scintigraphy and CT alone and even to side-by-side interpretation of scintigraphy and CT, which were acquired separately. The improved diagnostic accuracy is reflected by improving image quality of SPECT and PET, detection of more clinically relevant lesions, better localization of disease and differentiation between physiologic and pathologic uptake, characterization of disease by its functional and morphologic appearance before and after therapy and accurate delineation of disease, optimizing biopsy and therapy planning.

First demonstration of 3-D lymphatic mapping in breast cancer using freehand SPECT

PURPOSE

Freehand SPECT is a 3-D tomographic imaging modality based on data acquisition with a hand-held detector that is moved freely, in contrast to conventional, fixed gamma camera systems. In this pilot study, the feasibility of freehand SPECT for 3-D lymphatic mapping in breast cancer was evaluated.

METHODS

A total of 85 patients (age: 29-88 years) with an initial diagnosis of invasive breast cancer and no clinical evidence of nodal involvement prospectively underwent sentinel lymph node (SLN) biopsy. Preoperative lymphatic mapping (35-87 MBq (99m)Tc-Nanocoll) included tomographic imaging with a SPECT/CT device (Siemens Symbia T6) serving as reference. Initially, the freehand SPECT approach was assessed in a pilot study consisting of 50 patients. The quality of each freehand SPECT acquisition was assessed and ranked as good, intermediate or poor. In another series comprising a further 35 patients (validation study), a guidance system for the acquisition was implemented based on the results of the pilot study, ensuring acquisitions with good quality. For 3-D tomographic image reconstruction, ad hoc models and iterative reconstruction algorithms were used in all 85 patients. To allow for adequate comparison, SPECT/CT data and freehand SPECT data were registered within the same coordinate system.

RESULTS

In the pilot study, freehand SPECT enabled mapping of 24 of 83 SLNs in 20 of 44 patients (3 dropouts, 3 patients without SLN either in SPECT/CT or in freehand SPECT). Using SPECT/CT as reference, the accuracy of freehand SPECT was 77.8% (7/9 nodes) in scans with good quality, while for intermediate and poor quality scans, the accuracy was reduced to 34.3 and 12.8%, respectively. In the validation study, quality feedback improved the results significantly and freehand SPECT enabled the mapping of at least one SLN in 87.5% of the patients (28/32 - 3 dropouts). Compared to the reference method, freehand SPECT showed a sensitivity of 83.3% (35/42 nodes). False-negative findings were related to insufficient scanning time, insufficient coverage of the axillary region, close proximity of the SLN to the injection site and low tracer uptake in the SLNs.

CONCLUSION

In this preliminary study, we could demonstrate that 3-D localization of SLNs is feasible using freehand SPECT technology. Prerequisites for acquisition of a good scan quality, most likely allowing precise SLN mapping, have been defined. This approach has high potential to allow image-guided biopsy and further standardization of SLN dissection, thus bringing 3-D nuclear imaging into the operating room.

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).