Problems and prospects of modern lymph node imaging

In Vitro Studies Regarding the Safety of Chitosan and Hyaluronic Acid-Based Nanohydrogels Containing Contrast Agents for Magnetic Resonance Imaging

The aim of this study was to investigate the biocompatibility of contrast agents, such as gadolinium 1, 4, 7, 10 tetraazacyclo-dodecane tetraacetic acid (GdDOTA) and gadolinium dioctyl terephthalate (GdDOTP), encapsulated in a polymeric matrix containing chitosan and hyaluronic acid using RAW264.7 murine macrophages and human blood samples. The cell viability and cytotoxicity were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, while cell cycle analysis was determined in RAW264.7 cells using flow cytometry. The mitochondrial membrane potential (MMP), hemolytic index, complement activation, and thrombogenic potential of gadolinium (Gd) containing nanohydrogels were measured by fluorometric and spectrophotometric methods. Taken together, our results demonstrate the good bio- and hemocompatibility of chitosan-based nanohydrogels with the RAW264.7 cell line and human blood cells, suggesting that these could be used as injectable formulations for the magnetic resonance imaging diagnostic of lymph nodes.

Radiomics nomogram for the preoperative prediction of lymph node metastasis in pancreatic ductal adenocarcinoma

PURPOSE

To develop and validate a radiomics nomogram for the preoperative prediction of lymph node (LN) metastasis in pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

In this retrospective study, 225 patients with surgically resected, pathologically confirmed PDAC underwent multislice computed tomography (MSCT) between January 2014 and January 2017. Radiomics features were extracted from arterial CT scans. The least absolute shrinkage and selection operator method was used to select the features. Multivariable logistic regression analysis was used to develop the predictive model, and a radiomics nomogram was built and internally validated in 45 consecutive patients with PDAC between February 2017 and December 2017. The performance of the nomogram was assessed in the training and validation cohort. Finally, the clinical usefulness of the nomogram was estimated using decision curve analysis (DCA).

RESULTS

The radiomics signature, which consisted of 13 selected features of the arterial phase, was significantly associated with LN status (p < 0.05) in both the training and validation cohorts. The multivariable logistic regression model included the radiomics signature and CT-reported LN status. The individualized prediction nomogram showed good discrimination in the training cohort [area under the curve (AUC), 0.75; 95% confidence interval (CI), 0.68-0.82] and in the validation cohort (AUC, 0.81; 95% CI, 0.69-0.94) and good calibration. DCA demonstrated that the radiomics nomogram was clinically useful.

CONCLUSIONS

The presented radiomics nomogram that incorporates the radiomics signature and CT-reported LN status is a noninvasive, preoperative prediction tool with favorable predictive accuracy for LN metastasis in patients with PDAC.

Technical Challenges in "Micro" Lymph Node Identification during Vascularized Submental Lymph Node Flap Harvesting

Background:

The outcome of autologous lymph node (LN) transfer has depended on the number of LNs in the donor site. Unknown accuracy of the LN counting method has thrown some doubts on the reliability of the previous statistics. This study aimed to assess the accuracy of naked eye (NK) and stereo microscopy (SM) as tools for LN count.

Methods:

In total, 40 vascularized submental LN flaps were harvested from 23 fresh cadavers. The colored polymer was injected into the external carotid arteries before the harvest. LNs in each flap were counted by NK, SM, and histology in sequential order.

Results:

An estimated 175 LNs were confirmed, 4.4 ± 1.8 per flap. NK sensitivity was 33.7% compared with that of SM at 63.5%. Both methods missed all micro-lymph nodes (micro-LNs), contributing to 5.1% (9 nodes) of all LNs. Non-LN structures (647 negative counts) were composed of fat lobules, salivary gland lobules, and muscle fibers. NK specificity was 98.0%, compared with that of SM at 96.1%. SM showed a higher false positive rate at 14.3%, compared with NK at 7.4%. False positive counts were located mostly in Ib sublevel.

Conclusions:

NK and SM are imperfect tools for LN count due to poor sensitivity. If the method needs to be applied, points of considerations are (1) undetectable micro-LNs, (2) interposition of LNs with the digastric muscle and submandibular salivary gland, (3) confusion of LNs with lobules of salivary gland supplied by glandular artery or fat lobules supplied by lobular artery.

Intranodal pressure of a metastatic lymph node reflects the response to lymphatic drug delivery system

Cancer metastasis to lymph nodes (LNs) almost certainly contributes to distant metastasis. Elevation of LN internal pressure (intranodal pressure, INP) during tumor proliferation is associated with a poor prognosis for patients. We have previously reported that a lymphatic drug delivery system (LDDS) allows the direct delivery of anticancer drugs into the lymphatic system and is a promising treatment strategy for early‐stage LN metastasis. However, methods for evaluating the treatment effects have not been established. Here, we used a mouse model of MXH10/Mo‐lpr/lpr, which develops a systemic swelling of LNs, and murine malignant fibrous histiocytoma‐like (KM‐Luc/GFP) cells or murine breast cancer (FM3A‐Luc) cells inoculated into the subiliac LN of mice to produce a tumor‐bearing LN model. The changes in INP during intranodal tumor progression and after treatment with cis‐dichlorodiammineplatinum(II) (CDDP) using an LDDS were measured. We found that tumor progression was associated with an increase in INP that occurred independently of LN volume changes. The elevation in INP was suppressed by CDDP treatment with the LDDS when intranodal tumor progression was significantly inhibited. These findings indicate that INP is a useful parameter for monitoring the therapeutic effect in patients with LN metastasis who have been given drugs using an LDDS, which will serve to manage cancer metastasis treatment and contribute to an improved quality of life for cancer patients.

Diffusion-weighted magnetic resonance imaging for evaluation of malignant lymph node invasion in patients with female genital neoplasms

Background / Aim: Functional imaging, including diffusion-weighted magnetic resonance imaging (DWI MRI) and ADC map, provides promising results in discrimination benign from malignant pelvic and inguinal lymph nodes in patients with gynecological malignancies. Aim of the study was to assess diagnostic performances of DWI in differentiation between benign and malignant pelvic and inguinal lymph nodes in patients with gynecological malignancies. Methods: The prospective clinical study was conducted at Clinical Center of Vojvodina from 2013 to 2016, comprising 80 patients with malignant gynecological tumors. Preoperatively, all patients underwent MRI examination, followed by standard surgical treatment with complete pelvic and/or inguinal lymphadenectomy. Histopathological examination of surgically removed material and lymph nodes separated in pelvic and inguinal anatomic groups was performed after the surgery. Results: The total of 2320 of lymph nodes were mapped and histopathologically examined in 80 patients included in the study. Metastases in lymph nodes were histopathologically confirmed in 28 patients (35%). Measured ADC values were significantly lower in metastatic (mean ? SD, ADC: 0.8725 x 10-3 mm2/s ? 0.0125) than benign lymph nodes (mean ? SD, ADC: 1.116 x 10-3 mm2/s ? 0.1848; P=0.001). If ADC value of 0.860 x 10- 3 mm2 / s is determined as a cut off value for discrimination between benign and malignant lymph nodes, DWI sensitivity was 89%, specificity 85% and overall accuracy was 86%. Combination of ADC value criteria and size-based criteria yields MRI the following diagnostic performances in discrimination between benign and malignant lymph nodes: sensitivity 95%, specificity 92%, overall accuracy 92.5%, positive predictive value 46% and negative predictive value 99.6%. Conclusion: DWI MRI sequence is fast, simple, noninvasive method which aids significantly to MRI diagnostic performances in discrimination between benign and malignant pelvic and inguinal lymph nodes.

Relationship Between Radiomics and Risk of Lymph Node Metastasis in Pancreatic Ductal Adenocarcinoma

OBJECTIVE

The objective of this study was to explore the exact relationship between the arterial radiomics score (rad-score) and lymph node (LN) metastasis in pancreatic ductal adenocarcinoma (PDAC).

METHODS

A total of 225 patients with pathologically confirmed PDAC who underwent multislice computed tomography within 1 month of resection from December 2016 to August 2017 were retrospectively studied. For each patient, 1029 radiomics features of arterial phase were extracted, which were reduced using the least absolute shrinkage and selection operator logistic regression algorithm. Multivariate logistic regression models were used to analyze the association between the arterial rad-score and LN metastasis.

RESULTS

Lymph node-negative and LN-positive patients accounted for 107 (47.56%) and 118 (52.44%) of the cohort, respectively. The rad-score, which consisted of 12 selected features of the arterial phase, was significantly associated with LN status (P < 0.05). Univariate analysis revealed that the arterial rad-score and T stage were independently and positively associated with risk of LN metastasis (P < 0.05). Multivariate analyses revealed a significant association between the arterial rad-score and the LN metastasis (P < 0.0001). Higher arterial rad-score was associated with LN metastasis (P for trend <0.0001).

CONCLUSIONS

The arterial rad-score is independently and positively associated with the risk of LN metastasis in PDAC.

The Diagnostic Value of MR Imaging in Determining the Lymph Node Status of Patients with Non-Small Cell Lung Cancer: A Meta-Analysis

Purpose To summarize existing evidence of thoracic magnetic resonance (MR) imaging in determining the nodal status of non-small cell lung cancer (NSCLC) with the aim of elucidating its diagnostic value on a per-patient basis (eg, in treatment decision making) and a per-node basis (eg, in target volume delineation for radiation therapy), with results of cytologic and/or histologic examination as the reference standard. Materials and Methods A systematic literature search for original diagnostic studies was performed in PubMed, Web of Science, Embase, and MEDLINE. The methodologic quality of each study was evaluated by using the Quality Assessment of Diagnostic Accuracy Studies 2, or QUADAS-2, tool. Hierarchic summary receiver operating characteristic curves were generated to estimate the diagnostic performance of MR imaging. Subgroup analyses, expressed as relative diagnostic odds ratios (DORs) (rDORs), were performed to evaluate whether publication year, methodologic quality, and/or method of evaluation (qualitative [ie, lesion size and/or morphology] vs quantitative [eg, apparent diffusion coefficients in diffusion-weighted images]) affected diagnostic performance. Results Twelve of 2551 initially identified studies were included in this meta-analysis (1122 patients; 4302 lymph nodes). On a per-patient basis, the pooled estimates of MR imaging for sensitivity, specificity, and DOR were 0.87 (95% confidence interval [CI]: 0.78, 0.92), 0.88 (95% CI: 0.77, 0.94), and 48.1 (95% CI: 23.4, 98.9), respectively. On a per-node basis, the respective measures were 0.88 (95% CI: 0.78, 0.94), 0.95 (95% CI: 0.87, 0.98), and 129.5 (95% CI: 49.3, 340.0). Subgroup analyses suggested greater diagnostic performance of quantitative evaluation on both a per-patient and per-node basis (rDOR = 2.76 [95% CI: 0.83, 9.10], P = .09 and rDOR = 7.25 [95% CI: 1.75, 30.09], P = .01, respectively). Conclusion This meta-analysis demonstrated high diagnostic performance of MR imaging in staging hilar and mediastinal lymph nodes in NSCLC on both a per-patient and per-node basis. (©) RSNA, 2016 Online supplemental material is available for this article.

Label-free Detection of Lymph Node Metastases with US-guided Functional Photoacoustic Imaging

PURPOSE

To determine the ability of ultrasonography (US)-guided spectroscopic photoacoustic (sPA) imaging to depict changes in blood oxygen saturation (SO2) in metastatic lymph nodes of a mouse model of oral cancer.

MATERIALS AND METHODS

All studies were performed by following protocols approved by the institutional animal care and use committee at the University of Texas at Austin. Coregistered US and photoacoustic images were acquired spanning volumes containing a total of 31 lymph nodes in 17 female nu/nu mice. The mice were either healthy (three mice, five nodes) or bearing a primary tumor consisting of luciferase-labeled FaDu cells (14 mice, 26 nodes). Ten photoacoustic images acquired with optical wavelengths spanning from 680 to 860 nm were spectrally unmixed by using a linear least-squares method to obtain sPA images. After imaging, histologic analysis enabled confirmation of the presence of micrometastases. Generalized estimating equations were used to compare metastatic and normal lymph nodes, with a P value of .05 taken to indicate a significant difference. Sensitivity and specificity were determined with a receiver operator characteristic curve constructed from the background-subtracted SO2 values.

RESULTS

Metastatic lymph nodes (n = 7) exhibited a significantly (P = .018) lower spatially averaged background-subtracted SO2 (mean, 5.4% ± 3.5 [standard error]) when compared with lymph nodes without metastases (mean, 13.7% ± 1.3; n = 24). This effect was observed throughout the entire volume of the nodes rather than being limited to the metastatic foci. The change in SO2, which was inversely related to the size of the metastasis, was detectable in metastases as small as 2.6 × 10(-3) mm(3).

CONCLUSION

The results show that US-guided sPA imaging is capable of depicting changes in SO2 in lymph nodes that were correlated with metastatic invasion.

Sentinel lymph node biopsy revisited: ultrasound-guided photoacoustic detection of micrometastases using molecularly targeted plasmonic nanosensors

Metastases rather than primary tumors are responsible for killing most patients with cancer. Cancer cells often invade regional lymph nodes (LN) before colonizing other parts of the body. However, due to the low sensitivity and specificity of current imaging methods to detect localized nodal spread, an invasive surgical procedure--sentinel LN biopsy--is generally used to identify metastatic cancer cells. Here, we introduce a new approach for more sensitive in vivo detection of LN micrometastases, based on the use of ultrasound-guided spectroscopic photoacoustic (sPA) imaging of molecularly activated plasmonic nanosensors (MAPS). Using a metastatic murine model of oral squamous cell carcinoma, we showed that MAPS targeted to the epidermal growth factor receptor shifted their optical absorption spectrum to the red-near-infrared region after specific interactions with nodal metastatic cells, enabling their noninvasive detection by sPA. Notably, LN metastases as small as 50 μm were detected at centimeter-depth range with high sensitivity and specificity. Large sPA signals appeared in metastatic LN within 30 minutes of MAPS injection, in support of the clinical utility of this method. Our findings offer a rapid and effective tool to noninvasively identify micrometastases as an alternate to sentinal node biopsy analysis.

Assessment of cervical lymph node metastases using indirect computed tomography lymphography with iopamidol in a tongue VX2 carcinoma model

OBJECTIVE

To investigate the performance of indirect computed tomography lymphography with iopamidol for detecting cervical lymph node metastases in a tongue VX2 carcinoma model.

MATERIALS AND METHODS

A metastatic cervical lymph node model was created by implanting VX2 carcinoma suspension into the tongue submucosa of 21 rabbits. Computed tomography images were obtained 1, 3, 5, 10, 15 and 20 minutes after iopamidol injection, on days 11, 14, 21 (six rabbits each) and 28 (three rabbits) after carcinoma transplantation. Computed tomography lymphography was performed, and lymph node filling defects and enhancement characteristics evaluated.

RESULTS

Indirect computed tomography lymphography revealed bilateral enhancement of cervical lymph nodes in all animals, except for one animal imaged on day 28. There was significantly slower evacuation of contrast in metastatic than non-metastatic nodes. A total of 41 enhanced lymph nodes displayed an oval or round shape, or local filling defects. One lymph node with an oval shape was metastatic (one of 11, 9.1 per cent), while 21 nodes with filling defects were metastatic (21/30, 70 per cent). The sensitivity, specificity, accuracy, and positive and negative predictive values when using a filling defect diameter of 1.5 mm as a diagnostic criterion were 86.4, 78.9, 82.9, 82.6 and 83.3 per cent, respectively.

CONCLUSION

When using indirect computed tomography lymphography to detect metastatic lymph nodes, filling defects and slow evacuation of contrast agent are important diagnostic features.

Preoperative assessment of para-aortic lymph node metastasis in patients with pancreatic cancer

BACKGROUND

Para-aortic lymph node (PALN) metastasis is an important prognostic factor in patients with pancreatic cancer, but accurate preoperative diagnosis is difficult. The objective of this study was to assess the accuracy of diagnosis of PALN by computed tomography (CT), magnetic resonance imaging (MRI), and (18)F-fluorodeoxyglucose positron-emission tomography (FDG-PET).

METHODS

From August 2005 to July 2008, 119 patients with invasive ductal adenocarcinoma of the pancreas were included in this study. PALNs with a longer diameter >10 mm on CT or MRI were suspected of being involved by metastasis, whereas FDG uptake exceeding that of the adjacent normal tissue was considered to be positive for metastasis on FDG-PET studies. The imaging findings were compared with the pathological diagnosis of PALN metastasis.

RESULTS

PALN dissection was performed in 71 patients (60.0%). Although histopathological examination revealed metastasis in 6 patients (8.5%), none of these patients was positive in any of the preoperative imaging studies. The longer diameter, the shorter diameter, the ratio of the two diameters, and the calculated lymph node volume showed no significant differences between patients with and without PALN metastasis.

CONCLUSIONS

Preoperative detection of PALN metastasis in patients with pancreatic cancer is very difficult. Intraoperative histopathological examination of frozen sections is necessary if radical resection is contemplated.