Modern imaging lymph node staging of the head and neck region

The aim of this paper is to describe the modern imaging methods, their techniques, ability, and performance in staging head and neck lymph nodes. Also, the imaging morphologies of benign and malignant lymph nodes according to the different imaging techniques will be delineated. The imaging techniques of ultrasound including contrast-enhanced ultrasound, computed tomography and magnetic resonance imaging (MRI) including diffusing weighted imaging and contrast-enhanced iron oxide MRI are explained. Imaging examples of the different modalities of benign and malignant transformed lymph nodes will be demonstrated. Furthermore, the diagnostic sensitivity of each modality will be delineated and further aspects of modern lymph node staging of the head and neck region such as those with special contrast agents will be described. These modern imaging modalities have sensitivity rates of 70-80% depending on the technical equipment and ability and on the experience of the investigator. The technique of near-infrared-imaging will be mentioned in another article in this journal. Also the value of biopsy techniques including recently developed ultrasonography guided needle biopsy with molecular analysis of the cells of about 97-100% accuracy in diagnosing benign from malignant lymph nodes will be mentioned. Overall, the reader will get an overview of the present imaging modalities to potentially stage correctly lymph nodes in the head and neck region to facilitate the therapeutic procedure.     

Ultrasmall superparamagnetic iron oxide enhanced MR imaging for lymph node metastases

The presence of a lymph node metastasis is one of the most important factors influencing therapeutic planning and prognosis in patients with malignancy. For example, a single nodal metastasis approximately halves the survival rate in patients with head and neck cancer, regardless of the location or size of the primary tumor. Currently used imaging techniques such as CT or conventional MRI are unreliable in detecting involved nodes accurately. There are few new techniques that have proven to be of value in nodal staging, and one such technique is ultrasmall superparamagnetic iron oxide (USPIO) contrast agents for MRI. Administered intravenously, USPIO are phagocytosed by macrophages within lymph nodes. Homogeneous uptake of iron oxide particles in normal lymph node shortens the T2 and T2*, turning these nodes dark on post contrast images whereas malignant nodes, lacking the normal physiologic uptake, remain hyperintense on T2- and T2*-weighted images. These differences in signal intensity between normal and metastatic nodes are easily detected visually, leading to high sensitivity and specificity regardless of size or morphological features.This article will review the physiologic properties of USPIO, the technical considerations for imaging using USPIO agent, the results of various clinical trials, and other experimental agents, as well asthe future directions.     

Iron oxide-enhanced MR lymphography: The evaluation of cervical lymph node metastases in head and neck cancer

Accurate diagnosis of cervical lymph node metastasis is challenging, even with the latest computed tomography or MR equipment and technique. The lack of definitive criteria for distinguishing metastatic from benign nodes is a serious shortcoming of current imaging options. Dextran-coated, ultrasmall superparamagnetic iron oxide is a new MR contrast agent, which accumulates in the reticuloendothelial system of lymph nodes. Small iron oxide particles are taken up by macrophages within normal functioning nodes, reducing their signal on postcontrast MR because of the magnetic susceptibility effects of iron oxide. Metastatic nodes, on the other hand, remain high in signal on postcontrast T2*-weighted gradient echo images. Early clinical experience in cancer patients suggests that iron oxide-enhanced MR lymphography is a valuable imaging technique that may improve diagnostic accuracy for nodal metastases. This article reviews development of superparamagnetic iron oxide compounds, their imaging characteristics, and clinical experience for evaluating head and neck cancer metastases.     

MR lymphangiography using ultrasmall superparamagnetic iron oxide in patients with primary abdominal and pelvic malignancies: radiographic-pathologic correlation

OBJECTIVE: The purpose of this study was to administer ultrasmall superparamagnetic iron oxide (USPIO) and compare changes in signal intensity of lymph nodes in patients with primary abdominal and pelvic malignancies. Also, we correlated radiographic with pathologic findings. SUBJECTS AND METHODS: Nineteen patients with proven primary abdominal or pelvic cancer (prostatic [n = 10]; colonic [n = 5]; endometrial [n = 1]; Merkel cell tumor [n = 1]; lymphoma [n = 1]; seminoma [n = 1]) were enrolled as part of our phase II and phase III clinical trials. In these patients, 49 lymph nodes (mean size, 1.4 cm) revealed on CT or MR imaging were evaluated on T1-weighted spin-echo, T2-weighted fast spin-echo, and T2*-weighted gradient-echo MR imaging at 1.5 T 24-36 hr after IV administration of USPIO. Quantitative analyses used measurements of unenhanced and enhanced region-of-interest values in lymph nodes. Qualitative assessment used subjective evaluation and classification of changes in signal intensity. All patients underwent lymph node biopsy or surgical dissection followed by histopathologic correlation. RESULTS: Of the 49 lymph nodes that were evaluated, 20 were benign and 29 were malignant. A decrease in nodal signal intensity on enhanced T2-weighted and T2*-weighted gradient-echo images was seen in 20 benign lymph nodes and two malignant lymph nodes. No appreciable signal change was noted in 27 of the 29 malignant lymph nodes. The mean signal intensity on fast spin-echo T2-weighted images for benign lymph nodes changed from 186.48 (unenhanced) to 73.66 (enhanced). Conversely, mean signal intensity for malignant lymph nodes was relatively unchanged from 191.17 (unenhanced) to 183.18 (enhanced). CONCLUSION: USPIO appears to be a useful MR contrast agent for characterizing benign and malignant lymph nodes based on the enhancement criteria evaluated in our study.     

Morphologic predictors of lymph node status in rectal cancer with use of high-spatial-resolution MR imaging with histopathologic comparison

PURPOSE: To evaluate signal intensity and border characteristics of lymph nodes at high-spatial-resolution magnetic resonance (MR) imaging in patients with rectal cancer and to compare these findings with size in prediction of nodal status. MATERIALS AND METHODS: Forty-two patients who underwent total mesorectal excision of the rectum to determine if they had rectal carcinoma were studied with preoperative thin-section MR imaging. Lymph nodes were harvested from 42 transversely sectioned surgical specimens. The slice of each lymph node was carefully matched with its location on the corresponding MR images. Nodal size, border contour, and signal intensity on MR images were characterized and related to histologic involvement with metastases. Differences in sensitivity and specificity with border or signal intensity were calculated with CIs by using method 10 of Newcombe. RESULTS: Of the 437 nodes harvested, 102 were too small (<3 mm) to be depicted on MR images, and only two of these contained metastases. In 15 (68%) of 22 patients with nodal metastases, the size of normal or reactive nodes was equal to or greater than that of positive nodes in the same specimen. Fifty-one nodes were above the area imaged, and seven of these contained metastases. The diameter of benign and malignant nodes was similar; therefore, size was a poor predictor of nodal status. If a node was defined as suspicious because of an irregular border or mixed signal intensity, a superior accuracy was obtained and resulted in a sensitivity of 51 (85%) of 60 (95% CI: 74%, 92%) and a specificity of 216 (97%) of 221 (95% CI: 95%, 99%). CONCLUSION: Prediction of nodal involvement in rectal cancer with MR imaging is improved by using the border contour and signal intensity characteristics of lymph nodes instead of size criteria.     

MR contrast agents in lymph node imaging

The detection of tumor metastases in lymph nodes is clinically important for tumor staging and therapy planning in cancer patients. However, differentiating between malignant and benign lymph nodes is still a problem because current imaging modalities rely only on the size and shape of the lymph nodes. Thus, small metastases in normal-sized lymph nodes can be missed, and it is difficult to differentiate enlarged nodes (benign hyperplasia versus malignant disease). Therefore, a specific lymphotropic contrast agent is needed to obtain a high contrast between functional and metastatic tissue. Contrast-enhanced MR lymphography is a noninvasive method for the analysis of the lymphatic system after interstitial (intracutaneous or subcutaneous) or intravenous application of contrast media. Interstitial MR lymphography using extracellular, liposomal, polymeric, lipophilic or particulate contrast agents results in high accumulation in regional lymph nodes. The systemic administration of a lymphotropic contrast medium is needed to address each individual lymph node. Ultrasmall superparamagnetic iron oxide particles are in late-stage clinical development for this indication, but they take 24h to show sufficient contrast. Recently, a gadolinium-type contrast agent (Gadofluorine M) was described that detected lymph node metastases within 60 min of intravenous injection.     

背景抑制扩散加权成像诊断头颈部鳞癌颈部淋巴结转移的价值

目的 前瞻性地探讨背景抑制扩散加权成像(DWIBS)评价头颈部鳞癌颈部淋巴结转移的临床应用价值.方法 对20例经颈部淋巴结活检或手术病理证实的头颈部鳞癌患者(舌癌5例、鼻咽癌5例、喉癌3例、口底癌3例、口咽癌1例、喉咽癌1例、面颊癌1例和唇癌1例)进行颈部常规MR和DWIBS扫描,测量淋巴结的ADC值,选定鉴别转移性和良性淋巴结的最佳ADC阈值,并比较DWIBS与常规MRI显示和诊断转移性淋巴结的能力.两组均数间的比较采用独立样本t检验.结果 常规MR检查计数淋巴结共101枚,诊断转移性淋巴结58枚;常规MRI诊断淋巴结转移的敏感度为78%(47/60)、特异度为81%(44/54)、准确度为80%(91/114)、阳性预测值为82%(47/57)、阴性预测值为77%(44/57).DWIBS计数淋巴结共114枚,转移性淋巴结(60枚)的平均ADC值为(0.945±0.122)×10-3mm2/s,低于良性淋巴结(54枚)的平均ADC值(1.210±0.151)×10-3 mm2/s(t=-10.354,P＜0.01).以1.090×10-3 mm2/s作为ADC阈值,诊断颈部淋巴结转移的敏感度、特异度、准确度、阳性和阴性预测值分别为88%(53/60)、80%(43/54)、84%(96/114)、83%(53/64)和86%(43/50).结论 DWIBS有助于诊断头颈部鳞癌的颈部淋巴结转移,较常规MRI可提高其检出率.     

Superparamagnetic iron oxide-enhanced MR imaging of head and neck lymph nodes.

PURPOSE: To compare findings on superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) images of the head and neck with those from resected lymph node specimens and to determine the effect of such imaging on surgical planning in patients with histopathologically proved squamous cell carcinoma of the head and neck. MATERIALS AND METHODS: Thirty patients underwent MR imaging with nonenhanced and SPIO-enhanced (2.6 mg Fe/kg intravenously) T1-weighted (500/15 [repetition time msec/echo time msec]) and T2-weighted (1,900/80) spin-echo and T2-weighted gradient-echo (GRE) (500/15, 15 degrees flip angle) sequences. Signal intensity decrease was measured, and visual analysis was performed. Surgical plans were modified, if necessary, according to MR findings. Histopathologic and MR findings were compared. RESULTS: Histopathologic evaluation of 1,029 lymph nodes revealed 69 were metastatic. MR imaging enabled detection of 59 metastases. Regarding lymph node levels, MR diagnosis was correct in 26 of 27 patients who underwent surgery: Only one metastasis was localized in level II with MR imaging, whereas histopathologic evaluation placed it at level III. Extent of surgery was changed in seven patients. SPIO-enhanced T2-weighted GRE was the best sequence for differentiating between benign and malignant lymph nodes. CONCLUSION: SPIO-enhanced MR imaging has an important effect on planning the extent of surgery. On a patient basis, SPIO-enhanced MR images compared well with resected specimens.     

Lymph node metastases: CT and MRI

Imaging is playing a major role in the assessment of cervical lymphadenopathy. In head and neck malignancies, imaging can be helpful for staging, and sometimes in differentiating different types of metastases, such as squamous cell carcinomas, non-hodgkins disease and thyroid carcinomas. This article on imaging of cervical lymph node metastases will describe both radiological and clinical aspects. Computed tomography (CT) and magnetic resonance (MR) are widely used for primary tumor and nodal imaging. However, very seldom these modalities have clinical consequences for the management of the neck, such as a wait-and-see policy if no nodes are depicted. This is caused by the limited accuracy of both modalities caused by the fallibility of radiologic criteria for metastases. Ultrasound (US) is hampered by similar morphologic criteria, and only US-guided fine needle aspiration cytology (FNAC) can offer additional cytologic criteria which are more reliable.     

Urinary bladder cancer: preoperative nodal staging with ferumoxtran-10-enhanced MR imaging

PURPOSE: To prospectively evaluate ferumoxtran-10-enhanced magnetic resonance (MR) imaging for nodal staging in patients with urinary bladder cancer. MATERIALS AND METHODS: Fifty-eight patients with proved bladder cancer were enrolled. Results of MR imaging performed before and after injection of ferumoxtran-10 were compared with histopathologic results in surgically removed lymph nodes. High-spatial-resolution three-dimensional T1-weighted magnetization-prepared rapid acquisition gradient-echo (voxel size, 1.4 x 1.4 x 1.4 mm) and T2*-weighted gradient-echo (voxel size, 0.8 x 0.8 x 3.0 mm) sequences were performed before and 24 hours after injection of ferumoxtran-10 (2.6 mg iron per kilogram of body weight). On precontrast images, lymph nodes were defined as malignant by using size and shape criteria (round node, >8 mm; oval, >10 mm axial diameter). On postcontrast images, nodes were considered benign if there was homogeneous decrease in signal intensity and malignant if decrease was absent or heterogeneous. Qualitative evaluation was performed on a node-to-node basis. Sensitivity, specificity, predictive values, and accuracy were evaluated with logistic regression analysis. RESULTS: In 58 patients, 172 nodes imaged with use of ferumoxtran-10 were matched and correlated with results of node dissection. Of these, 122 were benign and 50 were malignant. With nodal size and shape criteria, accuracy, sensitivity, specificity, and positive and negative predictive values on precontrast images were 92%, 76%, 99%, 97%, and 91%, respectively; corresponding values on postcontrast images were 95%, 96%, 95%, 89%, and 98%. In the depiction of pelvic metastases, sensitivity and negative predictive value improved significantly at postcontrast compared with those at precontrast imaging, from 76% to 96% (P < .001) and from 91% to 98% (P < .01), respectively. At postcontrast imaging, metastases (4-9 mm) were prospectively found in 10 of 12 normal-sized nodes (<10 mm); these metastases were not detected on precontrast images. Postcontrast images also showed lymph nodes that were missed at pelvic node dissection in two patients. CONCLUSION: Ferumoxtran-10-enhanced MR imaging significantly improves nodal staging in patients with bladder cancer by depicting metastases even in normal-sized lymph nodes.     

Nodal imaging in the neck: recent advances in US,CT and MR imaging of metastatic nodes

The presence of lymph node metastasis in the neck in patients with head and neck cancer is an important prognostic determinant in staging cancers and in planning surgery and chemo- and radiotherapy for the cancer patients. Therefore, metastatic nodes should be effectively differentiated from benign lymphadenopathies and nodal lymphomas. Here, we review recent advances in the diagnostic imaging of metastatic nodes in the neck, with emphasis placed on the diagnostic performance of MR imaging, Doppler sonography, and CT.     

Effectiveness of the STIR turbo spin–echo sequence MR imaging in evaluation of lymphadenopathy in esophageal cancer

Purpose

We have investigated the utility of the STIR TSE sequence in the differentiation of benign from malignant mediastinal lymph nodes in patients with esophageal cancer.

Patients and methods

This study included 35 consecutive patients who were diagnosed as esophageal cancer and were undergone surgery. STIR TSE sequences were obtained as the ECG trigger. The signal intensity of the benign and malign lymph nodes, normal esophagus, and pathologic esophagus can be calculated on STIR sequence.

Results

Pathologically, the number of total lymph nodes in 35 operated cases was 482. Approximately 152 lymph nodes were detected with MR imaging. Of these, 28 were thought to be malignant, and 124 were thought to be benign, although 32 were malignant and 120 were benign according pathological results. The ratio of benign lymph node intensity value to normal esophagus intensity value was 0.73 ± 0.3. The ratio of malignant lymph node intensity value to normal esophagus intensity value ratio was 2.03 ± 0.4. According to these results, the sensitivity of MR was 81.3%, the specificity was 98.3%.

Conclusion

We think that if motionless images can be obtained with MRI, we may be able to differentiate benign lymph nodes from malignant ones.     

Lymph node staging with dual-modality PET/CT: enhancing the diagnostic accuracy in oncology

Lymph node staging according to the TNM criteria is an essential part of tumor evaluation. Several morphological and functional imaging procedures are used complementarily in this setting. Dual-modality PET/CT scanners are able to provide anatomical and functional data sets in a single session with accurate image co-registration. Comparative studies between morphological imaging procedures, such as MRI and CT, with co-registered PET/CT demonstrated significantly better lymph node staging with PET/CT than with anatomical procedures alone, regardless of the staged body compartment (head and neck, thorax or abdominal area). Based on more accurate staging results, PET/CT was able to alter the patients' therapy in a significant number of studies. Functional imaging with FDG-PET ([(18)F]-2-fluoro-2-desoxy-D-glucose-positron emission tomography) demonstrated outstanding results in lymph node staging of different tumor diseases. By adding anatomical information to PET, PET/CT outperforms PET alone when assessing the TNM-stage of different malignant diseases. This paper provides an overview concerning the performance of PET/CT in staging lymph nodes for malignant spread and points out benefits and limitations of this new imaging modality.     

MR microimaging of benign and malignant nodes in the neck

OBJECTIVE: We evaluated the diagnostic criteria of high-resolution MRI in differentiating benign and malignant cervical nodes that were palpable and superficial in the neck. SUBJECTS AND METHODS: We performed MR microimaging on 24 histologically proven metastatic nodes, 14 histologically proven lymphomas, and 35 histologically or clinically proven benign nodes in the necks of 26 patients. The lymph nodes were imaged with T1-weighted spin-echo, fat-suppressed T2-weighted turbo spin-echo, and spin-echo diffusion-weighted echo-planar sequences using a 47-mm microscopy coil. RESULTS: MR microimaging provided high-resolution images of the nodes. Hilar fat was lost in 92%, 79%, and 46% of the metastatic nodes, lymphomas, and benign nodes, respectively. Smooth nodal margins were lost in 58%, 23%, and 9% of metastatic nodes, lymphomas, and benign nodes, respectively. Heterogeneous nodal parenchyma on T1- or fat-suppressed T2-weighted images, or both, was observed in 88%, 29%, and 23% of metastatic nodes, lymphomas, and benign nodes, respectively. The apparent diffusion coefficients were significantly different among these three node groups (p < 0.001), with metastatic nodes being the highest, followed by benign nodes. Logistic regression analyses showed that heterogeneous nodal parenchyma and apparent diffusion coefficient levels were significant in discriminating metastatic nodes, and apparent diffusion coefficient levels in discriminating lymphomas. Combined use of these MR microscopic criteria on nodal architecture and apparent diffusion coefficients yielded 90% accuracy (86% sensitivity, 94% specificity) and 93% accuracy (85% sensitivity, 95% specificity) for discriminating metastatic nodes and lymphomas, respectively. CONCLUSION: The nodal architecture and apparent diffusion coefficient levels on MR microimaging may provide useful information in diagnosing benign and malignant nodes in the neck.     

A computer-aided algorithm to quantitatively predict lymph node status on MRI in rectal cancer

Objective The aim of this study was to demonstrate the principle of supporting radiologists by using a computer algorithm to quantitatively analyse MRI morphological features used by radiologists to predict the presence or absence of metastatic disease in local lymph nodes in rectal cancer. Methods A computer algorithm was developed to extract and quantify the following morphological features from MR images: chemical shift artefact; relative mean signal intensity; signal heterogeneity; and nodal size (volume or maximum diameter). Computed predictions on nodal involvement were generated using quantified features in isolation or in combinations. Accuracies of the predictions were assessed against a set of 43 lymph nodes, determined by radiologists as benign (20 nodes) or malignant (23 nodes). Results Predictions using combinations of quantified features were more accurate than predictions using individual features (0.67-0.86 vs 0.58-0.77, respectively). The algorithm was more accurate when three-dimensional images were used (0.58-0.86) than when only middle image slices (two-dimensional) were used (0.47-0.72). Maximum node diameter was more accurate than node volume in representing the nodal size feature; combinations including maximum node diameter gave accuracies up to 0.91. Conclusion We have developed a computer algorithm that can support radiologists by quantitatively analysing morphological features of lymph nodes on MRI in the context of rectal cancer nodal staging. We have shown that this algorithm can combine these quantitative indices to generate computed predictions of nodal status which closely match radiological assessment. This study provides support for the feasibility of computer-assisted reading in nodal staging, but requires further refinement and validation with larger data sets.     

SPIO粒子增强MRI检测腋窝转移性淋巴结的实验研究

目的:探讨超顺磁性氧化铁粒子(SPIO)增强MRI检测腋窝转移性淋巴结的价值.方法:选取健康成年新西兰白兔14只,采用随机数字法将其分为反应性增生淋巴结组(8只)及肿瘤转移淋巴结组(6只).MRI平扫后,3只反应性增生淋巴结皮下间隙注射SPIO(10 μmol Fe/单侧乳腺)后第1、3、6、12、24和48 h点扫描...     

Comparison of dynamic helical CT and dynamic MR imaging in the evaluation of pelvic lymph nodes in cervical carcinoma

OBJECTIVE: This study compares dynamic helical CT with dynamic MR imaging in the evaluation of pelvic lymph nodes in cervical carcinoma. SUBJECTS AND METHODS: Women with biopsy-proven cervical carcinoma prospectively underwent dynamic helical CT and MR imaging before surgery. A metastatic node on CT and MR imaging was defined as a rounded soft-tissue structure greater than 10 mm in maximal axial diameter or a node with central necrosis. Imaging results were compared with pathology, and receiver operating characteristic curves for size and shape were plotted on a hemipelvis basis. Nodal density and signal intensity on CT and MR images, respectively, were reviewed for differences between benign and malignant disease. RESULTS: A total of 949 lymph nodes were found at pathology in 76 hemipelves in 43 women, of which 69 lymph nodes (7%) in 17 hemipelves (22%) were metastatic. Sensitivity, specificity, positive and negative predictive values, and accuracy of helical CT and MR imaging in the diagnosis of lymph node metastasis on a hemipelvis basis was 64.7%, 96.6%, 84.6%, 90.5%, and 89.5% and 70.6%, 89.8%, 66. 7%, 91.4%, and 85.5%, respectively. Receiver operating characteristic curves for helical CT and MR imaging gave cutoff values of 9 and 12 mm in maximal axial diameter, respectively, in the prediction of metastasis. Central necrosis had a positive predictive value of 100% in the diagnosis of metastasis. Signal intensity on MR imaging and density-enhancement pattern on CT in patients with metastatic nodes did not differ from those in patients with negative nodes. CONCLUSION: Helical CT and MR imaging show similar accuracy in the evaluation of pelvic lymph nodes in patients with cervical carcinoma. Central necrosis is useful in the diagnosis of metastasis in pelvic lymph nodes in cervical cancer.     

3.0T MR多b值DWI对鼻咽癌患者颈部良恶性淋巴结的鉴别诊断价值

目的探讨3.0T磁共振多b值扩散加权成像(DWI)对鼻咽癌患者颈部良恶性淋巴结的鉴别和诊断价值。方法收集本院66例鼻咽癌患者的临床资料,并以35例良性淋巴结肿大患者为对照。所有患者均行MR常规平扫、增强和多b值DWI影像学检查,比较不同b值下鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结与良性淋巴结肿大患者表观扩散系数(ADC)值的差异。通过绘制受试者工作特征(ROC)曲线计算诊断阈值、ROC曲线下面积、敏感度和特异度,评价不同b值下ADC值对鼻咽癌颈部良恶性淋巴结的鉴别和诊断价值。结果随着b值的增加,鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结与良性淋巴结肿大患者ADC值呈现减少的趋势;鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结之间ADC值的比较,差异均无统计学意义(P>0.05);鼻咽癌患者原发灶、颈部转移性小淋巴结、转移性大淋巴结ADC值均显著低于良性淋巴结肿大患者(P<0.05)。在b值分别取400、600、800、1000s/mm^2时,其对应的ROC曲线下面积分别为0.77、0.82、0.91、0.87。当b=800s/mm^2时,其鉴别和诊断淋巴结良恶性的价值最高,此时ADC值诊断鼻咽癌颈部转移性小淋巴结的阈值为0.945×10^-3mm^2/s,诊断敏感度为98.49%,特异度为79.63%,约登指数为0.78。结论3.0T MR多b值DWI检查可有效区分良恶性淋巴结的性质,并且在b值为800s/mm^2时,其鉴别和诊断不同淋巴结性质的能力最强,可用于临床鉴别和诊断鼻咽癌患者颈部淋巴结转移瘤。     

Assessment of Lymph Node Metastases by Contrast-Enhanced MR Imaging in a Head and Neck Cancer Model

Objective

We wanted to investigate the accuracy of contrast-enhanced MR imaging for the detection of lymph node metastases in a head and neck cancer rabbit model.

Materials and Methods

The metastatic lymph node model we used was created by inoculating VX2 tumors into the auricles of six New Zealand White rabbits. T1-weighted MR images were obtained before and after injecting gadopentetate dimeglumine at three weeks after tumor cell inoculation. The sizes, signal intensity ratios (i.e., the postcontrast signal intensities of the affected nodes relative to the adjacent muscle) and the enhancement patterns of 36 regional lymph nodes (parotid and caudal mandibular nodes) were evaluated on MR images and then compared with the histopathologic findings.

Results

No statistical difference was found between the sizes of 12 metastatic (10.5±3.2 mm) and 24 hyperplastic (8.0±3.6 mm) lymph nodes (p > 0.05). On the contrast-enhanced T1-weighted MR images, nine metastatic and four hyperplastic lymph nodes had peripheral high and central low signal intensity, whereas three metastatic and 20 hyperplastic lymph nodes had homogeneous high signal intensity. Using a signal intensity ratio less than one as a diagnostic criterion for a metastatic lymph node, the sensitivity, specificity and positive and negative predictive values of the enhanced MR images were 75% (9/12), 83% (20/24), 69% (9/13) and 87% (20/23), respectively, with areas under receiver-operating-characteristic curve values of 0.81.

Conclusion

This experimental study confirms that metastatic and hyperplastic lymph nodes can be differentiated using MR images on the basis of the contrast uptake patterns, but that they cannot be differentiated using any particular size criteria.     

Diffusion-weighted MR imaging in the head and neck

Extracranial applications of diffusion-weighted (DW) magnetic resonance (MR) imaging are gaining increasing importance, including in head and neck radiology. The main indications for performing DW imaging in this relatively small but challenging region of the body are tissue characterization, nodal staging, therapy monitoring, and early detection of treatment failure by differentiating recurrence from posttherapeutic changes. Lower apparent diffusion coefficients (ADCs) have been reported in the head and neck region of adults and children for most malignant lesions, as compared with ADCs of benign lesions. For nodal staging, DW imaging has shown promise in helping detect lymph node metastases, even in small (subcentimeter) nodes with lower ADCs, as compared with normal or reactive nodes. Follow-up of early response to treatment is reflected in an ADC increase in the primary tumor and nodal metastases; whereas nonresponding lesions tend to reveal only a slight increase or even a decrease in ADC during follow-up. Optimization and standardization of DW imaging technical parameters, comparison of DW images with morphologic images, and increasing experience, however, are prerequisites for successful application of this challenging technique in the evaluation of various head and neck pathologic conditions.