Korean J Radiol.  2007 Feb;8(1):9-14. 10.3348/kjr.2007.8.1.9.

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

• Lee KC
• Moon WK
• Chung JW
• Choi SH
• Cho N
• Cha JH
• Lee EH
• Kim SM
• Kim HS
• Han MH
• Chang KH

• KMID: 753860
• DOI: http://doi.org/10.3348/kjr.2007.8.1.9

Abstract

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.

Keyword

Lymphatic system, diseases; Magnetic resonance (MR), contrast media; Head and neck neoplasms, MR; Experimental study

MeSH Terms

Sensitivity and Specificity
Retrospective Studies
Rabbits
ROC Curve
Predictive Value of Tests
Magnetic Resonance Imaging/*methods
Lymphatic Metastasis/*pathology
Head and Neck Neoplasms/*pathology
Gadolinium DTPA/diagnostic use
Disease Models, Animal
Contrast Media
Animals

Figure

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  Fig. 1 The coronal T1-(A) and T2-weighted (B) MR images obtained before injecting gadopentetate dimeglumine show enlarged parotid lymph nodes (arrow). The coronal T1-weighted MR images obtained before (C) and after (D) injecting gadopentetate dimeglumine 3 weeks after tumor cell inoculation show enlarged parotid lymph nodes (arrow) with rim enhancement. The photomicrograph (E) shows a metastatic parotid lymph node with central necrosis (H & E stain; original magnification, ×2).

• 

  Fig. 2 The coronal T1-(A) and T2-weighted (B) MR images obtained before injecting gadopentetate dimeglumine show enlarged parotid lymph nodes (arrow). The coronal T1-weighted MR images obtained before (C) and after (D) injecting gadopentetate dimeglumine at three weeks after tumor cell inoculation show enlarged parotid lymph nodes (arrow) with homogenous enhancement. The photomicrograph (E) shows a hyperplastic parotid lymph node (H & E stain; original magnification, ×2).

• 

  Fig. 3 A. Graph showing the size distribution of the metastatic and hyperplastic lymph nodes in rabbits. The metastatic lymph nodes were larger (10.5±3.2 mm) than the hyperplastic nodes (8.0±3.6 mm), however, the difference was not statistically significant (p > 0.05). B. Graph showing the signal intensity ratio of the metastatic and hyperplastic lymph nodes in rabbits with respect to the node size. The signal intensity ratio of the metastatic lymph nodes (0.82±0.16) was significantly lower than that of the hyperplastic lymph nodes (2.02±0.86) (p < 0.05). The size of the diseased lymph node and the signal intensity ratio was not found to be correlated (p > 0.05).

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  Fig. 4 Graph showing the receiver operating characteristic curves of size and signal intensity ratio for the detection of metastatic lymph nodes. The Az values were 0.81 for the signal intensity ratio and 0.72 for size as determined from the MR images, which were significantly different (p < 0.05). CI = confidence interval

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