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Diagnostic accuracy of 99mTc-MIBI-SPECT in the detection of lymph node metastases in patients with carcinoma of the tongue: comparison with computed tomography and MRI

Aim To compare the diagnostic efficacy of computerized tomography (CT), magnetic resonance imaging (MRI), and 99mTc-methoxyisobutylisonitrile-single photon emission computed tomography (MIBI-SPECT) for the detection of lymph node (LN) metastases in clinically neck-negative patients (T1-T2N0) with carcinoma of the tongue. Materials and methods Twenty adult patients (aged 54.75±14.57 years) with histopathologically proven carcinoma of the tongue and clinically neck-negative (T1-T2N0) status were included in this study. Before the wide local excision of the primary tumor followed by modified functional neck dissection, all the patients underwent contrast-enhanced CT and MRI and 99mTc-MIBI-SPECT. The SPECT data acquisition (3600 arc, 128×128 matrix, 64 projections, 20 s/projection) was performed 15 min after an intravenous injection of 555–740 MBq of 99mTc-MIBI under the dual head &ggr;-camera (E Cam, Siemens, Erlangen, Germany) using the low-energy, high-resolution, parallel hole collimator. SPECT data reconstruction was achieved by filtered back projection using the Butterworth filter with a critical frequency of 0.5 and power 10.0. Only visual assessment was used for defining a positive lymph nodes (LNs) on reconstructed SPECT images and maximum intensity projection images. Histopathological examination of LNs was performed using hematoxylin and eosin staining. Results A total of 351 LNs were excised surgically (functional neck dissection) from 20 tongue cancer patients having N0 neck disease. Only nine of 351 LNs were documented as being positive for malignancy on histopathological examination. These nine LNs were distributed in eight of 20 patients. CT, MRI, and MIBI-SPECT could accurately identify one, three, and five LNs, respectively. In one of the eight patients, 99mTc-MIBI-SPECT could not distinguish between two LNs present at the same level, having size of 6.0 and 8.0 mm. In this study, 99mTc-MIBI-SPECT was shown to have better sensitivity/positive predictive values (55.5%/71%) than either CT (11%/33%) or MRI (33%/60%). The histopathologically documented metastatic LNs picked up by CT or MRI were also identified by 99mTc-MIBI-SPECT. Conclusion In this preliminary prospective study, we observed that 40% (8/20) of the clinically neck-negative carcinoma tongue patients harbored metastatic LNs. 99mTc-MIBI-SPECT is a more effective imaging modality in the staging of clinically neck-negative LN metastases in carcinoma tongue as compared with CT or MRI.