The value of SPECT with 201Tl chloride, in combination with MRI (particularly short inversion-time inversion recovery [STIR] sequences that suppress fat signals) to detect and characterize cervical lymphadenopathies (nodes > or = 1 cm), and ex vivo lymph node 201Tl uptake were studied in patients with squamous cell carcinoma of the head and neck.
Methods: Preoperative SPECT and MRI, displayed in similar planes, were compared with the histologic findings in 15 neck dissection specimens from 12 patients with squamous cell carcinoma of the head and neck (9 with unilateral and 3 with bilateral neck dissection). Results were evaluated topographically with regard to the lymph node compartments (levels) of the neck. In addition, in 8 of these patients, the 201Tl activity of dissected lymph nodes of 10 neck sides was measured immediately after surgery in a gamma counter and expressed as percentage of the injected dose per gram tissue (%ID/g).
Results: Sixty-two lymph node levels were evaluated histologically. The high sensitivity of MRI (92% versus 71% for 201Tl SPECT), which correctly detected lymph node involvement in 22 of 24 levels, and the high specificity of 201Tl SPECT (92% versus 71% for MRI), which correctly characterized as negative 35 of 38 lymph node levels without metastasis on histology, led to a combined 201Tl SPECT/MRI accuracy of 92%. 201Tl SPECT was particularly effective in excluding involvement in 9 tumor-free neck levels with pathologically enlarged lymph nodes on MRI but failed to confirm involvement in 5 other tumor-positive levels. Mean 201Tl uptake in 53 lymph nodes with confirmed histologic involvement was significantly higher than uptake in 145 tumor-free lymph nodes (0.0043+/-0.0022 %ID/g versus 0.0023+/-0.0014 %ID/g, P = 0.0001), muscle and fat tissue but clearly lower than salivary gland uptake.
Conclusion: Although 201Tl SPECT is not sensitive enough to be used as an independent imaging modality for staging of the neck, its correlative application with MRI appears to be an accurate method for the assessment of regional spread in head and neck squamous cell carcinoma. The ability of 201Tl SPECT to characterize neck lymphadenopathies detected by MRI appears to be based on the difference in 201Tl concentration found in lymph nodes with and without tumor involvement.