Correlative Tl-201 SPECT, MRI and ex vivo Tl-201 uptake in detecting and characterizing cervical lymphadenopathy in head and neck squamous cell carcinoma

The value of SPECT with Tl-201 chloride, in combination with MRI (particula rly short inversion-time inversion recovery [STIR] sequences that suppress fat signals) to detect and characterize cervical lymphadenopathies (nodes g reater than or equal to 1 cm), and ex vivo lymph node Tl-201 uptake were st udied in patients with squamous cell carcinoma of the head and neck. Method s: Preoperative SPECT and MRI, displayed in similar planes, were compared w ith the histologic findings in 15 neck dissection specimens from 12 patient s with squamous cell carcinoma of the head and neck (9 with unilateral and 3 with bilateral neck dissection). Results were evaluated topographically w ith regard to the lymph node compartments (levels) of the neck. In addition , in 8 of these patients, the Tl-201 activity of dissected lymph nodes of 1 0 neck sides was measured immediately after surgery in a gamma counter and expressed as percentage of the injected dose per gram tissue (%ID/g). Resul ts: Sixty-two lymph node levels were evaluated histologically. The high sen sitivity of MRI (92% versus 71% for Tl-201 SPECT), which correctly detected lymph node involvement in 22 of 24 levels, and the high specificity of Tl- 201 SPECT (92% versus 71% far MRI), which correctly characterized as negati ve 35 of 38 lymph node levels without metastasis on histology, led to a com bined Tl-201 SPECT/MRI accuracy of 92%. Tl-201 SPECT was particularly effec tive in excluding involvement in 9 tumor-free neck levels with pathological ly enlarged lymph nodes on MRI but failed to confirm involvement in 5 other tumor-positive levels. Mean Tl-201 uptake in 53 lymph nodes with confirmed histologic involvement was significantly higher than uptake in 145 tumor-f ree 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 upta ke. Conclusion: Although Tl-201 SPECT is not sensitive enough to be used as an independent imaging modality far staging of the neck, its correlative a pplication with MRI appears to be an accurate method for the assessment of regional spread in head and neck squamous cell carcinoma. The ability of Tl -201 SPECT to characterize neck lymphadenopathies detected by MRI appears t o be based on the difference in Tl-201 concentration found in lymph nodes w ith and without tumor involvement.