Evaluation of diagnostic abilities of Ga-SPECT for head and neck lesions

Single-photon emission computed tomography (SPECT) using gallium (Ga) has been frequently used for diagnosing head and neck tumors in patients. Although the usefulness of Ga-SPECT is well known, the degree of the increase in diagnostic ability with Ga-SPECT for head and neck tumors has not been reported. We compared the ability of the planar images of Ga scintigraphy, SPECT images of Ga scintigraphy, and CT images to diagnose head and neck primary tumors and neck metastases.

The subjects of this study were 167 patients with malignant head/neck lesions. For Ga scintigraphy, Ga-67-citrate (74 MBq) was injected via a cubital vein. Planar and SPECT images were taken 72 h after the Ga-67-citrate injection. The rate of detection of the primary lesions was compared first between SPECT and planar images then between SPECT and CT images. The rate of detection for each stage of disease according to the TNM classification was also analyzed.

The rate of detection of primary lesions was 50% with planar imaging and 69% with SPECT. And similarly, regarding the rate of detection of lymph node metastases, there was a significant difference between planar imaging and SPECT. The rate of detection of primary lesions was 70% for both CT and SPECT. At T stage, the rates of detection of primary lesions with each imaging technique were 11% with planar imaging and 39% with SPECT, and 22% with CT for stage T1.

This study revealed the marked superiority of SPECT images over planar images in terms of the ability to detect primary tumors and tumor metastasis to cervical lymph nodes. Furthermore, the primary T1 tumor detection rate of SPECT images was higher than that of CT images. On the basis of these results, the concomitant use of SPECT is highly recommended when Ga scintigraphy is performed to check for malignant head/neck tumors.