Thymic lesions in patients with myasthenia gravis: characterization with thallium 201 scintigraphy.
OBJECTIVE
To assess thallium 201 ((201)Tl) single photon emission computed tomography (SPECT) for evaluation of thymic lesions associated with myasthenia gravis (MG), including lymphoid follicular hyperplasia (LFH) and thymoma.


METHODS
(201)Tl SPECT and computed tomography (CT) were performed preoperatively in 46 patients with MG who had undergone thymectomy. SPECT was conducted 15 (early image) and 180 (delayed image) minutes after (201)Tl injection. Results were visually assessed, and (201)Tl uptake ratios (thymic lesion count density/lung count density) were measured for quantitative analysis. Uptake was analyzed among the normal thymus, LFH, and thymoma patient groups.


RESULTS
Histopathologic results indicated a normal thymus, LFH, and thymoma in 19, 16, and 11 patients, respectively. Mean uptake ratios in the normal thymus, LFH, and thymoma were 0.96 (95% CI: 0.90, 1.03), 1.14 (95% CI: 1.04, 1.25), and 1.87 (95% CI: 1.56, 2.25), respectively, on early images and 1.09 (95% CI: 1.00, 1.18), 1.65 (95% CI: 1.48, 1.85), and 2.03 (95% CI: 1.65, 2.50), respectively, on delayed images. Thymoma showed more intense (201)Tl accumulation than did the normal thymus (P <.001) and LFH (P <.001) on early images. Both thymoma (P <.001) and LFH (P <.001) displayed more intense uptake than did the normal thymus on delayed images.


CONCLUSIONS
(201)Tl SPECT can enable differentiation between normal thymus, LFH, and thymoma in patients with MG.
Higuchi
T
T
Department of Nuclear Medicine, Kanazawa University School of Medicine, Takaramachi 13-1, Kanazawa, Ishikawa, Japan. higuchi@med.kanazawa-u.ac.jp
Taki
J
J
Kinuya
S
S
Yamada
M
M
Kawasuji
M
M
Matsui
O
O
Nonomura
A
A
Bunko
H
H
Tonami
N
N
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications*; D011300:Preoperative Care; D013794:Thallium Radioisotopes; D013945:Thymoma / Q000000981:diagnostic imaging; D013952:Thymus Hyperplasia / Q000000981:diagnostic imaging*; D013953:Thymus Neoplasms / Q000000981:diagnostic imaging*; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
D013794:Thallium Radioisotopes