Comparison of [(18)F]FDG PET and (201)Tl SPECT in evaluation of pulmonary nodules.
Recent reports have indicated the value of [(18)F]FDG PET and (201)Tl SPECT in diagnosing lung cancer. In this study, we compared the diagnostic value of FDG PET and (201)Tl SPECT in the evaluation of pulmonary nodules.


METHODS
Sixty-three patients with 66 pulmonary nodules suspected to be lung cancer on the basis of chest CT were examined by FDG PET and (201)Tl SPECT (early and delayed scans) within a week of each study. For semiquantitative analysis, the standardized uptake value (SUV) or the tumor-to-nontumor activity ratio (T/N) (or both) was calculated. All of these lesions were completely removed thoracoscopically or by thoracotomy and were examined histologically.


RESULTS
Fifty-four nodules were histologically confirmed to be malignant tumors, and 12 were benign. Both techniques delineated focal lesions with an increase in tracer accumulation in 41 of 54 lung cancers. (201)Tl SPECT on early or delayed scans (or both) identified 4 additional lung cancers that FDG PET images did not reveal: 3 bronchioloalveolar carcinomas and a well-differentiated adenocarcinoma. FDG PET identified 3 additional lung cancers that (201)Tl SPECT images did not reveal; 2 of these lung cancers were <2 cm in diameter. The mean FDG SUV and T/N of bronchioloalveolar carcinomas (2.06 +/- 0.76 and 3.49 +/- 1.03, respectively) were significantly lower than those of poorly differentiated adenocarcinomas (5.55 +/- 2.01 [P = 0.026] and 8.23 +/- 2.16 [P = 0.01], respectively). However, no significant difference was found in (201)Tl T/N on early and delayed scans between bronchioloalveolar carcinomas (1.64 +/- 0.29 and 1.87 +/- 0.42, respectively) and poorly differentiated adenocarcinomas (1.58 +/- 0.32 and 2.76 +/- 1.36, respectively). Of the 12 benign nodules, FDG PET and (201)Tl SPECT showed false-positive results for the same 7 benign nodules (58.3%) (4 granulomas, 1 sarcoidosis, 1 inflammatory pseudotumor, and 1 aspergilloma). Negative FDG PET findings and positive (201)Tl SPECT findings were obtained only for bronchioloalveolar carcinomas or a well-differentiated adenocarcinoma but not for other histologic types of lung cancers or benign pulmonary nodules.


CONCLUSIONS
No significant difference was found between FDG PET and (201)Tl SPECT in specificity for the differentiation of malignant and benign pulmonary nodules. The degree of differentiation of lung adenocarcinoma correlated with FDG uptake but not with (201)Tl uptake. Bronchioloalveolar carcinoma (a well-differentiated, slow-growing tumor) findings typically were positive with (201)Tl but were negative with FDG. The combination of FDG PET and (201)Tl SPECT may provide additional information regarding the tissue characterization of pulmonary nodules.
Higashi
K
K
Department of Radiology, Kanazawa Medical University, 1-1, Uchinada, Daigaku, Kahoku-gun, Ishikawa, 920-0293, Japan.
Ueda
Y
Y
Sakuma
T
T
Seki
H
H
Oguchi
M
M
Taniguchi
M
M
Taki
S
S
Tonami
H
H
Katsuda
S
S
Yamamoto
I
I
D000230:Adenocarcinoma / Q000000981:diagnostic imaging; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000000981:diagnostic imaging; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon
D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes; D019788:Fluorodeoxyglucose F18