01.04.2010 | Original Article
18F-FDG PET-CT respiratory gating in characterization of pulmonary lesions: approximation towards clinical indications
Erschienen in: Annals of Nuclear Medicine | Ausgabe 3/2010
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Aim
To evaluate the effect of the 18F-FDG PET-CT respiratory gating (4D) study in the correct documentation of pulmonary lesions with faint uptake in standard PET-CT.
Methods
Forty-two pulmonary lesions with a low or no detectable uptake of FDG (SUVmax < 2.5) in 3D PET-CT were prospectively evaluated in 28 patients (19 males and 9 females), mean age 66.5 years (41–81). 22 patients had neoplastic background. A conventional PET-CT (3D) total body scan was performed approximately 60 min after iv injection of a mean dose of 370 MBq. Furthermore, a 4D PET-CT (synchronized with respiratory movement) thorax study was acquired. SUVmax was determined for each lesion in both studies. For the 4D studies, we selected the SUVmax in respiratory period with the highest uptake (“best bin”). We calculated the SUVmax percentage difference between 3D and 4D PET-CT (% difference = SUVmax 4D − SUVmax 3D/SUVmax 3D × 100) and the relation of this value with the size and locations of the lesions. In 4D study, any lesion with SUVmax ≥ 2.5 was classified as malignant. We assessed the changes of lesion classification (from benign to malignant) applying the 4D technique. The final diagnosis was obtained by histological assessment or clinical and radiological follow-up longer than 12 months.
Results
Forty out of 42 lesions showed an increase of SUVmax in the 4D study with respect to 3D. The mean SUVmax in the 3D and 4D PET-CT studies were 1.33 (±0.59) and 2.26 (±0.87), respectively. The SUVmax percentage difference mean between both techniques was 83.3% (±80.81).The smaller the lesion the greater was the SUVmax percentage difference (P < 0.05). No differences were observed depending on the location of the lesion. In 40% of cases, there was a change in the final classification of lesions from benign to malignant. In the final diagnosis, 24 lesions were malignant. 4D PET-CT diagnosed correctly the 52% of them.
Conclusions
The 4D PET-CT study permitted a better characterization of malignant lung lesions compared with the standard PET-CT, because of its higher sensitivity. 4D PET-CT is a recommendable technique in the early diagnosis of malignant lesions.
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