Key words

IJNM

Indian Journal of Nuclear Medicine

0972-3919

Society of Nuclear Medicine, India

ijnm-22-4-047

RESEARCH ARTICLE

Initial Experience of PET/CT in Discriminating Solitary Pulmonary Nodule

Rangarajan

Purandare

N C

Shah

Sharma

A R

Pathak

Arora

Bioimaging Unit, Tata Memorial Hospital, Parel, Mumbai, 400012.

122007

224

Key wordsFDGPET-CTSolitary Pulmonary Nodule

Aims

The term Solitary pulmonary Nodule (SPN) describes a well-circumscribed, rounded, smooth edged, dense pulmonary lesion, 3 cm or less in diameter. Many SPNs are malignant and efforts are on to discriminate them from benign ones, so that the malignant ones can be removed in time for better long time disease free survival. Positron Emission Tomography (PET) with ¹⁸F FDG was the investigation of choice with the highest accuracy to discriminate benign from malignant and was the first indication approved by the FDA.In Line CT in PET/CT adds radiological characterization of the nodule and this could improve the accuracy. Our aim is to study the accuracy of FDG PET/CT in discriminating SPN as benign from malignant.

Material and Methods

14 patients with lung lesion on xray chest with dimension between 1cms to 3 cms and fulfilled the criteria of being called a SPN-namely absence of any other lesion in thorax, underwent FDG PET/CT scan. After a minimum of 6 hours fasting, and ensuring blood sugar <150mg/dl, 10mCi 18 F FDG was injected. After 60 minutes uptake period, they underwent a PET/CT scan from the base of skull to mid third of thighs. Scan was interpreted looking for SUV Max bw (g/ml). CT characteristics of the lesion were noted. Final Histopathology or follow-up scans after 6 months were considered as gold standard. The study was analyzed in a retrospective mode.

Results

The study was divided in to two groups-SUV below and above 3. The group with SPN with FDG uptake less than 3 had 5 patients. 4 of them had no FDG uptake or SUV of 0. The fifth patient SUV was 1.8 and size of 1 to 2.6 cms. Three lesions were benign on Histopathology and two were followed up for a year with no change in nodule or FDG uptake. The other group with SUV >3, had 9 patients. Seven of them had malignant lesions confirmed on HP with SUV ranging between 3.6–26 and size of 1.6–4 cms. Two were false positives who turned out to be tuberculosis with SUV of 4.8 and 8.6 respectively and size 1.2 and 2.4 cms.

Conclusion

In this small group of 14 patients, with a cutoff of SUV of 3, PET/CT imaging could discriminate the SPN as malignant from benign with a sensitivity of 100% and specificity of 60%. While absent uptake or low grade FDG uptake is suggestive of benign disease, higher SUV and uptake does not mean malignancy always and must always be followed by a PET/CT guided biopsy.

Initial Experience of PET/CT in Discriminating Solitary Pulmonary Nodule

Keywords