Prospective comparison of two gamma probes for intraoperative detection of 18F-FDG: in vitro assessment and clinical evaluation in differentiated thyroid cancer patients with iodine-negative recurrence.
OBJECTIVE
This study was aimed at evaluating the spatial resolution and sensitivity of two hand-held gamma probes. Radioguided surgery was tested in seven patients with iodine-negative differentiated thyroid cancer (DTC) recurrence using (18)F-FDG PET.


METHODS
Two gamma probes were evaluated: Clerad's GammaSup with a collimated CsI(Tl) scintillator and Novelec's Modelo2 with a BGO scintillator. Five measurement tests were performed following the NEMA guidelines (NU3-2004). Radioguided surgery was performed in patients with recurrent DTC and abnormal (18)F-FDG uptake on preoperative (18)F-FDG PET images. Patients were injected with rTSH 2 days before surgery. A mean activity of 211 MBq of (18)F-FDG was injected 60 min before surgery. In vivo and ex vivo counts were recorded for suspected tumours and normal tissue.


RESULTS
Spatial resolution was higher with the CsI(Tl) than with the BGO detector: 20.2-40.6 mm vs 20.6-55.3 mm from 0 to 20 mm depth. Sensitivity in air and water and through side shielding was higher for BGO but the signal-to-noise ratio was 88 and 22 with the BGO compared to 131 and 76 with the CsI(Tl) at 10 and 30 mm depth. Median in vivo SNR (tumour/non-tumour ratio) was 1.8 with both the BGO and the CsI(Tl) detector, while ex vivo ratios of 2.3 and 2.1, respectively, were obtained. Radioguided surgery allowed detection of all of the tumours identified by (18)F-FDG PET images.


CONCLUSIONS
This study demonstrated the feasibility of high-energy photon detection with a conventional scintillator equipped with a collimator. The CsI(TI) probe detected more true events from background than did the BGO detector during surgery.
Curtet
Chantal
C
INSERM, U601, Quai Moncousu, 44035 Nantes, France. ccurtet@nantes.inserm.fr
Carlier
Thomas
T
Mirallié
Eric
E
Bodet-Milin
Caroline
C
Rousseau
Caroline
C
Barbet
Jacques
J
Kraeber-Bodéré
Francoise
F
D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D015902:Gamma Cameras; D006801:Humans; D007430:Intraoperative Care / Q000379:methods; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery*; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery*; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18