RESUMO
BACKGROUND: To evaluate dosimetry between CT based radiation planning and PET-CT based radiation planning. MATERIAL & METHODS: Histologically proven 40 cases of locally advanced non-small cell carcinoma of lung were accrued for the prospective study. Contrast enhanced planning CT images and PET images were acquired. Target volume delineation, organs of interest & radiation planning were performed in Eclipse V 14.5 followed by dosimetric comparison among GTV, PTV and OARs. A p-value of <0.05 was considered significant. RESULTS: The mean of GTV were 141.18 ± 119.76 cc in CT and 115.54 ± 91.02 cc in PET-CT based and the difference was statistically significant (p=0.03). The mean of CTV were 313.91 ± 180.87 cc in CT and 260.81 ± 148.83 cc in PET-CT based and the difference was statistically significant (p=0.03). The contralateral lung mean dose was statistically very significant (p<0.01) among both the 3D-CRT plans which were 8.49 Gy in CECT based planning and 9.53 Gy in PET CT based planning. The heart mean dose was also statistically significant (p=0.03) among the plans which were 17.90 Gy in CECT based planning and 17.06 Gy in PET CT based planning. Mann-Whitney U test showed the CT based PTV D90 was 58.20 Gy vs 57.58 Gy in PET CT based planning (p=0.02). PTV V95 were also comparable in both of the plans (p=0.02). CONCLUSIONS: GTV measured using PET-CT, may be greater or lesser than the CECT-based GTV. PET-CT-based contouring is more accurate for identifying tumour margins and new lymph node volumes.
