摘要
We compared two treatment planning methods for stereotactic boost for treating nasopharyngeal carcinoma (NPC): the use of conventional whole-body bismuth germanate (BGO) scintillator positron emission tomography (PETCONVWB) versus the new brain (BR) PET system using semiconductor detectors (PETNEWBR).
Twelve patients with NPC were enrolled in this study. [18F]Fluorodeoxyglucose-PET images were acquired using both the PETNEWBR and the PETCONVWB system on the same day. Computed tomography (CT) and two PET data sets were transferred to a treatment planning system, and the PETCONVWB and PETNEWBR images were coregistered with the same set of CT images. Window width and level values for all PET images were fixed at 3000 and 300, respectively. The gross tumor volume (GTV) was visually delineated on PET images by using either PETCONVWB (GTVCONV) images or PETNEWBR (GTVNEW) images. Assuming a stereotactic radiotherapy boost of 7 ports, the prescribed dose delivered to 95% of the planning target volume (PTV) was set to 2000 cGy in 4 fractions.
The average absolute volume (±standard deviation [SD]) of GTVNEW was 15.7 ml (±9.9) ml, and that of GTVCONV was 34.0 (±20.5) ml. The average GTVNEW was significantly smaller than that of GTVCONV (p = 0.0006). There was no statistically significant difference between the maximum dose (p = 0.0585) and the mean dose (p = 0.2748) of PTV. The radiotherapy treatment plan based on the new gross tumor volume (PLANNEW) significantly reduced maximum doses to the cerebrum and cerebellum (p = 0.0418) and to brain stem (p = 0.0041).
Results of the present study suggest that the new brain PET system using semiconductor detectors can provide more accurate tumor delineation than the conventional whole-body BGO PET system and may be an important tool for functional and molecular radiotherapy treatment planning.