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Y. Ren
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P2.02 - Poster Session/ Treatment of Localized Disease – NSCLC (ID 210)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Localized Disease - NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.02-038 - Clinical Evaluations of Odd/Even Respiratory Phases Based Approach for Determining Internal Target Volume in NSCLC Treated with 4D SABR (ID 2361)
09:30 - 09:30 | Author(s): Y. Ren
- Abstract
Background:
Appropriate definition of the target volume with an efficient approach remains a major challenge for early stage NSCLS treated with SBRT technique; one of crucial disturbed factors in delineation of target volume is the tumors movement due to irregular respiration patterns(3), to account for tumor motion, the ICRU Report 62 introduced the concept of an internal target volume (ITV), defined as the clinical target volume (CTV), plus an additional margin to account for geometric uncertainties due to variable tumor motion (4), Conventionally, a free-breathing three-dimensional (3D)-CT scan was adopted to acquire the patient’s anatomic information which leads to geometric distortions (5). To account for these geometric uncertainties, large target volumes are needed, thereby limiting the effectiveness of the radiotherapy (6).To reduce geometric uncertainties in 3D-CT images, time related four-dimensional CT (4D-CT) scanning techniques have been developed in radiation therapy to obtain information about volumetric organ motion associated with respiration. And various methods for definition of the target volume using 4D-CT scans in treatment planning have been reported recently(7,8,9,10), the most accurate method of determining ITV is combined by contouring in each phase of the 4DCT dataset (typically 10 phases). Although this method is widely accepted as a golden standard for delineation of ITV , it poses more efforts and time consuming due to the increased workload for radiation oncologists. To Improve work efficiency many efforts has been done to reduce the workload meanwhile maintain a reasonable ITV, the maximal intensity projection (MIP) dataset has been widely applied in the clinic to define ITV in the early stage; some other researchers investigated ITV from 4D-CT such as ITV2ep(including two extreme phases ) and ITV4phase= ITV2ep+ two phases (20% and 70%) , The matching index (MI) was adopted to evaluate the marching degree between different determining approaches,in this research, we will proposed a new approach to definite an ITV with the best marching index meanwhile with the least time and human resource.
Methods:
December 2013 and March 2014, 46 patients who underwent SABR were included in this retrospective study. All patients underwent imaging with 4DCT scans, The MI and DI index were evaluated ITV~10,~ITV~Yeo,~ITV~EI+EE,~And combining GTV from five odd phasesITVodd, Accordingly the ITV~EVEN~ , and ITV~AVG~ ,ITV~MIP~ were Contoured from two reconstructed 4D-CT Sequences, finally, a method which was not sensitive to the tumor volume and motion Characteristic was selected for clinical use.
Results:
The mean tumor motion (RLR, RAP, RCC, and R3D) were 3.5mm(1.4mm~8.4mm)，4.5mm(1.1mm~8.6mm)，9.5mm(0mm~10mm), 12.3mm (2.5-55.3 mm) respectively. IGTVx volume were Underestimated by25.7%、35.6%、17.9%、12.8%、3.6%、4.8% (P=0.000) respectively. MI index comparisons between six ITV generation methods and ITV~10~ showed statistical significance: 0.69、0.62、0.80、0.86、0.93、0.91（P=0.006）, DI index showed no statistical significance: 0.98、0.98、0.97、0.97、0.99、0.98（P=0.13）, the tumor size and motion amplitude were certified not the independent factors for the MI index of ITV~odd ~and ITV~EVEN~
Conclusion:
IGTV~ODD/EVEN~ based on odd or even 4D-CT phases was not sensitive to tumor size or motion characteristic and was proved to have a good marching with ITV~10~ meanwhile Maintaining a reasonable contouring efficiency, it can be recommend to the institutions which not equipped with the deformable registration systems.
