Accuracy of inverse treatment planning on substitute CT images derived from MR data for brain lesions

Radiation Oncology

Tufve Nyholm¹  Thomas Asklund¹  Adam Johansson¹  Magnus G Karlsson¹  Mohammad M Akhtari¹  Joakim H Jonsson¹ 

[1] Department of Radiation Sciences, Umeå University, Umeå SE-901 87, Sweden

关键词: s-CT;    Substitute CT;    MRI;    Treatment planning;    Radiotherapy;   

Others  :  1150147
DOI  :  10.1186/s13014-014-0308-1

 received in 2013-12-13, accepted in 2014-12-15,  发布年份 2015

【 摘 要 】

Background

In this pilot study we evaluated the performance of a substitute CT (s-CT) image derived from MR data of the brain, as a basis for optimization of intensity modulated rotational therapy, final dose calculation and derivation of reference images for patient positioning.

Methods

S-CT images were created using a Gaussian mixture regression model on five patients previously treated with radiotherapy. Optimizations were compared using D_max, D_min, D_median and D_mean measures for the target volume and relevant risk structures. Final dose calculations were compared using gamma index with 1%/1 mm and 3%/3 mm acceptance criteria. 3D geometric evaluation was conducted using the DICE similarity coefficient for bony structures. 2D geometric comparison of digitally reconstructed radiographs (DRRs) was performed by manual delineation of relevant structures on the s-CT DRR that were transferred to the CT DRR and compared by visual inspection.

Results

Differences for the target volumes in optimization comparisons were small in general, e.g. a mean difference in both D_min and D_max within ±0.3%. For the final dose calculation gamma evaluations, 100% of the voxels passed the 1%/1 mm criterion within the PTV. Within the entire external volume between 99.4% and 100% of the voxels passed the 3%/3 mm criterion. In the 3D geometric comparison, the DICE index varied between approximately 0.8-0.9, depending on the position in the skull. In the 2D DRR comparisons, no appreciable visual differences were found.

Conclusions

Even though the present work involves a limited number of patients, the results provide a strong indication that optimization and dose calculation based on s-CT data is accurate regarding both geometry and dosimetry.

【 授权许可】

   
2015 Jonsson et al.; licensee BioMed Central.

【 图 表 】

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