Vol 25, No 2 (2020)
Original research articles
Published online: 2020-03-01

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A new strategy for craniospinal axis localization and adaptive dosimetric evaluation using cone beam CT

Kather Hussain Rafic1, Christopher Sujith1, Balakrishnan Rajesh1, Ebenezer Suman Babu S1, Peace Balasingh Timothy, B Selvamani1, Paul B Ravindran1
DOI: 10.1016/j.rpor.2019.11.003
Rep Pract Oncol Radiother 2020;25(2):282-292.

Abstract

Background and Aim

Computational complexities encountered in craniospinal irradiation (CSI) have been widely investigated with different planning strategies. However, localization of the entire craniospinal axis (CSA) and evaluation of adaptive treatment plans have traditionally been ignored in CSI treatment. In this study, a new strategy for CSI with comprehensive CSA localization and adaptive plan evaluation has been demonstrated using cone beam CT with extended longitudinal field-of-view (CBCTeLFOV).

Materials and Methods

Multi-scan CBCT images were acquired with fixed longitudinal table translations (with 1cm cone-beam overlap) and then fused into a single DICOM-set using the custom software coded in MatLab™. A novel approach for validation of CBCTeLFOV was demonstrated by combined geometry of Catphan-504 and Catphan-604 phantoms. To simulate actual treatment scenarios, at first, the end-to-end workflow of CSI with VMAT was investigated using an anthropomorphic phantom and then applied for two patients (based on random selection).

Results

The fused CBCTeLFOV images were in excellent agreement with planning CT (pCT). The custom developed software effectively manages spatial misalignments arising out of the uncertainties in treatment/setup geometry. Although the structures mapped from pCT to CBCTeLFOV showed minimal variations, a maximum spatial displacement of up to 1.2cm (and the mean of 0.8±0.3cm) was recorded in phantom study. Adaptive plan evaluation of patient paradigms showed the likelihood of under-dosing the craniospinal target.

Conclusion

Our protocol serves as a guide for precise localization of entire CSA and to ensure adequate dose to the large and complex targets. It can also be adapted for other complex treatment techniques such as total-marrow-irradiation and total-lymphoid-irradiation.

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Reports of Practical Oncology and Radiotherapy