Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning.
MetadataShow full item record
<h4>Background and purpose</h4>Computed tomography (CT) imaging is the current gold standard for radiotherapy treatment planning (RTP). The establishment of a magnetic resonance imaging (MRI) only RTP workflow requires the generation of a synthetic CT (sCT) for dose calculation. This study evaluates the feasibility of using a multi-atlas sCT synthesis approach (sCT<sub>a</sub>) for head and neck and prostate patients.<h4>Material and methods</h4>The multi-atlas method was based on pairs of non-rigidly aligned MR and CT images. The sCT<sub>a</sub> was obtained by registering the MRI atlases to the patient's MRI and by fusing the mapped atlases according to morphological similarity to the patient. For comparison, a bulk density assignment approach (sCT<sub>bda</sub>) was also evaluated. The sCT<sub>bda</sub> was obtained by assigning density values to MRI tissue classes (air, bone and soft-tissue). After evaluating the synthesis accuracy of the sCTs (mean absolute error), sCT-based delineations were geometrically compared to the CT-based delineations. Clinical plans were re-calculated on both sCTs and a dose-volume histogram and a gamma analysis was performed using the CT dose as ground truth.<h4>Results</h4>Results showed that both sCTs were suitable to perform clinical dose calculations with mean dose differences less than 1% for both the planning target volume and the organs at risk. However, only the sCT<sub>a</sub> provided an accurate and automatic delineation of bone.<h4>Conclusions</h4>Combining MR delineations with our multi-atlas CT synthesis method could enable MRI-only treatment planning and thus improve the dosimetric and geometric accuracy of the treatment, and reduce the number of imaging procedures.
Tomography, X-Ray Computed
Magnetic Resonance Imaging
Radiotherapy Planning, Computer-Assisted
Atlases as Topic
Clinical Academic Radiotherapy (Dearnaley)
Radiotherapy Physics Modelling
License start date
Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), 2017, 35 pp. 7 - 17