introduction of a simple algorithm to create synthetic‑computedtomography of the head from magnetic resonance imaging

Background: recently, magnetic resonance imaging (mri)‑based radiotherapy has becomea favorite science field for treatment planning purposes. in this study, a simple algorithm wasintroduced to create synthetic computed tomography (sct) of the head from mri. methods: asimple atlas‑based method was proposed to create sct images based on the paired t1/t2‑weightedmri and bone/brain window ct. dataset included 10 patients with glioblastoma multiformeand 10 patients with other brain tumors. to generate a sct image, first each mr from datasetwas registered to the target‑mr, the resulting transformation was applied to the correspondingct to create the set of deformed cts. then, deformed‑cts were fused to generate a single sctimage. the sct images were compared with the real ct images using geometric measures (meanabsolute error [mae] and dice similarity coefficient of bone [dsc_bone]) and hounsfield unitgamma‑index (г_hu) with criteria 100 hu/2 mm. results: the evaluations carried out by mae,dsc_bone, and г_hu showed a good agreement between the synthetic and real ct images. theresults represented the range of 78–93 hu and 0.80–0.89 for mae and dscbone, respectively.the г_hu also showed that approximately 91%–93% of pixels fulfilled the criteria 100 hu/2 mmfor brain tumors. conclusion: this method showed that mr sequence (t1w or t2w) should beselected depending on the type of tumor. in addition, the brain window synthetic cts are in betteragreement with real ct relative to bone window sct images.