Comparison of setup accuracy of three different thermoplastic masks for the treatment of brain and head and neck tumors

Towards the production of radiotherapy treatment shells on 3D printers using data derived from DICOM CT and MRI: preclinical feasibility studies

“…Studies have suggested that both soft drape and BDS radiotherapy shells produced in a standard way do allow a certain amount of movement and hence the recommendation to employ some method of checking patient position prior to commencing each treatment [1,[2][3][4]10,14,15,16]. Rotondo et al present an approach to calculate errors between immobilisation techniques by determining displacement errors between co-registered data sets of patients undergoing different immobilisation techniques [15].…”

Is daily computed tomography image guidance necessary for nasal cavity and nasopharyngeal radiotherapy? An investigation based on helical tomotherapy

“…A similar operation was performed as outlined by Xia and colleagues (4) and Gilbeau and colleagues (7) to calculate $D_{weekly}(\overrightarrow{\mathrm{normalr}})$ for each patient with the adjusted daily shifts. Three sets of $\text{DVHs}—{\text{DVH}}_u$ for $D_{\mathit{\text{unregistered}}}(\overrightarrow{\mathrm{normalr}}),{\text{DVH}}_r$ for $D_{\mathit{\text{registered}}}(\overrightarrow{\mathrm{normalr}})$, and ${\text{DVH}}_w$ for $D_{\mathit{\text{weekly}}}(\overrightarrow{\mathrm{normalr}})$ —were then generated for comparison.…”

“…With standard head‐and‐neck radiotherapy immobilization techniques (conventional thermoplastic masks, baseplate fixation, three‐point laser alignment, and weekly portal film evaluation), a setup variability of 2 – 5 mm has been suggested by previous studies. ( 7 – 9 ) Systematic errors of $1.6-4.6\hspace{0.17em}\text{mm}$ and random errors of $1.1-2.5\hspace{0.17em}\text{mm}$ were reported by Hurkmans et al for portal imaging, with “state of the art” setup accuracy of 2 mm (one‐dimensional) standard deviation for both types of errors (8) . A recent study by Hong et al using a high‐precision optically‐guided patient localization system reported a 3.33 mm absolute average daily setup error in any one of three dimensions, with a composite vector setup error of 6.97 mm in three‐dimensional (3D) space (9) …”

Monitoring frequency of intra‐fraction patient motion using the ExacTrac system for LINAC‐based SRS treatments

“…To achieve the required levels of setup accuracy, image guidance and a thermoplastic mask attached to the treatment couch are used in place of an invasive head frame. Previous works have shown that intra‐fractional positioning accuracy of mask‐based immobilization systems range from 1.59 ± 0.84 mm to 4.7 ± 1.7 mm using a thermoplastic mask and image guidance from Cone‐beam CT (CBCT), CT simulation, portal images, and biplanar diagnostic x ray 2, 3, 4, 5. These positioning errors are still too large for SRS treatments, due to irradiating critical organs during the treatment.…”