Upright 3D Treatment Planning Using a Vertical CT

Shah, Anand P.; Strauss, Jonathan B.; Kirk, M.; Chen, Sea S.; Kroc, Thomas; Zusag, Thomas

doi:10.1016/j.meddos.2008.05.004

Cited by 22 publications

(25 citation statements)

References 6 publications

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“…Vertical treatment requires taking computed tomography (CT) images in the vertical position for treatment planning. Although several vertical CT systems exist, they are specialized and are not available in most clinical settings. One existing solution is to use the on‐board imager of a common medical linear accelerator to take vertical cone‐beam CT (CBCT) images, which can be implemented by programming the Varian TrueBeam linear accelerator in developer mode and rotating the patient couch .…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Density correction to improve CT number mapping in thoracic deformable image registration

Yang

Zhang

et al. 2019

Medical Physics

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Purpose To improve the accuracy of computed tomography (CT) number mapping inside the lung in deformable image registration with large differences in lung volume for applications in vertical CT imaging and adaptive radiotherapy. Methods The deep inspiration breath hold (DIBH) CT image and the end of exhalation (EE) phase image in four‐dimensional CT of 14 thoracic cancer patients were used in this study. Lung volumes were manually delineated. A Demons‐based deformable registration was first applied to register the EE CT to the DIBH CT for each patient, and the resulting deformation vector field deformed the EE CT image to the DIBH CT space. Given that the mass of the lung remains the same during respiration, we created a mass‐preserving model to correlate lung density variations with volumetric changes, which were characterized by the Jacobian derived from the deformation field. The Jacobian determinant was used to correct the lung CT numbers transferred from the EE CT image. The absolute intensity differences created by subtracting the deformed EE CT from the DIBH CT with and without density correction were compared. Results The ratio of DIBH CT to EE CT lung volumes was 1.6 on average. The deformable registration registered the lung shape well, but the appearance of voxel intensities inside the lung was different, demonstrating the need for density correction. Without density correction, the mean and standard deviation of the absolute intensity difference between the deformed EE CT and the DIBH CT inside the lung were 54.5 ± 45.5 for all cases. After density correction, these numbers decreased to 18.1 ± 34.9, demonstrating greater accuracy. The cumulative histogram of the intensity difference also showed that density correction improved CT number mapping greatly. Conclusion Density correction improves CT number mapping inside the lung in deformable image registration for difficult cases with large lung volume differences.

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Section: Introductionmentioning

confidence: 99%

Technical Note: Density correction to improve CT number mapping in thoracic deformable image registration

Yang

Zhang

et al. 2019

Medical Physics

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“…Historically, chairs for radiation therapy have been used primarily as an exception for patients unable to tolerate the lying position and have involved temporary replacement of the treatment couch with an upright unit 7, 8. Additionally, these previous studies are from an era in which treatment planning was carried out primarily using 2D image acquisition9, 10, 11 and margins which were much more tolerant of positional inaccuracies.…”

Section: Introductionmentioning

confidence: 99%

Reproducibility of patient setup in the seated treatment position: A novel treatment chair design

McCarroll

Beadle

Fullen

et al. 2017

J Applied Clin Med Phys

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Radiotherapy in a seated position may be indicated for patients who are unable to lie on the treatment couch for the duration of treatment, in scenarios where a seated treatment position provides superior anatomical positioning and dose distributions, or for a low‐cost system designed using a fixed treatment beam and rotating seated patient. In this study, we report a novel treatment chair that was constructed to allow for three‐dimensional imaging and treatment delivery while ensuring robust immobilization, providing reproducibility equivalent to that in the traditional supine position. Five patients undergoing radiation treatment for head‐and‐neck cancers were enrolled and were setup in the chair, with immobilization devices created, and then imaged with orthogonal X‐rays in a scenario that mimicked radiation treatments (without treatment delivery). Six subregions of the acquired images were rigidly registered to evaluate intra‐ and interfraction displacement and chair construction. Displacements under conditions of simulated image guidance were acquired by first registering one subregion; the residual displacement of other subregions was then measured. Additionally, we administered a patient questionnaire to gain patient feedback and assess comparison to the supine position. Average inter‐ and intrafraction displacements of all subregions in the seated position were less than 2 and 3 mm, respectively. When image guidance was simulated, L‐R and A‐P interfraction displacements were reduced by an average of 1 mm, providing setup of comparable quality to supine setups. The enrolled patients, who had no indication for a seated treatment position, reported no preference in the seated or the supine position. The novel chair design provides acceptable inter‐ and intrafraction displacement, with reproducibility equivalent to that reported for patients in the supine position. Patient feedback will be incorporated in the refinement of the chair, facilitating treatment of head‐and‐neck cancer in patients who are unable to lie for the duration of treatment or for use in an economical fixed‐beam setup.

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“…In order to introduce a practical upright clinical treatment protocol, it is first necessary to produce images for treatment planning with the patient in the upright position. Although several vertical CT systems are in use, 2,[5][6][7] these are specialized systems not available in most clinical settings. In this study, the ability of the onboard imager of a common medical linac to take upright CT images was investigated.…”

Section: Introductionmentioning

confidence: 99%