Patient-specific calibration of cone-beam computed tomography data sets for radiotherapy dose calculations and treatment plan assessment.
J Appl Clin Med Phys
; 19(2): 249-257, 2018 Mar.
Article
en En
| MEDLINE
| ID: mdl-29479821
ABSTRACT
PURPOSE:
In this work, we propose a new method of calibrating cone beam computed tomography (CBCT) data sets for radiotherapy dose calculation and plan assessment. The motivation for this patient-specific calibration (PSC) method is to develop an efficient, robust, and accurate CBCT calibration process that is less susceptible to deformable image registration (DIR) errors.METHODS:
Instead of mapping the CT numbers voxel-by-voxel with traditional DIR calibration methods, the PSC methods generates correlation plots between deformably registered planning CT and CBCT voxel values, for each image slice. A linear calibration curve specific to each slice is then obtained by least-squares fitting, and applied to the CBCT slice's voxel values. This allows each CBCT slice to be corrected using DIR without altering the patient geometry through regional DIR errors. A retrospective study was performed on 15 head-and-neck cancer patients, each having routine CBCTs and a middle-of-treatment re-planning CT (reCT). The original treatment plan was re-calculated on the patient's reCT image set (serving as the gold standard) as well as the image sets produced by voxel-to-voxel DIR, density-overriding, and the new PSC calibration methods. Dose accuracy of each calibration method was compared to the reference reCT data set using common dose-volume metrics and 3D gamma analysis. A phantom study was also performed to assess the accuracy of the DIR and PSC CBCT calibration methods compared with planning CT.RESULTS:
Compared with the gold standard using reCT, the average dose metric differences were ≤ 1.1% for all three methods (PSC -0.3%; DIR -0.7%; density-override -1.1%). The average gamma pass rates with thresholds 3%, 3 mm were also similar among the three techniques (PSC 95.0%; DIR 96.1%; density-override 94.4%).CONCLUSIONS:
An automated patient-specific calibration method was developed which yielded strong dosimetric agreement with the results obtained using a re-planning CT for head-and-neck patients.Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Algoritmos
/
Planificación de la Radioterapia Asistida por Computador
/
Fantasmas de Imagen
/
Radioterapia de Intensidad Modulada
/
Tomografía Computarizada de Haz Cónico
/
Neoplasias de Cabeza y Cuello
Tipo de estudio:
Observational_studies
/
Prognostic_studies
Límite:
Humans
Idioma:
En
Revista:
J Appl Clin Med Phys
Asunto de la revista:
BIOFISICA
Año:
2018
Tipo del documento:
Article
País de afiliación:
Canadá