On the accuracy of bulk synthetic CT for MR-guided online adaptive radiotherapy

Autor: L. Azario, Marco De Spirito, Lorenzo Placidi, Luca Boldrini, Francesco Cellini, S. Longo, S. Teodoli, Davide Cusumano, Vincenzo Valentini, Francesca Greco, N. Dinapoli
Rok vydání: 2019
Předmět:
Adult
Male
Dose-volume histogram
Dose calculation
Radiotherapy Planning
MR-guided radiotherapy
Mean difference
Pelvis
030218 nuclear medicine & medical imaging
03 medical and health sciences
Computer-Assisted
0302 clinical medicine
Treatment plan
Abdomen
80 and over
medicine
Humans
Radiology
Nuclear Medicine and imaging
Online adaptive radiotherapy
Adaptive radiotherapy
Tomography
Synthetic CT
Settore MED/36 - DIAGNOSTICA PER IMMAGINI E RADIOTERAPIA
Aged
Aged
80 and over
Radiotherapy
medicine.diagnostic_test
business.industry
Radiotherapy Planning
Computer-Assisted
Ultrasound
Radiotherapy Dosage
Magnetic resonance imaging
General Medicine
Middle Aged
Magnetic Resonance Imaging
X-Ray Computed
Image-Guided
030220 oncology & carcinogenesis
Female
Bulk ED assignment
Radiotherapy
Image-Guided
Tomography
X-Ray Computed
Nuclear medicine
business
Mri guided
Zdroj: La radiologia medica. 125:157-164
ISSN: 1826-6983
0033-8362
DOI: 10.1007/s11547-019-01090-0
Popis: MR-guided radiotherapy (MRgRT) relies on the daily assignment of a relative electron density (RED) map to allow the fraction specific dose calculation. One approach to assign the RED map consists of segmenting the daily magnetic resonance image into five different density levels and assigning a RED bulk value to each level to generate a synthetic CT (sCT). The aim of this study is to evaluate the dose calculation accuracy of this approach for applications in MRgRT. A planning CT (pCT) was acquired for 26 patients with abdominal and pelvic lesions and segmented in five levels similar to an online approach: air, lung, fat, soft tissue and bone. For each patient, the median RED value was calculated for fat, soft tissue and bone. Two sCTs were generated assigning different bulk values to the segmented levels on pCT: The sCTICRU uses the RED values recommended by ICRU46, and the sCTtailor uses the median patient-specific RED values. The same treatment plan was calculated on two the sCTs and the pCT. The dose calculation accuracy was investigated in terms of gamma analysis and dose volume histogram parameters. Good agreement was found between dose calculated on sCTs and pCT (gamma passing rate 1%/1 mm equal to 91.2% ± 6.9% for sCTICRU and 93.7% ± 5.3% b or sCTtailor). The mean difference in estimating V95 (PTV) was equal to 0.2% using sCTtailor and 1.2% using sCTICRU, respect to pCT values The bulk sCT guarantees a high level of dose calculation accuracy also in presence of magnetic field, making this approach suitable to MRgRT. This accuracy can be improved by using patient-specific RED values.
Databáze: OpenAIRE
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