Observer uncertainties of soft tissue‐based patient positioning in IGRT

Purpose There remain uncertainties due to inter‐ and intraobserver variability in soft‐tissue‐based patient positioning even with the use of image‐guided radiation therapy (IGRT). This study aimed to reveal observer uncertainties of soft‐tissue‐based patient positioning on cone‐beam computed tomogra...

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Bibliographic Details
Published in:Journal of applied clinical medical physics 2020-02, Vol.21 (2), p.73-81
Main Authors: Hirose, Taka‐aki, Arimura, Hidetaka, Fukunaga, Jun‐ichi, Ohga, Saiji, Yoshitake, Tadamasa, Shioyama, Yoshiyuki
Format: Article
Language:English
Subjects:
Aged
Aged, 80 and over
Antigens
Cancer therapies
Cone-Beam Computed Tomography
Humans
interobserver variation
intraobserver variation
Male
Middle Aged
Models, Statistical
Observer Variation
Patient Positioning
Prostate cancer
prostate cancer image‐guided radiation therapy
Prostatic Neoplasms - diagnostic imaging
PTV margin
Radiation Oncology Physics
Radiation therapy
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Image-Guided - methods
Radiotherapy, Intensity-Modulated - methods
Registration
Reproducibility of Results
Retrospective Studies
soft‐tissue‐based patient positioning
Studies
Tomography
Tomography, X-Ray Computed
Uncertainty
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Summary:Purpose There remain uncertainties due to inter‐ and intraobserver variability in soft‐tissue‐based patient positioning even with the use of image‐guided radiation therapy (IGRT). This study aimed to reveal observer uncertainties of soft‐tissue‐based patient positioning on cone‐beam computed tomography (CBCT) images for prostate cancer IGRT. Methods Twenty‐six patients (7–8 fractions/patient, total number of 204 fractions) who underwent IGRT for prostate cancer were selected. Six radiation therapists retrospectively measured prostate cancer location errors (PCLEs) of soft‐tissue‐based patient positioning between planning CT (pCT) and pretreatment CBCT (pre‐CBCT) images after automatic bone‐based registration. Observer uncertainties were evaluated based on residual errors, which denoted the differences between soft‐tissue and reference positioning errors. Reference positioning errors were obtained as PCLEs of contour‐based patient positioning between pCT and pre‐CBCT images. Intraobserver variations were obtained from the difference between the first and second soft‐tissue‐based patient positioning repeated by the same observer for each fraction. Systematic and random errors of inter‐ and intraobserver variations were calculated in anterior–posterior (AP), superior–inferior (SI), and left–right (LR) directions. Finally, clinical target volume (CTV)‐to‐planning target volume (PTV) margins were obtained from systematic and random errors of inter‐ and intraobserver variations in AP, SI, and LR directions. Results Interobserver variations in AP, SI, and LR directions were 0.9, 0.9, and 0.5 mm, respectively, for the systematic error, and 1.8, 2.2, and 1.1 mm, respectively, for random error. Intraobserver variations were
ISSN:1526-9914
1526-9914
DOI:10.1002/acm2.12817