A deformable head and neck phantom with in‐vivo dosimetry for adaptive radiotherapy quality assurance. Issue 4 (11th March 2015)

• Record Type: Journal Article
• Authors: Graves, Yan Jiang; Smith, Arthur‐Allen; McIlvena, David; Manilay, Zherrina; Lai, Yuet Kong; Rice, Roger; Mell, Loren; Jia, Xun; Jiang, Steve B.; Cerviño, Laura
• Is Part Of: Medical physics. Volume 42:Issue 4(2015)
• Page Start: 1490
• Page End: 1497
• Publication Date: 2015-03-11
• Subjects: biomechanics -- computerised tomography -- deformation -- dosimetry -- image registration -- medical image processing -- phantoms -- quality assurance -- radiation therapy -- tumours; Dose‐volume analysis -- Mechanical and electrical properties of tissues and organs -- Biomechanics -- Registration -- Computed tomography; Computerised tomographs -- Radiation therapy -- Biological material, e.g. blood, urine; Haemocytometers -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general -- Scintigraphy; deformable registration -- adaptive radiotherapy -- deformable phantom -- deformable registration verification -- ART verification; Cancer -- Dosimetry -- Computed tomography -- Tissues -- Adaptive radiation therapy -- Calibration -- Optical images -- Medical image reconstruction; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4908205
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: Patients' interfractional anatomic changes can compromise the initial treatment plan quality. To overcome this issue, adaptive radiotherapy (ART) has been introduced. Deformable image registration (DIR) is an important tool for ART and several deformable phantoms have been built to evaluate the algorithms' accuracy. However, there is a lack of deformable phantoms that can also provide dosimetric information to verify the accuracy of the whole ART process. The goal of this work is to design and construct a deformable head and neck (HN) ART quality assurance (QA) phantom with in vivo dosimetry. Methods: An axial slice of a HN patient is taken as a model for the phantom construction. Six anatomic materials are considered, with HU numbers similar to a real patient. A filled balloon inside the phantom tissue is inserted to simulate tumor. Deflation of the balloon simulates tumor shrinkage. Nonradiopaque surface markers, which do not influence DIR algorithms, provide the deformation ground truth. Fixed and movable holders are built in the phantom to hold a diode for dosimetric measurements. Results: The measured deformations at the surface marker positions can be compared with deformations calculated by a DIR algorithm to evaluate its accuracy. In this study, the authors selected a Demons algorithm as a DIR algorithm example for demonstration purposes. The average error magnitude is 2.1 mm. The point dose measurements from the in vivo diode dosimeters show a good agreement with the calculated doses from the treatment planning system with a maximum difference of 3.1% of prescription dose, when the treatment plans are delivered to the phantom with original or deformed geometry. Conclusions: In this study, the authors have presented the functionality of this deformable HN phantom for testing the accuracy of DIR algorithms and verifying the ART dosimetric accuracy. The authors' experiments demonstrate the feasibility of this phantom serving as an end‐to‐end ART QA phantom.