Artefacts in multi-echoT2imaging for high-precision gel dosimetry: II. Analysis ofB1-field inhomogeneity

Deene, Yves De; Wagter, Carlos De; Neve, Wilfried De; Achten, Eric

doi:10.1088/0031-9155/45/7/308

Cited by 69 publications

(43 citation statements)

References 43 publications

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“…Whereas T 2 -weighted images are used in the clinic, a collection of these images are used to calculate R 2 maps. Although theoretically, the use of T 1− or T 2− weighted images is not excluded, it is found that main magnetic field ( B 0 ) (De Deene et al 2001a) radio-frequency field ( B 1 ) (De Deene et al 2000b) inhomogeneities have a detrimental impact on the accuracy of the dose reading. These effects are largely compensated by the use of quantitative R 2 maps as these effects are in first order proportional to the signal intensity.…”

Section: Evaluation Of Polymer Gel Dosimetersmentioning

confidence: 99%

Polymer gel dosimetry

et al. 2010

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Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.

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Section: Evaluation Of Polymer Gel Dosimetersmentioning

confidence: 99%

Polymer gel dosimetry

et al. 2010

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“…64,207,[228][229][230] In particular, attention is required to minimize uncertainties that originate from the technical challenges of controlling magnetic field uniformity and gradients with sufficient precision, avoiding MRI sequences that cause excessive temperature increase associated with RF energy deposited in the gel during MR imaging. 228 For MR measurements requiring high accuracy and highspatial resolution, long imaging times ͑several hours͒ may be required to achieve the low uncertainty and high spatial resolution associated with standard dosimeters.…”

Section: Vb3 Readout Techniquesmentioning

confidence: 99%

Dosimetry tools and techniques for IMRT

et al. 2011

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Intensity modulated radiation therapy ͑IMRT͒ poses a number of challenges for properly measuring commissioning data and quality assurance ͑QA͒ radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of dosimeters, from secondary standards to field instruments, is established to assure the quantitative nature of the tests. This report is intended to describe the characteristics of the components of these systems; dosimeters, phantoms, and dose evaluation algorithms. This work is the report of AAPM Task Group 120.

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“…The main advantage of this evaluation technique is that limited access to MRI facilities is not an issue or is the need to build or purchase specialized optical scanning equipment. It should be noted that where, for instance, MRI has evaluation problems such as in homogeneities or temperature dependence (De Deene et al, 2000a, 2000bDe Deene & Wagter, 2001), x-ray CT evaluation has its own limitations. However, as is the case with MRI evaluation of polymer gel dosimeters , it has been shown that x-ray CT evaluation techniques require the CT scanner be commissioned specifically for gel dosimetry before use (Hill et al, 2005).…”

Section: X-ray Ct Scanningmentioning

confidence: 99%