Characterization of an <i>in vivo</i> diode dosimetry system for clinical use

Huang, Kai; Bice, William S.; Hidalgo-Salvatierra, O.

doi:10.1120/jacmp.v4i2.2528

Cited by 15 publications

(9 citation statements)

References 16 publications

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“…who reported that since it is difficult to put the diode dosimeter at the central axis accurately, a larger tolerance should be considered for wedged fields when performing in vivo dosimetry. [ 11 ]…”

Section: Discussionmentioning

confidence: 99%

“…These consist of the measurement of calibration and correction factors (CFs), checking the system, methodology and the use of the factors in practice; and clinical pilot studies to establish the existing accuracy and precision of given treatment situation. [ 11 – 13 ] The ideal diode for in vivo dosimetry should show minimal dependence on field size, source–skin distance (SSD) and interposition of modifying devices such as wedges. [ 1 4 14 ] CFs need to be modified with accumulating dose.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy

Allahverdi¹,

Mohammadkarim²,

Esfehani³

et al. 2012

J Med Phys

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An in vivo dosimetry system, using p-type diode dosimeters, was characterized for clinical applications of treatment machines ranging in megavoltage energies. This paper investigates two different models of diodes for externally wedged beams and explains a new algorithm for the calculation of the target dose at various tissue depths in external radiotherapy. The values of off-axis wedge correction factors were determined at two different positions in the wedged (toward the thick and thin edges) and in the non-wedged directions on entrance and exit surfaces of a polystyrene phantom in 60Co and 6 MV photon beams. Depth transmission was defined on the entrance and exit surfaces to obtain the off-axis wedge correction factor at any depth. As the sensitivity of the diodes depends on physical characteristics [field size, source–skin distance (SSD), thickness, backscatter], correction factors were applied to the diode reading when measuring conditions different from calibration situations. The results indicate that needful correction factors for 60Co wedged photons are usually larger than those for 6 MV wedged photon beams. In vivo dosimetry performed with the proposed algorithms at externally wedged beams has negligible probable errors (less than 0.5&) and is a reliable method for patient dose control.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy

Allahverdi¹,

Mohammadkarim²,

Esfehani³

et al. 2012

J Med Phys

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“…The difference in electronic contamination and scatter radiation received by a diode on the surface and an ionization chamber at

d_{max}

causes a variation in CFs with field size (31) . Both ascending and descending variation of CFs with field size are reported for different diodes at various energies 3 , 28 , 32 . In this study, the field size CF for both diodes had ascending variation for cobalt‐60 and descending variation at 9 MV.…”

Section: Discussionmentioning

confidence: 53%

“…Several investigators have characterized commercial diodes experimentally and measured their CFs at various energies, 3 , 17 , 25 , 27 but there is little published data on such factors for low‐perturbation diodes. Also, to the best of our knowledge, there is no published data on diode characterization for 9 MV photons.…”

Section: Introductionmentioning

confidence: 99%

A Monte Carlo and experimental investigation of the dosimetric behavior of low‐ and medium‐perturbation diodes used for entrance in vivo dosimetry in megavoltage photon beams

Mosleh-Shirazi

Karbasi

Shahbazi‐Gahrouei

et al. 2012

J Applied Clin Med Phys

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Full buildup diodes can cause significant dose perturbation if they are used on most or all of radiotherapy fractions. Given the importance of frequent in vivo measurements in complex treatments, using thin buildup (low‐perturbation) diodes instead is gathering interest. However, such diodes are strictly unsuitable for high‐energy photons; therefore, their use requires evaluation and careful measurement of correction factors (CFs). There is little published data on such factors for low‐perturbation diodes, and none on diode characterization for 9 MV X‐rays. We report on MCNP4c Monte Carlo models of low‐perturbation (EDD5) and medium‐perturbation (EDP10) diodes, and a comparison of source‐to‐surface distance, field size, temperature, and orientation CFs for cobalt‐60 and 9 MV beams. Most of the simulation results were within 4% of the measurements. The results suggest against the use of the EDD5 in axial angles beyond ±50° and exceeding the range 0° to +50° tilt angle at 9 MV. Outside these ranges, although the EDD5 can be used for accurate in vivo dosimetry at 9 MV, its CF variations were found to be 1.5–7.1 times larger than the EDP10 and, therefore, should be applied carefully. Finally, the MCNP diode models are sufficiently reliable tools for independent verification of potentially inaccurate measurements.PACS numbers: 87.10.Rt; 87.50.cm; 87.55.km; 87.56.Fc

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“…In vivo measurements are performed at several locations, with these measurements requiring high spatial resolution, high sensitivity, and low dose influence, over a broad range of doses. Silicon diodes, Gafchromic films, metal-oxide-semiconductor field-effect transistors (MOSFETs), and thermoluminescence detectors (TLDs) are all currently used as in vivo dosimetric tools [8][9][10][11][12][13][14]. These sensors each have their own inherent advantages and disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of radio-photoluminescence glass dosimeters to accumulated doses

et al. 2020

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Background This study investigated the effect of accumulated doses on radio-photoluminescence glass dosimeters (RPLGDs) from measurements involving mega-voltage photons. Methods Forty-five commercially available RPLGDs were irradiated to estimate their dose responses. Photon beams of 6, 10, and 15 MV were irradiated onto the RPLGDs inside a phantom, which were divided into five groups with different doses and energies. Groups 1 and 2 were irradiated at 1, 5, 10, 50, and 100 Gy in a sequential manner; Group 3 was irradiated 10 times with a dose of 10 Gy; and Groups 4 and 5 followed the same method as that of Group 3, but with doses of 50 Gy and 100 Gy, respectively. Each device was subjected to a measurement reading procedure each time irradiation. Results For the annealed Group 1, RPLGD exhibited a linearity response with variance within 5%. For the non-annealed Group 2, readings demonstrated hyperlinearity at 6 MV and 10 MV, and linearity at 15 MV. Following the 100 Gy irradiation, the readings for Group 2 were 118.7 ± 1.9%, 112.2 ± 2.7%, and 101.5 ± 2.3% at 6, 10, and 15 MV, respectively. For Groups 3, 4, and 5, the responsiveness of the RPLGDs gradually decreased as the number of repeated irradiations increased. The percentage readings for the 10th beam irradiation with respect to the readings for the primary beam irradiation were 84.6 ± 1.9%, 87.5 ± 2.4%, and 93.0 ± 3.0% at 6 MV, 10 MV, and 15 MV, respectively. Conclusions The non-annealed RPLGD response to dose was hyperlinear for the 6 MV and 10 MV photon beams but not for the 15 MV photon beam. Additionally, the annealed RPLGD exhibited a fading phenomenon when the measurement was repeated several times and demonstrated a relatively large fading effect at low energies than at high energies.

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Characterization of an in vivo diode dosimetry system for clinical use

Cited by 15 publications

References 16 publications

Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy

Evaluation of off-axis wedge correction factor using diode dosimeters for estimation of delivered dose in external radiotherapy

A Monte Carlo and experimental investigation of the dosimetric behavior of low‐ and medium‐perturbation diodes used for entrance in vivo dosimetry in megavoltage photon beams

Sensitivity of radio-photoluminescence glass dosimeters to accumulated doses

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