Quality assurance in radiotherapy by in vivo dosimetry. 2. Determination of the target absorbed dose

Leunens, G.; Dam, J. Van; Dutreix, A.; Schueren, Emmanuel van der

doi:10.1016/0167-8140(90)90167-u

Cited by 103 publications

(40 citation statements)

References 12 publications

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“…The desired midline dose is calculated from the midline dose that was derived from the curve, and the measured entrance dose. Leunen et al 17 introduced a correction factor that allows assessing the dose at any depth, calculated as the ratio of the water-equivalent patient thickness and the actual patient thickness extracted from the patient computed tompography (CT) contour. We used this factor to calculate the dose at the isocenter.…”

Section: In Vivo Dosimetrymentioning

confidence: 99%

Implementation of in vivo Dosimetry with Isorad™ Semiconductor Diodes in Radiotherapy Treatments of the Pelvis

Rodríguez¹,

Abrego²,

Pineda³

2008

Medical Dosimetry

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Section: In Vivo Dosimetrymentioning

confidence: 99%

Implementation of in vivo Dosimetry with Isorad™ Semiconductor Diodes in Radiotherapy Treatments of the Pelvis

Rodríguez¹,

Abrego²,

Pineda³

2008

Medical Dosimetry

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“…Leunens et a1. 1 emphasized that the transmission measurements are very useful to evaluate the uncertainties related to patient data such as contour errors and tissue inhomogenities as well as to the algorithms of the treatment planning system. The exit dose measurements in principle could be made in external beam radiotherapy during every fraction because no perturbations of the tumor dose will result 2 .…”

Section: Introductionmentioning

confidence: 99%

A simplified approach for exit dose in vivo measurements in radiotherapy and its clinical application

Banjade

Shrestha

Shukri

et al. 2002

Australas. Phys. Eng. Sci. Med.

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This is a study using LiF:Mg;Ti thermoluminescent dosimeter (TLD) rods in phantoms to investigate the effect of lack of backscatter on exit dose. Comparing the measured dose with anticipated dose calculated using tissue maximum ratio (TMR) or percentage depth dose (PDD) gives rise to a correction factor. This correction factor may be applied to in-vivo dosimetry results to derive true dose to a point within the patient. Measurements in a specially designed humanoid breast phantom as well as patients undergoing radiotherapy treatment were also been done. TLDs with reproducibility of within +/- 3% (1 SD) are irradiated in a series of measurements for 6 and 10 MV photon beams from a medical linear accelerator. The measured exit doses for the different phantom thickness for 6 MV beams are found to be lowered by 10.9 to 14.0% compared to the dose derived from theoretical estimation (normalized dose at dmax). The same measurements for 10 MV beams are lowered by 9.0 to 13.5%. The variations of measured exit dose for different field sizes are found to be within 2.5%. The exit doses with added backscatter material from 2 mm up to 15 cm, shows gradual increase and the saturated values agreed within 1.5% with the expected results for both beams. The measured exit doses in humanoid breast phantom as well as in the clinical trial on patients undergoing radiotherapy also agreed with the predicted results based on phantom measurements. The authors' viewpoint is that this technique provides sufficient information to design exit surface bolus to restore build down effect in cases where part of the exit surface is being considered as a target volume. It indicates that the technique could be translated for in vivo dose measurements, which may be a conspicuous step of quality assurance in clinical practice.

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“…Such an in‐vivo dose measurement can be performed as entrance dose only and entrance and exit dose determinations 2 11 The entrance dose only in‐vivo dosimetry program can effectively provide an overall check of the dosimetry and treatment delivery processes, including monitoring unit calculations, patient setup, and proper treatment accessories and field size being used 9 . With entrance and exit dose measurements, additional errors, including changes in patient thickness, contouring errors, and problems with CT data transfer, can be detected 3 …”

Section: Introductionmentioning

confidence: 99%

“…With entrance and exit dose measurements, additional errors, including changes in patient thickness, contouring errors, and problems with CT data transfer, can be detected 3 7 , 9 In our clinical practices, diode detectors have been used for measuring entrance doses only for treatment quality assurance. For an ideal detector, the entrance dose (maximum dose,

D_{max}

, in cGy) can be directly derived from reading a calibrated diode.…”

Section: Introductionmentioning

confidence: 99%

Entrance dose measurements for in‐vivo diode dosimetry: Comparison of correction factors for two types of commercial silicon diode detectors

Zhu

2000

J Applied Clin Med Phys

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Silicon diode dosimeters have been used routinely for in‐vivo dosimetry. Despite their popularity, an appropriate implementation of an in‐vivo dosimetry program using diode detectors remains a challenge for clinical physicists. One common approach is to relate the diode readout to the entrance dose, that is, dose to the reference depth of maximum dose such as dmax for the 10×10 cm2 field. Various correction factors are needed in order to properly infer the entrance dose from the diode readout, depending on field sizes, target‐to‐surface distances (TSD), and accessories (such as wedges and compensate filters). In some clinical practices, however, no correction factor is used. In this case, a diode‐dosimeter‐based in‐vivo dosimetry program may not serve the purpose effectively; that is, to provide an overall check of the dosimetry procedure. In this paper, we provide a formula to relate the diode readout to the entrance dose. Correction factors for TSD, field size, and wedges used in this formula are also clearly defined. Two types of commercial diode detectors, ISORAD (n‐type) and the newly available QED (p‐type) (Sun Nuclear Corporation), are studied. We compared correction factors for TSDs, field sizes, and wedges. Our results are consistent with the theory of radiation damage of silicon diodes. Radiation damage has been shown to be more serious for n‐type than for p‐type detectors. In general, both types of diode dosimeters require correction factors depending on beam energy, TSD, field size, and wedge. The magnitudes of corrections for QED (p‐type) diodes are smaller than ISORAD detectors.PACS number(s): 87.66.–a, 87.52.–g

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Quality assurance in radiotherapy by in vivo dosimetry. 2. Determination of the target absorbed dose

Cited by 103 publications

References 12 publications

Implementation of in vivo Dosimetry with Isorad™ Semiconductor Diodes in Radiotherapy Treatments of the Pelvis

Implementation of in vivo Dosimetry with Isorad™ Semiconductor Diodes in Radiotherapy Treatments of the Pelvis

A simplified approach for exit dose in vivo measurements in radiotherapy and its clinical application

Entrance dose measurements for in‐vivo diode dosimetry: Comparison of correction factors for two types of commercial silicon diode detectors

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