OSL films for in-vivo entrance dose measurements

Purpose: Having previously reviewed the implementation of systematic in vivo dosimetry at the Norfolk and Norwich Hospital this paper examines the results of entrance dose measurements for specific sites/techniques and determines whether different action/alert protocols are required for these different categories.Methods and materials: Entrance dose measurements using p-type diodes were analysed for the following treatment categories: Breast, head and neck in beam direction shell, abdomino-pelvic and intrathoracic. A 4% tolerance was applied.Results: Mean deviations from expected dose and proportion of measurements exceeding tolerance were: Breast: +1.15%±3.04% (1SD), 238/1073≥4%; Head and neck: +0.35%±2.20% (1SD), 21/326≥4%; Abdomino-pelvic: +0.52%±2.75% (1SD), 93/712≥4%; Intrathoracic: −0.01%±2.75% (1SD), 22/119≥4%. Significant improvements in results for breast patients were noted following the introduction of a commercial breast board. The results for abdomino-pelvic patients confirmed a substantial variation in diode response under short FSD, wedged fields at 16MV (that had not been corrected for). The statistical uncertainty in dose measurement for each treatment category was calculated in order to assist determination of appropriate tolerance levels.Conclusions: A blanket tolerance of 4% was generally too low given the extent of measurement uncertainty. The relatively high number of readings outside tolerance where identification of errors was difficult/impossible resulted in inconsistent application of the action protocol. Some widening of tolerances is likely to improve quality of procedure and treatment. Appropriate action levels are recommended for each treatment category.

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Correction factors in in-vivo dosimetry. With reference to entrance dose measurements

Radiotherapy and Oncology ◽

10.1016/0167-8140(96)80505-6 ◽

1995 ◽

Vol 37 ◽

pp. S19 ◽

Cited By ~ 2

Author(s):

Rikner Göran ◽

Grusell Erik

Keyword(s):

In Vivo Dosimetry ◽

Correction Factors ◽

Entrance Dose ◽

Dose Measurements

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Quality assurance in radiotherapy by in vivo dosimetry. 1. Entrance dose measurements, a reliable procedure

Radiotherapy and Oncology ◽

10.1016/0167-8140(90)90102-3 ◽

1990 ◽

Vol 17 (2) ◽

pp. 141-151 ◽

Cited By ~ 115

Author(s):

G. Leunens ◽

J. Van Dam ◽

A. Dutreix ◽

E. van der Schueren

Keyword(s):

Quality Assurance ◽

In Vivo Dosimetry ◽

Entrance Dose ◽

Reliable Procedure ◽

Dose Measurements

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

Journal of Applied Clinical Medical Physics ◽

10.1120/1.308253 ◽

2000 ◽

Vol 1 (3) ◽

pp. 100 ◽

Cited By ~ 23

Author(s):

X. R. Zhu

Keyword(s):

Correction Factors ◽

Silicon Diode ◽

Entrance Dose ◽

Dose Measurements

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A clinical implementation of in vivo dosimetry with n-type Isorad semiconductor diodes

Nuclear Technology and Radiation Protection ◽

10.2298/ntrp1404313r ◽

2014 ◽

Vol 29 (4) ◽

pp. 313-320

Author(s):

Laza Rutonjski ◽

Borislava Petrovic ◽

Milutin Baucal ◽

Milan Teodorovic ◽

Ozren Cudic ◽

...

Keyword(s):

Quality Assurance ◽

Mean Value ◽

In Vivo Dosimetry ◽

Quality Assurance Program ◽

Clinical Implementation ◽

Entrance Dose ◽

Dose Measurements ◽

Action Levels ◽

Radiotherapy Treatment

The study was aimed to check the radiotherapy treatment accuracy and definition of action levels during implementation of in vivo dosimetry as a part of quality assurance program. The calibration and correction factors for in vivo entrance dose measurements for six n-type Isorad semiconductor diodes were determined as recommended by the European Society for Radiotherapy and Oncology Booklet No. 5. The patients for in vivo measurements have been divided in groups, according to the treatment site/techique, in order to investigate and detect the groups where the uncertainty was larger or where a systematic error occurred. The tolerance/action levels for all groups were also defined and checked. In this study, the entrance dose measurements were performed for total of 451 treatment fields, and 338 patients over one year period. The mean value and the standard deviation for different groups were: breast +1.0% ? 2.89%(1 SD), brain, and head and neck - +0.74% ? 2.04%(1 SD), and isocentric pelvis and abdomen - +0.1% ? 2.86%(1 SD). All measurements - +0.72% ? 2.64%(1 SD). In our experience, systematic in vivo dosimetry proved to be a very useful tool for quality assurance of patient's plan and treatment, both in detecting systematic errors and for estimating the accuracy of radiotherapy treatment delivery.

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Systematic in vivo dosimetry for quality assurance using diodes. Part 1: Experiences and results of the implementation of entrance dose measurements

Journal of Radiotherapy in Practice ◽

10.1017/s1460396903000542 ◽

2003 ◽

Vol 3 (4) ◽

pp. 185-196 ◽

Cited By ~ 1

Author(s):

R. Appleyard ◽

K. Ball ◽

F.E. Hughes ◽

W. Kilby ◽

S. Lassen ◽

...

Keyword(s):

Calibration Procedure ◽

In Vivo Dosimetry ◽

Mean Deviation ◽

Factors Affecting ◽

Entrance Dose ◽

Dosimetric Accuracy ◽

Single Field ◽

Diode System ◽

Dose Measurements

Purpose: This paper describes our experiences of implementing systematic in vivo dosimetry at the Norfolk and Norwich Hospital and reviews the results of 2,254 entrance dose measurements made over a 17-month period.Methods and materials: Entrance dose measurements using p-type diodes were performed on all new planned patients. The calibration procedure and correction factors applied are described. A 4% tolerance was applied.Results: The results of all measurements indicated a small mean deviation from expected entrance dose of 10.77% and a standard deviation of 2.85%. 16.7% of all measurements exceeded the 4% tolerance with 9.2% exceeding a 5% level. The estimated overall errors for 578 treatments were calculated using the weighted averages of all beams. A narrower SD of 1.96% combined with only 4.8% of all treatments exceeding a 4% tolerance show that large deviations from a single field do not always translate into significant overall errors.Conclusions: Global dosimetric accuracy was within clinically acceptable limits and variations between measured and expected doses were mainly attributable to factors affecting diode reading. A number of errors in calculating deviations and the inconsistent application of the protocol suggest the need for interfacing the diode system with software control.

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Rectal and Bladder Dose Measurements in the Intracavitary Applications of Cervical Cancer Treatment with HDR Afterloading System: Comparison of TPS Data with MOSFET Detector

Journal of Biomedical Physics and Engineering ◽

10.31661/jbpe.v0i0.1065 ◽

2019 ◽

Author(s):

N Singh ◽

Sh Ahamed ◽

A Sinha ◽

Sh Srivastava ◽

N K Painuly ◽

...

Keyword(s):

High Dose Rate ◽

In Vivo Dosimetry ◽

Intracavitary Brachytherapy ◽

High Dose ◽

Gradient Fields ◽

Calculated Dose ◽

Mosfet Detector ◽

Dose Measurements

Background: Intracavitary brachytherapy plays a major role in management of cervical carcinoma. Assessment of dose received by OAR’s therefore becomes crucial for the estimation of radiation toxicities in high dose rate brachytherapy.Objective: The purpose of this study is to evaluate the role of in vivo dosimetry in HDR brachytherapy and to compare the actual doses delivered to OAR’s with those calculated during treatment planning.Materials and Methods: A total of 50 patients were treated with Microselectron HDR. Out of 50 patients, 26 were treated with a dose of 7 Gy and 24 with a dose of 9 Gy, prescribed to point A. Brachytherapy planning and evaluation of dose to the bladder and rectum was done on TPS & in vivo dosimetry was performed using portable MOSFET.Results: The calibration factors calculated for both the dosimeters are almost equal and are 0.984 cGy/mV and 1.0895 cGy/mV. For bladder, dose deviation was found to be within +/- 5% in 28 patients, +/- 5-10% in 14 patients, +/- 10-15% in 4 patients. The deviation between the TPS-calculated dose and the dose measured by MOSFET for rectum was within +/- 5% in 31 patients, +/- 5–10% in 8 patients, and +/- 10–15% in 7 patients.Conclusion: TPS calculated doses were slightly higher than that measured by MOSFET. The use of a small size of MOSFET dosimeter is an efficient method for accurately measuring doses in high-dose gradient fields typically seen in brachytherapy. Therefore, to reduce risk of large errors in the dose delivery, in vivo dosimetry can be done in addition to TPS computations.

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