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

2003 ◽  
Vol 3 (4) ◽  
pp. 185-196 ◽  
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.

Systematic in vivo dosimetry for quality assurance using diodes 2: Assessing radiotherapy techniques and developing an appropriate action protocol

2004 ◽  
Vol 4 (4) ◽  
pp. 143-154 ◽  
Author(s):  
R. Appleyard ◽  
K. Ball ◽  
F. E. Hughes ◽  
W. Kilby ◽  
R. Nicholls ◽  
...  
Keyword(s):  
Head And Neck ◽  
In Vivo Dosimetry ◽  
Entrance Dose ◽  
Treatment Category ◽  
P Type ◽  
Dose Measurements ◽  
Action Levels

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.

In vivo dosimetry using radiochromic films (EBT-2) during intraoperative radiotherapy

2016 ◽  
Vol 15 (4) ◽  
pp. 378-384 ◽  
Author(s):  
Zahra Rahimzade Yekta ◽  
Seied Rabi Mehdi Mahdavi ◽  
Hamid Reza Baghani ◽  
Mostafa Robatjazi ◽  
Ahmad Mostaar ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Early Stage ◽  
Intraoperative Radiotherapy ◽  
Surgical Excision ◽  
In Vivo Dosimetry ◽  
Mean Deviation ◽  
Beam Radiation ◽  
Dose Measurements ◽  
Delivered Dose

AbstractBackgroundIntraoperative radiotherapy is a method of choice to deliver a critical radiation dose to the tumour bed immediately after surgical excision.AimThe purpose of this work is to check the dose delivered to the patients during intraoperative electron beam radiation therapy (IOERT) in the conservative treatment of breast cancer, by means of reference dose measurement using radiochromic (EBT-2) films.Material and methodsNinety patients with early-stage breast cancer underwent exclusive IOERT to the tumour bed using a LIAC linear accelerator. Absolute dose measurements were done with film pieces. After irradiation, the pixel values of the films were obtained via MATLAB and ImageJ softwares. Calibration curve was also used for calculating net optical density. Expected dose was compared to the patient delivered dose.ResultsThe mean deviation of the delivered dose from the expected one was 2·56% that is well in the accepted criteria. Only in one case, there was a larger deviation due to barometer miscalibration.FindingsEBT-2 film response is independent from dose-per-pulse and as it was shown in this study it can be robustly used during breast IOERT for dosimetric and also positioning verifications.

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

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.

OSL films for in-vivo entrance dose measurements

2017 ◽  
Vol 106 ◽  
pp. 644-649 ◽  
Author(s):  
S.O. Souza ◽  
F. d'Errico ◽  
B. Azimi ◽  
A. Baldassare ◽  
A.V.S. Alves ◽  
...  
Keyword(s):  
Entrance Dose ◽  
Dose Measurements

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

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.

A survey of in vivo diode dosimetry in the UK

1999 ◽  
Vol 1 (2) ◽  
pp. 73-82
Author(s):  
Robert Appleyard
Keyword(s):  
Quality Assurance ◽  
Central Axis ◽  
In Vivo Dosimetry ◽  
In Vivo Measurements ◽  
Radiotherapy Department ◽  
Critical Organ ◽  
Diode System ◽  
The Uk ◽  
Radiotherapy Physics

A clear rationale exists for routine in vivo dosimetry as part of an overall quality assurance (QA) programme within a radiotherapy department. A survey was undertaken in order to identify the extent of diode dosimetry practice within the UK.Questionnaires were distributed to 57 radiotherapy physics departments in the UK in order to determine the extent of central axis diode dosimetry and the protocols implemented, the range of other in vivo measurements performed using diodes and the type of equipment used. Fifty-four responses were received. Eighteen departments undertook some form of central axis entrance dosimetry. Fifteen departments could be considered to be doing this routinely. Seven departments indicated planned future use. Six centres routinely undertook exit dosimetry with a further 3 indicating planned future use. Varied protocols for use were reported by those centres undertaking central axis dosimetry. Thirty-two respondents used a diode system for other forms of in vivo measurements with critical organ and TBI dosimetry being the most common. The vast majority used Scanditronix equipment.Despite the distinct benefits of central axis diode dosimetry, this continues to be infrequently adopted as part of a departmental QA programme. However, an indication of a number of departments planning to implement such an approach is reassuring.

Calibration of entrance dose measurement for an in vivo dosimetry programme

1995 ◽  
Vol 39 (4) ◽  
pp. 369-374 ◽  
Author(s):  
W Ding ◽  
W Patterson ◽  
L Tremethick ◽  
D Joseph
Keyword(s):  
In Vivo Dosimetry ◽  
Dose Measurement ◽  
Entrance Dose

scholarly journals Total skin electron beam therapy rationalization and utility of in vivo dosimetry in a high-volume centre

BJR|Open ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 20190008
Author(s):  
Sarah Misson-Yates ◽  
Marium Naeem ◽  
Isabel Palmer ◽  
Eleanor Holden ◽  
Owen Hedley ◽  
...  
Keyword(s):  
Electron Beam ◽  
Standard Deviation ◽  
High Volume ◽  
In Vivo Dosimetry ◽  
Thermoluminescent Dosimeter ◽  
Electron Beam Therapy ◽  
Point Reduction ◽  
Dosimetric Accuracy ◽  
Significant Change

Objective: This paper reports on the rationalization of a substantial pool of in vivo dosimetry (IVD) data from patients treated with total skin electron beam therapy (TSEBT) and the application of this to verify the accurate delivery of TSEBT when changing linac manufacturer. Methods: Thermoluminescent dosimeter IVD data from 149 patients were analyzed comparing the population mean and standard deviation for each site. The number of sites required to confirm the prescribed dose were reviewed considering both dosimetric and clinical relevance. The reduced sites were then used to assess the continued dosimetric accuracy on new equipment and the results were compared statistically using the Mann–Witney test. Results: The trunk dose measurement points were reduced from nine to six and five extra trunk sites were identified and reviewed clinically prior to removal. Following change in manufacturer the trunk dose points showed no statistically significant change and confirmed that patients had received within 1.3% of the intended mean trunk dose using both delivery methods. A statistically significant change in 4 out of the 13 extra trunk sites was seen following the move to the new centre. However, all but one site showed a change of less than 1 standard deviation. Conclusion: The total number of measurement points per patient were reduced from 27 to 19 which constituted a 25% saving in preparation and read out. Accurate delivery of prescribed dose was confirmed following measurement point reduction for treatments delivered on linacs from two different manufacturers. Advances in knowledge: Proven methodology for rationalization of IVD measurements for TSEBT

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