Transit and non‐transit 3D <scp>EPID</scp> dosimetry versus detector arrays for patient specific <scp>QA</scp>

Olaciregui-Ruiz, Ígor; Vivas-Maiques, Begoña; Kaas, J.; Perik, T.; Wittkämper, F.W.; Mijnheer, Ben J.; Mans, A.

doi:10.1002/acm2.12610

Cited by 28 publications

(34 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, it is often not possible to use these in combination with Intensity Modulated Radiation Therapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT) for which verification is limited to pre-treatment solutions. Since Electronic Portal Imaging Device (EPID) images contain dose information, many groups have investigated their use for radiotherapy dose measurement [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] . Pre-treatment dose verification and in-vivo dosimetry using EPIDs has become routine practice in a growing number of clinics in recent years.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of automated pre-treatment and transit in-vivo dosimetry in radiotherapy using empirically determined parameters

Bossuyt

Weytjens

Nevens

et al. 2020

Physics and Imaging in Radiation Oncology

View full text Add to dashboard Cite

Background and purpose: First reports on clinical use of commercially automated systems for Electronic Portal Imaging Device (EPID)-based dosimetry in radiotherapy showed the capability to detect important changes in patient setup, anatomy and external device position. For this study, results for more than 3000 patients, for both pre-treatment verification and in-vivo transit dosimetry were analyzed. Materials and methods: For all Volumetric Modulated Arc Therapy (VMAT) plans, pre-treatment quality assurance (QA) with EPID images was performed. In-vivo dosimetry using transit EPID images was analyzed, including causes and actions for failed fractions for all patients receiving photon treatment (2018)(2019). In total 3136 and 32,632 fractions were analyzed with pre-treatment and transit images respectively. Parameters for gamma analysis were empirically determined, balancing the rate between detection of clinically relevant problems and the number of false positive results. Results: Pre-treatment and in-vivo results depended on machine type. Causes for failed in-vivo analysis included deviations in patient positioning (32%) and anatomy change (28%). In addition, errors in planning, imaging, treatment delivery, simulation, breath hold and with immobilization devices were detected. Actions for failed fractions were mostly to repeat the measurement while taking extra care in positioning (54%) and to intensify imaging procedures (14%). Four percent initiated plan adjustments, showing the potential of the system as a basis for adaptive planning. Conclusions: EPID-based pre-treatment and in-vivo transit dosimetry using a commercially available automated system efficiently revealed a wide variety of deviations and showed potential to serve as a basis for adaptive planning.

show abstract

Section: Introductionmentioning

confidence: 99%

Evaluation of automated pre-treatment and transit in-vivo dosimetry in radiotherapy using empirically determined parameters

Bossuyt

Weytjens

Nevens

et al. 2020

Physics and Imaging in Radiation Oncology

View full text Add to dashboard Cite

show abstract

“…For example, thermoluminescent detectors (TLDs) are only capable of point measurement (measuring of the dose on the patient's skin) and films are limited to two‐dimensional (2D) measurements. Recent studies have demonstrated the use of electronic portal imaging devices (EPIDs) as 3D patient‐specific dosimetry tools; however they are associated with uncertainties in the calibration process along with uncertainties in various steps of the dose reconstruction process . Therefore, the implementation of adaptive radiotherapy is limited by the lack of a real‐time device that can accurately measure the delivered dose to the patient …”

Section: Introductionmentioning

confidence: 99%

“…Recent studies have demonstrated the use of electronic portal imaging devices (EPIDs) as 3D patient-specific dosimetry tools; 8,9 however they are associated with uncertainties in the calibration process along with uncertainties in various steps of the dose reconstruction process. 10,11 Therefore, the implementation of adaptive radiotherapy is limited by the lack of a real-time device that can accurately measure the delivered dose to the patient. 3,7,12 The x-ray acoustic (XA) effect has recently been proposed as a method for real-time 3D in-vivo dosimetry using x-ray acoustic computed tomography (XACT).…”

Section: Introductionmentioning

confidence: 99%

Simulation of x‐ray‐induced acoustic imaging for absolute dosimetry: Accuracy of image reconstruction methods

et al. 2020

View full text Add to dashboard Cite

Purpose Three‐dimensional in‐vivo dose verification is one of the standing challenges in radiation therapy. X‐ray‐induced acoustic tomography has recently been proposed as an imaging method for use in in‐vivo dosimetry. The aim of this study was to investigate the accuracy of reconstructing three‐dimensional (3D) absolute dose using x‐ray‐induced acoustic tomography. We performed this investigation using two different tomographic dose reconstruction techniques. Methods Two examples of 3D dose reconstruction techniques for x‐ray acoustic imaging are investigated. Dose distributions are calculated for varying field sizes using a clinical treatment planning system. The induced acoustic pressure waves which are generated by the increase in temperature due to the absorption of pulsed MV x‐rays are simulated using an advanced numerical modeling package for acoustic wave propagation in the time domain. Two imaging techniques, back projection and iterative time reversal, are used to reconstruct the 3D dose distribution in a water phantom with open fields. Image analysis is performed and reconstructed depth dose curves from x‐ray acoustic imaging are compared to the depth dose curves calculated from the treatment planning system. Calculated field sizes from the reconstructed dose profiles by back projection and time reversal are compared to the planned field size to determine their accuracy. The iterative time reversal imaging technique is also used to reconstruct dose in an example clinical dose distribution. Image analysis of this clinical test case is performed using the gamma passing rate. In addition, gamma passing rates are used to validate the stopping criteria in the iterative time reversal method. Results Water phantom simulations showed that back projection does not adequately reconstruct the shape and intensity of the depth dose. When compared to the depth of maximum dose calculated by a treatment planning system, the maximum dose depth by back projection is shifted deeper by 55 and 75 mm for 4 × 4 cm and 10 × 10 cm field sizes, respectively. The reconstructed depth dose by iterative time reversal accurately agrees with the planned depth dose for a 4 × 4 cm field size and is shifted deeper by 12 mm for the 10 × 10 cm field size. When reconstructing field sizes, the back projection method leads to 18% and 35% larger sizes for the 4 × 4 cm and 10 × 10 cm fields, respectively, whereas the iterative time reversal method reconstructs both field sizes with < 2% error. For the clinical dose distribution, we were able to reconstruct the dose delivered by a 1 degree sub‐arc with a good accuracy. The reconstructed and planned doses were compared using gamma analysis, with> 96% gamma passing rate at 3%/2 mm. Conclusions Our results show that the 3D x‐ray acoustic reconstructed dose by iterative time reversal is considerably more accurate than the dose reconstructed by back projection. Iterative time reversal imaging has a potential for use in 3D absolute dosimetry.

show abstract

“…Measurement of a dose or fluence map, taking into account the patient's body, is called transit dosimetry. 11 The aforementioned common use of portal matrices allows to check the dose distribution by measuring fluence maps before the therapeutic session without the patient. [12][13][14] The parameter adopted for comparing two data sets, including dose distributions or fluence maps, is the gamma coefficient.…”

Section: Introductionmentioning

confidence: 99%

Portal dosimetry in radiotherapy repeatability evaluation

Ślosarek

Plaza

Nas

et al. 2020

J Applied Clin Med Phys

View full text Add to dashboard Cite

The accuracy of radiotherapy is the subject of continuous discussion, and dosimetry methods, particularly in dynamic techniques, are being developed. At the same time, many oncology centers develop quality procedures, including pretreatment and online dose verification and proper patient tracking methods. This work aims to present the possibility of using portal dosimetry in the assessment of radiotherapy repeatability. The analysis was conducted on 74 cases treated with dynamic techniques. Transit dosimetry was made for each collision‐free radiation beam. It allowed the comparison of summary fluence maps, obtained for fractions with the corresponding summary maps from all other treatment fractions. For evaluation of the compatibility in the fluence map pairs (6798), the gamma coefficient was calculated. The results were considered in four groups, depending on the used radiotherapy technique: stereotactic fractionated radiotherapy, breath‐hold, free‐breathing, and conventionally fractionated other cases. The chi2 or Fisher's exact test was made depending on the size of the analyzed set and also Mann–Whitney U‐test was used to compare treatment repeatability of different techniques. The aim was to test whether the null hypothesis of error‐free therapy was met. The patient is treated repeatedly if the P‐value in all the fluence maps sets is higher than the level of 0.01. The best compatibility between treatment fractions was obtained for the stereotactic technique. The technique with breath‐holding gave the lowest percentage of compliance of the analyzed fluence pairs. The results indicate that the repeatability of the treatment is associated with the radiotherapy technique. Treated volume location is also an essential factor found in the evaluation of treatment accuracy. The EPID device is a useful tool in assessing the repeatability of radiotherapy. The proposed method of fluence maps comparison also allows us to assess in which therapeutic session the patient was treated differently from the other fractions.

show abstract

Transit and non‐transit 3D EPID dosimetry versus detector arrays for patient specific QA

Cited by 28 publications

References 41 publications

Evaluation of automated pre-treatment and transit in-vivo dosimetry in radiotherapy using empirically determined parameters

Evaluation of automated pre-treatment and transit in-vivo dosimetry in radiotherapy using empirically determined parameters

Simulation of x‐ray‐induced acoustic imaging for absolute dosimetry: Accuracy of image reconstruction methods

Portal dosimetry in radiotherapy repeatability evaluation

Contact Info

Product

Resources

About