Comparison of gamma- and DVH-based in vivo dosimetric plan evaluation for pelvic VMAT treatments

Bijl, Erik van der; Oers, René F.M. van; Olaciregui-Ruiz, Ígor; Mans, A.

doi:10.1016/j.radonc.2017.09.014

Cited by 16 publications

(6 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These gamma metrics have included gamma pass rate, gamma mean value, and max 1% of gamma, to assess errors and patient-related changes. 10,11 The gamma comparison approach has been demonstrated to detect various errors related to the treatment machine as well as the patient. 2 Additionally the gamma approach in vivo has been shown to be sensitive to changes in machine output as well as patient weight change.…”

Section: Introductionmentioning

confidence: 99%

Using in vivo EPID images to detect and quantify patient anatomy changes with gradient dose segmented analysis

et al. 2020

View full text Add to dashboard Cite

Purpose To investigate the utility of gradient dose segmented analysis (GDSA) in combination with in vivo electronic portal imaging device (EPID) images to predict changes in the PTV mean dose for patient cases. Also, we use the GDSA to retrospectively analyze patients treated in our clinic to assess deviations for different treatment sites and use time‐series data to observe any day‐to‐day changes. Methods In vivo EPID transit images acquired on the Varian Halcyon were analyzed for simulated errors in a phantom, including gas bubbles, weight loss, patient shifts, and an arm erroneously in the field. GDSA threshold parameters were tuned to maximize the coefficient of determination (R2) between GDSA metrics and the change in the PTV mean dose (Dmean) as estimated in a treatment planning system (TPS). Similarly for a gamma analysis, the gamma criteria were adjusted to maximize R2 between gamma pass rate and the change in the PTV Dmean from the TPS. The predictive accuracy of these models was tested on patient data measuring the mean and standard deviation of the difference in the predicted change in PTV Dmean and the change in PTV Dmean measured in the TPS. This analysis was extended retrospectively for every patient treated over a 23‐month period (n = 852 patients) to assess the range of expected deviations that occurred during routine clinical operation, as well as to assess any differences between treatment sites. Grouping patients treated on the same day, a time‐series analysis was performed to determine if GDSA metrics could add value in tracking machine behavior over time. Results For the phantom data, analyzing the errors, except for shifts, and comparing the change in PTV Dmean and GDSA mean, a maximal R2 = 0.90 was found for a dose threshold of 5% and gradient threshold of 3 mm. For the gamma approach a linear fit between the gamma pass rate for change in the PTV Dmean was assessed for different criteria, using the same image data. A maximal, R2 = 0.84 was found for a gamma criteria of 3%/3 mm, 45% lower dose threshold. For patient data, the predictive accuracy of the change in the PTV Dmean using the GDSA approach and the gamma approach was 0.09 ± 0.98 % and − 0.65 ± 2.21%, respectively. Comparing the two approaches the accuracy did not significantly differ (P = 0.38), whereas the precision of the GDSA prediction is significantly less (P < 0.001). The dosimetric impact of shifts was not detectable with either the GDSA or gamma approach. Analysis of all patients treated over 23 months showed that over 95% of fractions treated deviated from the first fraction by 2% or less. Deviations> 2% occurred most frequently for the later fractions of head‐and‐neck and lung treatments. Additionally, averaging the GDSA mean metric over all patients on a given treatment day showed that changes in the machine output on the order of 1% could be identified. Conclusions GDSA of in vivo EPID images is a useful technique for monitoring patient changes during the course of treatment, particularly weight loss and tumor shrinkage...

show abstract

Section: Introductionmentioning

confidence: 99%

Using in vivo EPID images to detect and quantify patient anatomy changes with gradient dose segmented analysis

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The comparison was performed by γ-analysis using the same parameters as in conventional linacs (3% global/3mm/50% threshold) [27] . The choice for a threshold value of 50% of the maximum planned dose for γ-statistics is arbitrary, but a threshold is necessary to separate low and high dose areas.…”

Section: Methodsmentioning

confidence: 99%

Clinical rationale for in vivo portal dosimetry in magnetic resonance guided online adaptive radiotherapy

Maiques¹,

Ruiz²,

Janssen

et al. 2022

Physics and Imaging in Radiation Oncology

Self Cite

View full text Add to dashboard Cite

“…The MDACC calculation of dose is based on the TG-51 protocol [28] Core Houston (IROC-H, formerly, the RPC) for the end-to-end test requires that our institution's treatment plan agrees within ±7% of measured TLD doses in the PTVs, and that that ≥ 85% of pixels pass ±4 mm distance-to-agreement (i.e., 7%/4 mm gamma analysis for film) in the high dose gradient area between the PTV and the OAR. That is, a gamma (γ) index analysis compared 2D dose distributions between film measurements and Eclipse TPS dose calculations [29][30][31][32][33]. The gamma analysis method evaluates the coincidence between measured and calculated dose distributions by using percentage dose difference (DD) and distance-to-agreement (DTA) where the evaluation criteria were set at 7%/4 mm (i.e., 7% DD and 4 mm DTA).…”

Section: Figure 1 (A) Tld Dosimetry Irradiation System Comprising Acr...mentioning

confidence: 99%

End-to-End Test for a Radiotherapy Program Based on the Medical Linear Accelerator Installed in a Resource-Limited Oncology Centre in Sub-Saharan Africa

Mobit¹,

Imandi²,

Ade³

2022

RST

View full text Add to dashboard Cite

Several challenges including the availability of necessary funds and expertise hinder the development and modernization of radiotherapy in resource-scarce countries like those in Sub-Saharan Africa (SSA). This work presents the findings of an end-to-end audit on independent verification of radiation doses delivered by a commercially available medical linear accelerator (linac) installed at Cameroon Oncology Center, a resource-constrained oncology centre in SSA. The medical linac with 6 MV and 18 MV x-rays, and five electron energies ranging from 6-20 MeV was commissioned for clinical use. The mailed TLD dosimetry irradiation systems based on the American Radiological Physics Center technique were used to check the output of the photon beams and electron energies. The end-to-end test was achieved by requesting, imaging and treating the MD Anderson anthropomorphic head and neck phantom using an IMRT technique on our linac. The phantom was irradiated and sent back to the USA for analysis. Evaluation criteria require that an institution's treatment plan agree within ± 7% of measured TLD doses and that ≥ 85% of pixels pass ± 7%/4 mm gamma analysis for film. Beam output met the required criteria within ± 3%, and our institution's treatment plan satisfied the established criteria of measured TLD doses and film dose distributions. The gamma-passing rate was ≥ 91%. A resource-constrained oncology centre in SSA has met the MD Anderson humanoid phantom irradiation criteria generally used for credentialing institutions to assure quality and safety of complex radiation treatments. Despite the various challenges faced by resource-constrained countries in SSA, this work demonstrates the practicability of implementing a modern radiotherapy program based on linear accelerator technology in a resource-limited region.

show abstract

Comparison of gamma- and DVH-based in vivo dosimetric plan evaluation for pelvic VMAT treatments

Cited by 16 publications

References 19 publications

Using in vivo EPID images to detect and quantify patient anatomy changes with gradient dose segmented analysis

Using in vivo EPID images to detect and quantify patient anatomy changes with gradient dose segmented analysis

Clinical rationale for in vivo portal dosimetry in magnetic resonance guided online adaptive radiotherapy

End-to-End Test for a Radiotherapy Program Based on the Medical Linear Accelerator Installed in a Resource-Limited Oncology Centre in Sub-Saharan Africa

Contact Info

Product

Resources

About