Characterization and evaluation of 2.5 MV electronic portal imaging for accurate localization of intra‐ and extracranial stereotactic radiosurgery

Song, Kwang Hyun; Snyder, Karen; Kim, Jinkoo; Li, Haisen; Rusnac, Robert; Jackson, Paul; Gordon, J; Siddiqui, Salim; Chetty, Indrin J.

doi:10.1120/jacmp.v17i4.6247

Cited by 11 publications

(6 citation statements)

References 24 publications

(15 reference statements)

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“…However, depending on the direction of the motion displacements, this magnitude of stability and reproducibility can have dosimetric impact on target coverage and sparing of the organs-at-risk, such as the heart and the lung. Utilizing kV or 2.5 MV [15][16][17][18] imaging with implanted clips for alignment may offer increased accuracy at patient setup. 19,20 Further investigation of the intra-and inter-fractional variations will be needed to examine the dosimetric effects.…”

Section: Discussionmentioning

confidence: 99%

Stability and reproducibility comparisons between deep inspiration breath‐hold techniques for left‐sided breast cancer patients: A prospective study

Parsons

Joo

Iqbal

et al. 2023

J Applied Clin Med Phys

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Deep inspiration breath-hold (DIBH) is crucial in reducing the lung and cardiac dose for treatment of left-sided breast cancer.We compared the stability and reproducibility of two DIBH techniques: Active Breathing Coordinator (ABC) and VisionRT (VRT). Materials and Methods:We examined intra-and inter-fraction positional variation of the left lung. Eight left-sided breast cancer patients were monitored with electronic portal imaging during breath-hold (BH) at every fraction. For each patient, half of the fractions were treated using ABC and the other half with VRT, with an equal amount starting with either ABC or VRT. The lung in each portal image was delineated, and the variation of its area was evaluated. Intrafraction stability was evaluated as the mean coefficient of variation (CV) of the lung area for the supraclavicular (SCV) and left lateral (LLat) field over the course of treatment. Reproducibility was the CV for the first image of each fraction. Daily session time and total imaging monitor units (MU) used in patient positioning were recorded. Results: The mean intrafraction stability across all patients for the LLat field was 1.3 ± 0.7% and 1.5 ± 0.9% for VRT and ABC, respectively. Similarly, this was 1.5 ± 0.7% and 1.6 ± 0.8% for VRT and ABC, respectively, for the SCV field. The mean interfraction reproducibility for the LLat field was 11.0 ± 3.4% and 14.9 ± 6.0% for VRT and ABC, respectively. Similarly, this was 13.0 ± 2.5% and 14.8 ± 9% for VRT and ABC, respectively, for the SCV. No difference was observed in the number of verification images required for either technique. Conclusions: The stability and reproducibility were found to be comparable between ABC and VRT. ABC can have larger interfractional variation with less feedback to the treating therapist compared to VRT as shown in the increase in geometric misses at the matchline.

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Section: Discussionmentioning

confidence: 99%

Stability and reproducibility comparisons between deep inspiration breath‐hold techniques for left‐sided breast cancer patients: A prospective study

Parsons

Joo

Iqbal

et al. 2023

J Applied Clin Med Phys

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“…The image quality from the 2.5 MV beam has been investigated in the literature . Although image quality was not a primary motivator of this work, several properties of the beam commissioning parameters indicate the potential for higher image quality of the 2.5 MV beam compared to 6 MV.…”

Section: Discussionmentioning

confidence: 99%

“…The TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA) is equipped with a 2.5 MV unflattened beam option that is used for image guidance. This beam has shown to have improved image quality in comparison to higher energy MV imaging beams, such as 6 MV . The 2.5 MV beam is currently not used for delivering a therapeutic dose.…”

Section: Introductionmentioning

confidence: 99%

Calculating dose from a 2.5 MV imaging beam using a commercial treatment planning system

Ferris

Culberson

Anderson

et al. 2019

J Applied Clin Med Phys

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Patient dose from 2.5 MV images on the TrueBeam linear accelerator is not easily quantified, primarily because this beam energy is not normally modeled by commercial treatment planning systems. In this work we present the feasibility of using the Eclipse® treatment planning system to model this beam. The Acuros XB and the AAA dose calculation algorithms were tested. Profiles, PDDs, and output factors were measured for the 2.5 MV unflattened imaging beam and used for beam modeling. The algorithms were subsequently verified using MPPG 5.a guidelines. Calculated doses with both algorithms agreed with the measurement data to within the following criteria recommended for conventional therapeutic MV beams: 2% local dose‐difference in the high‐dose region, 3% global difference in the low‐dose region, 3 mm distance to agreement in the penumbra, and a gamma pass rate of >95% for 3%/3 mm criteria. Acuros was able to accurately calculate dose through cork and bone‐equivalent heterogeneities. AAA was able to accurately calculate dose through the bone‐equivalent heterogeneity but did not pass within the recommended criteria for the cork heterogeneity. For the 2.5 MV imaging beam, both the AAA and Acuros algorithms provide calculated doses that agree with measured results well within the 20% criteria for imaging beams recommended by AAPM TG‐180.

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“…The 2.5 MV beam is an FFF beam that was developed for imaging purposes and was studied by both experimental and Monte Carlo methods. 6,23,24 As done previously 8,21,22,25 for the 2.5 and 6 MV-SRS beams, when the accelerator head geometry was available from the manufacturer, the beam simulation started with electrons exiting from the vacuum window of the linear accelerator, including the details of the accelerator head geometry with flattening filter and beam defining systems. Each generated beam also included the position, energy, charge, and direction of every particle in the phase space file.…”

Section: Methodsmentioning

confidence: 99%

The effects of different photon beam energies in stereotactic radiosurgery with cones

Ding

Homann

2023

Medical Physics

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BackgroundStereotactic radiosurgery (SRS) relies on small fields to ablate lesions. Currently, linac based treatment is delivered via circular cones using a 6 MV beam. There is interest in both lower energy photon beams, which can offer steeper dose fall off as well as higher energy photon beams, which have higher dose rates, thus reducing radiation delivery times. Of interest in this study is the 2.5 MV beam developed for imaging applications and both the 6 and 10 MV flattening‐filter‐free (FFF) beams, which can achieve dose rates up to 2400 cGy/min.PurposeThis study aims to assess the benefit and feasibility among different energy beams ranging from 2.5 to 10 MV beams by evaluating the dosimetric effects of each beam and comparing the dose to organs‐at‐risk (OARs) for two separate patient plans. One based on a typical real patient tremor utilizing a 4 mm cone and the other a typical brain metastasis delivered with a 10 mm cone.MethodsThe Monte Carlo codes BEAMnrc/DOSXYZnrc were used to generate beams of 2.5 MV, 6 MV‐FFF, 6 MV‐SRS, 6 MV, 10 MV‐FFF, and 10 MV from a Varian TrueBeam except 6 MV‐SRS, which is taken from a Varian TX model linear accelerator. Each beam's energy spectrum, mean energy, %dd curve, and dose profile were obtained by analyzing the simulated beams. Calculated patient dose distributions were compared among six different energy beam configurations based on a realistic treatment plan for thalamotomy and a conventional brain metastasis plan. Dose to OARs were evaluated using dose–volume histograms for the same target dose coverage.ResultsThe mean energies of photons within the primary beam projected area were insensitive to cone sizes and the values of percentage depth–dose curves (%dd) at d = 5 cm and SSD = 95 cm for a 4 mm (10 mm) cone ranges from 62.6 (64.4) to 82.2 (85.7) for beam energy ranging from 2.5 to 10 MV beams, respectively. Doses to OARs were evaluated among these beams based on real treatment plans delivering 15 000 and 2200 cGy to the target with a 4 and 10 mm cone, respectively. The maximum doses to the brainstem, which is 10 mm away from the isocenter, was found to be 434 (300), 632 (352), 691 (362), 733 (375), 822 (403), and 975 (441) cGy for 2.5 MV, 6 MV‐FFF, 6 MV‐SRS, 6 MV, 10 MV‐FFF, and 10 MV beams delivering 15 000 (2200) cGy target dose, respectively.ConclusionUsing the 6 MV‐SRS as reference, changes of the maximum dose (691 cGy) to the brain stem are −37%, −9%, +6%, +19%, and 41% for 2.5 MV, 6 MV‐FFF, 6 MV, 10 MV‐FFF, and 10 MV beams, respectively, based on the thalamotomy plan, where the “‐” or “+” signs indicate the percentage decrease or increase. Changes of the maximum dose (362 cGy) to brain stem, based on the brain metastasis plan are much less for respective beam energies. The sum of 21 arcs beam‐on time was 39 min on our 6 MV‐SRS beam with 1000 cGy/min for thalamotomy. The beam‐on time can be reduced to 16 min with 10 MV‐FFF.

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Characterization and evaluation of 2.5 MV electronic portal imaging for accurate localization of intra‐ and extracranial stereotactic radiosurgery

Cited by 11 publications

References 24 publications

Stability and reproducibility comparisons between deep inspiration breath‐hold techniques for left‐sided breast cancer patients: A prospective study

Stability and reproducibility comparisons between deep inspiration breath‐hold techniques for left‐sided breast cancer patients: A prospective study

Calculating dose from a 2.5 MV imaging beam using a commercial treatment planning system

The effects of different photon beam energies in stereotactic radiosurgery with cones

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