On the accuracy of dose prediction near metal fixation devices for spine SBRT

Cheng, Zhangkai J.; Bromley, Regina; Oborn, Bradley M; Carolan, Martin G; Booth, Jeremy

doi:10.1120/jacmp.v17i3.5536

Cited by 10 publications

(10 citation statements)

References 16 publications

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“…However, the underestimation of density due to the saturation of HU is larger for cobalt-chrome and the dosimetric uncertainty may be amplified. While the dosimetric effect of titanium hardware has been widely studied [8]- [14], to our best knowledge, this is the first study to evaluate the dosimetric effect of cobalt-chrome spinal hardware for single fraction and hypofractionated paraspinal IMRT and VMAT cases. Data is presented to support a clinical decision on the necessity to contour the hardware and assign the correct electron density for treatment planning.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

Tang¹,

LoSasso²,

Lim³

et al. 2022

IJMPCERO

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High density materials are assigned with an apparent density of 3.2 g/cm 3 in 12-bit CT images due to saturation. This is often ignored in planning for spine tumors with titanium (density 4.40 g/cm 3 ) spinal hardware. However, new cobalt-chrome hardware has a density of 8.11 g/cm 3 , which would increase dosimetric uncertainty if the true density is not utilized in planning. This effect was evaluated in this study. Calculation accuracy was examined using MapCHECK2 with a single 20 × 10 cm 2 field with a titanium and a cobalt-chrome rod in a solid water phantom for 6X, 6FFF and 15X, at 2 cm and 6 cm beneath the rods. Measurement was compared to the calculation with density override (DO) with the true density and to the calculation with no-density override (NDO). Additionally, the dosimetric effect in clinical treatment plans was investigated for six IMRT and VMAT paraspinal cases. Plan quality was compared with the original NDO calculation and the DO recalculation. Compared to measurements, the treatment planning system (TPS) overestimated the dose locally by up to 13.2% for cobalt-chrome and 4.8% for titanium with NDO calculations. DO calculations improved the differences to 8.4% and 4.0%, respectively. Scatter from the rod increased the lateral dose and diminished as depth increased but was not properly accounted for by the TPS even with the correct density assigned. For the clinical plans, PTV coverage was lowered by an average of ~1.0% (range: 0.5% -2.0%) and ~0.3% (range: 0.2% -0.7%) in DO recalculations for cobalt-chrome and titanium, respectively. In conclusion, neglecting the true density of cobalt-chrome hardware during planning may result in an unexpected decrease in target coverage.

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Section: Introductionmentioning

confidence: 99%

Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

Tang¹,

LoSasso²,

Lim³

et al. 2022

IJMPCERO

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show abstract

“…Previously published studies on the impact of spinal metal hardware on the dose calculation, and the beam delivery specific to spine SBRT using IMRT techniques [17] , [18] , [19] have been limited. For example, Son et al investigated the effects of titanium spinal implants on the dose calculated by the TPS for various delivery techniques such as ARTISTE, TomoTherapy and CyberKnife using three different types of imaging namely kVCT, extended kVCT and MVCT with an in-house homogeneous phantom with/without the titanium pedicle screws [17] .…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the plan that was compared was a simple plan as opposed to a highly complex spine SBRT plan. Cheng et al also evaluated the dose prediction accuracy near titanium hardware for spine SBRT using immersed gafchromic films embedded within an in-house water phantom with titanium spinal hardware [19] . A comparison between the measured and calculated doses for a simple plan with six open-fields was performed, and showed greater than 95% agreement with a gamma criterion of 2%/2mm for the commercial TPS dose calculation algorithms.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of multi-institutional end-to-end testing for post-operative spine stereotactic body radiation therapy

Furuya

Lee

Archibald-Heeren

et al. 2020

Physics and Imaging in Radiation Oncology

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Background and purpose: Post-operative spine stereotactic body radiation therapy (SBRT) represents a significant challenge as there are many restrictions on beam geometry to avoid metal hardware as it surrounds the target volume. In this study, an international multi-institutional end-to-end test using an in-house spine phantom was developed and executed. The aim was to evaluate the impact of titanium spine hardware on planned and delivered dose for post-operative spine SBRT. Materials and methods: Five centers performed simulation, planning and irradiation of the spine phantom, with/ without titanium metal hardware (MB/B), following our pre-specified protocol. The doses were calculated using the centers' treatment planning system (TPS) and measured with radiophotoluminescent glass dosimeters (RPLDs) embedded within each phantom. Results: The dose differences between the RPLD measured and calculated doses in the target region were within ± 5% for both phantoms studied. Differences greater than 5% were observed for the spinal cord and the out-of-the target regions due to steeper dose gradient regions that are created in these plans. Dose measurements within ± 3% were observed between RPLDs that were embedded in MB and B inserts. For the spinal cord and the out-of-target regions surrounded by metal hardware, the dose measured using RPLDs was within 3% different near the titanium screws compared to the dose measured near only the metal rods. Conclusion: We have successfully performed the first multi-institutional end-to-end dose analysis using an inhouse phantom built specifically for post-operative spine SBRT. The differences observed between the measured and planned doses in the presence of metal hardware were clinically insignificant.

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“…Supported by measurements in phantoms with a single beam or parallel-opposing beams, several studies have reported the dose perturbation by the spinal hardware. [3][4][5][6] Using Pinnacle dose calculation algorithm for a SBRT plan using step-shoot intensity-modulated radiation therapy (IMRT), Wang et al 7 found a ∼0.5 Gy dose decrease for seven cases with prescription dose of 24 Gy when manually overriding the physical density with the correct number. Using the Analytical Anisotropic Algorithm (AAA) algorithm from Eclipse planning system for one step-shoot IMRT and five volumetric modulated arc therapy (VMAT) plans, Tang et al 8 found the differences in V95% to the PTV between density override (DO) and no-DO calculations were within 1% for both titanium and cobalt-chrome implants, while the differences to maximum dose in the spinal cord were 0.02-0.18 Gy for titanium implants and 0.06-0.25 Gy for cobaltchrome implants.…”

Section: Introductionmentioning

confidence: 99%

The dosimetric impact of titanium implants in spinal SBRT using four commercial treatment planning algorithms

Liu

Cho

Magnelli

et al. 2023

J Applied Clin Med Phys

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To evaluate the dosimetric impact of titanium implants in spine SBRT using four dose calculation algorithms. Twenty patients with titanium implants in the spine treated with SBRT without density override (DO) were selected. The clinical plan for each patient was created in Pinnacle and subsequently imported into Eclipse (AAA and AcurosXB) and Raystation (CC) for dose evaluation with and without DO to the titanium implant. We renormalized all plans such that 90% of the tumor volume received the prescription dose and subsequently evaluated the following dose metrics: (1) the maximum dose to 0.03 cc (Dmax), dose to 99% (D99%) and 90% (D90%) of the tumor volume; (2) Dmax and volumetric metrics of the spinal cord. For the same algorithm, plans with and without DO had similar dose distributions. Differences in Dmax, D99% and D90% of the tumor were on average <2% with slightly larger variations up to 5.58% in Dmax using AcurosXB. Dmax of the spinal cord for plans calculated with DO increased but the differences were clinically insignificant for all algorithms (mean: 0.36% ± 0.7%). Comparing to the clinical plans, the relative differences for all algorithms had an average of 1.73% (−10.36%–13.21%) for the tumor metrics and −0.93% (−9.87%–10.95%) for Dmax of the spinal cord. A few cases with small tumor and spinal cord volumes, dose differences of >10% in both D99% and Dmax of the tumor, and Dmax of the spinal cord were observed. For all algorithms, the presence of titanium implants in the spine for most patients had minimal impact on dose distributions with and without DO. For the same plan calculated with different algorithms, larger differences in volumetric metrics of >10% could be observed, impacted by dose gradient at the plan normalization volume, tumor volumes, plan complexity, and partial voxel volume interpolation.

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On the accuracy of dose prediction near metal fixation devices for spine SBRT

Cited by 10 publications

References 16 publications

Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

Dosimetric Effect of Cobalt-Chrome Stabilization Hardware in Paraspinal Radiation Treatments

Evaluation of multi-institutional end-to-end testing for post-operative spine stereotactic body radiation therapy

The dosimetric impact of titanium implants in spinal SBRT using four commercial treatment planning algorithms

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