Monte Carlo study on the impact of spinal fixation rods on dose distribution in photon beams

Mesbahi, Asghar; Nejad, Farshad Seyed

doi:10.1016/s1507-1367(10)60064-8

Cited by 12 publications

(11 citation statements)

References 23 publications

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“…The second culprit of dosimetric uncertainty in calculating with metallic objects is inherent in the limitation of the calculation algorithm in the treatment planning system. While it has been widely established that Monte Carlo algorithms can best estimate the dose distributions with the presence of metallic implants [9] [11] [23] [24], dose calculation with high density materials is not accurate with the AAA algorithm. As demonstrated from the open beam measurements in Figure 2, AAA underestimated the lateral scatter and attenuation of titanium and cobalt-chrome, and the inaccuracy increased with material density.…”

Section: Discussionmentioning

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: Discussionmentioning

confidence: 99%

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

Tang¹,

LoSasso²,

Lim³

et al. 2022

IJMPCERO

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“…Second, metal implants distort dose distributions from therapeutic megavoltage beams. A 5% to 10% dose reduction to tissues in regions behind stabilization rods has been reported, due to the attenuation effect . As a result, some patients who might benefit from radiotherapy may be treated with lower doses unlikely to provide long‐term local control.…”

Section: Introductionmentioning

confidence: 99%

Perturbation effects of the carbon fiber‐PEEK screws on radiotherapy dose distribution

Nevelsky

Borzov

Daniel

et al. 2017

J Applied Clin Med Phys

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Radiation therapy, in conjunction with surgical implant fixation, is a common combined treatment in cases of bone metastases. However, metal implants generally used in orthopedic implants perturb radiation dose distributions. Carbon‐Fiber Reinforced Polyetheretherketone (CFR‐PEEK) material has been recently introduced for production of intramedullary nails and plates. The purpose of this work was to investigate the perturbation effects of the new CFR‐PEEK screws on radiotherapy dose distributions and to evaluate these effects in comparison with traditional titanium screws. The investigation was performed by means of Monte Carlo (MC) simulations for a 6 MV photon beam. The project consisted of two main stages. First, a comparison of measured and MC calculated doses was performed to verify the validity of the MC simulation results for different materials. For this purpose, stainless steel, titanium, and CFR‐PEEK plates of various thicknesses were used for attenuation and backscatter measurements in a solid water phantom. For the same setup, MC dose calculations were performed. Next, MC dose calculations for titanium, CFR‐PEEK screws, and CFR‐PEEK screws with ultrathin titanium coating were performed. For the plates, the results of our MC calculations for all materials were found to be in good agreement with the measurements. This indicates that the MC model can be used for calculation of dose perturbation effects caused by the screws. For the CFR‐PEEK screws, the maximum dose perturbation was less than 5%, compared to more than 30% perturbation for the titanium screws. Ultrathin titanium coating had a negligible effect on the dose distribution. CFR‐PEEK implants have good prospects for use in radiotherapy because of minimal dose alteration and the potential for more accurate treatment planning. This could favorably influence treatment efficiency and decrease possible over‐ and underdose of adjacent tissues. The use of such implants has potential clinical advantages in the treatment of bone metastases.

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“…bone removal, tumour debulking etc.). [98,99] Further, as the spinal cord undergoes decompression, the location of the spinal cord is expected to shift over time and, therefore, the geometric constraints of the cord applied preoperatively are no longer valid. While care can be taken to maintain separation between the cord and the epidural disease by packing the surgical cavity, geometric limitations remain.…”

Section: Discussionmentioning

confidence: 99%

Feasibility Of Radiation Dose Planning Guided Surgical Resection In Spinal Tumours

Jakubovic¹

2021

Preprint

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The objective of high dose stereotactic radiotherapy regardless of application is to treat the malignancy while minimizing the radiation dose to the surrounding healthy tissue. In the context of spinal tumours this paradigm is difficult since the rigid dose tolerance of the spinal cord precludes optimal dose coverage of the epidural disease. To achieve adequate coverage spine separation surgery is performed, increasing the distance from the spinal cord to the malignancy and facilitating adequate radiation treatment planning. This approach has been validated with delivery of maximum tolerable dose and local control rates over 90%. The objective of this dissertation is to establish the feasibility of intraoperative, dose guided, spine separation surgery. In the current clinical context, spine separation surgery is performed prior to radiation treatment planning and contours are placed based on postoperative resected tumour volumes. The extent of surgical resection is not dictated by the dosimetric constraints of the spinal cord and relies solely on the clinical expertise of the operating neurosurgeon. Further, though a skilled surgeon can perform precise tumour debulking with or without the aid of millimetre resolution neuronavigation devices, determination of surgical debulking progress with accuracy comparable to treatment delivery cannot be recognized without intraoperative imaging. To achieve this goal, we introduced pre-surgical dosimetric planning with tracked high frequency micro-ultrasound imaging into the operating theatre to inform the surgeon of the surgical progress while considering the dosimetric objectives. In this dissertation, we assessed the dosimetric advantage of spine separation surgery on a millimetre by millimetre basis in a retrospective simulation study. Feasibility of intraoperative navigation with submillimetre resolution was established by quantifying the application accuracy of surgical navigation in the context of cranial and spinal surgery. Accuracy quantification was performed, assessing our revolutionary optical topographical imaging system and benchmarked versus existing commercially available neuronavigation systems. Finally, to establish feasibility of radiation dose planning guided surgical resection we integrated a high frequency micro-ultrasound system into the operating theater during spine separation surgery. Thus, by implementing sub-millimetre high frequency micro-ultrasound imaging and neuronavigation, incremental gains towards establishing the feasibility of in traoperative dose planning by iteratively updating the extent of tumour resection were recognized.

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Monte Carlo study on the impact of spinal fixation rods on dose distribution in photon beams

Cited by 12 publications

References 23 publications

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

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

Perturbation effects of the carbon fiber‐PEEK screws on radiotherapy dose distribution

Feasibility Of Radiation Dose Planning Guided Surgical Resection In Spinal Tumours

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