Implications of tissue heterogeneity for radiosurgery in head and neck tumors

Solberg, Timothy D.; Holly, F. Eugene; Salles, Antonio A. F. De; Wallace, Robert E.; Smathers, James B.

doi:10.1016/0360-3016(94)00495-7

Cited by 48 publications

(28 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The shortcoming of PB algorithms to accurately predict dose in low density media has been described previously 27 , 32 , 45 , 46 , 47 , 48 , 49 . In a recent study of 304 irradiations performed at 221 different institutions, Kry et al (49) observed an overestimate of 4.9% in PB algorithms compared to measurement in the Radiological Physics Center (RPC) thorax phantom used for RTOG credentialing; these results agree favorably with those reported here.…”

Section: Discussionsupporting

confidence: 87%

“…Acquisition of beam data for SRS and SABR can be particularly challenging, however, due to the small size of the fields employed and the partial volume effects associated with many common dosimeters. Further, small photon beams exhibit a loss of lateral electronic equilibrium on the central axis, producing output factors that falloff rapidly for fields below 10 mm in diameter 26 , 27 , 28 , 29 . Centering of the dosimeter in the beam is also challenging, and improper alignment of the beam and detector can introduce significant errors.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

Solberg

Medin

Ramirez

et al. 2014

J Applied Clin Med Phys

Self Cite

View full text Add to dashboard Cite

The purpose of this study is to describe the comprehensive commissioning process and initial clinical performance of the Vero linear accelerator, a new radiotherapy device recently installed at UT Southwestern Medical Center specifically developed for delivery of image‐guided stereotactic ablative radiotherapy (SABR). The Vero system utilizes a ring gantry to integrate a beam delivery platform with image guidance systems. The ring is capable of rotating ± 60° about the vertical axis to facilitate noncoplanar beam arrangements ideal for SABR delivery. The beam delivery platform consists of a 6 MV C‐band linac with a 60 leaf MLC projecting a maximum field size of 15×15 cm2 at isocenter. The Vero planning and delivery systems support a range of treatment techniques, including fixed beam conformal, dynamic conformal arcs, fixed gantry IMRT in either SMLC (step‐and‐shoot) or DMLC (dynamic) delivery, and hybrid arcs, which combines dynamic conformal arcs and fixed beam IMRT delivery. The accelerator and treatment head are mounted on a gimbal mechanism that allows the linac and MLC to pivot in two dimensions for tumor tracking. Two orthogonal kV imaging subsystems built into the ring facilitate both stereoscopic and volumetric (CBCT) image guidance. The system is also equipped with an always‐active electronic portal imaging device (EPID). We present our commissioning process and initial clinical experience focusing on SABR applications with the Vero, including: (1) beam data acquisition; (2) dosimetric commissioning of the treatment planning system, including evaluation of a Monte Carlo algorithm in a specially‐designed anthropomorphic thorax phantom; (3) validation using the Radiological Physics Center thorax, head and neck (IMRT), and spine credentialing phantoms; (4) end‐to‐end evaluation of IGRT localization accuracy; (5) ongoing system performance, including isocenter stability; and (6) clinical SABR applications.PACS number: 87.53.Ly

show abstract

Section: Discussionsupporting

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

Solberg

Medin

Ramirez

et al. 2014

J Applied Clin Med Phys

Self Cite

View full text Add to dashboard Cite

show abstract

“…cavities (3)(4)(5)(6)(7) . On the other hand, the under dosing that gives rise to the skin-sparing effect could reduce the dose delivered to the rectal wall during treatment of prostate cancer, as reported by Holmes et al (1) .…”

Section: Introductionmentioning

confidence: 99%

Dosimetric accuracy of the Acuros XB and Anisotropic analytical algorithm near interface of the different density media for the small fields of a 6- MV flattening-filter-free beam

Kang

Chung

Lee

et al. 2017

IJRR

View full text Add to dashboard Cite

“…More accurate algorithms may prove valuable, especially in reirradiation cases of the head and neck with hypofractionated dosing where accurate prediction of dose distribution to conformal target volumes and organs at risk is critical. Where clinically available, more accurate dose calculation algorithms, such as Monte Carlo-based (MC) method, (4,5,6,7) could prove beneficial in such cases in which there exists a delicate balance between side effects and tumor control.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, the authors concluded that both normal tissue inhomogeneity and surgical air cavities on the target coverage were adequately characterized by the conventional pencil beam algorithm when compared to MC-based calculation. The challenges of air-tissue interfaces were characterized by Solberg and colleagues, (5) who undertook phantom measurements with and without air-gap inserts and evaluated the ability of a MC algorithm to account for dose perturbation using a 10 MV beam. In their smaller field geometry, which used a radiosurgical setup with a 1 cm circular tissue diameter and a 3 mm air cavity at 2.6 cm depth, both film and diode measurements suggested a reduction of central axis dose by up to 21% in the area immediately following the cavity.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo evaluation of tissue heterogeneities corrections in the treatment of head and neck cancer patients using stereotactic radiotherapy

Pokhrel

McClinton

Sood

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

The purpose of this study was to generate Monte Carlo computed dose distributions with the X-ray voxel Monte Carlo (XVMC) algorithm in the treatment of head and neck cancer patients using stereotactic radiotherapy (SRT) and compare to heterogeneity corrected pencil-beam (PB-hete) algorithm. This study includes 10 head and neck cancer patients who underwent SRT re-irradiation using heterogeneity corrected pencil-beam (PB-hete) algorithm for dose calculation. Prescription dose was 24-40 Gy in 3-5 fractions (treated 3-5 fractions per week) with at least 95% of the PTV volume receiving 100% of the prescription dose. A stereotactic head and neck localization box was attached to the base of the thermoplastic mask fixation for target localization. The gross tumor volume (GTV) and organs-at-risk (OARs) were contoured on the 3D CT images. The planning target volume (PTV) was generated from the GTV with 0 to 5 mm uniform expansion; PTV ranged from 10.2 to 64.3 cc (average = 35.0±17.5 cc). OARs were contoured on the 3D planning CT and consisted of spinal cord, brainstem, optic structures, parotids, and skin. In the BrainLab treatment planning system (TPS), clinically optimal SRT plans were generated using hybrid planning technique (combination of 3D conformal noncoplanar arcs and nonopposing static beams) for the Novalis-Tx linear accelerator consisting of high-definition multileaf collimators (HD-MLCs: 2.5 mm leaf width at isocenter) and 6 MV-SRS (1000 MU/min) beam. For the purposes of this study, treatment plans were recomputed using XVMC algorithm utilizing identical beam geometry, multileaf positions, and monitor units and compared to the corresponding clinical PB-hete plans. The Monte Carlo calculated dose distributions show small decreases (< 1.5%) in calculated dose for D 99 , D mean , and D max of the PTV coverage between the two algorithms. However, the average target volume encompassed by the prescribed percent dose (V p ) was about 2.5% less with XVMC vs. PB-hete and ranged between -0.1 and 7.8%. The averages for D 100 and D 10 of the GTV were lower by about 2% and ranged between -0.8 and 3.1%. For the spinal cord, both the maximal dose difference and the dose to 0.35 cc of the structure were higher by an average of 4.2% (ranged 1.2 to -13.6%) and 1.4% (ranged 7.5 to -11.3%), respectively, with XVMC calculation. For the brainstem, the maximal dose differences and the dose to 0.5 cc of the structure were, on average, higher by 2.4% (ranged 6.4 to -8.0%) and 3.6% (ranged 6.4 to -9.0%), respectively. For the parotids, both the mean dose and the dose to 20 cc of parotids were higher by an average of 3% (ranged -0.2 to -5.9%) and 4% (ranged -0.2 to -8%), respectively, with XVMC calculation. For the optic apparatus, results from both algorithms were similar. However, the mean dose to skin was 3% higher (ranged 0 to -6%), on average, with XVMC compared to PB-hete, although the maximum dose to skin was 2%

show abstract

Implications of tissue heterogeneity for radiosurgery in head and neck tumors

Cited by 48 publications

References 8 publications

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

Commissioning and initial stereotactic ablative radiotherapy experience with Vero

Dosimetric accuracy of the Acuros XB and Anisotropic analytical algorithm near interface of the different density media for the small fields of a 6- MV flattening-filter-free beam

Monte Carlo evaluation of tissue heterogeneities corrections in the treatment of head and neck cancer patients using stereotactic radiotherapy

Contact Info

Product

Resources

About