Monte Carlo simulations with time-dependent geometries to investigate effects of organ motion with high temporal resolution

Paganetti, Harald; Jiang, Haihui Joy; Adams, Jody; CHEN, G; Rietzel, Eike

doi:10.1016/s0360-3016(04)01081-8

Cited by 34 publications

(34 citation statements)

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“…Clinical application of dose‐warping techniques is a contentious topic as reflected by, for instance, a recent point‐counterpoint article and correspondences published by Medical Physics which raised the question, ‘Is it appropriate to “deform” dose along with deformable image registration in adaptive radiotherapy?’ (33) Although the answer is not likely to be without complexity, a number of published studies have shown the applicability of dose‐warping techniques 9 , 10 , 11 , 14 , 15 , 16 , 17 . We have previously corresponded to the point‐counterpoint article 34 , 35 following earlier work in which we demonstrated an experimental validation of the dose‐warping technique, as well as accurate performance of deformable registration algorithms (13) .…”

Section: Discussionmentioning

confidence: 99%

“…Attempts to contend with organ deformation in image‐guided and adaptive radiotherapy often involve the implementation of deformable image registration (DIR) algorithms 4 , 5 , 6 , 7 , 8 . One approach for calculation of cumulative doses in moving and deforming targets for both inter‐ and intrafraction effects is via the ‘dose‐warping’ technique, using DIR to redistribute dose before summation 9 , 10 , 11 . Our previous work has demonstrated experimentally (using a deformable, three‐dimensional, dose‐integrating tissue‐equivalent dosimeter, ‘DEFGEL’ (12) ) that this can be performed accurately (13) when optimized appropriately.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration

Yeo

Taylor

Supple

et al. 2014

J Applied Clin Med Phys

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The purpose of this study is to evaluate dosimetric errors in 3D conventional planning of stereotactic body radiotherapy (SBRT) by using a 4D deformable image registration (DIR)‐based dose‐warping and integration technique. Respiratory‐correlated 4D CT image sets with 10 phases were acquired for four consecutive patients with five liver tumors. Average intensity projection (AIP) images were used to generate 3D conventional plans of SBRT. Quasi‐4D path‐integrated dose accumulation was performed over all 10 phases using dose‐warping techniques based on DIR. This result was compared to the conventional plan in order to evaluate the appropriateness of 3D (static) dose calculations. In addition, we consider whether organ dose metrics derived from contours defined on the average intensity projection (AIP), or on a reference phase, provide the better approximation of the 4D values. The impact of using fewer (<10) phases was also explored. The AIP‐based 3D planning approach overestimated doses to targets by 1.4% to 8.7% (mean 4.2%) and underestimated dose to normal liver by up to 8% (mean −5.5%; range −2.3% to −8.0%), compared to the 4D methodology. The homogeneity of the dose distribution was overestimated when using conventional 3D calculations by up to 24%. OAR doses estimated by 3D planning were, on average, within 10% of the 4D calculations; however, differences of up to 100% were observed. Four‐dimensional dose calculation using 3 phases gave a reasonable approximation of that calculated from the full 10 phases for all patients, which is potentially useful from a workload perspective. 4D evaluation showed that conventional 3D planning on an AIP can significantly overestimate target dose (ITV and GTV+5mm), underestimate normal liver dose, and overestimate dose homogeneity. Implementing nonadaptive quasi‐4D dose calculation can highlight the potential limitation of 3D conventional SBRT planning and the resultant misrepresentations of dose in some regions affected by motion and deformation. Where the 4D approach is unavailable, contouring on the full expiration phase may yield more accurate dose calculations, most relevant in the case of the healthy liver, but the absolute dose differences are in general small for the other healthy organs. The technique has the potential to quantify under‐ and over‐dosage and improve treatment plan evaluation, retrospective plan analysis, and clinical outcome correlation.PACS numbers: 87.55.‐x, 87.55.D‐, 87.55.de, 87.55.dk, 87.55.Qr, 87.57.nj

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration

Yeo

Taylor

Supple

et al. 2014

J Applied Clin Med Phys

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“…5 One approach for the calculation of accumulated dose in different phases of the breathing cycle is via ''dose warping.'' [6][7][8][9][10][11] In previous work, we have demonstrated that this may be performed accurately 12 using the DEFGEL dosimetry system. 13 This deformable image registration-based approach revealed that conventional 3-dimensional (3D) planning approaches can significantly underestimate the dose to the planning target volume (PTV) in liver SBRT.…”

Section: Introductionmentioning

confidence: 99%

The Importance of Quasi-4D Path-Integrated Dose Accumulation for More Accurate Risk Estimation in Stereotactic Liver Radiotherapy

Taylor

Yeo

Supple

et al. 2015

Technol Cancer Res Treat

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Intrafraction organ deformation may be accounted for by inclusion of temporal information in dose calculation models. In this article, we demonstrate a quasi-4-dimensional method for improved risk estimation. Conventional 3-dimensional and quasi-4-dimensional calculations employing dose warping for dose accumulation were undertaken for patients with liver metastases planned for 42 Gy in 6 fractions of stereotactic body radiotherapy. Normal tissue complication probabilities and stochastic risks for radiation-induced carcinogenesis and cardiac complications were evaluated for healthy peripheral structures. Hypothetical assessments of other commonly employed dose/fractionation schedules on normal tissue complication probability estimates were explored. Conventional 3-dimensional dose computation may result in significant under-or overestimation of doses to organ at risk. For instance, doses differ (on average) by 17% (s ¼ 14%) for the left kidney, by 14% (s ¼ 7%) for the right kidney, by 7% (s ¼ 9%) for the large bowel, and by 10% (s ¼ 14%) for the duodenum. Discrepancies in the excess relative risk range up to about 30%. The 3-dimensional approach was shown to result in cardiac complication risks underestimated by >20%. For liver stereotactic body radiotherapy, we have shown that conventional 3-dimensional dose calculation may significantly over-/underestimate dose to organ at risk (90%-120% of the 4-dimensional estimate for the mean dose and 20%-150% for D 2% ). Providing dose estimates that most closely represent the actual dose delivered will provide valuable information to improve our understanding of the dose response for partial volume irradiation using hypofractionated schedules. Excess relative risks of radiocarcinogenesis were shown to range up to approximately excess relative risk ¼ 4 and the prediction thereof depends greatly on the use of either 3-dimensional or 4-dimensional methods (with corresponding results differing by tens of percent).

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“…In such an approach, a single free‐breathing CT dataset is replaced by a series of up to 10 CT datasets sampled during various phases of a respiratory cycle. ( 10 , 14 ) However, evidence suggests that the true anatomic relationships between 4D CT image frames are uncertain, and current image‐processing methods suffer from considerable artifacts. ( 18 , 19 ) In addition, because the field size of a typical CT scan is limited, the interlinked motions and deformations involving several organs (such as heart, lungs, liver, etc.)…”

Section: Introductionmentioning

confidence: 99%

Development of a geometry‐based respiratory motion– simulating patient model for radiation treatment dosimetry

Zhang

Shi³

et al. 2008

J Applied Clin Med Phys

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Temporal and spatial anatomic changes caused by respiration during radiation treatment delivery can lead to discrepancies between prescribed and actual radiation doses. The present paper documents a study to construct a respiratory‐motion‐simulating, four‐dimensional (4D) anatomic and dosimetry model for the study of the dosimetric effects of organ motion for various radiation treatment plans and delivery strategies. The non‐uniform rational B‐splines (NURBS) method has already been used to reconstruct a three‐dimensional (3D) VIP‐Man (“visible photographic man”) model that can reflect the deformation of organs during respiration by using time‐dependent equations to manipulate surface control points. The EGS4 (Electron Gamma Shower, version 4) Monte Carlo code is then used to apply the 4D model to dose simulation. We simulated two radiation therapy delivery scenarios: gating treatment and 4D image‐guided treatment. For each delivery scenario, we developed one conformal plan and one intensity‐modulated radiation therapy plan. A lesion in the left lung was modeled to investigate the effect of respiratory motion on radiation dose distributions. Based on target dose–volume histograms, the importance of using accurate gating to improve the dose distribution is demonstrated. The results also suggest that, during 4D image‐guided treatment delivery, monitoring of the patient's breathing pattern is critical. This study demonstrates the potential of using a “standard” motion‐simulating patient model for 4D treatment planning and motion management.PACS numbers: 87.53.Bn, 87.53.Kn, 87.53.Tf, 87.53.Wz, 87.57.Gg, 89.80.+h

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Monte Carlo simulations with time-dependent geometries to investigate effects of organ motion with high temporal resolution

Abstract: We present a novel method able to calculate dose with underlying time-dependent geometry. The technique allows 4D dose calculation in arbitrary time scales in a single simulation even for double-dynamic systems (e.g., time-dependent beam delivery under organ motion).

Cited by 34 publications

References 0 publications

Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration

Evaluation of dosimetric misrepresentations from 3D conventional planning of liver SBRT using 4D deformable dose integration

The Importance of Quasi-4D Path-Integrated Dose Accumulation for More Accurate Risk Estimation in Stereotactic Liver Radiotherapy

Development of a geometry‐based respiratory motion– simulating patient model for radiation treatment dosimetry

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