Dosimetric Comparison of Helical Tomotherapy and Dynamic Conformal Arc Therapy in Stereotactic Radiosurgery for Vestibular Schwannomas

Lee, Tsair-Fwu; Chao, Pei‐Ju; Wang, Changyu; Lan, Jen-Hong; Huang, Y; Hsu, Hsuan-Chih; Sung, Chieh-Cheng; Su, Te‐Jen; Lian, Shi-Long; Fang, Fu‐Min

doi:10.1016/j.meddos.2009.11.005

Cited by 25 publications

(20 citation statements)

References 35 publications

(32 reference statements)

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“…Improvement ratio: The ratio used to evaluate the improvement in the index between the two rival plans (a plan with a 2.5-mm MLC vs. a plan with a 5-mm MLC) [30]. …”

Section: Methodsmentioning

confidence: 99%

The effect of multileaf collimator leaf width on the radiosurgery planning for spine lesion treatment in terms of the modulated techniques and target complexity

2014

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PurposeWe aim to evaluate the effects of multileaf collimator (MLC) leaf width (5 mm vs. 2.5 mm) on the radiosurgery planning for the treatment of spine lesions according to the modulated techniques (intensity-modulated radiotherapy [IMRT] vs. volumetric-modulated arc therapy [VMAT]) and the complexity of the target shape.MethodsFor this study, artificial spinal lesions were contoured and used for treatment plans. Three spinal levels (C5, T5, and L2 spines) were selected, and four types of target shapes reflecting the complexity of lesions were contoured. The treatment plans were performed using 2.5-mm and 5-mm MLCs, and also using both static IMRT and VMAT. In total, 48 treatment plans were established. The efficacy of each treatment plan was compared using target volume coverage (TVC), conformity index (CI), dose gradient index (GI), and V30%.ResultsWhen the 5-mm MLC was replaced by the 2.5-mm MLC, TVC and GI improved significantly by 5.68% and 6.25%, respectively, while CI did not improve. With a smaller MLC leaf width, the improvement ratios of the TVC were larger in IMRT than VMAT (8.38% vs. 2.97%). In addition, the TVC was improved by 14.42-16.74% in target type 4 compared to the other target types. These improvements were larger in IMRT than in VMAT (27.99% vs. 6.34%). The V30% was not statistically different between IMRT and VMAT according to the MLC leaf widths and the types of target.ConclusionThe smaller MLC leaf width provided improved target coverage in both IMRT and VMAT, and its improvement was larger in IMRT than in VMAT. In addition, the smaller MLC leaf width was more effective for complex-shaped targets.

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“…Improvement ratio: The ratio used to evaluate the improvement in the index between the two rival plans (a plan with a 2.5-mm MLC vs. a plan with a 5-mm MLC) [30]. …”

Section: Methodsmentioning

confidence: 99%

The effect of multileaf collimator leaf width on the radiosurgery planning for spine lesion treatment in terms of the modulated techniques and target complexity

2014

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“…Recent dosimetric studies, including the dose gradient analyses, have frequently dealt with the treatment techniques with nearly coplanar beam arrangements such as Helical tomotherapy [15][16][17][18] and volumetric modulated arc therapy. 19) The arc arrangement of the RapidArc plan with two arcs, as reported by Mayo et al,20) was similar to the "3 arcs (a)" plan shown in Fig.…”

Section: Effect Of Planning Methods On the Gi Valuesmentioning

confidence: 99%

“…The non-coplanar DCA plans have been shown to represent a better dose gradient than the Helical tomotherapy plans in SRS plans for skull-base tumors. 16,17) The DCA technique has a great freedom for the arc arrangement and would be therefore more advantageous for attaining the steep dose gradient than the coplanar beam delivery systems. Planners must arrange the arc positions to attain the better dose gradient in addition to the better target coverage and conformity.…”

Section: Effect Of Planning Methods On the Gi Valuesmentioning

confidence: 99%

Dose Gradient Analyses in Linac-based Intracranial Stereotactic Radiosurgery Using Paddick's Gradient Index: Consideration of the Optimal Method for Plan Evaluation

Ohtakara¹,

Hayashi²,

Hoshi³

2011

JRR

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The objective of our study was to describe the dose gradient characteristics of Linac-based stereotactic radiosurgery using Paddick's gradient index (GI) and to elucidate the factors influencing the GI value. Seventy-three plans for brain metastases using the dynamic conformal arcs were reviewed. The GI values were calculated at the 80% and 90% isodose surfaces (IDSs) and at the different target coverage IDSs (D99, D95, D90, and D85). The GI values significantly decreased as the target coverage of the reference IDS increased (the percentage of the IDS decreased). There was a significant inverse correlation between the GI values and target volume. The plans generated with the addition of a 1-mm leaf margin had worse GI values both at the D99 and D95 relative to those without leaf margin. The number and arrangement of arcs also affected the GI value. The GI values are highly sensitive to (1) the IDS selection variability for dose prescription or evaluation, (2) the target volume, and (3) the planning method. To objectively compare the quality of dose gradient between rival plans, it would be preferable to employ the GI defined at the reference IDS indicating the specific target coverage (e.g., D95), irrespective of the intended marginal dose. The modified GI (mGI), defined in this study, substituting the denominator of the original GI with the target volume, would be useful to compensate for the false superior GI value in cases of target over-coverage with the reference IDS and to objectively evaluate the dose gradient outside the target boundary.

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“…Improvement ratio: The ratio used to evaluate the improvement in the index between the two plans (a 2.5-mm MLC plan vs. 5-mm MLC plan) [39].

Improvement ratio (%) = \frac{| Inde x_{2.5 - mm MLC} - Inde x_{5 - mm MLC} |}{Inde x_{5 - mm MLC}} \times 100 (%)

…”

Section: Methodsmentioning

confidence: 99%

Dosimetric impact of multileaf collimator leaf width according to sophisticated grade of technique in the IMRT and VMAT planning for pituitary adenoma lesion

2016

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We analyzed the difference in the dosimetric effect between 5-mm and 2.5-mm multileaf collimator (MLC) leaf width according to the sophisticated grades of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). Nineteen patients with pituitary adenomas were selected for this study. The treatment plans were performed according to the size of the MLC (5-mm and 2.5-mm MLC), the type of technique (IMRT and VMAT), and the sophisticated grades of each technique (5-field, 9-field, 13-field, 17-field technique in IMRT and 1-arc and 2-arc techniques in VMAT). The downsizing effects of MLC leaf width were analyzed using target volume coverage (TVC), conformity index (CI), dose gradient index (GI), and normal tissue difference 70% isodose line and 50% isodose line. Upon replacing the 5-mm MLC with the 2.5-mm MLC, TVC and CI improved by 1.30% and 1.36%, respectively, in total plans. The TVC and CI improved by 1.68% and 1.67% in IMRT, respectively, and by 0.54% and 0.72% in VMAT, respectively. TVC improved by 2.53%, 1.82%, 1.34%, and 0.94%, and CI also improved by 2.70%, 1.81%, 1.24%, and 0.94%, in 5-field, 9-field, 13-field, and 17-field IMRT, respectively. TVC improved by 0.66% and 0.43%, and CI also improved by 0.93%, and 0.52% in 1-arc and 2-arc VMAT, respectively. Regarding the target coverage, there were dosimetric benefits of a smaller MLC leaf width. However, the downsizing effect of the MLC leaf width decreased with the use of a more precise RT technique and a more sophisticated grade of the same technique.

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Dosimetric Comparison of Helical Tomotherapy and Dynamic Conformal Arc Therapy in Stereotactic Radiosurgery for Vestibular Schwannomas

Cited by 25 publications

References 35 publications

The effect of multileaf collimator leaf width on the radiosurgery planning for spine lesion treatment in terms of the modulated techniques and target complexity

The effect of multileaf collimator leaf width on the radiosurgery planning for spine lesion treatment in terms of the modulated techniques and target complexity

Dose Gradient Analyses in Linac-based Intracranial Stereotactic Radiosurgery Using Paddick's Gradient Index: Consideration of the Optimal Method for Plan Evaluation

Dosimetric impact of multileaf collimator leaf width according to sophisticated grade of technique in the IMRT and VMAT planning for pituitary adenoma lesion

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