Dosimetric comparisons of helical tomotherapy and step-and-shoot intensity-modulated radiotherapy in nasopharyngeal carcinoma

Lee, Tsair-Fwu; Fang, Fu‐Min; Chao, Pei‐Ju; Su, Te‐Jen; Wang, Luke K.; Leung, Stephen Wan

doi:10.1016/j.radonc.2008.05.010

Cited by 92 publications

(62 citation statements)

References 21 publications

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“…The smaller the value of CI, the better the conformal coverage. ( 34 , 35 ) Homogeneity index (HI):

H I = \frac{D_{5 %}}{D_{95 %}}

, a ratio evaluating the dose homogeneity in PTV, where

D_{5 %}

and

D_{95 %}

are the minimum doses delivered to 5% and 95% of the PTV. A higher HI indicates poorer homogeneity.…”

Section: Methodsmentioning

confidence: 99%

“…Comprehensive quality index (CQI): the sum of each QI function times the weight of the OARs ( 34 , 36 , 39 )

(i . e ., C Q I = \sum_{i = 1}^{N} W_{i} \times {false(Q I_{S e r i a l} | Q I_{p a r a l l e l} false)}_{i}

where i is the index of the critical structures and ‘|’ means ‘or’;

W_{i}

denotes the priority weight for the OAR based on the demands of the physicians.) CQI values

< 1

for an overall evaluation in the 11 OARs indicate a reduction in the maximal/mean dose for DA‐VMAT compared with 7F‐IMRT, and vice versa.…”

Section: Methodsmentioning

confidence: 99%

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Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma

Lee

Chao

Ting

et al. 2011

J Applied Clin Med Phys

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The purpose of this study was to evaluate and quantify the planning performance of SmartArc‐based volumetric‐modulated arc radiotherapy (VMAT) versus fixed‐beam intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) using a sequential mode treatment plan. The plan quality and performance of dual arc‐VMAT (DA‐VMAT) using the Pinnacle3 Smart‐Arc system (clinical version 9.0; Philips, Fitchburg, WI, USA) were evaluated and compared with those of seven‐field (7F)‐IMRT in 18 consecutive NPC patients. Analysis parameters included the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), maximum and mean dose, normal tissue complication probability (NTCP) for the specified organs at risk (OARs), and comprehensive quality index (CQI) for an overall evaluation in the 11 OARs. Treatment delivery time, monitor units per fraction (MU/fr), and gamma (Γ3mm,3%) evaluations were also analyzed. DA‐VMAT achieved similar target coverage and slightly better homogeneity than conventional 7F‐IMRT with a similar CI and HI. NTCP values were only significantly lower in the left parotid gland (for xerostomia) for DA‐VMAT plans. The mean value of CQI at 0.98±0.02 indicated a 2% benefit in sparing OARs by DA‐VMAT. The MU/fr used and average delivery times appeared to show improved efficiencies in DA‐VMAT. Each technique demonstrated high accuracy in dose delivery in terms of a high‐quality assurance (QA) passing rate (>98%) of the (Γ3mm,3%) criterion. The major difference between DA‐VMAT and 7F‐IMRT using a sequential mode for treating NPC cases appears to be improved efficiency, resulting in a faster delivery time and the use of fewer MU/fr.PACS number: 87.53.Tf, 87.55.x, 87.55.D, 87.55.dk

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“…The smaller the value of CI, the better the conformal coverage. ( 34 , 35 ) Homogeneity index (HI):

H I = \frac{D_{5 %}}{D_{95 %}}

, a ratio evaluating the dose homogeneity in PTV, where

D_{5 %}

and

D_{95 %}

are the minimum doses delivered to 5% and 95% of the PTV. A higher HI indicates poorer homogeneity.…”

Section: Methodsmentioning

confidence: 99%

“…Comprehensive quality index (CQI): the sum of each QI function times the weight of the OARs ( 34 , 36 , 39 )

(i . e ., C Q I = \sum_{i = 1}^{N} W_{i} \times {false(Q I_{S e r i a l} | Q I_{p a r a l l e l} false)}_{i}

where i is the index of the critical structures and ‘|’ means ‘or’;

W_{i}

denotes the priority weight for the OAR based on the demands of the physicians.) CQI values

< 1

for an overall evaluation in the 11 OARs indicate a reduction in the maximal/mean dose for DA‐VMAT compared with 7F‐IMRT, and vice versa.…”

Section: Methodsmentioning

confidence: 99%

Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma

Lee

Chao

Ting

et al. 2011

J Applied Clin Med Phys

Self Cite

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“…In comparison with linac based step and shoot IMRT, tomotherapy improves the conformity index to the PTVs and significantly reduces dose to the OAR [13,32], thereby improving the therapeutic index.…”

Section: Discussionmentioning

confidence: 99%

“…The dose prescription to the head and neck area also differs from other sites as there is usually one or more high-dose planning target volume (PTV) and a prophylactic nodal PTV receiving a differing radiation dose. Owing to its wider availability, most UK centres providing a head and neck IMRT service deliver linac-based IMRT; however, HT IMRT can achieve improved dose sparing to OAR compared with linac-based IMRT in the treatment of certain head and neck cancer sites [13]. This paper summarises the clinical challenges encountered in establishing a clinical helical tomotherapy IMRT…”

mentioning

confidence: 99%

Clinical challenges in the implementation of a tomotherapy service for head and neck cancer patients in a regional UK radiotherapy centre

Chatterjee

Mott²,

Smyth³

et al. 2011

BJR

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Objective: Intensity-modulated radiotherapy (IMRT) is increasingly being used to treat head and neck cancer cases. Methods: We discuss the clinical challenges associated with the setting up of an image guided intensity modulated radiotherapy service for a subset of head and neck cancer patients, using a recently commissioned helical tomotherapy (HT) Hi Art (Tomotherapy Inc, WI) machine in this article. We also discuss the clinical aspects of the tomotherapy planning process, treatment and image guidance experiences for the first 10 head and neck cancer cases. The concepts of geographical miss along with tomotherapy-specific effects, including that of field width and megavoltage CT (MVCT) imaging strategy, have been highlighted using the first 10 head and neck cases treated. Results: There is a need for effective streamlining of all aspects of the service to ensure compliance with cancer waiting time targets. We discuss how patient toxicity audits are crucial to guide refinement of the newly set-up planning dose constraints. The advantages of intensity-modulated radiotherapy (IMRT) in head and neck cancer, in terms of target conformation, organ at risk sparing and associated improvement in quality of life, and the potential for dose escalation, have been well documented [1][2][3]. The development and commercial release of the helical tomotherapy (HT) Hi Art (Tomotherapy, Madison WI) system by Mackie et al [4] has introduced advanced helical IMRT delivery techniques and combined these with integrated onboard image guidance capabilities [5]. Recent adoption of this technology within the NHS by two centres (Cambridge and Newcastle), alongside existing provision within a private sector treatment centre (BUPA Cromwell Hospital, London), enables delivery of highly conformal image-guided IMRT in the UK.The physical characteristics of the HT system are described in detail elsewhere [4,5]; however, in basic terms, the system is a short waveguide 6 MV linac mounted on a spiral CT gantry system. Beam collimation is by a pneumatically controlled binary multileaf collimator (MLC), with each leaf projecting to 6.25 mm at isocentre, for three selectable field widths [6]. Owing to its continuous rotational delivery technique and rapid beam modulation throughout its full arc of travel, the HT system gives greater flexibility than conventional linear accelerator (linac)-based IMRT that provides intensity modulation at multiple fixed gantry angles. Planning comparisons between tomotherapy and rotational techniques using conventional linacs, volumetric arc therapy (VMAT) or intensity-modulated arc therapy (IMAT), have also been published [7,8]; however, there is ongoing debate as to the relative merits of each technique [9][10][11][12].The complexity of head and neck radiotherapy is due to the proximity of multiple organs at risk (OAR), including critical structures such as the brain stem and spinal cord and important functional organs such as the parotid glands, optic nerve, optic chiasm, larynx and mandible. The dose prescription ...

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“…Treatments are optimized from 51 projections and can be conceptualized as IMRT beams delivered from 51 equally spaced angles. The benefit of HT in improving dose homogeneity and a reduced dose to critical structures have been reported in prostate cancer [11], nasopharyngeal cancer [12], other head and neck cancer [13], breast cancer [14], and intracranial tumors [15]. …”

Section: Htmentioning

confidence: 99%

Modern External Beam Radiotherapy Techniques for Endometrial Cancer

Yang¹,

Wang²

2012

Cancer of the Uterine Endometrium - Advances and Controversies

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Dosimetric comparisons of helical tomotherapy and step-and-shoot intensity-modulated radiotherapy in nasopharyngeal carcinoma

Cited by 92 publications

References 21 publications

Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma

Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma

Clinical challenges in the implementation of a tomotherapy service for head and neck cancer patients in a regional UK radiotherapy centre

Modern External Beam Radiotherapy Techniques for Endometrial Cancer

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