A dosimetric comparison of the use of equally spaced beam (ESB), beam angle optimization (BAO), and volumetric modulated arc therapy (VMAT) in head and neck cancers treated by intensity modulated radiotherapy.

Previous studies have shown that the beam arrangement had significant influence on plan quality in intensity modulated radiotherapy (IMRT). This study aimed to evaluate the dosimetric performance of beam arrangement methods by employing equally spaced beams (ESB), beam angle optimization (BAO), and volumetric modulated arc therapy (VMAT) in the planning of five types of head and neck (H&N) cancers treated by IMRT. Five plans of different beam arrangement methods were optimized for 119 H&N cancer patients with the prescription of 66-70 Gy for high-risk planning target volume (PTV), 60 Gy for intermediate risk PTV, 54 Gy for low-risk PTV using a simultaneously integrated boost method. The five-beam arrangement methods were: ESB, coplanar BAO (BAOc), noncoplanar BAO (BAOnc), two-arc VMAT (VMAT2), and three-arc VMAT (VMAT3). The H&N cancers included cancers of nasopharynx, oral cavity, larynx, maxillary sinus, and parotid. Although the partial arc VMAT could be used in cases where the PTVs were situated at one side of the head such as the parotid, this arrangement was not included because it was intended to include only the beam arrangements that were applicable to all the types of head and neck cancers in the study. The plans were evaluated using a "figure-of-merit" known as uncomplicated target conformity index (UTCI). In addition, PTV conformation number and homogeneity index, normal tissue integral dose, and organ at risk (OAR) doses were also used. The mean values of these parameters were compared among the five plans. All treatment plans met the preset dose requirements for the target volumes and OARs. For nasopharyngeal cancer, VMAT3 and BAOnc demonstrated significantly higher UTCI. For cancer of oral cavity, most beam arrangement showed similar UTCI except ESB, which was relatively lower. For cancer of larynx, there was no significant difference in UTCI among the five-beam arrangement methods. For cancers of maxillary sinus and parotid gland, the two BAO methods showed marginally higher UTCI among all the five methods. Individual methods showed dosimetric advantages on certain aspects, and the UTCI of the BAO treatment plans are marginally greater in the case of maxillary sinus and parotid gland. However, if treatment time was included into consideration, VMAT plans would be recommended for cancers of the nasopharynx, oral cavity, and larynx.

Leung WS ，Wu VWC ，Liu CYW ，Cheng ACK ... -  《Journal of Applied Clinical Medical Physics》

A dosimetric comparison of volumetric modulated arc therapy (VMAT) and non-coplanar intensity modulated radiotherapy (IMRT) for nasal cavity and paranasal sinus cancer.

Jeong Y ，Lee SW ，Kwak J ，Cho I ，Yoon SM ，Kim JH ，Park JH ，Choi EK ，Song SY ，Kim YS ，Kim SS ，Joo JH ，Ahn SD ... -  《Radiation Oncology》

Treatment planning comparison of IMPT, VMAT and 4π radiotherapy for prostate cases.

Tran A ，Zhang J ，Woods K ，Yu V ，Nguyen D ，Gustafson G ，Rosen L ，Sheng K ... -  《Radiation Oncology》

Volumetric-modulated arc therapy vs. c-IMRT in esophageal cancer: a treatment planning comparison.

Yin L ，Wu H ，Gong J ，Geng JH ，Jiang F ，Shi AH ，Yu R ，Li YH ，Han SK ，Xu B ，Zhu GY ... -  《-》

(18) F-Fluoromisonidazole positron emission tomography/CT-guided volumetric-modulated arc therapy-based dose escalation for hypoxic subvolume in nasopharyngeal carcinomas: A feasibility study.

The purpose of this study is to investigate the feasibility of a simultaneously integrated boost to the hypoxic subvolume of nasopharyngeal carcinomas (NCPs) under the guidance of 18 F-fluoromisonidazole (FMISO) positron emission tomography (PET)/CT using volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques. Eight patients with NPC were treated with simultaneous integrated boost-IMRT (treatment plan named IMRT70) with dose prescriptions of 70 Gy, 66 Gy, 60 Gy, and 54 Gy to the gross tumor volume (GTV), positive neck nodes, the planning target volume (PTV), and the clinically negative neck, respectively. Based on the same datasets, experimental plans with the same dose prescription plus a dose boost of 14 Gy (an escalation of 20% of the prescription dose) to the hypoxic volume target contoured on the pretreatment 18 F-FMISO PET/CT imaging were generated using IMRT and VMAT techniques, respectively (represented by IMRT84 and VMAT84). Two or more arcs (approximately 2-2.5 arcs, totally rotating angle <1000 degrees) were used in VMAT plans and 9 equally separated fields in IMRT plans. Dosimetric parameters, total monitor units, and delivery time were calculated for comparative study of plan quality and delivery efficiency between IMRT84 and VMAT84. In experimental plans, hypoxic target volumes successfully received the prescribed dose of 84 Gy in compliance with other dose constraints with either the IMRT technique or the VMAT technique. In terms of the target coverage, dose homogeneity, and organs at risk (OAR) sparing, there was no statistically significant difference between the actual treatment plan of IMRT70 and experimental plans. The total monitor unit of VMAT84 (525.7 ± 39.8) was significantly less than IMRT70 (1171.5 ± 167; P = .001) and IMRT84 (1388.3 ± 151.0; P = .001) per fraction, with 55.1% and 62.1% reduction. The average machine delivery time was 3.5 minutes for VMAT plans in comparison with approximately 8 minutes for IMRT plans, resulting in a reduction factor of 56.2%. For experimental plans, the 3D gamma index average was over 98.0% with no statistical significant difference when a 3%/3 mm gamma passing rate criteria was used. With the guidance of 18 F-FMISO PET/CT imaging, dose escalation to hypoxic zones within NPC could be achieved and delivered efficiently with the VMAT technique in comparison with the IMRT technique.

Qiu J ，Lv B ，Fu M ，Wang X ，Zheng X ，Zhuo W ... -  《-》