Lin Zhu, Bailin Zhang, Qiang He, Geng Yang, Huaizhi Jin, Fei Li, Haoyu Meng, Wanwei Jian, Xuetao Wang
{"title":"Dosimetric evaluation of beam block techniques in helical tomotherapy for extranodal nasal-type NK/T-cell lymphoma.","authors":"Lin Zhu, Bailin Zhang, Qiang He, Geng Yang, Huaizhi Jin, Fei Li, Haoyu Meng, Wanwei Jian, Xuetao Wang","doi":"10.1016/j.meddos.2026.04.008","DOIUrl":null,"url":null,"abstract":"<p><p>The aim of the study was to evaluate the dosimetric effects of different virtual beam block combinations on target coverage, organ at risk (OAR) sparing, and delivery efficiency in helical tomotherapy (HT) for extranodal nasal-type NK/T-cell lymphoma (ENKTCL-NT). In addition, normal tissue complication probability (NTCP) modeling was used to assess the biological impact on OARs and to inform optimal treatment planning strategies. Twenty-six patients with stage I-II ENKTCL-NT were retrospectively analyzed. Three virtual beam block configurations for the lens and eyeball-B-OFF, B-LEN, and B-L&E-were generated. Dosimetric parameters of the target volume, physical and biological indices of OARs, monitor units (MUs), and beam-on time (BOT) were compared among the plans. Dose delivery accuracy was verified using the ArcCHECK phantom. All 3 plans achieved clinically acceptable target coverage without significant differences in target dosimetric parameters. Compared with B-OFF, B-LEN significantly reduced the maximum dose (D<sub>max</sub>), mean dose (D<sub>mean</sub>), equivalent uniform dose (EUD), and NTCP of the bilateral lenses (all p < 0.05) but did not significantly affect the eyeball dose (p > 0.05). B-L&E provided further protection: relative to B-LEN, it reduced the D<sub>max</sub> of the left and right lenses by 3.4% and 5.9%, D<sub>mean</sub> by 5.0% and 4.9%, and median NTCP by 10.3% and 21.4%, respectively (all p < 0.05). It also significantly lowered the D<sub>max</sub> and D<sub>mean</sub> of the eyeballs (p < 0.05). No significant differences were observed among the 3 plans for the brainstem, spinal cord, optic chiasm, or optic nerves (p > 0.05). Compared with B-OFF, B-L&E increased the MUs by 17.9% and BOT by 58 s (19.0%). Gamma passing rates (3%/2 mm) exceeded 90% for all the plans, meeting the American Association of Physicists in Medicine Task Group No. 218 (AAPM TG-218) clinical criteria. The virtual beam block technique in HT effectively reduces radiation exposure to the lens and eyeball while maintaining target coverage in ENKTCL-NT. The B-L&E configuration offers the greatest OAR protection, and B-LEN may be preferable when shorter treatment times are required.</p>","PeriodicalId":49837,"journal":{"name":"Medical Dosimetry","volume":" ","pages":""},"PeriodicalIF":1.7000,"publicationDate":"2026-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Medical Dosimetry","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1016/j.meddos.2026.04.008","RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"ONCOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
The aim of the study was to evaluate the dosimetric effects of different virtual beam block combinations on target coverage, organ at risk (OAR) sparing, and delivery efficiency in helical tomotherapy (HT) for extranodal nasal-type NK/T-cell lymphoma (ENKTCL-NT). In addition, normal tissue complication probability (NTCP) modeling was used to assess the biological impact on OARs and to inform optimal treatment planning strategies. Twenty-six patients with stage I-II ENKTCL-NT were retrospectively analyzed. Three virtual beam block configurations for the lens and eyeball-B-OFF, B-LEN, and B-L&E-were generated. Dosimetric parameters of the target volume, physical and biological indices of OARs, monitor units (MUs), and beam-on time (BOT) were compared among the plans. Dose delivery accuracy was verified using the ArcCHECK phantom. All 3 plans achieved clinically acceptable target coverage without significant differences in target dosimetric parameters. Compared with B-OFF, B-LEN significantly reduced the maximum dose (Dmax), mean dose (Dmean), equivalent uniform dose (EUD), and NTCP of the bilateral lenses (all p < 0.05) but did not significantly affect the eyeball dose (p > 0.05). B-L&E provided further protection: relative to B-LEN, it reduced the Dmax of the left and right lenses by 3.4% and 5.9%, Dmean by 5.0% and 4.9%, and median NTCP by 10.3% and 21.4%, respectively (all p < 0.05). It also significantly lowered the Dmax and Dmean of the eyeballs (p < 0.05). No significant differences were observed among the 3 plans for the brainstem, spinal cord, optic chiasm, or optic nerves (p > 0.05). Compared with B-OFF, B-L&E increased the MUs by 17.9% and BOT by 58 s (19.0%). Gamma passing rates (3%/2 mm) exceeded 90% for all the plans, meeting the American Association of Physicists in Medicine Task Group No. 218 (AAPM TG-218) clinical criteria. The virtual beam block technique in HT effectively reduces radiation exposure to the lens and eyeball while maintaining target coverage in ENKTCL-NT. The B-L&E configuration offers the greatest OAR protection, and B-LEN may be preferable when shorter treatment times are required.
期刊介绍：
Medical Dosimetry, the official journal of the American Association of Medical Dosimetrists, is the key source of information on new developments for the medical dosimetrist. Practical and comprehensive in coverage, the journal features original contributions and review articles by medical dosimetrists, oncologists, physicists, and radiation therapy technologists on clinical applications and techniques of external beam, interstitial, intracavitary and intraluminal irradiation in cancer management. Articles dealing primarily with physics will be reviewed by a specially appointed team of experts in the field.
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