Effect of Multi-Leaf Collimator Angle Optimization on the Planning Parameters in Intensity-Modulated Radiotherapy for Thoracic Tumors

Abstract

Introduction

To investigate the effect of multi-leaf collimator (MLC) angle optimization on the planning parameters in intensity-modulated radiotherapy (IMRT) for thoracic tumors.

Methods

Forty-two patients (21 esophageal cancer, 21 lung cancer) were retrospectively enrolled. For each patient, two IMRT plans were designed in Eclipse treatment planning system: one with the MLC angle set to 0°, which triggered automatic field splitting due to excessive X-jaw aperture; the other with the MLC angle adjusted to keep the X-jaw aperture below 13.8 cm, thereby avoiding field splitting. The homogeneity index (HI) and conformity index (CI) of target volume, doses of organs at risk (OARs), monitor units (MUs) and treatment time were compared. Dose verification was performed.

Results

For both esophageal and lung cancer patients, the two groups of plans met the clinical requirements and the dose distribution of target volume was similar. Compared with the plan of the MLC at 0°, the number of MUs and the treatment time were significantly reduced by adjusting the MLC angle to avoid automatic field splitting by the planning system. The average number of MUs in esophageal cancer and lung cancer patients was reduced from 1015.7 ± 162.8 and 1122.0 ± 315.3 to 853.3 ± 113.0 and 886.5 ± 264.8, respectively, and the average treatment time was shortened from 1.6 ± 0.3 min and 1.8 ± 0.6 min to 1.4 ± 0.2 min and 1.5 ± 0.5 min, respectively. The D_mean, V_5Gy and V_10Gy of the lung in patients with esophageal cancer and the D_mean, V_10Gy and V_20Gy of the lung in patients with lung cancer were significantly reduced (P < 0.05). Dose verification showed no significant difference between the two methods.

Conclusions

For thoracic tumors with a large transverse range, the method of adjusting the MLC angle to prevent automatic field splitting may effectively reduce MUs and treatment time while maintaining target coverage and OAR safety.

Keywords

multi-leaf collimator (MLC)thoracic tumors intensity-modulated radiotherapy (IMRT)monitor unit (MU)treatment time

Introduction

Lung cancer and esophageal cancer are two kinds of cancers with high incidence worldwide,¹ and they are very common malignant thoracic tumors in China, with high morbidity and mortality.^2,3 Concurrent chemoradiotherapy is a commonly used treatment, especially for patients with inoperable advanced tumors.^4-7 At present, in the radiotherapy plan design for thoracic tumors, the collimator jaw is mainly used to reduce the exposure dose to the organs at risk (OARs), thereby reducing the toxicity of radiotherapy, especially radiation pneumonitis.^8,9

In recent years, the wide application of intensity-modulated radiotherapy (IMRT) has significantly improved the conformity of dose distribution and target coverage.^10,11 However, there are still many optimizations in the planning design. The target volume of thoracic tumors is often distributed along the esophagus or bronchus in a long strip or oblique pattern, with a large transverse range. The Varian medical linear accelerator supports the “sliding window” technique for IMRT through multi-leaf collimator (MLC). There are two strategies for dealing with large target volume: firstly, the large field is divided into several sub-fields by automatic field splitting; the second is to use the large field intensity-modulated irradiation technique to achieve continuous irradiation by pausing the beam and adjusting the position of the jaws. When the X-axis field size is larger than 14.5 cm,¹² the field will be divided into two or more sub-fields for irradiation, or the large field intensity-modulated irradiation technique can be used to retain only one beam. However, the former significantly prolongs the treatment time due to multiple loading of field data and manual manipulation. The latter, although it reduces the number of operations, is still not conducive to the improvement of treatment efficiency due to the movement of the jaws and the increase in the beam pause time.

In this study, the MLC angle was adjusted to limit the aperture range of the X-jaw to avoid the occurrence of automatic field splitting. The effects of this method on the homogeneity index (HI) and conformity index (CI) of the target volume, dose distribution of OARs, treatment time, monitor units (MUs) and delivery accuracy were systematically evaluated, aiming to provide an efficient and safe plan design strategy for clinical practice.

Materials and Methods

Patient Characteristics

This retrospective cohort study encompassed a total of 42 patients who received IMRT in the Cancer Hospital of Shantou University Medical College from April 2021 to December 2023, including 21 patients with esophageal cancer and 21 patients with lung cancer. The age of esophageal cancer patients ranged from 47 to 87 years, with a median age of 66 years. The age of lung cancer patients ranged from 28 to 79 years, with a median age of 68 years. The pathological types, clinical stages and tumor volume of the patients are shown in Table 1. All patient details were de-identified. The reporting of this study conforms to STROBE guidelines.¹³

Table 1.

Clinicopathological Characteristics of the Patients (n=42)

	Pathological type			Clinical stage			Tumor volume
	Squamous cell carcinoma	Small cell carcinoma	Adenocarcinoma	II	III	IV	(cm³)
Esophageal cancer	20	0	1	2	9	10	262.2±210.6
Lung cancer	8	7	6	1	13	7	455.4±188.3

Note: Tumor volumes are presented as mean±standard deviation.

Image Acquisition

Patients were positioned in the supine position, immobilized with a thermoplastic mask (Guangzhou Klarity Medical and Equipment Co, Ltd, China) or vacuum bag (Medtec Medical, Inc, Buffalo Grove, IL, USA), and scanned with a spiral CT simulator (Philips Brilliance Big Bore Oncology Configuration, Cleveland, OH) at a slice thickness of 5mm. The CT images were transferred to the Eclipse v16.1 (Varian Medical Systems, Palo Alto, CA) treatment planning system through DICOM 3.0 network. The target volume and OARs were delineated by radiotherapy doctors.

Plan Design

Forty-two patients were divided into an esophageal cancer cohort and a lung cancer cohort. For each patient, two types of plan were designed, including the automatic field splitting (AFS) plan and the no automatic field splitting (NAFS) plan. Five to seven coplanar sliding-window IMRT fields of 6-MV photons from a TrueBeam (Varian Medical Systems, Palo Alto, USA) linear accelerator were generated for each plan in Eclipse v16.1. In the AFS group, the MLC angle was set to 0°, resulting in automatic field splitting due to excessive X-jaw aperture width (> 14.5 cm). In these cases, the large field intensity-modulated irradiation technique was used to retain only one field. In the NAFS group, the MLC angle was adjusted according to the longest axis of the target volume, so that the leaf motion direction was perpendicular to the longest axis. The adjustment angles for esophageal cancer and lung cancer were 25.0 (5.0-90.0)° and 45.0 (14.0-90.0)°, respectively. The MLC was rotated to align the X-direction of the field along the shortest axis of the target in the beam’s-eye view (BEV), ensuring that the X-direction aperture remained under 13.8 cm and thereby preventing automatic field splitting by the treatment planning system. Therefore, the X-direction widths of the fields selected for angle optimization in AFS and NAFS groups for esophageal cancer were 16.6±1.3 cm and 13.2±1.5 cm, respectively, and those for lung cancer were 16.9±1.5 cm and 11.8±1.4 cm, respectively, with the differences between the two groups being statistically significant (P < 0.05). For the fields selected for angle optimization, the MLC rotation angles and X-direction widths are presented as box plots in Figure 1. In this study, two groups of plans were designed by the same physicist, and the number of fields, gantry angles and optimization conditions were consistent between the two groups. As shown in Figure 2, the layout of the six fields in a plan is presented, where the first and second columns are the BEVs in the AFS group, and the third column shows the BEVs in the NAFS group after adjusting the MLC angle.

Figure 1.

Box plots of rotation angles of multi-leaf collimator and X-direction widths of the fields selected for angle optimization between the automatic field splitting group (No. 1) and the no automatic field splitting group (No. 2).

Figure 2.

Beam’s-eye views of a treatment plan in the automatic field splitting group (a1–f1, a2–f2) and the no automatic field splitting group (a3–f3).

Evaluation Indicators

All plans were evaluated according to the parameters of the target volume and OARs in the dose volume histograms (DVHs). The evaluation indices of target volume were the HI and CI. The HI was calculated by the formula: HI = (D_2% - D_98%)/D_50%, while the CI was calculated using the formula (TV_RI/TV)×(TV_RI/V_RI). Here, D_2%, D_50% and D_98% represent the radiation dose received by 2%, 50% and 98% of the target volume, respectively. TV_RI is the target volume covered by the reference isodose line, TV represents the target volume, and V_RI represents the volume covered by the reference isodose line. The closer the HI value is to 0, the more homogeneous the dose distribution of the target volume is. The closer the CI value is to 1, the better the conformity of the target volume is. The evaluation indices of OARs included: (1) the percentage of the volume receiving doses of 5Gy, 10Gy, 20Gy and 30Gy (V_5Gy, V_10Gy, V_20Gy, V_30Gy) and the average radiation dose (D_mean) of the lung; (2) the D_mean of the heart; (3) the maximum dose (D_max) of the spinal cord and the spinal cord planning organ at risk volume (SC-PRV). In addition, the MUs and treatment time of the plans were also evaluated.

Dosimetric Verification

The delivery accuracy of each treatment plan was verified using a cylindrical ArcCHECK phantom (Sun Nuclear Corporation, Melbourne, FL, USA). The clinical plan was transferred to the phantom geometry for dose recalculation and delivered on the TrueBeam linear accelerator. The measured dose distribution was then compared with the planned dose distribution. Evaluation was performed in accordance with American Association of Physicists in Medicine (AAPM) TG-218 recommendations, employing a gamma index analysis with criteria of 3% dose difference, 2 mm distance-to-agreement, and a 10% dose threshold.¹⁴ The result was expressed as a gamma passing rate (%), and a plan was considered to have passed the verification if the rate was ≥ 95%.

Statistical Analysis

Statistical analyses were conducted using Statistical Package for the Social Sciences, version 25.0 (SPSS, Inc., Chicago, IL, USA). In this study, the MUs, treatment time, dose to OARs, HI, CI of target volume and gamma passing rate for each plan were reported as mean ± standard deviation (SD). According to the normality of the difference “d” distribution between the two groups, the paired-sample t-test or the Wilcoxon signed-rank test was used to compare the differences of planning parameters between the NAFS group and the AFS group. The statistical inference was based on two-tailed P values, with a significance threshold set at P < 0.05.

Results

The statistical results are presented in Tables 2 and 3. As shown in these two tables, the HI and CI values of the target volume were comparable between the AFS and NAFS groups, respectively, which indicated that the plans had similar target coverage. For esophageal cancer patients, while D_max of the spinal cord and SC-PRV, D_mean of the heart, V_20Gy and V_30Gy of the lung showed no significant differences between the AFS and NAFS groups (P > 0.05), the NAFS group exhibited significantly lower D_mean, V_5Gy and V_10Gy of the lung compared with the AFS group (P < 0.05), indicating advantages in reducing radiation dose to the lung. For lung cancer patients, there were no significant differences between the AFS and NAFS groups in terms of D_max of the spinal cord and SC-PRV, D_mean of the heart, V_5Gy and V_30Gy of the lung (P > 0.05), whereas D_mean, V_10Gy and V_20Gy of the lung showed significant differences (P < 0.05), with the NAFS group having more advantages in reducing radiation dose to the lung. In addition, the MUs and treatment time of the AFS groups were higher than those of the NAFS groups, and the differences were statistically significant (P < 0.05).

Table 2.

Comparison of Planning Parameters Between the Automatic Field Splitting Group (AFS Group) and the No Automatic Field Splitting Group (NAFS Group) for Esophageal Cancer Patients ( $\bar{X}$ ± SD)

	AFS group	NAFS group	t/z value	P value
Spinal cord_D_max (Gy)	39.2±2.6	39.2±2.6	-1.461	0.160
SC-PRV_D_max (Gy)	45.0±3.5	45.0±3.5	-0.014	0.989
Heart_D_mean (Gy)	15.2±12.7	15.3±12.8	-0.678	0.498
Lung_D_mean (Gy)	12.5±4.0	12.3±3.9	-3.025	0.002
Lung_V_5Gy (%)	61.7±23.9	59.7±22.7	-2.971	0.003
Lung_V_10Gy (%)	46.4±17.0	45.2±16.2	-3.140	0.002
Lung_V_20Gy (%)	24.1±7.5	24.0±7.6	-1.331	0.183
Lung_V_30Gy (%)	10.2±4.3	10.1±4.3	-0.203	0.839
Monitor unit	1015.7±162.8	853.3±113.0	-4.015	0.000
Treatment time (min)	1.6±0.3	1.4±0.2	-3.956	0.000
CI	0.9±0.0	0.9±0.0	-1.000	0.317
HI	0.1±0.0	0.1±0.0	0.000	1.000
Gamma passing rate (%)	98.4±0.9	98.5±1.0	0.000	1.000

CI, conformity index; HI, homogeneity index; A P value < 0.05 was considered statistically significant.

Table 3.

Comparison of Planning Parameters Between the Automatic Field Splitting Group (AFS Group) and the No Automatic Field Splitting Group (NAFS Group) for Lung Cancer Patients ( $\bar{X}$ ± SD)

	AFS group	NAFS group	t/z value	P value
Spinal cord_D_max (Gy)	37.7±6.0	37.4±5.9	-1.269	0.205
SC-PRV_D_max (Gy)	42.8±7.8	42.8±7.7	0.530	0.602
Heart_D_mean (Gy)	10.9±8.4	10.8±8.2	-1.721	0.085
Lung_D_mean (Gy)	15.0±3.3	14.9±3.3	2.862	0.010
Lung_V_5Gy (%)	59.7±10.6	59.4±10.3	-0.714	0.475
Lung_V_10Gy (%)	42.7±8.8	42.4±8.5	2.225	0.038
Lung_V_20Gy (%)	27.9±6.8	27.7±6.7	3.603	0.002
Lung_V_30Gy (%)	18.1±5.8	18.1±5.7	1.654	0.114
Monitor unit	1122.0±315.3	886.5±264.8	7.547	0.000
Treatment time (min)	1.8±0.6	1.5±0.5	7.716	0.000
CI	0.8±0.1	0.8±0.1	0.000	1.000
HI	0.1±0.0	0.1±0.0	-1.000	0.317
Gamma passing rate (%)	98.8±0.7	98.8±0.8	0.000	1.000

CI, conformity index; HI, homogeneity index; A P value < 0.05 was considered statistically significant.

The results of the ArcCHECK dose verification showed that in patients with esophageal cancer, the gamma passing rates for the AFS group and the NAFS group were 98.4% ± 0.9% and 98.5% ± 1.0%, respectively, with no significant difference between the two groups (P > 0.05). In patients with lung cancer, the gamma passing rates for the AFS group and the NAFS group were 98.8% ± 0.7% and 98.8% ± 0.8%, respectively, and the difference was also not statistically significant (P > 0.05). High gamma passing rates (≥ 95.6%) were observed in all patients, indicating that regardless of whether the MLC angle was adjusted, the treatment plans exhibited excellent deliverability and met the clinical requirements for treatment accuracy.

Figures 3 and 4 present the box plots comparing the radiation dose to the OARs, MUs, treatment time and gamma passing rate between the AFS and NAFS groups of plans for esophageal and lung cancer patients, respectively.

Figure 3.

Box plots of monitor units, treatment time, gamma passing rates, and lung, spinal cord, and heart doses between the automatic field splitting group (No. 1) and the no automatic field splitting group (No. 2) for esophageal cancer patients.

Figure 4.

Discussion

IMRT has been widely used in the treatment of thoracic tumors. Due to the special anatomical location of thoracic tumors, they are adjacent to OARs such as the lung, esophagus, heart, and spinal cord. At present, the research on the design of radiotherapy plans mainly focuses on how to arrange the radiation field,^15,16 or how to lock jaws to reduce the dose to OARs,¹⁷ while maintaining the conformity and homogeneity of the target volume.^18,19 Due to the irregular shape of the thoracic tumor, the target volume presents an oblique or transverse extension along the esophageal direction or bronchus, resulting in a large transverse range of the target volume. The infiltrative growth patterns of thoracic malignancies often lead to target volumes with a considerable lateral extent. For esophageal cancer, this is primarily due to circumferential invasion around the esophageal wall,²⁰ while for lung cancers abutting the mediastinum, it results from peribronchovascular spread or direct invasion into adjacent structures.²¹ However, the MLC motion range of Varian linear accelerator is limited, and the maximum cannot exceed 14.5 cm. When the target volume is larger than or close to this range, the planning system needs to split the field automatically, which results in an increase in treatment time and MUs.^22,23 In this cohort of 42 patients with lung cancer and esophageal cancer, we observed findings consistent with our preliminary analysis. The results demonstrated that adjusting the MLC angle to prevent automatic field splitting significantly reduced MUs and treatment time without compromising target coverage or increasing high-dose OAR exposure. Moreover, the mean lung dose, V_10Gy, V_5Gy (for esophageal cancer), and V_20Gy (for lung cancer) were reduced, and this reduction helps to lower the incidence of radiation pneumonitis, as previous studies^24,25 have shown that the parameters of mean lung dose, V_5Gy, V_10Gy and V_20Gy are closely related to radiation pneumonitis.

The results of this study showed that adjusting the MLC angle to avoid the automatic field splitting significantly reduced the average MUs for both esophageal and lung cancer by approximately 16% and 21%, respectively (P < 0.05). Since the scattered radiation deposited outside the treatment volume is proportional to the number of MUs delivered,^26,27 excessive MUs increase leakage radiation and out-of-field dose. Studies have shown that increased MUs may increase the risk of secondary cancer.^28,29 Therefore, our strategy is meaningful for mitigating this risk.

During the treatment, thoracic tumor may move with the respiration and the fluctuation of the thoracic cavity. Studies have shown that prolonged treatment time may increase the risk of tumor displacement during beam delivery.^30,31 Therefore, it is clinically essential to effectively reduce the treatment time to reduce the risk of tumor displacement. The results of this study showed that by adjusting the MLC angle to avoid the automatic field splitting in the treatment planning system, the treatment time was significantly shortened by approximately 13% for esophageal cancer and 17% for lung cancer (P < 0.05). A shorter treatment time is generally associated with better patient position stability and treatment accuracy, while reducing the likelihood of target volume deviation from the treatment iso-center.²⁶ Hoogeman’s study showed that the geometric error in the patient’s position during treatment is linear with treatment time, which means that even with immobilization techniques, patients may gradually drift away from their initial position during treatment, with the shift increasing with the duration of treatment.³⁰ For patients with thoracic tumors who have a large range of motion, reducing the total treatment time may reduce the discomfort of prolonged immobilization, reduce the uncertainty caused by factors such as changes in organ volume and organ motion, and improve the precision of treatment. In addition, reducing the total treatment time may improve the utilization and efficiency of linear accelerators, which is particularly important in the context of limited medical resources.

A large field size in the X-direction (the leaf motion direction) necessitates a wider physical travel range for the MLC leaves. If the MLC angle is not optimized, the direction of leaf travel may not be perpendicular to the longest axis of the target. In the worst-case scenario, it could be perpendicular to the shortest axis. This suboptimal alignment reduces the number of leaf pairs that span the entire width of the target volume, which are the leaves primarily responsible for beam modulation across that dimension. Consequently, the plan’s modulation efficiency is diminished, resulting in an increased number of MU. Conversely, by optimizing the MLC angle to align the leaf motion direction perpendicular to the longest axis of the target, the number of MLC leaves effectively participating in modulation is maximized, while minimizing leaf travel distance. This enhances modulation efficiency, which is demonstrated to result in significantly lower dose to normal organs and decreased total MUs in the research by Kim et al..³² Moreover, it is difficult to completely avoid MLC leaf displacement errors during the accelerator operation, and a large MLC motion range may introduce more errors. By adjusting the MLC angle, the required leaf travel distance is significantly shortened, helping to reduce the workload of the MLC and the possibility of MLC interlocking. Additionally, this MU reduction is also achieved by eliminating the need for field splitting. As demonstrated by Cao et al.,¹⁷ segmented jaw-locking strategies (SJL-IMRT) lead to higher total MUs, as they require the delivery of multiple sub-fields. In contrast, our strategy avoids field splitting, thereby simplifying the delivery and reducing the total MU count. As supported by Mu et al.,³³ plans with lower complexity (characterized by fewer segments) are significantly less sensitive to MLC positioning errors. Since fewer segments inherently require less leaf motion between control points, our strategy may help to maintain, or potentially improve, delivery reliability by minimizing unnecessary mechanical motion.

In addition, the inherent transmission through the MLC leaves for a 6MV photon beam from a TrueBeam linear accelerator is approximately 1.58±0.07%,³⁴ whereas the transmission through the jaws alone is substantially lower (typically <0.5%).^35,36 Optimizing the MLC angle allows the jaws to more closely conform to the target volume at the field edges. As the jaws have far lower transmission, this thereby reduces undesirable dose leakage into surrounding tissues, which is conducive to reducing the low-dose irradiation volume and the mean dose to the OARs.^37-39 Consistent with this mechanism, our results demonstrated that adjusting the MLC angle led to a significant reduction in the lung D_mean, V_5Gy, V_10Gy and V_20Gy.

In addition to the dosimetric benefits, the deliverability of the optimized plans is a critical factor for clinical implementation. In this study, pre-treatment dose verification was performed using ArcCHECK, and the results showed that in both esophageal cancer and lung cancer patients, the gamma passing rates were high for both the AFS and NAFS groups, with no statistically significant differences between the two groups in either subgroup. These findings indicate that adjusting the MLC angle to avoid automatic field splitting does not compromise the deliverability of IMRT plans, regardless of tumor type. The high gamma passing rates suggest that the planned dose distributions could be accurately delivered to patients, which supports the clinical feasibility of this optimization strategy.

It is important to clarify that the proposed MLC angle optimization strategy in this study is inherently bound to the technical framework of fixed-gantry IMRT. In IMRT, the MLC angle can be independently optimized for each static gantry angle, allowing for a field-by-field tailoring of the leaf motion direction to the specific anatomy from each BEV. This degree of per-field control enables us to adjust the MLC angle to reduce the required X-jaw opening, thereby preventing the treatment planning system from triggering automatic field-splitting for large targets. In contrast, the technique of volumetric modulated arc therapy (VMAT) operates on a fundamentally different paradigm. Firstly, the gantry rotates continuously during delivery while the MLC angle remains fixed for the entire arc, and this technical constraint makes the MLC angle unable to be optimized for each gantry angle. Secondly, VMAT does not utilize field-splitting as a planning strategy for extensive target volume; its dose is delivered through one or more continuous gantry rotations. Consequently, this planning strategy to optimize the MLC angle and thus avoid the issues caused by forced field-splitting may not be suitable for the VMAT planning.

There are three limitations in this study. Firstly, all plans were generated on the basis of a single treatment planning system (Varian Eclipse v16.1). The logic for automatic field splitting, the optimization algorithms, and X-jaw limiting settings may vary across different planning systems or software versions (e.g., RayStation, Pinnacle). Therefore, the generalizability of our conclusions to other platforms requires verification. In particular, the collimator design of Elekta linear accelerators differs from that of Varian systems; the Elekta Agility collimator design integrates the MLC at the upper level, effectively eliminating the independent X-jaw and thus the field-splitting issue for wide targets. Consequently, the direct applicability of our MLC angle optimization strategy to platforms like the Monaco treatment planning system (commonly used for Elekta linacs) remains to be investigated. Secondly, this study only evaluated dosimetric parameters, MUs, and treatment time, delivery accuracy; it did not evaluate clinical endpoints such as tumor control rate, patient survival, or long-term radiation toxicity. Thus, the potential clinical benefit of this approach warrants further investigation in prospective studies. Finally, the strategy of avoiding field-splitting by optimizing the MLC angle is not a universally applicable solution. Its suitability depends on the geometric shape and orientation of the target volume and the mechanical constraints of the MLC system. For targets that are extremely irregular in shape or extend beyond a certain critical width, rotating the MLC angle alone may be insufficient to prevent automatic splitting, and conventional field-splitting or alternative techniques (e.g., VMAT) may still be necessary. Therefore, clinical implementation should involve individualized assessment and plan comparison to select the most appropriate technique.

Despite these limitations, this study provides a feasible and practical strategy for improving the efficiency and dosimetric quality of large-field IMRT plans for thoracic tumors, within the specific technical framework investigated. The findings merit further validation and adaptation in broader clinical and technical contexts.

Conclusions

For thoracic tumors with a large transverse range, adjusting the MLC angle to avoid automatic field splitting is an efficient and reliable planning optimization strategy. On the premise of ensuring the dose coverage of the target volume and the safety of OARs, it may effectively reduce the number of MUs in the fields and the treatment time, and reduce the risk of secondary cancer and the risk of tumor movement during beam delivery.

Supplemental Material

Supplemental Material - Effect of Multi-Leaf Collimator Angle Optimization on the Planning Parameters in Intensity-Modulated Radiotherapy for Thoracic Tumors

Supplemental Material for Effect of Multi-Leaf Collimator Angle Optimization on the Planning Parameters in Intensity-Modulated Radiotherapy for Thoracic Tumors by Chun-Yan Deng, Jia-Huan Cai, Ji-Yong Zhang and Jia-Yang Lu in Technology in Cancer Research & Treatment.

Footnotes

ORCID iD

Jia-Yang Lu

Ethical Considerations

This study was approved by the Medical Ethics Committee of Cancer Hospital of Shantou University Medical College (approval number: 2024046), and the ethical review was waived on the basis of the following reasons: this study is a retrospective data analysis study, does not involve the direct collection of patients’ identity information, does not interfere with the clinical diagnosis and treatment process, and all data have been anonymized. Due to the retrospective nature of this study, all data were anonymized, ensuring that no personal information of patients was disclosed at any stage, the ethics committee of the hospital waived the informed consent of the patients and confirmed compliance with the Declaration of Helsinki and the confidentiality of the patient data.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was sponsored by the Medical Research Foundation of Guangdong Province [A2022218], Science and Technology Innovation Strategy Special Foundation (Vertical Collaborative Management Direction) Project of Guangdong Province [Shan Fu Ke (2018) No. 157], and Medical and Health Science and Technology Program of Shantou City [Shan Fu Ke (2025) No. 96].

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The original contributions presented in the study are included in the article material. Further inquiries can be directed to the corresponding author.*

Supplemental material

Supplemental material for this article is available online.

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