Herein, we provide a concise review of the critical role of motion management in radiation therapy, with a focus on photon radiation therapy, real-time control of respiratory motion, and image-guided radiation therapy (IGRT) in lung stereotactic body radiation therapy (SBRT). The dynamic nature of human anatomy, particularly in regions prone to movement such as the thoracic and abdominal areas, poses significant challenges in accurately targeting tumors during radiation therapy. This review explores the implications of organ and tumor motion, emphasizing the necessity for precise treatment delivery. We assess the advancements in four-dimensional (4D) imaging techniques such as 4D computed tomography, which provide time-resolved images for enhanced treatment planning. The review highlights various motion management strategies, including motionencompassing methods, respiratory-gating, breath-hold techniques, and real-time tumor tracking, discussing their implementation and impact on treatment efficacy. The role of IGRT in lung SBRT is particularly emphasized, showcasing how real-time imaging and advanced targeting techniques enhance the precision of high-dose radiation delivery while minimizing exposure to surrounding healthy tissues. This comprehensive review aims to underscore the significance of integrating motion management in radiation therapy, highlighting its pivotal role in improving treatment accuracy, reducing toxicity, and ultimately enhancing patient outcomes in cancer care.

Purpose: This study assessed and compared the dosimetric performance of HyperArc and RapidArc in stereotactic radiosurgery (SRS) for a single brain metastasis.
Methods: Twenty patients with intracranial brain metastases, each presenting a distinct target volume, were retrospectively selected. Subsequently, volumetric modulated arc therapy (VMAT) plans were designed using RapidArc (VMAT_RA) and HyperArc (VMAT_HA) for each patient. For planning comparisons, dose-volumetric histogram (DVH) parameters for planning target volumes (PTVs) and normal brain regions were computed across all VMAT plans. Subsequently, their total monitor units (MUs), total beam-on times, and modulation complexity scores for the VMAT (MCS_v) were compared. A statistical test was used to evaluate the dosimetric disparities in the DVH parameters, total MUs, total beam-on times, and MCS_v between the VMAT_HA and VMAT_RA plans.
Results: For the PT Vs, VMAT_HA presented a higher homogeneity index (HI) than VMAT_RA. Moreover, VMAT_HA p resented s ignificantly s maller g radient i ndex ( GI) v alues (P<0.001) than VMAT_RA. Thus, VMAT_HA demonstrated better performance in the DVH parameters for the PTV than VMAT_RA. For normal brain tissues, VMAT_HA p resented l ower v olume r eceiving 5 0% o f t he prescription dose and V_2Gy to the normal brain tissues than VMAT_RA (P<0.0001). While the total MUs required for VMAT_HA was significantly higher than those for VMAT_RA, the total beam-on time for VMAT_HA was superior to that for VMAT_RA.
Conclusions: Thus, VMAT_HA exhibited superior performance in achieving rapid dose fall-offs (as indicated by the GI) and a higher HI at the PTV compared to VMAT_RA in brain SRS. This advancement positions HyperArc as a significant development in the field of radiation therapy, offering optimized treatment outcomes for brain SRS.

Purpose: Accurate operation of the multi-leaf collimator (MLC), a key technology in intensity modulated radiation therapy (IMRT), is essential for safe and optimal radiation treatment. The Halcyon^TM linear accelerator has a collimator with low leakage and radiation transmission, making it suitable for IMRT. The limitations of the existing Halcyon^TM MLC quality assurance (QA) method were supplemented with a mathematical method, and the results were analyzed.
Methods: Electric portal imaging device (EPID) images obtained by performing the MLC QA plan on the Halcyon^TM was analyzed using Python. The picket fence tests were performed and compared using the maximum pixel value and mathematical methods. Dose rate, gantry speed, and leaf speed variation plan were performed for dose transmission comparison.
Results: For the maximum pixel value, the minimum distance between leaf junctions was 13.86 mm, and the maximum was 16.06 mm. However, for the mathematical method, the minimum and maximum were 14.54 mm and 15.68 mm, respectively. This suggests that setting the peak value to the highest value may cause an error in interpretation due to the limitations of the pixels of the EPID image. Performing QA on the remaining items confirmed that the measured values were within 3% of tolerance.
Conclusions: The presented analysis method applied to the MLC QA can derive more reasonable and valid values than existing methods, which will help with MLC monitoring by reducing errors in excessive interpretation.

Purpose: The use of two adjacent radiation beams to treat a lesion that is larger than the maximum field of a machine may lead to higher or lower dose distribution at the junction than expected. Therefore, evaluation of the junction dose is crucial for radiotherapy. Volumetric modulated arc therapy (VMAT) can effectively protect surrounding normal tissues by implementing a complex dose distribution; therefore, two adjacent VMAT fields can effectively treat large lesions. However, VMAT can lead to significant errors in the junction dose between fields if setup errors occur due to its highly complex dose distributions.
Methods: In this study, setup errors of ±1, ±3, and ±5 mm were assumed during radiotherapy for treating large lesions in the lower abdomen, and their effects on the treatment dose distribution and target coverage were analyzed using gamma pass rate (GP) and homogeneity index (HI). All studies were performed using a computational simulation method based on our radiation treatment planning software.
Results: Consequently, when the setup error was more than ±3 mm, most GP values using a 3%/3-mm criterion decreased by <90%. GP was independent of the direction of the field gap (FG), whereas HI values were relatively more affected by negative values for FG.
Conclusions: Therefore, the size and direction of setup errors should be carefully managed when performing dual-isocentric VMATs for large targets.