Journal of Thai Association of Radiation Oncology

Immobilization Devices for Proton Therapy in Head and Neck Cancer: The Role of Radiation Therapists

2025-10-27T15:15:44+07:00

Head and neck cancers present significant therapeutic challenges in radiation oncology due to the proximity of multiple radiosensitive organs and critical structures. Proton therapy has emerged as a specialized technique to minimize unintended doses to surrounding normal tissues, leveraging the physical properties of the Bragg peak to achieve maximal dose deposition at a precise depth. However, the therapeutic advantages of proton therapy are strictly dependent on highly accurate and reproducible patient immobilization. This review highlights the clinical importance of immobilization in proton therapy for head and neck malignancies and describes the essential roles of radiation therapists in device preparation and treatment simulation. By examining the technical processes of patient positioning and the utilization of various immobilization systems—including thermoplastic masks, specialized head and neck cushions (e.g., cushions), bite blocks, and related supportive accessories—this article summarizes a CT simulation workflow based on clinical experience and evidence from relevant literature. Effective immobilization is shown to reduce patient motion and breathing-induced variations, thereby minimizing range uncertainty and ensuring positional reproducibility across the entire treatment course. Furthermore, appropriate immobilization strategies decrease radiation exposure to organs at risk, directly enhancing the precision and safety of proton therapy. Consequently, the selection of appropriate devices, combined with the meticulous technical practice of skilled radiation therapists, remains a cornerstone of treatment accuracy and patient safety in this complex anatomical region.

Lung cancer radiotherapy using end expiration breath hold technique with respiratory gating for scanners (RGSC) and linear accelerator at Siriraj hospital

2026-01-08T11:55:40+07:00

Respiratory motion, or lung movement resulting from breathing, is an important factor that causes uncertainty in the target position during radiation treatment for lung cancer, and may affect the accuracy and safety of the treatment. This article presents technical and practical guidelines for radiation treatment of lung cancer using the end-expiration breath-hold (EEBH) technique with respiratory gating for scanners (RGSC) and a linear accelerator, covering the patient selection process and preparation procedures, including breath-hold training, computed tomography simulation (CT simulation) under EEBH conditions, and advanced radiation therapy planning. Additionally, it encompasses the process of radiation delivery and position monitoring using kV-kV and cone beam CT (CBCT) images to ensure the consistency of the patient’s radiation position in clinical settings. Furthermore, it discusses the considerations for using EEBH techniques in medical practice, such as patient cooperation, reproducibility of breath holding, pre-treatment training, and position monitoring in each fraction to maintain the quality and safety of treatment. Therefore, these guidelines are technical reports and medical practice. These are not evaluating comparative results. However, this article can serve as a reference guide for radiotherapy treatment workflows in institutions with similar resources and technology.

Proton Therapy in Liver Cancer at King Chulalongkorn Memorial Hospital, Thai Red Cross Society: Technical and Clinical Implementation

2026-01-19T13:43:33+07:00

Proton beam therapy is an effective and highly precise treatment option for liver cancer, owing to the unique physical properties of protons that allow maximal energy deposition at the tumor site while minimizing radiation exposure to surrounding normal tissues. This characteristic enables the delivery of high radiation doses for effective tumor control with a low incidence of treatment-related toxicity. However, proton therapy for liver cancer requires technically complex procedures, as the liver is a highly mobile organ and is located in close proximity to several critical structures. This article aims to present the technical approaches and clinical experience of proton beam therapy for liver cancer at King Chulalongkorn Memorial Hospital, Thai Red Cross Society. This article covers the entire treatment workflow, including simulation, patient positioning and selection of appropriate immobilization devices, respiratory motion management techniques, treatment planning, and image guidance. These components play a crucial role in reducing uncertainties, enhancing treatment accuracy, and minimizing radiation-induced toxicity to adjacent critical organs, such as the stomach, intestines, and kidneys.

Marker-less patient setup applications of surface-guided radiotherapy and quality assurance: An institutional experience

2026-04-01T12:46:45+07:00

Surface-guided radiotherapy (SGRT) has been increasingly implemented in modern radiation therapy practice. It can be utilized for patient positioning and real-time monitoring of organ motion during treatment. Furthermore, the system enables automatic beam interruption when the motion of the target or organ of interest deviates from the planned treatment position. Therefore, quality assurance (QA) of SGRT systems is essential to ensure treatment accuracy and patient safety. SGRT QA can generally be categorized into three levels: daily, monthly, and annual procedures. This article presents our institutional experience in the clinical application of SGRT for patient setup in radiation therapy, as well as the implementation of quality assurance procedures for the SGRT system. The aim is to provide practical guidance for the implementation and further development of SGRT in radiotherapy practice.

Comparison of lung tumor position for image guided radiotherapy between Three Dimensional Cone beam computed tomography and Four Dimensional Cone beam computed tomography

2025-11-05T12:33:55+07:00

Backgrounds: Stereotactic Body Radiotherapy (SBRT) for lung cancer requires high precision because lung tumors move with respiration. Treatment planning using four-dimensional computed tomography (4D-CT) has therefore been employed. During treatment, image-guided radiation therapy (IGRT) is essential to verify tumor positioning. Both three-dimensional cone-beam CT (3D-CBCT) and four-dimensional cone-beam CT (4D-CBCT) are available, but their accuracy remains debatable. This study aims to compare matching error between these two techniques relative to average intensity projection (AIP) from 4D-CT.

Objectives: To evaluate the matching error of lung tumor positioning using 3D-CBCT and 4D-CBCT compared with 4D-CT. And to assess the feasibility of using 3D-CBCT as an alternative to 4D-CBCT.

Materials and Methods: This was a retrospective study of nine patients with lung cancer who underwent stereotactic body radiotherapy (SBRT). Tumor positioning was verified prior to each treatment fraction using image-guided radiotherapy with both three-dimensional cone-beam computed tomography (3D-CBCT) and four-dimensional cone-beam computed tomography (4D-CBCT), respectively, on a Varian TrueBeam system between 2018 and 2021. The data consisted of average intensity projection (AIP) images from 4D-CT (9 datasets) and a total of 61 sets each of 3D-CBCT and 4D-CBCT images. Matching error in the anterior–posterior(AP), superior–inferior(SI), and left–right(LR) directions were compared using an auto-matching method. Statistical analysis was performed using a paired t-test, with statistical significance defined as p < 0.05.

Results: Mean matching errors relative to AIP from 4D-CT : 3D-CBCT: AP -0.31 ± 1.75 mm, SI -1.13 ± 1.57 mm, LR -0.33 ± 0.69 mm ,4D-CBCT: AP -0.28 ± 1.92 mm, SI -0.80 ± 2.00 mm, LR -0.31 ± 0.67 mm The largest mean matching errors between the two techniques was in the SI direction -0.34 mm(p=0.26), followed by AP -0.03 mm(p=0.85) and LR -0.02 mm(p=0.82). No statistically significant differences were found (p> 0.05), and all values were within the 5 mm planning target volume (PTV) margin.

Conclusion: Both 3D-CBCT and 4D-CBCT demonstrated comparable accuracy when referenced to AIP from 4D-CT, with no statistically significant differences. These findings suggest that in institutions without 4D-CBCT, 3D-CBCT can be used as a clinically acceptable alternative for lung SBRT positioning verification.