Application of MR-guided radiotherapy for brain metastases / 中华放射肿瘤学杂志

Radiotherapy (RT) is the primary local treatment modality for brain metastases, which are common secondary malignancies. Image-guidance system such as cone beam computed tomography (CBCT) may be not applicable to adaptive radiotherapy (ART), as well as hypofractionated RT in brain metastases, because it cannot clearly show the shrinkage and deformation of intracranial tumors, and the peritumoral edema changes in a real-time manner. Magnetic resonance (MR) image has high spatial resolution and soft tissue contrast and no radiation dose burden compared with CBCT. MR-guided adaptive radiotherapy (MR-gART) allows real-time tracking of deformation and position changes of the intracranial tumors, and enables online planning reconstruction during the treatment process. MR-gART could deliver high dose irradiation to the tumors while reducing the radiation dose of important organs at risk around, which contributes to achieving precision RT. In this work, the application of MR-gART in brain metastases was reviewed.

Clinical implementation of MR-Linac systems in adaptive radiation therapy for head and neck cancer / 中华放射肿瘤学杂志

Adaptive radiation therapy (ART) has been proposed as a method to account for changes in head and neck cancer and normal tissues to enhance the therapeutic ratios. Online magnetic resonance-guided radiotherapy (MRgRT) using hybrid MR-Linac systems is a novel innovative application in ART for head and neck cancer. The concept of MR-Linac systems is the ability to acquire MR images for ART and also online imaging during treatment delivery. Daily ART allows to improve the targeting accuracy while avoiding organs at risk for head and neck cancer. Although an increasing number of studies related to clinical application and technical aspect of MRgRT in head and neck cancer have been published, MRgRT for ART of head and neck cancer remains in its infancy. The purpose of this article is to summarize and discuss the rationale, clinical implementation, and prospect of this promising adaptive radiotherapy modality for treating head and neck cancer.

Application and basic application process of MR accelerator in lung cancer / 中华放射肿瘤学杂志

Radiotherapy is one of the most important components of cancer treatment. Image-guided radiotherapy (IGRT) is the mainstream tool in the precision radiation oncology. Magnetic resonance (MR) accelerator can perform MRI for tumors during radiotherapy, deliver real-time tracing and monitoring of tumors and thus realize the MRI-guided adaptive radiotherapy. Here, the latest research status and clinical application of MR accelerator in lung cancer were reviewed.

Statistical analysis of duration of each phase of Unity MR-linac in clinical application / 中华放射肿瘤学杂志

Objective:To analyze the duration of each phase of Unity MR-linac in clinical application, aiming to provide reference for clinical optimization of the process time.Methods:Clinical data of 55 patients treated with Unity MR-linac were retrospectively analyzed. All patients were divided into the adapt to position (ATP) and adapt to shape (ATS) groups according to the planning method. The duration of each phase in the treatment process, the name and the time of each sequence, the number of beams, segments and total monitor units (MUs) were recorded and compared between two groups. In addition, the set-up time was counted according to different treatment sites. The time of each sequence and set-up time were expressed as the median M (Q 1, Q 3), and the number of beams, segments and total MUs of each plan were described as the mean±SD. Results:42 patients underwent ATP with a total of 305 treatment sessions: setup time was 3(2, 5) min, MR scanning time was 5(4, 7) min, registration time was 3(3, 4) min, adaptive planning time was 8(4, 12) min, beam on time was 8(6, 11) min, and the total time was 30(25, 36) min. 13 patients received ATS with a total of 65 treatment sessions: setup time was 2(2, 3) min, MR scanning time was 7(5, 8) min, registration time was 4(3, 5) min, time of delineation of target and organs at risk was 12(9, 16) min, adaptive planning time was 11(10, 14) min, beam on time was 10(9, 11) min and the total time was 55(49, 61) min. The set-up time according to treatment sites was 4(2, 4) min in the head and neck, 2(2, 4) min in the chest, and 3(2, 5) min in the abdomen. The number of fields, segments and total MUs during ATP were 8.1±1.7, 49.9±31.2, 846.75±363.44 in the head and neck, 8.0±2.0, 60.7±13.3, 790.21±279.00 in the chest, and 9.7±2.0, 81.2±22.3, 2007.32±1053.81 in the abdomen, respectively. The number of fields, segments and total MUs during ATS in head and neck of one case were 13, 39, 993.07, and 9.5±1.5, 65.5±6.3, 2763.26±835.41 in the abdomen.Conclusions:MR-guided radiotherapy yields huge potential in clinical application. However, there is still much room for the improvement of shortening the process duration.