Reduced volume intensity-modulated radiotherapy with simultaneous integrated boost for patients with high-grade glioma: A retrospective observational study.

Radiotherapy (RT) is an essential treatment for patients with high-grade gliomas. however, a consensus on the target area of RT has not yet been achieved. In this study, we aimed to analyze progression-free survival (PFS), recurrence patterns, and toxicity in patients who received reduced volume intensity-modulated radiotherapy with simultaneous integrated boost (rvSIB-IMRT). In addition, we attempted to identify prognostic factors for recurrence. Twenty patients with high-grade gliomas who received rvSIB-IMRT between July 2011 and December 2021 were retrospectively analyzed. For rvSIB-IMRT, clinical target volume 1/2 was set at a 5 to 10 mm margin on each gross tumor volume (GTV) 1 (resection cavity and enhanced lesion) and GTV2 (high-signal lesion of T2/fluid-attenuated inversion recovery). RT doses were prescribed to 60 Gy/30 fractions (fxs) for planning target volume (PTV)1 and 51 to 54 Gy/30 fxs for PTV2. The median PFS and overall survival of the total cohorts were 10.6 and 13.6 months, respectively. Among the 12 relapsed patients, central, in-field, and marginal recurrences were identified in 8 (66.7%), 2 (16.7%), and 1 patient (8.3%), respectively. Distant recurrence was identified in 3 patients. Gross total resection (GTR) and high Ki-67 index (>27.4%), and subventricular involvement (SVI) were identified as significant factors for PFS in the multivariate analysis. During the follow up, 4 patients showed pseudoprogression and 1 patient showed radiation necrosis. The rvSIB-IMRT for high-grade gliomas resulted in comparable PFS and tolerable toxicity. Most recurrences were central/in-field (10 cases of 12, 83.4%). GTR, high Ki-67 index (>27.4%), and SVI were significant factors for recurrence.

Development of a compact X-band linear accelerator system mounted on an O-arm rotating gantry for radiation therapy.

A compact X-band linear accelerator (LINAC) system equipped with a small and lightweight magnetron was constructed to develop a high-precision image-guided radiotherapy system. The developed LINAC system was installed in an O-ring gantry where cone-beam computed tomography (CBCT) was embedded. When the O-arm gantry is rotated, an x-ray beam is stably generated, which resulted from the stable transmission of radio frequency power into the X-band LINAC system. Quality assurance (QA) tests, including mechanical and dosimetry checks, were carried out to ensure safety and operation performance according to the American Association of Physicists in Medicine's TG-51, 142, an international standard protocol established by accredited institutions. In addition, delivery QA of the radiotherapy planning system was conducted to verify intensity-modulated radiotherapy techniques. Therefore, it was demonstrated that the developed X-band LINAC system mounted on the O-arm gantry proved to be valid and reliable for potential use in CBCT image-guided radiation therapy.

Verification of lithium formate monohydrate in 3D-printed container for electron paramagnetic resonance dosimetry in radiotherapy.

The nondestructive dosimetry achieved with electron paramagnetic resonance (EPR) dosimetry facilitates repetitive recording by the same dosimeter to increase the reliability of data. In precedent studies, solid paraffin was needed as a binder material to make the lithium formate monohydrate (LFM) EPR dosimeter stable and nonfragile; however, its use complicates dosimetry. This study proposes a newly designed pure LFM EPR dosimeter created by inserting LFM into a 3D-printed container. Dosimetric characteristics of the LFM EPR dosimeter and container, such as reproducibility, linearity, energy dependence, and angular dependence, were evaluated and verified through a radiation therapy planning system (RTPS). The LFM EPR dosimeters were irradiated using a clinical linear accelerator. The EPR spectra of the dosimeters were acquired using a Bruker EMX EPR spectrometer. Through this study, it was confirmed that there is no tendency in the EPR response of the container based on irradiation dose or radiation energy. The results show that the LFM EPR dosimeters have a highly sensitive dose response with good linearity. The energy dependence across each photon and electron energy range seems to be negligible. Based on these results, LFM powder in a 3D-printed container is a suitable option for dosimetry of radiotherapy. Furthermore, the LFM EPR dosimeter has considerable potential for in vivo dosimetry and small-field dosimetry via additional experiments, owing to its small effective volume and highly sensitive dose response compared with a conventional dosimeter.

Image similarity evaluation of the bulk-density-assigned synthetic CT derived from MRI of intracranial regions for radiation treatment.

OBJECTIVE: Various methods for radiation-dose calculation have been investigated over previous decades, focusing on the use of magnetic resonance imaging (MRI) only. The bulk-density-assignment method based on manual segmentation has exhibited promising results compared to dose-calculation with computed tomography (CT). However, this method cannot be easily implemented in clinical practice due to its time-consuming nature. Therefore, we investigated an automatic anatomy segmentation method with the intention of providing the proper methodology to evaluate synthetic CT images for a radiation-dose calculation based on MR images. METHODS: CT images of 20 brain cancer patients were selected, and their MR images including T1-weighted, T2-weighted, and PETRA were retrospectively collected. Eight anatomies of the patients, such as the body, air, eyeball, lens, cavity, ventricle, brainstem, and bone, were segmented for bulk-density-assigned CT image (BCT) generation. In addition, water-equivalent CT images (WCT) with only two anatomies-body and air-were generated for a comparison with BCT. Histogram comparison and gamma analysis were performed by comparison with the original CT images, after the evaluation of automatic segmentation performance with the dice similarity coefficient (DSC), false negative dice (FND) coefficient, and false positive dice (FPD) coefficient. RESULTS: The highest DSC value was 99.34 for air segmentation, and the lowest DSC value was 73.50 for bone segmentation. For lens segmentation, relatively high FND and FPD values were measured. The cavity and bone were measured as over-segmented anatomies having higher FPD values than FND. The measured histogram comparison results of BCT were better than those of WCT in all cases. In gamma analysis, the averaged improvement of BCT compared to WCT was measured. All the measured results of BCT were better than those of WCT. Therefore, the results of this study show that the introduced methods, such as histogram comparison and gamma analysis, are valid for the evaluation of the synthetic CT generation from MR images. CONCLUSIONS: The image similarity results showed that BCT has superior results compared to WCT for all measurements performed in this study. Consequently, more accurate radiation treatment for the intracranial regions can be expected when the proper image similarity evaluation introduced in this study is performed.