Precision Radiation Oncology最新文献

Purpose: This study investigates three different calibration methods for the selection of background pixel intensity.

Methods: Film-by-Film (FBF) Method: Each film serves as its own control. Batch-by-Film (BBF) Method: A single film is used as a control for all calibration films. Generic (GEN) Method: A generic value (65535) is used as the background pixel value for all calibration films.Three calibration curves were established for the red, green, blue, and RGB channels, and the Radbard NIH (image) curve-fitting model was used to predict the dose. Sensitivity at different dose levels was quantified by calculating the first derivative of each color channel.

Results: The GEN method exhibited a difference of up to 6% between the predicted and delivered doses below 2 Gy. The changes in optical density when using the GEN method differed significantly (p<0.0001) from those of the FBF and BBF methods. In the dose range 5-30 Gy, the percentage difference between the predicted and delivered doses for the FBF, BBF, and GEN methods was within 2%. Both the red and green channels demonstrated higher sensitivity than the blue channel over the dose range of 2-30 Gy.

Conclusions: The FBF method is more accurate than the BBF and GEN methods because it accounts for inter-film variations. The Radbard NIH (image) curve-fitting function proved suitable for predicting the dose for all the three calibration methods.

Temporal bone squamous cell carcinoma (TBSCC) is a rare and invasive malignant tumor. The common predisposing factors include a history of local radiotherapy and chronic suppurative otitis media. The current treatment approach for TBSCC primarily involves surgery, followed by adjuvant radiotherapy and chemotherapy, based on T staging and high-risk factors. Although patients with early-stage TBSCC have a high survival rate after treatment, the majority of patients are diagnosed in the intermediate to advanced stages, with extensive tumor involvement, posing challenges for surgical intervention. Definitive chemoradiotherapy (CRT) serves as a viable alternative for unresectable tumors. Constraints in administering curative radiation doses, due to the tolerance of surrounding organs, can lead to uncontrolled tumor growth. Although programmed cell death 1 inhibitors have demonstrated efficacy in head and neck squamous cell carcinoma and cutaneous squamous cell carcinoma, their application in TBSCC remains underexplored. Herein, we report a case of a 47-year-old man diagnosed with unresectable advanced and localized TBSCC. Following inadequate tumor control with primary chemoradiotherapy, immunotherapy was initiated, resulting in disease remission within a follow-up period of > 4 years.

Objective: This study aimed to analyze the effect of different gantry angles on portal imaging in terms of isocenter shifts and their dosimetric impact on dose delivery.

Methods: Thirty patients with head and neck cancers were prospectively selected for this study. The reference anterior to posterior (AP) digitally reconstructed reference radiograph image was obtained at a gantry angle of 0°. The AP portal images were acquired at angles of 0°, 0.5°, 1°, 1.5°, and 2.0°. The average deviation of the isocenter shift with respect to the zero-gantry angle was calculated. To check the dosimetric effects, the reference fluence was compared with different fluences measured at different isocenter shifts.

Results: The average isocenter shift differences in the lateral direction were 0.7 mm, 1.3 mm, 1.9 mm, and 2.5 mm. The average difference was <±0.1 mm for isocenter shift in the longitudinal direction. The results of the statistical analysis showed that the average isocenter shift and gamma pass rate with respect to the different isocenter position errors were significant in the lateral direction.

Conclusion: The results of this study showed that as the gantry angle increased, the isocenter shifted and the percentage of deviation in the lateral direction increased.

Esophageal cancer is among the top causes of cancer-related mortality worldwide, and the main treatment modality for locally advanced esophageal cancer is concurrent chemoradiotherapy. The current photon-based radiotherapy modalities and procedures have increased the incidence of treatment-related cardiac and pulmonary complications. Additionally, anatomical changes in the esophagus resulting from diaphragmatic movement, weight loss, and tumor progression present challenges for radiotherapy. These challenges have spurred interest in particle therapies, such as proton beam therapy (PBT) and heavy-ion therapy, for esophageal cancer. This paper comprehensively reviews the dosimetric advantages, clinical efficacy, and limitations of PBT and heavy-ion therapy for esophageal cancer and discusses their prospects. This highlights the unique dosimetric benefits of these therapies, particularly their ability to deliver high-dose radiation precisely to the tumor while sparing the surrounding normal organs and tissues. Although PBT and heavy-ion therapy demonstrate superior clinical efficacy compared to photon therapy, they are not without limitations. Multiple studies are needed to further validate and supplement the existing clinical and preclinical data to better exploit the benefits of PBT and thereby provide improved survival advantages to these patients.

Objective: Eye plaque radiation therapy is the treatment of choice for small- and medium-sized choroidal melanomas. This study investigated the dose distribution around eye plaques containing ¹²⁵I seeds to treat ocular melanoma using Monte Carlo N-Particle eXtended (MCNPX) and Plaque Simulator (PS) software.

Methods: Dosimetry evaluation and comparison of the resulting isodose curves for ¹²⁵I COMS plaques were performed using the MCNPX code. The isodose curves and dose distributions were calculated using PS treatment planning for a ¹²⁵I COMS plaque.

Results: In the validation, the maximum relative difference between the results of this study and those reported in other literature was approximately 9%-10% for the COMS plaques. The dose distributions of MCNPX were lower than those of PS with a relative difference of approximately 27.7%-35.4%. The dose distribution may differ depending on the ¹²⁵I source spectra and seed design used in the two methods. In addition, the dose algorithm used in PS made a major contribution to the relative differences between the results.

Conclusion: The PS did not provide accurate details of dose distribution near the surface of the plaque insert. The source parameters used in each program should be studied more carefully to determine the source of the differences in the estimated dose values.