Medical Dosimetry最新文献

To compare proton plans (IMPT) to VMAT plans and intercompare proton plans using 3 different spot sizes with robustness: cyclotron-generated proton beams (CPB) (σ: 2.7-7.0 mm), linear accelerator proton beams (LPB) (σ: 2.9-5.5 mm), and linear accelerator proton mini beams (LPMB) (σ: 0.9-3.9 mm) for the treatment of early-stage lung cancer. Twenty-two lesions from a total of twenty patients with early-stage lung cancer, originally treated with SBRT, were replanned using CPBs, LPBs, LPMBs, and VMAT using the same treatment planning system and dose calculation algorithm. The average intensity projected CTs (AIP-CT) were used for planning and 3D robust optimization was used for all proton plans. Conformity index (CI), homogeneity index (HI), R₅₀, lung V_20 Gy, and mean lung dose were compared among all proton plan types and with VMAT plans. Set-up uncertainties of ±5 mm and ±3.5% range uncertainty were included in the IMPT robust optimization and evaluation, using V_100%Rx > 98% of the ITV. The Wilcoxon signed-rank test was used to evaluate statistical differences between VMAT plans and all proton plan types. When compared to VMAT plans, all proton plans generally show improvement in CI, HI, Lung V_20 Gy, Mean lung dose, and R₅₀. The LPMB plans showed the most improvement from VMAT plans. Comparison between CPB and linear accelerator proton plans showed statistical significance (p < 0.05). R₅₀ and mean lung dose for the CPB, LPB and LPMB plans were 3.6 ± 0.9, 3.1 ± 0.8 and 2.6 ± 0.6; 2.2 ± 1.1 Gy, 1.9 ± 1 Gy and 1.6 ± 0.9 Gy, respectively (p < 0.05). The mean R₅₀ and mean lung dose from the VMAT plans were 4.1 ± 0.4 and 3.8 ± 2 Gy, respectively. The V_20 Gy (%) of lung and mean lung dose were improved across all proton plans when compared with those of VMAT plans. When evaluated for robustness in the worst-case scenario at V_100%Rx of the ITV > 98%, average ITV coverage of 98.6 ± 0.3%, 98.6 ± 0.6%, and 98.9 ± 0.6% were achieved for CPB plans, LPB plans, and LPMB plans, respectively. With decreased spot size, the LPB and LPMB plans are excellent alternatives to VMAT and cyclotron-generated proton plans with reduced dose to normal tissue and improved plan quality for early-stage lung cancer treatments.

One of the reasons for planning heterogeneity is lack of enough experience and recommendations on the quality of Linac-based stereotactic radiosurgery (SRS). In this study, our goal is to investigate the impact of planner's experience on the quality of Linac-based SRS plans for brain metastases (BMs) with varying levels of complexity. Specifically, to assess the impact of experience on the outcome of an automated noncoplanar treatment planning. A cohort of 120 patients with intracranial SRS plans, with a total of 633 BMs, was examined using VMAT delivery calculated with an available automated plan delivery system. Four planners with different levels of experience, ranging from under 1 year to over 5 years (Expert planner) of SRS planning, generated treatment plans. Dosimetric parameters and plan quality metrics were evaluated including: conformality index, homogeneity index, modulation factor, R_50%, total volume of brain receiving 12Gy, 6Gy, and 3Gy (V_12Gy, V_6Gy, V_3Gy) were assessed for each plan and compared with plan which was created by an expert planner with the highest planning experience. Experienced planners consistently produced acceptable plans, while less experienced one required revisions. Single BM cases showed minimal deviations in dosimetric parameters (under 10%) irrespective of planner experience. However, as the number and complexity of BMs increased, differences in plan quality became more pronounced. Moreover, expert planner's plans consistently outperformed others in terms of organs at risk sparing. This difference was particularly pronounced for cases involving the volume of healthy brain tissue. Our study underscores the critical role of planner's experience in the quality of Linac-based SRS plans using an automated planning. By standardizing and enhancing the planning process, the study aims to improve the quality of care for patients with multiple BMs, contributing to more efficient and effective treatments in the field of SRS.

We evaluated the effects of different aperture shape controller (ASC) settings on the dose distribution and delivery efficiency of lung stereotactic body radiotherapy (SBRT) using volumetric modulated arc therapy (VMAT) with a 10 MV flattening filter-free (FFF) beam. Ten lung SBRT cases with breath-holding were retrospectively analyzed by comparing plans with no-ASC and those with 5 ASC settings (very low, low, moderate, high, and very high). The gross tumor volume (GTV) coverage: D_98% (minimum dose to 98% of the volume), target conformity index (CI), gradient index (GI), D_2cm (dose maximum at 2cm from the planning target volume), lung dose, monitor unit (MU), modulated complexity score for VMAT (MCSv), and delivery time were evaluated. Compared with the no-ASC setting, there were no significant differences in GTV coverage, GI, or D_2cm in the different ASC settings. A very high ASC setting resulted in a slight increase in the mean lung dose metrics. On average, MU and delivery times were significantly reduced by approximately 200 MU and 5.0 s with very high ASC settings compared to the no-ASC setting. Plan complexity decreased as the ASC increased, with the very high ASC setting showing the highest MCSv values. This study suggests that the very high ASC setting may improve the delivery efficiency for lung SBRT using VMAT with the 10 MV FFF beam under breath-holding while maintaining comparable dose distributions and target coverage.

One major adverse effect of prostate radiotherapy is associated with the rectum. The SpaceOAR system has been developed to address this problem, as it enables treatment planning with a reduced dose to the rectum. This study aimed to evaluate and compare the treatment plans between three-dimensional conformal radiotherapy (3D-CRT) and volumetric modulated arc therapy (VMAT) for prostate cancer using the SpaceOAR system. Thirty-five patients treated with prostate cancer radiation using the SpaceOAR system received a total radiation dose of 60 Gy/20 fractions. The dose constraints and robustness of the plan for VMAT and 3D-CRT were compared. For 3D-CRT, 6-field conformal method and 2-arc conformal method were created and compared in 3 treatment plans together with VMAT. The dose-constraint evaluation was performed using the planning target volume (PTV), rectum (mean dose), bladder (mean dose), and femoral head (mean dose). One issue associated with prostate radiotherapy is the physiological movement of the target prostate gland, which reduces the accuracy of irradiation. The prostate moves several millimeters during irradiation due to physiological movements, and there are reports of a decrease in the PTV index due to this effect. This has a significant impact on the cure rate of prostate cancer. A comparative study of the 3 irradiation methods was conducted to investigate this issue. Each study item was analyzed using the Friedman test to determine the significance of the 3 irradiation methods. Our analysis showed that the dose constraint was statistically significant for VMAT, but 3D-CRT was also sufficient in achieving dose constraints. The hydrogel spacer reduced the rectal dose and improved the dose-constrained fulfillment rate in VMAT and 3D-CRT. In a study of prostate motion during irradiation, 3D-CRT, a robust plan, was superior in the PTV mean evaluation over VMAT, where the multileaf collimator moved in fine increments. VMAT is currently the standard treatment for prostate cancer; however, with the introduction of the SpaceOAR system using hydrogel spacers, 3D-CRT may also be a viable option for prostate cancer treatment.

Most of conventional 2-dimensional (2D) methods verify dose of multiple targets separately one-by-one for Single-isocenter Multiple-target (SIMT) brain plans, which are inefficient and sub-optimal. This study presented a practical method to verify the dose of 2 targets simultaneously for improved efficiency and accuracy. Fifteen Stereotactic Radiation Therapy (SRT) and sixteen Stereotactic Radiosurgery (SRS) plans were used for this study. Each plan has 2 targets coincide with a plane through the plan isocenter. All plans were created in the Eclipse Treatment Planning System (TPS) using a 6 MV flattening filter free photon beam. A 2D detector array, myQA SRS was used for measurements. It has a spatial resolution of 0.4 mm and an active area of 120 × 140 mm². It can be rotated along the longitudinal axis with a cylindrical phantom with one-degree precision. All plans were delivered with the detector array centered at the plan isocenter and rotated to intersect 2 targets. Six plans with target separations less than 70 mm were crosschecked with the SRS MapCHECK, which has an active area of 77 × 77 mm². The measured 2D dose distributions were compared with those calculated from the TPS. Gamma-index analysis was performed using 3%/1 mm criteria and a 10% dose threshold. For all 31 SIMT brain plans measured with myQA SRS, the average and standard deviation of the gamma-passing rate was (96.8 ± 2.2)%. For 15 SRT plans and 16 SRS plans, that was (96.6 ± 2.4)% and (97.0 ± 2.1)%, respectively. For 6 plans crosschecked, the average gamma-passing rates were 96.8% vs. 94.8% with myQA SRS and SRS MapCHECK, respectively. A practical method to verify the dose of 2 targets simultaneously was demonstrated. It offers an efficient way for pretreatment verification of SIMT SRT and SRS plans with improved accuracy.

Sweat gland cancers, particularly eccrine sweat gland carcinomas, are rare and challenging to treat due to their aggressive nature and inconspicuous clinical presentation. Aggressive digital papillary adenocarcinoma, a rare subtype, frequently presents with delays in diagnosis, increasing the risk of metastasis and recurrence. Surgical excision remains the standard treatment, but the role of postoperative radiation therapy is not well-established due to the paucity of data. This case study explores the use of radiotherapy in treating a 50-year-old female with digital papillary adenocarcinoma of the great toe. A custom three-dimensional (3D) printed bolus was utilized to improve dose distribution and reproducibility in radiation treatment using Volumetric Modulated Arc Therapy (VMAT). The comparative analysis of VMAT and 3D conformal radiation plans demonstrated superior target coverage, dose homogeneity, and reduced exposure to adjacent healthy tissue with VMAT. The findings contribute valuable insight into the use of 3D-printed bolus and advanced radiotherapy techniques in the management of rare sweat gland cancers, particularly in complex anatomical regions like the toe.

This study presents a patient with a PET-CT detected residual lacrimal sac tumor who was treated with intensity modulated proton therapy (IMPT) and concurrent chemotherapy. The patient a 49-year-old male diagnosed with squamous cell carcinoma of the left lacrimal sac had under-went endoscopic surgery. Postoperative PET-CT implied tumor residual in the left lacrimal sac. Given the tumor's proximity to optic organs, IMPT was employed to provide optimal dose painting. The precise delineation of the target volumes using multimodal imaging modalities (CT, MRI, and PET-CT), coupled with daily cone-beam CT technology for accurate positioning during radiotherapy contributed to an adequate dose coverage of the target. In comparison to helical tomotherapy (TOMO) and volumetric modulated arc therapy (VMAT), IMPT reduces doses to most ocular structures. With a follow-up period of 21 months after IMPT, the patient exhibited no evidence of disease recurrence and experienced only mild toxicity. This report highlights the critical role of multimodal imaging in diagnosis and radiotherapy planning. Furthermore, a literature review of proton therapy for malignant lacrimal sac tumors reveals that the scarcity of reports and emphasizes the importance of this case as a significant contribution to medical literature. This highlights the potential benefits of optimal tumor control and reducing toxicities by the integration of multimodal imaging and IMPT.

Uganda's only radiotherapy center is a very busy facility treating about 210 patients daily on three linear accelerators making it sometimes hard to have machine time for pretreatment QAs. This study was aimed at validating an independent calculation software, ClearCalc (ICS) for second checks of the treatment planning system (TPS) calculations. The validation of ICS started with simple phantom test plans consisting of square, irregular, open and wedged fields designed in the TPS and measured in phantoms. Doses and monitor units (MUs) calculated by ICS were compared with TPS calculated doses and with measured doses. ICS was then validated on clinically approved treatment plans: comparison with TPS calculations and with pretreatment QA measurements performed with electronic portal imaging devices (EPIDs) and analyzed using Gamma passing criteria of 3%/3 mm and 3%/2 mm. Results for test plans were within the passing level of 3.0% except for 2 outliers (-3.1% and 3.1%). As for the clinically approved treatment plans, they show good agreement between MUs (0.2 ± 1.8%), reference point doses (0.2 ±1.5%) and mean PTV doses (0.5 ± 1.4%). ICS calculated (3D) mean gamma pass rates were 98.1±1.6% and 98.4±1.0% for 3%/2 mm and 3%/3 mm criteria. No correlation was seen between gamma analysis results from ICS and EPID. This study validated ClearCalc on phantom and clinically approved plans. The result show that ICS based patients specific QA is quick, promising and potentially allows significant time saving that can be utilized for patient treatments.