Search Results (112)

Photodynamic therapy (PDT) is a promising treatment for pleural malignancies, yet accurate dosimetry remains challenging due to complex cavity geometries and the need to protect surrounding critical structures. The reactive oxygen species ([ROS]_rx) generated during treatment serve as a direct predictor of therapeutic efficacy. We developed a finite element model using COMSOL Multiphysics to simulate macroscopic photophysical kinetics, using clinical data inputs, including light fluence derived from a navigation system and patient-specific photosensitizer concentrations. Crucially, we integrated a deformable image registration framework to align intra-operative navigation data with pre-treatment CT scans, enabling the calculation of [ROS]_rx dose accumulation in critical Organs at Risk (OARs), such as the lung, heart, and esophagus. The model successfully reconstructed 3D [ROS]_rx distributions for multiple clinical cases. Point-to-point comparison at 32 detector locations across ten patients showed strong agreement between COMSOL-simulated and clinically calculated [ROS]_rx (mean percentage difference 0.6 ± 5.8%), while volume-averaged values differed by −6.0%, reflecting the enhanced spatial coverage of the 3D model relative to discrete sampling. The two-stage deformable registration improved CT-to-navigation surface alignment from HD95 = 4.08 mm to 1.78 mm (56.4% reduction) and MSD = 1.77 mm to 0.68 mm (61.5% reduction), enabling the first patient-specific mapping of [ROS]_rx onto OAR structures. This study demonstrates the feasibility of a comprehensive 3D dosimetry system for pleural PDT. By integrating kinetic modeling with deformable registration, we provide a robust platform for evaluating treatment efficacy and ensuring OAR safety, paving the way for eventual integration into treatment planning and real-time feedback. Full article

Background: This study evaluated the performance of a commercial offline adaptive radiotherapy system for systematic monitoring of breast cancer treatment with nodal irradiation using helical tomotherapy. Methods: Thirty patients treated for invasive unilateral breast carcinoma were analysed. For each patient, three megavoltage CT scans acquired at the first, middle, and last treatment sessions were processed through the PreciseART (Accuray, US) offline ART workflow. Automatically deformed structures were compared with manually delineated reference structures. Geometric accuracy was assessed using the Dice similarity coefficient (DSC), Hausdorff distance (HD95), mean distance to agreement (MDA), and barycentre distance (BD). The dosimetric parameters included D2% and V95% for targets and Dmean/Dmax/V20Gy for organs at risk. Results: Median DSCs exceeded 0.9 for the CTVbreast, PTVbreast, heart, and ipsilateral lung and were above 0.8 for the remaining structures, except the CTVn and oesophagus. Dosimetric differences between deformed and reference structures were within 5% for D2% across all targets and for V95% of the CTVbreast and PTVbreast in 90% of the sessions. The ipsilateral lung V20Gy differed by less than 5% in more than 90% of the sessions. Larger deviations (up to 10%) were observed for the nodal PTVs and mean heart dose, while the greatest inconsistencies were found for the oesophagus and spinal canal. Conclusions: The evaluated offline ART system demonstrates sufficient accuracy for automated monitoring of breast and lung structures. However, cautious interpretation remains necessary for nodal targets, heart, and oesophagus dosimetry prior to clinical implementation. Full article

Background/Objectives: Peritoneal micrometastases (micromets) remain a major barrier to durable cytoreduction in ovarian and other intra-abdominal cancers because lesions are difficult to visualize and are often resistant to systemic therapy. Liposomal doxorubicin (Dox) improves pharmacokinetics but can be limited by slow intratumoral release. Porphyrin-phospholipid (PoP) liposomes enable near-infrared light–triggered release of Dox (chemophototherapy (CPT)), creating an opportunity for intraoperative fluorescence-guided treatment planning and monitoring. Here, we evaluate a laparoscopic fluorescence imaging platform for quantifying light-triggered drug delivery. Methods: LC-Dox-PoP was applied to SCC2095sc and SKOV-3 cultures in 2D monolayers and 3D spheroid clusters. Dox fluorescence was quantified using a laparoscopic fluorescence imaging system over 1–9 μg/mL concentrations and compared with standard well-plate reader measurements. Porphyrin fluorescence was monitored to assess spheroid localization and photobleaching after activation light exposure. Results: For both cell lines, Dox fluorescence exhibited an approximate 4-fold increase at the maximum administered LC-Dox-PoP concentration, following a linear trend in both SCC2095sc and SKOV-3 cultures (R² = 0.97, 0.98 for 2D and R² = 0.98, 0.98 for spheroids). Laparoscope-derived fluorescence measurements agreed with well-plate reader measurements (R² = 0.89–0.96). Porphyrin fluorescence provided stronger complementary contrast for localizing spheroid constructs and decreased after activation light exposure, consistent with photobleaching during triggered release. Conclusions: These results support a quantitative imaging framework for fluorescence-guided monitoring of light-triggered liposomal drug release and may enable individualized CPT dosimetry for peritoneal micrometastases. Findings in SCC2095sc additionally suggest potential relevance of fluorescence-guided CPT for head and neck/oral cancer, where localized post-resection adjuvant treatment may improve control of residual disease. Full article

Additive manufacturing enables the rapid fabrication of radiographic phantoms for X-ray and CT imaging, supporting applications such as patient simulation, dosimetry, imaging protocol optimization, and quality assurance. Polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) are among the most widely used printing polymers in phantoms; however, their X-ray attenuation properties can vary substantially among manufacturers, product lines within manufacturers, and even between colors of the same product. Cylindrical samples of 34 PLA filaments from 11 manufacturers and 13 ABS filaments from 9 manufacturers were evaluated for X-ray attenuation and energy dependence between 70 and 140 kV using a clinical CT scanner. Measured mass densities ranged from 1.17 to 1.34 g/cm³ for PLA and 1.03–1.11 g/cm³ for ABS. At 120 kV, Hounsfield unit (HU) values spanned 109 to 424 HU for PLA and −34 to 40 HU for ABS. Energy dependence, quantified as the HU at 70 kV minus HU at 140 kV, ranged from −29 to +172 HU for PLA filaments and −52 to −4 HU for ABS filaments. Identical products differing only in color showed HU variations from <2 HU to >90 HU at 120 kV, with no consistent pattern linking specific colors to highest or lowest attenuation. These findings demonstrate that 3D printing materials require individual characterization, as base polymer designation alone does not predict X-ray behavior accurately. The observed variability, however, enables the design of phantoms with tailored attenuation and energy-dependent contrast. Referring only to base polymers when specifying 3D printing materials for radiographic phantoms or suggesting printing materials as radiographic substitutes to mimic a specified tissue or reference material without naming the actual product, including color, is, thus, insufficient. Full article

Background: Phantoms are essential in medical imaging, providing reproducible and quantitative means for system and protocol evaluation, image quality assessment, and dosimetry without patient exposure. Additive manufacturing enables rapid, accurate fabrication of phantoms ranging from simple geometries to complex anthropomorphic models. Ongoing developments in 3D printing technologies and polymer formulations have enhanced mechanical properties and printability, but also affect X-ray attenuation behaviour, necessitating an update with current materials to facilitate the choice of appropriate materials mimicking body tissues in radiographic phantoms. Methods: Attenuation properties of 27 photopolymer resins and 22 thermoplastic filaments (based on PLA, ABS, HIPS, PETG/PCTG, and PVB) were quantified using a clinical CT scanner at 70–140 kV to establish reference data for material selection. Results: At 120 kV, resins exhibited attenuation values between 124 and 384 Hounsfield Units (HU), and filaments ranged from −69 to 308 HU (PLA-based filaments: 160 to 241 HU, ABS: −32 to 43 HU, PETG/PCTG: 151 to 308 HU, and HIPS: −69 to −22 HU). Energy dependence of HU values is presented from 70 to 140 kV tube potential. Compared to the 2021 study, a wider selection of X-ray opacities is available. Regarding SLA/DLP printing, resins with higher attenuation were identified, and flexible resins that had provided a choice of low attenuation printing materials in the range of 60 to 90 HU at 120 kV tended to replicate attenuation properties closer to rigid photopolymers; i.e., HU values were slightly higher. In FDM filaments, a wide variation in different PLA-, ABS-, and HIPS-based filaments is found. In copolymers from the PET/PCTG/PETG family, very inhomogeneous X-ray attenuations are still found, as anticipated. Conclusions: The range of X-ray attenuation observed demonstrates that commercially available 3D printing materials can replicate clinically relevant tissues and tissue-equivalent contrasts. Furthermore, the available range of attenuations has increased, as has the finer gradation of these materials. These findings support the design of patient- and task-specific imaging phantoms for optimization of acquisition protocols, image quality evaluation, and radiation dose studies, as well as facilitate the selection of appropriate phantom materials. Full article

This study investigates the radiation-induced attenuation (RIA) of an Anti-Resonant Hollow-Core Fiber (AR-HCF) exposed to neutron and gamma radiation in a nuclear reactor environment. The AR-HCF—with a revolver-style structure—was characterized for RIA and compared to a solid, pure-silica-core fiber. Experimental results demonstrate that the AR-HCF exhibits substantially higher radiation tolerance compared to pure-silica, solid-core fibers, by about a factor of six in terms of dB/m. Numerical modeling in COMSOL Multiphysics (Version 6.3) was performed to simulate potential contributors of RIA, including silica compaction due to neutron fluence and changes in light confinement. These simulations ruled out these effects as primary causes of the measured attenuation. We also show that our results are consistent with the radiolytic generation of nitric acid within the hollow core, an interpretation that aligns with findings from a prior study. The results included in this manuscript provide insight into the behavior of AR-HCFs in the radiation field of a nuclear reactor, a topic with very limited prior literature, and underscore their potential for use in high-radiation environments such as fission and fusion reactors, particle accelerators, and space applications. The findings also point to promising future directions, including spectral characterization and dosimetry applications that leverage the unique properties of these fibers. Full article

Background/Objectives: Inter-platform variability in beam characteristics and low-dose exposure may arise from differences in linear accelerator head design, multileaf collimator geometry, and dose calculation algorithms. This study aimed to evaluate system-level dosimetric differences between two widely used linear accelerator platforms under clinically commissioned conditions. Methods: A comparative dosimetric analysis was performed between Elekta Synergy and Varian TrueBeam linear accelerators. Beam data were acquired using a SunSCAN™ 3D water phantom, and patient-specific quality assurance was conducted with the Octavius^® 4D system. Treatment plans were generated for left-sided breast, prostate, and head and neck cases using clinically commissioned treatment planning systems. Beam flatness, symmetry, penumbra width, low-dose exposure, conformity, homogeneity, and organ-at-risk dose metrics were evaluated. Results: Platform-dependent differences were observed in penumbra behavior and out-of-field dose, primarily attributable to intrinsic linac head design and collimation characteristics. These differences propagated into clinical plans, with greater variability observed for breast and head and neck cases, while prostate plans showed higher consistency between platforms. Algorithm-dependent trends were noted for conformity and homogeneity indices; however, all plans met institutional clinical acceptance criteria during quality assurance. Stricter gamma evaluation criteria revealed systematic but limited inter-platform deviations. Conclusions: Elekta Synergy and Varian TrueBeam demonstrated clinically acceptable dosimetric performance, with modest platform-dependent differences. While target coverage and overall plan quality were comparable, these variations were primarily observed in peripheral dose regions and may be relevant for platform-specific planning optimization and quality assurance. This supports the importance of comprehensive commissioning and QA procedures in both mixed- and single-platform clinical settings, particularly for highly modulated techniques. Full article

Background: Radiosensitizers can be used to enhance tumor response and mitigate toxicity in healthy tissues during radiation therapy. This study investigates the radiosensitizing potential of the metallacarborane Fe/⁵⁷Fe-ferrabisdicarbollide in SK-BR-3 and MDA-MB-231 breast cancer cells, using two distinct gamma-photon sources: high-dose ⁶⁰Co (2.08 Gy) and low-dose ⁵⁷Co (37.55 mGy, ⁵⁷Fe Mössbauer effect). Methods: We evaluated cell viability and survival in 2D monolayer and 3D spheroid cultures, as well as the mechanism of cell death (ROS production, apoptosis or necrosis). Computational dosimetry was used to calculate the average absorbed dose. Results: In 2D models, both radiation sources induced reduced viability and increased ROS, with distinct cell death patterns dependent on the source (apoptosis or necrosis). Comparing 2D and 3D MDA-MB-231 models revealed that spheroid survival was significantly more impaired. The low-dose ⁵⁷Co source caused a significant radiosensitization in MDA-MB-231 spheroids, dramatically impacting viability and survival. This effect is attributed to the Mössbauer effect, where the resonant absorption of 14.41 keV radiation by ⁵⁷Fe leads to a massive, localized dose enhancement. The subsequent cascade of Auger and conversion electrons (local high LET) caused significantly greater cellular damage than sparse photon radiation. Conclusions: Fe/⁵⁷Fe-ferrabisdicarbollide demonstrates a potent radiosensitizing effect depending on the cell model and the radiation source used. Crucially, the observed radiosensitization allows for the development of a new, more efficient cancer radiotherapy approach that can achieve therapeutic efficacy using a significantly lower radiation dose to the patient. This paves the way for safer and better-tolerated cancer treatments. Full article

Background: Malignant pleural mesothelioma (MPM) is an aggressive neoplasm, the major cause of which is asbestos exposure. Adjuvant radiotherapy after pleurectomy/decortication (P/D) aims at reducing locoregional recurrence but is limited by the risk of radiation pneumonitis (RP). In this study, we attempted to evaluate the predictive value of conventional and functional dosimetric parameters in assessing RP risk. Methods: This retrospective study analyzed 68 patients with non-metastatic MPM treated with adjuvant radiotherapy after P/D. Dosimetric parameters, including V20, V5, and mean lung dose (MLD), were calculated for both total lung volume and functional lung volume (FLV), with emphysematous regions excluded based on CT imaging thresholds. Statistical analyses assessed correlations between these parameters and acute RP incidence. Results: Acute RP developed in 42% of patients, and 28% had moderate-to-severe (Grade 2–3) events. V20 and FCL_V20 were significantly associated with the risk of RP (p = 0.017 and p = 0.028, respectively). Predictive accuracy for conventional V20 (AUC = 0.668) and Functional Contralateral Lung V20 (FCL_V20) (AUC = 0.655) showed moderate efficacy, without further significant improvement in using functional parameters. A V20 threshold > 1.8% predicted severe RP with high specificity (89.8%). Conclusions: While functional lung delineation provides an alternative in dosimetry, conventional V20 is a robust predictor of RP. Optimization of dosimetric constraints, in an effort to reduce pulmonary toxicity in MPM patients, should be further combined with advanced radiotherapy techniques and biomarkers. Full article

Transarterial radioembolization (TARE) is an established therapy for primary and secondary hepatic malignancies. Outcomes depend heavily on dosimetry, which has evolved from empirical and body-surface-area methods to partition and voxel-based approaches. This review summarizes current evidence for advanced (personalized) dosimetry across tumor types, highlights emerging dose–response concepts, and outlines practical barriers and implementation strategies. A narrative review of peer-reviewed clinical studies and trials evaluating dosimetry in TARE, with emphasis on hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (iCCA), metastatic colorectal cancer (mCRC), neuroendocrine tumor (NET), and breast cancer liver metastases, was performed with comparison of single-compartment medical internal radiation dosimetry method (MIRD), partition (multicompartment) methods, and voxel-based dosimetry methodologies. Personalized dosimetry improves outcomes in multiple tumor types. A randomized trial in HCC showed superior overall survival with partition-based dosing versus MIRD. In selective HCC treatments, voxel-derived metrics (e.g., D95) correlate with complete pathologic necrosis, suggesting benefit beyond mean dose targets. For iCCA, data associate higher tumor doses with better radiologic response, progression-free survival, and downstaging. In mCRC, voxel-based and threshold analyses link specific tumor and margin doses with metabolic/radiographic response and survival. Smaller series in NET and breast cancer indicate dose–response relationships using advanced dosimetry. Evidence supports broader adoption of advanced dosimetry in TARE. Emerging strategies that ensure adequate coverage of the “coldest” tumor regions and thoughtful particle-load planning may further optimize results. Standardized protocols, prospective validation, and scalable workflows are needed to accelerate implementation. Full article

Background/Objectives: To evaluate the efficacy of balloon occlusion trans-arterial hepatic radioembolization with Yttrium-90 (b-TARE) in optimizing dose activity in patients with large or multifocal Hepatocellular Carcinoma (HCC) lesions with heterogeneous macroaggregate distribution by retrospectively comparing outcomes with a similar cohort treated with standard TARE. Methods: This single-center restrospective study included sixty-three consecutive patients with unresectable HCC treated with TARE, of whom 24/63 had balloon-occluded TARE and 39/63 had standard TARE. Both cohorts included large or multifocal HCC lesions characterized by heterogeneous macroaggregate distribution, also in relation to the angiosome framework. The impact of b-TARE was analyzed using 2D and 3D dosimetry with dedicated software on post-procedural SPECT-CT. Dosimetric b-TARE results were retrospectively compared with standard TARE. Results: Both 2D and 3D SPECT-CT analyses demonstrated a better dosimetry profile in the b-TARE group. Concerning 2D evaluation, the activity intensity peak was significantly higher in the b-TARE group compared to the TARE group (998.6 ± 394.9 vs. 578.8 ± 313.3, p = 0.004). Regarding 3D dose analysis, the mean intra-lesion dose administered was significantly higher in the b-TARE group (162.7 ± 54.3 Gy vs. 111.2 ± 44.5 Gy, p = 0.01). There was no increase in significant complications or in the mean dose delivered to the normal liver in the b-TARE group. Conclusions: The employment of balloon occlusion in TARE was associated with a higher activity intensity peak and lesion absorbed dose on voxel-based dosimetry, compared to standard TARE, in patients with heterogeneous HCC and uneven macroaggregate distribution, without increasing mean non-tumoral liver dose. Full article

Background: Stereotactic radiotherapy (SRT) is a promising treatment option for patients with multiple brain metastases (BMs). Using one isocenter instead of a separate isocenter for each BM can reduce the treatment time. This work compares the calculated dose in the treatment planning system with the measured dose using film dosimetry of single-isocenter multi-target (SIMT) SRT for multiple BM. Methods: Fifty patients with 4 to 18 BMs (median = 6, in total 356 BMs) were treated with a single-isocenter non-coplanar LINAC-based treatment with six VMAT arcs. Treatment was performed using RayStation and Elekta Versa HD with Agility multileaf collimator, including a 6D robotic couch. Patient-specific QA measurements were performed with an in-house developed phantom using three layers of GafChromic EBT3 film. Film measurements were analyzed in DoseLab using global gamma with 3% and 1 mm distance-to-agreement criteria. Additionally, secondary dose calculations in Mobius3D were performed with similar gamma criteria. Results: The mean total Paddick conformity index and gradient index were 0.7 ± 0.10 and 5.2 ± 1.9, respectively. Monitor units used were 6321 ± 2510, and mean irradiation time was 600 ± 90 s. The mean global gamma passing rate for all measured films was 94.5 ± 4.6% with 3% and 1 mm criteria, while that of the dose calculations in Mobius3D was 98.2 ± 1.2% with the same criteria. A dependence of gamma passing rates of film measurements on the total PTV volume was observed, whereas such dependence was minimal for Mobius3D. Conclusions: The results demonstrate good agreement between the TPS, film measurements, and independent dose calculations, supporting the dosimetric accuracy of single-isocenter multi-target SRT for treating multiple BMs. Full article

Radioactive seed migration after low-dose-rate brachytherapy (LDR-BT) for prostate cancer is a known phenomenon; however, its clinical impact remains unclear. We retrospectively analyzed 611 patients treated with LDR-BT using loose iodine-125 seeds. Post-treatment imaging was used to assess seed migration. Treatment efficacy was evaluated using post-plan dosimetry (V100 and D90) and biochemical recurrence-free survival (bRFS). Seed migration was observed in 150 patients (24.5%) within 1–3 months post-treatment, involving a total of 210 seeds. Migration sites included lungs, vasculature, and seminal vesicles. Hematogenous migration was significantly associated with higher seed counts. Seminal vesicle migration was linked to increased needle usage and absence of neoadjuvant hormone therapy. No significant differences were observed in V100, D90, or bRFS between patients with or without seed migration. However, migration of ≥3 seeds correlated with significantly lower V100 and with a trend toward decreased bRFS. Limited seed migration appears to have minimal clinical impact. However, ≥3 migrated seeds may reduce dosimetric quality and affect treatment efficacy. Risk factors include larger prostate volume as well as higher seed and needle counts. Improved planning and using linked seeds may reduce migration and improve outcomes in LDR-BT for prostate cancer. Full article

Spatially fractionated radiotherapy (SFRT) is emerging as a powerful tool in cancer therapy for patients who are ineligible for treatment with clinically established irradiation techniques. Microbeam radiotherapy (MRT) is characterized by spatial dose fractionation in the micrometre range. This presents challenges in both treatment planning and dosimetry. While a dosimetry system with a spatial resolution of 10 µm and an option for real-time readout already exists, this system can only record dose in a very small volume. Thus, we are exploring dosimetry in an N-isopropylacrylamide (NIPAM) gel as an option for 3D dose visualization and, potentially, also three-dimensional dosimetry in larger volumes. In the current study, we have recorded the geometric patterns of single- and multiport irradiation with microbeam arrays in NIPAM gel. Data for 3D dose distribution was acquired in a 7T small animal MRI scanner. We found that the resolution of the gel is well suited for a detailed 3D visualization of microbeam patterns even in complex multiport geometries, similar to that of radiochromic film, which is well established for recording 2D dose distribution in MRT. The results suggest that a dose–response calibration is required for reliable quantitative dosimetry. Full article

The accurate calibration of radiochromic films is critical for high dose rate (HDR) brachytherapy dosimetry. Conventional workflows frequently rely on manually determined regions of interest (ROIs), which might increase operator variability. In this investigation, Gafchromic EBT3 films were irradiated under clinical settings at nominal doses of 0–10 Gy and evaluated using a MATLAB (R2024b)-based tool that allows for both manual and automated ROI selection. The calibration curves were modeled with a second-order polynomial and rational model, and performance was assessed using statistical measures. The study found that the rational model fits better than the polynomial model. Additionally, the automatic ROI approach outperformed the manual method in both models, resulting in higher calibration accuracy and reproducibility (R² = 0.999, RMSE = 0.118 Gy, MAE = 0.103 Gy vs. R² = 0.986, RMSE = 0.448 Gy, MAE = 0.388 Gy). Although manual ROI occasionally produced greater dose–response slopes at higher doses, it was more susceptible to operator bias and film non-uniformity. In contrast, automatic ROI reduced variability by consistently picking homogeneous sections, resulting in steady curve fitting across the entire dose range. Furthermore, a companion module transformed calibrated films into 2D false-color maps and 3D dosage surfaces, allowing for visual assessment of dose uniformity, detection of scanner-related aberrations, and quantitative verification for quality assurance. These findings demonstrate that automated ROI selection provides a more stable and reproducible foundation for film calibration in HDR brachytherapy, minimizing operator dependency while facilitating routine clinical quality assurance. Full article