Search Results (76)

Background/Objectives: Photon re-irradiation in previously treated head and neck cancer (HNC) is constrained by cumulative normal-tissue toxicity. Pencil-beam scanning intensity-modulated proton therapy (PBS-IMPT) allows for a sharper dose conformation than conventional photon techniques, which may widen the therapeutic window in previously irradiated tissue. Methods: Sixty-five patients with recurrent or second primary HNC were enrolled in a prospective single-institution registry and re-irradiated with PBS-IMPT between January 2020 and December 2025. Forty-five were treated with radical intent (69.2%), and 20 were treated postoperatively (30.8%), with a median prescribed dose of 66 Gy (RBE) in 30 fractions. Primary endpoints were overall survival (OS) and progression-free survival (PFS). Locoregional control (LRC), adverse events and the prognostic impact of anatomical extent were secondary endpoints. Results: The median follow-up was 9.3 months. The median OS was 17.2 months (95% CI 13.9–NR), with a 12-month rate of 67.1%. The median PFS was 10.1 months and the median LRC was 28.1 months. Central/skull-base involvement was associated with a non-significant trend toward worse OS (14.3 vs. 35.2 months; p = 0.062) and with significantly worse PFS (9.1 vs. 14.7 months; p = 0.037) than peripheral disease, but LRC did not differ between the groups (p = 0.240). Grade ≥ 3 oral mucositis occurred in 7.7%, with no grade 4–5 acute events. Within a median follow-up of 9.3 months, late osteoradionecrosis affected 6.2%, but late toxicity data remain preliminary given the short follow-up. Ninety-two percent of patients completed treatment. Conclusions: PBS-IMPT re-irradiation provided adequate survival with low acute toxicity. T3–T4 stage at re-irradiation was the only variable retaining significance for PFS on multivariable analysis (HR 4.32, 95% CI 1.24–15.13; p = 0.022). The poor survival observed for central/skull-base disease on Kaplan–Meier curves disappeared after T-stage adjustment, indicating the higher concentration of advanced disease in that compartment. Multicentre prospective data and longer follow-up are needed. Full article

Background and objectives: Previous dynamic collimator system (DCS) developments included: (1) hardware construction and commissioning, (2) an accurate dose calculation algorithm, (3) a quality assurance approach, and (4) development of optimization tools for treatment planning. Clinical DCS implementation necessitates efficient treatment plan delivery and fully integrated tools. In this work, a novel algorithm for minimizing treatment time was developed with the goal of reducing the DCS time increase, relative to conventional pencil beam scanning, to one minute or less per beam. In this extensive end-to-end evaluation, treatment plans generated with a modified U.S. Food and Drug Administration (FDA)-cleared treatment planning system were delivered on an Ion Beam Applications (IBA) Proteus Plus proton therapy system, with and without a DCS, to evaluate delivery times and dosimetric accuracy for a relatively large patient dataset, providing evidence of the clinical potential of the approach. Methods: Ten previously treated brain patients were replanned, consisting of both deep-seated central and superficial targets, the latter of which required an external 4 cm polyethylene range shifter. DCS treatments were optimized using a maximum conformity planning technique exploiting per-spot collimator capabilities. An optimization algorithm was incorporated to minimize treatment delivery time by determining the optimal sequencing of spot positions and collimator settings. Plan quality was quantified using conformity and dose-volume histogram (DVH)-based metrics while delivery accuracy was validated through measurements using both patient-specific quality assurance (PSQA) and log file analysis at the Miami Cancer Institute (MCI). Results: The DCS reduced the dose gradient index on average by 26.4% (17.7–37.1%) and the mean dose to the adjacent healthy tissue (within 10 mm of the target) by 19.3% (16.3–26.2%). The average reduction to the mean and maximum dose to the involved optic nerves was 50% (25.7–80.7%) and 18.7%, respectively, and the mean and D_2cc dose to the involved brainstem was reduced by 63.9% (31.5–96.4%) and 60.4% (10.8–99.8%), respectively. PSQA pass rates among DCS-collimated and baseline uncollimated treatments were 99.7% and 99.2%, respectively. DCS treatment fields were delivered within an average of 49 s (32–61 s) from their uncollimated intensity modulated proton therapy (IMPT) counterparts. Average spot position errors were −0.05 ± 0.2 mm and 0.04 ± 0.2 mm for the x- and y-position, respectively. The maximum error in magnitude for collimator positioning was 0.2 mm or less. Conclusions: DCS collimated IMPT treatments can provide significant dosimetric improvements over uncollimated treatments. These highly collimated treatments can be delivered with sufficient accuracy for clinical use while incurring an additional time penalty of around one minute or less per field compared to uncollimated treatments. Full article

The sharp dose gradients that underpin the dosimetric advantage of particle therapy over photon therapy can be undermined by the interplay effects due to intra-fraction motion in modern pencil beam scanning systems. Fluoroscopy-Guided Particle Therapy (FGPT) offers a promising path to improved motion management through real-time tracking of tumors or surrogate signals. The advent of flat-panel detector (FPD)-based technology has enabled tighter integration of fluoroscopy/fluorography into treatment units and accelerated clinical adoption and research, with commercial systems such as Hitachi’s Real-time Gated Particle Therapy (RGPT) now available. However, the need for implanted fiducial markers, with the associated invasiveness and risk of complications, limits the utility of RGPT to a few anatomic sites in selected patients. The full potential of FGPT, therefore, depends on reliable marker-less tumor tracking, which remains challenging because soft-tissue targets are obscured by overlapping anatomy along the X-ray path, leading to reduced reliability of traditional image-registration algorithms in the projection domain. Recent advances in deep learning and AI-driven image registration have renewed hope for overcoming these barriers, enabling real-time marker-less tracking for particle therapy. This review outlines the evolution of fluoroscopy technology from image intensifier (II) to FPD-based systems, summarizes historical and recent vendor-supported FGPT strategies, and surveys emerging AI-based algorithms in the literature. A general review of machine learning-based image registration is provided, challenges in generalizability and interpretability are highlighted, and potential paths toward reliable, clinically deployable FGPT are discussed. Full article

Background/Objectives: Proton therapy has emerged as an advanced radiotherapy modality due to its unique physical dose distribution and its distinct radiobiological properties. The finite range of protons in tissue enables highly conformal dose delivery with minimal exit dose, significantly reducing irradiation of surrounding normal tissues compared to photon-based radiotherapy. Beyond these physical advantages, proton beams exhibit a spatially varying linear energy transfer that increases toward the distal edge of the spread-out Bragg peak, leading to clustered and complex DNA damage that is more difficult for cancer cells to repair. Methods: This review integrates experimental, computational, and clinical evidence to examine how proton-induced DNA damage, relative biological effectiveness, oxygen effects, and non-targeted responses contribute to tumor control and normal tissue sparing. Results: Comparative analyses with photon intensity-modulated radiotherapy demonstrate consistent reductions in acute and late toxicities across multiple tumor sites, particularly in pediatric patients and in tumors located near critical organs. The review also discusses emerging technologies, including pencil beam scanning, image-guided and adaptive proton therapy, compact accelerator systems, and ultra-high dose rate FLASH proton therapy, which collectively aim to enhance treatment precision, biological effectiveness, and accessibility. Conclusions: Together, these developments support proton therapy as a rapidly evolving modality with significant potential to improve therapeutic outcomes in modern oncology. Full article

Background/Objectives: Traditionally, proton therapy assumes a fixed relative biological effectiveness (RBE) value of 1.1, which can lead to inaccurate dose calculations in treatment planning. This study examines the effect of dynamic arc delivery and pencil beam scanning (PBS) linear energy transfer (LET) optimization on LET-dependent RBE dose escalation to nervous tissue structures in head and neck (H&N) cancer patients undergoing proton beam therapy, utilizing two RBE dose models. Methods: Fifteen head and neck cancer patients previously treated with PBS proton therapy at high risk of nervous tissue toxicity were retrospectively analyzed. Three plans were developed for each patient: PBS, dynamic arc, and PBS with LET optimization. RBE-weighted dose distributions were calculated and compared for all patient plans using a linear LET-weighted model and a tissue-specific α/β-dependent model. LET-dose (LET_d) constraints were systematically tested to determine optimal values for plan quality and efficacy in altering LET spatial distribution in regions of concern. LET-dependent RBE enhancement was calculated for the three different planning methods. Results: Dynamic arc plans increased RBE enhancement when compared to PBS, while LET optimization for PBS consistently reduced RBE-enhanced dose to nervous tissue compared to non-optimized plans for both RBE models. Patient-specific variability in optimization benefit was observed, with the most significant improvements in cases with greater initial RBE enhancement. A maximum LET_d constraint of 2.5 µm/keV above 80% of the maximum structure dose threshold was found to balance plan quality and RBE mitigation. Conclusions: Dynamic arc delivery increased RBE enhancement relative to static PBS. LET optimization successfully modified LET_d spatial distributions to minimize RBE enhancement to nervous tissue structures when compared to non-LET optimized PBS and dynamic arc plans. Patient-specific risk stratification should be used when clinically deploying LET optimization. Full article

Background: skull base chordoma (Ch) and chondrosarcoma (ChSa) are rare neoplasms prone to local relapse. Alongside surgery, proton therapy (PT) is a well-established treatment for them. Given the relatively long patient survival expectancy, post-treatment quality of life (QoL) is crucial. This study prospectively assessed long-term QoL in this collective. Methods: seventy-seven adult patients (median age, 50 years; male n = 31; 40.3%) with skull base Ch/ChSa completed at least two EORTC-QLQ-C30 and BN20 questionnaires during and after PT. Oncological outcomes and therapy-related toxicities were recorded during follow-up. QoL was analyzed, with post-treatment scores compared to each patient’s baseline and correlated to oncological outcomes. Results: median follow-up was 51 months (range, 1–94), with 5-year overall survival (5yOS) and local control (5yLC) rates of 88.8% and 82.8%, respectively. The time to local or distant failure ranged from 8 to 58 (median, 22) months. QoL deteriorated directly at completion of PT and two to three years thereafter, especially in patients with local or distant failure. From the fifth year onward, QoL improved again. Complete resection before PT correlated to better QoL at all time points. Disease progression was associated with overall worse QoL, higher neurological symptoms already before PT, and higher symptom burden one year thereafter. Males reported better QoL before and one year after PT than females. Conclusions: PT achieves excellent OS and LC in patients with skull base Ch/ChSa. QoL declines directly after PT but remains close to reference population values. From the fifth year onward, QoL improves again. Gender, resection status, and disease progression significantly affect QoL in these patients. Full article

Background: RMS is the most common soft tissue sarcoma in children. Pencil beam scanning proton therapy (PBS PT) enables highly conformal dose delivery with reduced exposure to surrounding healthy structures, making it particularly suited for RMS in critical anatomical regions. Long-term clinical outcome data for this new radiation technique are scarce. Purpose: This study reports long-term outcomes and quality of life after PBS PT in children and adolescents with rhabdomyosarcoma (RMS). Methods and Materials: We retrospectively reviewed 114 children and adolescents with RMS (mostly embryonal, n = 100; 87.7%) treated between 2000 and 2020. Their median age was 4.6 years (range, 0.3–18). All received systemic chemotherapy according to prospective protocols. The median total PT dose delivered was 52 Gy (RBE; range, 41.4–64.8). Results: After a median follow-up period of 7.1 years (range, 0.3 to 17 years), we observed 26 failures overall; 21 (80.8%) occurred in-field. The 5-year local control and overall survival were 81.2% and 81%, respectively. The composite endpoint (non-ocular grade ≥3 toxicity- and failure-free survival) counting the first occurrence of any failure (local or distant), death, or non-ocular CTCAE v5.0 grade ≥3 toxicity was 77.3% at 5 years. At the start of PT, parents and children reported a quality of life significantly worse than that of a German normative group, but during the follow-up period, their scores improved to normal values in nearly all domains within two years. Conclusions: Our two decades of experience with PBS PT provide data that reflect good local control rates and minimal late non-ocular grade 3 toxicity. We also show that quality of life returned to normal scores in nearly all domains within 2 years. Children and adolescents with RMS seem to benefit from PBS PT in terms of toxicity and quality of life, but further prospective, multi-institutional comparative trials are needed. Full article

In view of the great need for quality assurance in radiotherapy, this paper proposes a stitching-based detector (SBD) technique and a set of intelligent algorithms that can reconstruct the information of projected particle beams. The reconstructed information includes the intensity, sigma value, and location of the maximum intensity of the beam under test. To verify the effectiveness of the proposed technique and algorithms, this research study adopts the pencil beam scanning (PBS) form of proton beam therapy (PBT) as an example. Through the SBD technique, it is possible to utilize 128 × 128 ionization chambers, which constitute an ionization plate of 25.6 cm², with an acceptable number of 4096 analog-to-digital converters (ADCs) and a resolution of 0.25 mm. Through simulation, the proposed SBD technique and intelligent algorithms are proven to exhibit satisfactory and practical performance. By using two kinds of maximum intensity definitions, sigma values ranging from 10 to 120, and two definitions in an erroneous case, the maximum error rate is found to be 3.95%, which is satisfactorily low. Through analysis, this research study discovers that most errors occur near the symmetrical and peripheral boundaries. Furthermore, lower sigma values tend to aggravate the error rate because the beam becomes more like an ideal particle, which leads to greater imprecision caused by symmetrical sensor structures as its sigma is reduced. However, because proton beams are normally not projected onto the border region of the sensed area, the error rate in practice can be expected to be even lower. Although this research study adopts PBS PBT as an example, the proposed SBD technique and intelligent algorithms are applicable to any type of particle beam reconstruction in the field of radiotherapy, as long as the particles under analysis follow a Gaussian distribution. Full article

Proton beam therapy for head and neck cancers traditionally employs a fixed relative biological effectiveness (RBE) of 1.1, which may underestimate actual biological effects in critical structures. This study evaluates how Linear Energy Transfer (LET) optimization could potentially prevent radiation-induced brachial plexopathy (RIBP). (1) Case presentation: A 65-year-old male with stage IVA p16-positive oropharyngeal squamous cell carcinoma received pencil-beam-scanning intensity-modulated proton therapy with concurrent cisplatin. Due to a right level 4 neck node, the high-risk target volume overlapped with the brachial plexus, resulting in a D0.1cc of 70.3 Gy (RBE = 1.1). Four years post-treatment, the patient developed progressive right upper extremity paresthesia, weakness, and dysesthesia. Electromyography revealed myokymia consistent with brachial plexopathy, while MRI showed hyperintensity of the right brachial plexus corresponding to the radiation field. Conservative treatment with pentoxifylline, gabapentin, and physical therapy improved his symptoms. (2) Methods: The original treatment plan was retrospectively analyzed using Monte Carlo dose algorithms and LET-dependent RBE models from McMahon and McNamara. An LET-optimized plan was created to limit LET_d to 2.0 keV/µm in the brachial plexus. (3) Results: The relative biological equivalent (RBE) dose to 0.1cc of the brachial plexus was 77.8 Gy (CGE RBE), exceeding tolerance. The LET-optimized plan reduced the brachial plexus D0.1cc to 59.4 Gy (RBE = 1.1) and 63.2 Gy (CGE RBE), an 18.8% decrease, while maintaining target coverage. LET_d, within the brachial plexus enhancement, decreased from 5.3 to 2.6 keV/μm. (4) Conclusion: This case highlights the potential clinical importance of LET optimization in proton therapy planning, particularly when organs-at-risk overlap with target volumes. By reducing LET_d from 5.3 to 2.6 keV/μm and biological equivalent dose by 18.8%, LET optimization could potentially prevent late toxicities, like RIBP, while maintaining target coverage. Full article

In this paper, we present an array-fed Fabry–Perot cavity antenna (FPCA) based on a partially reflecting sheet (PRS) capable of generating a circularly polarized (CP), highly directive, far-field radiation pattern in the 27–28.5 GHz frequency range. The PRS, the cavity, and the array of feeders serve to different purposes in this original structure. The PRS is engineered to produce a circular polarization from a linearly polarized source placed inside the cavity. The cavity is optimized to obtain a directive conical beam from the dipole-like pattern of the simple source, and allows for a frequency scan of the beam along the elevation plane. The array of feeders is designed to obtain a pencil beam whose azimuthal pointing direction can be controlled by properly phasing the sources. The radiation performance is studied with a specific application of the reciprocity theorem in a full-wave solver along with the pattern multiplication principle. A number of array-pattern configurations in terms of operation frequency and phase shift are investigated and presented to show the potential of the proposed solution in terms of design flexibility and radiation performance. Full article

Applying a proton beam in radiotherapy enables precise irradiation of the tumor volume, but only for continuous assessment of changes in patient anatomy. Proton beam range uncertainties in the treatment process may originate not only from physical beam properties but also from patient-specific factors such as tumor shrinkage, edema formation and sinus filling, which are not incorporated in tumor volume safety margins. In this paper, we evaluated variations in dose distribution in proton therapy resulting from the differences observed in the control tomographic images and the dosimetric influence of applied adaptive treatment. The data from weekly computed tomography (CT) control scans of 21 patients, which serve as the basis for adaptive radiotherapy, were used for this study. Dosimetric analysis of adaptive proton therapy (APT) was performed on patients with head and neck (H&N) area tumors who were divided into two groups: patients with tumors in the sinus/nasal area and patients with tumors in the brain area. For this analysis, the reference treatment plans were forward-calculated using weekly control CT scans. A comparative evaluation of organ at risk (OAR) dose-volume histogram (DVH) parameters, as well as conformity and homogeneity indices, was conducted between the initial and recalculated dose distributions to assess the necessity of the adaptation process in terms of dosimetric parameters. Changes in PTV volume after replanning were observed in seventeen patient cases, showing a discrepancy of over 1 ${\mathrm{cm}}^3$ in ten cases. In these cases, tumor progression occurred in 30% of patients, while regression was observed in 70%. The statistical analysis indicates that the use of the adaptive planning procedure results in a statistically significant improvement in dose distribution, particularly in the PTV area. The findings led to the conclusion that the adaptive procedure provides significant advantages in terms of dose distribution within the treated volume. However, when considering the entire patient group, APT did not result in a statistically significant dose reduction in OARs ($\alpha$ = 0.05). Full article

Because proton beam therapy (PBT) can lower the dose of radiation to the heart, lungs, and breast, it is an established radiation modality for patients with Hodgkin lymphoma (HL). Pencil beam scanning (PBS) PBT facilitates the treatment of more extensive targets. This may be especially of value for lymphoma patients who require RT to both mediastinal and axillary targets, defined here as extended target RT (ETRT), given the target distribution and need to minimize the lung, heart, and breast dose. Using the Proton Collaborative Group registry, we identified patients with HL treated with PBT to both their mediastinum and axilla, for which DICOM-RT was available. All patients were treated with PBS. To evaluate the dosimetric impact of PBS, we compared delivered PBS plans with VMAT butterfly photon plans optimized to have the same target volume coverage, when feasible. Between 2016 and 2021, twelve patients (median 26 years) received PBS ETRT (median 30.6 Gy (RBE)). Despite the large superior/inferior (SI, median 22.2 cm) and left/right (LR, median 22.8 cm) extent of the ETRT targets, all patients were treated with one isocenter except for two patients (both with SI and LR > 30 cm). Most commonly, anterior beams, with or without posterior beams, were used. Compared to photons, PBS had greater target coverage, better conformity, and lower dose heterogeneity while achieving lower doses to the lungs and heart, but not to the breast. No acute grade 3+ toxicities were reported, including pneumonitis. Proton ETRT in this small cohort was safely delivered with PBS and was associated with an improved sparing of the heart and lungs compared to VMAT. Full article

The antenna field of view, the angle range that can be accessed by scanning the main beam of a phased array, is one of the key performance prescriptions especially for space-borne aerials. The classical example of the full Earth, continental and subcontinental field of view of the geosynchronous satellite is indicative, and it extends to the medium and lower orbit multibeam telecommunication systems. There, a high-gain, very small beamwidth pencil beam should scan a given service area. At the same time, it should exhibit extremely low sidelobes in order not to present interference to adjacent geographical areas, served by neighboring beams, and keep its grating lobes out of the Earth’s surface. High-throughput telecommunication satellites should comply with those prescriptions to be given permission for placement in orbit. Thus, the motivation for delivering solid methods for the design of limited-field-of-view array antennas is high. A proposal in this direction is presented in the work at hand. Indeed, in the present study a scaling transformation is used to map a wide-angle scanning array to a limited-field-of-view one. We start the design from a Full-Field-of-View array with the appropriate half-power beamwidth, sidelobe level, and directivity index, and then we enlarge it to attain the desired one with the limited-field-of-view pattern characteristics. The potential of the method is solid since it augments the limited-field-of-view design methods using the excellent performance of the respective full-field-of-view ones. As a result, the synthesis of a limited-field-of-view array can use any of the well-known array synthesis methods in conjunction with the right scaling. Additionally, one can employ design methods that rely on sampling of planar aperture distributions. Various design examples, employing both sampling of continuous apertures and utilizing classical full-field-of-view array synthesis methods, are included and presented in detail, verifying the merit of our approach. Full article

Background and purpose: Proton therapy has been shown to provide dosimetric benefits in comparison with IMRT when treating prostate cancer with whole pelvis radiation; however, the optimal proton beam arrangement has yet to be established. The aim of this study was to evaluate three different intensity-modulated proton therapy (IMPT) beam arrangements when treating the prostate bed and pelvis in the postoperative setting. Materials and Methods: Twenty-three post-prostatectomy patients were planned using three different beam arrangements: two-field (IMPT₂B) (opposed laterals), three-field (IMPT₃B) (opposed laterals inferiorly matched to a posterior–anterior beam superiorly), and four-field (IMPT₄B) (opposed laterals inferiorly matched to two posterior oblique beams superiorly) arrangements. The prescription was 50 Gy radiobiological equivalent (GyE) to the pelvis and 70 GyE to the prostate bed. Comparisons were made using paired two-sided Wilcoxon signed-rank tests. Results: CTV coverages were met for all IMPT plans, with 99% of CTVs receiving ≥ 100% of prescription doses. All organ at risk (OAR) objectives were met with IMPT₃B and IMPT₄B plans, while several rectum objectives were exceeded by IMPT₂B plans. IMPT₄B provided the lowest doses to OARs for the majority of analyzed outcomes, with significantly lower doses than IMPT₂B +/− IMPT₃B for bladder V30–V50 and mean dose; bowel V15–V45 and mean dose; sigmoid maximum dose; rectum V40–V72.1, maximum dose, and mean dose; femoral head V37–40 and maximum dose; bone V40 and mean dose; penile bulb mean dose; and skin maximum dose. Conclusion: This study is the first to compare proton beam arrangements when treating the prostate bed and pelvis. four-field plans provided better sparing of the bladder, bowel, and rectum than 2- and three-field plans. The data presented herein may help inform the future delivery of whole pelvis IMPT for prostate cancer. Full article

Scatterometers are highlighted in polar applications, such as sea ice extent retrieval. There are currently three types of spaceborne scatterometer in operation, among which the rotating pencil beam scatterometer and the rotating fan beam scatterometer have similar rotating observation geometry, but different beam sampling. However, it is difficult to objectively evaluate the performance of the two rotating beam scatterometers using the obtained data. This is because there are significant differences in their system parameters, which in turn affects the objectivity of the evaluation. Considering the high flexibility of the rotating fan beam scatterometer, this study proposes a dual-mode sea ice extent retrieval method for the rotating fan beam scatterometer. The dual modes refer to the rotating fan beam mode (or full incidence mode) and the equivalent rotating pencil beam mode (or single incidence mode). The two modes share the same system and spatiotemporal synchronous backscatter measurements provide the possibility of objectively comparing the rotating pencil beam and rotating fan beam scatterometers. The comparison, validation, and evaluation of the dual-mode sea ice extent of China France Oceanography Satellite Scatterometer (CSCAT) were performed. The results indicate that the sea ice extent retrieval of the equivalent rotating pencil beam mode of the rotating fan beam scatterometer is realizable, and compared to the existing rotating pencil beam scatterometers (such as the OceanSat Scatterometer on ScatSat-1, OSCAT, on ScatSat-1, and the Hai Yang 2B Scatterometer, HSCAT-B), the derived sea ice extent is closer to that of Advanced Microwave Scanning Radiometer 2 (AMSR2). For the two modes of CSCAT, when compared to AMSR2, the sea ice extent of the CSCAT full incidence mode has smaller values of root mean squared error (RMSE), error-of-ice (EI), and ice edge location distance (LD) than those of the CSCAT single incidence mode. These suggest that the rotating fan beam scatterometer shows better observation abilities for sea ice extent than the rotating pencil beam scatterometers. Full article