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Medical Physics Jun 2024Intensity Modulated Proton Therapy (IMPT) is a sophisticated radiation treatment allowing for precise dose distributions. However, conventional spot selection strategies...
BACKGROUND
Intensity Modulated Proton Therapy (IMPT) is a sophisticated radiation treatment allowing for precise dose distributions. However, conventional spot selection strategies in IMPT face challenges, particularly with minimum monitor unit (MU) constraints, affecting planning quality and efficiency.
PURPOSE
This study introduces an innovative Two-Stage Mixed Integer Linear Programming (MILP) method to optimize spot intensity in IMPT with Lower Bound (LB) constraints. This method seeks to improve treatment planning efficiency and precision, overcoming limitations of existing strategies.
METHODS
Our approach evaluates prevalent IMPT spot selection strategies, identifying their limitations, especially concerning MU constraints. We integrated LB constraints into a MILP framework, using a novel three-phase strategy for spot pool selection, to enhance performance over traditional heuristic methods and L1 + L∞ strategies. The method's efficacy was tested in eight study cases, using Dose-Volume Histograms (DVHs), spot selection efficiency, and computation time analysis for benchmarking against established methods.
RESULTS
The proposed method showed superior performance in DVH quality, adhering to LB constraints while maintaining high-quality treatment plans. It outperformed existing techniques in spot selection, reducing unnecessary spots and balancing precision with efficiency. Cases studies confirmed the method's effectiveness in producing clinically feasible plans with enhanced dose distributions and reduced hotspots, especially in cases with elevated LB constraints.
CONCLUSIONS
Our Two-Stage MILP strategy signifies a significant advancement in IMPT treatment planning. By incorporating LB constraints directly into the optimization process, it achieves superior plan quality and deliverability compared to current methods. This approach is particularly advantageous in clinical settings requiring minimum spot number and high MU LB constraints, offering the potential for improved patient outcomes through more precise and efficient radiation therapy plans.
PubMed: 38922975
DOI: 10.1002/mp.17265 -
Medical Physics Jun 2024Cone-beam CT (CBCT) is the most commonly used onboard imaging technique for target localization in radiation therapy. Conventional 3D CBCT acquires x-ray cone-beam... (Review)
Review
Cone-beam CT (CBCT) is the most commonly used onboard imaging technique for target localization in radiation therapy. Conventional 3D CBCT acquires x-ray cone-beam projections at multiple angles around the patient to reconstruct 3D images of the patient in the treatment room. However, despite its wide usage, 3D CBCT is limited in imaging disease sites affected by respiratory motions or other dynamic changes within the body, as it lacks time-resolved information. To overcome this limitation, 4D-CBCT was developed to incorporate a time dimension in the imaging to account for the patient's motion during the acquisitions. For example, respiration-correlated 4D-CBCT divides the breathing cycles into different phase bins and reconstructs 3D images for each phase bin, ultimately generating a complete set of 4D images. 4D-CBCT is valuable for localizing tumors in the thoracic and abdominal regions where the localization accuracy is affected by respiratory motions. This is especially important for hypofractionated stereotactic body radiation therapy (SBRT), which delivers much higher fractional doses in fewer fractions than conventional fractionated treatments. Nonetheless, 4D-CBCT does face certain limitations, including long scanning times, high imaging doses, and compromised image quality due to the necessity of acquiring sufficient x-ray projections for each respiratory phase. In order to address these challenges, numerous methods have been developed to achieve fast, low-dose, and high-quality 4D-CBCT. This paper aims to review the technical developments surrounding 4D-CBCT comprehensively. It will explore conventional algorithms and recent deep learning-based approaches, delving into their capabilities and limitations. Additionally, the paper will discuss the potential clinical applications of 4D-CBCT and outline a future roadmap, highlighting areas for further research and development. Through this exploration, the readers will better understand 4D-CBCT's capabilities and potential to enhance radiation therapy.
PubMed: 38922912
DOI: 10.1002/mp.17269 -
Medical Physics Jun 2024The advantages of proton therapy can be further enhanced with online magnetic resonance imaging (MRI) guidance. One of the challenges in the realization of MRI-guided...
BACKGROUND
The advantages of proton therapy can be further enhanced with online magnetic resonance imaging (MRI) guidance. One of the challenges in the realization of MRI-guided proton therapy (MRPT) is accurately calculating the radiation dose in the presence of magnetic fields.
PURPOSE
This study aims to develop an efficient and accurate proton dose calculation algorithm adapted to the presence of magnetic fields.
METHODS
An analytical-numerical radiation dose calculation algorithm, Proton and Ion Dose Engine (PRIDE), was developed. The algorithm combines the pencil beam algorithm (PBA) with a novel iterative voxel-based ray-tracing algorithm. The new ray-tracing method uses fewer assumptions and ensures broader applicability for proton beam trajectory prediction in magnetic fields, and has been compared to Wolf's method and Schellhammer's method. The accuracy of PRIDE algorithm was validated on three phantoms and two practical plans (one single-field water plan and one prostate tumor plan) in different magnetic field strengths up to 3.0 T. The validation was performed by comparing the results against the Monte Carlo (MC) simulations, using the global gamma index criteria of 2%/2 mm and 3%/3 mm with a 10% threshold.
RESULTS
PRIDE showed good agreement with MC in homogeneous and slab heterogeneous phantom, achieving gamma passing rates (%GPs) above 99% for 2%/2 mm criteria when magnetic field strength is not greater than 1.5 T. Although the agreement decreased for scenarios involving high proton energy (240 MeV) and strong magnetic field (3.0 T), the 2%/2 mm %GPs still remained above 98%. In lateral heterogeneous phantom, the accuracy of PRIDE decreased due to the PBA's limitation. For the two practical plans in different magnetic fields, %GPs exceeded 98% and 99% for 2%/2 mm and 3%/3 mm criteria, respectively.
CONCLUSIONS
PRIDE can perform efficient and accurate proton dose calculation in magnetic fields up to 3.0 T, and is expected to work as a useful tool for proton dose calculation in MRPT.
PubMed: 38922910
DOI: 10.1002/mp.17262 -
Journal of Applied Clinical Medical... Jun 2024A higher minimum monitor unit (minMU) for pencil-beam scanning proton beams in intensity-modulated proton therapy is preferred for more efficient delivery. However, plan...
PURPOSE
A higher minimum monitor unit (minMU) for pencil-beam scanning proton beams in intensity-modulated proton therapy is preferred for more efficient delivery. However, plan quality may be compromised when the minMU is too large. This study aimed to identify the optimal minMU (OminMU) to improve plan delivery efficiency while maintaining high plan quality.
METHODS
We utilized clinical plans including six anatomic sites (brain, head and neck, breast, lung, abdomen, and prostate) from 23 patients previously treated with the Varian ProBeam system. The minMU of each plan was increased from the current clinical minMU of 1.1 to 3-24 MU depending on the daily prescribed dose (DPD). The dosimetric parameters of the plans were evaluated for consistency against a 1.1-minMU plan for target coverage as well as organs-at-risk dose sparing. DPD/minMU was defined as the ratio of DPD to minMU (cGy/MU) to find the OminMU by ensuring that dosimetric parameters did not differ by >1% compared to those of the 1.1-minMU plan.
RESULTS
All plans up to 5 minMU showed no significant dose differences compared to the 1.1-minMU plan. Plan qualities remained acceptable when DPD/minMU ≥35 cGy/MU. This suggests that the 35 cGy/MU criterion can be used as the OminMU, which implies that 5 MU is the OminMU for a conventional fraction dose of 180 cGy. Treatment times were decreased by an average of 32% (max 56%, min 7%) and by an average of 1.6 min when the minMU was increased from 1.1 to OminMU.
CONCLUSION
A clinical guideline for OminMU has been established. The minMU can be increased by 1 MU for every 35 cGy of DPD without compromising plan quality for most cases analyzed in this study. Significant treatment time reduction of up to 56% was observed when the suggested OminMU is used.
PubMed: 38922754
DOI: 10.1002/acm2.14435 -
Physical and Engineering Sciences in... Jun 2024Particle (proton, carbon ion, or others) radiotherapy for ocular tumors is highly dependent on precise dose distribution, and any misalignment can result in severe...
Particle (proton, carbon ion, or others) radiotherapy for ocular tumors is highly dependent on precise dose distribution, and any misalignment can result in severe complications. The proposed eye positioning and tracking system (EPTS) was designed to non-invasively position eyeballs and is reproducible enough to ensure accurate dose distribution by guiding gaze direction and tracking eye motion. Eye positioning was performed by guiding the gaze direction with separately controlled light sources. Eye tracking was performed by a robotic arm with cameras and a mirror. The cameras attached to its end received images through mirror reflection. To maintain a light weight, certain materials, such as carbon fiber, were utilized where possible. The robotic arm was controlled by a robot operating system. The robotic arm, turntables, and light source were actively and remotely controlled in real time. The videos captured by the cameras could be annotated, saved, and loaded into software. The available range of gaze guidance is 360° (azimuth). Weighing a total of 18.55 kg, the EPTS could be installed or uninstalled in 10 s. The structure, motion, and electromagnetic compatibility were verified via experiments. The EPTS shows some potential due to its non-invasive wide-range flexible eye positioning and tracking, light weight, non-collision with other equipment, and compatibility with CT imaging and dose delivery. The EPTS can also be remotely controlled in real time and offers sufficient reproducibility. This system is expected to have a positive impact on ocular particle radiotherapy.
PubMed: 38922382
DOI: 10.1007/s13246-024-01453-6 -
Cells Jun 2024The use of charged particle radiotherapy is currently increasing, but combination therapy with DNA repair inhibitors remains to be exploited in the clinic. The... (Review)
Review
The use of charged particle radiotherapy is currently increasing, but combination therapy with DNA repair inhibitors remains to be exploited in the clinic. The high-linear energy transfer (LET) radiation delivered by charged particles causes clustered DNA damage, which is particularly effective in destroying cancer cells. Whether the DNA damage response to this type of damage is different from that elicited in response to low-LET radiation, and if and how it can be targeted to increase treatment efficacy, is not fully understood. Although several preclinical studies have reported radiosensitizing effects when proton or carbon ion irradiation is combined with inhibitors of, e.g., PARP, ATR, ATM, or DNA-PKcs, further exploration is required to determine the most effective treatments. Here, we examine what is known about repair pathway choice in response to high- versus low-LET irradiation, and we discuss the effects of inhibitors of these pathways when combined with protons and carbon ions. Additionally, we explore the potential effects of DNA repair inhibitors on antitumor immune signaling upon proton and carbon ion irradiation. Due to the reduced effect on healthy tissue and better immune preservation, particle therapy may be particularly well suited for combination with DNA repair inhibitors.
Topics: Humans; DNA Repair; DNA Damage; Proton Therapy; Heavy Ion Radiotherapy; Neoplasms; Animals; Linear Energy Transfer
PubMed: 38920686
DOI: 10.3390/cells13121058 -
DEN Open Apr 2025Gastric mucosal changes associated with long-term potassium-competitive acid blocker and proton pump inhibitor (PPI) therapy may raise concern. In contrast to that for... (Review)
Review
Gastric mucosal changes associated with long-term potassium-competitive acid blocker and proton pump inhibitor (PPI) therapy may raise concern. In contrast to that for PPIs, the evidence concerning the safety of long-term potassium-competitive acid blocker use is scant. Vonoprazan (VPZ) is a representative potassium-competitive acid blocker released in Japan in 2015. In order to shed some comparative light regarding the outcomes of gastric mucosal lesions associated with a long-term acid blockade, we have reviewed six representative gastric mucosal lesions: fundic gland polyps, gastric hyperplastic polyps, multiple white and flat elevated lesions, cobblestone-like gastric mucosal changes, gastric black spots, and stardust gastric mucosal changes. For these mucosal lesions, we have evaluated the association with the type of acid blockade, patient gender, infection status, the degree of gastric atrophy, and serum gastrin levels. There is no concrete evidence to support a significant relationship between VPZ/PPI use and the development of neuroendocrine tumors. Current data also shows that the risk of gastric mucosal changes is similar for long-term VPZ and PPI use. Serum hypergastrinemia is not correlated with the development of some gastric mucosal lesions. Therefore, serum gastrin level is unhelpful for risk estimation and for decision-making relating to the cessation of these drugs in routine clinical practice. Given the confounding potential neoplastic risk relating to infection, this should be eradicated before VPZ/PPI therapy is commenced. The evidence to date does not support the cessation of clinically appropriate VPZ/PPI therapy solely because of the presence of these associated gastric mucosal lesions.
PubMed: 38919514
DOI: 10.1002/deo2.400 -
Cureus May 2024This study aims to summarize sacrococcygeal chordoma literature through bibliometric analysis and to offer insights into key studies to guide clinical practices and... (Review)
Review
This study aims to summarize sacrococcygeal chordoma literature through bibliometric analysis and to offer insights into key studies to guide clinical practices and future research. The Web of Science database was searched using the terms "sacral chordoma", "chordomas of the sacrum", "chordomas of the sacral spine", "chordomas of the sacrococcygeal region", "coccygeal chordoma", and "coccyx chordoma". Articles were analyzed for citation count, authorship, publication date, journal, research area tags, impact factor, and evidence level. The median number of citations was 75 (range: 53-306). The primary publication venue was the International Journal of Radiation Oncology, Biology, Physics. Most works, published between 1999 and 2019, featured a median journal impact factor of 3.8 (range: 2.1-7) and predominantly fell under the research area tag, radiation, nuclear medicine, and imaging. Of these articles, 19 provided clinical data with predominantly level III evidence, and one was a literature review. This review highlights the increasing volume of sacrococcygeal chordoma publications over the past two decades, indicating evolving treatment methods and interdisciplinary patient care. Advances in radiation, particularly intensity-modulated radiation therapy (IMRT) and proton beam therapy, are believed to be propelling research growth, and the lack of level I evidence underscores the need for more rigorous studies to refine treatment protocols for sacrococcygeal chordomas.
PubMed: 38919226
DOI: 10.7759/cureus.61119 -
Arthritis Research & Therapy Jun 2024To determine the relationship between gastroesophageal reflux disease (GORD) and its treatment and interstitial lung disease in patients with systemic sclerosis (SSc).
BACKGROUND
To determine the relationship between gastroesophageal reflux disease (GORD) and its treatment and interstitial lung disease in patients with systemic sclerosis (SSc).
METHODS
SSc patients from the Australian Scleroderma Cohort Study (ASCS) were included. GORD was defined as self-reported GORD symptoms, therapy with a proton pump inhibitor (PPI) or histamine 2 receptor antagonist (H2RA) and/or the presence of reflux oesophagitis diagnosed endoscopically. The impact of GORD and its treatment on ILD features (including severity and time to ILD development) and survival was evaluated.
RESULTS
GORD was a common manifestation affecting 1539/1632 (94%) of SSc patients. GORD affected 450/469 (96%) of those with SSc-ILD cohort. In SSc-ILD, there was no relationship between the presence of GORD or its treatment and time to ILD development or ILD severity. However, GORD treatment was associated with improved survival in those with ILD (p = 0.002). Combination therapy with both a PPI and a H2RA was associated with a greater survival benefit than single agent therapy with PPI alone (HR 0.3 vs 0.5 p < 0.050 respectively).
CONCLUSION
GORD is a common SSc disease manifestation. While the presence or treatment of GORD does not influence the development or severity of ILD, aggressive GORD treatment, in particular with a combination of PPI and H2RA, is associated with improved survival in those with SSc-ILD.
Topics: Humans; Gastroesophageal Reflux; Lung Diseases, Interstitial; Female; Male; Middle Aged; Scleroderma, Systemic; Proton Pump Inhibitors; Aged; Histamine H2 Antagonists; Adult; Cohort Studies; Treatment Outcome; Australia
PubMed: 38918847
DOI: 10.1186/s13075-024-03355-0 -
Scientific Reports Jun 2024
PubMed: 38918458
DOI: 10.1038/s41598-024-65365-x