Physica Medica-European Journal of Medical Physics最新文献

Purpose: Material decomposition induces substantial noise in basis images and their synthesized computed tomography (CT) images. A likelihood-based bilateral filter was previously developed as a neighborhood filter that effectively reduces noise. However, this method is sensitive to image contrast, and the noise texture needs improvement. It is also necessary to address how to optimally combine filtered basis images to synthesize CT images. This study addressed these issues by introducing total likelihood and a noise-matched condition.

Methods: The experimental feasibility of the proposed method was demonstrated in a benchtop photon-counting CT (PCCT) system using the following steps: (1) A calibration process for forward modeling, (2) maximum likelihood (ML)-based material decomposition, which is accurate but suffers from substantial noise, (3) noise reduction by applying a total-likelihood-based filter, and (4) CT image synthesis using the noise-matched condition. The proposed method was compared with conventional neighborhood filters and statistical iterative reconstruction with edge-preserving regularization.

Results: The local noise and task-based modulation transfer function (TTF) were analyzed using a test phantom, and the proposed method was found to preserve the spatial resolution better than the other methods, especially in low-contrast regions. In the chicken leg experiment, the proposed method improved the fine structures and background textures in the denoised images and exhibited superior properties in analyzing the noise power spectrum.

Conclusion: The proposed method is effective and computationally efficient for noise reduction in PCCT and can potentially replace conventional iterative edge-preserved regularization approaches.

Purpose: Automatic planning (AP) has been compared to manual planning (MP) in lung stereotactic body radiation therapy (SBRT) to validate the former and to implement it in clinical practice.

Methods: A new developing Guided Planning System (GPS) engine was used to reoptimize 20 lung SBRT plans with the RayStation™ treatment planning system (TPS). The original manual plans were optimized to deliver 60 Gy in 5 or 8 fractions to the target with constraints on organs at risk (OARs) based on an internal protocol. AP plans were compared to MP based on (i) planning target volume (PTV) and OARs dosimetric evaluation, (ii) clinician's blind plan comparison, (iii) Plan QA results, and (iv) plan quality metrics. Differences between continuous variables were explored through the Mann-Whitney test (p < 0.05).

Results: Target and OARs dosimetry showed no significant difference, with the only exception of the spinal cord maximum dose that was significantly lower for AP in the 5 fractions scheme (MP: 8.93 Gy ± 3.94 Gy vs AP: 6.45 Gy ± 2.72 Gy, p = 0.034). In the blind comparison, AP was preferred in 45 % of cases while MP in 35 % of cases (no preference was expressed in 20 % of cases). A trend towards lower monitor units (MUs) was found for AP in the 5 fractions scheme (MP: 3383 ± 943 vs AP: 2662 ± 588, p = 0.059). No significant difference was found in any of the plan quality metrics.

Conclusions: AP plans were not inferior to MP plans; therefore, GPS is ready for clinical use in a pulmonary SBRT setting, reducing the planning workload and harmonizing the planning procedure.

Purpose: To train and validate KB prediction models by merging a large multi-institutional cohort of whole breast irradiation (WBI) plans using tangential fields.

Methods: Ten institutions (INST1-INST10, 1481 patients) developed their KB-institutional models for left/right WBI (ten models for right and eight models for left). The transferability of models among centers was assessed based on the overlap of the geometric Principal Component (PC1) of each model when applied to other institutions and/or on the presence of significantly different optimization policies. Centers corresponding to transferable models were asked to join the building of two KB-benchmark models for right/left breast. Dose-volume histogram (DVH) prediction bands (lung/heart) were compared against those of the KB-institutional models.

Results: All models were transferable except INST6 (right breast) and INST1 (left breast). Planning data from 6 institutions for right breast and 5 institutions for left breast (out of 9 and 7 institutions with transferable models, respectively) were combined, totaling data from 850 patients. Prediction bands on the test cohorts (n = 30/25 right/left) showed a large overlap with bands of each institution model: for the right-breast, the KB-benchmark model predicts slightly lower lung D_mean when compared to KB-institution models, except for INST7. Regarding the left-breast, even greater similarity between KB-benchmark and KB-institution model predictions was found.

Conclusions: Multi-institutional KB-benchmark models for WBI were successfully generated. They may be employed by other users, representing the performances reached in a multi-institutional context of experienced centers. KB-benchmark models can also have significant applications for large-scale automatic plan optimization, QA/audit and tutoring/education purposes.

Objectives: To investigate the impact of compressed sensing - sensitivity encoding (CS-SENSE) acceleration factor on the diagnostic performance of magnetic resonance imaging (MRI) within standard female pelvis protocol in patients with endometrial cancer.

Methods: T2-weighted turbo spin echo (TSE) sequence from standard female pelvic MRI protocol was chosen due to its long acquisition time and essential role in the evaluation of morphological characteristics of the female pelvic anatomical structures. Fully sampled reference scans and multiple prospectively 2x to 5x under-sampled CS-SENSE scans were acquired. Retrospectively, under-sampled scans were compared to fully sampled scans and visually assessed for image quality and diagnostic quality by two independent radiologists dedicated to urogenital imaging with different experience levels.

Results: Images obtained with CS-SENSE accelerated acquisition were of diagnostically acceptable quality at up to 3x acceleration for T2 TSE in both axial and sagittal planes (with an acquisition time reduction of 64 %). Among all evaluated uterine structures, the junctional zone proved to be most sensitive to the influence of the acceleration factor. Statistical analysis showed statistically significant differences between image interpretation qualities between two radiologists of different experience levels (p < 0.05).

Conclusion: CS-SENSE accelerated T2 TSE sequence of the female pelvis shows image quality similar to that of conventional acquisitions with reduced acquisition time. CS-SENSE can moderately reduce scan time, providing many benefits without losing the image quality.

Purpose: Total marrow (lymph-node) irradiation (TMI/TMLI) is a radiotherapy technique irradiating the whole body of a patient. The limited couch travel range in modern linacs (130-150 cm) forces to split the TMI/TMLI delivery into two plans with opposite orientation. A dedicated field junction is necessary to achieve satisfactory target coverage in the overlapping region of the two plans. In a recent study, we implemented an automatic tool (AT) using the Eclipse Scripting API for the creation of a field junction and optimization of TMI/TMLI. In this work, we improved the AT by developing an automatic base-dose planning approach.

Methods: Ten patients were selected to compare the manual procedure, original automatic planning approach, and new base-dose approach. Treatment plans were evaluated with the D98%, D_mean, and D2% for the planning target volume at the junction (PTV_J), while D_mean and D2% were considered for the PTV without the junction (PTVNoJ) and healthy tissues.

Results: Base-dose planning significantly improved the PTV_J coverage compared with the manual approach, with unaltered D_mean, consistently lower D2% (2.24 Gy vs. 2.30 Gy) and higher D98% (1.98 Gy vs. 1.89 Gy). Moreover, it significantly reduced the hotspots in healthy tissues (2.02 Gy vs. 2.15 Gy). No significant differences for PTVNoJ dose statistics were observed among the procedures, demonstrating that the automatic approaches produced a target coverage similar to the one obtained manually.

Conclusions: Base-dose planning improved the field junction optimization of TMI/TMLI. Automatic planning tools can incrementally improve procedures that would be challenging or error-prone to achieve manually.

Purpose: This study aims to systematically evaluate all radionuclides used in knee RSV to date and identify the most suitable radionuclide for knee RSV.

Methods: To compare knee RSV with Y-90, P-32, Ho-166, Re-188, Au-198, Lu-177, Sm-153, and Re-186, we measured the radiation dose to non-target organs and the inducing of secondary malignancies in knee RSV patient, the radiation dose to family member and medical staff from the knee RSV patients, and the quality of post-treatment images.

Results: The Lifetime Attributable Risks of cancer incidence and mortality and the Relative Risks of solid cancer incidence and mortality are significantly higher for Y-90 and P-32 in both adult and pediatric patients compared to other radionuclides used in knee RSV. Knee RSV with Re-188, Ho-166, Au-198, and Sm-153 induces a negligible risk of secondary malignancies. The average absorbed dose for medical staff and family members exposed to patients treated with Y-90 is also significantly greater than for those exposed to RSV patients treated with other radionuclides. In contrast, the absorbed dose for medical staff and family members exposed to RSV patients treated with Sm-153, Ho-166, and Au-198 is negligible. Sm-153, Ho-166, and Re-188 offer high-quality images in post-RSV planar imaging.

Conclusion: Based on the findings of this study and the therapeutic range of the radionuclides, Re-188 has been identified as a suitable alternative to Y-90 for knee RSV in adults. At the same time, Sm-153 and Ho-166 have been recognized as the most appropriate radionuclides for pediatric knee RSV.

Purpose: Minibeam radiotherapy (MBRT) uses small parallel beams of radiation to create a highly modulated dose pattern. The aim of this study is to develop an optical radioluminescence imaging (RLI) approach to perform real-time dose measurement for MBRT.

Methods: MBRT was delivered using an image-guided small animal irradiator equipped with a custom collimator. Five slabs of plastic scintillators with a thicknesses of 0.5, 1, 2, 3 and 10 mm were placed on top of a mouse phantom, to localize and measure the delivered dose. A thin radioluminescence film (Gd₂O₂S:Tb) was used to obtain the mini beam dose profile that was compared against GafChromic (GC) films measurements. The RLI signal was detected with a CMOS camera placed at 90 deg with respect to the beam axis. Monte Carlo (MC) simulations were also performed using TOPAS for comparison with the experimental results.

Results: The measured peak to valley dose ratio (PVDR) obtained with RLI was 16.7 in line with GC films measurements. The differences between peak and valley dimension were less that 3% with respect to GC measurements. Using RLI performed with the scintillator slabs, it was possible to localize and measure in real-time MBRT delivery on the mouse phantom.

Conclusions: We proposed a novel method for MBRT dose localization and measurement in real-time based on RLI. The results we obtained are in good agreement with GC film measurements.

Purpose: Proton therapy of moving targets is considered a challenge. At Maastro, we started treating lung cancer patients with proton therapy in October 2019. In this work, we summarise the developed treatment strategies and gained clinical experience from a physics point of view.

Methods: We report on our clinical approaches to treat lung cancer patients with the Mevion Hyperscan S250i proton machine. We classify lung cancer patients as small movers (tumour movement ≤ 5 mm) or large movers (tumour movement > 5 mm). The preferred beam configuration has evolved over the years of clinical treatment, and currently mostly two or three beam directions are used. All patients are treated with robustly optimised plans (5 mm setup and 3% range uncertainty). Small movers are planned based on a clinical target volume (CTV) with a 3 mm isotropic margin expansion to account for motion, while large movers are planned based on an internal target volume (ITV). All patients are treated in free-breathing.

Results: Between October 2019 and December 2023, 379 lung cancer patients have been treated, of which 130 were large movers. The adaptation rate was 28%. The median treatment time has been reduced from 30 to 23 min. The mean dose to the heart, oesophagus, and lungs was on average 4.3, 15.4, and 11.0 Gy, respectively.

Conclusions: Several treatment planning and workflow improvements have been introduced over the years, resulting in an increase of treatment quality and number of treated patients, as well as reduction of planning and treatment time.

Purpose: To study the application of radiomics in cancer imaging with a focus on lung cancer, renal cell carcinoma, gastrointestinal cancer, and head and neck cancer.

Methods: Different electronic databases were considered. Articles published in the last five years were analyzed (January 2019 and December 2023). Papers were selected by two investigators with over 15 years of experience in Radiomics analysis in cancer imaging. The methodological quality of each radiomics study was performed using the Radiomic Quality Score (RQS) by two different readers in consensus and then by a third operator to solve disagreements between the two readers.

Results: 19 articles are included in the review. Among the analyzed studies, only one study achieved an RQS of 18 reporting multivariable analyzes with also non-radiomics features and using the validation phase considering two datasets from two distinct institutes and open science and data domain.

Conclusion: This informative review has brought attention to the increasingly consolidated potential of Radiomics, although there are still several aspects to be evaluated before the transition to routine clinical practice. There are several challenges to address, including the need for standardization at all stages of the workflow and the potential for cross-site validation using heterogeneous real-world datasets. It will be necessary to establish and promote an imaging data acquisition protocol, conduct multicenter prospective quality control studies, add scanner differences and vendor-dependent characteristics; to collect images of individuals at additional time points, to report calibration statistics.

Background: Working from home during the Covid-19 pandemic was perceived differently by men and women working in STEM fields. The aim of this paper is to highlight the unexpected benefits generated by working from home during the pandemic.

Methods: Qualitative methodology was used to analyze data, collected via survey. The survey designed and conducted by WiMPBME targeted both males and females working in medical-related STEM fields (physics and engineering) and was answered by 921 individuals from 76 countries across all continents. This report analysed the responses to one open-ended question of the survey, namely: "What is the one positive that you have learnt/experienced as a result of working from home during this pandemic?".

Results: 594 responded to the question of interest. Access to home office was reported by 72.2% of survey participants. Males were more likely than females to report no positives of working from home (62.9%). Females were more likely to cite quality time, physical and mental health as positive factors than males, and to mention children in their responses. The most commonly coded thematic unit for males was remote working, with many males reporting the feasibility of working from home. Increased work productivity, better time management and work organisation were other common themes highlighted by responders irrespective of gender.

Conclusion: The findings of the survey show the diversity of perceptions about remote working in STEM fields, while highlighting the importance of considering family dynamics, individual circumstances as well as gender when evaluating varied experiences of STEM professionals.