Journal of Medical Physics最新文献

Aim: This study aimed to clarify the relationship between the results of in vivo dosimetry (IVD) analysis and intrafractional set-up errors (SEs) to determine the criteria for detecting intra-fractional SEs of 3 mm.

Methods: Fifteen patients undergoing deep-inspiration breath-hold (DIBH) irradiation for left breast cancer were included in the study. The prescribed dose and fraction size were 50 Gy for six patients, and 42.56 Gy for nine patients. Visual coaching devices were used to improve the reproducibility of deep inspiration states. For IVD, integrated electronic portal imaging device (EPID) images were obtained using treatment beams. Intra-fractional SEs were detected, and gamma analysis was performed on these images. Receiver-operating characteristic curves were calculated to assess the accuracy of the detection of the intrafractional SEs for each criterion.

Results: The mean values for two-dimensional vectors, absolute Z-direction, and three dimensional (3D) vectors of intra-fractional SEs were 1.9 ± 1.5 mm, 1.8 ± 1.6 mm, and 2.9 ± 1.8 mm, respectively. The mean γ-pass rates in each criterion were 90.6% ± 10.4%, 89.6% ± 10.8%, 92.7% ± 9.7%, 94.8% ± 8.3%, and 94.4% ± 8.3% for 2% 3 mm, 3% 2 mm, 3% 3 mm, 3% 4 mm, and 4% 3 mm, respectively. The correlation coefficients between the SEs in the 3D vector and each γ value ranged from 0.6 to 0.8.

Conclusions: In IVD with EPIDs for DIBH irradiation, the optimal γ-analysis index for intrafractional SEs detection >3 mm is 3% 3 mm.

Propose: Medical image enhancement is one of the most critical areas in modern medicine, as it helps in disease diagnosis and medical action on the basis of diagnostic accuracy. This paper proposes a new hybrid model having new techniques of noise processing and contrast enhancement for medical images.

Materials and methods: An adaptive Wiener filter can be used to remove noise, the contrast-limited adaptive histogram equalization (CLAHE) algorithm can be used to enhance picture contrast, gamma transforms to correct for illumination, and wavelet transforms may also be employed as another means in order to amplify fine details. For this purpose, the method was first implemented on the retinal images. After that, the same method was long computed tomography (CT) images and finally magnetic resonance imaging (MRI) pictures. To reflect the fractal nature of medical images, 10 retinal images were taken; 10 CT pictures and 10 MRI scans, as a statistical sampling to provide more accurate weighing of the effectiveness in image processing technologies with respect to different medical imaging modalities.

Results: In extreme contrast conditions, by contrasting the results yielded by the proposed method with those of some existing methods, for example, conventional histogram equalization (HE) and CLAHE, considerable enhancement in the image quality could be obtained. The results indicated that our proposed approach outperforms the former approach by suppressing noise but preserving the microstructures of tissues or anatomical structures. It also improves the contrast evenly, providing increased sharpness of the images without loss of vital information and distortion.

Conclusions: This suggested technique equates the value priorities with additional harmonious; this suggests the image is shrewdly for medical purpose. In addition, this allows for translation and better ability to identify more subtlety and specificity tissue, the essence of any medical diagnosis.

Purpose: The purpose of the study was to evaluate longitudinal changes in health-related quality of life (HRQoL) among patients undergoing radiotherapy for solid tumors, using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) questionnaire and to identify symptom and function trajectories over time in relation to clinical and demographic parameters.

Materials and methods: In this prospective observational study, 211 adult patients with histologically confirmed solid malignancies (excluding breast cancer) were enrolled at a tertiary oncology center. HRQoL was assessed at four time points: Baseline (T1), end of radiotherapy (T2), 1-month post-treatment (T3), and 6 months' post-treatment (T4), using the validated EORTC QLQ-C30 tool. Statistical analysis included repeated measures analysis of variance and Bonferroni-adjusted post hoc tests.

Results: Global health status improved significantly from T1 (67.0) to T4 (76.0) (P < 0.001). Functional domains, physical, emotional, cognitive, and social functioning, also showed significant improvement (all P < 0.001), whereas role functioning improved modestly (P = 0.009). Symptom scores such as fatigue, pain, nausea/vomiting, and insomnia declined significantly (P < 0.001), whereas dyspnea showed no significant change (P = 0.573). Financial difficulties decreased over time (P < 0.001). Subgroup analyses revealed sex-based variations in symptom burden, with females reporting higher pain and financial strain early post-treatment, and males experiencing greater appetite loss and delayed economic burden.

Conclusion: This study represents preliminary 6-month follow-up data; ongoing surveillance will provide insights into late toxicity and long-term survivorship. Persistent symptoms such as dyspnea highlight the need for targeted supportive interventions. Longitudinal HRQoL monitoring can guide personalized care and survivorship planning.

Introduction: This study investigates a single-source photon beam model and a single source for contamination electrons for Monte Carlo (MC) simulations. Our approach uses a beam characterization model-to-model clinical photon beams for 6, 8, and 15 MV on a linear accelerator. The flattening filter attenuates the photon fluence in the beam model before reaching the secondary collimation accessories. An error function was used to model scatter from these devices. This study aimed to develop a model for clinical X-ray source beams for MC dose calculations for an Elekta^TM Precise Linac.

Materials and methods: The photon energy was modeled with the Schiff formula and off-axis beam softening. DOSXYZnrc was used to calculate X-ray dose distributions in water and RW3 solid water phantoms. These distributions were compared to measured EBT3 film or water tank dose data. A gamma (γ) index was calculated to compare the MC and the measured dose. The criteria for the γ-index were 2% dose/2 mm distance-to-agreement. Dose distribution data for square, rectangular, offset, and irregular fields were compared with measurements.

Results: A range of fields for 6, 8, and 15 MV beams was modeled, simulated, and compared to corresponding measured water tank data. Rectangular, small, and medium-sized offset fields met the γ-index criteria of 2%/2 mm.

Conclusion: The beam characterization model performed well against measured data and can be employed for dose verification ranging from regular fields to conformal treatments, as demonstrated by various multi-leaf collimator shapes.

Background: Interventional radiology (IR) procedures often require prolonged fluoroscopic imaging, resulting in substantial radiation exposure to both patients and medical staff. Although conventional protective devices are widely used, the scattered radiation beneath the procedural table remains inadequately shielded.

Materials and methods: An additional shielding sheet, fabricated from a discarded 0.25 mmPb lead apron, was developed to block the open space between the interventional table and lead curtain. Phantom-based simulations of bronchial artery embolization (BAE) and transarterial chemoembolization (TACE) have been performed. Optically stimulated luminescence dosimeters were used to measure the radiation doses in the radiosensitive organs of the patient and operator phantoms, both with and without an additional shielding sheet. This study also evaluated dose reduction in the presence or absence of personal protective devices (PPD). Statistical significance was determined using the Wilcoxon signed-rank test (P < 0.05).

Results: When an additional shielding sheet was used, the patient dose was significantly reduced by 20.5% and 20.6% during BAE and TACE, respectively (both P < 0.05). For operators, dose reductions were 68.1% and 43.3% during BAE and TACE with PPD, respectively. Without PPD, the dose was also significantly reduced in both BAE and TACE procedures (P < 0.05).

Conclusions: Additional shielding sheets significantly decreased radiation exposure in both patients and operators during IR procedures. This simple and cost-effective device complements existing shielding tools and enhances radiation safety in clinical practice.

Background: Breast cancer is one of the most common cancers affecting women worldwide. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a highly sensitive technique for the diagnosis of breast cancer, providing comprehensive kinetic analysis of lesions.

Objective: This study aimed to develop an automated method for classifying kinetic curves derived from DCE-MRI into three types - persistent (Type I), plateau (Type II), and washout (Type III) - using a support vector machine (SVM) classifier.

Methods: DCE-MRI scans from 41 histopathologically confirmed breast lesions were analyzed. Region of interest were manually selected by an expert radiologist on the most enhancing solid areas. Kinetic features, including initial enhancement (E_Initial), early signal enhancement ratio, peak enhancement (E_Peak), and four gradient-based slope features, were extracted. A SVM classifier was trained on these features, and performance was evaluated using accuracy, sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve (AUC) to investigate the efficacy in distinguishing between the kinetic curve for each suspicious breast lesion.

Results: The performance of the classification procedure employing the kinetic features with (P < 0.001) was evaluated by means of several measures, including accuracy, sensitivity, specificity, 97.56%, 96.49%, 100%, 100%, and 97.62%, respectively. The results achieved a higher area under the ROC curve (AUC) of 100%.

Conclusion: To diagnose breast lesions, DCE-MRI scans offer an important information, such as kinetic analysis, which is a useful and irreplaceable component of breast diagnostics. This approach may reduce unnecessary biopsies and improve diagnostic efficiency.

Purpose: The purpose of this study was to assess the dosimetric consistency and clinical interchangeability of treatment plans between factory beam-matched Varian TrueBeam SVC and Clinac iX linear accelerators across various anatomical locations.

Materials and methods: Eighty clinical plans were analyzed, including 40 intensity modulated radiotherapy (IMRT) plans (20 for cervix and 20 for head and neck) and 40 volumetric modulated arc therapy (VMAT) plans (20 for breast and 20 for urinary bladder). Both linacs were independently commissioned per AAPM-106 protocols. Plans were recalculated on the alternate machine and compared statistically. Patient-specific QA was performed using ArcCHECK with 3%/2 mm gamma criteria. Transferable fractions were estimated using ICRU-50 (±5%) and AAPM TG-40 (±2%) guidelines to determine fractions safely deliverable without re-planning.

Results: Beam commissioning showed excellent agreement within ±1% for all dosimetric parameters. Head and neck IMRT had minimal differences (D95%: -0.26%, P < 0.001) and the highest transferability (median 39%, 10-14 fractions). Breast VMAT achieved consistent organ-at-risk sparing with moderate transferability (median 19%, 2-4 fractions). Urinary bladder VMAT displayed acceptable transferability (median 29%, 7-11 fractions). Cervical IMRT showed systematic dose increases on TrueBeam (planning target volume D95%: +1.57%, P = 0.012) with limited transferability (median 14%, 1-2 fractions). All plans exceeded gamma passing rates of 97.3%, with VMAT demonstrating superior consistency over IMRT (99.1% vs. 97.3-98.6%).

Conclusions: Linear accelerators that are beam-matched in factories provide safe interchangeability of treatment plans for the majority of clinical scenarios, with VMAT showing improved consistency over IMRT due to continuous arc delivery averaging out minor machine-specific variations in multileaf collimator positioning and dose rate.

Background: This study aimed to investigate and compare the ability of dosiomics features (DFs) and dosimetric parameters (DPs) in detecting variations in dose distribution.

Materials and methods: This research included 15 patients with early-stage breast cancer who had previously undergone radiotherapy using three-dimensional (3D) conformal radiotherapy technique. Four treatment plans are created by different users for each patient. DPs such as D _1%(%), D _5%(%), and …, up to D _100%(%) were analyzed for each region of interest, and DFs were extracted from each plan using 3D-Slicer software. The coefficient of variation (CV) was used to measure the ability of each DFs or DPs to identify differences in dose distribution. CVs were calculated for intrapatient (across four plans) and interpatient (across one plan for all patients) comparisons.

Results: Results showed that the planning target volume (PTV) and heart had the highest CV values in the gray level size zone matrix group (1.05, 0.68). The PTV showed the highest CV for SZM-large area low gray level emphasis, the lung for SZM-Small area low gray level emphasis, and the heart for SZM-size zone nonuniformity. For the D _20%(%) parameter, the heart had the highest CV, followed by the lung and PTV, with CVs of 0.7, 0.56, and 0.51, respectively.

Conclusion: The findings suggest that DFs are more effective than DPs in differentiating between dose distributions. These features could play a key role in future radiotherapy plan evaluations with further study.

Background: In mammography, radiation dose is typically expressed as the mean glandular dose (MGD), which represents the dose delivered to the glandular tissue of the breast.

Materials and methods: This study compares MGD estimates obtained using three different methodologies: (I) MGD-Dance-Laboratory for Individualized Breast Radiodensity Assessment (LIBRA) - Calculated manually for each patient using Dance's formula, incorporating mammographic breast density values derived from the LIBRA application, thereby replacing Dance's standard glandularity assumption with image-specific values; (II) MGD-Dance - Calculated using Dance's formula with the conventional assumption of 50% glandularity; (III) MGD-Displayed - Extracted directly from the Digital Imaging and Communication in Medicine header of each mammogram.

Results: A total of 688 anonymized mammograms from 172 women undergoing routine screening were analyzed, with complete technical and patient-related data. The mean MGD values obtained by the three methods were: MGD-Dance-LIBRA: 2.97 mGy; MGD-Dance: 2.78 mGy; and MGD-Displayed: 2.81 mGy. The average glandularity across the dataset was estimated at 14%. A strong correlation was observed between MGD-Dance and MGD-Dance-LIBRA values (R² =0.9865). The refined dose estimation using image-specific glandularity from LIBRA consistently produced slightly higher values compared to the standard Dance method, highlighting the impact of the commonly assumed 50% glandularity, which overestimates the true average density.

Conclusions: Incorporating individualized breast density estimates from the LIBRA application into Dance's formula provides a more refined and accurate method for calculating MGD in digital mammography.

Aim: Brachytherapy is an integral part of the management of carcinoma cervix. High-dose-rate intracavitary brachytherapy (HDR ICBT) is often delivered after external beam radiotherapy (EBRT) in more than one session. The uncertainties may arise due to variations in anatomy and applicator position during each session, which may impact dose distribution to the clinical target volume (CTV) and normal organs. This study aims to quantify interfraction dose variations in HDR ICBT for cervical cancer patients using computed tomography-based planning.

Materials and methods: In this retrospective study, 30 patients with carcinoma cervix of the International Federation of Gynecology and Obstetrics stage IB2 to IVA after EBRT were included in the study. Total dose for ICBT was 21 Gy delivered in 3 weekly fractions. Doses to CTV, Point A, Point B, and normal organs (rectum, bladder, and sigmoid colon) were recorded in each session. Statistical analysis was conducted using the Chi-square test to compare dose variations between fractions, with a significance level set at P < 0.05.

Results: Mean dose received by 90% of the CTV was 5.92 Gy, 5.77 Gy, and 6.05 Gy for the first, second, and third fractions, respectively. Doses to 0.1 cc of bladder were 8.02 Gy, 7.17 Gy, and 7.51 Gy across fractions, whereas for 1 cc, doses were 6.17 Gy, 5.88 Gy, and 6.15 Gy, respectively. For 1 cc of rectum, doses were 5.60 Gy, 4.90 Gy, and 5.23 Gy, and for 2 cc, 5.17 Gy, 4.34 Gy, and 4.71 Gy, respectively, for three fractions. Sigmoid doses had relatively stable dose variation.

Conclusion: Bladder, rectal, and sigmoid doses varied considerably across fractions, emphasizing the need for strict organ preparation protocols and adaptive dose monitoring.