Potential Defects and Improvements of Equivalent Uniform Dose Prediction Model Based on the Analysis of Radiation-Induced Brain Injury

PurposeTo study the impact of dose distribution on volume-effect parameter and predictive ability of equivalent uniform dose (EUD) model, and to explore the improvements.Methods and MaterialsThe brains of 103 nasopharyngeal carcinoma patients treated with IMRT were segmented according to dose distribution (brain and left/right half-brain for similar distributions but different sizes; VD with different D for different distributions). Predictive ability of EUDVD (EUD of VD) for radiation-induced brain injury was assessed by receiver operating characteristics curve (ROC) and area under the curve (AUC). The optimal volume-effect parameter a of EUD was selected when AUC was maximal (mAUC). Correlations between mAUC, a and D were analyzed by Pearson correlation analysis. Both mAUC and a in brain and half-brain were compared by using paired samples t-tests. The optimal DV and VD points were selected for a simple comparison.ResultsThe mAUC of brain/half-brain EUD was 0.819/0.821 and the optimal a value was 21.5/22. When D increased, mAUC of EUDVD increased, while a decreased. The mAUC reached the maximum value when D was 50–55 Gy, and a was always 1 when D ≥55 Gy. The difference of mAUC/a between brain and half-brain was not significant. If a was in range of 1 to 22, AUC of brain/half-brain EUDV55 Gy (0.857–0.830/0.845–0.830) was always larger than that of brain/half-brain EUD (0.681–0.819/0.691–0.821). The AUCs of optimal dose/volume points were 0.801 (brain D2.5 cc), 0.823 (brain V70 Gy), 0.818 (half-brain D1 cc), and 0.827 (half-brain V69 Gy), respectively. Mean dose (equal to EUDVD with a = 1) of high-dose volume (V50 Gy–V60 Gy) was superior to traditional EUD and dose/volume points.ConclusionVolume-effect parameter of EUD is variable and related to dose distribution. EUD with large low-dose volume may not be better than simple dose/volume points. Critical-dose-volume EUD could improve the predictive ability and has an invariant volume-effect parameter. Mean dose may be the case in which critical-dose-volume EUD has the best predictive ability.

Two-Stage Segmentation Framework Based on Distance Transformation

With the rise of deep learning, using deep learning to segment lesions and assist in diagnosis has become an effective means to promote clinical medical analysis. However, the partial volume effect of organ tissues leads to unclear and blurred edges of ROI in medical images, making it challenging to achieve high-accuracy segmentation of lesions or organs. In this paper, we assume that the distance map obtained by performing distance transformation on the ROI edge can be used as a weight map to make the network pay more attention to the learning of the ROI edge region. To this end, we design a novel framework to flexibly embed the distance map into the two-stage network to improve left atrium MRI segmentation performance. Furthermore, a series of distance map generation methods are proposed and studied to reasonably explore how to express the weight of assisting network learning. We conduct thorough experiments to verify the effectiveness of the proposed segmentation framework, and experimental results demonstrate that our hypothesis is feasible.

Comparison of PSF and Non PSF BLOB based reconstructed image in Time-of-Flight PET/CT

Hybrid PET/CT imaging with the use of 18F FDG is a widely used imaging technique with major indications in oncology for staging, re-staging and monitoring response to therapy. There is a major issue of partial volume effect in PET images which affects image quality as well as quantitative accuracy in small lesions. Multiple attempts have been made to resolve these issues. The aim of our study was to look into impact of Point‐spread-function (PSF) on reconstructed attenuation corrected (AC) images of PET/CT and to find out best combination of the number of PSF iterations with regularization level while applying PSF.

Tumor-to-normal tissue (T/N) dosimetry ratios role in assessment of 90Y selective internal radiation therapy (SIRT)

Objective: The purpose of our work is to assess the role of tumor-to-normal tissue (T/N) dosimetry ratios for predicting response in patients undergoing locoregional therapy to the liver with 90Y microspheres. Methods: 39 patients (seven femal:32 male, mean age 68.3 ± 7.6y), underwent PET/CT imaging after treatment with 90Y microspheres. For attenuation correction and localization of the 90Y microspheres, the low dose, non-diagnostic CT images from PET/CT were used. The acquisition took 15 min and the reconstruction matrix size was 200 × 200×75 mm and voxel size of 4.07 × 4.07×3.00 mm. For dosimetry calculations the local deposition method with known activity of 90Y was used. For each patient, regions-of-interest (ROIs) for tumor(s) and whole liver were manually created; the normal tissue ROI was created automatically. mRECIST criteria on MRI done at a month post treatment and subsequently every three months after90Y treatment, were used to assess response. Results: For 39 patients, the mean liver, tumor and normal tissue doses (mean ± SD) were, 55.17 ± 26.04 Gy, 911.87 ± 866.54 Gy and 47.79 ± 20.47 Gy respectively. Among these patients, 31 (79%) showed complete response (CR) and 8 (21%) showed progression of disease (PD). For patients with CR, the mean T/N dose ratio obtained was 24.91 (range 3.09–80.12) and for patients with PD, the mean T/N dose ratio was significantly lower, at 6.69 (range 0.36–14.75). Conclusion: Our data shows that patients with CR have a statistically higher T/N dose ratio than those with PD. Because, the number of PD cases was limited and partial volume effect was not considered, further investigation is warranted. Advances in knowledge: Tumor-to-normal tissue dosimetry ratios can be used for assessing response in patients undergoing locoregional therapy to the liver with 90Y microspheres.

Radiotherapy-Induced Digestive Injury: Diagnosis, Treatment and Mechanisms

Radiotherapy is one of the main therapeutic methods for treating cancer. The digestive system consists of the gastrointestinal tract and the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder). The digestive system is easily impaired during radiotherapy, especially in thoracic and abdominal radiotherapy. In this review, we introduce the physical classification, basic pathogenesis, clinical characteristics, predictive/diagnostic factors, and possible treatment targets of radiotherapy-induced digestive injury. Radiotherapy-induced digestive injury complies with the dose-volume effect and has a radiation-based organ correlation. Computed tomography (CT), MRI (magnetic resonance imaging), ultrasound (US) and endoscopy can help diagnose and evaluate the radiation-induced lesion level. The latest treatment approaches include improvement in radiotherapy (such as shielding, hydrogel spacers and dose distribution), stem cell transplantation and drug administration. Gut microbiota modulation may become a novel approach to relieving radiogenic gastrointestinal syndrome. Finally, we summarized the possible mechanisms involved in treatment, but they remain varied. Radionuclide-labeled targeting molecules (RLTMs) are promising for more precise radiotherapy. These advances contribute to our understanding of the assessment and treatment of radiation-induced digestive injury.

Theory and Calculation of Nontraditional Stable Isotope Fractionation

This paper conducts processing on isotope anharmonic effect with molecular dynamics method and Monte Carlo method based on path integration. It introduces the theoretical calculation method of pressure effect, and finally the nuclear volume effect and its theoretical calculation method, stressing that the nuclear volume effect is an important part of isotopic studies of heavy metals in the future. This paper makes an analysis on the equilibrium fractionation theory based on simple harmonic approximation.

Influence of Temperature Control of Coke Oven on Life Cycle of Refractories

Different stages of the oven drying are analyzed by the theory of molecular diffusion and crystal change in oven drying process. It’s pointed that in order to ensure uniform expansion and gray seam integrity, the speed of spreading to the outside about within water should be in accordance with the speed of evaporation about surface moisture in the drying period, heating up too quickly will easily lead to extending drying period and destroying masonry rigor. The expansion of silica brick is mainly from the volume effect form with the transition between the allotrope in the expansion period, the heating rate of crystal transformation point must be strictly controlled. At the same time, quartz content should be higher, lesser residual quartz content will be better. The hot state engineering period is consistent with the construction schedule, the construction sequence can’t be reversed, and it is not recommended at this stage to extend the construction period. Effective control of the heating rate of the three stages above lays a solid foundation to extend the oven life.