Optimal Dose Distribution Research Articles

A Knowledge-Based Planning model for IMRT in breast and lung cancer

The advent of Knowledge-Based Planning (KBP) models has introduced a transformative approach to Intensity-Modulated Radiation Therapy (IMRT) treatment planning in breast cancer and lung cancer cases. This paper explores the application of KBP models to these specific cancer types, highlighting their potential to enhance treatment accuracy, efficiency, and patient outcomes. By leveraging historical treatment data and machine learning techniques, KBP-IMRT offers a data-driven framework for optimizing dose distributions, minimizing radiation exposure to healthy tissues, and improving overall treatment plan quality. Through a comprehensive review of the literature and clinical case studies, this paper underscores the advantages of KBP-IMRT, such as streamlined planning processes and improved plan consistency, while acknowledging the challenges associated with model development and implementation. As the field of radiotherapy continues to evolve, KBP models hold the promise of shaping the future of personalized and precise cancer treatment strategies.

Personalized Brachytherapy: Applications and Future Directions

Brachytherapy offers a highly conformal and adaptive approach to radiation therapy for various oncologic conditions. This review explores the rationale, applications, technological advances, and future directions of personalized brachytherapy. Integration of advanced imaging techniques, 3D-printed applicators, and artificial intelligence are rapidly enhancing brachytherapy delivery and efficiency, while genomic tests and molecular biomarkers are refining patient and dose selection. Emerging research on combining brachytherapy with immunotherapy offers unique synergistic potential, and technologies such as intensity-modulated and shielded brachytherapy applicators present novel opportunities to further optimize dose distributions. Despite these promising advances, the field faces challenges including a need to train more practitioners and develop new approaches to treating a broader range of malignancies. As personalized medicine evolves, brachytherapy’s ability to deliver highly targeted, individualized treatments positions it as a critical component in future cancer care.

Analisis Distribusi Dosis pada Treatment Planning System Pasien Kanker Payudara dengan Sumber Foton 6 MV pada Instalasi Radioterapi Rumah Sakit X

The internship at X Hospital aimed to gain practical experience as a medical physicist over two months, particularly in the treatment planning system activities in the radiotherapy unit. Additionally, this internship aimed to evaluate the Dose Volume Histogram (DVH) and analyze the effectiveness of the isodose lines. The treatment planning system is a simulation of cancer or tumor treatment using radiation with 3D conformal radiotherapy (3D-CRT) techniques. The patient study object was a woman with post-mastectomy breast cancer who was to undergo adjuvant curative therapy. The prescribed dose was 50 Gy, divided into 25 fractions, using a 6 MV photon source. The irradiation was conducted with four fields, gantry angle 129° with collimator angle 270°, 310° with collimator angle 90°, 130° with collimator angle 0°, and 270° with collimator angle 0°, field size 14 x 14 cm, and irradiation distance of 100 cm. The TPS simulation results indicated that the dose received by the Planning Target Volume (PTV) covered more than 90% of the target volume (special treatment), while the dose received by the Organ at Risk (OAR) tended to be below the threshold limit, and the isodose lines ensured optimal radiation dose distribution to the breast cancer target area. This was demonstrated by the DVH curve.

Comparison of Photon Dose Distribution in Breast Cancer Using 3DCRT and Half Beam Techniques

Radiotherapy planning can be done with 3D Conformal Radiotherapy (3DCRT) and Half Beam. The success of radiotherapy planning is considered by comparing the isodose curve, Dose Volume Histogram (DVH), Organs At Risk (OAR), Homogeneity Index (HI), and Conformity Index (CI) obtained by the 3DCRT and Half Beam techniques. This study used data from 5 patients at the Radiotherapy Installation at A.W. Hospital. Sjahranie Samarinda with radiation planning of 5000 cGy (25×2 Gy) for breast cancer. The two radiation plans used gantry angles of 310˚ and 120˚. The calculated dose distribution value can be seen through the 90%, 95% PTV dose, and OAR absorbed dose. PTV doses of 90% and 95% in the 3DCRT technique covered the target well. The radiation dose values of the 3DCRT technique at PTV 90% were around 4860 cGy – 4930 cGy and PTV 95% were around 4750 cGy – 4840 cGy. Meanwhile, the Half Beam technique could not cover the target well. It was because the radiation dose values received by the Half Beam technique at 90% PTV were around 780 cGy – 4860 cGy and 95% PTV were around 2210 cGy – 5020 cGy. The OAR absorbed doses values for the 3DCRT and Half Beam techniques were still within the safe limits of tolerance according to QUANTEC. Meanwhile, the HI and CI values in the 3DCRT technique were closer to the rules of ICRU Report 83 of 2010 compared to the Half Beam technique. Therefore, from the values that have been obtained, the success rate of the radiotherapy planning process after measurements is shown in the 3DCRT technique. It has the value of more efficient dose calculations and can be used as a reference in optimizing dose distribution to patients.

169Yb-based high dose rate intensity modulated brachytherapy for focal treatment of prostate cancer

PurposeThis study compares conventional 192Ir-based high dose rate brachytherapy (HDR-BT) with 169Yb-based HDR intensity modulated brachytherapy (IMBT) for focal prostate cancer treatment. Additionally, the study explores the potential to generate less invasive treatment plans with IMBT by reducing the number of catheters needed to achieve acceptable outcomes. Methods and MaterialsA retrospective dosimetric study of ten prostate cancer patients initially treated with conventional 192Ir-based HDR-BT and 5-14 catheters was employed. RapidBrachyMCTPS, a Monte Carlo-based treatment planning system was used to calculate and optimize dose distributions. For 169Yb-based HDR IMBT, a custom 169Yb source combined with 0.8 mm thick platinum shields placed inside 6F catheters was used. Furthermore, dose distributions were investigated when iteratively removing catheters for less invasive treatments. ResultsWith IMBT, the urethra D10 and D0.1cc decreased on average by 15.89 and 15.65 percentage points (pp) and the rectum V75 and D2cc by 1.53 and 11.54 pp, respectively, compared to the conventional clinical plans. Similar trends were observed when the number of catheters decreased. On average, there was an observed increase in PTV V150 from 2.84 pp with IMBT when utilizing all catheters to 8.83 pp when four catheters were removed. PTV V200 increased from 0.42 to 2.96 pp on average. Hotspots in the body were however lower with IMBT compared to conventional clinical plans. Conclusions169Yb-based HDR IMBT for focal treatment of prostate cancer has the potential to successfully deliver clinically acceptable, less invasive treatment with reduced dose to organs at risk.

Prediction of Radiation Therapy Dose Distribution Using Random Forest Algorithm in Volumetric Modulated Arc Therapy Technique for Brain Cancer

Optimization of radiation dose distribution in clinical planning using a Treatment Planning System (TPS) for radiotherapy patients is crucial to achieving a balance between therapeutic effectiveness and patient safety. However, this process is time-consuming and relies heavily on the expertise of medical physicists. In this study, dose prediction using machine learning was performed on the Planning Target Volume (PTV) and Organ at Risk (OAR) for brain cancer cases using the Volumetric Modulated Arc Therapy (VMAT) planning technique. The planning DICOM data were extracted for radiomic and dosiomic values, which were then used as input and output in this study using a random forest algorithm model. Model evaluation results indicated that the random forest model's performance in predicting dose had a Mean Square Error (MSE) value of 0.018. The Homogeneity Index (HI) and Conformity Index (CI) values for the clinical data were 0.136±0.134 and 0.939±0.131 respectively, while the predicted results were 0.136±0.039 and 0.949±0.006, with p-values for PTV and OAR features > 0.05. Thus, it can be concluded that the random forest model is effective in predicting dose for PTV brain cancer and OAR and can function as a reference in the planning process.

A Novel Positive-Contrast Magnetic Resonance Imaging Line Marker for High-Dose-Rate (HDR) MRI-Assisted Radiosurgery (MARS).

Magnetic resonance imaging (MRI) can facilitate accurate organ delineation and optimal dose distributions in high-dose-rate (HDR) MRI-Assisted Radiosurgery (MARS). Its use for this purpose has been limited by the lack of positive-contrast MRI markers that can clearly delineate the lumen of the HDR applicator and precisely show the path of the HDR source on T1- and T2-weighted MRI sequences. We investigated a novel MRI positive-contrast HDR brachytherapy or interventional radiotherapy line marker, C4:S, consisting of C4 (visible on T1-weighted images) complexed with saline. Longitudinal relaxation time (T1) and transverse relaxation time (T2) for C4:S were measured on a 1.5 T MRI scanner. High-density polyethylene (HDPE) tubing filled with C4:S as an HDR brachytherapy line marker was tested for visibility on T1- and T2-weighted MRI sequences in a tissue-equivalent female ultrasound training pelvis phantom. Relaxivity measurements indicated that C4:S solution had good T1-weighted contrast (relative to oil [fat] signal intensity) and good T2-weighted contrast (relative to water signal intensity) at both room temperature (relaxivity ratio > 1; r2/r1 = 1.43) and body temperature (relaxivity ratio > 1; r2/r1 = 1.38). These measurements were verified by the positive visualization of the C4:S (C4/saline 50:50) HDPE tube HDR brachytherapy line marker on both T1- and T2-weighted MRI sequences. Orientation did not affect the relaxivity of the C4:S contrast solution. C4:S encapsulated in HDPE tubing can be visualized as a positive line marker on both T1- and T2-weighted MRI sequences. MRI-guided HDR planning may be possible with these novel line markers for HDR MARS for several types of cancer.

Effective timing of hyaluronate gel injection in image-guided adaptive brachytherapy for uterine cervical cancer: a proposal of the 'adjusted dose score'.

Hyaluronate gel injection (HGI) in the rectovaginal septum and vesicovaginal septum is effective in the setting of high-dose-rate image-guided adaptive brachytherapy (IGABT) for cervical cancer. We aimed to retrospectively investigate optimal conditions for HGI to achieve optimal dose distribution with a minimum number of HGI. We classified 50 IGABT plans of 13 patients with cervical cancer who received IGABT both with and without HGI in the rectovaginal septum and vesicovaginal septum into the following two groups: plan with (number of plans = 32) and plan without (number of plans = 18) HGI. The irradiation dose parameters of high-risk clinical target volume (CTVHR) and organs at risk per fraction were compared between these groups. We also developed the adjusted dose score (ADS), reflecting the overall irradiation dose status for four organs at risk and CTVHR in one IGABT plan and investigated its utility in determining the application of HGI. HGI reduced the maximum dose to the most exposed 2.0cm3 (D2.0 cm3) of the bladder while increasing the minimum dose covering 90% of CTVHR and the percentage of CTVHR receiving 100% of the prescription dose in one IGABT plan without causing any associated complications. An ADS of ≥2.60 was the optimum cut-off value to decide whether to perform HGI. In conclusion, HGI is a useful procedure for improving target dose distribution while reducing D2.0 cm3 in the bladder in a single IGABT plan. The ADS can serve as a useful indicator for the implementation of HGI.

Narrative review of the utility of magnetic resonance imaging in radiotherapy for cervical cancer.

In radiotherapy (RT) for locally advanced cervical cancer, high soft tissue contrast on magnetic resonance imaging (MRI) can ensure accurate delineation of target volumes (TVs) and optimal dose distribution to the RT target and organs at risk (OAR). MRI-guided adaptive RT (MRIgART) is a novel technology that revises RT plans according to anatomical changes occurring throughout the treatment to improve target coverage and minimise OAR toxicity. This review aims to assess the evidence and gaps of MRI use in RT planning and MRIgART in the treatment of cervical cancer, as well as challenges in its clinical implementation. Ovid Medline and PubMed were searched using keywords for MRI in RT for cervical cancer. After applying the inclusion and exclusion criteria, the initial search was deduced to 32 studies. A total of 37 final studies were reviewed, including eight additional articles from references. In the primary studies, TVs and organ motion were assessed before, during, and after treatment. MRI was used to investigate dose distribution and therapeutic response to the treatment in association with its outcome. Lastly, rationales for MRIgART were evaluated. It was concluded that MRI enables accurate target delineation, assessment of organ motion and interfraction changes, and monitoring of treatment response through dynamic parameters. Enhanced target coverage and reduced OAR irradiation through MRIgART can improve local control and the overall outcome, although its rationales against the logistical challenges need to be evaluated on further research.

Robust and optimal dose distribution for brain metastases with robotic radiosurgery system: recipe for an inflection point.

Purpose.This study aims to establish a robust dose prescription methodology in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) for brain metastases, considering geometrical uncertainty and minimising dose exposure to the surrounding normal brain tissue.Methods and Materials.Treatment plans employing 40%-90% isodose lines (IDL) at 10% IDL intervals were created for variously sized brain metastases. The plans were constructed to deliver 21 Gy in SRS. Robustness of each plan was analysed using parameters such as the near minimum dose to the tumour, the near maximum dose to the normal brain, and the volume of normal brain irradiated above 14 Gy.Results.Plans prescribed at 60% IDL demonstrated the least variation in the near minimum dose to the tumour and the near maximum dose to the normal brain under conditions of minimal geometrical uncertainty relative to tumour radius. When the IDL-percentage prescription was below 60%, geometrical uncertainties led to increases in these doses. Conversely, they decreased with IDL-percentage prescriptions above 60%. The volume of normal brain irradiated above 14 Gy was lowest at 60% IDL, regardless of geometrical uncertainty.Conclusions.To enhance robustness against geometrical uncertainty and to better spare healthy brain tissue, a 60% IDL prescription is recommended in SRS and SRT for brain metastases using a robotic radiosurgery system.

Brachyterapy: The radiation oncologist opinion.

The role of the radiation oncologist in the management of patients affected by prostate cancer is increasingly considered thanks to important technological innovations that have marked the radiotherapeutic approach in its three main fields: external beam radiotherapy (EB-RT), brachytherapy (interventional radiotherapy, I-RT), and metabolic radiotherapy (M-RT) through the use of new radiopharmaceuticals. Regarding the modern brachytherapy, the introduction of intensity-modulated techniques (IM-IRT), thanks to the implementation of HDR remote-after loading machines, and image-guided techniques (IG-IRT), has led to advantages in optimizing dose distribution after implantation with the possibility of modulating the dose according to the intraprostatic dominant lesions, limiting the dose to the surrounding tissues with improvement in local control and a significant reduction in side effects. I-RT today represents a safe, scientifically established, effective and well-tolerated treatment for patients affected by prostate cancer. Like most special techniques, in order to obtain the best results, it must be performed in centers with a high volume of activity and consolidated experience with an interdisciplinary approach.

ИСПОЛЬЗОВАНИЕ ВОДНОГО БОЛЮСА ПРИ ЛУЧЕВОЙ ТЕРАПИИ ПАЦИЕНТОВ С ИЗОЛИРОВАННЫМИ ПОВЕРХНОСТНЫМИ ПРОЯВЛЕНИЯМИ Т-КЛЕТОЧНОЙ ЛИМФОМЫ КОЖИ

Purpose: To demonstrate the effectiveness of water bolus, combined with individual immobilization for the treatment of lesions in the pedal region of the foot on a patient with isolated cutaneous T-cell lymphoma lesions. Material and methods: Construction of individual immobilization devices, simultaneously functioning as a bolus, in two clinical cases of T-cell cutaneous lymphoma radiation therapy in the pedal region of the foot, along with 3D-CRT and VMAT treatment planning, accompanied by retrospective evaluation of interfractional motion. Results: The proposed methodology demonstrates the effectiveness of the individual immobilization devices in minimizing interfractional motion, as well as the benefit of the bolus effect of the device in achieving optimal dose distribution in the treatment of superficial T-cell lymphoma lesions.

A Beam Angle Selection Method to Improve Plan Robustness Against Position Error in Intensity-Modulated Radiotherapy for Left-Sided Breast Cancer.

We report a dosimetric study in whole breast irradiation (WBI) of plan robustness evaluation against position error with two radiation techniques: tangential intensity-modulated radiotherapy (T-IMRT) and multi-angle IMRT (M-IMRT). Ten left-sided patients underwent WBI were selected. The dosimetric characteristics, biological evaluation and plan robustness were evaluated. The plan robustness quantification was performed by calculating the dose differences (Δ) of the original plan and perturbed plans, which were recalculated by introducing a 3-, 5-, and 10-mm shift in 18 directions. M-IMRT showed better sparing of high-dose volume of organs at risk (OARs), but performed a larger low-dose irradiation volume of normal tissue. The greater shift worsened plan robustness. For a 10-mm perturbation, greater dose differences were observed in T-IMRT plans in nearly all directions, with higher ΔD98%, ΔD95%, and ΔDmean of CTV Boost and CTV. A 10-mm shift in inferior (I) direction induced CTV Boost in T-IMRT plans a 1.1 (ΔD98%), 1.1 (ΔD95%), and 1.7 (ΔDmean) times dose differences greater than dose differences in M-IMRT plans. For CTV Boost, shifts in the right (R) and I directions generated greater dose differences in T-IMRT plans, while shifts in left (L) and superior (S) directions generated larger dose differences in M-IMRT plans. For CTV, T-IMRT plans showed higher sensitivity to a shift in the R direction. M-IMRT plans showed higher sensitivity to shifts in L, S, and I directions. For OARs, negligible dose differences were found in V20 of the lungs and heart. Greater ΔDmax of the left anterior descending artery (LAD) was seen in M-IMRT plans. We proposed a plan robustness evaluation method to determine the beam angle against position uncertainty accompanied by optimal dose distribution and OAR sparing.

Paediatric radiotherapy in the United Kingdom: an evolving subspecialty and a paradigm for integrated teamworking in oncology.

Many different malignancies occur in children, but overall, cancer in childhood is rare. Survival rates have improved appreciably and are higher compared with most adult tumour types. Treatment schedules evolve as a result of clinical trials and are typically complex and multi-modality, with radiotherapy an integral component of many. Risk stratification in paediatric oncology is increasingly refined, resulting in a more personalized use of radiation. Every available modality of radiation delivery: simple and advanced photon techniques, proton beam therapy, molecular radiotherapy, and brachytherapy, have their place in the treatment of children's cancers. Radiotherapy is rarely the sole treatment. As local therapy, it is often given before or after surgery, so the involvement of the surgeon is critically important, particularly when brachytherapy is used. Systemic treatment is the standard of care for most paediatric tumour types, concomitant administration of chemotherapy is typical, and immunotherapy has an increasing role. Delivery of radiotherapy is not done by clinical or radiation oncologists alone; play specialists and anaesthetists are required, together with mould room staff, to ensure compliance and immobilization. The support of clinical radiologists is needed to ensure the correct interpretation of imaging for target volume delineation. Physicists and dosimetrists ensure the optimal dose distribution, minimizing exposure of organs at risk. Paediatric oncology doctors, nurses, and a range of allied health professionals are needed for the holistic wrap-around care of the child and family. Radiographers are essential at every step of the way. With increasing complexity comes a need for greater centralization of services.

A study on short-term efficacy and safety of Iodine-125 brachytherapy coupled with preoperative arterial chemoembolization for hypervascular spinal metastasis

Hypervascular spinal metastatic malignancies can cause severe pain and intraoperative bleeding and selection of appropriate treatment can be challenging. This study aimed to observe the short-term efficacy and safety of Iodine-125 brachytherapy (125I BT) combined with preoperative transcatheter arterial chemoembolization (TACE) for hypervascular spinal metastasis. This study included a total of 33 patients (39 lesions) with hypervascular spinal metastasis. All of them carried out a regimen of TACE followed by 125I BT under CT guidance. A brachytherapy planning system has been utilized for the purpose of designing treatment plans and optimizing dose distribution. Pain relief was evaluated using a numeric rating scale (NRS) and intraoperative bleeding was recorded. Follow-up was conducted for 6 months to observe the local control rate and clinical complications. All patients tolerated combined treatment well and intraoperative blood loss of every patient was not more than 10 ml. The 2- and 6- month local disease control rates were 92.3% and 83.8%. The NRS scores for thirty-three tumor patients before surgery and after one week, two, and six months of surgery were recorded as 7.33 ± 1.80, 7.39 ± 1.89, 3.15 ± 2.35, and 4.16 ± 2.15, respectively. The NRS score 2 months after treatment was found considerably lower in comparison to the NRS score before operation (p < 0.05). According to our findings, 125I BT as well as preoperative TACE leads to perioperative hemostasis, pain alleviation, and reduced tumor burden, indicating that this combined treatment could be effective and promising for hypervascular spinal metastases.

Tatalaksana Terapi Radiasi Pada Pasien Cito Bleeding Kanker Serviks Di Instalasi Radioterapi RSUD Provinsi NTB

Background: Treatment of radiation therapy in patients with cervical cancer citobleeding at the Radiotherapy Installation of the NTB Provincial Hospital uses a 2D technique with 2 radiation fields, namely AP (Antero Posterior) and PA (Postero Anterior). The aim of this study is to describe the management of radiation therapy in patients with cervical cancer bleeding in the radiotherapy installation of the NTB Provincial Regional Hospital and its advantages and disadvantages. Method: This type of research is qualitative descriptive research with a case study approach. The author conducted interviews with research subjects, namely 1 radiation oncologist, 1 medical physicist and 3 radiographers/RTT. The author took the collected data such as images and medical record data. Data was collected using interview transcripts, then processed using a categorization table and an open coding system. Results: Based on the results of the author's observations and interviews, the management of radiation therapy in Cito bleeding cervical cancer patients at the Radiotherapy Installation of the NTB Provincial Regional Hospital uses a 2D technique with a dose of 3 x 3 Gy per fraction. The advantage of radiation therapy management for patients with bleeding cervical cancer is the use of a 2D technique which is simpler and faster so that the patient can be immediately irradiated, but the disadvantage is that it produces less than optimal dose distribution to the target and organs at risk (OAR). Conclusion: Treatment of radiation therapy in patients with bleeding cervical cancer at the NTB Provincial Hospital Radiotherapy Installation uses a 2D two-field AP and PA technique with a dose of 3 x 3 Gy per fraction to stop bleeding. The advantage of using the 2D technique is that it is faster and simpler, while the disadvantage is that the dose distribution is not optimal.

Impact of proton therapy on the DNA damage induction and repair in hematopoietic stem and progenitor cells

Proton therapy is of great interest to pediatric cancer patients because of its optimal depth dose distribution. In view of healthy tissue damage and the increased risk of secondary cancers, we investigated DNA damage induction and repair of radiosensitive hematopoietic stem and progenitor cells (HSPCs) exposed to therapeutic proton and photon irradiation due to their role in radiation-induced leukemia. Human CD34+ HSPCs were exposed to 6 MV X-rays, mid- and distal spread-out Bragg peak (SOBP) protons at doses ranging from 0.5 to 2 Gy. Persistent chromosomal damage was assessed with the micronucleus assay, while DNA damage induction and repair were analyzed with the γ-H2AX foci assay. No differences were found in induction and disappearance of γ-H2AX foci between 6 MV X-rays, mid- and distal SOBP protons at 1 Gy. A significantly higher number of micronuclei was found for distal SOBP protons compared to 6 MV X-rays and mid- SOBP protons at 0.5 and 1 Gy, while no significant differences in micronuclei were found at 2 Gy. In HSPCs, mid-SOBP protons are as damaging as conventional X-rays. Distal SOBP protons showed a higher number of micronuclei in HSPCs depending on the radiation dose, indicating possible changes of the in vivo biological response.

Development of an automatic optimization program for the weight of multi-field irradiation in BNCT based on a genetic algorithm

ABSTRACT Boron Neutron Capture Therapy (BNCT) is a promising radiotherapy technique for cancer treatment. Optimizing dose distribution in tumors is a significant challenge for BNCT, especially for tumors that are deep-seated. The method of optimizing dose distribution through multi-field irradiation holds great potential for clinical applications in BNCT. This study presents an optimization program that couples genetic algorithm and Monte Carlo simulation, which can automatically optimize irradiation field weights for multi-field irradiation, ensuring optimal dose distribution for cancer patients. Using this program, a glioblastoma case was used to analyze the optimization results for different numbers of irradiation fields. The results demonstrate that the program possesses an efficient and accurate automatic optimization feature for multi-field irradiation weights. The minimum dose, mean dose, and D80% of tumor dose improve with the increase in irradiation fields, while the homogeneity index (HI) of tumor dose decreases, without exceeding dose constraints for organs at risk. The developed optimization program provides a method for determining irradiation field weights in BNCT treatment planning systems, which has the potential to improve treatment outcomes.

Efficacy of drip irrigation with thiamethoxam on control of Monolepta hieroglyphica and uptake, translocation, and dietary risk of thiamethoxam in maize.

Monolepta hieroglyphica (Motschulsky) is an important agricultural pest that causes significant economic losses in terms of crop production. Conventional pesticide spraying treatments can result in pesticide drift, endanger nontarget organisms, and cause pests to fly away, resulting in unsatisfactory prevention and control effects. To study the effect of thiamethoxam on the control of maize M. hieroglyphica, a field experiment was conducted to determine the optimal thiamethoxam application dose, its spatial and temporal distribution dynamics and its dietary risk based on its control effect when applied by spray and drip irrigation. The results of the field trials showed that compared with spray irrigation, drip irrigation resulted in greater control starting from the 5th day. This result was due to the hysteresis effect of thiamethoxam being first absorbed by the roots and then continuously transferred upward, where it accumulates. After 30 days of drip irrigation with 75 and 150 g a.i. ha-1 thiamethoxam, the control effect on M. hieroglyphica was 32.41-49.44% and 69.77-80.57%, respectively. The results of the dietary risk assessment showed that the risk of thiamethoxam ingestion through maize kernels was acceptable regarding its effect on human health. Drip irrigation with thiamethoxam can improve the effective utilization rate of pesticides, achieve precise control of maize M. hieroglyphica, and provide a new method for sustainable agricultural production. This article is protected by copyright. All rights reserved.

From coarse to fine: a deep 3D probability volume contours framework for tumour segmentation and dose painting in PET images.

With the increasing integration of functional imaging techniques like Positron Emission Tomography (PET) into radiotherapy (RT) practices, a paradigm shift in cancer treatment methodologies is underway. A fundamental step in RT planning is the accurate segmentation of tumours based on clinical diagnosis. Furthermore, novel tumour control methods, such as intensity modulated radiation therapy (IMRT) dose painting, demand the precise delineation of multiple intensity value contours to ensure optimal tumour dose distribution. Recently, convolutional neural networks (CNNs) have made significant strides in 3D image segmentation tasks, most of which present the output map at a voxel-wise level. However, because of information loss in subsequent downsampling layers, they frequently fail to precisely identify precise object boundaries. Moreover, in the context of dose painting strategies, there is an imperative need for reliable and precise image segmentation techniques to delineate high recurrence-risk contours. To address these challenges, we introduce a 3D coarse-to-fine framework, integrating a CNN with a kernel smoothing-based probability volume contour approach (KsPC). This integrated approach generates contour-based segmentation volumes, mimicking expert-level precision and providing accurate probability contours crucial for optimizing dose painting/IMRT strategies. Our final model, named KsPC-Net, leverages a CNN backbone to automatically learn parameters in the kernel smoothing process, thereby obviating the need for user-supplied tuning parameters. The 3D KsPC-Net exploits the strength of KsPC to simultaneously identify object boundaries and generate corresponding probability volume contours, which can be trained within an end-to-end framework. The proposed model has demonstrated promising performance, surpassing state-of-the-art models when tested against the MICCAI 2021 challenge dataset (HECKTOR).