Accurate Dose Delivery Research Articles

Anatomy-Guided Deep Learning Model for Accurate and Robust Gross Tumor Volume Segmentation in Lung Cancer Radiation Therapy

In lung cancer radiation therapy, clinicians must outline the gross tumor volume (GTV) precisely on the planning computed tomography (pCT) for accurate radiation dose delivery. However, due to the limited contrast between tumor and normal tissues in lung parenchyma, accurate delineation of tumor boundaries is difficult leading to large inter-observer variation. In this study, we develop an anatomy-guided lung GTV deep segmentation model using a training cohort of multi-center datasets. The quantitative segmentation performance is evaluated on an independent dataset, where the inter-observer delineation variation is also assessed. We collected and curated four publicly available lung datasets with GTV annotations (Lung-PET-CT-Dx, LIDC-IDRI, NSCLC-Radiogenomics and RIDER-CT) for deep learning model development. A total of 871 CT scans of patients, who were diagnosed with T1-T4 NSCLC, were available for training after data curation. The GTV annotations of primary tumor were examined and edited by two experienced radiation oncologists following the RTOG 1106 protocol. An anatomy-guided deep learning model was proposed, which consisted two deep networks. The first deep network used CT scan as input and segmented 4 anatomic organs (airway, heart, pulmonary artery and pulmonary vein), while the second deep network took both CT scan and these pre-segmented 4 organs as input and segmented the lung GTV. With the help of anatomic priors from 4 pre-segmented organs, the second deep network could more easily locate the GTV. We used nnUNet as the deep segmentation network. For evaluation, we used NSCLC-Radiomics as the testing dataset, which contains 20 CT scans each annotated by 5 radiation oncologists. The auto-segmented GTV were compared against each of the manual GTV reference. Inter-observer variation was also assessed using the 5 manual GTV references. The proposed anatomic-guided lung GTV segmentation model achieved a mean Dice score of 82.4% and 95% Hausdorff distance (HD95) of 6.9mm when averaged cross 20 patients and 5 GTV references (Table 1), which outperformed the basic deep GTV segmentation model by markedly reducing 19.4% HD95 error. The performance of proposed model was also comparable to the inter-observer variation (Dice score: 82.4% vs. 81.9%, HD95 6.9 vs. 6.4mm), indicating that our model had similar reproducibility as human observers. We developed and tested an anatomy-guided deep learning model for segmenting GTV in NSCLC patients. The model achieves high quantitative segmentation performance, which is comparable to the human observer variation. It can be potentially used in radiotherapy practice to improve GTV delineation consistency and reduce workloads of radiation oncologists.

The Robotic System for the Treatment of Locally Advanced Cervical Cancer with Stereotactic Body Radiotherapy Boost: Results of a Phantom-Based and Preliminary Study

To fix uterocervical position, compensate uterocervical intrafraction motion, and thus improve the accuracy of dose delivery based on the robotic system for the treatment of locally advanced cervical cancer with stereotactic body radiotherapy boost. CT images were acquired after robot arm implanted a fixator with fiducial markers into the cervix of pelvic phantom. The treatment plans were designed by contoured a simulated tumor lesion site. The fiducial markers position was obtained by real-time image guidance system and was registered with digitally reconstructed radiographs to calculate correlation error of six directions. The correlation error was delivered to the robotic arm to precisely adjust the position and posture of the fixator, and thus compensated uterocervical intrafraction movement through the interactive interface of the robotic system. The pressure sensor at the head of the fixator provided real-time feedback on the pressure value at the contact surface between the fixer and the cervix. The correlation error of six directions and the pressure value were extracted and analyzed from the log file. The data from the log file indicated that the three translational direction correlation error of x, y and z were 0.19mm, 0.20mm and 0.10mm, respectively. The three rotational direction correlation error of roll, pitch and yaw were 0.25°, 0.21° and 0.23°, respectively. With the increase of the relative distance between cervix and pressure sensor, the mean value of pressure variation decreases gradually. When the relative distance is 0.5mm and 3mm, the mean value of pressure variation is approximately 76% and 32%, respectively. The correlation accuracy of the robotic system meets the clinical requirements. The robot arm can fix and monitor the cervical motion in real time during radiotherapy. The robot system adjusts the position of the fixator to correct the uterocervical intrafraction motion error, which is feasible and has good clinical application prospect.

Development of Novel Focal Irradiation Tool for High-Precision Irradiation Using Clinical Brachytherapy System

Several small animals, including mice, are used to conduct research on state-of-the-art radiation therapy techniques or treatment-related toxicity. However, it is difficult to conduct the focal irradiation to a shallow depth on small animals, because irradiation using LINAC has limitations in energy and field size. The purpose of this paper was to develop a focal irradiation tool for high-precision irradiation and to evaluate beam characteristics. We designed the collimator of 1 mm diameter consisting of tungsten material for high-precision irradiation applied to the clinical brachytherapy system and the percent depth dose and horizontal profile were measured. We compared the depth dose and horizontal profile with 4 mm diameter SRS cone for 6 MV in LINAC. We measured the PDD and horizontal profile using EBT3 film for high-precision irradiation of 1 mm diameter using Ir-192 source. In case of 4 mm diameter, the beam was measured using edge detector. In addition, all measurements were compared with the results of planning tool simulation. In case of focal irradiation tool, the maximum dose showed at the surface for both measurement and simulation, and 26% and 32% doses at 1 mm depth, respectively. In addition, FWHM at a 1 mm depth showed that high-precision irradiation was possible with measurement and simulation results of 1.86 and 1.28 mm. In case of LINAC, the maximum dose was showed at a depth of 1 cm and 0.8 cm in the measurement and simulation, respectively. Even if the smallest cone is used, the FWHM at a dmax depth was 4.0 mm in both simulation and measurement. We overcame the limitation for energy and field size through the focal irradiation tool for high-precision irradiation. The focal irradiation tool enables high dose delivery to the shallow depth. In addition, small FWHM reduced dose delivery to the periphery at a specific depth and enabled accurate dose delivery. These results mean that the focal irradiation tool can be useful in small animal experiments that require accurate doses near the shallow depth.

Evaluation of Treatment Interruptions and Recovery during Biology-Guided Radiotherapy Delivery

A Biology-guided Radiotherapy (BgRT) based device is designed to use Positron Emission Tomography (PET) signals to achieve tracked dose delivery. The goal of this study is to investigate the dose delivery accuracy in case of interruption during BgRT treatment, and resumption in a separate treatment session for a multi-target delivery, as the PET activity continues to decay. A custom-built large anthropomorphic phantom (LAP) including a 26 mm spherical target with 3D independent motion and two 22 mm spherical targets with 1D sinusoidal motion embedded in water was used. All three targets were filled with FGD in an 8:1 target to background uptake ratio (41.52 kBq/ml in target and 5.19 kBq/ml in background). During BgRT delivery, the treatment was intentionally paused during delivery to the second target and the current treatment session was ended to generate a partial fraction. Then the partial fraction was continued in a new session, where the CT scan localization and PET pre-scan were repeated using the existing PET activity present in the phantom. The newly acquired PET pre-scan, was then used to determine if sufficient PET counts were present to resume treatment delivery. The interruption and recovery algorithm is designed to calculate the fluence that needs to be delivered to the remaining targets as well as the residual fluence to be given to the targets that have already received partial dose prior to the interruption. Once the new fluence is recomputed, the treatment is resumed. The delivered doses were captured using radiochromic film (EBT-XD) inserted in the target as well as post-treatment dose calculations based on the delivered beamlet sequence to evaluate the results in terms of dosimetric coverage and margin loss. The margin loss is calculated as the maximum difference between the distance from the Clinical Target Volume (CTV) contour to the 97% isodose contour in the treatment plan and the on the film. The dosimetric coverage is defined as the percentage of voxels within the CTV that lies within 97% and 130% of the prescribed dose. As shown in the table below, a margin loss of less than 3 mm for all targets and 100% CTV coverage was achieved. After treatment interruptions, the PET safety evaluation based on the PET pre-scan helped to determine whether the treatment could be continued on the same day using the same injected PET activity (an NTS value ≧ 2 and AC value ≧ 5 kBq/ml). This study demonstrated that the BgRT system is able to deliver the prescribed dose to all targets with independent motion, even when an interruption and resumption occurs during treatment. In case such an interruption if the remaining PET activity satisfies the BgRT safety evaluation, the treatment can continue to deliver the remainder of the BgRT doses.

Assessment of interfraction dose variation in pancreas SBRT using daily simulation MR images

Pancreatic Cancer is associated with poor treatment outcomes compared to other cancers. High local control rates have been achieved by using hypofractionated stereotactic body radiotherapy (SBRT) to treat pancreatic cancer. Challenges in delivering SBRT include close proximity of several organs at risk (OARs) and target volume inter and intra fraction positional variations. Magnetic resonance image (MRI) guided radiotherapy has shown potential for online adaptive radiotherapy for pancreatic cancer, with superior soft tissue contrast compared to CT. The aim of this study was to investigate the variability of target and OAR volumes for different treatment approaches for pancreatic cancer, and to assess the suitability of utilizing a treatment-day MRI for treatment planning purposes. Ten healthy volunteers were scanned on a Siemens Skyra 3 T MRI scanner over two sessions (approximately 3 h apart), per day over 5 days to simulate an SBRT daily simulation scan for treatment planning. A pretreatment scan was also done to simulate patient setup and treatment. A 4D MRI scan was taken at each session for internal target volume (ITV) generation and assessment. For each volunteer a treatment plan was generated in the Raystation treatment planning system (TPS) following departmental protocols on the day one, first session dataset (D1S1), with bulk density overrides applied to enable dose calculation. This treatment plan was propagated through other imaging sessions, and the dose calculated. An additional treatment plan was generated on each first session of each day (S1) to simulate a daily replan process, with this plan propagated to the second session of the day. These accumulated mock treatment doses were assessed against the original treatment plan through DVH comparison of the PTV and OAR volumes. The generated ITV showed large variations when compared to both the first session ITV and daily ITV, with an average magnitude of 22.44% ± 13.28% and 25.83% ± 37.48% respectively. The PTV D95 was reduced by approximately 23.3% for both plan comparisons considered. Surrounding OARs had large variations in dose, with the small bowel V30 increasing by 128.87% when compared to the D1S1 plan, and 43.11% when compared to each daily S1 plan. Daily online adaptive radiotherapy is required for accurate dose delivery for pancreas cancer in the absence of additional motion management and tumour tracking techniques.

Can Optical Surface Imaging Replace Non-coplanar Cone-beam Computed Tomography for Non-coplanar Set-up Verification in Single-isocentre Non-coplanar Stereotactic Radiosurgery and Hypofractionated Stereotactic Radiotherapy for Single and Multiple Brain Metastases?

AimsTo conduct a direct comparison regarding the non-coplanar positioning accuracy between the optical surface imaging system Catalyst HDTM and non-coplanar cone-beam computed tomography (NC-CBCT) in intracranial single-isocentre non-coplanar stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (HSRT). Materials and methodsTwenty patients with between one and five brain metastases who underwent single-isocentre non-coplanar volumetric modulated arc therapy (NC-VMAT) SRS or HSRT were enrolled in this study. For each non-zero couch angle, both Catalyst HDTM and NC-CBCT were used for set-up verification prior to beam delivery. The set-up error reported by Catalyst HDTM was compared with the set-up error derived from NC-CBCT, which was defined as the gold standard. Additionally, the dose delivery accuracy of each non-coplanar field after using Catalyst HDTM and NC-CBCT for set-up correction was measured with SRS MapCHECKTM. ResultsThe median set-up error differences (absolute values) between the two positioning methods were 0.30 mm, 0.40 mm, 0.50 mm, 0.15°, 0.10° and 0.10° in the vertical, longitudinal, lateral, yaw, pitch and roll directions, respectively. The largest absolute set-up error differences regarding translation and rotation were 1.5 mm and 1.1°, which occurred in the longitudinal and yaw directions, respectively. Only 35.71% of the pairs of measurements were within the tolerance of 0.5 mm and 0.5° simultaneously. In addition, the non-coplanar field with NC-CBCT correction yielded a higher gamma passing rate than that with Catalyst HDTM correction (P < 0.05), especially for evaluation criteria of 1%/1 mm with a median increase of 12.8%. ConclusionsCatalyst HDTM may not replace NC-CBCT for non-coplanar set-up corrections in single-isocentre NC-VMAT SRS and HSRT for single and multiple brain metastases. The potential role of Catalyst HDTM in intracranial SRS/HSRT needs to be further studied in the future.

Quality Control of Brachytherapy Equipment in Kazakhstan: Current Stage and Minimum Requirements.

Brachytherapy is used in 17 radiotherapy facilities In Kazakhstan. Each institution has an individual quality control (QC) program in place to ensure the safe and accurate delivery of the treatment dose to the patient. The main objective of this paper is to explore current approaches to quality control of brachytherapy in Kazakhstan and reduce potential discrepancies in testing frequency and tolerance limits by identifying a set of basic quality control requirements. A detailed brachytherapy quality control questionnaire was provided to 17 radiotherapy institutions for completion. A separate questionnaire was sent to two institutions associated with brachytherapy. Questions addressed safety aspects, radiation parameters, total time spent on quality control, and available imaging systems for dose determination. The results of the survey were compared with the recommendations set found in international brachytherapy quality control documents. The results of the questionnaires revealed significant differences in the frequency and methods of testing. For example, only two of the 17 centers have at least some kind of quality assurance program for brachytherapy treatment. Only five centers have equipment with the help of which dosimetric control can be performed, and only two centers have local medical physicists performing this control. One of the centers is checked quarterly, while the other is checked only once a year. In the remaining 15 centers, dosimetric control is performed by specialists who recharge the source without providing any document or protocol. There were also significant differences in the amount of time spent on quality control, mostly related to the variety of approaches to quality control and differences in the availability of resources. Almost all centers (15 of 17) rely only on inspections from the radionuclide source supplier and do not monitor the dosimetric and mechanical parameters of the facility at all. Based on the results of the survey and comparison with international recommendations, a set of basic requirements for brachytherapy quality control is needed.

Picoscience: Picotechnology’s Advent in Health and Medicine

Abstract: As the human race evolves, numerous diseases have dominated humans, causing scientists to encounter myriad challenges with formulations. To rectify these issues, Nanoparticle (10-9 m) formulation approach or nanotechnology has been developed. Since nanoparticles have legion benefits, encompassing better bioavailability, target-specific, confined, accurate dose delivery, and increased surface area, are pertinent for effective treatment. Toxicity, inflammation, limited penetrating ability, accumulation, and aggregation are some of the downsides of nanoparticles. Picoscale along with nanoparticle technology in drug delivery, will enhance the permeability and myriad factors. Also, picometer (10-12 m) and futuristic femtometer (10-15 m) particles will allow scientists to deal with atomic and subatomic levels in some cases and improve the properties of nanotechnology in others. Herein, picotechnology, formulation, synthesis, and some unique properties concluding with femtotechnology have been addressed.

Reducing the margin in prostate radiotherapy: optimizing radiotherapy with a general-purpose linear accelerator using an in-house position monitoring system.

To study the feasibility of optimizing the Clinical Target Volume to Planning Target Volume (CTV-PTV) margin in prostate radiotherapy(RT) with a general-purpose linear accelerator using an in-house developed position monitoring system, SeedTracker. A cohort of 30 patients having definitive prostate radiotherapy treated within an ethics-approved prospective trial was considered for this study. The intrafraction prostate motion and the position deviations were measured using SeedTracker system during each treatment fraction. Using this data the CTV-PTV margin required to cover 90% of the patients with a minimum of 95% of the prescription dose to CTV was calculated using van Herk's formula. The margin calculations were performed for treatment scenarios both with and without applying the position corrections for observed position deviations. The feasibility of margin reduction with real-time monitoring was studied by assessing the delivered dose that incorporates the actual target position during treatment delivery and comparing it with the planned dose. This assessment was performed for plans generated with reduced CTV-PTV margin in the range of 7mm-3mm. With real-time monitoring and position corrections applied the margin of 2.0mm, 2.1mm and 2.1mm in LR, AP and SI directions were required to meet the criteria of 90% population to receive 95% of the dose prescription to CTV. Without position corrections applied for observed position deviations a margin of 3.1mm, 4.0mm and 3.0mm was required in LR, AP and SI directions to meet the same criteria. A mean ± SD reduction of 0.5 ± 1.8% and 3 ± 7% of V60 for the rectum and bladder can be achieved for every 1mm reduction of PTV margin. With position corrections applied, the CTV D99 can be delivered within -0.2 ± 0.3 Gy of the planned dose for plans with a 3mm margin. Without applying corrections for position deviations the CTV D99 was reduced by a maximum of 1.1 ± 1.1 Gy for the 3mm margin plan and there was a statistically significant difference between planned and delivered dose for 3mm and 4mm margin plans. This study demonstrates the feasibility of reducing the margin in prostate radiotherapy with SeedTracker system without compromising the dose delivery accuracy to CTV while reducing dose to critical structures.

Surface guided radiation therapy with an innovative open-face mask and mouth bite: patient motion management in brain stereotactic radiotherapy.

To guarantee treatment reproducibility and stability, immobilization devices are essential. Additionally, surface-guided radiation therapy (SGRT) serves as an accurate complement to frameless stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) by aiding patient positioning and real-time monitoring, especially when non-coplanar fields are in use. At our institute, we have developed a surface-guided SRS (SG-SRS) workflow that incorporates our innovative open-face mask (OM) and mouth bite (MB) to guarantee a precise and accurate dose delivery. This study included 40 patients, and all patients were divided into closed mask (CM) and open-face mask (OM) groups according to different positioning flow. Cone beam computed tomography (CBCT) scans were performed, and the registration results were recorded before and after the treatment. Then Bland-Altman method was used to analyze the consistency of AlignRT-guided positioning errors and CBCT scanning results in the OM group. The error changes between 31 fractions in one patient were recorded to evaluate the feasibility of monitoring during treatment. The median of translation error between stages of the AlignRT positioning process was (0.03-0.07) cm, and the median of rotation error was (0.20-0.40)°, which were significantly better than those of the Fraxion positioning process (0.09-0.11) cm and (0.60-0.75)°. The mean bias values between the AlignRT guided positioning errors and CBCT were 0.01cm, -0.07cm, 0.03cm, -0.30°, -0.08° and 0.00°. The 31 inter-fractional errors of a single patient monitored by SGRT were within 0.10cm and 0.50°. The application of the SGRT with an innovative open-face mask and mouth bite device could achieve precision positioning accuracy and stability, and the accuracy of the AlignRT system exhibits excellent constancy with the CBCT gold standard. The non-coplanar radiation field monitoring can provide reliable support for motion management in fractional treatment.

Technical note: Multi-MATE, a high-throughput platform for automated image-guidedsmall-animal irradiation.

Small animal irradiation is essential to study the radiation response of new interventions before or parallel to human therapy. Image-guided radiotherapy (IGRT) and intensity-modulated radiotherapy (IMRT) are recently adopted in small animal irradiation to more closely mimic human treatments. However, sophisticated techniques require exceedingly high time, resources, and expertize that are often impractical. We propose a high throughput and high precision platform named Multiple Mouse Automated Treatment Environment (Multi-MATE) to streamline image-guided small animal irradiation. Multi-MATE consists of six parallel and hexagonally arranged channels, each equipped with a transfer railing, a 3D-printed immobilization pod, and an electromagnetic control unit, computer-controlled via an Arduino interface. The mouse immobilization pods are transferred along the railings between the home position outside the radiation field and the imaging/irradiation position at the irradiator isocenter. All six immobilization pods are transferred to the isocenter in the proposed workflow for parallel CBCT scans and treatment planning. The immobilization pods are then sequentially transported to the imaging/therapy position for dose delivery. The positioning reproducibility of Multi-MATE are evaluated using CBCT and radiochromic films. While parallelizing and automating the image-guided small animal radiation delivery, Multi-MATE achieved the average pod position reproducibility of 0.17 ± 0.04 mm in the superior-inferior direction, 0.20 ± 0.04 mm in the left-right direction, and 0.12 ± 0.02mm in the anterior-posterior direction in repeated CBCT tests. Additionally, in image-guided dose delivery tasks, Multi-MATE demonstrated the positioning reproducibility of 0.17 ± 0.06 mm in the superior-inferior direction, 0.19 ± 0.06 mm in the left-right direction. We designed, fabricated, and tested a novel automated irradiation platform, Multi-MATE to accelerate and automate image-guided small animal irradiation. The automated platform minimizes human operation and achieves high setup reproducibility and image-guided dose delivery accuracy. Multi-MATE thus removes a major barrier to implementing high-precision preclinical radiation research.

Dosimetry impact of distinct gating strategies in cine MR image-guided breath-hold pancreatic cancer radiotherapy.

To investigate the dosimetry effects of different gating strategies in cine magnetic resonance imaging (MRI)-guided breath-hold pancreatic cancer radiotherapy. Two cine MRI-based gating strategies were investigated： a tumor contour-based gating strategy at a gating threshold of 0-5% and a tumor displacement-based gating strategy at a gating threshold of 3-5 mm. The cine MRI videos were obtained from 17 pancreatic cancer patients who received MRI-guided radiation therapy. We calculated the tumor displacement in each cine MR frame that satisfied the gating threshold and obtained the proportion of frames with different displacements. We generated IMRT and VMAT plans using a 33 Gy prescription, and motion plans were generated by adding up all isocenter-shift plans corresponding to different tumor displacements. The dose parameters of GTV, PTV, and organs at risk (OAR) were compared between the original and motion plans. In both gating strategies, the difference was significant in PTV coverage but not in GTV coverage between the original and motion plans. OAR dose parameters deteriorate with increasing gating threshold. The beam duty cycle increased from 19.5±14.3% (median 18.0%) to 60.8±15.6% (61.1%) for gating thresholds from 0% to 5% in tumor contour-based gating and from 51.7±11.5% (49.7%) to 67.3±12.4% (67.1%) for gating thresholds from 3 to 5 mm in tumor displacement-based gating. In tumor contour-based gating strategy, the dose delivery accuracy deteriorates while the dose delivery efficiency improves with increasing gating thresholds. To ensure treatment efficiency, the gating threshold might be no less than 3%. A threshold up to 5% may be acceptable in terms of the GTV coverage. The displacement-based gating strategy may serve as a potential alternative to the tumor contour based gating strategy, in which the gating threshold of approximately 4 mm might be a good choice for reasonably balancing the dose delivery accuracy and efficiency.

Investigation of total skin helical tomotherapy using a 3D-printed total skin bolus

ObjectiveTo investigate the effectiveness of using a 3D-printed total skin bolus in total skin helical tomotherapy for the treatment of mycosis fungoides.Materials and methodsA 65-year-old female patient with a 3-year history of mycosis fungoides underwent treatment using an in-house desktop fused deposition modelling printer to create a total skin bolus made of a 5-mm-thick flexible material, which increased the skin dose through dose building. The patient's scan was segmented into upper and lower sections, with the division line placed 10 cm above the patella. The prescription was to deliver 24 Gy over 24 fractions, given 5 times per week. The plan parameters consisted of a field width of 5 cm, pitch of 0.287 and modulation factor of 3. The complete block was placed 4 cm away from the planned target region to reduce the area of the internal organs at risk, especially the bone marrow. Dose delivery accuracy was verified using point dose verification with a "Cheese" phantom (Gammex RMI, Middleton, WI), 3D plane dose verification with ArcCHECK (Model 1220, Sun Nuclear, Melbourne, FL), and multipoint film dose verification. Megavoltage computed tomography guidance was also utilized to ensure the accuracy of the setup and treatment.ResultsA 5-mm-thick 3D-printed suit was used as a bolus to achieve a target volume coverage of 95% of the prescribed dose. The conformity index and homogeneity index of the lower segment were slightly better than those of the upper segment. As the distance from the skin increased, the dose to the bone marrow gradually decreased, and the dose to other organs at risk remained within clinical requirements. The point dose verification deviation was less than 1%, the 3D plane dose verification was greater than 90%, and the multipoint film dose verification was less than 3%, all of which confirmed the accuracy of the delivered dose. The total treatment time was approximately 1.5 h, which included 0.5 h of wearing the 3D-printed suit and 1 h with the beam on. Patients only experienced mild fatigue, nausea or vomiting, low-grade fever, and grade III bone marrow suppression.ConclusionThe use of a 3D-printed suit for total skin helical tomotherapy can result in a uniform dose distribution, short treatment time, simple implementation process, good clinical outcomes, and low toxicity. This study presents an alternative treatment approach that can potentially yield improved clinical outcomes for mycosis fungoides.

Sometimes it is better to just make it simple. De-escalation of oncoplastic and reconstructive procedures.

Simple breast conservation surgery (sBCS) has technically advanced onto oncoplastic breast procedures (OBP) to avoid mastectomy and improve breast cancer patients' psychosocial well-being and cosmetic outcome. Although OBP are time-consuming and expensive, we are witnessing an increase in their use, even for cases that could be managed with sBCS. The choice between keeping it simple or opting for more complex oncoplastic procedures is difficult. This review proposes a pragmatic approach in assisting this decision. Medical literature suggests that OBP and sBCS might be similar regarding local recurrence and overall survival, and patients seem to have higher satisfaction levels with the aesthetic outcome of OBP when compared to sBCS. However, the lack of comprehensive high-quality research assessing their safety, efficacy, and patient-reported outcomes hinders these supposed conclusions. Postoperative complications after OBP may delay the initiation of adjuvant RT. In addition, precise displacement of the breast volume is not effectively recorded despite surgical clips placement, making accurate dose delivery tricky for radiation oncologists, and WBRT preferable to APBI in complex OBP cases. With a critical eye on financial toxicity, patient satisfaction, and oncological outcomes, OBP must be carefully integrated into clinical practice. The thoughtful provision of informed consent is essential for decision-making between sBCS and OBP. As we look into the future, machine learning and artificial intelligence can potentially help patients and doctors avoid postoperative regrets by setting realistic aesthetic expectations.

Conditional-based Transformer network with learnable queries for 4D deformation forecasting and tracking.

Real-time motion management for image-guided radiation therapy interventions plays an important role for accurate dose delivery. Forecasting future 4D deformations from in-plane image acquisitions is fundamental for accurate dose delivery and tumor targeting. However, anticipating visual representations is challenging and is not exempt from hurdles such as the prediction from limited dynamics, and the high-dimensionality inherent to complex deformations. Also, existing 3D tracking approaches typically need both template and search volumes as inputs, which are not available during real-time treatments. In this work, we propose an attention-based temporal prediction network where features extracted from input images are treated as tokens for the predictive task. Moreover, we employ a set of learnable queries, conditioned on prior knowledge, to predict future latent representation of deformations. Specifically, the conditioning scheme is based on estimated time-wise prior distributions computed from future images available during the training stage. Finally, we propose a new framework to address the problem of temporal 3D local tracking using cine 2D images as inputs, by employing latent vectors as gating variables to refine the motion fields over the tracked region. The tracker module is anchored on a 4D motion model, which provides both the latent vectors and the volumetric motion estimates to be refined. Our approach avoids auto-regression and leverages spatial transformations to generate the forecasted images. The tracking module reduces the error by 63% compared to a conditional-based transformer 4D motion model, yielding a mean error of 1.5±1.1 mm. Furthermore, for the studied cohort of abdominal 4D MRI images, the proposed method is able to predict future deformations with a mean geometrical error of 1.2±0.7 mm.

Online adaptive radiotherapy and dose delivery accuracy: A retrospective analysis.

With online adaptive radiotherapy (ART), patient-specific quality assurance (PSQA) testing cannot be performed prior to delivery of the adapted treatment plan. Consequently, the dose delivery accuracy of adapted plans (i.e., the ability of the system to interpret and deliver the treatment as planned) are not initially verified. We investigated the variation in dose delivery accuracy of ART on the MRIdian 0.35T MR-linac (Viewray Inc., Oakwood, USA) between initial plans and their respective adapted plans, by analyzing PSQA results. We considered the two main digestive localizations treated with ART (liver and pancreas). A total of 124 PSQA results acquired with the ArcCHECK (Sun Nuclear Corporation, Melbourne, USA) multidetector system were analyzed. PSQA result variations between the initial plans and their respective adapted plans were statistically investigated and compared with the variation in MU number. For the liver, limited deterioration in PSQA results was observed, and was within the limits of clinical tolerance (Initial=98.2%, Adapted=98.2%, p=0.4503). For pancreas plans, only a few significant deteriorations extending beyond the limits of clinical tolerance were observed and were due to specific, complex anatomical configurations (Initial=97.3%, Adapted=96.5%, p=0.0721). In parallel, we observed an influence of the increase in MU number on the PSQA results. We show that the dose delivery accuracy of adapted plans, in terms of PSQA results, is preserved in ART processes on the 0.35T MR-linac. Respecting good practices, and minimizing the increase in MU number can help to preserve the accuracy of delivery of adapted plans as compared to their respective initial plans.

Realistic CT data augmentation for accurate deep-learning based segmentation of head and neck tumors in kV images acquired during radiation therapy.

Using radiation therapy (RT) to treat head and neck (H&N) cancers requires precise targeting of the tumor to avoid damaging the surrounding healthy organs. Immobilisation masks and planning target volume margins are used to attempt to mitigate patient motion during treatment, however patient motion can still occur. Patient motion during RT can lead to decreased treatment effectiveness and a higher chance of treatment related side effects. Tracking tumor motion would enable motion compensation during RT, leading to more accurate dose delivery. The purpose of this paper is to develop a method to detect and segment the tumor in kV images acquired during RT. Unlike previous tumor segmentation methods for kV images, in this paper a process for generating realistic and synthetic CT deformations was developed to augment the training data, and make the segmentation method robust to patient motion. Detecting the tumor in 2D kV images is a necessary step towards 3D tracking of the tumor position during treatment. In this paper a conditional generative adversarial network (cGAN) is presented that can detect and segment the gross tumor volume (GTV) in kV images acquired during H&N RT. Retrospective data from 15 H&N cancer patients obtained from the Cancer Imaging Archive were used to train and test patient-specific cGANs. The training data consisted of digitally reconstructed radiographs (DRRs) generated from each patient's planning CT and contoured GTV. Training data was augmented by using synthetically deformed CTs to generate additional DRRs (in total 39600 DRRs per patient or 25200 DRRs for nasopharyngeal patients) containing realistic patient motion. The method for deforming the CTs was a novel deformation method based on simulating head rotation and internal tumor motion. The testing dataset consisted of 1080 DRRs for each patient, obtained by deforming the planning CT and GTV at different magnitudes to the training data. The accuracy of the generated segmentations was evaluated by measuring the segmentation centroid error, Dice similarity coefficient (DSC) and mean surface distance (MSD). This paper evaluated the hypothesis that when patient motion occurs, using a cGAN to segment the GTV would create a more accurate segmentation than no-tracking segmentations from the original contoured GTV, the current standard-of-care. This hypothesis was tested using the 1-tailed Mann-Whitney U-test. The magnitude of our cGAN segmentation centroid error was (mean ± standard deviation) 1.1 ± 0.8 millimeters and the DSC and MSD values were 0.90 ± 0.03 and 1.6 ± 0.5 millimeters respectively. Our cGAN segmentation method reduced the segmentation centroid error (p<0.001), and MSD (p = 0.031) when compared to the no-tracking segmentation, but did not significantly increase the DSC (p = 0.294). The accuracy of our cGAN segmentation method demonstrates the feasibility of this method for H&N cancer patients during RT. Accurate tumor segmentation of H&N tumors would allow for intrafraction monitoring methods to compensate for tumor motion during treatment, ensuring more accurate dose delivery and enabling better H&N cancer patient outcomes. This article is protected by copyright. All rights reserved.

A new target localization method for image-guided radiation therapy of prostate cancer

In imaged-guided radiation therapy (IGRT), target localization is usually done with rigid-body registration based on anatomy matching. Problems arise when the target volume can only be matched partially due to inter-fractional organ motion and deformation, resulting in deteriorated target coverage and critical structure sparing. A new target localization method is investigated in which the treatment target volume is aligned with the prescription isodose surface. Our study included 15 prostate patients previously treated with intensity-modulated radiation therapy (IMRT). Patient setup and target localization were performed using a CT-on-rails system before and after the IMRT treatment. IMRT plans were generated on the original simulation CTs (15) and the same MUs and leaf sequences were used to compute the dose distributions on post-treatment CTs (98) with the isocenter adjustments based on either anatomical structure matching or prescription isodose surface alignment. When patients were aligned with the traditional anatomy matching method, the dose to 95% of the CTV, D95, received 74.0 – 77.6 Gy and the minimum CTV dose, Dmin, was 61.9 – 71.6 Gy, respectively, in the cumulative dose distributions. The rectal dose-volume constraints were violated in 35.7% of the treatment fractions. When patients were aligned using the new localization method, the dose to 95% of the CTV, D95, received 74.0 – 78.2 Gy and the minimum CTV dose, Dmin, was 68.4 – 71.6 Gy, respectively, in the cumulative dose distributions. The rectal dose-volume constraints were violated in 17.3% of the treatment fractions. Traditional IGRT target localization based on anatomy matching is effective for population-based PTV margins but not ideal for those patients with large inter-fractional prostate rotation/deformation due to large rectal and bladder volume variation. The new method using the prescription isodose surface to align the target volume could improve the target coverage and rectal sparing for these patients, which can be implemented clinically to improve target dose delivery accuracy.

Benchmarking a New Circular Cone-based Radiosurgery System against Clinically Tested Radiosurgery System on the same Novel Digital Linear Accelerator Platform.

To examine the dosimetric characteristics of circular cones, the accuracy of dose modeling and overall treatment delivery of two radiosurgery systems integrated on a linear accelerator (Linac). The dosimetric characteristics of circular cones (4-17.5 mm) from Varian (VC) and BrainLAB (BLC) were measured for 6 MV flattening filter free beam from Edge linac using stereotactic field diode and 0.65 cc ionization chamber following established protocols. The Eclipse and iPlan modeled dose distribution for VCs and BLCs were validated with EBT3-film measurement. End-to-end tests were performed using stereotactic phantom having PTW 60008 diode connected to a Dose-1 electrometer. The depth at dose maximum, TRP2010 and dose at 10cm depth of the same size VC and BLC agree within ± 0.7 mm, ± 0.71% and ± 0.81% respectively. Full width at half maximum (FWHM) of any cone beyond 15 mm depth increases at 1% of nominal cone size per 10 mm depth. The penumbra of 4mm and 17.5mm VC at 15 mm depth was 1.1 mm and 1.50 mm. At 300 mm depth, penumbra increased by around 0.4 mm for 4 mm cone and up to 1 mm for cone size ≥12.5 mm. The VCs penumbra values were within ±1mm of the corresponding BLCs. Scatter factors for VCs varies from 0.609 to 0.841 and were within ± 1.0% of corresponding values of BLCs. Agreement between the Eclipse and iPlan computed dose fluence and the EBT3-film measured dose fluence was >98% (γ: 1%@1 mm), and the absolute dose difference was ≤ 2.2%, except for the 4 mm cone in which it was >96% and ≤4.83%. Target localization using cone-beam computed tomography was accurate within ± 0.8 mm and ± 0.3° in translation and rotation. The end-to-end dose delivery accuracy for both radiosurgery systems was within ± 3.62%. The dosimetric characteristics of Varian and BLC cones of same diameter was comparable. Both Eclipse and iPlan cone planning system modeled dose fluences agree well with the EBT3 film measurement. The end-to-end tests revealed an excellent target localization accuracy of Edge linac with satisfactory and comparable absolute dose agreement between Varian and BLC radiosurgery systems and hence these can be interchanged on edge linac.

Инновации в лучевой терапии при лечении рака предстательной железы: улучшение результатов и минимизация побочных эффектов

Prostate cancer is one of the most common oncological diseases affecting men and causing an increase in the mortality rate among men worldwide. Russia has also seen a significant increase in morbidity and mortality in recent years. Currently, there is no absolutely effective method of treating prostate cancer. It is necessary to search for new economically justified methods with minor side effects or without them. The purpose of this article is to compare the methods of radiation therapy, to determine the advantages of innovative methods improving results and minimizing side effects in the treatment of patients with prostate cancer. We reviewed the current state of remote radiotherapy (EBRT/DLT) in high-risk cases, including the use of androgen deprivation therapy (ADT/ADT), the role of hypofractionation and stereotactic radiotherapy (SBRT/STLT), new data on combination therapy. An analysis of publications has shown the feasibility of combining long-term ADT and remote radiotherapy in patients with high-risk prostate cancer for maximum disease control and increased overall survival compared with treatment without this combination. Randomized data suggest that increasing the dose with LDR brachytherapy may be more effective than increasing the dose with EBRT alone. Over the past decade, advances in technology, imaging capabilities, and improved radiobiological understanding have profoundly changed radiation therapy for prostate cancer, allowing for increased dose and widespread introduction of hypofractionation. In addition, the integration of magnetic resonance imaging (MRI) and improved physical accuracy of dose delivery gave impetus to additional targeting of intra-static tumor lesions previously independent of the traditional concept of determining the target of radiation therapy.