Development of a 3D optical scanner for evaluating patient-specific dose distributions

PurposeThis paper describes the hardware and software characteristics of a 3D optical scanner (P3DS) developed in-house. The P3DS consists of an LED light source, diffuse screen, step motor, CCD camera, and scanner management software with 3D reconstructed software.Materials and methodWe performed optical simulation, 2D and 3D reconstruction image testing, and pre-clinical testing for the P3DS. We developed the optical scanner with three key characteristics in mind. First, we developed a continuous scanning method to expand possible clinical applications. Second, we manufactured a collimator to improve image quality by reducing scattering from the light source. Third, we developed an optical scanner with changeable camera positioning to enable acquisition of optimal images according to the size of the gel dosimeter.ResultsWe confirmed ray-tracing in P3DS with optic simulation and found that 2D projection and 3D reconstructed images were qualitatively similar to the phantom images. For pre-clinical tests, the dose distribution and profile showed good agreement among RTP, optical CT, and external beam radiotherapy film data for the axial and coronal views. The P3DS has shown that it can scan and reconstruct for evaluation of the gel dosimeter within 1 min. We confirmed that the P3DS system is a useful tool for the measurement of 3D dose distributions for 3D radiation therapy QA. Further experiments are needed to investigate quantitative analysis for 3D dose distribution.     

A software platform for statistical evaluation of patient respiratory patterns in radiation therapy

AimThe aim of this work was to design and evaluate a software tool for analysis of a patient’s respiration, with the goal of optimizing the effectiveness of motion management techniques during radiotherapy imaging and treatment.Materials and methodsA software tool which analyses patient respiratory data files (.vxp files) created by the Varian Real-Time Position Management System (RPM) was developed to analyse patient respiratory data. The software, called RespAnalysis, was created in MATLAB and provides four modules, one each for determining respiration characteristics, providing breathing coaching (biofeedback training), comparing pre and post-training characteristics and performing a fraction-by-fraction assessment. The modules analyse respiratory traces to determine signal characteristics and specifically use a Sample Entropy algorithm as the key means to quantify breathing irregularity. Simulated respiratory signals, as well as 91 patient RPM traces were analysed with RespAnalysis to test the viability of using the Sample Entropy for predicting breathing regularity.ResultsRetrospective assessment of patient data demonstrated that the Sample Entropy metric was a predictor of periodic irregularity in respiration data, however, it was found to be insensitive to amplitude variation. Additional waveform statistics assessing the distribution of signal amplitudes over time coupled with Sample Entropy method were found to be useful in assessing breathing regularity.ConclusionsThe RespAnalysis software tool presented in this work uses the Sample Entropy method to analyse patient respiratory data recorded for motion management purposes in radiation therapy. This is applicable during treatment simulation and during subsequent treatment fractions, providing a way to quantify breathing irregularity, as well as assess the need for breathing coaching. It was demonstrated that the Sample Entropy metric was correlated to the irregularity of the patient’s respiratory motion in terms of periodicity, whilst other metrics, such as percentage deviation of inhale/exhale peak positions provided insight into respiratory amplitude regularity.     

Sensitivity of the IQM and MatriXX detectors in megavolt photon beams

AimThis study focused on evaluating the sensitivity of integral quality monitoring (IQM^®) system and MatriXX detectors. These two detectors are recommended for radiotherapy pre-treatment quality assurance (QA).BackgroundIQM is a large wedged-shaped ionisation chamber mounted to the linear accelerator (linac) head in practice. MatriXX consists of an array of ionisation chambers also attached to the linac head.Materials and methodsIn this study, the dosimetric performance and sensitivity of MatriXX and IQM detectors were evaluated using the following characteristics: reproducibility, linearity, error detection capability and three-dimensional conformal radiotherapy (3D-CRT) plans of the head and neck, thorax and pelvic regions.ResultsThis study indicates that the signal responses of the large ionisation chamber device (IQM) and the small pixel array of ionisation chambers device (MatriXX) are reproducible, linear and sensitive to MLC positional errors, backup jaw positional errors and dose errors. The local percentage differences for dose errors of 1%, 2%, and 3% were, respectively, within 0.35–8.23%, 0.78–16.21%, and 1.10–24.41% for the IQM device. While for the MatriXX detector, the ranges were between 0.24–3.19, 0.57–6.43 and 0.81–12.95, respectively. Since IQM is essentially a double wedge-shaped large ionisation chamber, its reproducibility and detection capability are competitive to that of MatriXX. In addition, the sensitivity of the two QA systems increases with an increase in escalation percentage, and the signal responses are patient plan specific.ConclusionsThe two detectors response signals have good correlations and they are accurate for pre-treatment QA. Statistically, (P < 0.05) there is a significant difference between the IQM and MatriXX response to dose errors.     

Field output factors for small fields: A large multicentre study

PurposeThe determination of output factors in small field dosimetry is a crucial point, especially when implementing stereotactic radiotherapy (SRT). Herein, a working group of the French medical physicist society (SFPM) was created to collect small field output factors. The objective was to gather and disseminate information on small field output factors based on different detectors for various clinical SRT equipment and measurement configurations.MethodParticipants were surveyed for information about their SRT equipment, including the type of linear particle accelerator (linac), collimator settings, measurement conditions for the output factors and the detectors used. Participants had to report both the ratio of detector readings and the correction factors applied as described in the IAEA TRS-483 code of practice for nominal field sizes smaller or equal to 3 cm. Mean field output factors and their associated standard deviations were calculated when data from at least 3 linacs were available.Results23 centres were enrolled in the project. Standard deviations of the mean field output factors were systematically smaller than 1.5% for field sizes larger or equal to 1 cm and reached 5% for the smallest field size (0.5 cm). Deviations with published data were smaller than 2% except for the 0.5 cm circular fixed aperture collimator of the CyberKnife where it reached 3.5%.ConclusionThese field output factor values obtained via a large multicentre study can be considered as an external cross verification for any radiotherapy centre starting a SRT program and should help minimize systematic errors when determining small field output factors.     

The feasibility of an approximate irregular field dose distribution simulation program applied to a respiratory motion compensation system

PurposeThis study optimized our previously proposed simulation program for the approximate irregular field dose distribution (SPAD) and applied it to a respiratory motion compensation system (RMCS) and respiratory motion simulation system (RMSS). The main purpose was to rapidly analyze the two-dimensional dose distribution and evaluate the compensation effect of the RMCS during radiotherapy.MethodsThis study modified the SPAD to improve the rapid analysis of the dose distribution. In the experimental setup, four different respiratory signal patterns were input to the RMSS for actuation, and an ultrasound image tracking algorithm was used to capture the real-time respiratory displacement, which was input to the RMCS for actuation. A linear accelerator simultaneously irradiated the EBT3 film. The gamma passing rate was used to verify the dose similarity between the EBT3 film and the SPAD, and conformity index (CI) and compensation rate (CR) were used to quantify the compensation effect.ResultsThe Gamma passing rates were 70.48–81.39% (2%/2mm) and 88.23–96.23% (5%/3mm) for various collimator opening patterns. However, the passing rates of the SPAD and EBT3 film ranged from 61.85% to 99.85% at each treatment time point. Under the four different respiratory signal patterns, CR ranged between 21% and 75%. After compensation, the CI for 85%, 90%, and 95% isodose constraints were 0.78, 0.57, and 0.12, respectively.ConclusionsThis study has demonstrated that the dose change during each stage of the treatment process can be analyzed rapidly using the improved SPAD. After compensation, applying the RMCS can reduce the treatment errors caused by respiratory movements.     

Design and development of a dedicated portable gamma camera system for intra-operative imaging

PurposeWe developed a high performance portable gamma camera platform dedicated to identification of sentinel lymph nodes (SLNs) and radio-guided surgery for cancer patients. In this work, we present the performance characteristics of SURGEOSIGHT-I, the first version of this platform that can intra-operatively provide high-resolution images of the surveyed areas.MethodsAt the heart of this camera, there is a 43 × 43 array of pixelated sodium-activated cesium iodide (CsI(Na)) scintillation crystal with 1 × 1 mm² pixel size and 5 mm thickness coupled to a Hamamatsu H8500 flat-panel multi-anode (64 channels) photomultiplier tube. The probe is equipped with a hexagonal parallel-hole lead collimator with 1.2 mm holes. The detector, collimator, and the associated front-end electronics are encapsulated in a common housing referred to as head.ResultsOur results show a count rate of ∼41 kcps for 20% count loss. The extrinsic energy resolution was measured as 20.6% at 140 keV. The spatial resolution and the sensitivity of the system on the collimator surface was measured as 2.2 mm and 142 cps/MBq, respectively. In addition, the integral and differential uniformity, after uniformity correction, in useful field-of-view (UFOV) were measured 4.5% and 4.6%, respectively.ConclusionsThis system can be used for a number of clinical applications including SLN biopsy and radiopharmaceutical-guided surgery.     

A Simple and Effective Approach for Digitization of the CTG Signals from CTG Traces

ObjectivesCardiotocography (CTG) is a useful tool for monitoring of the fetal heart rate (FHR) and uterine contractions (UC) during the intrauterine life. Generally, CTG is provided on a printed paper which is hard to save for future evaluations. So, digitization of CTG signals is in demand for future evaluations. A straightforward approach for digitization of the CTG signals is to apply image processing on the scanned CTG printed papers.Material and methodsIn this paper, an automatic procedure is proposed for digitization of the CTG signals. The proposed approach consists of four main stages such as pre-processing, image segmentation, signal extraction and signal calibration. The pre-processing stage covers median filtering and contrasts limited adaptive histogram equalization (CLAHE) for noise removal and contrast enhancement. Image segmentation is used to binarize the CTG images for signal determination using the Otsu's thresholding algorithm. The signal extraction is carried out by a two-stepped algorithm. The acquired CTG signals are then calibrated for obtaining the final CTG signals. We use the correlation coefficient to measure the similarity between the automatically digitized CTG signals and original signals.ResultsIn experimental works, an open-access database, which contains 552 CTG recordings, is employed. The results are quite impressive. According to the obtained results, the average correlation coefficients for FHR and UC signals are 0.9715 ± 0.0168 and 0.9717 ± 0.0465, respectively.ConclusionsThe obtained results show that the proposed method is quite efficient in digitization of the CTG signals. In future works, this tool will be used to digitize the recordings belonging to the antepartum period collected from the obstetrics clinics in Medical Park Hospital in Elazığ, Turkey.     

Generation of clinical 177Lu SPECT/CT images based on Monte Carlo simulation with GATE

PurposePatient-specific dosimetry in MRT relies on quantitative imaging, pharmacokinetic assessment and absorbed dose calculation. The DosiTest project was initiated to evaluate the uncertainties associated with each step of the clinical dosimetry workflow through a virtual multicentric clinical trial. This work presents the generation of simulated clinical SPECT datasets based on GATE Monte Carlo modelling with its corresponding experimental CT image, which can subsequently be processed by commercial image workstations.MethodsThis study considers a therapy cycle of 6.85 GBq ¹⁷⁷Lu-labelled DOTATATE derived from an IAEA-Coordinated Research Project (E23005) on “Dosimetry in Radiopharmaceutical therapy for personalised patient treatment”. Patient images were acquired on a GE Infinia-Hawkeye 4 gamma camera using a medium energy (ME) collimator. Simulated SPECT projections were generated based on experimental time points and validated against experimental SPECT projections using flattened profiles and gamma index. The simulated projections were then incorporated into the patient SPECT/CT DICOM envelopes for processing and their reconstruction within a commercial image workstation.ResultsGamma index passing rate (2% − 1 pixel criteria) between 95 and 98% and average gamma between 0.28 and 0.35 among different time points revealed high similarity between simulated and experimental images. Image reconstruction of the simulated projections was successful on HERMES and Xeleris workstations, a major step forward for the initiation of a multicentric virtual clinical dosimetry trial based on simulated SPECT/CT images.ConclusionsRealistic ¹⁷⁷Lu patient SPECT projections were generated in GATE. These modelled datasets will be circulated to different clinical departments to perform dosimetry in order to assess the uncertainties in the entire dosimetric chain.     

Technical note: Unexpected external markers artifact in 3D k-space based parallel imaging turbo spin-echo magnetic resonance imaging

PurposeMRI for radiotherapy planning requires spatial referencing using immobilization devices and markers. Clinical images of a difficult-to-interpret artifact are presented, resembling a metastasis, which occurs when combining CAIPIRINHA k-space-based parallel imaging (PI), 3D distortion correction, and external markers.MethodsA 3D variable flip angle Turbo Spin Echo sequence was used on a 1.5 T and 3 T MRI using flexible and head and neck coils. Two types of markers were tested: Liquimark LM1 and Spee-D-Mark. A silicone oil phantom was used that represents low signal intensity, such as gray matter. 3D Fourier transforms were also used to show the issue’s origin.ResultsThe markers can appear in an unexpected region of a patient, not in the same original or reconstructed slice nor in a rectilinear direction in a slice, especially when using CAIPIRINHA acceleration with 3D distortion correction. The probability of occurrence was respectively 13% and 80% for distances of <=2 mm and >2 mm between marker and patient, for example when using thermoplastic masks. Clinical cases are shown where this semi-randomly occurring artifact appears post contrast only, and thus can be interpreted as metastases. The artifact did not appear when using compressed sensing acceleration.ConclusionMarkers used for radiotherapy MRI application can introduce additional artifacts that can be interpreted as metastases. However, other high signal intensity structures on the surface of a patient, such as the ear, can lead to an equivalent error.     

Automatic tracking of gold seed markers from CBCT image projections in lung and prostate radiotherapy

PurposeTo construct a method and software to track gold seed implants in prostate and lung patients undergoing radiotherapy using CBCT image projections.MethodsA mathematical model was developed in the MatLab (Mathworks, Natick, USA) environment which uses a combination of discreet cosine transforms and filtering to enhance several edge detection methods for identifying and tracking gold seed fiducial markers in images obtained from Varian (Varian Medical Systems, Palo Alto, USA) and Elekta (Kungstensgatan, Sweden) CBCT projections.ResultsOrgan motion was captured for 16 prostate patients and 1 lung patient.ConclusionImage enhancement and edge detection is capable of automatically tracking markers for up to 98% (Varian) and 79% (Elekta) of CBCT projections for prostate and lung markers however inclusion of excessive bony anatomy (LT and RT LAT) inhibit the ability of the model to accurate determine marker location.     

Simulating the approximate irregular field dose distribution in radiotherapy using an ultrasound tracking technique

PurposeThis study used an ultrasound image tracking algorithm (UITA) in combination with a proposed simulation program for the approximate irregular field dose distribution (SPAD) to assess the feasibility of performing dose distribution simulations for two-dimensional radiotherapy.MethodsThis study created five different types of multileaf collimator openings, and applied a SPAD to analyze the matrix position parameters for each regular field to generate a static program-simulation dose distribution map (PDDM), whose similarity was then compared with a static radiochromic film experimental-measurement dose distribution map (EDDM). A two-dimensional respiration motion simulation system (RMSS) was used to reproduce the respiration motion, and the UITA was used to capture the respiration signals. Respiration signals were input to the SPAD to generate two dynamic PDDMs, which were compared for similarity with the dynamic EDDM.ResultsIn order to verify the dose distribution between different dose measurement techniques, the gamma passing rate with 2%/2 mm criterion was used for the EDDM and PDDM, the passing rates were between 94.31% and 99.71% in the static field analyses, and between 84.45% and 96.09% for simulations with the UITA signal input and between 89.35% and 97.78% for simulations with the original signal input in the dynamic field analyses.ConclusionsStatic and dynamic dose distribution maps can be simulated based on the proposed matrix position parameters of various fields and by using the UITA to track respiration signals during radiation therapy. The present findings indicate that it is possible to develop a reusable and time-saving dose distribution measurement tool.     

Coded aperture nuclear scintigraphy: a novel small animal imaging technique

We introduce and demonstrate the utility of coded aperture (CA) nuclear scintigraphy for imaging small animals. CA imaging uses multiple pinholes in a carefully designed mask pattern, mounted on a conventional gamma camera. System performance was assessed using point sources and phantoms, while several animal experiments were performed to test the usefulness of the imaging system in vivo, with commonly used radiopharmaceuticals. The sensitivity of the CA system for 99mTc was 4.2 x 10(3) cps/Bq (9400 cpm/microCi), compared to 4.4 x 10(4) cps/Bq (990 cpm/microCi) for a conventional collimator system. The system resolution was 1.7 mm, as compared to 4-6 mm for the conventional imaging system (using a high-sensitivity low-energy collimator). Animal imaging demonstrated artifact-free imaging with superior resolution and image quality compared to conventional collimator images in several mouse and rat models. We conclude that: (a) CA imaging is a useful nuclear imaging technique for small animal imaging. The advantage in signal-to-noise can be traded to achieve higher resolution, decreased dose or reduced imaging time. (b) CA imaging works best for images where activity is concentrated in small volumes; a low count outline may be better demonstrated using conventional collimator imaging. Thus, CA imaging should be viewed as a technique to complement rather than replace traditional nuclear imaging methods. (c) CA hardware and software can be readily adapted to existing gamma cameras, making their implementation a relatively inexpensive retrofit to most systems.     

Classification of Motor Imagery EEG Based on Time-Domain and Frequency-Domain Dual-Stream Convolutional Neural Network

Background and objectiveAn important task of the brain-computer interface (BCI) of motor imagery is to extract effective time-domain features, frequency-domain features or time-frequency domain features from the raw electroencephalogram (EEG) signals for classification of motor imagery. However, choosing an appropriate method to combine time domain and frequency domain features to improve the performance of motor imagery recognition is still a research hotspot.MethodsIn order to fully extract and utilize the time-domain and frequency-domain features of EEG in classification tasks, this paper proposed a novel dual-stream convolutional neural network (DCNN), which can use time domain signal and frequency domain signal as the inputs, and the extracted time-domain features and frequency-domain features are fused by linear weighting for classification training. Furthermore, the weight can be learned by the DCNN automatically.ResultsThe experiments based on BCI competition II dataset III and BCI competition IV dataset 2a showed that the model proposed by this study has better performance than other conventional methods. The model used time-frequency signal as the inputs had better performance than the model only used time-domain signals or frequency-domain signals. The accuracy of classification was improved for each subject compared with the models only used one signals as the inputs.ConclusionsFurther analysis shown that the fusion weight of different subject is specifically, adjusting the weight coefficient automatically is helpful to improve the classification accuracy.     

Cost-effectiveness of the modifications in the quality assurance system in radiotherapy in the example of in-vivo dosimetry

PurposeTo present the methodology for the evaluation of cost-effectiveness of the quality assurance protocol modifications associated with increasing demands on accuracy and reliability in radiotherapy and to present results on cost-effectiveness of in-vivo dosimetry as the chosen example of a technical procedure.Material and methodsIn-vivo dosimetry was used as an example of a quality assurance procedure, whose modifications have an impact on several procedures in the QA system and thus on the cost of radiotherapy. An analysis of 6864 patients, treated between 2001 and 2005 for tumours in the head and neck, breast, pelvis, or lung, was performed. The quality of radiotherapy was expressed as the accuracy of dose delivery and the cost was estimated from labour, equipment and materials.ResultsModifications implemented in the quality assurance protocol have gradually improved the quality of irradiation. Mean deviations between measured and calculated doses, recorded for several groups of treatment sites, were reduced from ?1.5% to 0.5%, 3.4% to 1.4%, 3.9% to 0.1% and ?2.1% to 1.8% for head and neck, breast, pelvis and lung respectively. The standard deviations of the measured values decreased also consistently. Total monthly cost in radiotherapy (related to in-vivo dosimetry) increased from € 4376 to € 10,696 while the unitary cost of radiotherapy procedures remained at the same level. The predominant cost component of in-vivo dosimetry was labour, limited at first to physics staff and later extended to quality assurance personnel and technicians.ConclusionThe application of the presented methodology revealed cost-effectiveness relationships in tested technical procedures.     

Assessing good operating conditions for intraoperative imaging of melanoma sentinel nodes by a portable gamma camera

ObjectiveTo provide guidance for reliable identification of low-activity sentinel nodes in the setting of melanoma surgery using a commercial hand-held gamma camera.MethodsThe average uptake of ^99mTc nanocolloid by sentinel nodes was evaluated in 95 excised nodes using a Sentinella 102^® (Oncovision, Valencia, Spain) portable gamma camera. The device sensitivity was assessed for different source depths and collimator distances, imaging an 8-mm sphere filled with a known-activity solution of ^99mTc. Five nuclear medicine physicians were asked to identify the source at different activity levels and positions within the field of view. For each image the number of signal counts inside a circular region of interest (ROI) was measured, while the variability of ROI counts among operators was assessed. The number of counts providing a minimal, near-constant inter-operator variability was determined as a criterion for a consistent identification of the source. Either the minimum activity or the acquisition time needed to collect the appropriate statistics were then calculated.ResultsThe median SN uptake (0.5%) turned out to be compatible with values reported in the literature. The sensitivity of the compact gamma camera ranged from ∼25 cpm/kBq to ∼1 cpm/kBq. A total of 50 counts in the ROI circumscribing the lymph node-simulating sphere appeared to be a robust criterion for identification of the source.ConclusionsTen megabecquerels of injected activity at the time of surgery and one minute of acquisition allows reliable identification of sentinel nodes for collimator-to-source distances up to 10 cm.     

Quantitative evaluation of scintillation camera imaging characteristics of isotopes used in liver radioembolization

Background

Scintillation camera imaging is used for treatment planning and post-treatment dosimetry in liver radioembolization (RE). In yttrium-90 (90Y) RE, scintigraphic images of technetium-99m (99mTc) are used for treatment planning, while 90Y Bremsstrahlung images are used for post-treatment dosimetry. In holmium-166 (166Ho) RE, scintigraphic images of 166Ho can be used for both treatment planning and post-treatment dosimetry. The aim of this study is to quantitatively evaluate and compare the imaging characteristics of these three isotopes, in order that imaging protocols can be optimized and RE studies with varying isotopes can be compared.

Methodology/Principal Findings

Phantom experiments were performed in line with NEMA guidelines to assess the spatial resolution, sensitivity, count rate linearity, and contrast recovery of 99mTc, 90Y and 166Ho. In addition, Monte Carlo simulations were performed to obtain detailed information about the history of detected photons. The results showed that the use of a broad energy window and the high-energy collimator gave optimal combination of sensitivity, spatial resolution, and primary photon fraction for 90Y Bremsstrahlung imaging, although differences with the medium-energy collimator were small. For 166Ho, the high-energy collimator also slightly outperformed the medium-energy collimator. In comparison with 99mTc, the image quality of both 90Y and 166Ho is degraded by a lower spatial resolution, a lower sensitivity, and larger scatter and collimator penetration fractions.

Conclusions/Significance

The quantitative evaluation of the scintillation camera characteristics presented in this study helps to optimize acquisition parameters and supports future analysis of clinical comparisons between RE studies.     

A new isocentric technique for exact geometric matching in the radiotherapy of the breast and ipsilateral supraclavicular fossa using dual asymmetric jaws

BackgroundIn some clinical situations breast or chest wall radiotherapy for cancer is given in association with supraclavicular fossa irradiation. Often the treatment is delivered by two tangential fields to the breast or chest wall and an anterior field that irradiates the supraclavicular region. The tissue between the breast or chest wall and the supraclavicular region may be under or overdosed, because of the junction between the two tangential fields and the anterior field.PurposeTo present a new isocentric technique for exact geometric matching between the two tangential fields and the anterior field.MethodsPatients are positioned with both arms raised. Using three-dimensional trigonometry, two half-fields, with isocenter between the breast and the supraclavicular region, are easily matched. The tangential fields have a collimator rotation to protect the lung without additional shielding. The correct gantry, collimator and couch positions are defined for the anterior field to match the tangential fields.ConclusionsA general formula for exact geometric matching in radiotherapy of the breast and supraclavicular fossa is presented. The method does not require additional shielding to eliminate divergence other than the four independent jaws. The result is simple to implement in modern delivery facilities.     

99mTc thyroid imaging system using multiple imaging plates

A system for taking static thyroid ^99mTc images was devised by using multiple imaging plates (IPs) and a low-energy high resolution collimator. System spatial resolution of the IP systems and the gamma camera was determined by referring to standards set by the National Electrical Manufacturers Association. Sensitivity was represented by using lower detection limits (LDLs). The sensitivity and resolution of IP systems using 16 IP probes connecting two collimators and 9 IPs were determined by using a 20 ml thyroid phantom, and compared with the sensitivity of gamma cameras. The sensitivity of the IP systems increased in proportion to the number of IPs. The sensitivity and resolution of a probe using 6 IPs and a high resolution collimator were equivalent to or superior to the gamma camera for taking static thyroid ^99mTc images. IP systems can be applied clinically as mobile static nuclear imaging devices. The performance of IP systems should be thoroughly investigated for combinations of various collimators and the number of IPs in order to verify their efficacy for imaging all organs.     

Radiotherapy for cervical cancer: Chilean consensus of the Society of Radiation Oncology

BackgroundCervical cancer is a public health problem in Latin America. Radiotherapy plays a fundamental role both as definitive or adjuvant treatment. There are important intra and inter-country differences regarding access and availability of radiotherapy facilities in this region. The aim of a study was to standardize the basic clinical and technical criteria for the radiation treatment of patients with CC in Chile and provide a guide for Latin American Radiation Oncologists.Materials and methodsForty-one expert radiation oncologists from the Chilean Radiation Oncology Society made a consensus using the Delphi methodology.ResultsThere was a high degree of agreement for each of the recommendations. Those with the lowest percentage were related to the definition of the conformal 3D technique as the standard for definitive external radiotherapy (81%) and the criteria for extended nodal irradiation (85%).ConclusionsThese recommendations present an updated guide for radiotherapy treatment of patients with cervical cancer for Latin America. Those should be implemented according to local resources of each institution.     

Recent advances in clinical studies of selenium supplementation in radiotherapy

BackgroundRadiotherapy is one of the most important and common therapies for cancer patients. Selenium has been shown to be capable of reducing the side effects of radiotherapy because selenoproteins have anti-oxidative functions against reactive oxygen species that are induced by the radiation. They also function in DNA-repair and cytokine control.PurposeWe explored the benefits and risks of selenium supplementation in radiotherapy in our previous review to establish guidelines. In the current study, we expanded the search to cover recent advances in clinical studies of selenium supplementation in radiotherapy.MethodsWe conducted an initial screening in the PubMed using the MeSH terms and keywords “selenium”, “radiation”, “therapy”, and “radiotherapy” using the same methodology applied in our previous review. We identified 121 articles published between January 2013 and December 2019. We then identified eight articles (six studies) on selenium and radiotherapy by excluding 113 articles.ResultsIn selenium supplementation studies, selenium doses of 300−500 μg/day with duration of 10 days to 6 months were used. Selenium supplementation improved the selenium nutritional conditions of the patients and reduced the side effects of radiotherapy. Selenium supplementation did not reduce the effectiveness of radiotherapy, and no toxicities were reported.ConclusionThe results of our previous and current reviews showed that selenium supplementation offers specific benefits for several cancer types treated with radiotherapy. Here, we suggest a new guideline for selenium supplementation in radiotherapy. We recommend determining the selenium status of the patients before radiotherapy, and in cases of deficiency (<100 μg/L serum selenium level), selenium supplement can be beneficial.