Forecasting patient-specific dosimetric benefit from daily online adaptive radiotherapy for cervical cancer.

Objective. Adaptive Radiotherapy (ART) is an emerging technique for treating cancer patients which facilitates higher delivery accuracy and has the potential to reduce toxicity. However, ART is also resource-intensive, Requiring extra human and machine time compared to standard treatment methods. In this analysis, we sought to predict the subset of node-negative cervical cancer patients with the greatest benefit from ART, so resources might be properly allocated to the highest-yield patients.Approach. CT images, initial plan data, and on-treatment Cone-Beam CT (CBCT) images for 20 retrospective cervical cancer patients were used to simulate doses from daily non-adaptive and adaptive techniques. We evaluated the coefficient of determination (R2) between dose and volume metrics from initial treatment plans and the dosimetric benefits to theBowelV40Gy,BowelV45Gy,BladderDmean,andRectumDmeanfrom adaptive radiotherapy using reduced 3 mm or 5 mm CTV-to-PTV margins. The LASSO technique was used to identify the most predictive metrics forBowelV40Gy.The three highest performing metrics were used to build multivariate models with leave-one-out validation forBowelV40Gy.Main results. Patients with higher initial bowel doses were correlated with the largest decreases in BowelV40Gyfrom daily adaptation (linear best fit R2= 0.77 for a 3 mm PTV margin and R2= 0.8 for a 5 mm PTV margin). Other metrics had intermediate or no correlation. Selected covariates for the multivariate model were differences in the initialBowelV40GyandBladderDmeanusing standard versus reduced margins and the initial bladder volume. Leave-one-out validation had an R2of 0.66 between predicted and true adaptiveBowelV40Gybenefits for both margins.Significance. The resulting models could be used to prospectively triage cervical cancer patients on or off daily adaptation to optimally manage clinical resources. Additionally, this work presents a critical foundation for predicting benefits from daily adaptation that can be extended to other patient cohorts.

Dosimetric and feasibility evaluation of a CBCT-based daily adaptive radiotherapy protocol for locally advanced cervical cancer.

PURPOSE: Evaluate a cone-beam computed tomography (CBCT)-based daily adaptive platform in cervical cancer for multiple endpoints: (1) physics contouring accuracy of daily CTVs, (2) CTV coverage with adapted plans and reduced PTV margins versus non-adapted plans with standard-of-care (SOC) margins, (3) dosimetric improvements to CTV and organs-at-risk (OARs), and (4) on-couch time. METHODS AND MATERIALS: Using a Varian Ethos™ emulator and KV-CBCT scans, we simulated the doses 15 retrospective cervical cancer patients would have received with/without online adaptation for five fractions. We compared contours and doses from SOC plans (5-15 mm CTV-to-PTV margins) to adapted plans (3 mm margins). Auto-segmented CTVs and OARs were reviewed and edited by trained physicists. Physics-edited targets were evaluated by an oncologist. Time spent reviewing and editing auto-segmented structures was recorded. Metrics from the CTV (D99%), bowel (V45Gy, V40Gy), bladder (D50%), and rectum (D50%) were compared. RESULTS: The physician approved the physics-edited CTVs for 55/75 fractions; 16/75 required reductions, and 4/75 required CTV expansions. CTVs were encapsulated by unadapted, SOC PTVs for 56/75 (72%) fractions-representative of current clinical practice. CTVs were completely covered by adapted 3 mm PTVs for 71/75 (94.6%) fractions. CTV D99% values for adapted plans were comparable to non-adapted SOC plans (average difference of -0.9%), while all OAR metrics improved with adaptation. Specifically, bowel V45Gy and V40Gy decreased on average by 87.6 and 109.4 cc, while bladder and rectum D50% decreased by 37.7% and 35.8%, respectively. The time required for contouring and calculating an adaptive plan for 65/75 fractions was less than 20 min (range: 1-29 min). CONCLUSIONS: Improved dose metrics with daily adaption could translate to reduced toxicity while maintaining tumor control. Training physicists to perform contouring edits could minimize the time physicians are required at adaptive sessions improving clinical efficiency. All emulated adaptive sessions were completed within 30 min however extra time will be required for patient setup, image acquisition, and treatment delivery.

Clinical commissioning of an adaptive radiotherapy platform: Results and recommendations.

Online adaptive radiotherapy platforms present a unique challenge for commissioning as guidance is lacking and specialized adaptive equipment, such as deformable phantoms, are rare. We designed a novel adaptive commissioning process consisting of end-to-end tests using standard clinical resources. These tests were designed to simulate anatomical changes regularly observed at patient treatments. The test results will inform users of the magnitude of uncertainty from on-treatment changes during the adaptive workflow and the limitations of their systems. We implemented these tests for the cone-beam computed tomography (CT)-based Varian Ethos online adaptive platform. Many adaptive platforms perform online dose calculation on a synthetic CT (synCT). To assess the impact of the synCT generation and online dose calculation on dosimetric accuracy, we conducted end-to-end tests using commonly available equipment: a CIRS IMRT Thorax phantom, PinPoint ionization chamber, Gafchromic film, and bolus. Four clinical scenarios were evaluated: weight gain and weight loss were simulated by adding and removing bolus, internal target shifts were simulated by editing the CTV during the adaptive workflow to displace it, and changes in gas were simulated by removing and reinserting rods in varying phantom locations. The effect of overriding gas pockets during planning was also assessed. All point dose measurements agreed within 2.7% of the calculated dose, with one exception: a scenario simulating gas present in the planning CT, not overridden during planning, and dissipating at treatment. Relative film measurements passed gamma analysis (3%/3 mm criteria) for all scenarios. Our process validated the Ethos dose calculation for online adapted treatment plans. Based on our results, we made several recommendations for our clinical adaptive workflow. This commissioning process used commonly available equipment and, therefore, can be applied in other clinics for their respective online adaptive platforms.

The current status and shortcomings of stereotactic radiosurgery.

Background: Stereotactic radiosurgery (SRS) is a common treatment for intracranial lesions. This work explores the state of SRS treatment delivery to characterize current treatment accuracy based on treatment parameters. Methods: NCI clinical trials involving SRS rely on an end-to-end treatment delivery on a patient surrogate (credentialing phantom) from the Imaging and Radiation Oncology Core (IROC) to test their treatment accuracy. The results of 1072 SRS phantom irradiations between 2012 and 2020 were retrospectively analyzed. Univariate analysis and random forest models were used to associate irradiation conditions with phantom performance. The following categories were evaluated in terms of how they predicted outcomes: year of irradiation, TPS algorithm, machine model, energy, and delivered field size. Results: Overall, only 84.6% of irradiations have met the IROC/NCI acceptability criteria. Pass rate has remained constant over time, while dose calculation accuracy has slightly improved. Dose calculation algorithm (P < .001), collimator (P = .024), and field size (P < .001) were statistically significant predictors of pass/fail. Specifically, pencil beam algorithms and cone collimators were more likely to be associated with failing phantom results. Random forest modeling identified the size of the field as the most important factor for passing or failing followed by algorithm. Conclusion: Constant throughout this retrospective study, approximately 15% of institutions fail to meet IROC/NCI standards for SRS treatment. In current clinical practice, this is particularly associated with smaller fields that yielded less accurate results. There is ongoing need to improve small field dosimetry, beam modeling, and QA to ensure high treatment quality, patient safety, and optimal clinical trials.

Evaluation of image quality of a novel computed tomography metal artifact management technique on an anthropomorphic head and neck phantom.

BACKGROUND AND PURPOSE: Artefacts caused by dental amalgam implants present a common challenge in computed tomography (CT) and therefore treatment planning dose calculations. The goal was to perform a quantitative image quality analysis of our Artifact Management for Proton Planning (AMPP) algorithm which used gantry tilts for managing metal artefacts on Head and Neck (HN) CT scans and major vendors' commercial approaches. MATERIALS AND METHODS: Metal artefact reduction (MAR) algorithms were evaluated using an anthropomorphic phantom with a removable jaw for the acquisition of images with and without (baseline) metal artifacts. AMPP made use of two angled CT scans to generate one artifact-reduced image set. The MAR algorithms from four vendors were applied to the images with artefacts and the analysis was performed with respective baselines. Planar HU difference maps and volumetric HU differences were analyzed. RESULTS: AMPP algorithm outperformed all vendors' commercial approaches in the elimination of artefacts in the oropharyngeal region, showing the lowest percent of pixels outside +- 20 HU criteria, 4%; whereas those in the MAR-corrected images ranged from 26% to 67%. In the region of interest within the affected slices, the commercial MAR algorithms showed inconsistent performance, whereas the AMPP algorithm performed consistently well throughout the phantom's posterior region. CONCLUSIONS: A novel MAR algorithm was evaluated and compared to four commercial algorithms using an anthropomorphic phantom. Unanimously, the analysis showed the AMPP algorithm outperformed vendors' commercial approaches, showing the potential to be broadly implemented, improve visualizations in patient anatomy and provide accurate HU information.

Dosimetric impact of commercial CT metal artifact reduction algorithms and a novel in-house algorithm for proton therapy of head and neck cancer.

PURPOSE: To compare the dosimetric impact of all major commercial vendors' metal artifact reduction (MAR) algorithms to one another, as well as to a novel in-house technique (AMPP) using an anthropomorphic head phantom. MATERIALS AND METHODS: The phantom was an Alderson phantom, modified to allow for artifact-filled and baseline (no artifacts) computed tomography (CT) scans using teeth capsules made with metal amalgams or bone-equivalent materials. It also included a cylindrical insert that was accessible from the bottom of the neck and designed to introduce soft tissue features into the phantom that were used in the analysis. The phantom was scanned with the metal teeth in place using each respective vendor's MAR algorithm: OMAR (Philips), iMAR (Siemens), SEMAR (Canon), and SmartMAR (GE); the AMPP algorithm was designed in-house. Uncorrected and baseline (bone-equivalent teeth) image sets were also acquired using a Siemens scanner. Proton spot scanning treatment plans were designed on the baseline image set for five targets in the phantom. Once optimized, the proton beams were copied onto the different artifact-corrected image sets, with no reoptimization of the beams' parameters, to evaluate dose distribution differences in the different MAR-corrected and -uncorrected image sets. Dose distribution differences were evaluated by comparing dose-volume histogram (DVH) metrics, including planning target volume D95 and clinical target volume D99 coverages, V100, D0.03cc, and heterogeneity indexes, along with a qualitative and water equivalent thickness (WET) analysis. RESULTS: Uncorrected CT metal artifacts and commercial MAR algorithms negatively impacted the proton dose distributions of all five target shapes and locations in an inconsistent manner, sometimes overdosing by as much as 11.1% (D0.03) or underdosing by as much as 11.7% (V100) the planning target volumes. The AMPP-corrected images, however, provided dose distributions that consistently agreed with the baseline dose distribution. The dosimetry results also suggest that the commercial MAR algorithms' performances varied more with target location and less with target shape. Once relocated further from the metal, the target showed dose distributions that agreed more with the baseline for all commercial solutions, improving the overdosing by as much as 6%, implying inadequate HU correction from commercial MAR algorithms. In comparison to the baseline, HU profile shapes were considerably altered by commercial algorithms and reference values showed differences that represent stopping power percentage differences of 2.7-10%. The AMPP algorithm plans showed the smallest WET differences with the baseline (0.06 cm on average), while the commercial image sets created differences that ranged from 0.11 to 0.54 cm. CONCLUSIONS: Computed tomography metal artifacts negatively impacted proton dose distributions on all five targets analyzed. The commercial MAR solutions performed inconsistently throughout all targets compared to the metal-free baseline. A lack of CTV coverage and an increased number of hotspots were observed throughout all commercial solutions. Dose distribution errors were related to the proximity to the artifacts, demonstrating the inability of commercial techniques to adequately correct severe artifacts. In contrast, AMPP consistently showed dose distributions that best matched the baseline, likely because it makes use of accurate HU information, as opposed to interpolated data like commercial algorithms.

Development of a stereoscopic CT metal artifact management algorithm using gantry angle tilts for head and neck patients.

Dental amalgams are a common source of artifacts in head and neck (HN) images. Commercial artifact reduction techniques have been offered, but are substantially ineffectual at reducing artifacts from dental amalgams, can produce additional artifacts, provide inaccurate HU information, or require extensive computation time, and thus offer limited clinically utility. The goal of this work was to define and validate a novel algorithm and provide a phantom-based testing as proof of principle. An initial clinical comparison to a vendor's current solution was also performed. The algorithm uses two-angled CT scans in order to generate a single image set with minimal artifacts posterior to the metal implants. The algorithm was evaluated using a phantom simulating a HN patient with dental fillings. Baseline (no artifacts) geometrical measurements of the phantom were taken in the anterior-posterior, left-right, and superior-inferior directions and compared to the metal-corrected images using our algorithm to evaluate possible distortion from application of the algorithm. Mean HU numbers were also compared between the baseline scan and corrected image sets. A similar analysis was performed on the vendor's algorithm for comparison. The algorithm developed in this work successfully preserved the image geometry and HU and corrected the CT metal artifacts in the region posterior to the metal. The average total distortion for all gantry angles in the AP, LR, and SI directions was 0.17, 0.12, and 0.14 mm, respectively. The HU measurements showed significant consistency throughout the different reconstructed images when compared to the baseline image sets. The vendor's algorithm also showed no geometrical distortion but performed inferiorly in the HU number analysis compared to our technique. Our novel metal artifact management algorithm, using CT gantry angle tilts, provides a promising technique for clinical management of metal artifacts from dental amalgam.

Independent recalculation outperforms traditional measurement-based IMRT QA methods in detecting unacceptable plans.

PURPOSE: To evaluate the performance of an independent recalculation and compare it against current measurement-based patient specific intensity-modulated radiation therapy (IMRT) quality assurance (QA) in predicting unacceptable phantom results as measured by the Imaging and Radiation Oncology Core (IROC). METHODS: When institutions irradiate the IROC head and neck IMRT phantom, they are also asked to submit their internal IMRT QA results. Separately from this, IROC has previously created reference beam models on the Mobius3D platform to independently recalculate phantom results based on the institution's DICOM plan data. The ability of the institutions' IMRT QA to predict the IROC phantom result was compared against the independent recalculation for 339 phantom results collected since 2012. This was done to determine the ability of these systems to detect failing phantom results (i.e., large errors) as well as poor phantom results (i.e., modest errors). Sensitivity and specificity were evaluated using common clinical thresholds, and receiver operator characteristic (ROC) curves were used to compare across different thresholds. RESULTS: Overall, based on common clinical criteria, the independent recalculation was 12 times more sensitive at detecting unacceptable (failing) IROC phantom results than clinical measurement-based IMRT QA. The recalculation was superior, in head-to-head comparison, to the EPID, ArcCheck, and MapCheck devices. The superiority of the recalculation vs these array-based measurements persisted under ROC analysis as the recalculation curve had a greater area under it and was always above that for these measurement devices. For detecting modest errors (poor phantom results rather than failing phantom results), neither the recalculation nor measurement-based IMRT QA performed well. CONCLUSIONS: A simple recalculation outperformed current measurement-based IMRT QA methods at detecting unacceptable plans. These findings highlight the value of an independent recalculation, and raise further questions about the current standard of measurement-based IMRT QA.

Radiation Planning Assistant - A Streamlined, Fully Automated Radiotherapy Treatment Planning System.

The Radiation Planning Assistant (RPA) is a system developed for the fully automated creation of radiotherapy treatment plans, including volume-modulated arc therapy (VMAT) plans for patients with head/neck cancer and 4-field box plans for patients with cervical cancer. It is a combination of specially developed in-house software that uses an application programming interface to communicate with a commercial radiotherapy treatment planning system. It also interfaces with a commercial secondary dose verification software. The necessary inputs to the system are a Treatment Plan Order, approved by the radiation oncologist, and a simulation computed tomography (CT) image, approved by the radiographer. The RPA then generates a complete radiotherapy treatment plan. For the cervical cancer treatment plans, no additional user intervention is necessary until the plan is complete. For head/neck treatment plans, after the normal tissue and some of the target structures are automatically delineated on the CT image, the radiation oncologist must review the contours, making edits if necessary. They also delineate the gross tumor volume. The RPA then completes the treatment planning process, creating a VMAT plan. Finally, the completed plan must be reviewed by qualified clinical staff.

An Anthropomorphic Head and Neck Quality Assurance Phantom for Credentialing of Intensity-Modulated Proton Therapy.

PURPOSE: To design and commission a head and neck (H&N) anthropomorphic phantom that the Imaging and Radiation Oncology Core Houston (IROC-H) can use to verify the quality of intensity-modulated proton therapy H&N treatments for institutions participating in National Cancer Institute-sponsored clinical trials. MATERIALS AND METHODS: The phantom design was based on a generalized oropharyngeal tumor, including critical H&N structures (parotid glands and spinal cord). Radiochromic film and thermoluminescent dosimeter (TLD)-100 capsules were embedded in the phantom and used to evaluate dose delivery. A spot-scanning treatment plan with typical clinical constraints for H&N cancer was created by using the Eclipse analytic algorithm. The treatment plan was approved by a radiation oncologist and the phantom was irradiated 4 times. The measured dose distribution using a ±7%/4 mm gamma analysis (85% of pixels passing) and point doses were compared with the treatment planning system calculations. The prescribed target dose was 6 Gy (RBE) with 646.2 cGy (RBE) and 648.6 cGy (RBE) planned to the superior and inferior TLD, respectively. RESULTS: For point dosimetry, the average measured-to-calculated dose ratios were 0.984 and 0.986 for the superior and inferior target TLD, respectively. Dose values for the superior and inferior target TLDs were 636.1 cGy and 639.6 cGy, respectively. For the relative dose comparison, the pixel passing rates for the axial and sagittal films, respectively, were 95.5% and 94.2% for trial 1, 97.3% and 93.2% for trial 2, 93.4% and 90.0% for trial 3, and 96.2% and 92.7% for trial 4. CONCLUSION: The anthropomorphic H&N phantom was successfully designed so that TLD measured-to-calculated ratios were within IROC-H's 7% acceptance criteria, 1.6% and 1.4% lower than expected for the superior and inferior target TLDs, respectively. All trials passed the 85% pixel passing criteria established at IROC-H for the relative dose comparison performed when using a gamma index of ±7%/4 mm.

Trans-cultural adaptation and psychometric properties of the 'Sense of Coherence Scale' in mothers of preschool children / Adaptação trans-cultural e propriedades psicométricas da 'Escala de Senso de Coerência' em mães de crianças pré-escolares

The aim of this paper is to present the trans-cultural adaptation and reliability of the Sense of Coherence scale (SOC-13 from Antonovsky) into Portuguese language using a sample of mothers of preschool children. The originally validated scale demonstrated a low return percentage and high number of extreme answers when applied to mothers of preschool children selected by convenience sampling in Brazil. Adaptations were made through cognitive interviews and involved rewording items, the usage of five rather than seven alternatives and the insertion of middle anchoring phrases. Three independent samples took part in the study for the psychometric tests. These samples consisted of one group of 36 and another of 38 mothers selected by convenience, as well as an additional group of 546 mothers randomly selected from the city of Belo Horizonte, Brazil. Instrument reliability was accessed by internal consistency, test-retest and item-to-total-score correlations with each of the three samples, respectively. Findings indicate that the adapted scale is comprehensible and obtained a greater response rate than the originally validated scale. Internal consistency increased from 0.67 for the original scale to 0.71 for the adapted scale. This value was extended to 0.80 in the test with the randomly selected sample. Medium weighted Kappa coefficients were 49.5 percent. The Spearman test demonstrated that the questions were correlated with total SOC scores. Results indicate that the adapted scale is valid and consistent for mothers of preschool children from different social classes.(AU)

O objetivo do presente estudo é apresentar a adaptação trans cultural e a confiabilidade da escala de Senso de Coerência (SOC-13 de Antonovsky) para a língua portuguesa em uma amostra de mães de crianças pré-escolares. A escala originalmente validada demonstrou um baixo percentual de resposta e um elevado número de respostas extremas quando aplicada a mães de crianças pré-escolares de uma amostra de conveniência na cidade de Belo Horizonte, Brasil. Com o auxílio de entrevistas cognitivas, foram feitas adaptações que envolveram a alteração de palavras, o uso de cinco opções de respostas ao invés de sete e a inserção de explicação por escrito para as respostas intermediárias. Três amostras independentes participaram do estudo para os testes psicométricos. Estas três amostras consistiram de um grupo de 36 e outro de 38 mães selecionadas por conveniência, e um terceiro grupo composto por 564 mães selecionadas aleatoriamente. A confiabilidade foi verificada através da consistência interna, teste-reteste e correlação intem-escore total, em cada uma das três amostras respectivamente. Os resultados indicam que a escala adaptada é consistente e obteve uma taxa de respostas superior à da escala originalmente validada. A consistência interna aumentou de 0,67 para 0,71 para a escala adaptada. Este valor aumentou para 0,80 no teste com a amostra aleatoriamente selecionada. Os coeficientes de Kappa ponderado atingiram valores médios de 49,5 por cento. A correlação de Spearman mostrou que todos os itens se correlacionaram com os escores totais de SOC. Os resultados indicam que a escala adaptada é válida e consistente para mães de crianças pré-escolares de diferentes classes sociais.(AU)

Familiares em sala de espera de unidades de bloco cirúrgico (UBC): percepçäo sobre informaçöes recebidas / Relatives in the waiting-room of a unit surgical in a hospital: perception of information received

Identifica as percepçöes evidenciadas pelos familiares de pacientes, durante a permanência destes na Unidade de Bloco Cirúrgico e na Sala de Recuperaçäo Pós-Anestésica. Após a observaçäo realizada junto aos familiares na sala de espera, foi elaborado um insturmento para coleta de dados da populaçäo alvo, através dos quais evidenciou-se o funcionamento do processo de transmissäo de informaçöes (equipe-informante-familiar), bem como os sentimento demonstrados e relatados pelos acompanhantes