Screening for language delay after life-saving therapies in term-born infants.

BACKGROUND: Strong recommendations have been made for the periodic developmental surveillance, screening, and evaluation of children with CHD. This supports similar calls for all at-risk children in order to provide timely, structured early developmental intervention that may improve outcomes. The aim of this study was to determine the accuracy of screening for language delay after life-saving therapies using the parent-completed vocabulary screen of the language Development Survey, by comparing screening with the individually administered language scores of the Bayley Scales of Infant and Toddler Development, Third edition. METHOD: In total, 310 (92.5%) of 335 eligible term-born children, born between 2004 and 2011, receiving complex cardiac surgery, heart or liver transplantation, or extracorporeal membrane oxygenation in infancy, were assessed at 21.5 (2.8) months of age (lost, 25 (7.5%)), through developmental/rehabilitation centres at six sites as part of the Western Canadian Complex Pediatric Therapies Follow-up Group. RESULTS: Vocabulary screening delay was defined as scores ⩽15th percentile. Language delay defined as scores >1 SD below the mean was calculated for language composite score, receptive and expressive communication scores of the Bayley-III. Delayed scores for the 310 children were as follows: vocabulary, 144 (46.5%); language composite, 125 (40.3%); receptive communication, 98 (31.6%); and expressive communication, 124 (40%). Sensitivity, specificity, positive predictive values, and negative predictive values of screened vocabulary delay for tested language composite delay were 79.2, 75.7, 68.8, and 84.3%, respectively. CONCLUSION: High rates of language delay after life-saving therapies are concerning. Although the screening test appears to over-identify language delay relative to the tested Bayley-III, it may be a useful screening tool for early language development leading to earlier referral for intervention.

Medical physics staffing for radiation oncology: a decade of experience in Ontario, Canada.

The January 2010 articles in The New York Times generated intense focus on patient safety in radiation treatment, with physics staffing identified frequently as a critical factor for consistent quality assurance. The purpose of this work is to review our experience with medical physics staffing, and to propose a transparent and flexible staffing algorithm for general use. Guided by documented times required per routine procedure, we have developed a robust algorithm to estimate physics staffing needs according to center-specific workload for medical physicists and associated support staff, in a manner we believe is adaptable to an evolving radiotherapy practice. We calculate requirements for each staffing type based on caseload, equipment inventory, quality assurance, educational programs, and administration. Average per-case staffing ratios were also determined for larger-scale human resource planning and used to model staffing needs for Ontario, Canada over the next 10 years. The workload specific algorithm was tested through a survey of Canadian cancer centers. For center-specific human resource planning, we propose a grid of coefficients addressing specific workload factors for each staff group. For larger scale forecasting of human resource requirements, values of 260, 700, 300, 600, 1200, and 2000 treated cases per full-time equivalent (FTE) were determined for medical physicists, physics assistants, dosimetrists, electronics technologists, mechanical technologists, and information technology specialists, respectively.

Position-probability-sampled Monte Carlo calculation of VMAT, 3DCRT, step-shoot IMRT, and helical tomotherapy dose distributions using BEAMnrc/DOSXYZnrc.

PURPOSE: The commercial release of volumetric modulated arc therapy techniques using a conventional linear accelerator and the growing number of helical tomotherapy users have triggered renewed interest in dose verification methods, and also in tools for exploring the impact of machine tolerance and patient motion on dose distributions without the need to approximate time-varying parameters such as gantry position, MLC leaf motion, or patient motion. To this end we have developed a Monte Carlo-based calculation method capable of simulating a wide variety of treatment techniques without the need to resort to discretization approximations. METHODS: The ability to perform complete position-probability-sampled Monte Carlo dose calculations was implemented in the BEAMnrc/DOSXZYnrc user codes of EGSnrc. The method includes full accelerator head simulations of our tomotherapy and Elekta linacs, and a realistic representation of continous motion via the sampling of a time variable. The functionality of this algorithm was tested via comparisons with both measurements and treatment planning dose distributions for four types of treatment techniques: 3D conformal, step-shoot intensity modulated radiation therapy, helical tomotherapy, and volumetric modulated are therapy. RESULTS: For static fields, the absolute dose agreement between the EGSnrc Monte Carlo calculations and measurements is within 2%/1 mm. Absolute dose agreement between Monte Carlo calculations and treatment planning system for the four different treatment techniques is within 3%/3 mm. Discrepancies with the tomotherapy TPS on the order of 10%/5 mm were observed for the extreme example of a small target located 15 cm off-axis and planned with a low modulation factor. The increase in simulation time associated with using position-probability sampling, as opposed to the discretization approach, was less than 2% in most cases. CONCLUSIONS: A single Monte Carlo simulation method can be used to calculate patient dose distribution for various types of treatment techniques delivered with either tomotherapy or a conventional linac. The method simplifies the simulation process, improves dose calculation accuracy, and involves an acceptably small change in computation time.

Integration of on-line imaging, plan adaptation and radiation delivery: proof of concept using digital tomosynthesis.

The main objective of this manuscript is to propose a new approach to on-line adaptive radiation therapy (ART) in which daily image acquisition, plan adaptation and radiation delivery are integrated together and performed concurrently. A method is described in which on-line ART is performed based on intra-fractional digital tomosynthesis (DTS) images. Intra-fractional DTS images were reconstructed as the gantry rotated between treatment positions. An edge detection algorithm was used to automatically segment the DTS images as the gantry arrived at each treatment position. At each treatment position, radiation was delivered based on the treatment plan re-optimized for the most recent DTS image contours. To investigate the feasibility of this method, a model representing a typical prostate, bladder and rectum was used. To simulate prostate deformations, three clinically relevant, non-rigid deformations (small, medium and large) were modeled by systematically deforming the original anatomy. Using our approach to on-line ART, the original treatment plan was successfully adapted to arrive at a clinically acceptable plan for all three non-rigid deformations. In conclusion, we have proposed a new approach to on-line ART in which plan adaptation is performed based on intra-fractional DTS images. The study findings indicate that this approach can be used to re-optimize the original treatment plan to account for non-rigid anatomical deformations. The advantages of this approach are 1) image acquisition and radiation delivery are integrated in a single gantry rotation around the patient, reducing the treatment time, and 2) intra-fractional DTS images can be used to detect and correct for patient motion prior to the delivery of each beam (intra-fractional patient motion).

On-line rapid palliation using helical tomotherapy: a prospective feasibility study.

Rapid delivery of radiation therapy is expected to benefit patients requiring palliation. We investigated the feasibility of employing a helical tomotherapy unit to scan, plan, and deliver a radiation treatment in a single radiation therapy appointment. Eleven patients each had an MVCT scan acquired, a plan created, and delivery completed while the patient was on the treatment couch. Timelines for each step of the process were recorded for each patient, and compared with the conventional process for similar patients. Preliminary results show that patients routinely can be treated within a 1 hour appointment for the first fraction.

Direct aperture optimization for online adaptive radiation therapy.

This paper is the first investigation of using direct aperture optimization (DAO) for online adaptive radiation therapy (ART). A geometrical model representing the anatomy of a typical prostate case was created. To simulate interfractional deformations, four different anatomical deformations were created by systematically deforming the original anatomy by various amounts (0.25, 0.50, 0.75, and 1.00 cm). We describe a series of techniques where the original treatment plan was adapted in order to correct for the deterioration of dose distribution quality caused by the anatomical deformations. We found that the average time needed to adapt the original plan to arrive at a clinically acceptable plan is roughly half of the time needed for a complete plan regeneration, for all four anatomical deformations. Furthermore, through modification of the DAO algorithm the optimization search space was reduced and the plan adaptation was significantly accelerated. For the first anatomical deformation (0.25 cm), the plan adaptation was six times more efficient than the complete plan regeneration. For the 0.50 and 0.75 cm deformations, the optimization efficiency was increased by a factor of roughly 3 compared to the complete plan regeneration. However, for the anatomical deformation of 1.00 cm, the reduction of the optimization search space during plan adaptation did not result in any efficiency improvement over the original (nonmodified) plan adaptation. The anatomical deformation of 1.00 cm demonstrates the limit of this approach. We propose an innovative approach to online ART in which the plan adaptation and radiation delivery are merged together and performed concurrently-adaptive radiation delivery (ARD). A fundamental advantage of ARD is the fact that radiation delivery can start almost immediately after image acquisition and evaluation. Most of the original plan adaptation is done during the radiation delivery, so the time spent adapting the original plan does not increase the overall time the patient has to spend on the treatment couch. As a consequence, the effective time allotted for plan adaptation is drastically reduced. For the 0.25, 0.5, and 0.75 cm anatomical deformations, the treatment time was increased by only 2, 4, and 6 s, respectively, as compared to no plan adaptation. For the anatomical deformation of 1.0 cm the time increase was substantially larger. The anatomical deformation of 1.0 cm represents an extreme case, which is rarely observed for the prostate, and again demonstrates the limit of this approach. ARD shows great potential for an online adaptive method with minimal extension of treatment time.

Geometric parameter analysis to predetermine optimal radiosurgery technique for the treatment of arteriovenous malformation.

PURPOSE: To develop a method of predicting the values of dose distribution parameters of different radiosurgery techniques for treatment of arteriovenous malformation (AVM) based on internal geometric parameters. METHODS AND MATERIALS: For each of 18 previously treated AVM patients, four treatment plans were created: circular collimator arcs, dynamic conformal arcs, fixed conformal fields, and intensity-modulated radiosurgery. An algorithm was developed to characterize the target and critical structure shape complexity and the position of the critical structures with respect to the target. Multiple regression was employed to establish the correlation between the internal geometric parameters and the dose distribution for different treatment techniques. The results from the model were applied to predict the dosimetric outcomes of different radiosurgery techniques and select the optimal radiosurgery technique for a number of AVM patients. RESULTS: Several internal geometric parameters showing statistically significant correlation (p < 0.05) with the treatment planning results for each technique were identified. The target volume and the average minimum distance between the target and the critical structures were the most effective predictors for normal tissue dose distribution. The structure overlap volume with the target and the mean distance between the target and the critical structure were the most effective predictors for critical structure dose distribution. The predicted values of dose distribution parameters of different radiosurgery techniques were in close agreement with the original data. CONCLUSIONS: A statistical model has been described that successfully predicts the values of dose distribution parameters of different radiosurgery techniques and may be used to predetermine the optimal technique on a patient-to-patient basis.

A comparison of two commercial treatment-planning systems to IMRT.

This study compared the clinical functionality of BrainSCAN (BrainLAB) and Helios (Eclipse, Varian) for intensity-modulated radiation therapy (IMRT) treatment planning with the aim of identifying practical and technical issues. The study considered implementation and commissioning, dose optimization, and plan assessment. Both systems were commissioned for the same 6 MV photon beam equipped with a high-resolution multileaf collimator (Varian Millennium 120 leaf). The software was applied to three test plans having identical imaging and contour data. Analysis considered 3D axial dose distributions, dose-volume histograms, and monitor unit calculations. Each system requires somewhat different input data to characterize the beam prior to use, so the same data cannot be used for commissioning. In addition, whereas measured beam data was entered directly into Helios with minimal data processing, the BrainSCAN system required configured beam data to be sent to BrainLAB before clinical use. One key difference with respect to system commissioning was that BrainSCAN required high resolution data, which necessitated the use of detectors with small active volumes. This difference was found to impact on the ability of the systems to accurately calculate dose for highly modulated fields, with BrainSCAN being more successful than Helios. In terms of functionality, the BrainSCAN system uses a dynamically penalized likelihood inverse planning algorithm and calculates four plans at once with various relative weighting of the planning target and organ-at-risk volumes. Helios uses a gradient algorithm that allows the user to make changes to some of the input parameters during optimization. An analysis of the dosimetry output shows that, although the systems are different in many respects, they are each capable of producing substantially equivalent dose plans in terms of target coverage and normal tissue sparing.

Analysis of patient repositioning accuracy in precision radiation therapy using automated image fusion.

This work describes a rapid and objective method of determining repositioning error during the course of precision radiation therapy using off-line CT imaging and automated mutual-information image fusion. The technique eliminates the variability associated with manual identification of anatomical landmarks by observers. A phantom study was conducted to quantify the accuracy of the image co-registration-based analysis itself. For CT voxel dimensions of 0.65 x 0.65 x1.0 mm3, the method is shown to detect translations with an accuracy of 0.5 mm in the anterior-posterior and lateral dimensions and 0.8 mm in the superior-inferior dimension. Phantom rotation in the coronal plane was detected to within 0.5 degrees of expected values. The analysis has been applied to eight radiotherapy patients at two independent clinics, each immobilized by the same system for cranial stereotactic radiotherapy and CT-imaged once per week over the five- to six-week course of treatment. Among all patients, the ranges of translation in the anterior-posterior, lateral, and superior-inferior dimensions were -0.91 mm to 0.77 mm, -0.66 mm to 1.02 mm, and -2.24 mm to 3.47 mm, respectively. Considering all patients and CT scans, the standard deviations of translation were 0.42 mm, 0.47 mm, and 1.36 mm in the anterior-posterior, lateral, and superior-inferior dimensions, respectively. The ranges of patient rotation about the superior-inferior, left-right, and anterior-posterior axes were -2.84 to 2.62 degrees, -1.74 degrees to 1.96 degrees, and -1.78 degrees to 1.42 degrees, respectively.

Exploring the limits of spatial resolution in radiation dose delivery.

Flexibility and complexity in patient treatment due to advances in radiotherapy techniques necessitates a simple method for evaluating spatial resolution capabilities of the dose delivery device. Our purpose in this investigation is to evaluate a model that describes the ability of a radiation therapy device to deliver a desired dose distribution. The model is based on linear systems theory and is analogous to methods used to describe resolution degradation in imaging systems. A qualitative analysis of spatial resolution degradation using the model is presented in the spatial and spatial frequency domains. The ability of the model to predict the effects of geometric dose conformity to treatment volumes is evaluated by varying multileaf collimator leaf width and magnitude of dose spreading. Dose distributions for three clinical treatment shapes, circular shapes of varying diameter and one intensity modulated shape are used in the evaluation. We show that the model accurately predicts the dependence of dose conformity on these parameters. The spatial resolution capabilities of different radiation therapy devices can be quantified using the model, providing a simple method for comparing different treatment machine characteristics. Also, as different treatment sites have different resolution requirements this model may be used to tailor machine characteristics to the specific site.

Enhancement of IMRT delivery through MLC rotation.

Multileaf collimator (MLC) based intensity modulated radiation therapy (IMRT) techniques are well established but suffer several physical limitations. Dosimetric spatial resolution is limited by the MLC leaf width; interleaf leakage and tongue-and-groove effects degrade dosimetric accuracy and the range of leaf motion limits the maximum deliverable field size. Collimator rotation is used in standard radiation therapy to improve the conformity of the MLC shape to the target volume. Except for opposed orthogonal fields, collimator rotation has not been exploited in IMRT due to the complexity of deriving the MLC leaf configurations for rotated sub-fields. Here we report on a new way that MLC-based IMRT is delivered which incorporates collimator rotation, providing an extra degree of freedom in deriving leaf sequences for a desired fluence map. Specifically, we have developed a series of unique algorithms that are capable of determining rotated MLC segments. These IMRT fields may be delivered statically (with the collimator rotating to a new position in between sub-fields) or dynamically (with the collimator rotating and leaves moving simultaneously during irradiation). This introductory study provides an analysis of the rotating leaf motion calculation algorithms with focus on radiation efficiency, the range of collimator rotation and number of segments. We then evaluate the technique by characterizing the ability of the algorithms to generate rotating leaf sequences for desired fluence maps. Comparisons are also made between our method and conventional sliding window and step-and-shoot techniques. Results show improvements in spatial resolution, reduced interleaf effects and maximum deliverable field size over conventional techniques. Clinical application of these enhancements can be realized immediately with static rotational delivery although improved dosimetric modelling of the MLC will be required for dynamic delivery.

Patient safety improvements in radiation treatment through 5 years of incident learning.

PURPOSE: To quantify the impact of a comprehensive incident learning system in terms of safety improvements. METHODS AND MATERIALS: An incident learning system tailored for radiation treatment and based on published principles has been used consistently in our large academic cancer center for more than 5 years. In the adopted system, every incident, whether or not there is a resulting direct impact on a patient treatment, is recorded and investigated to determine basic causes. The scope of the program thus includes potential, or near miss, events which have no impact on patients but which provide valuable insights into program weaknesses and hence facilitate proactive measures to minimize risk. RESULTS: Analysis of 2506 incident reports generated over a 5-year period demonstrate a substantial decline in actual, nonminor incidents; ie, those with a dose variation from that prescribed of greater than 5%. Only 49 incidents (1.95%) had an impact on patients. The actual incident rate at the point of treatment delivery, the most vulnerable point in our process, has also decreased. The system has provided rapid feedback to monitor several initiatives including implementation of new technology and several new treatment techniques. Using the evidence provided by these incident reports, strategies were developed by a multidisciplinary team to address system weaknesses. Interventions introduced include several human error reduction strategies including forcing functions and constraints to improve system resilience. CONCLUSIONS: Our results demonstrate that effective use of an incident learning system will strongly encourage the reporting of incidents, whether or not they directly impact a patient, and serve as a proactive means of enhancing safety and quality. As a side benefit, addressing and overcoming the cultural barriers between the 3 professional groups involved in radiation treatment has resulted in an improvement in the safety culture in our center.

Evaluation of a thermoplastic immobilization system for breast and chest wall radiation therapy.

We report on the impact of a thermoplastic immobilization system on intra- and interfraction motion for patients undergoing breast or chest wall radiation therapy. Patients for this study were treated using helical tomotherapy. All patients were immobilized using a thermoplastic shell extending from the shoulders to the ribcage. Intrafraction motion was assessed by measuring maximum displacement of the skin, heart, and chest wall on a pretreatment 4D computed tomography, while inter-fraction motion was inferred from patient shift data arising from daily image guidance procedures on tomotherapy. Using thermoplastic immobilization, the average maximum motion of the external contour was 1.3 ± 1.6 mm, whereas the chest wall was found to be 1.6 ± 1.9 mm. The day-to-day setup variation was found to be large, with random errors of 4.0, 12.0, and 4.5 mm in the left-right, superior-inferior, and anterior-posterior directions, respectively, and the standard deviations of the systematic errors were found to be 2.7, 9.8, and 4.1 mm. These errors would be expected to dominate any respiratory motion but can be mitigated by daily online image guidance. Using thermoplastic immobilization can effectively reduce respiratory motion of the chest wall and external contour, but these gains can only be realized if daily image guidance is used.

The management of radiation treatment error through incident learning.

PURPOSE: To assess efficacy of an incident learning system in the management of error in radiation treatment. MATERIALS AND METHODS: We report an incident learning system implementation customized for radiation therapy where any "unwanted or unexpected change from normal system behaviour that causes or has the potential to cause an adverse effect to persons or equipment" is reported, investigated and learned from. This system thus captures near-miss (potential) and actual events. Incidents are categorized according to severity, type and origin. RESULTS: Our analysis spans a period of 3 years with an average accrual of 11.6 incidents per week. We found a significant reduction in actual incidents of 28% and 47% in the second and third year when compared to the first year (p<0.001), which we attribute to the many interventions prompted by the analysis of incidents reported. We also saw a similar significant reduction in incidents generated at the treatment unit correlating with the introduction of direct treatment parameter transfer and electronic imaging (p<0.001). CONCLUSIONS: Implementation of an incident learning system has helped us to establish a just environment where all staff members report deviations from normal system behaviour and thus generate evidence to initiate safety improvements.

Optimization of stereotactic radiotherapy treatment delivery technique for base-of-skull meningiomas.

This study compares static conformal field (CF), intensity modulated radiotherapy (IMRT), and dynamic arcs (DA) for the stereotactic radiotherapy of base-of-skull meningiomas. Twenty-one cases of base-of-skull meningioma (median planning target volume [PTV] = 21.3 cm3) previously treated with stereotactic radiotherapy were replanned with each technique. The plans were compared for Radiation Therapy Oncology Group conformity index (CI) and homogeneity index (HI), and doses to normal structures at 6 dose values from 50.4 Gy to 5.6 Gy. The mean CI was 1.75 (CF), 1.75 (DA), and 1.66 (IMRT) (p < 0.05 when comparing IMRT to either CF or DA plans). The CI (IMRT) was inversely proportional to the size of the PTV (Spearman's rho = -0.53, p = 0.01) and at PTV sizes above 25 cm3, the CI (IMRT) was always superior to CI (DA) and CI (CF). At PTV sizes below 25 cm3, there was no significant difference in CI between each technique. There was no significant difference in HI between plans. The total volume of normal tissue receiving 50.4, 44.8, and 5.6 Gy was significantly lower when comparing IMRT to CF and DA plans (p < 0.05). There was significantly improved dose sparing for the brain stem and ipsilateral temporal lobe with IMRT but no significant difference for the optic chiasm or pituitary gland. These results demonstrate that stereotactic IMRT should be considered to treat base-of-skull meningiomas with a PTV larger than 25 cm3, due to improved conformity and normal tissue sparing, in particular for the brain stem and ipsilateral temporal lobe.

Five-year neurocognitive and health outcomes after the neonatal arterial switch operation.

OBJECTIVES: We sought to assess the 5-year neurocognition and health of an interprovincial inception cohort undergoing the arterial switch operation for transposition of the great arteries. METHODS: Sixty-nine consecutive neonates had operations from 1996-2003 with full-flow cardiopulmonary bypass and selective deep hypothermic circulatory arrest. Outcomes were recorded at 58 +/- 9 months of age. Univariate and multivariate analyses were used to identify outcome predictors, including surgical subtype and preoperative, operative, and postoperative variables. RESULTS: There was 1 (1.5%) operative death. Two children were lost to follow-up, and 1 was excluded because of postdischarge meningitis. Outcomes are reported for 65 survivors. Two (3%) children have cerebral palsy, and 7 (11%) have language disorders, 4 of whom also meet the criteria for autism spectrum disorder. Two of the 4 children with autism have an affected older sibling. Of the 61 children without autism, scores approach those of peers, with a full-scale intelligence quotient of 97 +/- 16, a verbal intelligence quotient of 97 +/- 18, a performance intelligence quotient of 96 +/- 15, and a visual-motor integration score of 95 +/- 16. Mother's education, birth gestation or weight, and postoperative plasma lactate values account for 21% to 32% of the variance of these scores. Septostomy adds 7% to the variance of visual-motor integration scores. CONCLUSIONS: Most preschool children do well after surgical correction for transposition of the great arteries, including complex forms. Potentially modifiable variables include high preoperative plasma lactate levels and septostomy. A minority of children were given diagnoses of language disorders, including autism, in which familial factors likely contribute to outcome.