Assessing the need for adaptive radiotherapy in head and neck cancer patients using an automatic planning tool.

BACKGROUND: Unbiased analysis of the impact of adaptive radiotherapy (ART) is necessary to evaluate dosimetric benefit and optimize clinics' workflows. The aim of the study was to assess the need for adaptive radiotherapy (ART) in head and neck (H&N) cancer patients using an automatic planning tool in a retrospective planning study. MATERIALS AND METHODS: Thirty H&N patients treated with adaptive radiotherapy were analysed. Patients had a CT scan for treatment planning and a verification CT during treatment according to the clinic's protocol. Considering these images, three plans were retrospectively generated using the iCycle tool to simulate the scenarios with and without adaptation: 1) the optimized plan based on the planning CT; 2) the optimized plan based on the verification CT (ART-plan); 3) the plan obtained by considering treatment plan 1 re-calculated in the verification CT (non-ART plan). The dosimetric endpoints for both target volumes and OAR were compared between scenarios 2 and 3 and the SPIDERplan used to evaluate plan quality. RESULTS: The most significant impact of ART was found for the PTVs, which demonstrated decreased D98% in the non-ART plan. A general increase in the dose was observed for the OAR but only the spinal cord showed a statistical significance. The SPIDERplan analysis indicated an overall loss of plan quality in the absence of ART. CONCLUSION: These results confirm the advantages of ART in H&N patients, especially for the coverage of target volumes. The usage of an automatic planning tool reduces planner-induced bias in the results, guaranteeing that the observed changes derive from the application of ART.

A protocol for absolute dose verification of SBRT/SRS treatment plans using Gafchromic™ EBT-XD films.

PURPOSE: To provide a practical protocol for absolute dose verification of stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) treatment plans, based on our clinical experience. It aims to be a concise summary of the main aspects to be considered when establishing an accurate film dosimetry system. METHODS: Procedures for film calibration and conversion to dose are described for a dosimetry system composed of Gafchromic™ EBT-XD films and a flatbed document scanner. Factors that affect the film-scanner response are also reviewed and accounted for. The accuracy of the proposed methodology was assessed by taking a set of strips irradiated to known doses and its applicability is illustrated for ten SBRT/SRS treatment plans. The film response was converted to dose using red and triple channel dosimetry. The agreement between the planned and measured dose distributions was evaluated using global gamma analysis with criteria of 3%/2mm 10% threshold (TH), 2%/2mm 10% TH, and 2%/2mm 20% TH. RESULTS: The differences between the expected and determined doses from the strips analysis were 0.9 ± 0.6% for the red channel and 1.1 ± 0.7% for the triple channel method. Regarding the SBRT/SRS plans verification, the mean gamma passing rates were 99.5 ± 1.0% vs 99.6 ± 1.0% (3%/2mm 10% TH), 96.9 ± 3.5% vs 99.1 ± 1.3% (2%/2mm 10% TH) and 98.4 ± 1.8% vs 98.8 ± 1.5% (2%/2mm 20% TH) for red and triple channel dosimetry, respectively. CONCLUSIONS: The proposed protocol allows for accurate absolute dose verification of SBRT/SRS treatment plans, applying both single and triple channel methods. It may work as a guide for users that intend to implement a film dosimetry system.

On the complexity of helical tomotherapy treatment plans.

PURPOSE: Multiple metrics are proposed to characterize and compare the complexity of helical tomotherapy (HT) plans created for different treatment sites. METHODS: A cohort composed of 208 HT plans from head and neck (105), prostate (51) and brain (52) tumor sites was considered. For each plan, 14 complexity metrics were calculated. Those metrics evaluate the percentage of leaves with small opening times or approaching the projection duration, the percentage of closed leaves, the amount of tongue-and-groove effect, and the overall modulation of the planned sinogram. To enable data visualization, an approach based on principal component analysis was followed to reduce the dataset dimensionality. This allowed the calculation of a global plan complexity score. The correlation between plan complexity and pretreatment verification results using the Spearman's rank correlation coefficients was investigated. RESULTS: According to the global score, the most complex plans were the head and neck tumor cases, followed by the prostate and brain lesions irradiated with stereotactic technique. For almost all individual metrics, head and neck plans confirmed to be the plans with the highest complexity. Nevertheless, prostate cases had the highest percentage of leaves with an opening time approaching the projection duration, whereas the stereotactic brain plans had the highest percentage of closed leaves per projection. Significant correlations between some of the metrics and the pretreatment verification results were identified for the stereotactic brain group. CONCLUSIONS: The proposed metrics and the global score demonstrated to be useful to characterize and quantify the complexity of HT plans of different treatment sites. The reported differences inter- and intra-group may be valuable to guide the planning process aiming at reducing uncertainties and harmonize planning strategies.

Clinical validation of a graphical method for radiation therapy plan quality assessment.

BACKGROUND: This work aims at clinically validating a graphical tool developed for treatment plan assessment, named SPIDERplan, by comparing the plan choices based on its scoring with the radiation oncologists (RO) clinical preferences. METHODS: SPIDERplan validation was performed for nasopharynx pathology in two steps. In the first step, three ROs from three Portuguese radiotherapy departments were asked to blindly evaluate and rank the dose distributions of twenty pairs of treatment plans. For plan ranking, the best plan from each pair was selected. For plan evaluation, the qualitative classification of 'Good', 'Admissible with minor deviations' and 'Not Admissible' were assigned to each plan. In the second step, SPIDERplan was applied to the same twenty patient cases. The tool was configured for two sets of structures groups: the local clinical set and the groups of structures suggested in international guidelines for nasopharynx cancer. Group weights, quantifying the importance of each group and incorporated in SPIDERplan, were defined according to RO clinical preferences and determined automatically by applying a mixed linear programming model for implicit elicitation of preferences. Intra- and inter-rater ROs plan selection and evaluation were assessed using Brennan-Prediger kappa coefficient. RESULTS: Two-thirds of the plans were qualitatively evaluated by the ROs as 'Good'. Concerning intra- and inter-rater variabilities of plan selection, fair agreements were obtained for most of the ROs. For plan evaluation, substantial agreements were verified in most cases. The choice of the best plan made by SPIDERplan was identical for all sets of groups and, in most cases, agreed with RO plan selection. Differences between RO choice and SPIDERplan analysis only occurred in cases for which the score differences between the plans was very low. A score difference threshold of 0.005 was defined as the value below which two plans are considered of equivalent quality. CONCLUSION: Generally, SPIDERplan response successfully reproduced the ROs plan selection. SPIDERplan assessment performance can represent clinical preferences based either on manual or automatic group weight assignment. For nasopharynx cases, SPIDERplan was robust in terms of the definitions of structure groups, being able to support different configurations without losing accuracy.

Evaluation of the complexity of treatment plans from a national IMRT/VMAT audit - Towards a plan complexity score.

PURPOSE: This work aimed to characterize and compare the complexity of the plans created in the context of a national IMRT/VMAT audit. A plan complexity score is proposed to summarize all the evaluated complexity features. MATERIALS AND METHODS: Nine complexity metrics have been computed for the audit plans, evaluating different complexity aspects. An approach based on Principal Component Analysis was followed to explore the correlation between the metrics and derive a smaller set of new uncorrelated variables (principal components, PCs). The resulting PCs were then used to calculate a plan complexity score. Plan quality was also assessed and the correlation between plan complexity, quality and deliverability investigated using the Spearman's rank correlation coefficient. RESULTS: The first two PCs explained over 90% of the total variance in the original dataset. Their representation allowed to identify patterns in the data, namely a clear separation between plans created using different technologies/techniques. The calculated plan complexity score quantified these differences. Sliding window Eclipse plans were found to be the most complex and VMAT Eclipse group presented the highest complexity variability, for the evaluated parameters. Concerning plan quality, no differences between treatment technology/technique have been identified. However, plans with larger number of monitor units tended to be associated with higher deviations between calculated and measured doses. CONCLUSIONS: The proposed plan complexity score allowed to summarize the differences not only inter- but also intra-groups of technologies/techniques, paving the way for improvement of the planning strategies at the national level through knowledge sharing.

Application of the TRS 483 code of practice for reference and relative dosimetry in tomotherapy.

PURPOSE: To apply the recent code of practice from the IAEA/AAPM, TRS 483, to helical tomotherapy (HT) for reference and relative dosimetry obtaining correction factors for the Exradin A1SL ionization chamber. METHODS: The beam quality correction factor for the A1SL chamber was obtained through three different approaches following TRS 483 concepts and compared with published values. The determination of the reference absolute dose for the machine-specific reference (msr) field was complemented with relative dosimetry through the determination of output factors of small fields using different detectors. The response of A1SL was compared with correction-free film results and corrected output factors of other detectors. RESULTS: A weighted mean beam quality correction factor of 0.9945± 0.0073 was obtained for the A1SL chamber which is in agreement with values reported in the literature. Output factors obtained with different detectors were in agreement, given the uncertainty level. Considering the film output factors as free of corrections, the average value for A1SL output factors corrections was 1.000 ± 0.007. CONCLUSIONS: The beam quality correction factors for the A1SL chamber obtained through the three different pathways recommended by TRS 483 agreed with each other and also with published values. The measurements from the A1SL chamber normalized to the msr field in HT can be taken as output factors for small clinical field sizes without further corrections.

Comparison of two beam angular optimization algorithms guided by automated multicriterial IMRT.

PURPOSE: To compare two beam angle optimization (BAO) algorithms for coplanar and non-coplanar geometries in a multicriterial optimization framework. METHODS: 40 nasopharynx patients were selected for this retrospective planning study. IMRT optimized plans were produced by Erasmus-iCycle multicriterial optimization platform. Two different algorithms, based on a discrete and on a continuous exploration of the space search, algorithm i and B respectively, were used to address BAO. Plan quality evaluation and comparison were performed with SPIDERplan. Statistically significant differences between the plans were also assessed. RESULTS: For plans using only coplanar incidences, the optimized beam distribution with algorithm i is more asymmetric than with algorithm B. For non-coplanar beam optimization, larger deviations from coplanarity were obtained with algorithm i than with algorithm B. Globally, both algorithms presented near equivalent plan quality scores, with algorithm B presenting a marginally better performance than algorithm i. CONCLUSION: Almost all plans presented high quality, profiting from multicriterial and beam angular optimization. Although there were not significant differences when average results over the entire sample were considered, a case-by-case analysis revealed important differences for some patients.

IMRT national audit in Portugal.

PURPOSE: The IAEA newly developed "end-to-end" audit methodology for on-site verification of IMRT dose delivery has been carried out in Portugal in 2018. The main goal was to evaluate the physical aspects of the head and neck (H&N) cancer IMRT treatments. This paper presents the national results. METHODS: All institutions performing IMRT treatments in Portugal, 20 out of 24, have voluntarily participated in this audit. Following the adopted methodology, a Shoulder, Head and Neck End-to-End phantom (SHANE) - that mimics an H&N region, underwent all steps of an IMRT treatment, according to the local practices. The measurements using an ionization chamber placed inside the SHANE phantom at four reference locations (three in PTVs and one in the spinal cord) and an EBT3 film positioned in a coronal plane were compared with calculated doses. FilmQA Pro software was used for film analysis. RESULTS: For ionization chamber measurements, the percent difference was within the specified tolerances of ±5% for PTVs and ±7% for the spinal cord in all participating institutions. Considering film analysis, gamma passing rates were on average 96.9%±2.9% for a criterion of 3%/3 mm, 20% threshold, all above the acceptance limit of 90%. CONCLUSIONS: The national results of the H&N IMRT audit showed a compliance between the planned and the delivered doses within the specified tolerances, confirming no major reasons for concern. At the same time the audit identified factors that contributed to increased uncertainties in the IMRT dose delivery in some institutions resulting in recommendations for quality improvement.

Biological dose-escalated definitive radiation therapy in head and neck cancer.

OBJECTIVE: To compare treatment outcome of patients with head and neck (HN) tumours treated with definitive radiation therapy that, mainly owing to differences in the fractionation scheme used with simultaneous integrated boost techniques, resulted in a different biological dose. METHODS: 181 patients with HN cancer, prescribed to about 70.2 Gy in the primary tumour, were included in this study. Population cohort was divided into Group <70 and Group ≥70 when the mean dose converted to a 2 Gy fractionation in the primary tumour was less or higher than 70.2 Gy, respectively. The probability of local control (LC), locoregional control (LRC), disease-free survival (DFS) and overall survival (OS) was determined for both groups. The incidence of acute and late complications was compared between the two groups. RESULTS: At 24 months for Groups <70 and ≥70, LC was 83.2% and 87.5%, LRC was 79.5% and 81.6%, DFS was 56.3% and 66.8% and OS was 63.9% and 71.5% p = ns, respectively. The incidence of acute dysphagia, odynophagia and pain, and late mucositis was significantly higher in Group ≥70 than in Group <70. The rate of xerostomia, dysphonia, radiodermatitis, alopecia, dental complications, hypoacusia and weight loss was comparable between the two groups. CONCLUSION: The biological dose escalation was safe, but an increase in the incidence of the acute side effects: dysphagia, odynophagia and pain and late mucositis, was obtained. Advances in knowledge: Despite the significant biological dose escalation, within the range of doses delivered to this cohort, no clear dose-response effect was observed.

A derivative-free multistart framework for an automated noncoplanar beam angle optimization in IMRT.

PURPOSE: The inverse planning of an intensity-modulated radiation therapy (IMRT) treatment requires decisions regarding the angles used for radiation incidence, even when arcs are used. The possibility of improving the quality of treatment plans by an optimized selection of the beam angle incidences-beam angle optimization (BAO)-is seldom done in clinical practice. The inclusion of noncoplanar beam incidences in an automated optimization routine is even more unusual. However, for some tumor sites, the advantage of considering noncoplanar beam incidences is well known. This paper presents the benefits of using a derivative-free multistart framework for the optimization of the noncoplanar BAO problem. METHODS: Multistart methods combine a global strategy for sampling the search space with a local strategy for improving the sampled solutions. The proposed global strategy allows a thorough exploration of the continuous search space of the highly nonconvex BAO problem. To avoid local entrapment, a derivative-free method is used as local procedure. Additional advantages of the derivative-free method include the reduced number of function evaluations required to converge and the ability to use multithreaded computing. Twenty nasopharyngeal clinical cases were selected to test the proposed multistart framework. The planning target volumes included the primary tumor, the high and low risk lymph nodes. Organs-at-risk included the spinal cord, brainstem, optical nerves, chiasm, parotids, oral cavity, brain, thyroid, among others. For each case, a setup with seven equispaced beams was chosen and the resulting treatment plan, using a multicriteria optimization framework, was then compared against the coplanar and noncoplanar plans using the optimal beam setups obtained by the derivative-free multistart framework. RESULTS: The optimal noncoplanar beam setup obtained by the derivative-free multistart framework leads to high quality treatment plans with better target coverage and with improved organ sparing compared to treatment plans using equispaced or optimal coplanar beam angle setups. The noncoplanar treatment plans achieved, e.g., an average reduction in the mean dose of the oral cavity of 6.1 Gy and an average reduction in the maximum-dose of the brainstem of 7 Gy when compared to the equispaced treatment plans. CONCLUSIONS: The noncoplanar BAO problem is an extremely challenging multimodal optimization problem that can be successfully addressed through a thoughtful exploration of the continuous highly nonconvex BAO search space. The proposed framework is capable of calculating high quality treatment plans and thus can be an interesting alternative toward automated noncoplanar beam selection in IMRT treatment planning which is nowadays the natural trend in treatment planning.

SPIDERplan: A tool to support decision-making in radiation therapy treatment plan assessment.

AIM: In this work, a graphical method for radiotherapy treatment plan assessment and comparison, named SPIDERplan, is proposed. It aims to support plan approval allowing independent and consistent comparisons of different treatment techniques, algorithms or treatment planning systems. BACKGROUND: Optimized plans from modern radiotherapy are not easy to evaluate and compare because of their inherent multicriterial nature. The clinical decision on the best treatment plan is mostly based on subjective options. MATERIALS AND METHODS: SPIDERplan combines a graphical analysis with a scoring index. Customized radar plots based on the categorization of structures into groups and on the determination of individual structures scores are generated. To each group and structure, an angular amplitude is assigned expressing the clinical importance defined by the radiation oncologist. Completing the graphical evaluation, a global plan score, based on the structures score and their clinical weights, is determined. After a necessary clinical validation of the group weights, SPIDERplan efficacy, to compare and rank different plans, was tested through a planning exercise where plans had been generated for a nasal cavity case using different treatment planning systems. RESULTS: SPIDERplan method was applied to the dose metrics achieved by the nasal cavity test plans. The generated diagrams and scores successfully ranked the plans according to the prescribed dose objectives and constraints and the radiation oncologist priorities, after a necessary clinical validation process. CONCLUSIONS: SPIDERplan enables a fast and consistent evaluation of plan quality considering all targets and organs at risk.

Medical physics in Europe following recommendations of the International Atomic Energy Agency.

BACKGROUND: Medical physics is a health profession where principles of applied physics are mostly directed towards the application of ionizing radiation in medicine. The key role of the medical physics expert in safe and effective use of ionizing radiation in medicine was widely recognized in recent European reference documents like the European Union Council Directive 2013/59/EURATOM (2014), and European Commission Radiation Protection No. 174, European Guidelines on Medical Physics Expert (2014). Also the International Atomic Energy Agency (IAEA) has been outspoken in supporting and fostering the status of medical physics in radiation medicine through multiple initiatives as technical and cooperation projects and important documents like IAEA Human Health Series No. 25, Roles and Responsibilities, and Education and Training Requirements for Clinically Qualified Medical Physicists (2013) and the International Basic Safety Standards, General Safety Requirements Part 3 (2014). The significance of these documents and the recognition of the present insufficient fulfilment of the requirements and recommendations in many European countries have led the IAEA to organize in 2015 the Regional Meeting on Medical Physics in Europe, where major issues in medical physics in Europe were discussed. Most important outcomes of the meeting were the recommendations addressed to European member states and the survey on medical physics status in Europe conducted by the IAEA and European Federation of Organizations for Medical Physics. CONCLUSIONS: Published recommendations of IAEA Regional Meeting on Medical Physics in Europe shall be followed and enforced in all European states. Appropriate qualification framework including education, clinical specialization, certification and registration of medical physicists shall be established and international recommendation regarding staffing levels in the field of medical physics shall be fulfilled in particular. European states have clear legal and moral responsibility to effectively transpose Basic Safety Standards into national legislation in order to ensure high quality and safety in patient healthcare.

Automated fluence map optimization based on fuzzy inference systems.

PURPOSE: The planning of an intensity modulated radiation therapy treatment requires the optimization of the fluence intensities. The fluence map optimization (FMO) is many times based on a nonlinear continuous programming problem, being necessary for the planner to define a priori weights and/or lower bounds that are iteratively changed within a trial-and-error procedure until an acceptable plan is reached. In this work, the authors describe an alternative approach for FMO that releases the human planner from trial-and-error procedures, contributing for the automation of the planning process. METHODS: The FMO is represented by a voxel-based convex penalty continuous nonlinear model. This model makes use of both weights and lower/upper bounds to guide the optimization process toward interesting solutions that are able to satisfy all the constraints defined for the treatment. All the model's parameters are iteratively changed by resorting to a fuzzy inference system. This system analyzes how far the current solution is from a desirable solution, changing in a completely automated way both weights and lower/upper bounds. The fuzzy inference system is based on fuzzy reasoning that enables the use of common-sense rules within an iterative optimization process. The method is built in two stages: in a first stage, an admissible solution is calculated, trying to guarantee that all the treatment planning constraints are being satisfied. In this first stage, the algorithm tries to improve as much as possible the irradiation of the planning target volumes. In a second stage, the algorithm tries to improve organ sparing, without jeopardizing tumor coverage. RESULTS: The proposed methodology was applied to ten head-and-neck cancer cases already treated in the Portuguese Oncology Institute of Coimbra (IPOCFG) and signalized as complex cases. IMRT treatment was considered, with 7, 9, and 11 equidistant beam angles. It was possible to obtain admissible solutions for all the patients considered and with no human planner intervention. The results obtained were compared with the optimized solution using a similar optimization model but with human planner intervention. For the vast majority of cases, it was possible to improve organ sparing and at the same time to assure better tumor coverage. CONCLUSIONS: Embedding a fuzzy inference system into FMO allows human planner reasoning to be used in the guidance of the optimization process toward interesting regions in a truly automated way. The proposed methodology is capable of calculating high quality plans within reasonable computational times and can be an important contribution toward fully automated radiation therapy treatment planning.

Simulated annealing applied to IMRT beam angle optimization: A computational study.

Electing irradiation directions to use in IMRT treatments is one of the first decisions to make in treatment planning. Beam angle optimization (BAO) is a difficult problem to tackle from the mathematical optimization point of view. It is highly non-convex, and optimization approaches based on gradient descent methods will probably get trapped in one of the many local minima. Simulated Annealing (SA) is a local search probabilistic procedure that is known to be able to deal with multimodal problems. SA for BAO was retrospectively applied to ten clinical examples of treated cases of head-and neck tumors signalized as complex cases where proper target coverage and organ sparing proved difficult to achieve. The number of directions to use was considered fixed and equal to 5 or 7. It is shown that SA can lead to solutions that significantly improve organ sparing, even considering a reduced number of angles, without jeopardizing tumor coverage.

Analysis of fractionation correction methodologies for multiple phase treatment plans in radiation therapy.

PURPOSE: Radiation therapy is often delivered by multiple sequential treatment plans. For an accurate radiobiological evaluation of the overall treatment, fractionation corrections to each dose distribution must be applied before summing the three-dimensional dose matrix of each plan since the simpler approach of performing the fractionation correction to the total dose-volume histograms, obtained by the arithmetical sum of the different plans, becomes inaccurate for more heterogeneous dose patterns. In this study, the differences between these two fractionation correction methods, named here as exact (corrected before) and approximate (after summation), respectively, are assessed for different cancer types. METHODS: Prostate, breast, and head and neck (HN) tumor patients were selected to quantify the differences between two fractionation correction methods (the exact vs the approximate). For each cancer type, two different treatment plans were developed using uniform (CRT) and intensity modulated beams (IMRT), respectively. The responses of the target and normal tissue were calculated using the Poisson linear-quadratic-time model and the relative seriality model, respectively. All treatments were radiobiologically evaluated and compared using the complication-free tumor control probability (P+), the biologically effective uniform dose (D) together with common dosimetric criteria. RESULTS: For the prostate cancer patient, an underestimation of around 14%-15% in P+ was obtained when the fractionation correction was applied after summation compared to the exact approach due to significant biological and dosimetric variations obtained between the two fractionation correction methods in the involved lymph nodes. For the breast cancer patient, an underestimation of around 3%-4% in the maximum dose in the heart was obtained. Despite the dosimetric differences in this organ, no significant variations were obtained in treatment outcome. For the HN tumor patient, an underestimation of about 5% in treatment outcome was obtained for the CRT plan as a result of an underestimation of the planning target volume control probability by about 10%. An underestimation of about 6% in the complication probability of the right parotid was also obtained. For all the other organs at risk, dosimetric differences of up to 4% were obtained but with no significant impact in the expected clinical outcome. However, for the IMRT plan, an overestimation in P+ of 4.3% was obtained mainly due to an underestimation of the complication probability of the left and right parotids (2.9% and 5.8%, respectively). CONCLUSIONS: The use of the exact fractionation correction method, which is applying fractionation correction on the separate dose distributions of a multiple phase treatment before their summation was found to have a significant expected clinical impact. For regions of interest that are irradiated with very heterogeneous dose distributions and significantly different doses per fraction in the different treatment phases, the exact fractionation correction method needs to be applied since a significant underestimation of the true patient outcome can be introduced otherwise.

Response-probability volume histograms and iso-probability of response charts in treatment plan evaluation.

PURPOSE: This study aims at demonstrating a new method for treatment plan evaluation and comparison based on the radiobiological response of individual voxels. This is performed by applying them on three different cancer types and treatment plans of different conformalities. Furthermore, their usefulness is examined in conjunction with traditionally applied radiobiological and dosimetric treatment plan evaluation criteria. METHODS: Three different cancer types (head and neck, breast and prostate) were selected to quantify the benefits of the proposed treatment plan evaluation method. In each case, conventional conformal radiotherapy (CRT) and intensity modulated radiotherapy (IMRT) treatment configurations were planned. Iso-probability of response charts was produced by calculating the response probability in every voxel using the linear-quadratic-Poisson model and the dose-response parameters of the corresponding structure to which this voxel belongs. The overall probabilities of target and normal tissue responses were calculated using the Poisson and the relative seriality models, respectively. The 3D dose distribution converted to a 2 Gy fractionation, D2(GY) and iso-BED distributions are also shown and compared with the proposed methodology. Response-probability volume histograms (RVH) were derived and compared with common dose volume histograms (DVH). The different dose distributions were also compared using the complication-free tumor control probability, P+, the biologically effective uniform dose, D, and common dosimetric criteria. RESULTS: 3D Iso-probability of response distributions is very useful for plan evaluation since their visual information focuses on the doses that are likely to have a larger clinical effect in that particular organ. The graphical display becomes independent of the prescription dose highlighting the local radiation therapy effect in each voxel without the loss of important spatial information. For example, due to the exponential nature of the Poisson distribution, cold spots in the target volumes or hot spots in the normal tissues are much easier to be identified. Response-volume histograms, as DVH, can also be derived and used for plan comparison. RVH are advantageous since by incorporating the radiobiological properties of each voxel they summarize the 3D distribution into 2D without the loss of relevant information. Thus, more clinically relevant radiobiological objectives and constraints could be defined and used in treatment planning optimization. These measures become increasingly important when dose distributions need to be designed according to the microscopic biological properties of tumor and normal tissues. CONCLUSIONS: The proposed methods do not aim to replace quantifiers like the probabilities of total tissue response, which ultimately are the quantities of interest to evaluate treatment success. However, iso-probability of response charts and response-probability volume histograms illustrates more clearly the difference in effectiveness between different treatment plans than the information provided by alternative dosimetric data. The use of 3D iso-probability of response distributions could serve as a good descriptor of the effectiveness of a dose distribution indicating primarily the regions in a tissue that dominate its response.

Commissioning of brachytherapy module of Oncentra MasterPlan treatment planning system.

PURPOSE: To describe the tests that have been performed in order to commission the Brachytherapy module, version 3.2, service pack 3.0, of the Oncentra MasterPlan treatment plan system (OB), from Nucletron. The results were benchmarked against those obtained with the Plato system, v 14.3.7, also from Nucletron, used in the clinical routine. MATERIAL AND METHODS: Commissioning was performed taking Plato, v 14.3.7 as the standard TPS used in clinical practice. Commissioning tests were divided into two categories: i) simple geometric catheter configurations and ii) clinical intracavitary gynaecological and interstitial breast implants. For category i), also manual independent point dose calculations following the TG-43 dosimetry protocol were included in the comparisons. For category ii), the treatment plan comparisons were based on the calculated dose distributions in CT axial plans and on the dose-volume quality indexes following the local clinical acceptance criteria. Similar optimization tools were used in both systems. IPSA in OB was tested for planning interstitial breast implants and compared with the optimization process used with Plato in the clinical routine. RESULTS AND CONCLUSIONS: Regarding the point dose calculations, the agreement was better than 1%. For the clinical compared cases and using the same optimization tools all plans ended in similar dose distributions and very close quality indexes. Nevertheless, for endovaginal treatment plans, a slightly different value for the DTGR parameter had to be used (0.452, instead of 0.5 used as default in PLATO) in order to achieve the same dwell time for each activated source dwell position. Concerning interstitial breast implants, the IPSA algorithm constitutes a fast tool to reach a close clinical acceptable solution but Graphical Optimization is still needed. Considering these results the OB module was accepted for clinical use despite some persisting limitations, such as no consideration of heterogeneities or options for applicator shielding.

Uso diário e semanal de sulfato ferroso no tratamento de anemia em mulheres no período reprodutivo / Use of daily and weekly ferrous sulfate to treat anemic childbearing-age women

Mediante um ensaio terapêutico randomizado e cego em 193 mulheres (15-45 anos de idade) anêmicas (Hb<12mg/dl) e "menstruantes", comparou-se a açäo e a adesäo ao tratamento com sulfato ferroso (60 mg de Fe elementar), administrado em doses diárias e semanais, em uma comunidade de baixa renda do Recife-PE. Após 12 semanas de tratamento, 150 mulheres chegaram ao final do ensaio, sendo 79 do esquema semanal e 71 do diário. As médias de Hb antes do tratamento foram, respectivamente, 10,52 g/dl (DP = 1,13) e 10,72 g/dl (DP =0,92) para o esquema alternativo e convencional. Após a intervençäo, as médias de Hb alcançaram 11,83 g/dl (DP =0,97) no esquema semanal e 11,62 g/dl (DP =1,39) no diário. Näo houve significância estatística (p= 0,22) entre as diferenças de médias nos dois esquemas terapêuticos, embora o percentual de cura (48,1 por cento) tenha sido maior no tratamento semanal, quando comparado ao diário (36,6 por cento). Conclui-se que o esquema de tratamento semanal teve a mesma eficácia do diário. A aceitaçäo ao tratamento no primeiro mês foi melhor no esquema semanal, näo havendo, entretanto, diferenças nos dois meses subseqüentes.

Estudo prospectivo e randomizado do uso de antimicrobiano profilático em cesarianas / Prospective and randomized trial of the use of antibiotics as prophylatic in cesarean section

Este estudo prospectivo e randomizado foi realizado com o objetivo de comparar as taxas de infecçoes hospitalares de dois grupos, do total de 200 pacientes, submetidos à cesariana. Cem pacientes usaram cefalotina (IBA) 1g. EV após a ligadura do cordao umbilical e 100 pacientes nao usaram o antimicrobiano.Foi estabelecido um protocolo visando a correlaçao das infecçoes hospitalares com diversos fatores de risco para infecçoes puerperais. Submetido ao tratamento estatístico, o estudo nao demonstrou diferença significativa entre a incidência de infecçoes nos dois grupos, exceto no estudo dos fatores sociais, onde o grupo pertencente às classes DE, nao submetido a antibiótico-profilaxia, apresentou uma incidência de infecçoes hospitalares mais elevada do que o grupo das camadas sociais ABC.A taxa global de infecçoes hospitalares foi de 7,0 por cento. Sendo 4 por cento no grupo que usou antimicrobiano e 10 por cento no grupo que nao usou. A análise destes dados demonstrou que nao estamos autorizados a recomendar ou nao o uso de antimicrobianos (Cefalotina) profilático nas cesarianas.

Problemas de um serviço de enfermagem: experiência na estruturaçäo de um programa de trabalho / Problems of a nursing service: experience in the structuring of a work program

O trabalho foi desenvolvido visando identificar problemas e analisar sugestöes que servissem de subsídios para estruturaçäo de um programa de atividades centrado nas necessidades sentidas pelos enfermeiros, estabelecendo estratégias e açöes que possibilitem mudanças na prática da Enfermagem no hospital em estudo