On the use of radiobiological-based optimization functions in radiotherapy treatment planning for prostate and head and neck cases on Monaco and Eclipse TPS / Sobre el uso de funciones de costo basadas en radiobiología en la planeación de tratamientos de radioterapia para casos de próstata y cabeza y cuello en los TPS Monaco y Eclipse

INTRODUCTION Radiobiological-based optimization functions for radiotherapy treatment planning involve dose-volume effects that could allow greater versatility when shaping dose distributions and DVHs than traditional dose volume (DV) criteria. Two of the most commercially available TPS (Monaco and Eclipse) already offer biological-based optimization functions, but they are not routinely used by most planners in clinical practice. Insight into the benefits of using EUD, TCP/NTCP-based cost functions in Monaco and Eclipse TPS was gained by comparing biological-based optimizations and physical-based optimizations for prostate and head and neck cases. METHODS Three prostate and three H&N cases were retrospectively optimized in Monaco and Eclipse TPS, using radiobiological-based cost functions vs DV-based cost functions. Plan comparison involved ICRU Report 83 parameters D95%, D50%, D2% and TCP for the PTV, and NTCP and RTOG tolerance doses for OARs. RESULTS Although there were differences between Monaco and Eclipse plans due to their dissimilar optimization and dose calculation algorithms as well as optimization functions, both TPS showed that radiobiological-based criteria allow versatile tailoring of the DVH with variation of only one parameter and at most two cost functions, in contrast to the use of three to four DV-based criteria to reach a similar result. CONCLUSION Despite the use of a small sample, optimization of three prostate and three head and neck cases allowed the exploration of optimization possibilities offered by two of the most commercially available TPS on two anatomically dissimilar regions. Radiobiological-based optimization efficiently drives dose distributions and DVH shaping for OARs without sacrifice of PTV coverage. Use of EUD-based cost functions should be encouraged in addition to DV cost functions to obtain the best possible plan in daily clinical practice

INTRODUCCION Las funciones de optimización basadas en radiobiología para la planificación del tratamiento de radioterapia implican efectos dosis volumen que podrían permitir una mayor versatilidad a la hora de dar forma a las distribuciones de dosis y DVH que los tradicionales criterios dosis-volumen (DV). Dos de los TPS más disponibles comercialmente (Mónaco y Eclipse) ya ofrecen productos de funciones de optimización de base biológica, pero la mayoría de los planificadores no las utilizan de forma rutinaria en la práctica clínica. El conocimiento de los beneficios del uso de las funciones de costos basadas en EUD, TCP/NTCP en Mónaco y Eclipse TPS se obtuvo comparando optimizaciones de base biológica y optimizaciones físicas para casos de próstata y cabeza y cuello. MÉTODOS Tres próstatas y tres casos de H&N en Mónaco y Eclipse TPS fueron optimizadas retrospectivamente usando funciones de costos basadas en radiobiología vs funciones de costos basadas en DV. La comparación de planes involucró los parámetros del Informe ICRU 83 D95%, D50%, D2% y TCP para el PTV, y dosis de tolerancia NTCP y RTOG para OAR. Resultados. Aunque hubo diferencias entre los planes Mónaco y Eclipse, debido a sus diferentes algoritmos de optimización y cálculo de dosis, así como funciones de optimización, ambos TPS demostraron que el criterio basado en radiobiología permiten una adaptación versátil del DVH con variación de un solo parámetro y como máximo dos funciones de costos, en contraste con el uso de tres o cuatro criterios basados en DV para alcanzar un resultado similar. CONCLUSIÓN A pesar del uso de una muestra pequeña, la optimización de tres casos de próstata y tres de cabeza y cuello permitió la exploración de las posibilidades de optimización que ofrecen dos de los TPS más disponibles comercialmente en dos regiones anatómicamente diferentes. La optimización basada en radiobiología impulsa de manera eficiente las distribuciones de dosis y la configuración de DVH para OAR sin sacrificar Cobertura de PTV. Se debe fomentar el uso de funciones de costos basadas en EUD además de las funciones de costos DV para obtener el mejor posible plan en la práctica clínica diaria

Proposals of models for new formulations of the current complication-free cure (P+) and uncomplicated tumor control probability (UTCP) concepts, and total normal tissue complication probability of late complications.

This study proposes phenomenological models for total normal tissue complication probability (TNTCP) and NTCP0. NTCP0 is a new acronym for reformulating the current complication-free cure (P+) and uncomplicated tumor control probability (UTCP) concepts, and TNTCP will reformulate the current NTCP involving multiple organs at risks. The current probabilistic concepts are incoherently formulated with mathematical operations of tumor control probability (TCP) and normal tissue complication probability (NTCP) that are associated with different stochastic processes and random variables. NTCP0 is equal to NTCP0 (normal tissue non-complication probability) that is calculated as the ratio of a number of patients of a population without late complications and a total of them. As a cumulative distribution function (CDF) of late complications, TNTCP = sum(NTCPi), where NTCPi is the NTCP of the ith late complication. TNTCP is also a new acronym, and the probabilistic complement of NTCP0, then NTCP0 = 100% - TNTCP. The NTCP0/TNTCP (D(d)) proposing models are based on the relationship between the NTCP0/TNTCP and total dose (D = n×d; where d = dose per fraction, and n = number of fractions). TNTCP(D) model will be correlated with LKB model (the normal CDF) that is an increasing function; and NTCP0(D) model with a decreasing function, which additionally will define clear limits of three possible regions for NTCP0: 0 and 100% deterministic, and a stochastic. These models are function D, which is widely used for characterizing radiation therapies.

The effect of slice thickness on target and organs at risk volumes, dosimetric coverage and radiobiological impact in IMRT planning.

PURPOSE: Dose-volume histogram (DVH) has become an important tool for evaluation of radiation outcome as reflected from many clinical protocols. While dosimetric accuracy in treatment planning system (TPS) is well quantified, the variability in volume estimation is uncertain due to reconstruction algorithm that is investigated in this study. In addition, the impact of dose distribution and tumor control probability (TCP) were also investigated with CT slice thickness for IMRT planning. MATERIALS AND METHODS: A water phantom containing various objects with accurately known volume ranging from 1 to 100 cm(3) was scanned with 1, 2, 3, 5, and 10 mm slice thickness. The CT data sets were sent to Eclipse TPS for contour delineation and volume estimation. The data were compared with known volume for the estimation of error in the volume of each structure. IMRT Plans were generated on phantom containing four objects with different slice thickness (1-5 mm) to calculate TCP. ICRU-83-recommended dose points such as D 2%, D 50%, D 98%, as well as homogeneity and conformity index were also calculated. RESULTS: The variability of volumes with CT slice thickness was significant especially for small volume structures. A maximum error of 92% was noticed for 1 cm(3) volume of object with 10 mm slice thickness, whereas it was ~19% for 1 mm slice thickness. For 2 and 3 cm(3) objects, the maximum error of 99% was noticed with 10 mm slice thickness and ~60% with 5 mm. The differences are smaller for larger volumes with a cutoff at about 20 cm(3). The calculated volume of the objects is a function of reconstruction algorithm and slice thickness. The PTV mean dose and TCP decreased with increasing slice thickness. Maximum variation of ~5% was noticed in mean dose and ~2% in TCP with change in slice thickness from 1 to 5 mm. The relative decrease in target volume receiving 95% of the prescribed dose is ~5% with change in slice thickness from 1 to 5 mm. The homogeneity index increases up to 163% and conformity index decreases by 4% between 1 and 5 mm slice thickness, producing highly inhomogeneous and least conformal treatment plan. CONCLUSIONS: Estimation of a volume is dependent on CT slice thickness and the contouring algorithm in a TPS. During commissioning of TPS and for all clinical protocols, evaluation of volume should be included to provide the limit of accuracy in DVH from TPS, especially for small objects. A smaller slice thickness provides superior dosimetry with improved TCP. Thus, the smallest possible slice thickness should be used for IMRT planning, especially when smaller structures are present.

Anidamiento en las comunidades de parásitos en peces intermareales de Chile central: ¿Qué tan influyente es la longitud corporal del hospedero?

a estructura de la comunidad de parásitos, determinada mediante análisis de anidamiento, varía considerablemente en función de la especie hospedera y el tamaño corporal de la misma. El patrón anidado es aquel en el que comunidades pobres en especies constituyen subunidades de comunidades de mayor riqueza, lo cual también se observa en las comunidades de parásitos. Existen grandes diferencias de riqueza y abundancia de parásitos en función del tamaño del hospedero. Por lo tanto, en este estudio determinamos, mediante análisis de anidamiento, si la estructura de la comunidad de parásitos de peces del intermareal, se relaciona con la longitud corporal de los hospederos y los descriptores parasitológicos. Se recolectaron 2 435 individuos de cinco especies de peces del intermareal rocoso de Chile central (32º02'-33º57' S y 70º30'- 70º30' W); Helcogrammoides chilensis, Scartichthys viridis, Auchenionchus microcirrhis, Gobiesox marmoratus y Sicyases sanguineus. Cada especimen fue revisado con respecto a sus parásitos y medido en su longitud total (LT). Las cinco especies muestreadas fueron clasificadas en función de la longitud corporal (LT) en tres rangos, cada uno de los cuales constituye una infracomunidad del estudio, y para la que se calculó el índice de anidamiento. Se emplearon los modelos NTCP (Nestedness Temperature Calculator Program) y NODF (Nestedness metric based on the Overlap and Decreasing Fill), utilizando la presencia/ ausencia de especies parásitas. También se empleó el modelo WNODF (Weighted - NODF) utilizando la abundancia de parásitos por especie. Así mismo, se calculó la riqueza total de especies, el promedio de riqueza, abundancia, diversidad y dominancia a nivel de la infracomunidad, para relacionarlos con los índices de anidamiento. Las infracomunidades de parásitos de la mayoría de las especies presentaron patrones de anidamiento, excepto en G. marmoratus y H. chilensis, en algunos de sus rangos de LT. No se encontró una relación directa entre el índice de anidamiento y la LT de los peces. Sin embargo, se observaron correlaciones directas de los índices de anidamiento con la riqueza promedio, abundancia y la diversidad infracomunitaria de parásitos, pero no con la riqueza total, que mostró una correlación inversa con la LT del hospedero. Además, se detectó anidamiento en la comunidad componente de parásitos en todas las especies de peces. Concluimos que las comunidades de parásitos de peces provenientes de la zona intermareal son estructuradas y predecibles, y se encuentran vagamente condicionadas por la LT de los hospederos y las características agregadas de los parásitos, especialmente a un nivel infracommunitario.

tructure and richness of parasite communities varies substantially among species and body sizes of hosts, which can be determined by analyzing the nestedness. The nestedness pattern is originated when depauperate communities are subsets of those found in communities with greater species richness, and has normally used to study parasite communities. Therefore, in this study we determined whether the structure of parasite communities of the intertidal fish, of central Chile, relates to host lengths and parasitological descriptors, by the use of nested subset analyses. We collected 2 435 individuals of five fish species from the intertidal rocky zone of central Chile (32º02'-33º57' S - 70º30'-70º30' W): Helcogrammoides chilensis, Scartichthys viridis, Auchenionchus microcirrhis, Gobiesox marmoratus, and Sicyases sanguineus; each specimen was analyzed for parasites and its total body length (LT) was measured. The total species richness, average richness, abundance, diversity, and dominance of parasites infracommunity (all parasites in a host specimen) were calculated. Each fish species was classified into three LT ranges, to calculate the indices of nestedness and average of these parasitological descriptors in each LT range. We used the models given in the NTCP (Nestedness Temperature Calculator Program) and NODF (Nestedness metric based on Overlap and Decreasing Fill), considering the presence or absence of parasite species; we also used WNODF (Weighted-NODF) model for parasite abundances. The average of parasitological descriptors and LT of each host species, as well as the indices of nestedness were also calculated and related one another, considering the infracommunity and component community levels. The parasite infracommunity of most fish species exhibited a nestedness pattern structure, with the exception of G. marmoratus and H. chilensis, in some of the LT ranges. No relationship between the nestedness indices and fish LT was found. Nevertheless, direct correlations were observed among nestedness indices, average of richness, abundance and diversity of parasite infracommunity, and an inverse correlation with the parasite total richness (per LT range). Moreover, the nestedness pattern was present in all host species. We concluded that the parasite communities of intertidal fish are structured and predictable, and determined only minimally by the host LTs and the aggregated characteristics of the parasites, particularly at the infracommunity level. Rev. Biol. Trop. 63 (4): 995-1005. Epub 2015 December 01.

On voxel-by-voxel accumulated dose for prostate radiation therapy using deformable image registration.

Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 TM (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values.