Doses to internal organs for various breast radiation techniques - implications on the risk of secondary cancers and cardiomyopathy

<p>Abstract</p> <p>Background</p> <p>Breast cancers are more frequently diagnosed at an early stage and currently have improved long term outcomes. Late normal tissue complications induced by adjuvant radiotherapy like secondary cancers or cardiomyopathy must now be avoided at all cost. Several new breast radiotherapy techniques have been developed and this work aims at comparing the scatter doses of internal organs for those techniques.</p> <p>Methods</p> <p>A CT-scan of a typical early stage left breast cancer patient was used to describe a realistic anthropomorphic phantom in the MCNP Monte Carlo code. Dose tally detectors were placed in breasts, the heart, the ipsilateral lung, and the spleen. Five irradiation techniques were simulated: whole breast radiotherapy 50 Gy in 25 fractions using physical wedge or breast IMRT, 3D-CRT partial breast radiotherapy 38.5 Gy in 10 fractions, HDR brachytherapy delivering 34 Gy in 10 treatments, or Permanent Breast ¹⁰³Pd Seed Implant delivering 90 Gy.</p> <p>Results</p> <p>For external beam radiotherapy the wedge compensation technique yielded the largest doses to internal organs like the spleen or the heart, respectively 2,300 mSv and 2.7 Gy. Smaller scatter dose are induced using breast IMRT, respectively 810 mSv and 1.1 Gy, or 3D-CRT partial breast irradiation, respectively 130 mSv and 0.7 Gy. Dose to the lung is also smaller for IMRT and 3D-CRT compared to the wedge technique. For multicatheter HDR brachytherapy a large dose is delivered to the heart, 3.6 Gy, the spleen receives 1,171 mSv and the lung receives 2,471 mSv. These values are 44% higher in case of a balloon catheter. In contrast, breast seeds implant is associated with low dose to most internal organs.</p> <p>Conclusions</p> <p>The present data support the use of breast IMRT or virtual wedge technique instead of physical wedges for whole breast radiotherapy. Regarding partial breast irradiation techniques, low energy source brachytherapy and external beam 3D-CRT appear safer than ¹⁹²Ir HDR techniques.</p

On the use of HDR 60Co source with the MammoSite® radiation therapy system

This work summarizes Monte Carlo results in order to evaluate the potential of using HDR Co60 sources in accelerated partial breast irradiation (APBI) with the MammoSite® applicator. Simulations have been performed using the MCNP5 Monte Carlo Code, in simple geometries comprised of two concentric spheres; the internal consisting of selected concentrations, C, of a radiographic contrast solution in water (Omnipaque 300™) to simulate the MammoSite balloon and the external consisting of water to simulate surrounding tissue. The magnitude of the perturbation of delivered dose due to the radiographic contrast medium used in the MammoSite® applicator is calculated. At the very close vicinity of the balloon surface, a dose build-up region is observed, which leads to a dose overestimation by the treatment planning system (TPS) which depends on Omnipaque™ 300 solution concentration (and is in order of 2.3%, 3.0%, and 4.5%, respectively, at 1 mm away from the balloon - water interface, for C=10%, 15%, and 20%). However, dose overestimation by the TPS is minimal for points lying at the prescription distance (d=1 cm) or beyond, for all simulated concentrations and radii of MammoSite® balloon. An analytical estimation of the integral dose outside the CTV in the simple geometries simulated shows that dose to the breast for MammoSite® applications is expected to be comparable using HDR Co60 and Ir192 sources, and higher than that for Yb169. The higher enegies of Co60 sources result to approximately twice radiation protection requirements as compared to Ir169 sources. However, they allow for more accurate dosimetry calculation with currently used treatment planning algorithms for Co60 sources, compared to Ir169. © 2008 American Association of Physicists in Medicine

Developmental Language Disorder (DLD) and Autism Spectrum Disorder (ASD): similarities in pragmatic language abilities. A systematic review

Objective: Pragmatics can be defined as the appropriate use of language in social interactions. Children with Autism Spectrum Disorder (ASD) and children with Developmental Language Disorder (DLD) exhibit difficulties in pragmatic language (PL), but the nature and sources of these difficulties have not been fully investigated yet. The purpose of this paper is to critically review empirical literature on the PL of children with ASD as compared to that of children with DLD. Materials and methods: Thirteen studies that met established inclusion criteria were identified and reviewed. Results: Children with ASD and children with DLD demonstrated several similarities in PL. However, a lot of differences were observed and mainly children with ASD faced more profound difficulties than children with DLD, while PL may be a distinct marker between the two groups. Conclusion: The differences observed in the language profiles of ASD and DLD show that even if there is an overlap in some domains, the PL abilities of children of both clinical populations are likely to be controlled by different mechanisms and therefore these differences in PL may be considered as a distinguishable feature between the two populations. © The British Society of Developmental Disabilities 2022

A radiobiological investigation on dose and dose rate for permanent implant brachytherapy of breast using i 125 or P 103 d sources

Purpose: The present report addresses the question of what could be the appropriate dose and dose rate for 125I and 103Pd permanent seed implants for breast cancer as monotherapy for early stage breast cancer. This is addressed by employing a radiobiological methodology, which is based on the linear quadratic model, to identify a biologically effective dose (BED) to the prescription point of the brachytherapy implant, which would produce equivalent cell killing (or same cell survival) when compared to a specified external radiotherapy scheme. Methods: In the present analysis, the tumor and normal tissue BED ratios of brachytherapy and external radiotherapy are examined for different combinations of tumor proliferation constant (K), α/β ratios, initial dose rate (R0), and reference external radiotherapy scheme (50 or 60 Gy in 2 Gy per fraction). The results of the radiobiological analysis are compared against other reports and clinical protocols in order to examine possible opportunities of improvement. Results: The analysis indicates that physical doses of approximately 100-110 Gy delivered with an initial dose rate of around 0.05 Gyh-1 and 78-80 Gy delivered at 0.135 Gyh-1 for 125I and 103Pd permanent implants, respectively, are equivalent to 50 Gy external beam radiotherapy (EBRT) in 2 Gy per fraction. Similarly, for physical doses of approximately 115-127 Gy delivered with an initial dose rate of around 0.059 Gyh-1 and 92 Gy delivered at 0.157 Gyh-1 for 125I and 103Pd, respectively, are equivalent to 60 Gy EBRT in 2 Gy per fraction. It is shown that the initial dose rate required to produce isoeffective tumor response with 50 or 60 Gy EBRT in 2 Gy per fraction increases as the repopulation factor K increases, even though repopulation is also considered in EBRT. Also, the initial dose rate increases as the value of the α/β ratio decreases. The impact of the different α/β ratios on the ratio of the tumor BEDs is significantly large for both the 125I and 103Pd implants with the deviation between the α/β=10.0 Gy ratios and those using the 4.0 and 3.5 Gy values ranging between 18% and 22% in most of the cases. Conclusions: For the cases of 125I and 103Pd, the equivalent physical doses to 50 Gy EBRT in 2 Gy per fraction are associated with an overdosage of the involved normal tissue in the range of 4%-16% and an underdosage by 10%-15% for a BED for normal tissue, using an α/β value of 3.0 Gy (BEDNT,3 Gy) of 100 Gy. These values are lower by 10%-20% than the published value of 124 Gy for 125I and by about 13% when compared to the published isoeffective dose of 90 Gy for 103Pd. Similarly, the equivalent physical doses to 60 Gy EBRT in 2 Gy per fraction are associated with an overdosage of the involved normal tissue by 10%-20% and an underdosage by 4%-10% for BED NT,3 Gy of 110 Gy. © 2010 American Association of Physicists in Medicine