Purpose
Irregular breathing may compromise the treated volume for free‐breathing lung cancer patients during radiotherapy. We try to find a measure based on a breathing amplitude surrogate that can ...be used to select the patients who need further investigation of tumor motion to ensure that the internal target volume (ITV) provides reliant coverage of the tumor.
Material and methods
Fourteen patients were scanned with four‐dimensional computed tomography (4DCT) during free‐breathing. The breathing motion was detected by a pneumatic bellows device used as a breathing amplitude surrogate. In addition to the 4DCT, a breath‐hold (BH) scan and three cine CT imaging sessions were acquired. The cine images were taken at randomized intervals at a rate of 12 per minute for 8 minutes to allow tumor motion determination during a typical hypo‐fractionated treatment scenario. A clinical target volume (CTV) was segmented in the BH CT and propagated over all cine images and 4DCT bins. The center‐of‐volume of the translated CTV (CTVCOV) in the ten 4DCT bins were interconnected to define the 4DCT determined tumor trajectory (4DCT‐TT). The volume of CTV inside ITV for all cine CTs was calculated and reported at the 10th percentile (VCTV10%). The deviations between CTVCOV in the cine CTs and the 4DCT‐TT were calculated and reported at its 90th percentile (d90%). The standard deviation of the bellows amplitude peaks (SDP) and the ratio between large and normal inspirations, κrel, were tested as surrogates for VCTV10% and d90%.
Results
The values of d90% ranged from 0.6 to 5.2 mm with a mean of 2.2 mm. The values of VCTV10% ranged from 59–93% with a mean of 78 %. The SDP had a moderate correlation (r = 0.87) to d90%. Less correlation was seen between SDP and VCTV10% (r = 0.77), κrel and d90% (r = 0.75) and finally κrel and VCTV10% (r = 0.75).
Conclusions
The ITV coverage had a large variation for some patients. SDP seems to be a feasible surrogate measure to select patients that needs further tumor motion determination.
To assess the relationship between radiation doses to the coronary arteries (CAs) and location of a coronary stenosis that required intervention after three-dimensional conformal radiotherapy (3DCRT) ...for breast cancer (BC).
The study population consisted of 182 women treated for BC in Sweden between 1992 and 2012. All women received 3DCRT and subsequently underwent coronary angiography due to a suspected coronary event. CA segments were delineated in the patient's original planning-CT and radiation doses were recalculated based on the dose distribution of the original radiotherapy (RT) plan. The location of the CA stenosis that required intervention was identified from the Swedish Coronary Angiography and Angioplasty Registry (SCAAR). Logistic regression analysis was used to assess the relationship between CA radiation doses and risk of a later coronary intervention at this specific location.
The odds ratio (OR) varied by radiation dose to the mid left anterior descending artery (LAD) (p = 0.005). Women receiving mean doses of 1-5 Gray (Gy) to the mid LAD had an adjusted OR of 0.90 (95% CI 0.47-1.74) for a later coronary intervention compared to women receiving mean doses of 0-1 Gy to the mid LAD. In women receiving mean doses of 5-20 Gy to the mid LAD, an adjusted OR of 1.24 (95% CI 0.52-2.95) was observed, which increased to an OR of 5.23 (95% CI 2.01-13.6) for mean doses over 20 Gy, when compared to women receiving mean doses of 0-1 Gy to the mid LAD.
In women receiving conventional 3DCRT for BC between 1992 and 2012, radiation doses to the LAD remained high and were associated with an increased requirement of coronary intervention in mid LAD. The results support that the LAD radiation dose should be considered in RT treatment planning and that the dose should be kept as low as possible. Minimising the dose to LAD is expected to diminish the risk of later radiation-induced stenosis.
Patient breathing during lung cancer radiotherapy reduces the ability to keep a sharp dose gradient between tumor and normal tissues. To mitigate detrimental effects, accurate information about the ...tumor position is required. In this work, we evaluate the errors in modeled tumor positions over several fractions of a simple tumor motion model driven by a surface surrogate measure and its time derivative. The model is tested with respect to four different surface surrogates and a varying number of surrogate and image acquisitions used for model training. Fourteen patients were imaged 100 times with cine CT, at three sessions mimicking a planning session followed by two treatment fractions. Patient body contours were concurrently detected by a body surface laser scanning system BSLS from which four surface surrogates were extracted; thoracic point TP, abdominal point AP, the radial distance mean RDM, and a surface derived volume SDV. The motion model was trained on session 1 and evaluated on sessions 2 and 3 by comparing modeled tumor positions with measured positions from the cine images. The number of concurrent surrogate and image acquisitions used in the training set was varied, and its impact on the final result was evaluated. The use of AP as a surface surrogate yielded the smallest error in modeled tumor positions. The mean deviation between modeled and measured tumor positions was 1.9 mm. The corresponding deviations for using the other surrogates were 2.0 mm (RDM), 2.8 mm (SDV), and 3.0 mm (TP). To produce a motion model that accurately models the tumor position over several fractions requires at least 10 simultaneous surrogate and image acquisitions over 1–2 minutes.
Current knowledge on material-related aspects of asphalt recycling with focus on findings from fundamental studies is summarized. By way of introduction, a general description of different types of ...asphalt recycling methods is given, after which a more detailed compilation of material-related knowledge is presented. Special attention is given to the binder rejuvenation process at asphalt recycling, that is the restoration of reclaimed binder properties. Studies concerning properties of recycled mixtures are also summarized.
Children with brain tumors are at high risk of neurocognitive decline after radiotherapy (RT). However, there is a lack of studies on how RT doses to organs at risk (OARs) impacts neurocognition. The ...aim of this study was to examine dose-risk relationships for mean RT dose to different brain structures important for neurocognitive networks. We explored previously established OARs and potentially new OARs.
A sample of 44 pediatric brain tumor survivors who had received proton and/or photon RT were included. Correlations between mean RT doses to OARs and IQ were analyzed. Previously established OARs were cochleae, optic chiasm, optic nerve, pituitary gland, hypothalamus, hippocampus and pons. Potential new OARs for RT-induced neurocognitive decline were cerebellum, vermis and thalamus.
Mean RT dose to different OARs correlated with several IQ subtests. Higher mean RT dose to cochleae, optic nerve, cerebellum, vermis and pons was correlated with lower performance on particularly full-scale IQ (FIQ), Perceptual Reasoning (PRI), Working Memory (WMI) and Processing Speed Index (PSI). Higher mean RT dose to hippocampus correlated with lower performance on processing speed and working memory. For those receiving whole brain RT (WBRT), higher mean RT dose to the pituitary gland correlated with lower performance on working memory.
A high dose-risk correlation was found between IQ subtests and mean RT dose in established and potential new OARs. Thus, in the lack of validated dose constraints for vulnerable brain structures, a parsimonious approach in RT planning should be considered to preserve neurocognitive networks.
Diffusion is considered important in the process of mixing old and new binders during asphalt recycling. The degree of mixing is presumed to greatly influence the final properties of recycled asphalt ...concrete. Previously, studies have been undertaken to investigate diffusion using FTIR-ATR (Fourier Transform Infrared Spectroscopy using Attenuated Total Reflectance). A need was identified to verify, if the rates of diffusion detected using FTIR-ATR were accompanied by changes in rheological properties. In this paper, a dynamic shear rheometer (DSR) with parallel plates is used for monitoring diffusion. Diffusion coefficients obtained at 60, 80 and 100 °C from tests of a soft bitumen (rejuvenator) diffusing into a stiff one are presented. The diffusion coefficients determined are compared with the corresponding diffusion coefficients obtained using FTIR-ATR. The comparison shows that the rates of diffusion detected by the DSR are of the same magnitude, but somewhat higher than the ones detected by FTIR-ATR.
Proton beam therapy offers potential clinical advantages compared with conventional radiation therapy for many cancer patients. The benefits are mainly a result of a more favourable dose ...distribution. The treatment cost with proton radiation is higher than for conventional radiation, mainly due to the large investment cost of building a proton therapy facility. It is therefore important to evaluate whether the medical benefits of proton therapy are large enough to justify the higher treatment costs, compared with conventional radiation therapy.
The cost-effectiveness of proton therapy in the treatment of 55-year old women with left-sided breast cancer was assessed. A Markov cohort simulation model was used to simulate the life of patients diagnosed with breast cancers and treated with radiation. Cost and quality adjusted life years (QALYs) were the primary outcome measures.
The study found a cost per QALY gained of €67,000 for the base case analysis of an average breast cancer patient. The cost per QALY gained would, however, be considerably lower if a population with high-risk of developing cardiac disease was treated. Sensitivity analyses showed that the results were stable and that the risk of cardiac disease was the most important parameter.
The results indicate that proton therapy for breast cancer can be cost-effective if appropriate risk groups are chosen as targets for the therapy.
Although variable confining pressure (VCP) triaxial tests are generally preferred to constant confining pressure (CCP) triaxial tests due to the more realistic stress application, VCP tests have ...never been utilized when investigating freezethaw effects on unbound road materials. In this study, three soils were investigated for resilient behavior during freezing and thawing utilizing both VCP and CCP triaxial testing. The soils were tested at selected temperatures between +20 and 10°C during one full freezethaw cycle. The results were analyzed in terms of the traditionally used resilient modulus and Poisson's ratio, as well as volumetric and shear components, and indicate a significant difference in moduli computed from CCP and VCP data. However, resilient moduli display compatible values when interpreted in terms of mean values of deviator stress and mean normal stress. With regard to freezevthaw effects on resilient moduli, the results are inconsistent with previous findings. However, this can be explained by the different test conditions applied.Key words: freezethaw, triaxial tests, unbound pavement materials, subgrade soils, resilient modulus.
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